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RV7 slider rear skirt tolerance?

JurgenRoeland

Well Known Member
Hi all,

I'm working on the rear canopy lock blocks and you can only drill these when the height of the canopy rear vs top fuselage skin is defined.
So I'm finetuning the height of the rear canopy at the sliding track.
I already decided that I would not go with the aluminum skirts but make a custom epoxy rear skirt.
I have never worked with epoxy before and was wondering how much height difference you can hide and work away using the epoxy method.

The rear of my canopy sits about half to full the thickness of the canopy over the center of the top fuselage skin (so higher).
Passed the 45° point toward the bottom of the canopy along the rear frame, the canopy sits in both sides about 7/32 inch below the extended line of the top fuselage skin at the sides.
On the low point, of the canopy frame, the sides of the frame nicely match the sides of the fuselage as required for the side skirts and the alignment of canopy lowercorner with the top fuselage skin is reasonably close.

If I lower the canopy, the gap on the sides becomes obviously even bigger.
If I raise the canopy, the gap gets slightly smaller but I get much higher above the center of the top fuselage skin.

Should I leave my position as is which means I would have to work away 7/32inch on the sides. Is that possible with epoxy and will it still look ok ?

thanks in advance for the advise

Jurgen
 
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Jurgen,
Welcome to the club. What you are experiencing is completely normal. I’ve spent most of my build time over the last 3 months trying to tweak that slider frame, using all sorts of home-made jigs, long pieces of lumber, etc….. I finally decided to make one area of the frame that fit nicely, and then deal with the other areas to make them look right. I liked the idea of being able to use the metal side skirts as designed, so I made the sides fit as perfectly as possible. I made my aft canopy skirt out of fiberglass/epoxy following the excellent advice provided by Larry Larson on this website and in KitPlanes magazine. I had to shim my canopy on the left side, both front and back to make it work out right, and will hide that misfit with a special long term silicone filler called Silpruf. The aft canopy skirt turned out well and fit the turtledeck skin like a glove. I still have some filling/shaping to do when I get my Super-Fil. I used the premium version of 3M packing tape to make the mold, as suggested by Larry, along with generous amounts of Kirker mold release wax. This was the biggest layup I’ve ever done, but it turned out nicely. When Larry did his, he made the aft skirt and side skirts all in one piece. I’ll try to send a few pictures. Larry’s whole process along with pictures should be available here using the search feature.

The mold before layup:

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I don’t know how to get rid of the pictures link to post other ones, so I’ll make another post.
 
CONT……

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The layup popped right off after cure. I had fine line blue tape under the layup that I traced to the cured layup before removing it from the mold so I knew where to trim. Trimmed and scrubbed off the amine blush in my brew kitchen sink, then bonded it back on to the aft canopy using a structural epoxy adhesive and a few through the fiberglass fasteners. Filling/sanding in progress. Very easy really, and it’s going to look nice after it’s painted.
From an operation perspective, I really prefer the sliding canopy……. building it, not so much.
 
Ok if I'm understanding correct you are roughly good in the center area of the aft bow, low in the corner like in the picture I attached, and good along the lower sides?

Not sure what method of canopy attachment you are using but keep in mind you can also shim up the canopy in the low spots to some degree.

Have you also looked into the ability of the frame to slide and clear the aft top skin? If you get it too low it will not clear.

Long story short, I'm betting with a bit of shimming and the use of a fiberglass skirt you can make up that difference. However you could also go down the road of bending the aft bows and getting the corners a little closer to flush but bending those bows is an absolute nightmare! It's hard to really judge your situation without pictures but it sounds doable from what I read. The fiberglass rear skirt can cover up a fair amount of misalignment.

Also, here is a link to my build log as I had a similar problem. Canopy work continues on page 38.
 

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Canopy skirt

Scott documented the process very well. That skirt will be nice.
I had to hide lots of problems. That's why I did a one piece fiberglass skirt. 7/32" is no problem.
The articles mentioned were in Kitplanes. I encourage buying a subscription. If not, the links are in my blog.
http://wirejockrv7a.blogspot.com
 
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I was good (level) in the center at the top, and also on the whole right side. The left side was low by as much as 3/16”, which I shimmed to level. The front bow was also low on the left side relative to the windshield, and I shimmed that also, although not quite as much. If you are high in the middle at the back, that’s not a problem if it’s within about 1/4”. You won’t see it after your glass work. Fiberglass is messy, but it’s very forgiving and easy to make it look like you want.
 
If Brian Milani, from Showplanes got ahold of this frame, and decided to make a Showplanes version…. then we would have something. A carbon fiber/honeycomb frame could fit any airframe - within limits, because it’s so easy to work with and change. Trying to fit a welded steel frame to a fuselage that has as many variations as there are kits, especially non matched-drilled kits like mine, is extremely rare. To get one that actually fits well is like winning the lottery. The beauty of the welded steel frame is that it is strong enough to perform as designed, although it is quite flimsy, and #1, it is very light. I know - I’ve had mine on and of the airplane trying to make it fit my airframe at least 100 times (not joking), and I can lift it with one finger. Can’t tell you how many times I’ve wanted to catapult that collection of misaligned tubing out onto the railroad tracks next to my hangar. Perseverance is your goal. You will eventually get a great slider canopy, but it will take a little extra effort.
 
Can’t tell you how many times I’ve wanted to catapult that collection of misaligned tubing out onto the railroad tracks next to my hangar. Perseverance is your goal.

+1 I only got legitemately pi$$ed off about 3 times during my build and the canopy frame was one of them!
 
