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Old Jan 30, 2014, 12:35 AM
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United States, NV, Reno
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Help!
Epoxy questions

I am attempting to make an order of micro balloons and cabosil along with some decent epoxy for joining and laminating. Specifically I need products to join the webs and ribs for the spar of a Bubble Dancer and then I need a laminating epoxy for the spar caps and securing the kevlar tow.

Ideally I could buy 1 product but not sure if that is advisable.

Can I use just one epoxy for both tasks without too much compromise?

if I just use regular epoxy to laminate the spar parts and kevlar glass cloth etc. is that going to be inferior to using a specialized product?

A build log I was reading said to use cabosil to thicken the epoxy while joining the ribs to the sheer webs. Why would you not just use epoxy on it's own?

I just have great plans 20 min epoxy at the moment

Here are the products I am considering.

http://www.cstsales.com/west_system_epoxy.html
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Old Jan 30, 2014, 02:04 AM
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Fickle:

I use West Systems a lot, and have become a big fan. It is excellent for laminating. Buy the smallest portions you can of the #205 hardener, and be sure to get the electronic scale for measuring the proportions. Apply sparingly.

CST should also be able to supply the cabosil.

The short-term epoxies (like the Great Planes products) have their uses, but not in the application you are looking at. They tend to be brittle.

Yours, Greg
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Old Jan 30, 2014, 08:36 AM
Mark LSF # 3792
United States, TX, Garland
Joined Nov 2008
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West Systems and stuff

I use West Systems #105 resin for laminating and have used it for bonding as well, great stuff. Their information sheets and the resin can states the various uses. Unlike Greg, I use the #206 hardner which gives about a 20-25 minute pot life, helps sometimes when aligning assemblies or laying up parts.

A tub of their #406 Collodial Silica should last you for years to thicken the epoxy for bonding purposes. In small batches it doesn't take much. It's not as good as their #405 filler for strength though, but "very good" in most uses.

If you're mixing small batches of West Systems, or any fluid epoxy, get some 1 oz. medicine cups. Just Goggle "medicine cup" online, 100 for almost nothing and work great. Can even be reused if you let the excess cure and pop it out.

To measure West Systems in small batches I use hypodermic syringes. I find them at my local farm supply and use the largest gage needle with the point blunted. Makes it easy to hit the 1-5 ratio of hardener to resin and they are cheap.

Mark
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Old Jan 30, 2014, 10:59 AM
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I agree with the West Systems resin and colloidal silica route. There used to be a resin called PJ's that was better than anything else on the market for making glider wing skins but they aren't around anymore. I wonder what the high end manufacturers in Europe use on their models.
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Old Jan 30, 2014, 08:45 PM
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You guy's should check out Resin Research epoxy it's competively priced and it's as close as one can get to MGS resin with out having to pay the fine on each can of it's catalyst. It's used on the Icon series of glider's and it was Don Peter's that turned me on to it. Just so you guy's know I've been working with advanced composite's since 1971 and I try to use the best material's.
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Old Jan 31, 2014, 12:35 PM
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West Systems is an ok epoxy, but frankly MGS is much better. West has pretty good properties, but it was designed to seal wood in boat building applicatons. MGS was designed for the manufacture of aircraft and is on the list of acceptable materials for many homebuilt and commercial aircraft. You have to ask yourself how much you will use and whether the strength/stiffness of the epoxy is going to make a difference to the performance of your airplane or parts.

Most places I see use MGS with fillers like chopped fibers and a bit of cabosil when making major structural joints. I am talking places like Schempp-Hirth, Glasser Dirks, etc. Since they use MGS in the layup of the skins and spars, there is good compatibility using the thickened MGS as an adhesive.

If you really need the shear strength of a true adhesive, you can look into the specialized bonding agents made by Hysol (Locktite). They have much higher shear strength and are highly resistant to peel. But they are also the consistency of peanut butter and are specifically designed to bond two pieces together in a post-cure setup. You would never use this stuff to wet out fabric.

