Fiberglass Parts

[Steve W]

Sometimes I really have to bite my tongue but this time I have to relate what I'm going through with some fiberglass parts I purchased about two years ago. I didn't realize how bad they were until I started to shape and finish them recently. Their whole surfaces need to be puttied or sealed some how. I have tried a full bodied primer/filler but absolutely no luck after 7 coats with sanding in between. This is all and above all the voids, bubbles, and imperfections already puttied. Some of those are to be expected. I will have to putty the entire nose bowl as it's now covered with primer and will, after two days of spot filling, try and spray a coat of thinned epoxy in hopes of filling the fabric weave on the wing tips. If anyone is wanting to know where I got the parts, PM me, otherwise I'll keep that to myself.

Steve W
P203

[Archer39J]

Granted I have exactly zero experience with filling and fairing fiberglass. But from what I've read I thought filling pinholes was a rite of passage when making airplane parts. Are these parts particularly egregious? My CF wingtips look like they have plenty of pinholes but I figured I'd be addressing that when it came time to paint.

[jaredyates]

For parts that are not gel coated, this has always been my experience. Have you found otherwise?

[Bdflies]

I feel your pain! Actually, I felt your pain. I don’t remember how many days I spent filling, sanding, priming, repeat.... and my parts aren’t perfect. I used featherfill on some of the parts, with some success. Otherwise, stock up on spot putty and sandpaper!

Bill

[whee]

I'm lazy. Local vinyl shop said most of the voids won't show though a vinyl wrap. Obviously I'm not trying to with any airshow awards...

[Battson]

For parts that are not gel coated, this has always been my experience. Have you found otherwise?

+1

This is par for the course when buying parts without a gel coat.

Both my nose bowls supplied by BH Aircraft were gel coated and exceptionally easy to finish. Just assemble, prime, and paint.

Making parts from scratch, wingtips for example, took me 14 solid hours of sanding (not counting the filling). All I would say is, use a soft filler, not a hard-set resin filler. Much easier to sand. I used a combination of both.

[Steve W]

From Jared "For parts that are not gel coated, this has always been my experience. Have you found otherwise?"

Yes I have. A little more resin and saturating the fabric eliminates what I have here. The fabric is almost a fuzzy nap because it wasn't saturated. Like I said, a little more resin and a few more minutes rolling the resin into the weave eliminates this. If it's not vacuum formed, then yes, there will be voids around a tight radius because the fabric will try to straighten creating a bubble.
I just laid a thinned coat of epoxy on both wing tips and I think a second will close the fabric weave. As far as for the cowl, I will have to putty the whole thing.

[svyolo]

Dewaxing to get the mold release off (and contaminants that come to the surface) is really important before you do anything. If the resin was a polyester laminating resin it can have a nasty surface to it as well. I can't remember what it is called. Some type of mold release was used (PVA?) and it needs to come off first or you will never get pinholes and such to seal. They will just keep coming back to the surface.

[Steve W]

Just an update. I ended up having to completely putty the whole nose bowl. You can see from the picture before the putty was applied that the weave would not fill in with the primer/filler coats. Two hours of sanding and it looks pretty good. For the wing tips, I sanded the first thinned epoxy coat fairly smooth with 180 paper after letting it dry over night. I brushed on another thinned coat of epoxy and let dry. Today, I was able to get the tips smooth with most imperfections filled. Two coats of primer/filler and now to spot putty the voids. 5 days of work into these three parts and with one more, they might be suitable for the final priming.

[S Lathrop]

There is a product I have used frequently called "Feather Fill" This is a 2 part primer product that is like spraying Bondo. I have used it to cover wood and foam to make molds and bucks for race car body work. I also use it as the first step in refinishing damaged parts that had a lot of fiberglass work repair. Feather Fill sands easily and is followed with a good sanding primer.

This is way easier than putty but is is a sprayed product and requires good protection for the user when it is sprayed.

I will have the same issues with my nose bowl.

[Steve W]

I should have foreseen the problem and not tried to fill the weave with the primer/filler but afterwards, I had no choice but to putty. I cleaned and scrubbed the bowl with acetone to remove the mold release but because of the holes, I think it was still evident and would not allow the wet to penetrate. Anyways, just a heads up for anyone walking down the same path.