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Weatherstripping a Slider

Tango Mike

Well Known Member
I own an RV-6 tip-up (for sale) and an RV-7 slider. Experience with both puts me on the slider side of the "debate," but I didn't anticipate the difference in how the two canopy designs seal. There are no gaps with the tip-up and I've never had to add any weatherstripping.

I'm not a builder, but I've been told that sliders are harder to install, so part of the difference could be due to the fact that the slider isn't as well done as the tip-up. That said, looking at how the gap between the fuselage and the canopy varies during the open/close cycle appears to present a challenge in trying to seal the slider well.

I'm looking for information on how the experts have dealt with this and would appreciate any ideas/advice/suggestions.

Thanks,

Tosh
 
Hi Tosh...on our -6A slider, we'd use some pipe insulation stuffed between the skirts and the rail, during very cold mornings. We also installed some of the flap tape where the canopy lays on the aft fuselage. It stops the paint from getting scratched as well.

Best,
 
Velcro

Some people have glued felt or a similar fabric as weather-stripping on sliders. I glued the loop side of a length of Velcro to the aft portion of my slider to stop the paint wear and help seal this area. My thought being the loop side of Velcro is a soft surface against the paint but does not hold moisture like some fabrics may. By the way, I used headliner spray glue to attach it to the canopy skirt.
 
Tosh,

Sealing a slider can be a challenge, but I think I found a pretty good solution.

I noticed that the air tends to exit around the base of the slider skirt, usually near the pilot's left elbow or copilot's right elbow. If you have on a long-sleeve shirt, sometimes it tries to suck your sleeve out through the gap! This in turn promotes a lot of what most refer to as "tail pumping," which is just flow from the empennage area to the cockpit through the rear fuselage caused by the low pressure over the canopy and the high pressure (relatively) in the tail area. Obviously, this also increases the risk for carbon monoxide flowing from the engine to the tail and through the aft fuselage to the cabin. So if you can stop the air exiting under the canopy, you are also diminishing the tail pumping phenomena. I started experimenting with this a few years ago and came up with a pretty good solution. I think of it as a flapper valve: I glued a piece of flat rubber seal to the bottom of the canopy rail and then went up and flew it. I noticed that the suction pulls the strip of rubber tightly against the side of the canopy. I started with short strips just to see if it was going to work, and when it did, I went ahead and cut one long strip and glued it the entire length of the canopy rail. This really works well and will completely seal your canopy assuming you don't have leaks in other places. Here is the test strip:





And here is the completed seal:



Make sure you extend the seal beyond the end of the canopy rail such that the canopy will not snag it when you move it forward. Likewise in the front, be sure to cut it such that there is freedom of movement outboard to where it seals against the canopy skirt. The suction really pulls this seal tight against the canopy skirt and provides an excellent seal. You won't feel any suction pulling on your sleeve anymore!

I got the rubber seal material at McMaster-Carr and used CYA glue--a small bead along the bottom of the seal will hold it well. Mine's been on there a few years now and has not come loose. You will need to experiment a little in finding the right height for the seal, so plan on making a few test samples until you find the size that works best for you.

EDIT: I looked up the part number of the EPDM rubber seal on McMaster-Carr if anyone is interested it's p/n 8985K12, $5.37 for a 1/16" X 2" X 36" strip, durometer 50A.
 
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Tosh,

Sealing a slider can be a challenge, but I think I found a pretty good solution.

Can't see the pics right now at work, but this is great info, Pat. I scratched my head over the airflow from the back of the canopy for quite a while last winter - have really not thought about it since spring/summer rolled around. This post is timely since cold weather - especially at altitude - is right around the corner. As much as I like to pop my collar 80's style :D while flying in the winter, maybe this winter I won't have to.
 
What a great solution!

Appreciate each reply, thank you.

The flapper-valve seal is an ingenious solution because it automatically adjusts for the variable gap between the skirt and the rail. I love it.

That leaves the gaps between the fuselage and the skirt behind the rail stops and the rear edge of the canopy. Yesterday I tried a weatherstripping product that didn't work well because it's rubberized and won't let the skirt slide without rolling it up. As a temporary solution, I covered the exposed surface of the weatherstripping with UHMW tape. That works okay, but there's got to be a better way.

I like the loop Velcro idea, and wonder if the sticky kind would hold as well as the headliner spray glue?

I've also heard about using self-adhesive felt strips, but like the Velcro solution, you still have to deal with a variable gap. At the bottom rear edges of the skirt on my -7, it's pretty wide, narrowing to almost nothing toward the top and at the center rail.

A builder friend sealed the side of his -6A slider by adding a piece of wood of variable thickness to the canopy skirt to create a uniform gap. Then he added a strip of stick-on felt window seal that I think he got from a supplier of accessories for older cars.

I considered trying that, but the process of tapering the thickness of the wood and checking it seemed to be really labor intensive, and I'd prefer to find a more user-friendly solution.

One idea would be to use soft weatherstripping that will compress and add a strip of loop Velcro on top of it. Where the gap on the rear skirt tapers too much for the weatherstripping, transition to the Velcro strip only. That would seal and prevent scratching the fuselage at the same time.

I'm still pondering that problem, but in the meantime I'm going to get some rubber and glue and install a flapper-valve canopy seal. Again, that's a fantastic idea, Pat!

Tosh
 
Grumman canopy seal

I'm pretty sure that the 4-seat (at least) Grummans use a P seal at the rear of the canopy that had a nylon covering so it slides over the paint. I don't have my AA5 parts manual handy, but I remember giving a roll of it to a buddy when I sold my last Cheetah. Fletch air in Houston would be a good source.


Part no G204/5 here http://fletchair.com/catalog/section30.html
 
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It can be done very effectively

It gets a little frustrating when you go trouble of explaining with photographs and word descriptions time after time how this has been done and how well it works but it seems that no one really gets it.

Bob Axsom
 
It gets a little frustrating when you go trouble of explaining with photographs and word descriptions time after time how this has been done and how well it works but it seems that no one really gets it.

Bob Axsom

Hey Bob, did you do this and show pics of it in the past? If so, would like to see your solution (never saw it if you did).

Since I feel like the caveman reinventing the wheel (was trying...unsuccessfully...to solve this leak before the Reno races, but kept rolling up weatherstripping...as was described earlier...or tearing felt) this thread is a find!

I have loop velcro on the aft portion of my slider, but the gap at the roller opening needs filling, and the side gaps definitely pull windbreaker sleeves through the opening. I experience a great deal of "tail air pumping", as evidenced by smoke filling the cockpit during show passes with smoke on. CO has not been indicated by indicator patches...perhaps the air moves enough to keep concentrations from building, or CO is heavier than show smoke, but its a good thing to watch out for! Would like to seal the canopy to keep the smoke from moving forward, and am hoping it may be a speed mod as well! ;)

Pat, just to clarify a couple things (thanks in advance):

- I get the part about extending the seal aft, for no snags. On the front, do you mean to make sure the upper forward corner doesn't snag on the forward canopy and leave a gap?

- What is CYA glue...that acronym is unfamiliar (well, at least in a glue context ;))

- On height experimentation, it looks like you ended up at about 3/4" (since the rail is 1" high. I can see shorter being less effective, but did you find higher was also ineffective? Figure I'll start with a direct imitation (you know what they say about flattery, eh!) :)

Thanks for the gouge...looks like a good solution!

