Systems Three Gel Magic?

Has anyone used the Gel Magic epoxy from Systems Three? Just curious at this point but will probably try it unless I can comfirm negative quirks or whatever with the stuff. Doing a small sailboat's rotten transom from the outside and will glue 3/4 pt plywood onto the existing thick frp inner skin and then glue the outer frp transom skin to the ply.

Thanks,
E

 

Are you going to use some new glass/ epoxy to connect the outer FRP skin to the boat hull?
Hope you just didn't mention it.

 

This is only a 17' x 1600lb frp sailboat built like a tank. Most this size only have a single skin and no structural core in the transom. This boat has a 1/4" +thk inner skin with 3/4" ply and a thinner 3/16" outer skin. No cloth on the outer skin. Just structural epoxy gluing it to the ply.

 

The strength comes from glass, not epoxy.
Especially not on the transom.

Good luck

 

I have to respectfully disagree about glassing this one. Maybe you are thinking regular epoxy resin instead of structural epoxy glue? This boat doesn't even need the ply or skin. In this case the ply is the designed structure like all other boats and the outer skin keeps water out and provides ding resistance. Its built with major overkill with the inner skin. Structural epoxy glue will certainly hold this together. Today's stitch and glue wood boats are epoxy glued and stay together. I built a wood ultralight plane and the entire airframe was only glued with Sys Three T-88 structural epoxy. Flew it around in Florida and it stayed together. 99% are built this way. Glass has it place but not needed here if I use structural epoxy.

Thanks.

 

Don't use PT (treated) plywood, use Exterior (PS 1-95 grade) or Marine grade plywood instead. The new PT chemicals (CA) doesn't bond to epoxy. Gel Magic and the other structural goo's now available all work well and are esentally the same thing we make up ourselves, with thickening, bulking and other physical attribute changing agents. You're simply purchasing the convenience of a premix, which ounce for ounce is a lot more costly, than mixing it up yourself.

 

Thanks for info on CA (C?). Standard poly and epoxy resin sticks to cca and acq. Do know of any tech papers on why epoxy doesn't stick to CA? I no longer subscribe to the APA and can't access their tech papers. Do you know if they have current testing on CA? I'm not using non treated wood and one way or another it will be epoxy on pt.

Standard epoxy laminating resin that most of us use and mix with fillers isn't a structural adhesive. It works but not to the higher strength of structural epoxy. So gel is on my radar. I used gel (now discontinued) from another mfg and it was a easy, no sag, no runs no problems and super strong.

 

I've used both Gel Magic and System three general purpose resin. Mostly the general purpose resin. Listen to Paul and stay away from the PT.

I've built engine stringers for a small v-8 and reinforced the transom on my old Silverton using general purpose resin without any issues.

Good Luck

MIA

 

CCA if you can get it sticks just fine with epoxy and other adhesives. CA tends to clog up, the cut/sheared cellular structure, so penetrating goo's lose some peel strength. It's still a good grip, just not as good as it can be. Scratch the crap out if it (16 - 24 grit) and get a good mechanical bond. Most of the APA papers are public, you don't have to pay, unless you want to be one of the first, to know something. PT treatments on plywood aren't as effective as solid timber, being only as deep as the outer veneer. Sealing edges and penatrations are more important with sheet goods.

Agreed, most don't get the best out of their epoxy laminates. Using lighter, but stiffer or stronger materials as the reinforcements, can be cleverly thought through. I know what's in these premixes and make the same thing regularly. I'll also bet what made your discontinued goo "super strong", was in compression, sacrificing elongation and/or tension modulus, a common trait of this type (BPA) of thermoset. I have a nice Kevlar mix you'd like.

 

Interesting. At one time the APA had free info and later went to paid subscriptions. Last I looked (not lately) you still had to buy the tech specs to reference their entire data base.

