Why can't I

[koda2]

just prime this d&^% thing? The picture below illustrates the rudder bottom tip I am working on.

It represents my whole fiberglass struggle to date. Nothing has fit well and has required lots of cutting, reglassing, floxing, micro, etc to get the parts to look like they belong on the same airplane.



The rudder bottom didn't fit and the only way was to slip the forward end inside the rudder spar instead of outside. It looks a little dorky at the corners but its mostly out of the airstream. At the same time the bulbous front portion was too wide and it and the rudder skin struck the rear fuselage skin as the rudder swung. I had to cut a fair amount of fuselage and v-stab skin and also narrow the fiberglass by laying up glass on the inside to get the rudder to swing properly. And yes, the spar is straight and I tried evey combination of diffent lengths in the bearings

Finally I got everything looking good and applied a squeege layer of epoxy to cover the whole thing. The result was runs, sags and squeegee marks everywhere. Sanding those off with 400 left holes in the epoxy layer that even hi-fill primer wouldn't hide. What you see is the tip resanded to remove all the hi-fill primer, epoxy coating, any microballoons and most of the gel coat. There probably is some micro fill in places but the whole thing is nice and smooth and only a couple of pinholes in the epoxy-glass area that can be easily filled.

Why can't I just prime this piece and get a decent result? Is adding an expoxy covering necessary? Do I need some kind of UV coating to protect the epoxy? I am going to use PPG Omni epoxy primer and one of the PPG paints.

Dave A.

[lostpilot28]

Yeah, that thing is a PITA. I ended up cutting a large portion of the "front bulbous" part off so that it would fit inside the aft end of the fuselage and swing all the way to each side. I had to re-glass the hole I created and do a LOT of sanding and filling to make it look decent.

Unfortunately, I think most builders have to do the same thing. The only alternative I can think of is to trim more off of the top edge so that it sits a bit higher and gives more clearance.

[Kiwi]

Throw it away and make an aluminium one?

Anyone done this an would like to share their experiences?

[9GT]

After completing a scratch build composite plane a couple years ago, I can tell you that I find the quality of vans glass parts for my -10 are excellent,,,, needing very little work to get them to fit and look good. I like the West System epoxy for finishing mixed with some micro, nice and runny, and just painted on to fill the pin holes. It sands down real EZ and fills the larger holes. Your primer should have no problem filling any that remain.

[AZtailwind]

Originally Posted by Kiwi

Throw it away and make an aluminium one?

was a pain but not that hard- dremmel here and sand there... bingo!
that compound curve at the bottom calls out for glass- not aluminium....
Prime it and move on... FWIW

[DanH]

Originally Posted by koda2

.... the whole thing is nice and smooth and only a couple of pinholes in the epoxy-glass area that can be easily filled.

Why can't I just prime this piece and get a decent result? Is adding an expoxy covering necessary? Do I need some kind of UV coating to protect the epoxy? I am going to use PPG Omni epoxy primer and one of the PPG paints.

Dave, you really don't know what you have until you prime, so yes, fill those "couple of pinholes" and shoot it.

No real need to put an epoxy skim coat on a gelcoat surface. Think of gelcoat as a pre-installed surfacing layer found on glass parts built with polyester resin. It is itself a polyester.....use any of the common polyester surfacing putties to fix defects.

Both epoxy and polyester resins are sensitive to long-term UV exposure. Prime and paint.