(And Ax, what's on your rail? ;))

Cheers,
Bob

Tosh,

Sealing a slider can be a challenge, but I think I found a pretty good solution.

I noticed that the air tends to exit around the base of the slider skirt, usually near the pilot's left elbow or copilot's right elbow. If you have on a long-sleeve shirt, sometimes it tries to suck your sleeve out through the gap! This in turn promotes a lot of what most refer to as "tail pumping," which is just flow from the empennage area to the cockpit through the rear fuselage caused by the low pressure over the canopy and the high pressure (relatively) in the tail area. Obviously, this also increases the risk for carbon monoxide flowing from the engine to the tail and through the aft fuselage to the cabin. So if you can stop the air exiting under the canopy, you are also diminishing the tail pumping phenomena. I started experimenting with this a few years ago and came up with a pretty good solution. I think of it as a flapper valve: I glued a piece of flat rubber seal to the bottom of the canopy rail and then went up and flew it. I noticed that the suction pulls the strip of rubber tightly against the side of the canopy. I started with short strips just to see if it was going to work, and when it did, I went ahead and cut one long strip and glued it the entire length of the canopy rail. This really works well and will completely seal your canopy assuming you don't have leaks in other places. Here is the test strip:

Make sure you extend the seal beyond the end of the canopy rail such that the canopy will not snag it when you move it forward. Likewise in the front, be sure to cut it such that there is freedom of movement outboard to where it seals against the canopy skirt. The suction really pulls this seal tight against the canopy skirt and provides an excellent seal. You won't feel any suction pulling on your sleeve anymore!

I got the rubber seal material at McMaster-Carr and used CYA glue--a small bead along the bottom of the seal will hold it well. Mine's been on there a few years now and has not come loose. You will need to experiment a little in finding the right height for the seal, so plan on making a few test samples until you find the size that works best for you.

EDIT: I looked up the part number of the EPDM rubber seal on McMaster-Carr if anyone is interested it's p/n 8985K12, $5.37 for a 1/16" X 2" X 36" strip.
 
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Yes Bob I have posted my solution here in the VAF forum

Unrelated link removed - Bob Axsom

It took many years for Jeanine and I to build our RV-6A and I learned very early to think ahead and not limit myself to common tools and solutions if I could not see the a clear path to a precise and correct result. I carefully viewed the George and Becki Orndorff's VHS tape (great format for watching stopping and continuing where you left off later) as we built the plane and I collected problem solution facts where I found them (no VAF forum).

I found two interesting ideas that contributed to the solution of the canopy seal problem from others:

The Orndorff video - George pointed out that he welded steel tabs to the canopy frame at the bottom to support the side skirts. Welding is not in my skill set but the idea appeared to have merit. I made supports out of aluminum and pop riveted them to the frame and flush riveted them to the side skirt with standard flush rivets. This provided support to the side skirts but obviously would not provide a seal.

Tracy Saylor - I read somewhere that he made a mobile plug to close the area around the track in the rear center of the canopy. This seemed like a good idea. I made a little "dog house" out of 0.016 aluminum sheet to provide a closure shell and riveted it to the two rear skirts where they meet at the back. I made a plug out of several layers of balsa wood to fit inside the shell and conform to the slider rail. I cut a shallow recess across the plug and down it's sides and glued in a small white "P" strip (from aircraft spruce) to form a seal when canopy is closed. The plastic slider block on the canopy frame pushes the plug back when the canopy is opened and I used nylon electrical wire bundle lacing tape (flat string bought from aircraft spruce) as a means to pull the plug into the closed position. I looped the string over the bolt in the rear of the canopy frame as the anchor point (very easy to rig with the canopy off the airplane upside down on a work bench). I needed a stable and strong pull attach on the plug and after several not quite right methods I found that I could drive two thin stainless steel safety wire pieces (0.021 I think) back through the plug left and right of center then make a "U" on the back side and pull the bent back ends securely into the back side of the plug and coated it with glue for good measure. I formed string attachment loops in the two wires for the pull string on the front side of the plug. Initially I found that the loose string would wear out after a time from random contact with the rail. After replacing it a couple of times I installed clear plastic sleeving of the type used on electrical wire terminations {not thermofit) on the pull strings and never replaced a string again (a pain because the canopy has to be removed to rig the canopy/string/plug interface).

At this point only the center slider rail opening was sealed.

The forward seal was easy. The white "P" strip installed at the interface between the roll bar and the windshield fiberglass extension (the fiberglass that extends back over the canopy leading edge) provided the compressible seal and aluminum tape over the leading edge of the canopy provided a smooth mating surface to the fiberglass and the "P" strip.

Now I had the rest of the canopy perimeter to seal.

There are no parallel surfaces between the canopy and the fuselage that exist for the full range of travel with no interference. I studied this intently for a long time. Then I observed that the canopy travel is always parallel with the canopy side rails that have smooth sides and that I should be able to create a parallel surface on the inside of the canopy skirt above the bottom of the skirt to avoid the interference with the fuselage canopy deck/longeron/skin as the canopy pivots down during its rearward travel. I needed the exact shape of the canopy deck that extended beyond the maximum outward extension of the canopy side rail extrusions (they are not flat) to enable me to make conforming ribs for the side skirts. I marked off the canopy deck with butt lines (perpendicular to the centerline of the aircraft) every 1/2" on both sides of the fuselage. Then I made up a table for each side with a space for every butt line starting with 1 for the first line at the front. Then I took a simple square and set it flat on the canopy deck at each butt line measured and recorded the dimension and moved back to the next butt line and repeated until complete. Then I took file folders and assembled them with tape to form a unit with sufficient length and a straight edge for making the two patterns (left and right). I marked off the edge with at 1/2" intervals and plotted the points from the tables and connected the dots using a french curve. I bought 3/16" thick bar stock from Aircraft Spruce of sufficient width to include the widest dimension of the expose canopy deck. Then I taped the patterns to the bar stock and traced the pattern onto the aluminum with a sharpie. I did not have a bandsaw at that time so I used my hack saw to cut out the ribs in sections limited by the depth of the hack saw. Then I used files to shape the rough surface to a nicely conforming fit with the canopy skirt and provide a small interference avoiding gap for the slider side rail. Next I needed to know the height above the canopy deck of the maximum outward extension of the side rail extrusion curve (as I recall it was around 1/2"). I marked a line along the bottom of the canopy skirts and marked my desired rivet intervals and drilled the #40 rivet holes in the skirts only. Then I marked a longitudinal centerline on the curved surface of the ribs and clamped them to the inside of the canopy skirts so that the centerline aligned with every hole in the mating skirt and marked the desired rivet location on the exposed ribs. I used a drill press to precisely drill the rivet holes in the ribs. I countersunk all of the holes on both sides of both ribs to facilitate double flush riveting and I deburred and dimpled all of the rivet holes in the canopy side skirts. Then I used a hand squeezer to rivet the ribs to the skirts. to form the seal I bought a sheet of flat black rubber and cut out slightly over sized seals using the rib patterns from the aluminum ribs and glued them to the bottom of the aluminum ribs with 3M yellow Weather strip adhesive. The skirts are absolutely rigid and do not suck out in flight and the rubber seals against the outer slider rails.

