Slider Canopy Sideskirt

I've often wondered why every RV slider I've ever seen has the canopy sideskirt joggled flush with the top of the sill at the forward end. Seems to me this is a sure way to invite air seepage. My canopy sideskirts overlap the sill by 7/8" from front to back and spade underneath the fiberglass when the canopy is closed. Not only do I think this looks more cosmetic, but should cut down appreciably on the amount of air and noise entering the cockpit from the sideskirt area, but I really won't know for sure until first flight. Canopy travel is very light, with no binding whatsoever and one hand operation in a cinch. When the airplane is eventually painted, I'll probably install UHMW tape on the inner surface of the sideskirts to help prevent scuffing the paint.




Rick Galati RV-6A "Darla"

That is the intuitive way but...

I sent all of my information to Ken Scott but I DO NOT believe the intuitive - "wrap around the fuselage side skin" is the best way to go. The fuselage side is convex at this point so when fully closed the front of the canopy is more narrow than a few inches aft so some method of compensation is required in order to open and close the canopy. At flight angles of attack the protruding lower edge of the skirt actually acts as a draggy airscoop.

In the plans, my 1996 vintage design from Van's calls for a fuselage overlaping tab at the rear of the canopy skirt covering the gap between the end of the roller track and the aft upper skin similar to the design you have for the full length of the skirt. The obvious paint scraping potential convinced me there has to be a better way. I cut the side skirt bottom parallel with the canopy deck for the full length in the closed position. Now if you rivet 3/4" angle to the top of the longeron from the end of the roller track to the inside of the upper aft fuselage skin at the rear of the canopy deck you produce an overlaping interface without the hanging closure tab. The rear canopy lock pins drop down behind the angle with no interference whatsoever. I installed support straps of aluminum vertically form the inside of the canopy frame (pop rivets here) to the side skirts (solid rivets here) similar to the welded tabs that George Orndorf shows in his video.

Now what if there were two consistently parallel surfaces that remain perfectly aligned over the full range of the closure motion. OK there aren't any but half is there and you can make the other. To do this you make a precise pattern out of file folders using the method where you 1) mark off the sill outboard of the roller track in 1/2" increments [in my builder's photo log it looks like I actually marked the surface in 1/4" increments], 2) use a square to measure the distance from the maximum extension of the roller track extrusion radius to the edge of the fuselage and record the measurements in a table, 3) repeat these steps for both sides to assure precision in making parts that will be slightly different for left and right sides of the canopy, 4) make up patterns for both sides, 5) trace the patterns on 3/16" aluminum bar stock with a small pattern overhang that will provide the precise gap between the edge of these "canopy skirt ribs" and the roller track extrusions, 6) drill rivet holes through the 3/16" wide ribs with the spacing you feel is necessary, 7) measure the height of the maximum horizontal extension of the extrusion radus, 8) mark the skirt at this height and clamp the rib to the skirt in line with the mark, 9) use the holes in the rib as a drill guide for drilling the skirt and clecoe the rib and skirt together as each hole is drilled to assure perfect alignment and matching hole patterns, 10) remove the rib and countersink the holes on both sides of the rib and dimple the skirt, 11) rivet the ribs and skirts together with a squeezer in such a way that the manufactured flat head is on the outer surface of the skirt and the shop head is also formed as a flush head on the inboard surface of the rib, 12) go back and use the file folder patterns to layout sealing surfaces on sheet rubber setting the pattern back from the rubber edge enough to produce a rubber part the will extend the exact amount you want it extend past the edge of the rib for contact with the parallel surface of the roller guide extrusion, 13) glue the rubber to the underside flat surface of the rib with 3M Weatherstrip Adhesive. As the canopy is closed the rubber seal will ride down on the under side of the maximum extension of the extrusion radius compensating for any reasonable over extension or irregularity in the rubber and provide an effective seal. The skirt will not flex or be drawn out in flight.

That takes care of how I handled the side skirt sealing back to the end of the roller guide which is the only tricky part. Aft of there the taper is always in the right direction so I just coated the added angles with wax (I believe) to prevent sticking, applied silicon to the inside of the skirt in this area and closed the canopy. I used the soft white "P" strip from Aircraft Spruce at the interface between the windshield flange and the roll bar to seal the front of tha canopy when closed and the same material on the inside of the rear skirt set back from the edge enough so it doesn't show to seal the rear. I made a small balsawood plug (Tracy Saylor idea) covered with a layer of fiberglass for strength and some "P" strip for a seal of the rear skirt track hole. It gets pushed back by the rear plastic canopy guide when the canopy is opened and it gets pulled forward into the closed position with a piece of nylon lacing tape (available from Aircraft Spruce for tying wire bundles the old fashion way) tied to the mounting bolt for the plastic guide. I have a little over 100 hours flight time on the plane so far a the canopy seal is perfect with no draggy overhangs outside the fuselage design moldline.

I could give you some images but I'm not sure how that works in this environment. I e-mailed a PowerPoint File and several JPG files to Doug Reeves tonight.

