I have tried bonding two cowling halves with Bondo. There is quit an open seam between the two halves (perhaps as much as 1/32 of an inch. The Bondo that I'm using isn't sealing the area very well. Yes, I have done exactly what the instructions have stated.
My question to those with lots of experience is, can I do well by using 30 minute epoxy mixed with micro balloons? Won't that work just as well?
I'm all for trying this, but would sure welcome any comments that may prevent me from making a grave mistake. (Like ruining the cowling and having to put out the bucks for another two halves of cowling).
Thank you

What cowling is this? And what kind of materials are we looking at.

This is a large plastic cowling that came with the L-19 Bird Dog that I purchased from Jack Stafford Models.

Bondo is not the right material to use for this type of application.

I would take some heavy fiberglass cloth and epoxy on the inside of the cowl to join the halfs.

a

I failed to mention that I "did" put fiberglass cloth on the inside to hold the halves together. However, the seams still have a slight open space and I want to fill it in to hold it better and at the same time give it a real nice paint job so as not to look so obvious to a horrible job at putting the halves together.

OK - then I would try to fill the gap with a mixture of Expoy and microballoons

m

Not sure, but the plastic is probably ABS, so the epoxy will not adhere well to the plastic. Don't use the Bondo as an adhesive, but it should work as a filler (recommended by Great Planes in fact). Another method I've had succes with is to save the pieces of ABS that are trimmed off when cutting out the cowl pieces. Dissolve them in PVC Pipe cleaner (its acetone and MEK). Don't use a lot of solvent. You want a thick paste. Then spread that thick past over the seam with a popsicle stick. Allow it to stand for a couple days while the solven evaporates. Then sand it smooth. The solvent will cause the plastic cowl to become one with the filler. Just don't put it on to thick.

Brad

These solvents will likely melt the cowl; be very carefull.

When I put together the cowling for the TF Arrow it was 3 pieces that I used fiberglass mesh and 30 minute epoxy on the inside to hold everthing together. I had seams and a few small gaps. I then came back and use bondo on the outside. Very thin layers with wet sanding in between. It was time comsuming but it came out really nice. This picture may not be good enough to tell but we will give it a try. Good luck
chopper man

i would use the bondo if gaps are wide and epoxey if they are only under 1/16.bondo is easy to work.you will need to sand the plastic rough either way you choose to get the bondo/epoxey to adhere good.if you use bondo wet sand like was said here it that makes it nice and slick