That leaves everything aft of the outer slide rails still to be dealt with. In the RV-6 slider canopy design Van's extend the aft skirts down below the fuselage side skin to close the opening aft of the outer side rails - That was not acceptable to me. I decided I could cover the opening and provide a sealing surface above the fuselage side skin by riveting 1/16" aluminum angle to the top side of the longeron with the outboard flange extending up without extending the end of the rear skirts below the bottom of the side skirts. So I did that.

Finally for the rear bottom of the side skirts and the aft canopy skirts I used soft white "P" strip. I progressively trimmed the rear skirts as demonstrated by George Orndorff to get a perfect fit of the rear canopy skirts. Then I determined the distance of set back from the edge of the skirts need to seal the skirts with "P" strip without deflecting them away from the fuselage skin and installed the "P" strips.

And that's how it's done ...

I did a search on sealing the canopy and found that I put a complete set of photographs in a thread entitled "Sealing Canopy Side Skirts" by prkaye. I do have power point files I can send to someone if they want but I think this covers everything.

Only for you Bob Mills - now I think I will fix breakfast.

Bob Axsom
 
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Pat, just to clarify a couple things (thanks in advance):

- I get the part about extending the seal aft, for no snags. On the front, do you mean to make sure the upper forward corner doesn't snag on the forward canopy and leave a gap?

- What is CYA glue...that acronym is unfamiliar (well, at least in a glue context ;))

- On height experimentation, it looks like you ended up at about 3/4" (since the rail is 1" high. I can see shorter being less effective, but did you find higher was also ineffective? Figure I'll start with a direct imitation (you know what they say about flattery, eh!) :)

Cheers,
Bob

Bob,

Yes, exactly, on the forward end of the seal you just don't want it to snag on the roll bar fairing. I think you can get the idea from the photo here:



CyA = superglue (for former RC modelers). :)

Yes, the height is about 3/4", I got lucky and guessed right on the height on the first try. Bob is right, the surfaces are not parallel, but with this seal it doesn't matter. The seal will conform to the curvature of the skirt for two reasons, the seal is somewhat pliable and the suction force is very strong and it forces the seal to lay right up against the curved canopy skirt. So the height just has to be right for the amount of gap you have and the amount of curvature of the skirt. I think it will be obvious once you start playing with it a little bit.

I, like many slider guys, made up a brace to keep the skirt from flexing, here is the only photo that I could find of the brace that I used (the lower end is riveted flush with the canopy skirt):



For the rear skirt, I used the PTFE tape only. I lucked out and got a good fit so that's all I needed.
 
I experience a great deal of "tail air pumping", as evidenced by smoke filling the cockpit during show passes with smoke on. CO has not been indicated by indicator patches...perhaps the air moves enough to keep concentrations from building, or CO is heavier than show smoke, but its a good thing to watch out for! Would like to seal the canopy to keep the smoke from moving forward, and am hoping it may be a speed mod as well! ;)

Cheers,
Bob

Bob, one of the reasons I came up with this seal was that I was getting sporadic CO warnings on my sensitive detector. I think I would occasionally see about 15 ppm. I would open the vents wide and that would usually take care of it. Unless I slowed down, seemed to be worse then. I also prosealed the wedges in the corrugations on the baggage bulkhead and now I never get CO warnings. I'm convinced that I have just about eliminated my tail pumping problem, mostly I think by virtue of this seal. I think you're right, less tail pumping has got to equal more speed. :)
 
First of all let me post a link that is not directly related to make a point:

http://www.youtube.com/embed/MKikHxKeodA?rel=0

<snip>

And that's how it's done ...

I did a search on sealing the canopy and found that I put a complete set of photographs in a thread entitled "Sealing Canopy Side Skirts" by prkaye. I do have power point files I can send to someone if they want but I think this covers everything.

Only for you Bob Mills - now I think I will fix breakfast.

Bob Axsom

Holy cow Bob, you must've worked up a huge appetite with all that typing! Thanks very much! I feel like I just watched an episode of "How It's Made" (a show my boys and I like). Yours is a very elegant solution, for sure. And if you were comparing it to the secretary's cabinet in the video...I would tend to agree! ;) Nice work for sure, but perhaps suited to a pre-paint situation. I've been painting a lot of little mods lately, and am a bit chicken to drill my canopy skirt...I do not want to make one of those right now! But I admire your work, and appreciate your effort to share (I dug up all the old threads with your pics too). So as I move forward with copying Pat, please don't take offense! ;)

Bob,

Yes, exactly, on the forward end of the seal you just don't want it to snag on the roll bar fairing. I think you can get the idea from the photo here:<snip>

Makes perfect sense, thanks!

CyA = superglue (for former RC modelers). :)

OK, duh...V-8 salute! :eek:

Yes, the height is about 3/4", I got lucky and guessed right on the height on the first try. Bob is right, the surfaces are not parallel, but with this seal it doesn't matter. The seal will conform to the curvature of the skirt for two reasons, the seal is somewhat pliable and the suction force is very strong and it forces the seal to lay right up against the curved canopy skirt. So the height just has to be right for the amount of gap you have and the amount of curvature of the skirt. I think it will be obvious once you start playing with it a little bit.

Again, makes good sense, so simple a caveman (like me) can do it!


For the rear skirt, I used the PTFE tape only. I lucked out and got a good fit so that's all I needed.

My fuzzy-sided velcro also works well. Just need to fill the doghouse at the rear apex. Saw Bob's solution, but mine is glass, not metal, and smaller in height, so just need a material that will flex but not bind...cypherin' on it. Felt might work there...will see.

Bob, one of the reasons I came up with this seal was that I was getting sporadic CO warnings on my sensitive detector. I think I would occasionally see about 15 ppm. I would open the vents wide and that would usually take care of it. Unless I slowed down, seemed to be worse then. I also prosealed the wedges in the corrugations on the baggage bulkhead and now I never get CO warnings. I'm convinced that I have just about eliminated my tail pumping problem, mostly I think by virtue of this seal. I think you're right, less tail pumping has got to equal more speed. :)

In one attempt, I covered the baggage opening with visqueen before reinstalling the baggage wall. Worked OK...smoke infusion was diminished quite a bit, but not eliminated. Huge PITA too, everytime that wall comes off and on. I also sealed the seam along the fuse bottom just behind the baggage floor, to try to stop the pumping action via the tunnel (center of the baggage floor). Filling those corrugations is a good alternative to the visqueen...how far inboard did you fill...any pics of that?

It may be impossible to fill all of the leak paths from the tail, but if we can seal the canopy well, and get most of the path from the tailcone shored up, it should stop the pumping...and it would be great if that added measurable speed! ;)

Thanks for the discussion fellas! :)

Cheers,
Bob
 
In one attempt, I covered the baggage opening with visqueen before reinstalling the baggage wall. Worked OK...smoke infusion was diminished quite a bit, but not eliminated. Huge PITA too, everytime that wall comes off and on. I also sealed the seam along the fuse bottom just behind the baggage floor, to try to stop the pumping action via the tunnel (center of the baggage floor). Filling those corrugations is a good alternative to the visqueen...how far inboard did you fill...any pics of that?

