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Beginner Fiberglass Questions

David Carter

Well Known Member
Patron
Not a builder, and zero fiberglass experience, thus the questions.

I have installed an Archer nav antenna in my RV-7 wingtip, and from reading several threads on here, I see that glassing in the floppy part of the antenna seems to be the preferred method to keep it from flopping around.

I initially tried using 3M automotive molding tape, but it did not adhere to the rough fiberglass surface. Now I'm ready to bite the bullet & try my hand at the glass approach.

What should I do to prepare the unfinished fiberglass surface inside the wingtip to ensure that the epoxy will adhere to it?

In this application, can I get by with a single ply of 2" fiberglass cloth tape, or do I need to layup 2 or 3 plys?

Any other tips?

Thanks!
 
Not a builder, and zero fiberglass experience, thus the questions.

I have installed an Archer nav antenna in my RV-7 wingtip, and from reading several threads on here, I see that glassing in the floppy part of the antenna seems to be the preferred method to keep it from flopping around.

I initially tried using 3M automotive molding tape, but it did not adhere to the rough fiberglass surface. Now I'm ready to bite the bullet & try my hand at the glass approach.

What should I do to prepare the unfinished fiberglass surface inside the wingtip to ensure that the epoxy will adhere to it?

In this application, can I get by with a single ply of 2" fiberglass cloth tape, or do I need to layup 2 or 3 plys?

Any other tips?

Thanks!

Not much, just scuff it with sand paper and make sure it is all clean (using astone) or similar.
But be aware, if the plane is painted, you might see the outline of that piece from outside if you look at the area in the correct angle.

Here is an alternative, just use a piece of foam of the right size that jammed on the floppy side of the antenna and against the upper part. My first RV had that for many years without any issues.
 
Or - just mount the antenna on the rib with a piece of light angle (0.032” is fine).

Note - move the antenna aft a little to get it away from potential RFI from your LED NAV/strobes and such. I recommend not following the install instructions that have you route the NAV/Strobe wires along the antenna.

The photo is a homebrew antenna that uses the full wingtip width dimension to get it out away from the wing.

Carl
62-DCAA5-B-BC9-E-4-AFA-B3-E5-12168-CD550-B0.jpg
 
Or - just mount the antenna on the rib with a piece of light angle (0.032” is fine).

Not a bad idea, but I've already riveted the antenna to the inside of the wingtip per the instructions. I wish I had moved it back further from the FlyLEDs The Works lights. The heatsinks on the back come closer to the antenna than I'd like.
 
What should I do to prepare the unfinished fiberglass surface inside the wingtip to ensure that the epoxy will adhere to it?

In this application, can I get by with a single ply of 2" fiberglass cloth tape, or do I need to layup 2 or 3 plys?

Get someone who knows to show you - it is simple!
Scuff until the surface is relatively flat with 60 grit sandpaper a couple of inches either side of the antenna
Vacuum to remove debris (don't wipe with acetone)
Lay up a couple of plies, resin, cloth, wet out, more cloth, wet out then apply tear strip over the top over lapping the edge of the glass by at least 1/2" and with a piece of dry tear strip at the end as a hand hold. Remove tear strip when resin is good and cured.
 
Get someone who knows to show you - it is simple!
Scuff until the surface is relatively flat with 60 grit sandpaper a couple of inches either side of the antenna
Vacuum to remove debris (don't wipe with acetone)
Lay up a couple of plies, resin, cloth, wet out, more cloth, wet out then apply tear strip over the top over lapping the edge of the glass by at least 1/2" and with a piece of dry tear strip at the end as a hand hold. Remove tear strip when resin is good and cured.

Thanks, very helpful!
 
Get someone who knows to show you - it is simple!
Scuff until the surface is relatively flat with 60 grit sandpaper a couple of inches either side of the antenna
Vacuum to remove debris (don't wipe with acetone)
Lay up a couple of plies, resin, cloth, wet out, more cloth, wet out then apply tear strip over the top over lapping the edge of the glass by at least 1/2" and with a piece of dry tear strip at the end as a hand hold. Remove tear strip when resin is good and cured.

I agree with Pete. Don’t use acetone. It can start to dissolve the resin if your wingtip is a polyester based part. Rough it up to give the new epoxy a chance to tooth in. Wetted cloth is a good solution. Another possibility is a structural epoxy adhesive like G-Flex, available at Home Depot, Lowes, and other places. It has a high temperature range, remains slightly flexible, it will wet out fiberglass cloth if you want to do that, and it is compatible with all West Sytem epoxy fillers and structural additivities - because it is a West Systems product. Good part is, it’s easy to mix - equal parts A & B, mix, and just spread it on. It is a thickened structural adhesive. Simply spread it on like peanut butter and let it cure (overnight). It doesn’t make a big mess, and it doesn’t stink.
 
G-flex

I agree with Pete. Don’t use acetone. It can start to dissolve the resin if your wingtip is a polyester based part. Rough it up to give the new epoxy a chance to tooth in. Wetted cloth is a good solution. Another possibility is a structural epoxy adhesive like G-Flex, available at Home Depot, Lowes, and other places. It has a high temperature range, remains slightly flexible, it will wet out fiberglass cloth if you want to do that, and it is compatible with all West Sytem epoxy fillers and structural additivities - because it is a West Systems product. Good part is, it’s easy to mix - equal parts A & B, mix, and just spread it on. It is a thickened structural adhesive. Simply spread it on like peanut butter and let it cure (overnight). It doesn’t make a big mess, and it doesn’t stink.

G-flex is very tenacious stuff. It is mixed one to one by volume but if you mix by weight, the activator is heavier. 1 to .84. Probably wouldn't make any difference though.
Give you an idea how aggressive it is, I recently bonded a couple parts using a piece of waxed glass as a flat surface. I had to break the glass and grind it off. Powerful epoxy. I use it to bond important stuff.
 
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