Kregg

My Feedback: (45)

Am I doing something wrong? I have been trying my first aircraft with a fiberglass polyester resin finish. I have the Sig polyester resin and deadly Sig hardener drops. I have been using the recomended number of hardener drops per ounce (15 drops per ounce I think?). I have mixed and used several small batches for the smaller parts. The mix take many days even weeks to harden and they still feel tacky. I have increased the drops to about 20 per ounce with simmilar results.

My process: I lay the glass over the surface and then spread a thin layer of resin over the surface and partialy around the edges. Then I hang cloths pins from the glass cloth to keep the edges down as much as possible while it (sort of) dries. I carefully place the part so that the clothes pins hang down freely and applies tension to the glass. Days later the resin is still tacky and can be pulled up pretty easy. I have not tried to do a second coat yet. I have a few bubbles and the edges are questionable at best. The edges dry enough to eventually sand the extra glass cloth from the edges, but then these same edges threaten to lift. I mixed another batch of resin in an attempt to seal the edges (both side are glassed now), but I cant seam to get it to stick well and the resin cures soooo slow. If this was nitrate dope I would just rub the edge with my finger until the dope curred and I would be good to go to the next step. Attached is a pic of the small electric warbird that is my test subject. I'm using the .50 Sig glass and trying to keep it very light.

Help! I was also planning on using this same stuff to renforce and glue some parts to a poly resin fuse on another project. But I will not try that until I'm more comfortable with my results. two slightly different applications but the drying should be the same. Next time maybe I will go the Z-poxy route, but I no this stuff should work too and I have all the stuff. Please help. Thx

Rarebear

Kregg, Make sure that the surfaces are free of dust and any kind of oil residue, use a tact cloth,double check your measurements(1 oz of resin is just under 1/8 cup. Room temp,and humidity can affect how well the glass resin works. Acooler room means more cure time. Hope this helps!

KevinSheen

My 2 fuses have given similar results using SIG finishing resin. I built them both in my garage during the winter. I let the resin dry for a week or so and then just bust the surface down with a low grit paper (100) but be careful NOT to cut the cloth. For me, the second coat of resin usually tends to not be as tacky as the first.

I use a finer sandpaper in order to 'cut' the cloth. One thing I haven't had a problem with is getting the cloth to 'stick' to the wood but then again, I haven't tried to peel the cloth off. I just run a sanding block along the edge to cut it where I want it.

In both cases, the fuse / finish turned out fine for me. One was heavily used during last year and the worst rash was paint chips or scratches, no damage to cloth or the resin surface.

I have learned subsequently, that resin used for a surface coat has a small amount of wax incorporated to help give a complete cure. That wax is available for purchase and you can even purchase resin with / without this wax included. If you use a resin with the was included, you need to remove the wax from the surface before recoating. I don't know the percentage of wax that SIG includes with their resin but I would think it might be low.

What is the temperature that the part is drying at?

I wouldn't use this stuff for mounting anything inside of a fuse like you are saying. I would use goop.

hope this helps,

Kevin

KevinSheen

One thing I forgot to mention.

Polyester resin won't cure when applied over epoxy (glue joint or fillet). Are you dealing with that at all?

I've heard that some people have luck using CA as a 'sealer' between the two.

Kevin

Steve Collins

My Feedback: (8)

It sounds like you are using waaaaaaaaay to much hardener. I believe, if you check the can, it says something on the order of 8 drops per ounce. I experienced a lot of trial and error with polyester over the years. It seems reasonable that the more hardener you use, the better/faster it will harden. THIS IS NOT SO. I believe too much hardener is a good part of your problem.

As mentioned earlier, polyester is a little temperamental about curing anywhere near epoxy. If you use polyester to glass with, it is best not to use any epoxy on your project at all. I have also seen it take a very long time to set up over some of the hobby fillers like "Model Magic".

I have also noticed that it seems to cure much better when using fresh resin and especially fresh hardener. My recommendation is to buy a fresh bottle of hardener, use only the recommended amount (found on the can), and make absolutely sure it is not applied anywhere around the substances already mentioned.

I have had a number of gooey messes in my time but the stuff does eventually cure.

Kregg

My Feedback: (45)

Aptar,
Thank you very much for your responce. My problem has been solved by moving the pieces to a warmer part of my house. I have applied the second coat of unthinned resin and it dried great and has a very smooth finish. The finish coat only used 15 drops of hardener and it cured in about 15 to 18 hours.
Thx, Kregg

FYI: The Sig hardener bottle and the Sig finishing resin can both indicate to use 15 drops of hardener per ounce of resin, plus that this is just recomended and you can increase for faster hardening or decrease for slower hardening.

EASYTIGER

My Feedback: (119)

Ugh. Throw that stuff out. Get some z-poxy epoxy finishing resin. A LOT easier to use in all respects. You'll see the difference. Does not smell as bad, either.

pittsdriver

My Feedback: (7)

I agree with easytiger. I used polyester resins for years and discovered epoxy resins and will NEVER use polyester again! Z-poxy is very nice to use and sands great. No more gummy sandpaper, I can use one piece of sandpaper to three or four with polyester. You also get a longer working time. Also try Stits Smooth Prime, the best primer on the market for glass.Don

EASYTIGER

My Feedback: (119)

Plus, polyester is stinky and hazardous to boot.
Think about this, too. No measuring drops of hardener. Just squeeze reasonably equal amounts out of identical bottles. Not critical. Zpoxy is the best of them, though others like west systems, too.
Sands really easily.
I have seen batches of polyester that NEVER set up. Scrape it off, or just toss the model away when that happens.

perfectplanes

My Feedback: (133)

Kregg,
Another glue you may want to try for applying wood formers to fibergalss fuse is STABILIT EXPRESS. This is a very strong glue in almost any application, and I think it is one that Yellow Aircraft recommends for their wood/fiberglass attachments. It is VERY expensive so I would suggest using it only where the formers attache to the inside of the fuse and possibly wing roots. Check out Hobby Lobby's web page.

PS.
By the way, very nice job of the Thunderbolt! It that a Top Flite? Looks like you opted to build the cowl instead of using a fiberglass one.

pittsdriver

My Feedback: (7)

I just tried Joe Huntley's process with laquer base polyurethane over 3/4oz cloth. Works really well and is real easy to apply. Dries quick and sands great and as a bonus is very light. I am going to use this method from now on. Another bonus is for those of us who have a reaction to some epoxys. I built surfboards when I was younger and have glassed dozens of models. I am almost done with a full scale Lancair 360 and I'm doing all of the glasswork on a friends Glasstar and it's taking its toll on my hands. Wish I could do those with the polyurethane. I also see some guys use water base polyurethane so there is no smell. I might try that later but the laquer base isn't to offensive. Don

k_sonn

My Feedback: (32)

I agree with Easytiger except I use West Marine epoxy resin. It gives you a little longer working time than zpoxy.

Greg Takacs

I am in the process of making my first mold for a helicopter canopy and West System 105/205 worked out great.
The plug was bulged out by too much foam on the inside, so I had to make a new one and I've tried the SIG poly resin and it was a disaster. (I only had a little of the West System from a fellow flier and I've already used it all up on the fisrt mold so I had to go with what I've had) I have waisted a bunch of cloth with it for getting too sticky too soon and not being able to work the air bubbles out. So I drove 70 miles just to pick up some West System resin and it seems to work great. I'm sure I'll never try poly resin any more....