Sikaflex Bonding of Canopy

[jaradtke]

Can anyone provide the spring back measurements they experienced when using Sikaflex to bond the canopy to the slider frame?
I’ve read it approximately ½”, but this seems to be with the pulled rivets and screw method. Does the continuous bond with Sikaflex reduce the spring back?

 

[wirejock]

Spring back

Can anyone provide the spring back measurements they experienced when using Sikaflex to bond the canopy to the slider frame?
I’ve read it approximately ½”, but this seems to be with the pulled rivets and screw method. Does the continuous bond with Sikaflex reduce the spring back?

1/2" is conservative. Every canopy is a little different spring rate. I recommend builders get it as close as comfortable then clamp the canopy in the bow and take measurements across the forward and aft ends. Compare to the fuse and adjust the bow accordingly. Too much and the bow will hit the aft skin. Too little and your canopy has big hips like mine. Thankfully, judicuous fiberglass work hides a multitude of Twinkies!

 

[jaradtke]

How much spring back did you have? I didn't see it mentioned in your KP article or website.

 

[wirejock]

Spring back

How much spring back did you have? I didn't see it mentioned in your KP article or website.

I set the bow for 1/2" total. 1/4" each side.
Even after measuring over and over to confirm, the aft end ended up a tiny bit too wide. The forward end is ok because the rollers hold it in the tracks. She looks like she has muffin top hips. Too much junk in the trunk. Don't tell her. She's very sensitive about it.

 

[nohoflyer]

Is there a comprehensive article on this technique? I’m getting close and I don’t want to drill the canopy in for obvious reasons.

 

[wirejock]

Sika article

Is there a comprehensive article on this technique? I’m getting close and I don’t want to drill the canopy in for obvious reasons.

I don't know about comprehensive. I did write a Kitplanes article or two. Check my blog (below) for the links

 

[Desert Rat]

Can anyone provide the spring back measurements they experienced when using Sikaflex to bond the canopy to the slider frame?
I’ve read it approximately ½”, but this seems to be with the pulled rivets and screw method. Does the continuous bond with Sikaflex reduce the spring back?

There's still springback. The shape of the frame and where you position the canopy fore/aft of the frame are variables but on mine no matter how much I tweaked the position the canopy was still slightly wider than the frame. Even with sika you still have to clamp it all together and the canopy causes the frame to spread out slightly.

When I started fitting mine, I measured the frame, clamped the canopy to it and remeasured. My spread grew by 3/8", so I took it back apart and manipulated the frame another 3/8" narrower then rechecked. It looked good at that point so I glued it together. came out just about perfect.

FYI- the fwd rollers have a bit of lateral play in the tracks so if your off in your estimate by 1/8" or so it will still work, albeit maybe not as smoothly as if they weren't rubbing on the sides of the track.

 

[rapid_ascent]

I'm just getting back around to gluing mine. It got too cold last year for me to feel comfortable making the cut. Then I moved on to other things. My canopy has been cut for a bit now so I'm past that. Now I'm reviewing all of this Sikaflex information and I think I have figured most of it out. I reread Larry's article a few times too.

One thing I'm not 100% sure of is the masking process. I just received my fineline 218 tape so I'm ready to start that. I'm thinking I put the canopy frame back in the canopy and mark the areas where I will be bonding plus some space for the fillet of adhesive. Then I'm going to cut away the protective plastic a little further than those lines. Then I'll use the frame again to mask off where the edges will come to applying the tape directly onto the canopy and sealing the edge of the protective plastic. Is that basically the way it is done? Any further details could be helpful.

 

[wirejock]

Masking

I'm just getting back around to gluing mine. It got too cold last year for me to feel comfortable making the cut. Then I moved on to other things. My canopy has been cut for a bit now so I'm past that. Now I'm reviewing all of this Sikaflex information and I think I have figured most of it out. I reread Larry's article a few times too.

One thing I'm not 100% sure of is the masking process. I just received my fineline 218 tape so I'm ready to start that. I'm thinking I put the canopy frame back in the canopy and mark the areas where I will be bonding plus some space for the fillet of adhesive. Then I'm going to cut away the protective plastic a little further than those lines. Then I'll use the frame again to mask off where the edges will come to applying the tape directly onto the canopy and sealing the edge of the protective plastic. Is that basically the way it is done? Any further details could be helpful.

Pretty much. If you still have the plastic on the outside, make all your marks on the outside. I used a uniform 1" wide strip for the primer. Tape is your friend. Lay down the 218 first. Don't stretch it. Just press it down. Apply black electrical tape overlapping that then painters tape to hold the mask or to cover any exposed plexi. You don't want anything exposed except the area where the primer will be applied. It's very thin and will drip and run everywhere.

Make some test coupons out of scrap with lines of the same tape. Apply the same products at the same time as the canopy. When the job is done use them to test when to pull the tape. Pull it too early and it makes a mess. Too late and it won't come off. When you get a perfect tape removed, pull the tape on the canopy. I'm guessing about 12-24 hours.

 

[N16KY]

I got the frame as perfect as possible on the fuselage including rear pin/pin block fit.
Took it off and measured the width front and back.
Clamped the canopy on and measured front and back.
Very close to 1/2 inch wider.
Bent the frame 1/2 inch narrower.
Sika flexed canopy to frame off of fuselage.

It came out nice and a little adjusting of roller spacers has the canopy rolling slowly backward on it's own (it's a 7).