Bob, I have to get into the rear today so I'll take a couple of pix for you. I'm going to say about an inch. The overlap of the baggage cover/bulkhead flange is not much, probably a couple of inches or so.



I used the 3/4" thick foam insulation that I had used to insulate the forward cockpit floor. If I did it over, I would probably extend the wedge seal inboard to cover the overlap (as you suggest). I stuck the insulation wedges on with proseal and made them taller than the corrugation so that they get compressed when the panel gets screwed on.

Sorry for the thread drift, guys. :)
 
Working on this now, Thanks for all of the great ideas.

When making the canopy skirts I did make these little bracket thingys to help support the rear lower corner of the skirts.

9AAD791B-29C0-48CD-89E6-D79AA4A853C3-18528-00000A868E0485C5_zpsb2d10111.jpg
 
Bob, I have to get into the rear today so I'll take a couple of pix for you. I'm going to say about an inch. The overlap of the baggage cover/bulkhead flange is not much, probably a couple of inches or so.

I used the 3/4" thick foam insulation that I had used to insulate the forward cockpit floor. If I did it over, I would probably extend the wedge seal inboard to cover the overlap (as you suggest). I stuck the insulation wedges on with proseal and made them taller than the corrugation so that they get compressed when the panel gets screwed on.

Sorry for the thread drift, guys. :)

Thanks Pat...that makes sense too. At first I thought you filled the triangles with proseal, and I was thinking about mess and weight. The foam wedges make complete sense! Another V-8 salute!

And I have a "tunnel board" that looks just like that! The far end would be sitting above my strobe power pack and ELT, and the shop light would be leaning on my PC925 battery...weight and balance consequences of the big motor...and not fun to service...but that sounds like whining, doesn't it! ;)

Going back to the rail seal...was thinking about the gluing process today...does that material have a lengthwise curl to it? If so, did you affix the seal so the convex side is out, and thus when the suction pulls it outward, the convex side lays into the gap like a fillet? The point of the question is, just wondering how wide a glue line did you use on the bottom-inner part of the seal? Just along the bottom edge, and a small bead on the inner face to the rail? Probably overthinking it, but just wondering. Thanks!

Cheers,
Bob
 
I have no dog in this fight, but here is a link to Mr. Bob A's earlier reference to pictures.

http://www.vansairforce.com/community/showthread.php?t=5024

The search function of Google is fantastic. I can not match it with the in forum search tool.

In google type "site:vansairforce.com word or phrase1 +word or phrase2 . . . "
use some different words, dog, pooch, mutt etc.

VAF names search just fine too.

Now everyone can find what they need. (eventually, :D)
 
And I have a "tunnel board" that looks just like that! The far end would be sitting above my strobe power pack and ELT, and the shop light would be leaning on my PC925 battery...weight and balance consequences of the big motor...and not fun to service...but that sounds like whining, doesn't it! ;)

Going back to the rail seal...was thinking about the gluing process today...does that material have a lengthwise curl to it? If so, did you affix the seal so the convex side is out, and thus when the suction pulls it outward, the convex side lays into the gap like a fillet? The point of the question is, just wondering how wide a glue line did you use on the bottom-inner part of the seal? Just along the bottom edge, and a small bead on the inner face to the rail? Probably overthinking it, but just wondering. Thanks!

Bob, I don't blame you for whining--try it in 100% humidity 100? Florida heat! :eek:

The seal comes flat, but by the time you glue it in, it will adapt to the curvature of the canopy rail, convex, I guess. Anyway, it sits real pretty against the skirt with just the right amount of curvature. See here:



I ran my bead of CyA on the bottom of the seal. It's really a two-man job to get it right as you can imagine. Another option was to run the bead down in the corner of the canopy rail and then press the seal into the bead. I think I did it both ways and preferred the bead on the seal if you have a helper. A little bit of CyA is all you need. Get the thick stuff.

Here's the photo of the wedges:





Not that you need it, but here's a better photo of the skirt brace:

 
Thanks Pat, nice work! Agreed...100-squared tunnel crawling would not be much fun!

Time to order up some seal material!

Cheers,
Bob
 
I have no dog in this fight, but here is a link to Mr. Bob A's earlier reference to pictures.

http://www.vansairforce.com/community/showthread.php?t=5024

The search function of Google is fantastic. I can not match it with the in forum search tool.

In google type "site:vansairforce.com word or phrase1 +word or phrase2 . . . "
use some different words, dog, pooch, mutt etc.

VAF names search just fine too.

Now everyone can find what they need. (eventually, :D)


The forum search tool is terrible, which surprises me given the general quality of the rest of the forum software.

Wish it supported full regex searches :)
 
Do you know what durometer you used? 40, 50, 60, 70, 80?

Tosh,

Sealing a slider can be a challenge, but I think I found a pretty good solution.

I noticed that the air tends to exit around the base of the slider skirt, usually near the pilot's left elbow or copilot's right elbow. If you have on a long-sleeve shirt, sometimes it tries to suck your sleeve out through the gap! This in turn promotes a lot of what most refer to as "tail pumping," which is just flow from the empennage area to the cockpit through the rear fuselage caused by the low pressure over the canopy and the high pressure (relatively) in the tail area. Obviously, this also increases the risk for carbon monoxide flowing from the engine to the tail and through the aft fuselage to the cabin. So if you can stop the air exiting under the canopy, you are also diminishing the tail pumping phenomena. I started experimenting with this a few years ago and came up with a pretty good solution. I think of it as a flapper valve: I glued a piece of flat rubber seal to the bottom of the canopy rail and then went up and flew it. I noticed that the suction pulls the strip of rubber tightly against the side of the canopy. I started with short strips just to see if it was going to work, and when it did, I went ahead and cut one long strip and glued it the entire length of the canopy rail. This really works well and will completely seal your canopy assuming you don't have leaks in other places. Here is the test strip:





And here is the completed seal:



Make sure you extend the seal beyond the end of the canopy rail such that the canopy will not snag it when you move it forward. Likewise in the front, be sure to cut it such that there is freedom of movement outboard to where it seals against the canopy skirt. The suction really pulls this seal tight against the canopy skirt and provides an excellent seal. You won't feel any suction pulling on your sleeve anymore!

I got the rubber seal material at McMaster-Carr and used CYA glue--a small bead along the bottom of the seal will hold it well. Mine's been on there a few years now and has not come loose. You will need to experiment a little in finding the right height for the seal, so plan on making a few test samples until you find the size that works best for you.

EDIT: I looked up the part number of the EPDM rubber seal on McMaster-Carr if anyone is interested it's p/n 8985K12, $5.37 for a 1/16" X 2" X 36" strip.
 
Do you know what durometer you used? 40, 50, 60, 70, 80?

I asked Pat and he used 50A, which is medium, I think . . .

I bought the 40, and test flew it today, with good results and some lessons learned (for those that may do this). I could see slightly stiffer being good too.

First off, thanks again Pat...works really well!

