...i start working on an old kit, and noticed that my epoxies dont make strong bond,and thats after sanding very hard.

could this because the fuse is made out of polyester resin?...is there a way to find out if its epoxy or polyester?


thanx in advance for any info [8D]

Edit by the mod to remove inappropriate [ but funny ] pic.

When you sand the smell is different, but mainly the polyester tends to be harder. Which kit gives a bigger clue?

Dave

Dear Friend George what company is it? it has gel coat outside ,is it hard or not elastic when you press it?Usually the Byron i remember was polyester resin.Only epoxol from neotex can bond strong on this surface!

Hello Argyri

its gellcoat outside ,its "flexible" when pressed so id say elastic .only think that works till now is hysol..


Thanx for the tip Dave,i now remember i read this before somewhere .. will try sniff some mate ,wish me luck

I know this isn't a great way to tell... but along with the above info...

Epoxy will have a "Nutty" smell when sanded. And, polyester will have a "Solvent" or "Vinyl" smell.

We used to be tell by color with greenish fuse being polyester and yellowish fuse being epoxy, but that was a long time ago and don't know if that still holds true.

Hi George
Post a picture of the inside

Ted

You can get good epoxies to stick, no problem. You just have to clean with acetone, sand and clean again with acetone to make sure you get rid of any blush and get enough tooth fro the epoxy to stick - 80 grit paper is what I've used with Hysol and it stayed until the end...

Correct, you have to make a "mechanical" bond. basically have a rough surface to attach, with little to no resin residue.

You guys remember Stabilit? the glue that Yellow Aircraft used to sell for use on their kits? Man that sure smelled strong.

sand it and if it smells like the inside of a boat hull on a hot day or even a auto body shop(bondo smells the same), then its polyester.

Yes, Stabilit express ( a tube with resin and a small pot with powder catalyst), works best with polyester resin.

Chris

If the fuselage uses polyester resin for the lay-up there is something you should know and this is why you can’t get a good bond to it. Polyester resin will not cure to 100 % unless it is in a vacuum or oxygen is removed. You can’t always put a large lay-up in a vacuum so they add styrene to the resin and what this does is float to the surface and form a film to keeps the oxygen out. Styrene is a wax and unless you remove it nothing will stick very well including epoxies designed to bond to polyester. Depending on who made the resin they could have used very little of a lot, so this will need to be removed before you can get a good bond to it. You may need to sand down to expose some of the cloth before the wax is removed. After you get all the styrene off any good epoxy will bond to it, Hysol works great , but I found that West System Six-10 epoxy works better.

George, check VINYLESTER resin.