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.
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.
Practice on old canopy