Frame dimensions for sikaflex canopy

So I am at that point where most of my building consists of staring at the airplane trying to decide how to do stuff. I have looked at a lot of sikaflex writeups but still not sure about some parts.

My question is whether I should alter the frame dimensions at all to account for the 1/8" gap between frame and canopy due to the sikaflex joint. For example, the plans specify 7/32" from edge of roll bar base to edge of canopy deck. Should I increase this at all (bring the roll bar bases inboard) to account for that sikaflex gap? It seems like 7/32" on each side would allow enough for the sika (4/32) and canopy (3/32?), if the goal is to have the canopy flush with the side skin.

I'd love any input from anybody who has done this and whether they deviated from the stock dimensions at all. Thanks!

Chris

Chris., I had to narrow my tipper canopy bow by a 1/4". I wasn't satisfied having to live with an 1/8" hanging over both sides of the fuse.
So ya, your canopy width should include the plexi thinkness as well as your sika joint thickness. Btw: you HAVE TO deviate from
the stock dimensions if you go with the Sika method.

Thanks Lorne. This will get interesting as I already have to find a way to get my roll bar 1/4" narrower as is. About to go buy a huge ratchet strap.

Chris

The ratchet strap worked great. Just to check my math before I move on, I measured the canopy at 5/32" thick. Added to 1/8" (4/32) for sikaflex thickness, this places the roll bar 9/32" inboard of the side skin. Does this sound right or am I missing something?

Chris

Chris,

I'm at the same point and wondering the same things. I see some people don't put in that 1/8" gap. Also trying to figure out how much the canopy causes the frame to pull out. I will be watching.

I have been doing more research, and have now seen several logs and threads where people use the 1/8" gap at the top and sides of the canopy rails / roll bar, but taper this down to a very small gap at the sides. This allows using stock dimensions, and what looks like a very neat installation. This log https://picasaweb.google.com/n622wr/GluingMySliderCanopy# and this one http://www.rouault.us/ are examples of what look to be this method. I believe Bruce Hill did similar on his tip-up. The skin will hold the canopy against the roll bar at the bottom, and the skirt will do the same on the slider portion, so I wouldn't be as worried about the 1/8" thickness...

Right now I am planning to stick with the 7/32" inset, which will still give me 1/16" of sikaflex at the bottom of the roll bar, and use 1/8" spacers farther up. Open to any other comments suggestions!

Chris

I built my canopy frame to the standard dimensions. There is plenty enough "slop" for the Sikaflex bead. You really don't need 1/8" all the way around. The Sikaflex spec's are for allowing a large flat window to expand in a metal frame, like on a ship. The Van's canopy is a bubble shape, so a lot of the expansion is outward and upward. My build log has lots of information about the process I used. My only issue so far has been that Van's calls out a 1/32" gap between the front and rear canopy halves. That isn't enough when you see triple digit temps. That gap will disappear and you will need a bit of space to open the canopy without rubbing on the forward edge of the rear window. I recently sanded down the aft edge of the canopy bubble another 1/32" and it is now much easier to open when it is heat saturated.

Don't gap there!!

I know several that have done Sika. To avoid altering the Roll bar dimensions, simply eliminate the gap where it attaches on the bottom of the front arch. There will be plenty of adhesive on the front and back of the frame at the fillet. From there at approximately 4-6" begin to taper the gap to open it to the desired gap.

If you plan to Sika the side skirts, very little gap is needed. Same with the rear top skirts.

Remember, Sika is extremely aggressive and it's doubtful you will lose any strength by not having any planned gap there.

For the front wind screen, fabricate gap material to space the roll bar and glass to match the slider.