I had no helper available so I opted for masking tape "helping hands":
IMG_0373.jpg


I used the small bead in the corner method for the CyA glue. Trick there is to get enough on to make the end stick, but not so much that it rides up the inside wall of the rubber more than just a smidge. I glued about 6" at a time into place. Overall worked well:
IMG_0375.jpg


During today's test flight, the entire flap did suck onto the canopy skirt, and formed a good seal. Right in the middle, where the gap to my canopy skirt is the largest, the top of the seal was perilously close to being sucked down enough to extrude out the gap. If I pushed it with a pen point, I think it would have poked through, and left a little gap open. I'll see how it holds up, but were I to do it over (and I may...I bought two strips of rubber), I'd start at 3/4" at the forward and aft ends, and arc it up to a full inch in the middle. Perhaps even have the center 6-8" be a plateau at 1" high. I think it would lay in perfectly if cut like that.

Behind the rail on each side, I used a small length of weatherstripping, idea courtesy of Ralph Inkster, Bill Beaton's running mate up in Calgary (thanks Ralph!)
IMG_0368.jpg


I also used another of Ralph's ideas, using wider weatherstripping around the perimeter of the roll bar. It squesezed in nicely when the canopy closed, but since I was experimenting with different lengths and cuts to see how it fit the curves, it looks kinda hokey to me. I'll go back and see if I can use one piece all the way around, and work on the aesthetics a bit. But if worked!
IMG_0371.jpg


At the back of the slider, I've been using a layer of soft-side velcro under the back edge of the skirt for a while. There is a larger gap on the inner 8" or so approaching the center rail, so I added a short layer of velcro to the edge of the fuselage in that area:
IMG_0367.jpg


The center part of the velcro strip above (that looks to be sagging) is suspended over the skin cutout that the slider block passes through. My hope is that flap sucks up to the slider in flight...we'll see.

I used a two layers of gray felt weatherstripping in the doghouse over the rail. One layer full length, and one layer half length, to fill the angled opening.
IMG_0365.jpg

Bob Axsom and Ralph Inkster each had neat ideas for this complicated-to-fill void...far more elegant than this...but I'm hoping that my simplistic approach seals well, and that the center part of the lower velcro on the fuse schmooshes up with the velcro and felt on the canopy. Fingers crossed!

The test flight went well this morning. I mentioned the one issue of the center section of the side rail seal, but all in all, I felt no tug on my sleeve from the side gap, and I burned through about a gallon of smoke oil...and not a wisp of smoke came in the cockpit. Very cool result for a guy that gets teased for going IMC in the cockpit by his formation buds! ;) And that test was without the baggage wall corrugation triangles filled!

I did that part of the job this afternoon. I used some air conditioning weatherstripping. Its soft, but should conform well to the triangles, and as Pat suggested, I left it a bit proud, so it compresses when the wall is installed. It comes as a long 1.25" square-shaped piece, so I cut 3" lengths, then cut each length down the middle to make the triangles (with a bandsaw):
IMG_0358.jpg


I glued it in place with Permatex weatherstripping adhesive, brushed on with an acid brush. Turned out like this:
IMG_0360.jpg


Next test will be a nice long X-C to KC, for the KC Flight NFL Breast Cancer Awareness flyover on the 13th (Chiefs-Raiders pre-game...set your DVRs!). It will be interesting to check the smoke influx a bit more, to confirm the results, as well as see if X-C performance (TAS at specific power settings) is improved in any measurable way.

Thanks again for the ideas Pat, Ralph and Bob Ax!

Cheers,
Bob
 
Thanks for the updates Bob, I'm ordering my wx stripping on Monday. Does your velcro under the slider rail suck up to the slider rail in flight?
 
Thanks for the updates Bob, I'm ordering my wx stripping on Monday. Does your velcro under the slider rail suck up to the slider rail in flight?

Andy,

That's the one item I forgot to check in flight. Might need to do another test hop, eh! Maybe give someone a ride and have them look closely at it! ;)
Will report back!

Cheers,
Bob
 
With all of the weather stripping filling in the gaps, I'm wondering how well the engine exhaust/ heatmuff heating for winter operations will be. With reduced air flow through the cabin, heat may also be reduced.

In a home, with forced air heating.........if a room's door is closed without a return air, or sufficient gap under the door, that room will just remain colder than other sections of the house, until the door is opened.

As to how this applies to our RVs, I haven't checked it out. Just wondering.
 
Heater performance with sealed canopy

Airflow with sealed canopy will be noticeably less, but the retained heat without all the drafts more than compensates & very acceptable for Canadian conditions. For folks South you may notice a bit less volume from your air vents.
Bob, check if sealing side rails has any effect on race speeds.
Cheers
 
With all of the weather stripping filling in the gaps, I'm wondering how well the engine exhaust/ heatmuff heating for winter operations will be. With reduced air flow through the cabin, heat may also be reduced.

In a home, with forced air heating.........if a room's door is closed without a return air, or sufficient gap under the door, that room will just remain colder than other sections of the house, until the door is opened.

As to how this applies to our RVs, I haven't checked it out. Just wondering.

Makes sense Larry...I will check it out. My heat and and vent air both come in via my Stein vents (via a mix valve fwf), so I should be able to feel if there is a decrease in flow (as you and Ralph have said...I think you're both correct).

Airflow with sealed canopy will be noticeably less, but the retained heat without all the drafts more than compensates & very acceptable for Canadian conditions. For folks South you may notice a bit less volume from your air vents.
Bob, check if sealing side rails has any effect on race speeds.
Cheers

Ralph...speed impact is definitely on the to-check list. Seems it would be a positive impact...but ya never know with these crazy air molecules! First check will be the X-C cruise performance later this week.

Roger Bob, more than happy to ride along anytime!

Ya know Andy...I'll be at your 051/48 next weekend. Arriving KLXT Friday, and two practice sessions Saturday (with Chiefs players and cheerleaders on site that day). It'd be a fun day to visit Lees Summit! Will be there for a few days after too. Maybe we can check those seals while there, eh! :)

Cheers,
Bob
 
I finally made some progress sealing my canopy, the bulb seal I tried was too thin. 5/16 thick worked on half the rollbar, but needed 7/16 for an airtight fit. McMaster-Carr didn't have another bulb seal (cheap) that would fit th bill so I bought two different densities of foam 1 inch wide and 1/2 inch thick. I like the feel of the neoprene Wx resistant foam (not prone to ripping/tearing) but it was too dense. After applying it to the roll bar the canopy was 1/8 inch from closing. The super cushioning polyurethane water resistant foam worked well, it went on in 1 piece 1 inch wide and 1/2 thick with the adhesive backing. The canopy closes and the foam compresses well.
65EE31D8-6991-4DFC-ABA3-2E1F237FAA1F-8819-0000055DA96DC101_zps17462ef4.jpg

48D0A5CF-6CE9-4698-BCC1-63ED9146A32F-8819-0000055DB98D945A_zpsc22d51a3.jpg


For the side skirt seal I used the same EPDM 2x36x1/16 rubber Pat and Bob used. Using Bob's recommendation I put a pice of cardboard against the slider rail and traced the fuselage curve from underneath. Using 3/4 inch height on each edge gave a 1 inch height in the middle. The extra height in the middle gives more sealing material since the skirt is farther from the slider rail in the middle. Thanks for the tip Bob!
8A3C03E1-A26A-452A-9D76-BA5BF9D53C9C-8819-0000055DC93DA8FF_zpsfe84e06b.jpg


