Need input from epoxy experts

[Chotu]

Originally Posted by AKA-None

So you can’t put it in a fridge or similar to slow it down overnight?

No. It’s off grid, it will kill me if put in the boat refrigerator and it would be very irresponsible to put poison in the marina refrigerator

[Chotu]

Good news! He’s open to doing it either way. So, we will go wet on wet because these are the chain plates.

That’s a big relief.

Probably still never going to get the metal work done, but I guess I should contact that guy again tomorrow.

Anyone ever seen an 18 x 18 deck access hatch? I sure can’t seem to find one.

[Singularity]

Originally Posted by Chotu

Good news! He’s open to doing it either way. So, we will go wet on wet because these are the chain plates.

Do consider:
Wet-on-wet, particularly with a large layup, makes it more difficult to get the glass:resin ratio correct. Routinely ending up wet, the resultant mechanicals end up more compromised than taking a staged approach with a full cure under peel ply. The graphic below merely reflects hand layup limitations without respect to staged-or-not curing.

I otherwise agree with the not liking wet on tacky. I understand that it can be perfectly acceptable, but the art of doing it correctly isn't worth learning to me in a peel ply world.

[GRIT]

The test I've always used is to touch the layup with a cotton ball, if a bunch of the ball sticks to the laminate, I'll continue laminating. If none of the cotton sticks to the laminate, I'll wait for a full cure, sand, then laminate.

I'm also a proponent of wet on wet, especially when it matters most. I'd consider chainplates to fall into that category.

Cheers, and good luck.
Paul.

[foufou]

What Heywood cited. When I was building epoxy boats thirty years ago, we were able to build an admittedly small hull in four hours. Then vacuum bag it and go to lunch. We started in the morning in cool temperatures and after the laminating was done we lowered a foam insulated box over the mold to post cure at higher temperatures. We used laminating resin from Gougeon Bros which had much less exotherm than their 105/205 formulation. I would think that laminating resins are formulated to have less exotherm precisely so one can add multiple layers without problem. The temperatures you are working in make your situation difficult. Maybe you could add a small air conditioner to make working conditions more user friendly. Good luck with your project. Foufou

[Chotu]

Originally Posted by foufou

What Heywood cited. When I was building epoxy boats thirty years ago, we were able to build an admittedly small hull in four hours. Then vacuum bag it and go to lunch. We started in the morning in cool temperatures and after the laminating was done we lowered a foam insulated box over the mold to post cure at higher temperatures. We used laminating resin from Gougeon Bros which had much less exotherm than their 105/205 formulation. I would think that laminating resins are formulated to have less exotherm precisely so one can add multiple layers without problem. The temperatures you are working in make your situation difficult. Maybe you could add a small air conditioner to make working conditions more user friendly. Good luck with your project. Foufou

The project is off grid. There is no way to just run an air conditioner. There is no main power.

The best we can do is have the Hardner referenced in this thread.

And in fact, that’s how I built the whole boat. So nothing new to me. Ha ha

[ShoreFun]

I come the automotive restoration side of things.

What I learned is almost all the advice by people is either wrong or very very wrong.

What I know about epoxy is not a lot. I did learn that epoxy primer will not cure if you put down an acid on the metal, epoxy takes a base to cure. Epoxy primer also has a recoat window with full adhesion. It was explained to me that the epoxy has microscopic holes in which the next layer can stick their chemical chains in and when the epoxy cures it closes the holes and locks the chain into the matrix.

I do not know if the above applies here. The above information came from the owner of SPI paints when I called and asked what really happens with the paints.

I went to page 23 of the West Systems manual and it was clear.

The mixture will become tack free about midway through the initial cure phase. While
it is still tacky (about like masking tape), a new application of epoxy will still chemically
bond with it, so you may still bond to or recoat the surface without special preparation.
However, this ability diminishes as the mixture approaches the final cure phase.

I have a rule. I follow what the manufacturer says I need to do for each product. If I am unsure or am thinking of doing something slightly different I call and find a technical person that can give me insight in what is chemically going on and why.

I suggest that if you have any questions that you just call the manufacturer of the epoxy you intend to use and get the answer from someone that actually knows the correct answer. Sounds like you life might depend on a correct answer.

[DMCantor]

The manufacturer of the epoxy that I use (MAS) says "if you can sand it, you must sand it" between coats. If it is too soft to sand, it's OK to just go ahead and recoat.

[Benz]

I vote for full whack at one go. Then it will be one monolithic piece.

[s/v Jedi]

For non vacuum bagging but need for strong laminate, I like to use spacers of exact required thickness of laminate, put these around the layup, then put a 1/8” thick plastic sheet on top, followed by thick flat plywood, mdf etc., followed by heavy weights. This squeezes excess resin out and creates exact thickness as well as nice finish.

[sailorladd]

I have been working wet on wet with epoxies and polyesters for almost 50 years, I avoid wet on dry like the plague.... there should be no compromises when it comes to areas of stress and reinforcement...wet on wet is stronger. Period.

[Seaward22]

You took the right step, initially at least, by contacting the manufacturer. They should know every detail of how their product works. When patching two lighting exit points with a 12 X the thickness radius patch the West System engineer told me to remove as much epoxy as possible ( without making the glass look dry of course). Those two, below the waterline, patches have held up to a fair amount of pounding both in and out of the water (trailer) for 8 years now. But I would let the manufacturer be the final word on acceptable methods. If you can do the repair in one setting…..

[kmacdonald]

Lay it all up in one go. If not, it requires cleaning blush and sanding before laying up more glass.

[Ratty1978]

Originally Posted by Chotu

So, I’m having a little bit of a dilemma here. And I know my helper on the boat can read this so, it’s going to be a little awkward.

* * *

First, the way I do it. If there are multiple layers of glass to put down, I do everything wet on wet.


* * *
can put a couple layers down, then leave it overnight, and then come back in the morning and put a couple more layers down.



* * *

Because it’s the chain plates, stress is at an all time high. These components are as important as when I made the cross beams that hold the hulls together.

(1) Generally, your method better guarantees cross linking of the epoxy molecules throughout. This means there's a chemically unified, continuous, mass of resin, reinforced by fibers wholly encapsulated therein. And if it's chain plates, I'd opt for best possible bond.

(2) There is generally a time period where epoxy kind of "hardens" but some level of cross linking is still possible. Maybe the manufacturer has provided enough information on time, temperature and probably humidity, to permit this to happen as described. But if you're doing it at 45 latitude in the Spring, it will be different than 30 latitude in the Summer. There are also fast cure and slow cure catalysts.


(3) Additionally, there's laminating and finishing resin, the latter is supposed to have a smooth surface when cured, and I think is described as having "blush" when cured, the former is made for adding layers. If you use the wrong resin, you might need to clean the surface for a good bond. Might be extra waxy compound in finishing resin.

(4) Once the "lower" layers are fully cured, you're relying on only an adhesive bond, not cross linking of molecules. A lot of times this is the best you can do. Same thing with laminating and finishing resin. Prepare the surface for a good bond.

[Chotu]

Of course, I am loving these responses because that’s exactly how I learn to do it. And I actually have done enough epoxy work that I can no longer do epoxy work. Lol

My helper is pouring the other chain plate core today. All wet on wet. He will fill up the whole mold. That’s the only way to do it in my opinion.

These parts are pretty cool. So, I will put some pictures up as soon as I get them.