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Canopy oversized Holes And Rubber Insert Technique

mfleming

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I have tried searching for more information on the technique of attaching the slider canopy by making oversize holes and using rubber inserts but have not had much luck.

Pau Dye referenced it here

Any Help would be appreciated.

PS: I'm also thinking of Sikaflex but want to thoroughly explore all techniques before deciding.
 
Nothing complex about this, it's actually just oversizing the screw/rivet hole a size or two and then using a piece of small diameter surgical tubing to take up the bit of extra space around the screw/rivet shank. Allows the plexi to float just a bit. I got the idea and help from Matt Burch but a lot of others have done it as well. 500+ hours no cracks.
Hope this helps.
 
Nothing complex about this, it's actually just oversizing the screw/rivet hole a size or two and then using a piece of small diameter surgical tubing to take up the bit of extra space around the screw/rivet shank. Allows the plexi to float just a bit. I got the idea and help from Matt Burch but a lot of others have done it as well. 500+ hours no cracks.
Hope this helps.

Do you use the rivets as specified in the plans? Just wonder if the rivet heads were big enough?
 
I have never used rivets with the tubing. I would think you would have a problem with the rivet collapsing into the rubber. Or if you have metal over it the rivet would collapse the dimple, causing a diver reather than a smooth surface.
 
Do you use the rivets as specified in the plans? Just wonder if the rivet heads were big enough?

I used regular rivets and screws. Also chose to use tinnerman washers, size 4 I believe drilled out to match rivet diameter (thought I might have stuck with size 6 across the front bow). This disperses the force from the rivet head onto a wider plexi surface area. Some have chosen to use a single strip of aluminum across the entirety of the front bow. Serves the same purpose.
 
I have never used rivets with the tubing. I would think you would have a problem with the rivet collapsing into the rubber. Or if you have metal over it the rivet would collapse the dimple, causing a diver reather than a smooth surface.

So did you use screws everywhere rivets were called for? Also How important is the type of rubber tubing?

I'm thinking Tygon clear fuel tubing ¼"OD X ⅛"ID...does this sound right.

I haven't found a description of using enlarged holes with rubber tubing or a description of using screws instead of rivets anywhere.
 
I would think Tyson tubing would be to stif. Surgical tubing is ez get cheap, and cuts with just a ciders. Just cut up a bunch the thickness of the plexus. Overdose the hole to make a tight fit for the tubing. Tighten the screws to Minimum torque. You should be golden.
 
Canopy attachment with silicone tubing inserts

I have tried searching for more information on the technique of attaching the slider canopy by making oversize holes and using rubber inserts but have not had much luck.

Pau Dye referenced it here

Any Help would be appreciated.

PS: I'm also thinking of Sikaflex but want to thoroughly explore all techniques before deciding.

Copy and paste from 2012.
Danny King's Avatar
Danny King Danny King is online now

Join Date: Dec 2004
Location: Southlake, Texas
Posts: 614
Default Canopy Replacement
Last winter, my RV-8's canopy cracked while sitting motionless in front of Jay Pratt's RV Central the very day the RV-1 was getting it's pink slip. This is not the first time this has happened to me. Several other local RV-8 builders have had their canopies crack while sitting in the hanger on a cold night. There must be a better way to do this then what the plans call for. The following is a procedure Paul Dye and I came up with to address this problem.


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PROCEDURE FOR REPLACING CANOPY BY MIKE KING as told to Craig Taylor, May 1, 2012

1. Removal of Canopy from canopy frame

a. Remove only the upper row of rivets on the canopy skirt. Leave the canopy skirt attached at the bottom and ribs of the canopy frame unless it is desired to replace or repair the skirt.

b. Start from the aft end of the canopy

c. Remove paint from each AACQ 4-4 rivet head to locate the mandrill that remains from the original pull rivet.

d. Using a small diameter punch, drive the mandrills into the canopy frame tubing.

e. Using a 1/8” drill, remove the head of the rivets

f. Using a 1/8” punch and a very small hammer, drive the rivet body into the canopy frame tubing

g. After all rivets retaining the canopy are removed, lift the old canopy off the frame.



2. Match, Mark, and cut New Canopy

a. Remove any shade track, tape, decals and so forth from old canopy.

b. Clean the outside of the old canopy perfectly.

c. Remove the protective film from the inside of the new canopy and clean perfectly.

d. Nest the old canopy into the new canopy and move around till achieving the best fit.

e. Tape the two canopies together to hold that location.

f. Using a fine magic marker (“Sharpie”) trace the outline of the old canopy onto the new canopy. This will be the reference line for cutting the new canopy to shape. This will also provide a canopy that will slightly overlap the canopy frame tube, allowing for final fitting and for finishing the edge.

g. Remove the attaching tape and re-nest the two canopies to be sure that there was no slippage during marking

h. Cut the canopy along the reference line using a Dremel tool with a 1 1/2” diamond wheel.



