Is it normal for Polyester Resin to get so hot as it cures? The 1oz mixing cup I used got so hot I couldn't even keep my fingers on it. I'm afraid of what this will do to the fuselage when I glue in the formers.

Richie

That is one problem with the Polyester Resins, they get very hot. Instead try something like West Systems Epoxy or even some of the ZAP products.

JR Gautreaux

Yes it will get that hot in the cup when it is in mass quantities. It will not harm your fuse due to the fact that there is little heat felt when spread out over a flat area like fuse and formers. Epoxy will do the same thing in a container.

That makes a lot of sense. I certainly don't like the idea of investing even more so into another resin/epoxy although, of course, I would provided what I already have won't cut the mustard. Thanks Jeff.

Richie

Richie,

Careful with poleyester resin use... I used to use it for glassing wings and found that it will not cure when applied over epoxy. Epoxy, however, WILL cure over poleyester resin. Must be some chemical reason, who knows.

For what it's worth, BVM Aeropoxy is some of the best stuff you'll ever use to put formers in a fuse. No drip, no mess, well worth the initial price.

Bob

I am currently using Hysol 9462 by loctite. Comes in a dual tube setup and you use a guns with it to get it out. They have these little tips that mix the agents together as you squeeze it out the tube. Awesome stuff, so easy to use and so strong!!

I didn't see anyone else discuss this aspect of the subject, so I will.

Unlike epoxy, which requires a more exacting mixture in order to properly cure, you can vary the cure times (and resulting pot life/temps) of polyester resin by varying the amount of catalyst you add to it. Less catalyst equals slower cures with longer pot life and lower temps and more catalyst equals faster cure times with shorter pot life and higher temps.

Same for bondo body filler since it uses polyester resin as it's base.

Dan

Thanks Dan. I had a feeling that might be the case but I wasn't entirely sure. Time to start experimenting!!!

Richie

~S~ all

I work with polyester resin for 20 years without any problem. You have probably put to much catalys in your resin.
Polyester will cure from .8% to 5% . With .8% i have in a coolday 45 minutes to work . but a good rule of tumb to mix catalys and resin
are 6 drops of catalys for 30 cc or 1 onzes of resin.[8D]. D`ont mix lots of resin at the same time , to glue former in fuselage try 30 cc batch
this way you can work slowly without rushing anything.

Good luck with your project

That's EXACTLY what I did. I started with a small batch in a 1 oz cup and put exactly 6 drops of catalyst in it. I like that it's much thinner than epoxy which makes it easier to work with, but I felt it cured too fast. I will try 5 drops next and see how that works out and so on, till I get it right. I know, not too little or it won't cure as well...or will it? Thanks

Richie

I was hoping to glass my wings with this stuff and i'm glad I chose to test it on foam first!!! IT EATS RIGHT THRU IT!!! Any suggestions on how to glass wings with polyester resin? The root of the wing, where it meets with the fuse, is exposed foam. This area will be glued to the fuse later on. Thanks

Richie

TCMan, we used to use polyseter resin to glass our sheeted foam wings long before the thin finishing and laminating epoxies became readily available. I have used polyester to do probably 100+ wing panels over the years. You just need to make sure there are no voids in your sheeting seams, pinholes, etc. where the resin can leak through. Also need to be extra-careful around tips and the root (consider adding a 1/16" balsa root rib as protection). Don't pour the resin on, just lightly brush it and sqeegee the excess around, being particularly careful around the edges and openings.

Having said that, epoxy is far better (stronger) and easier to work with. Why not just spend $10 or so and get some Z-Poxy epoxy laminating resin? One kit will easily do a decent sized wing and tail. West Systems is even better but more costly and not as user-friendly (i.e. 5-1 mixing ratio).

Sound like you have not glassed wings before? If not, you may want to do a search on RCU, I am sure there are some good tips here.

Barry

Barry, thanks for your response and you're right!! I've never glassed wings before. I was considering the idea of adding the balsa rib at the wing root, but i'm afraid that the bond between the wing and the fuse might not come out as strong as gluing directly at the foam. Am I wrong? Also, when adding the leading and trailing edge balsa stock, I held them in place with pins. In other words, more areas for the polyester resin to get in to the foam. I'm sure I could seal them with some CA but I think it would be best for me to just use epoxy. I have some 30 minute epoxy on hand but it only gives me 10 mins of working time. I'm a go out and get something slower. BTW...when glassing wings, do I glass the ENTIRE WING (minus the foam root of course)? In other words, should I go over the trailing edge stock as well? Thanks

Richie

Go with Z-poxy it is foolproof. Polyester is great for fuselage, cowls, etc. If you want to sheet wings, you need to be really careful that you have a good seal on the sheeting otherwise the resin will destroy the foam. Polyester is very temprature sensitive, if it is too warm, it cures quickly, if it is too cold, it remains tacky. If you put it on too thin, it stays tacky. Pot life is really short when you mix fairly large quantities with a fair amount of hardner.

By the way, Z-poxy sands a lot easier than polyester.

Good luck

Zane

Z-Poxy....SOLD!!!! Thanks Zane.

TCMan - No worries, I was where you are once!

Do a search on "glassing wings" on the Net or here, there are lots of tips and techniques that will make the job SOOO much easier, there is nothing worse that trying to smooth out a lumpy, runny, saggy resin mess on a botched glassing job. Do it right and it only takes a few minutes of sanding to prep for primer. Make a practice piece (sheet some scrap foam about 10' square or so) and practice first, you'll be glad you did.

Next time you install LE/TE caps on sheeted cores, try using masking tape rather than pins. This is also one place that the foaming polyurethane (Elmer's woodworking or Gorilla) glues work great as they help fill any (small) voids, just takes practice to get the right amount. I still use Titebond myself because of the "sandability". Foam safe CA works but is too brittle and hard to sand, IMHO.

You should glass the entire wing, however it is best if you finish-sand, hinge, install gear and servo wells, etc. before you glass them. Some people glass first then cut out and face the ailerons but I find that is far more work. Just do the ailerons/flaps separately. You don't need to glass the open edges of the aileron/flap openings, but you do need to seal the wood with resin.

If you use epoxy, don't sheet the root, just adds extra weight. I assume you'll be glassing the wings to the fuse (do this AFTER you glass and sand the entire wing panel) and that is where much of the wing/fuse joint strength will come from (I assume there's a spar in there as well).

Have fun!

barry

Just how I plan to do it!!! Thanks again Barry. The "PRACTICE" run first sounds like a great idea, will do!! This way, I'll get a FEEL for it first and not screw up the job. I'll let you know how it turns out!!!