Bob Axsom

Rick6a said:

I've often wondered why every RV slider I've ever seen has the canopy sideskirt joggled flush with the top of the sill at the forward end. Seems to me this is a sure way to invite air seepage. My canopy sideskirts overlap the sill by 7/8" from front to back and spade underneath the fiberglass when the canopy is closed. Not only do I think this looks more cosmetic, but should cut down appreciably on the amount of air and noise entering the cockpit from the sideskirt area, but I really won't know for sure until first flight. Canopy travel is very light, with no binding whatsoever and one hand operation in a cinch. When the airplane is eventually painted, I'll probably install UHMW tape on the inner surface of the sideskirts to help prevent scuffing the paint.

Rick Galati RV-6A "Darla"

Click to expand...

After 8 hours of flight so far, I can say I am quite pleased with the performance of the unjoggled side skirts. The gap generated by flight pressures opens it to maybe 1/8". I'm certain that since the forward end of the skirt is "captured" by the fiberglass fairing, the bowing pressure is reduced considerably in that immediate area. Also as a data point, my canopy was constructed with newer updated parts that negated the need to weld tabs to deal with the vexing bowing tendency. I've rode in RV's sliders that develop far more gap than "Darla" and the main reason I decided to try something slightly different to deal with the problem. In one particular older year 6A slider I flew in, you could practically wiggle your fingers in the gap! If you visit Oshkosh this year, check out the Young Eagles RV-6A's. With the slider canopies in the closed position, you can see daylight between the joggles and the sill. How much air and noise do you suppose that generates? Of course my experience is anecdotal and as always, YMMV.

Zero Gap - the 3/16' Rib is the Answer not the Tabs

Rick,

The tabs are not the answer on my side skirt either. The essential thing of my side skirt installation that prevents the air gap and side skirt suck out in flight is the 3/16" aluminum bar stock rib and the rubber seal. I worried over this problem for years as I was building before I came up with this Idea and the tabs were already in place. It takes some effort to make them with a hack saw and file (process described in the previous message) but they are a perfect solution. You really ought to take a look before you paint. Since your skirt is already wider than the fuselage you may be stuck.





Bob Axsom

Outside view of skirt

I will post two photos - one open and one closed. The lower row of rivets is the one used to mount the rib in alignment with the maximum horizontal extension of the outer radius on the roller guide extrusion. The rivets are installed with the manufactured flush head on the outside of the skirt and the 3/16" rib is countersunk on both sides so the shop head is flush as well (double flush).






Bob Axsom

Rick,

After 112 hours, I remain very happy with my slider arrangement that is very similar to yours. It provides a very good seal with no discernible leakage in any flight regime. The only downside is the canopy is a little stiff to open about half way back as the skirts flex around the widest portion of the fuselage; no surprise.

I elected to add a .020" "catch plate" to the lower portion of the windscreen fairing to allow the leading edge of the canopy skirt to tuck-under that last 3/8 (or so) of travel. The aluminum catch-plate was fiberglassed in-place and has not (yet) proven to be a problem. It's a little more durable than just fiberglass.

Also, instead of welding tabs to the lower canopy rails to hold the skirt in-place, I used the RV-9 z-bend stiffener and just drilled and pop-riveted it into the canopy lower tube rail and the skirt. I recollect using the a hole-locator quite a bit during this operation.

Lastly, I added a strip of low-fiction UHMW to the under side of the skirts. It too is holding up well.

(sorry - can't attach any photos while at work)

RV-6 N601SC
Dayton, Ohio

Sideskirt notes

n601sc said:

Rick,

After 112 hours, I remain very happy with my slider arrangement that is very similar to yours. It provides a very good seal with no discernible leakage in any flight regime. The only downside is the canopy is a little stiff to open about half way back as the skirts flex around the widest portion of the fuselage; no surprise.

I elected to add a .020" "catch plate" to the lower portion of the windscreen fairing to allow the leading edge of the canopy skirt to tuck-under that last 3/8 (or so) of travel. The aluminum catch-plate was fiberglassed in-place and has not (yet) proven to be a problem. It's a little more durable than just fiberglass.

Also, instead of welding tabs to the lower canopy rails to hold the skirt in-place, I used the RV-9 z-bend stiffener and just drilled and pop-riveted it into the canopy lower tube rail and the skirt. I recollect using the a hole-locator quite a bit during this operation.

Lastly, I added a strip of low-fiction UHMW to the under side of the skirts. It too is holding up well.

(sorry - can't attach any photos while at work)

RV-6 N601SC
Dayton, Ohio

Click to expand...

I too used the Z type stiffener arrangement (with the many optional lightening holes added) and works out just fine. Luckily, my canopy experiences little binding thoughout its range of travel, but I gotta remember to duck my head slightly when closing the canopy with the headsets on! Excellent idea about using aluminum "catch plates" bonded to the fiberglass. It did not occur to me at the time but makes perfect sense. I'l likely bond some aluminum stock under my fiberglass fairing with proseal thus insuring some improved durability in this area over the long term. Glad to hear you validate the UHMW tape application and after 112 hours seems to work as anticipated. Thanks for the tip!

Rick Galati RV-6A "Darla"