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Leading edge of tip-up canopy

Glen P

Active Member
I've attached my tip-up canopy using Sikaflex. My thinking was that I needed to have an area of horizontal plexiglas at the leading edge to give the sika something to bond to. The profile at the centre is something like this:

https://vansairforce.net/community/attachment.php?attachmentid=1003&stc=1&d=1596982637

Now that I'm ready to do the transition from aluminum to plexiglas, I'm looking at Van's take on the profile:

https://vansairforce.net/community/attachment.php?attachmentid=1004&stc=1&d=1596982916

If I sand off some of the plexiglas and add some microballoons, does this profile seem like it would work?

https://vansairforce.net/community/attachment.php?attachmentid=1005&stc=1&d=1596983001
 

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Hi Glen
I bonded my tip up with Sikaflex, and followed the plans for fiberglass layup. Your diagram looks like it might result in less bonding area, and micro has no strength, flox is stronger. A failure at this joint could ruin your whole day

I'm not expert with glass, and didn't have difficulty with the task as laid out in the plans

Cheers
Jay
 
Here is what I have done

Applied a wide and thick sikaflex bead onto the top skin and obviously all other mating surfaces. Then position the canopy where it should be and let it cure for 48 hours. Then build up the coming with sikaflex and sand it down to the desired shape once cured. Then apply a few layers of glass.

Remember that when you use sikaflex the glass layers are merely there to finish off. The sikaflex is holding the canopy.
 
Sikaflex only...

It was a RV8A, so less frontal area, but I attached the windshield with sikaflex. I made a fillet with sika on the inside and up onto the windshield about 3/8ths. Once that was all dry, I used sika on the front and faired it using a cheap coffee saucer from a discount store.

I placed the saucer edge on the boot cowl and the windshield so I could figure out where the edge would fall and used a couple of layers of tape on both surfaces to keep things easy. Then I used the saucer to squeegee the sika on. I pulled the tape as soon as I could, otherwise it tries to pull the sika off. It came out nice.
 
Sika

Can we just use a sikaflex bead and no fiberglass?

7A Slider but still may apply.
I did. Sort of. I bonded the windshield using a bead aplied to the mating area of the top skin. Clamped it to cure then added two insurance clips.
One piece windshield trim was done as a layup. Popped it off, finished it then it was bonded with Sika as well so the edges were fully sealed to the windshield and skin. Windshield is not coming off.
However, just like a car, the Sika can be cut with a Kevlar string.
 
Even with the Sitkaflex adhesive, the glass layers, at a minimum, are desired to prevent microcracking that would imprint though the paint.

Brad
 
I would definitely bevel the front edge. Tape off the area shown on the plans, scuff the plexiglass and aluminum, then do the layups of fiberglass over the front edge. This will give you a much better look, better for paint to not crack as suggested above and provide a nice transition for airflow over the canopy.
If you need more bonding strength, then put another sikaflex bead on the interior side of the plexiglass and top skin.
 
Some pictures might help you

Here is a sequence of pictures that might help you. It is of a canopy I had to replace after a bird strike. I really hope it will help you.

IMG_9321 As it was when it arrived
IMG_9334 After stripping and cleaning most of it
IMG_9348 Sika applied
IMG-9350 Showing the bead of Sika inside
IMG_9372 More Sika outside to for the coaming
IMG_9377 After sanding
IMG_9379 After several layers of glass ans peel ply
IMG_9409 S-Fair applied
IMg_9426 All done except for painting
 

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