At the end of the day, ask yourself how much strength/stiffness do you REALLY need. Is it worth paying extra? Most of the time the answer is no.
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Old Jan 31, 2014, 12:38 PM
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Quote:
Originally Posted by edfmaniac View Post
I agree with the West Systems resin and colloidal silica route. There used to be a resin called PJ's that was better than anything else on the market for making glider wing skins but they aren't around anymore. I wonder what the high end manufacturers in Europe use on their models.
Most manufacturers of F3B and F3J models are using MGS epoxy. It is easy to spot because it has a light blue tint. I am talking about TUDM, Weberschock and Vladimir's Models specifically.
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Old Jan 31, 2014, 02:06 PM
Mark LSF # 3792
United States, TX, Garland
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"You have to ask yourself how much you will use and whether the strength/stiffness of the epoxy is going to make a difference to the performance of your airplane or parts....At the end of the day, ask yourself how much strength/stiffness do you REALLY need. Is it worth paying extra? Most of the time the answer is no."

That is the reason I have been using West Systems for years. Still have the original quart of resin and the original 7 oz. can of hardner I bought maybe 6 or 7 years ago. Their claim of an extremely long shelf life for my use appears to be confirmed. Store it in my work room which is temperature controlled.

Use it mostly for repairs and small glassing jobs, wtih some bonding. Just finished glassing the center section of my new HLG with it. Since I'm not laying up big structures or glassing big wings and trusting my life to them, I couldn't justify buying the "bulk" quantities the other brands were packaged in. Plus, there is a West Marine store only 3 miles from my house.
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Old Jan 31, 2014, 04:59 PM
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I think I am in the small batch boat. Honestly the minimum order from West seems like way more than I need which is what prompted my question initially. That said I was not aware of an extended shelf life. My epoxy will typically last 6 months to a year so that makes it a little more practical to buy in these quantities.

Also, I am going to have to check into if there is a West distributer near me.
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Old Jan 31, 2014, 05:26 PM
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Check out http://www.uscomposites.com/epoxy.html

Their 635 Thin with the med or fast hardener works great for general use.
Disclaimer! Yes I use MGS for bagging DLG wings and making fuses. But this is my go to epoxy for everything else. You can also get your cabosil and microballons there. West is fine, I've used it, but mixing ratios are easier, and the viscosity is lower with the USC stuff.

By the way, forget the pumps unless you are building a boat. Get an ebay scale and weigh your mixes. I have one scale (that's right, you might need more than one) that reads in .01grams. For a repair I can mix 2 grams of epoxy accurately.

Dave
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Old Jan 31, 2014, 07:47 PM
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United States, MN, Albert Lea
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If you're just laminating some spar caps and shear webs you won't need much epoxy. You might look at www.systemthree.com - they sell trial kits of most of their products. For the tiny amount you'll need I think that would be cost effective. They have various pre-mixed fillers and hardeners for filleting and bonding so you don't necessarily have to add colloidal silica

I've used West System too and it's ok, but he downsides are cost and the 5:1 mix ratio which is less forgiving of measuring errors, compared to 2:1 for most other brands.

Quote:
A build log I was reading said to use cabosil to thicken the epoxy while joining the ribs to the sheer webs. Why would you not just use epoxy on it's own?
A laminating epoxy on its own will be thin and runny - it makes it easier to flow into the cloth fibers when laminating fiberglass, kevlar etc onto surfaces. However if you're trying to bond two surfaces such as spruce or precured carbon sparcaps to balsa webs, you need a thickener to add strength to the joint, fill small gaps, and minimize the amount of epoxy soaking into the end grain balsa which adds weight.

Steve
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Old Jan 31, 2014, 08:39 PM
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Adam from Wyoming wind work's did some very depth resin testing and in the final analysis R-2 came in 2nd behind MGS. Don Peter's of Maple Leaf Design said that other resins never seem to totally cure and I think he was involved in yacht building before he got into model glider's. Last I heard he was still using R-2. Please know that I'm just putting info out here and not telling anyone what resin to use. I started using R-2 shortly after a fine was leevied on the catylist of MGS and I'm fortunate to have a store to go to right here in Tucson. R-2 is headquartered here in Tucson as well.
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Old Jan 31, 2014, 09:21 PM
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Quote:
Originally Posted by Fickle flier View Post
I think I am in the small batch boat. Honestly the minimum order from West seems like way more than I need which is what prompted my question initially. That said I was not aware of an extended shelf life. My epoxy will typically last 6 months to a year so that makes it a little more practical to buy in these quantities.

Also, I am going to have to check into if there is a West distributer near me.
There's a West Marine in Reno. They carry West Systems.
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