I ran the seal 1/2 inch under the windscreen fairing and put a bead of superglue at the slider rail/canopy deck junction in 6 inch increments. I can't believe how well the superglue worked, I also ran a bead of superglue on the outside edge of the rubber to the canopy deck. I was going to use the superglue to temporarily hold it in place and back it up with some weatherstrip adhesive but I don't think it needs it.
D87C58BE-44B4-414D-A21E-14E2754D2431-8819-0000055DD5986C67_zps3ef385ef.jpg


From the previous pic you can see I extended the skirt seal all the way back. I used some of the leftover neoprene foam as a backing for the rubber seal aft on the canopy pin blocks.
4F877DBF-DF18-46B1-B3A7-7D83FE84A3FA-8819-0000055DDBC14C8C_zps5c5b1dd5.jpg


Since I had the canopy off anyway I decided to make a doghouse plug for the slider rail. I have the original UHMW plug from vans but its so flimsy after I sanded it enough too fit I'm not confident it will work. I used packing tape on the doghouse and leftover foam to build up the edges, waxed it up and poured in some west systems epoxy/filler/flox. We will see if it will make a usable wedge to seal the rear slider rail.
158B5D7F-7C43-45B0-AB78-519DA34FABB1-8819-0000055DE7DCE151_zpsacf34a42.jpg


Thanks to Bob, Pat and Bob for all of the ideas, especially Bob for letting me observe the seals in action!
 
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A note on Pat's flapper seal

Pat recommends leaving a small gap between the front edge of the seal and the windscreen fairing so it can shift outboard against the skirt. I flew with mine for the first time today and it works as advertized.
 
I ran the seal 1/2 inch inside of the windscreen fairing, my side fairings slide underneath the windscreen fairing so the seal should lay on the side skirts. I think this method will seal more length of the skirt, if for some reason it won't lay right its easier to cut a little off than add some. Hopefully I'll be able to test fly it soon!
 
Flapper seal at the windscreen

Good plan, and good luck with it.

I"m trying to adapt Pat's seal to the rear skirt as well.

Yesterday I installed a 1" wide strip of EPDM rubber on the fuselage skin overhang of the baggage compartment from the end of the side rail seals (that I have extended past the rear end of the UHMW blocks all the way to the rear end of the canopy sill) up to the doghouse on both sides. The free, forward edge of the seal extends 1/2" past the skin and is secured on the trailing edge with plastic tape.

My theory, yet to be flight tested (today), is that the airflow from the cockpit to the outside will press the free end of the seal up against the canopy skirt just like it does along the side rails. The advantage is the ability of the rubber to conform to whatever variable gap exists.

If it works, I might try reversing the seal so it's attached to the underside of the skirt and the free end is pressed down onto the fuselage skin. This would effectively hide the seal. It doesn't look bad the way it is, in my opinion, but it's something to consider.

Tosh

 
Aft Flapper Seal Inflght Test Report #1

As mentioned in a reply to crabandy's post, I'm investigating the possibility that Pat Hatch's flapper seal idea for the canopy rails can be used along the aft canopy skirt-to-fuselage junction, either attached to the underside of the skirt or the top of the fuselage with the free edge facing forward.

Two days ago, I installed a seal on the fuselage, and I've included some pics to show you the idea, which is that the outflow will grab the free edge of the seal and press it against the skirt.

124 ? junction, side flapper to aft skirt flapper



125 ? left side aft skirt



126 ? inside view of left side aft skirt



129 ? the whole deal



A fellow RVer and I flew yesterday to test it out. We had a length of yarn on a dowel to check for airflow around the canopy-to-fuselage junction from the end of one side flapper seal all them way around to the other. Here are the preliminary results, and references to clock position are as viewed looking aft:

1. Airflow in the cockpit to the rear does lift the seal and press it against the underside of the canopy skirt.
2. The amount of airflow and how well it moves the seal varies depending on clock position.
3. The most effective action on the seal is from 9-10:00 and 2-3:00.
4. At 10-11:00 and 1-2:00, the seal wasn't being pushed up high enough to reach the skirt. I think there are four factors causing this:

a. The gap between the fuselage and skirt is greatest there.
b. I had taped the 1" strip of seal with only half of the width extending beyond the edge of the fuselage.
c. The seal has to conform to a compound curve there, which reduces the flexibility of the rubber.
d. The rearward airflow was less than that at clock positions closer to the 3-9:00 line.

5. Testing the airflow with long pieces of yarn on a dowel isn't sensitive enough for determining what's going on. I now have a telltale about 3" long, which will react to much less airflow.
5. And the real surprise . . . at 12:00 the airflow through the doghouse appears to be forward into the cockpit rather than to the rear out of it.

My conclusions:

1. The concept is sound, but getting the most effective seal will take some trial and error.
2. My first change is to reattach the seal so that very little of the rubber strip is in contact with the fuselage skin, which provides almost 1" of free rubber for the airflow to push against. I got that done yesterday afternoon and plan to test it today.
3. I may need to relieve the tension at one or more points where the rubber has to conform to a compound curve. A few slits perpendicular to the leading edge, maybe?

I'll let you know what I find out on the next test flight. When all is said and done, we may find that Pat Hatch's flapper seal has expanded its utility!

Tosh
 
Andy,

That side seal looks great...just the way we were discussing it! I think it will work great. Flying back from KC last week confirmed our concern about the 3/4" seal height in the middle of the side rail. The rubber strip is just about tangent to the skirt in middle, perhaps with a tiny gap at the very center. The seal can be pushed out through the gap easily. 1" in the center should be perfect!

WIll be interested in what you come up with at the doghouse. That gap remains unfilled on mine, as you saw that day in KC.

Tosh, also interested in how that seal works at the aft gap...neat idea! And I'll check the flow at the aft doghouse gap too...inward flow there is an interesting discovery!

Nice work guys!

Cheers,
Bob
 
Aft Flapper Seal Inflght Test Report #2

I've been communicating with Pat Hatch about adapting his flapper seal to the aft canopy-skirt-to-fuselage junction, and would like to relay a few relevant points from that discussion.

The best canopy seal is to fit it precisely in the first place. With due respect to the builder of mine, this is an area in which he could have done better. Getting help building a new canopy isn't an option at the moment, so I'm stuck with finding a solution to deal with what I've got.

Airflows around the canopy are a complex mixture, and the fit of each individual canopy presents a unique sealing task. That said, the differential pressure along the sides is substantially greater than along the aft skirt, and I've verified that inflight with a short piece of yarn on a dowel. Before I added any seal, when the tip of the yarn was held near any side gap from the windscreen all the way back to the end of the canopy sill, airflow out of the cockpit grabbed the yarn and streamlined it like a coon tail on car antenna :D

That's why I added a piece of angle aft of the UHMW blocks to the end of the sill. This provided a vertical surface for gluing the seal, so that mine is a continuous piece from the windscreen all the way back. I also cut the EPDM rubber strip from McMaster-Carr right down the middle to create two 1-inch-wide, 36-inch-long strips. The little extra height ensured that the seal doesn't come close to popping out and under the bottom edge of the skirt, and the rubber conforms nicely to any variations in the inside surface of the skirt like a rivet, for example.