I've been using epoxy over cca and acq on pt ply and dimensional lumber for stringers, transoms, floors for 25+ yrs. No issues but lots of naysayers. Greenwood XL was the boating industry standard for pt marine ply and it worked without issues. I think Sherwood makes them now. I haven't researched or tried the CA so can't comment until more info is gleaned.

I cut glass strands for the strongest filler and kevlar probably has the same symptoms as thickener. A 50/50 mix or anything close will not be a gel or as easy to use as a gel.
My opinion (experience has helped form it) is anytime you add enough filler to resin to the point of making it a gel the resin is compromised. I've mixed a lot of different fillers in poly and epoxy and most, if not all, separate from the resin. Epoxies are worse because the kick time can't be adjusted as easy. Gels stay in the gel stage and are easy to use. What is your experience with pre-mfg gels and what brands have you used?

 

I have never had a filler separate from epoxy under any conditions.
I'd rather not buy a bunch of single purpose epoxies when I won't use all of any one of them and will have a bunch of expensive bottles just sitting around.

Mixing my own means having only 2 or 3 epoxy bottles, much easier to keep control of the cost and have enough whenever I need some (not running out of something specific).

 

You've never had resin run out from a filler, you must use a lot of filler and have a very weak mix. Structural grade resin is a different chemical formula and stronger (considerably) than non structural. The difference isn't about fillers. Ask your resin mfg or chem engineer.

Do your own testing to see the difference. Fill two soda straws with each type of resin and let them cure. Do destructive testing and see which fractures first. Do another the same way between standard resin thickened to a gel consistancy (won't run out of the straw when held vertical for the full kick time) against one that isn't thickened. Doesn't take much time or effort to do this. Your results will show structural is stronger and adding filller weakens.


To PAR: I logged on the APA site and the only spec I could find about resin sticking to pt ply is (W240) the same one dated as "revised in 1997". I read that one a long time ago and it only covers CCA with polyester. It used to be free but cannot be downloaded and has to be purchased now.

L8R

 

Perhaps you would give me a specific recommendation for Structural epoxy and non structural.

Personally I use West system on wood. Never seen any reason to use a "stronger" epoxy.
That is except for aircraft where its all pre-preg - which is so different as to not be an issue.

Weak mix? What are you talking about? Epoxy is mixed at a required ratio (with a little tolerance) not just at your whim. Sounds like you are talking about polyester.

Specifics please.
I'm not a chemical engineer or an industrial formulator but I have some experience.

I do recognize a difference with an adhesive vs a laminating resin. Each for their own purpose.

 

I'm thinking the same thing you are upchurcher.

I've used System 3 general purpose resin for laminating, built stringers out of it (fiberglass layup over foam cores), used it as a glue for tongue and groove joints, made fillets out of it, coated and sealed with it......on and on it goes. Mixed it with silica, q-cells, wood flour, plastic mini fibers and talc (baby powder). Never noticed any separation of resin from additives.

Never had an issue with any of these applications.

I don't believe there is anything special about System 3 general purpose resin. My money says PAR is right and many resins would perform similarly.

Maybe if I were building a supersonic aircraft things would be different but for my boat it's all been good.

I don't know what he's taking about.

 

Seems we have a communication issue but if you are happy using what works for you keep using it. If you tell me adding filler doesn't weaken resin then I just disagree with you. Ask a structural chem engineer if it matters to you. I'm just stating my opinions whether they agree or not with anyone.

Systems Three laminating and T88 structural are my choice over WEST and any others. The reason is only because I have used them more than WEST or others. I currently have WEST and four other epoxy mfgs on my bench so it isn't like I don't use them.

Few home builders for exp aircraft are using prepreg here in the south. I built a wooden ultralight and know many who build. T88 is the structural glue they use and the reason I started using it back around 1990 for the ultralight. It would be difficult to add filler to T88 because it's too thick already.

Weak mix comment was about adding filler to resin. The more you add the weaker the resin gets.