Which resin?

[Varmint]

United Resin UniLam RTL with a hardener that will give you around a 500 CPS or so. I do not remember the the hardener number but if you call them they will tell you what the hardener is. It is a 30 or 40 minute pot life product. Been using it on and off for years. That will give you a near water resin that wets out really well. It is not overly expensive and you have a real nice choice of hardeners to use. I have been using Aeropoxy for about 15 years and will be going back to United as soon as my last gallon is gone. Started out with Saf-T-Poxy II in the 80's and when that got spendy went to some stuff made by King Fiberglass up in Seattle.

If you want to thicken up epoxy and want it structural you use cotton flock. If you just want it thicker you use cabosil or microballons. The problem with cabosil or microballons is that it will crack if flexed. Milled glass is considered structural but it will also crack if flexed much.

If you are laminating you want the thinnest stuff you can find so it is easily absorbed by the glass, especially if you are not vacuum bagging. Link is below:

http://unitedresincorp.com/

[tlandauer]

This is great, love the amount of knowledge one gets here. I have a related question: when I see posted pictures of hull reinforcement, I mostly see pictures of Carbon Fibre, may be a minority of pictures showed regular FG cloth/tape reinforcement. I assume CF is stronger, but regular FG is OK too right? Also, if one lays down a pretty good amount of CF, does it ever bother radio transmission? I read some where on CF hulls one needs to pay more attention to this aspect, although I presume that is because the whole hull is made of that stuff.

[jcald2000]

I use this epoxy for molding complete hulls and parts and the Airplane guys have tested all the popular resins and this is as good as the MSG resins at a much lower cost. I have been using it for several years for everything. It does not have a strong oder either, a big plus for me.

http://www.uscomposites.com/epoxy.html

[Fluid]

...I mostly see pictures of Carbon Fibre, may be a minority of pictures showed regular FG cloth/tape reinforcement. I assume CF is stronger, but regular FG is OK too right? Also, if one lays down a pretty good amount of CF, does it ever bother radio transmission?

Carbon fiber adds stiffness to the surface to which it is applied, that is why we spend the $$$ for it. But to get the maximum benefit most of the resin needs to be squeezed out and the cloth pressed firmly to the underlying surface while the epoxy cures. Most of us do not do that. Carbon fiber by itself is pretty brittle, so to say that it adds "strength" may not be completely correct. Fiberglass adds relatively little stiffness, but it does increase the strength of the underlying surface by increasing thickness.

A carbon fiber floor should not cause problems with a decent radio, my FASST radio has no problems even at great distances (over 800 feet) in my cats having carbon floors. I did have problems in a fully carbon fiber hull with both 75 mHz and old Spektrum 2.4 radios.



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[Fluid]

I would be weary of any 30 minute cure time epoxys if your looking for a very glossy finish

I wouldn't. The Z-Poxy Finishing Resin cures to a decent shine, then do a bit of buffing if you want it to hurt your eyes in the sunlight. But who needs that for an inside-the-hull application?


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[tlandauer]

Thanks, Fluid, this helps a great deal to clear my mind.

[desmobob]

I guess I have it all wrong: I've been using 30 min. ZPoxy to reinforce a used hull with FG tape/cloth. I thought it worked but now I think I should have used the Finishing Resin instead. What is the real difference between the two?

The finishing resin is made to mix up thinner so it coats and penetrates fiberglass and CF cloth without the need for thinning (which weakens epoxy).

I have the West Systems epoxy in the shop but I think it's better suited to full-scale use. I use Z-Poxy Finishing Resin on any fiberglass work I do on models.

Take it easy,
desmobob

[martin]

Ive found with most epoxy laminating resins when you want to add another finishing coat you get fish eyes in the resin, Ive tried several of the ideas around for curing this but find its quite difficult to prevent this happening. I was plesently suprised to find that Z- Poxy Finishing resin dosnt have this problem at all. Martin.

[Varmint]

I would tend to think that fisheye would be a contamination from what you are mixing it in or the brush you are using. If you are using a hair type bristle brush it may have been processed with a chemical that causes the epoxy to fisheye. Most brushes are made in China and it it tough to know how they process them. If I am using a brush to apply a flow coat I always hose it down with MEK or Laquer thinner first and let it dry completely before using it. I have never had a problem with any epoxy that way. Only if I did not clean all my mixing/painting equipment first.

You may want to wash the surface down with a degreaser like PPG Acryliclean first to get rid of any surface contaminate. If you sanded it with a non filling type sandpaper first it may have traces of compounds that would cause fisheye also. Thinner products will show that problem as they will literally run away from the defect.

[tlandauer]

I have another question: when one is reinforcing the hull with CF cloth, I assume most of you use epoxy to glue down the cloth to the hull. I seemed to remember I read a building thread/article by Randy at BBY. He states that he will use a liberal amount of CA to glue it down---I can be completely wrong, so if I am, please forgive me. Here is the point: assuming that is a different school/technique: does one then use epoxy to coat that reinforcement once it is dried/cured or it is enough just with CA. Wouldn't this combo make the hull extremely stiff to the point being a bit brittle? Excuse me for belaboring on this topic as I want to learn as much as possible before attempting to do any major project myself. Thanks guys. Tim

[Varmint]

There are a couple of spray tacky glues made by Airtech and someone else but the name does not come to mind. You can use Scotch 77 spray glue(Available at your local Home De-pot, or Lowes). It only requires enough to hold down the cloth, a light mist in between layers of cloth. Just enough to hold down the fabric. If you use CA you will have incomplete penetration of the resin as it will fill parts of the weave prior to resin application. Carbon is kind of the pits to work with out of a vacuum bag unless it is a really supple weave to begin with. A lot are not very flexible. Hope that helps.

[tlandauer]

Thanks, I see what you mean, I think I misunderstood Randy's thread.

[Chrisg81983]

Randys thread about using ca for cf is on abs hulls not for fiberglass. He said he found ca to stick the best to abs

[tlandauer]

Yes! You are right, I realized now that he was refering to that combination, thanks for clearing it up for me! I am still curious if that makes it overly stiff. Even with ABS, since ABS is quite flexible, would there be any issues between the area where there is reinforcement and where reinforcement ends, i.e., where in the front where one can't get to.