One of the solutions I heard of was using the loop (soft) side of velcro tape and seal the gap. Currently my canopy is off, as I work on the instrumentation and engine, but once it goes back on, I plan on using the velcro technique. I haven't ventured too much into the epoxy layups, and not sure I'm ready to try that method yet.
 
-good along the lower sides?

-Not sure what method of canopy attachment you are using but keep in mind you can also shim up the canopy in the low spots to some degree.

Have you also looked into the ability of the frame to slide and clear the aft top skin? If you get it too low it will not clear.
pony 2 ?

indeed, it's only low on the lowercorners as you have marked in your picture.
I'm pretty high with the slideblock of the sliding track and even little too high I think on the top side. But lowering would make the side gaps even bigger.

I'll give it a try using those nylon shims between canopy frame and plexi. I don't think I can win much there as my frame is already drilled for the canopy en the holes are already countersunk and 5/32. putting too much spacers will probably change hole alignments further on. But I will definitly give that a try as well.
 
I’ve had mine on and of the airplane trying to make it fit my airframe at least 100 times (not joking), and I can lift it with one finger. Can’t tell you how many times I’ve wanted to catapult that collection of misaligned tubing out onto the railroad tracks next to my hangar.

I completely know that feeling and still feel the pain :) I spent 3 months trying to get this thing to apply to the curves and the bends as to be within all measurements. I came up with something very close and decided to go with that as everything I manipulated later messed it up again. So I thought it was the best I could get. It's drilled and with the canopy on it slides very easily.

I thought it would go lower on that real track but I guess that's normal. I'll try some shimming today and maybe raise the top a little higher even as suggested above.
 
indeed, it's only low on the lowercorners as you have marked in your picture.
I'm pretty high with the slideblock of the sliding track and even little too high I think on the top side. But lowering would make the side gaps even bigger.

I'll give it a try using those nylon shims between canopy frame and plexi. I don't think I can win much there as my frame is already drilled for the canopy en the holes are already countersunk and 5/32. putting too much spacers will probably change hole alignments further on. But I will definitly give that a try as well.

I would say if your canopy and frame is already drilled trying any shimming is playing with fire as it will undoubtedly misalign holes. Thinking about this some more I'm betting that just going to straight to fiberglass skirt will work out for you. That height difference shouldn't be a problem.
 
it will undoubtedly misalign holes.

Gave it a try and looks I can get away with max 2 nylon washers on those side bars. More would indeed misalign holes. I'll try to keep those under. All little bits help to get it closer to the final shape.

I just noticed another issue. The plans called to countersink the plexi and dimple the aluminum. When I drilled the canopy I was still thinking aluminum skirt and countersunk the plexi canopy at the rear row along the rear side bars.
If I make a plexi fairing, that is going to be an issue as I can't the dimple plexi skirt. Two times countersinking for the AACQ-4-4 pop rivets is probably not a good idea.
 
Fiberglass skirt

Dan would be the one to ask but heres what I would do.
Use 1/2 the holes to attach the canopy as designed. Save the other half to cleko the fiberglass skirt to the canopy using Sika or other adhesive. After it sets, fill the holes.
Just an idea.
 
I did as Larry said above. Solid attach hardware spread out to about half what the plans call for, supplemented by a structural adhesive recommended by Gougeon Brothers (West System) for this application. My solid fasteners were mostly #6 screws going into rivet nuts with a nylon washer surrounding the rivet nut shoulder. The hole in the plexi for the #6 screw was 3/16”. The countersink in the plexi was done before enlarging the holes so I could use my piloted countersink cutter - as recommended in the plans. The aft bow tube is too small to allow the use of rivet nuts, so I used a few pulled rivets there. Holes for the rivets were enlarged to 5/32” per plans.
 
Thanks for the ideas everyone. Sounds like the attachment as in the manual with added bonding of the epoxy skirt as you suggested seems like the best way to go.

Everything is fixed in position now, the slide track screwed on and rear blocks drilled. It's all fitting good. Time to get started on the side skirts now.
 
Order of assembly

Thanks for the ideas everyone. Sounds like the attachment as in the manual with added bonding of the epoxy skirt as you suggested seems like the best way to go.

Everything is fixed in position now, the slide track screwed on and rear blocks drilled. It's all fitting good. Time to get started on the side skirts now.

Sounds crazy but I recommend leaving all the adjustment parts till the whole thing is done.
Front legs, HDPE blocks & the Aft height adjustment.
That takes some of the pressure off getting everything perfect. Not much help now but might help the next builder.
 
All of this discussion on this slider canopy - and this is just one of many threads on this subject - leads me to the belief that the fly in the ointment here is the welded steel slider frame. When you try to marry this steel frame to infinitely variable riveted aluminum airframe, and then try to enclose it all in flat sheet metal skirts, you are setting yourself up for failure. There have been 2700 RV6’s built and I know there are several, maybe many, that have used sheet metal skirting, but I don’t think there are many - maybe none - that have been finished as designed. That means no gaps anywhere. I’ve never seen one, but I’ve only seen a few hundred all metal configurations. If the slider frame was designed in composite, then any airframe would be compatible. Sand a little off the canopy frame here, add a little there - easy-peasy. Glue the plexi to this frame, and you have a very low stress canopy build that fits like a glove, and you didn’t drill a single hole. Differential expansion rates with temperature variations becomes much less of a concern.
I know that a metal frame under a plexiglass canopy or window is the way it has been done for a long time, but there have been so many gains in advanced molded composite structures that there might be a better way of doing something that has caused so much frustration by following conventional construction techniques.
 
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