3. Prepare the freshly cut canopy edge

a. Sand the edge to smooth out imperfections and remove any notches created by the cutting process. Start with 100 grit sandpaper and work up to 180 grit, rounding the edge.

b. Be sure not to sand the edge beyond the area to be covered by the canopy skirt.

c. The edge preparation should shorten the edge of the canopy so that it will not overlap the bottom of the canopy frame tube. (Nesting the old canopy into the new canopy provides the trim excess.)

d. Test fit the canopy to the frame to be sure that there is no area of interference. The canopy should nest tightly around the front canopy frame hoop and not bottom out when slipped between the canopy skirt and the horizontal frame tube.

e. Continue to test fit and sand the edge until the canopy fits all the way around the canopy frame.



4. Fit Forward Edge of Canopy to Windshield

a. Be sure that the canopy remains in the fitted position on the canopy frame as the canopy is fitted to the windshield. To do this, use a Sharpie to mark the position of the canopy on the canopy frame. Mark the location of the second hole from the forward end of both horizontal canopy tubes on the canopy (the first hole will be covered by the windshield cap when the canopy is closed).

b. Close the canopy, and gently attempt to lock the canopy handle.

c. If the canopy will not lock in place easily, check for interference between the canopy and windshield.

d. Remove material and re-round the forward edge of the canopy until the canopy can be closed and locked without slippage of the canopy as referenced by the Sharpie mark on the second rivet holes (Step 4.a.).

e. With the canopy in place and the canopy handle in the locked position, move the canopy slightly fore and aft, and left to right to be sure it is settled on the frame.

Note: The forward edge of the canopy will end up approximately even with the front side of the canopy bow.

This completes the fitting of the canopy to the canopy frame.

5. Match Drill the Canopy to Canopy Frame.

a. Open the canopy; using several spring clamps, clamp the skirt to the upper canopy horizontal rail with the canopy sandwiched between the skirt and rail.

b. Close the canopy and lock the canopy handle; verify that the canopy is settled in position by checking the Sharpie marks on the canopy against the second hole in the frame rail.

c. Using a 1/8” Plexiglas drill and starting at the rear center of the canopy, match drill the canopy to the frame rail using the rivet holes in the canopy skirt as a guide.

d. After each hole is drilled secure the canopy and skirt using Clecos.

e. Work symmetrically from the rear of the canopy. EG - drill one hole to the right of center, then one to the left of center, then one to the right of center working forward along the canopy frame rail. Check frequently to see that the “match marks” on the second hold from the front are still lined up. (Step 4.a.). Note: if the match marks move, some rework of the canopy-to-windshield fit will be required.

f. Finally, match drill the holes from the top to the bottom of the front canopy frame bow, again securing with Clecos as the work progresses.

This completes the match drilling of canopy to frame.

6. Enlarge Canopy holes

a. Remove Clecos and remove canopy from the canopy frame.

b. Place the canopy on saw horses to support it uniformly.

c. For each hole to be enlarged, clamp a piece of wood trim (approximately 1” by ¼” x 3”) under the hole to be enlarged.

d. Using a ¼” Plexiglas drill, enlarge each of the holes to ¼”. Drill into the wood till the point of the drill is completely through the Plexiglas, but not through the wood.

e. Remove the wood trim, and chamfer each hole lightly (after each hole drilled) with a deburring tool or a countersink tool operated manually.

Note: Do not drill into the same hole in the wood trim when drilling subsequent holes.

7. Fit Rubber Grommets

a. Rubber grommets are made from model airplane silicone rubber fuel line, 1/8” ID, ¼” OD. This is available at most hobby stores.

b. Since the canopy thickness varies, cut the tubing in lengths equal to the thickness of the canopy for each individual hole.

c. Secure the grommets into the ¼” holes with Super Glue (cyanoacrylate).



8. Attach Canopy to Canopy Frame

a. Install the canopy on the canopy frame, and align the rivet holes with the canopy skirt and frame.

b. Secure the canopy and skirt to the canopy frame using Clecos.

c. Again starting at the aft center, install the AACQ 4-4 rivets, working symmetrically forward left and right.

d. Starting at the top of the canopy front hoop and working symmetrically down the canopy front hoop, install the AACQ4-4 rivets holding the canopy to the front hoop.

e. Recheck the fit of the canopy leading edge with the windshield and adjust as necessary.
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Practice on old canopy
http://i50.tinypic.com/34ipk7c.jpg

http://i47.tinypic.com/2hrfwwn.jpg

http://i47.tinypic.com/mw9ssw.jpg
__________________
Danny King
Beautiful Doll 80434 TT 1675 hours
I0360 A1B6 200 HP
Christen Inverted Oil
First Flight 12 July 2000
VAF Dues current for 2020
Last edited by DeltaRomeo : 06-08-2012 at 08:25 AM.
 