Inflight testing with the yarn has confirmed that the aggressive outflow of air from the cockpit continues up and around the aft skirt of my canopy for about 10-12", where it tapers off to nothing. The boundary gradient from high flow to zero is very sharp, and I think this is due to a combination of two factors: 1) the differential pressure between the cockpit and the atmosphere is much less back there, and 2) this is where the skirt on my canopy is the tightest against the fuselage.

One flow discovery really surprised me, however. When comparing the airflow from the center rail at the doghouse (which on my airplane is effectively zero) to the left and right along the aft skirt, the left side outflow is also zero, but the right side has a point a few inches long at which the yarn flutters forward into the cockpit. That is occurring at a point where the canopy fits the tightest, but there is a short section in which the curve of the skirt lifts very slightly from the fuselage.

My explanation of this is that airflow across the canopy creates a suction that deforms it just a bit and lifts the trailing edge of the skirt.

But here's the really surprising part: if you think of viewing the aft canopy skirt from inside the cockpit inflight, from the center rail to either side for about 10-12" or so, the flapper seal is laying in its static position just like on the ground, and the gap above the seal to the bottom of the canopy skirt is about an inch or so.

And yet with the exception of that short section in which air flows into the cockpit, the net flow is zero.

It's important to note that I may have failed as a test pilot in assessing the effectiveness of the aft seal, however, because I changed more than one thing from the previous flight by adding some sticky-back pile Velcro to the trailing edge of the canopy skirt to fill in the gaps.

My canopy sits tight against the fuselage from the doghouse to about 18" around the skirt on both sides. At that point, a very slight gap begins, increasing to maximum at the bottom rear corners of the skirt, then begins decreasing along the horizontal skirt for about 6-8" where it reduces to nothing.

To determine where to put the Velcro, I slipped a piece into the gap between the skirt and the fuselage and worked it toward the point where the skirt was tight against the fuselage. As soon as it began to bind, I marked that spot, repeated the process at the other end of the variable gap, then attached a single layer strip of Velcro to the underside of the skirt along that perimeter. I repeated the process to add additional strips until the gap was filled.

This has to have an effect on the flow of air through the cockpit, but I can't separate that from having extended the flapper seals farther beyond the edge of the fuselage skin overhang before this second test flight.

Those two changes in combination, however, resulted in the following summary conclusions:

1. From just aft of the UHMW blocks where I added length to Pat's rail seals and up to about the first 10" of the fuselage skin overhang, it is clearly apparent that the rearward airflow is shoving the seal tight against the canopy skirt. If I pull the seal away from the skirt and drop the end of the yarn telltale into the gap, the yarn is visibly pulled to the rear with the escaping air. It's important to note that with my relatively ill-fitting canopy, this is also the area that has the largest gaps to contend with.

2. From there up to the doghouse, the seal appears to be in its static position with a fairly large gap between the seal and the canopy skirt. The same is true from the doghouse down to about 10" from the canopy sill on the opposite side.

3. When the telltale is placed in this gap on the right side of the aircraft, it streams forward. When placed in the vicinity of the doghouse, it falls straight down. From the doghouse all the way around the aft skirt on the left side of the aircraft to about 10" from the canopy sill, the telltale is static.

4. The combination of a flapper seal and pile Velcro has greatly reduced the flow of air out of the cockpit all around the canopy.

My original goals for the canopy were 1) get the best fit I could without having someone who knows what they are doing build me another one, 2) install the tipper mod, and 3) seal it better. I've accomplished all three, and at this point I see no reason to try a different approach to using an aft flapper seal (like attaching it to the underside of the skirt rather than on the fuselage).

For me, the most useful lesson learned is that Pat's original idea of the flapper seal can be extended along the entire perimeter of the canopy-to-airplane junction. There may be areas along the junction in which the seal isn't necessary because the canopy fit doesn't need it, but that's one of the advantages of the flapper idea to begin with. It reacts rather than being a static solution.

Anyone's final results will vary based upon the fit of the canopy, but there's no question in my mind that wherever the air is flowing out of the cockpit, Pat's seal can be an effective method for dealing with it.

Tosh
 
Here are some pics of the aft flapper seal with captions

126 detail of angle added for flapper aft of bayonet blocks (and unlike the caption shows, I installed a flapper seal, not a sea.



129 overall look at airflow results



132 inside view of airflow results



134 close up of airflow results



135 closer view of static area

 
Great write up Tosh! Somehow I bumped the "thumbs down" while typing this, not sure how to erase it.

There is probably a better way to make the plug, but here is my epoxy/flox plug after drilling and filing.
55C36EC0-6384-4D87-BC89-32AA9345ECA6-11462-000006A93C349853_zpsc252ada1.jpg

63BBF19A-290D-4D7E-A162-E3214FA0E745-11462-000006A9437E5291_zps0751e8a0.jpg


Seems too seal fairly well but I still have to figure out how to attach it. Some sticky foamy in front of the block stuck under the canopy fairings/doghouse should complete the seal.

My fairings originally fit perfect, side fairings are still tight but the addition of the foam on the roll bar and reassembly left a small gap on my lower left skirt. I will probably fill the gap like Tosh recommended with the cushy Velcro where it fits snug when closed. I had tried Velcro under the entire skirt but it was too tight and the canopy wouldn't quite close.
 
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crabandy's doghouse plug

crabandy,

It looks like your plug will do the trick, but it's not something on my radar for three reasons:

1. I used Velcro to fill the gap, and it's easy to conform the filler to the shape of the doghouse.

2. The airflow at my doghouse is neutral. I don't know whether that's due to the Velcro filler, the very low differential pressure at that position on the skirt, or a combination of the two, but there's nothing left to fix there.

3. I have the Ward tipper mod, and the slider slips in and out of a notch in the "T" rail. The plug wouldn't allow the canopy to tip unless I relieved the entire aft portion of the rail, not something I would relish doing.
 
Tosh,

Nice report...great pics! You paint the picture very well! I like the idea of the "PH" seal around the aft section.

On mine, loop-sided velcro has been doing the trick on the aft portion of the canopy, with the exception or the inner (furthest aft and up toward the rail) 8" on each side. I added more loop velcro on the fuselage in that area, so the velcro rides face to face in that area, and the only gap left now is the doghouse and about an inch on each side. Interesting that you show no flow in those inner 8" on each side, and little or forward (inward) flow at the doghouse. I will try to duplicate your results, and see if my velcro is really working there as well.

The differential flow and lifting of the canopy (side to side) is interesting too. I wonder if propeller slipstream around the fuselage is having an impact there.

corkscrewing-slipstream.gif


Some neat observations, and thanks for the work!

Andy, nice looking piece of work there. I need to get a better look at the gap I have back there, and see what the airflow is doing, then work a solution. How'd you do the final shaping...and are you going to glue yours to the rail?

One thing is for sure...there is a lot less air escaping from the cockpits of a few sliders! I had a very good test in KC the Friday before Chiefs flyover. We did a 4-ship flyover of a Friday nite HS football game just after sunset. I didn't get a wiff of show-smoke in the cockpit, and there are numerous pilots that will tell ya that was not the case before...cough, cough! :D

See what you started Pat! (and Bob) ;)

Cheers,
Bob
 
The doghouse and Velcro

Bob,

I added strips of Velcro laterally to the doghouse so they follow the flattened "U" shape, which seals the space between the top of the rail and the bottom of the skirt as well as the corresponding sides. The strips can be extended to either side as a single piece if necessary. To deal with the variable height of the gap above the rail, I added an additional strip or two to the aft end of the doghouse where the gap is the greatest. The sticky side on top of the fuzzy side adheres very well.

