[Berchmans]

I have done a lot of reading about sikaflex bonding of the canopy to the frame. With care it appears that the material is very flexible for installation, strong, and sandable once set. My question, has anyone done a 100% installation using sikaflex? By this I mean have you bonded the wind screen to the forward skin without using fiberglass but formed a fillet that was sanded to fit the skin/wind screen contour? It seems outwardly that this is a viable option...

 

[judoka5051]

That's a great idea!

I'm almost to that point myself. If you don't get any feedback and decide to break new ground, please keep the forum informed. I'm about 3 months from that project.

Lance

 

[flion]

I was assured that Sika was sandable and paintable, so I proceeded on that assumption. I found it difficult to form the fillet satisfactorily, so I built it up more than I .wanted and waited for it to cure. Then I tried sanding it. It does sand, using a coarse grit, but everything I tried to use clogged up. However, it was worth the effort because it came out fairly smooth and has been working, unpainted, on my RV-6A since around Sept. 2008. I understand that you have to paint, or at least prime, with acrylic to get it to stick; I thought if that proved difficult I might throw a single bid layer on there for paint to stick to. Someday. When I paint. Which means I have to stop flying it first. Hmmm.

 

[sjhurlbut]

Tough

I've Sikaflexed 2 RV canopies so far - great stuff.

As far as no fairings on the front - not sure its possible. The windscreen will fit well if you spend the time but it won't be perfect. I put Sikaflex under a fairing. I also like the air flow to get a good deflection over the canopy. Sikaflex only will have a transition thats at a larger angle.

Also reference getting a nice fillet. Put the Sikaflex on no more than ~12" at a time. Then create the fillet before continuing. If you wait until the end, the initial part will already be like rubber and will not fillet well.

 

[molson309]

I tried this and ultimately ended up putting a couple bid of glass over the Sikaflex. I could never sand it smooth enough that I could consider painting it, and I was also concerned that the paint wouldn't stick or could crack due to the flexible nature of the Sika. It wasn't a lot of trouble to glass over it and I like the finished result.

Mark Olson RV-7A F1-EVO

 

[SHIPCHIEF]

I'm not flying yet, but I did plan on the 100% SIKA application.
I'm a slow builder, and my primitive SIKA installation shows it.
The inside beads are rough where you can see them as a pilot or passenger. I didn't know about, (or think up) that you can scupt the exposed bead into a smooth fillet. Most of all, you have to work fast once it's applied. It will skin over quickly, even faster if it's humid.
I planned to have no exterior fillet around the windshield, but right now I don't think the forward edge of the RV-8 skirt would look right without some fillet to butt up against or possibly fit under. I might go with a small fiberglass lower windshield fillet.
Not over the top of the roll bar; I worked hard to get a nice clean fit there, and I like it that way.

 

[DGlaeser]

x2

I tried this and ultimately ended up putting a couple bid of glass over the Sikaflex. I could never sand it smooth enough that I could consider painting it, and I was also concerned that the paint wouldn't stick or could crack due to the flexible nature of the Sika. It wasn't a lot of trouble to glass over it and I like the finished result.
Mark Olson RV-7A F1-EVO

That is exactly what I did as well...

 

[jwyatt]

Mark, Dennis --
Was there any special prep you found required to get the fiberglass layup to bond with the Sika? Just sand it down well and overlap the layup onto the plexi and aluminum?

I built up a good thickness of Sika with the plan to sand it down into a fairing, but it sounds like that's been tried & abandoned by you who have gone before...I may as well save the trouble and bite the fiberglass bullet.

 

[DGlaeser]

Give it a shot...

Mark, Dennis --
Was there any special prep you found required to get the fiberglass layup to bond with the Sika? Just sand it down well and overlap the layup onto the plexi and aluminum?
I built up a good thickness of Sika with the plan to sand it down into a fairing, but it sounds like that's been tried & abandoned by you who have gone before...I may as well save the trouble and bite the fiberglass bullet.

I used a large radius form (a can) to get a nice fillet with the Sika flush with the plexi and faired to the aluminum. I always planned to add a couple of layers of deck cloth, so I never tried to sand and paint the forward fillet. I did no special prep, just sand and lay on the cloth strips. I had put on the multi layers of electrical tape on the plexi per the Vans instructions.
Give the sand and paint method a try. If it doesn't work you still can sand more and lay on the glass cloth.