Need input from epoxy experts

[Locquatious]

We worked for years developing resin formulations for 3-D printing. Ours were a mixture of epoxies and acrylates. In that process, liquid resin is laid layer-after-layer, exposing the layers imagewise with UV light to initiate the cures of the acrylate and the epoxy. We could make tensile test bars either horizontally or vertically. Surprisingly, the tensile strength was about the same.

In our curing process, the epoxy cured much faster than with an amine cure, but the degree of cure of each layer was probably about the same as what you are doing without a break between layers. I would expect that if we were to wait overnight, the interlayer adhesion would be lower, but there would still be some bonding between layers.

As the cure progresses, the viscosity of the epoxy thickens and molecular motion slows, slowing the reaction rate. As it thickens to a thumbnail deformation hardness, the curing slows significantly. If you then put another layer on, the heat of polymerization from the new layer, lowers the viscosity of the previous layer, and bonding between layers is enhanced. But I doubt it is as good as a continuous layer-on-layer lay-up.

It helps, if you take a break, if the temperature cools down at night and picks up again when you get back to work. The cooling will slow the reaction rate. Then the daytime heat will help soften the previous layer and increase the reaction rate (and exotherm) of the subsequent layer.

Water or moisture would be a bad thing since water will somewhat participate in the epoxy cure, producing an inferior epoxy product. So if you do stop, consider protecting the surface from evening dew and rain.

[GreenWave]

Seems like either apporach can work as long as you handle it properly (sand vs peel ply vs degree of wetness. Not every project may allow all lay down to be done in one session so I think you need to be able to work both ways.

[Secondshift]

I prefer to wet set or to wait and sand if It looses tackiness.

I try work to standards that alleviate my future worry but

not everything is critical and sometimes I even use (whisper) polyester.

It's really about your comfort level.

Maybe give a little get a little.

Maybe wet set the parts of highest concern and next day the less critical

stuff. Worry can be terribly distracting.

[Chotu]

Originally Posted by Secondshift

I prefer to wet set or to wait and sand if It looses tackiness.

I try work to standards that alleviate my future worry but

not everything is critical and sometimes I even use (whisper) polyester.

It's really about your comfort level.

Maybe give a little get a little.

Maybe wet set the parts of highest concern and next day the less critical

stuff. Worry can be terribly distracting.

Yes. Worry is really difficult. I agree. I get really stressed out about things like this.

These are the composite chain plates we are talking about right now. These are what hold the mast up. So my worry is very high. It’s as high as it gets. The only more important parts are the beams that hold the hulls to each other.

So if it were me, I would just do it all perfectly. But, I have to let go of the fact that I’m not actually doing it.

[Allied39]

Seems to me you have all the info you need and you know how you want it done.
You are being given correct answers to the wrong question.

If you are paying you get it your way. Unless your helper feels so strongly that he would rather walk than do as asked by the fellow with the $$

Which leads back to if he walks, can you replace him with someone who will do as asked?

Sorry to answer a question with more questions....but that is the basic issue here....does the fellow paying get what he wants?

Basic stuff, should be worked out in minutes.

[osprey877]

Chotu:
Why does the footer on all your posts say you are allergic to epoxy and you can’t be near it under any circumstance?? Have you discovered a cure or ?? Just curious 😀

[rslifkin]

Originally Posted by osprey877

Chotu:
Why does the footer on all your posts say you are allergic to epoxy and you can’t be near it under any circumstance?? Have you discovered a cure or ?? Just curious 😀

That problem is why he has someone else doing the work and can't just do it himself the way he'd prefer.

[Chotu]

Originally Posted by osprey877

Chotu:
Why does the footer on all your posts say you are allergic to epoxy and you can’t be near it under any circumstance?? Have you discovered a cure or ?? Just curious 😀

Good point. I was thinking of changing that for this discussion. I hired someone to help me with the epoxy work. I cannot go anywhere near it.

In fact, many chemicals cause me problems now.

[Chotu]

Originally Posted by rslifkin

That problem is why he has someone else doing the work and can't just do it himself the way he'd prefer.

Exactly.

Starting to really have some doubts about whether this entire operation is sustainable. Pretty much any chemical seems to cause me some problems these days.

A little while back, when I was down there, some polyester styrene came breezing in my nose. No problem. Everybody else was standing around it. A few hours later, intense sinus headaches. And then my nose basically had a period the next day. It shed the inner liner and it all came out with a bunch of blood.

This project has become project management from a far. And I don’t know if this is going to work. Nothings getting done. That’s not a dig at my helper. But I can’t manage the metal part of the project either. I’ve been trying for four or five months now to get a couple pieces welded up. I’m closer than ever, but every week, it’s like yes, I’ll get to it this week. And they never do.

It would have been faster for me to take a welding course and buy a welder.

I need a couple of 18 x 18 deck hatches. Does anyone make them? No. But they make 18 x 20. !!!

Now that I have chain plates going in, a mast, a bow tube, sails, A new steering system going in, The thing is ready. Ready to at least try. But through all this grief, I’m starting to hate boats. Seriously questioning whether I want to be around them anymore. Feeling a little down about it, but they have brought nothing but stress and sickness to me for years on end now.

[Slainte1]

If you are able to complete the layup in one process without any exotherm its a no brainer. However if it is completed in multiple stages cover the exposed surface with peel-ply or plastic film to prevent amine blush. If the epoxy is still green when removing the film you can go ahead with the layup but if the epoxy has cured sanding will be necessary

[guyrj33]

Can you share any pictures of the mold?
What are the dimensions of the chain plates?
The layup schedule?
If the piece is thicker than 1/2" it might need additional time between layers to prevent overheating. Of course the process can be cooled as it's curing to mitigate some of the heating issues. Cooling would also extend the overnight working time.

[sand6000]

Has nobody thought to ask the resin manufacturer?

[Chotu]

Originally Posted by sand6000

Has nobody thought to ask the resin manufacturer?

The data from them Resin manufacturer and from West system is in this thread above.

Nobody’s really technically a manufacturer of epoxy resin. They are just mixers. It’s all the same stuff.

[Chotu]

Originally Posted by guyrj33

Can you share any pictures of the mold?
What are the dimensions of the chain plates?
The layup schedule?
If the piece is thicker than 1/2" it might need additional time between layers to prevent overheating. Of course the process can be cooled as it's curing to mitigate some of the heating issues. Cooling would also extend the overnight working time.

There will be no mold on the actual chain plates, the part being worked on right now is a sort of core that the chain plate laminations are draped over. It has the big half inch stainless steel piece that the turnbuckle would connect to integrated into it.

Then, you drape all of your pieces of fiberglass that make up the composite chain plate over this piece. This is the piece I have concerned with right now. Because it’s being left overnight in between some of the pours.
I’m worried there could be a line in there that’s not bonded as well as the rest causing it to fail. Worried that the core is not one complete unit.

So it’s more of a pour. Just a little half inch at a time. It can’t be cooled. There is no practical way to do that.

[AKA-None]

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