We're getting the same sealing effect with Velcro around the rest of the aft skirt, the only difference being that I wanted to try Velcro-on-Velcro on the underside of the skirt rather than using a strip on the fuselage. With my ill-fitting canopy, this allowed me to install a seal of variable thickness (ugly!) and conceal it.

The technique of slipping a short length of Velcro with the backing tape still on it into the gap and sliding it toward the narrowing end until it binds worked well to identify each end of the gap I needed to fill. With that first strip installed, I repeated the process to fill in the rest.

Interesting idea about the propwash effect, although the reason for the relatively static flow in that area of the skirt probably includes a number of factors, and the yarn test allows you to identify what's going on where, and thereby assess the effect of each additional sealing attempt.

One factor I failed to point out in the photos is the effect of curving the rubber. Beginning on either side at the end of the canopy rail, taping the strip to the fuselage skin requires little bending of the rubber in a direction perpendicular to the edges.

But in order to transition from the side of the fuselage to the top, the rubber has to be stretched slightly, and this reduces its flexibility a little bit. I could see the effect in the leading edge of the rubber where it formed a gentle arch, and feel it when lifting up on the leading edge at that point to test how much force was required to push it up against the bottom of the skirt.

Before the first test flight of the aft flapper seal, I anticipated having to come up with a way to relieve the tension in the rubber so it would lift more easily with the escaping air. My original plan was to deal with that by cutting a slit in the rubber perpendicular to the leading edge at the midpoint of the arch to see if that would allow the rubber to lift up more easily.

But that became a moot point when I discovered that with the exception of one short section where the air flowed forward into the cockpit, the length of the seal with the arch had static airflow. I didn't need the seal there, and the reason has to be that these sections correspond to the tightest fit of the skirt against the fuselage.

I'm guessing at this point, but the slight forward airflow in that one section is probably the result of a very slight mismatch between the curve of the trailing edge of the skirt and the fuselage about 6" to the right of the doghouse in the middle of that section of skirt that fits the tightest. It's not nearly enough to accept a strip of Velcro, but considering the differential pressure between the cockpit and the atmosphere, combined with the lifting effect of that pressure on the canopy in flight, I think the gap increases just enough to allow air to pass through. Why it moves forward is still an interesting aerodynamic question, but from a practical perspective, I may try something to close that area off.

Rather than install a strip of Velcro right along the trailing edge of the skirt at that point, what if I tried one farther forward? I'd be looking for a point at which the Velcro is compressed against the fuselage when static, so that it's still an effective seal even when the canopy skirt lifts a little bit in flight.

That's on my list of things to do. I cut a length of aluminum rod (probably about 1/8" diameter), drilled a hole through it at one end to accept a 4" cable tie, and tied a short piece of yarn to the loop. Just for fun, I polished it to a chrome-like shine. Maybe I'll offer them for sale as Tosh's Cockpit Airflow Tester.

Seriously, I'll be carrying the device for awhile to fine-tune the seal of my canopy.

And while I'm at it, thanks to you for your excellent detailed post on sealing the corrugations in the panels.

Tosh
 
Another successful install!

I cut the 2" strip right down the middle. That resulted in a 1-1/16" strip on each side. I wanted them taller because my passenger side has close to 1/2" gap at the bottom slider fairing. Worked like a charm! It was 32deg at the airport, close to 15deg at 5500ft, and for the 1st time, my cockpit was WARM!!

I'll probably trim to 1" because they extend above the rail and your hand hits them getting into the plane.

Thanks for R&D gents!
 
Brian,

We don't have to deal with that problem very much down here in Texas, but another post in this thread specifically addresses the issue of whether successful sealing can have a negative effect on warming the cockpit, similar to closing off a room in a house and how that can create a cooler rather than a warmer room.

During my test flights of the aft flapper seal, I tried open and closed fresh air vents to see if that had any effect on airflow past the skirt-to-fuselage boundary, and it didn't appear to change anything. It's important to note that I've also sealed the corrugations in the baggage compartment panels as described by Pat Hatch and Bob Mills in this thread, which reduces/eliminates airflow into the cockpit due to tail-pumping.

It's probably safe to say that we don't want to create a static airflow environment in the cockpit even if we could. Fresh air, either at OAT through the vents or heated air, is a good thing, and your success with improving cockpit heating is another positive benefit of the flapper seals.

I'm going to leave my seals a little high as cut right down the middle. Pat reports that the CyA glue has held the rubber securely to his rails for long enough to prove durability, so I don't anticipate that having the strip a little higher is going to cause any problems.

Tosh
 
Thanks Pat! Read your article, ordered the rubber, cut it in 3/4 pieces. That took 45 min +\-. It took less 20 minutes to install both pieces. Absolutely a remarkable difference. It worked perfectly, thanks. I have to fly back from sunny Florida to freezing New York in the next week and this is certainly going to make it A lot more enjoyable trip. Thank you again.
 
This is a great thread, thanks for all of the great ideas. I used foam for the rollbar and rubber strips for the slider rails and tight metal skirts for the rear. I have the single heat muff except I RTV'd the baffle inlet so it's only 2/3 the original opening. I have been pleasantly surprised that I'm comfortable without a coat but my feet get kinda hot at 18 F OAT with the cabin heat full open. I've found the High setting of the heated seats is really hot, low is doable. I'm sure my wife will think the High setting on the heated seats is just right. At 30 OAT I've found heated seats off, heat cracked open and both fresh air vents 1/3 open is comfortable in a long sleeve tee shirt. I don't think I'll bother installing stick boots. As others have posted 2 computer fans mounted under the glare shield will pull heat from the avionics as well as keep the windscreen defrosted, I'm able to pull the canopy closed prior to start and the windscreen stays clear while the rest of the canopy frosts on the inside.
 
I wish it were easier for me to post pictures on here, but I found a weather stripping product at Home Depot that I used very easily and effectively to seal the rear of my 6 slider canopy. - The whole process took less than 5 minutes. It is Frost King EPDM Rubber Weatherseal ?D? profile. It comes in white, grey and black. I placed it along the forward edge of the entire back deck. It is incredibly soft and pliable, so when the canopy closes it will deform to fill gaps anywhere from 1/16? to ??. There is no rolling effect at that location because the rear of the canopy is moving almost vertically at that point in the travel. To me this seems like a much nicer solution than the Velcro trick and it looks very professional. I put a piece of 1 ?? X 5/8? foam rubber weather-stripping on the bottom side of the doghouse, and it seals that up nicely. I haven?t flown it yet, but it passes the light test.
 
rear skirt seal

On my rear skirt, I used silicone glue.

First I taped waxed paper to my fuselage, and sanded the face of the canopy skirt that would mate to it.

Next, apply a generous bead of silicone right at the adage of the skirt, and close the canopy up for the night. Once the silicone dries, it will be stuck to the skirt and be molded to the aft fuselage deck. Peel the wax paper loose, and its ready to go.

This was how I did it seven years ago... no photos, but could take some if interested.
 
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