I'm not really sure why you need anything in the hole, over size holes, CS, then using screws and tinerman style washers tighten the screws just barely enough to hold the canopy on.
 
I'm not really sure why you need anything in the hole, over size holes, CS, then using screws and tinerman style washers tighten the screws just barely enough to hold the canopy on.

you can also add some VC-3 thread lock to the screws. VC-3 will not harm the canopy plastic.
 
No inserts

If you have the patience (doesn't take all that long with a 1/8" dremel bit), don't oversize the holes.

Expansion/contraction is mainly fore-aft.

Pick a stationary reference point. Then gradually increase the holes to a slot, bigger and bigger slots the further away from the reference point.

Example from my RV-4:
Alum: 12
Acrylic: 38
Diff: 26 micro inch/F
Elongate Slot width Elongate Slot width Ref temp Min temp Max temp
Position inches 160 80 -10 150
2.60E-05 Inch Inch mm mm More aft More forward
3 0.012 0.137 0.3 3.5 1.9 1.6
6 0.025 0.150 0.6 3.8 2.0 1.8
9 0.037 0.162 1.0 4.1 2.2 1.9
12 0.050 0.175 1.3 4.4 2.4 2.1
15 0.062 0.187 1.6 4.8 2.5 2.2
18 0.075 0.200 1.9 5.1 2.7 2.4
21 0.087 0.212 2.2 5.4 2.9 2.5
24 0.100 0.225 2.5 5.7 3.0 2.7
27 0.112 0.237 2.9 6.0 3.2 2.8
30 0.125 0.250 3.2 6.3 3.4 3.0
33 0.137 0.262 3.5 6.7 3.6 3.1
36 0.150 0.275 3.8 7.0 3.7 3.3
39 0.162 0.287 4.1 7.3 3.9 3.4
42 0.175 0.300 4.4 7.6 4.1 3.6
45 0.187 0.312 4.8 7.9 4.2 3.7
48 0.200 0.325 5.1 8.2 4.4 3.8
51 0.212 0.337 5.4 8.6 4.6 4.0
54 0.225 0.350 5.7 8.9 4.7 4.1
57 0.237 0.362 6.0 9.2 4.9 4.3
60 0.250 0.375 6.3 9.5 5.1 4.4
63 0.262 0.387 6.7 9.8 5.2 4.6
66 0.275 0.400 7.0 10.1 5.4 4.7
69 0.287 0.412 7.3 10.5 5.6 4.9
72 0.300 0.425 7.6 10.8 5.8 5.0
75 0.312 0.437 7.9 11.1 5.9 5.2
78 0.324 0.449 8.2 11.4 6.1 5.3
81 0.337 0.462 8.6 11.7 6.3 5.5
84 0.349 0.474 8.9 12.1 6.4 5.6

I can e-mail you the spreadsheet if you want.

Oh, and I found it easy to countersink the plexi for the dimpled side skins. Just slide the 1/8" microstop countersink back and forth in the slots.

Finn
 
Last edited:
...

PS: I'm also thinking of Sikaflex but want to thoroughly explore all techniques before deciding.

Hi Michael,
I just finished glueing the canopy with SIKA.
It is very easy and clean and I can’t imagine going the route of holes, screws and Rivets.
B.t.w. Did we meet in 2017 during the Vans factory tour?
 
No sweat: Bennair; Dunnatt

We have been using the oversize hole process on the Rocket canopies since 1994 or so. Many aircraft used that exact process too.

Drill the hole to match 1/4” OD fuel line, and cut the line to match the thickness of the plexi. Use tinnerrman washers and #6 screws to hold things in place - don’t tighten the screws totally. If need be, you can use a slightly longer piece of tubing as a shim if the plexi does not quite lay down on the tubing

Don’t use the attach screws to force the plexi to conform to the tubing if the plexi does not quite follow the tubing shape (under 1/16” or so), or as it was with clecoes.

Drill the plexi with a step-drill on low RPM.

Build up your normal fiberglass fairing between the windshield and slider, and along the aft & side skirts.

Use household exterior caulk of your color choice to waterproof the slider plexi along the side and aft fairings; attach with the suggested fasteners. Before final assy, lay a length of masking tape along the metal fairings to keep the caulk off of the exterior
Plexi.

Do not use silicon caulk - just the inexpensive water based stuff.

The caulk is amazing regarding how long it lasts. Never did hear of anything coming loose.

I have never heard of a Rocket canopy cracking when this process is used.
 
Hi Michael,
I just finished glueing the canopy with SIKA.
It is very easy and clean and I can’t imagine going the route of holes, screws and Rivets.
B.t.w. Did we meet in 2017 during the Vans factory tour?

YES...:D I remember meeting at Van’s... glad to see you are building....good luck.
 
I would like to request pictures of this grommet technique. I read Danny King post but the pictures on tinypic are no longer there.

Thanks.
 
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