Epoxy and cloth questions

[TexasZeke]

While I'm not to the point of needing these answers yet figured I might as well get them out of the way

I have followed all the threads about weight vs. strength and have come up with my questions of how to find the perfect balance. I'm using 6oz. cloth inside and out and U.S. Composites slow epoxy. Please correct anything I say as wrong, this is my understanding from what I think I've read here.

When I get ready to do the saturation coat, I brush, roll, whatever, to get the epoxy spread, and then take a squeegee to remove the excess.
How long would it need to sit before the Squeegee?
Can I just push the epoxy to another part of the hull and continue on? Seems like it would waste a lot of epoxy just to squeegee it off and not use it.

Once I get ready to apply the cloth I really like the idea of doing it all at one time opposed to strips.
Do you have time though to wet out a whole hull this time of year. I'm assuming you mix a cup or two of epoxy at a time and go to work, mixing more as you need it.
Do you ever run into a problem with it kicking before you finish, or what do you do to prevent it? In my mind I can think of like your painting a wall and you keep working the wet edge.
Do you alternate back and forth from one side of the hull to the other so your always working a wet edge?
The boat I'm building has tumblehomes ( I guess that's how you'd say it) How would you do that? Pick a spot to stop putting down cloth and finish up with a strip once you flip the hull?

From my understanding you want no more epoxy than is actually needed. A thin saturation coat. Enough to wet out the cloth, then a few thin filler coats to fill in the weave of the cloth. I will say this, and it's just from making the splices. Epoxy is much thinner and easier to work with, spread and such, than poly.

This last comment is mostly for Ron. After I finished the splices tonight I had a little epoxy left over. Now I don't know exactly what time I mixed it, but I'm pretty close on when I did. After somewhere between 45mins and an hours I gave up and went in the house and it was still flowable in the cup. Question is can you work that slow. If not might think about a faster hardner

Another question just popped in my head. With epoxy do you ever back off on the hardner like you would with poly to increase working time

thanks
kevin

[FishingSETX]

Not an expert here, but from what I've read here and in a couple of books, you usually use one piece of cloth to cover the outside hull, one to cover the inside hull and you do the same for the deck. This is for strip building though.

I would be leery of changing the resin/hardener ratio. if there isn't enough hardner, it may not set completely (happened on a rod I was building).

If you want to extend the time you have to work the epoxy, pour it out in a pan covered with foil. the thinner the epoxy, the more it stays cool. In a cup, it starts to heat up and can get pretty hot (as in melting the plastic cup). This accelerates the cure time. A thin layer stays cooler and takes longer to kick. It sounds backward, but epoxy works off of an exothermic reaction rather than evaporation (like paints and glues). Im sure you will get better answers from the pro's though!!

[DarrellS]

First thing is don't change the ratio of hardner.

As you squegee an area you can move it to another area.

With the slow mix you probably have in the neighborhood of 30 minutes to work it in this heat.

I would not mix two cups at once. The more epoxy that is in a container the quicker it will go off.

As for wetting out the glass, I just pick an end and get after it. Making sure it is wetted out before moving to next small area.

[gerald]

You're right. Brush, roll, just get it on there. All I do is make sure I have complete saturation. You can move it around if you want, but I think it is false economy to try to make your epoxy stretch.

You can squeegee immeadiately after you get the cloth saturated--especially if you're just trying to move it to cover a bare area. It's easier to wait awhile. If it's too runny it's hard to get off and into a waste cup. About like thick honey would be nice, so it adheres to the plastic squeegee but doesn't move the cloth. You have to use touch here.

I'm not understanding why you would apply cloth in strips unless you have a boat that's much too wide for the cloth you have. Except for specific engineering reasons I apply cloth over the whole boat, then saturate. You have plenty of time to wet out the boat. Once the epoxy is out of the cup and onto the boat it takes awhile to start setting. IN the cup it cures much quicker. I use a fairly large plastic bowl to mix in and only mix small batches at a time. Small is relative. If you are new at this you should start with very small batches until you learn what you can handle. I generally mix 8 to 9 oz. batches. Less, of course, when I need less.

No...it won't kick off on the boat before you are finished. It may start thickening in the cup. If it does--toss it. I can tell when it's going to start thickening. In that case I just pour it on the boat and spread it out. But...if it does start hardening I toss it.

The application technique is whatever works for you. Some people start at one end and work one way. I start in the middle, work out in narrow sections, and come back to fill in. Do what works! I like a 2" brush. I have tried ALL methods and come back to the brush--always. That may not be the best method for you or for others. Do what works for you!

Tumblehomes or a deck? We may need to define what these are at some time. If youre boat is sitting hull side up, you won't be able to reach what is underneath. In this case you would probably only apply cloth and resin down the the sheer. Later you would turn it over to do the top. I'm not sure that either I or you are understanding exactly what you are doing here. Usually you wouldn't even apply the "deck" or top portions until you have done the hull inside and out. Have you posted your plan? I'll have to look.

The amount of epoxy that you need is ENOUGH to completely saturate the cloth. There's a lot of differences of opinion here. Saturate the cloth--then go back over with a squeegee--several times--to remove the excess. Do not remove too much. The cloth should be filled and shiny--not dull and white. This is the most important step. Fill coats are easy. However you need enough fill coats to do the job. Differences of opinion here as well. Time between coats and mechanical versus chemical bonds, etc., are all subjective. You do what works.

There is no comparison between epoxy and polyester. After you get the epoxy on the boat, have squeegeed it, and are happy with the way everything is--go do something else. If you're using the slow stuff it'll be tomorrow before you can do anything. If you're using a faster mixture (which generally means a different hardener) you could do two coats a day. Just chill.....

Absolutely never change the ratio of resin to hardener in epoxy. Anything other than the correct ratio will give you a hard brittle composite, or a soft, rubbery one.

Did I cover everything?

Ah...ok, I've seen the boat. I would do the "hull" first, inside and out. Then add the "tumblehome" deck and do that with a little overlap on the hull. Alignment would be a problem though. You could put it all together and do it that way, but it would make doing the inside a little harder. Whatever works. I think you'll still be better off to do the hull, turn it over, and do the inside of the hull, then the last cloth strip for the "deck".

Is this your design or somebody else's?

[CoolfinIE]

Two other points:
1
If you pour the epoxy into a clean container, and then add the hardener, and then stir - what is in suspension is mix and will harden BUT the stuff that is in contact with the sides of the container IS NOT MIX and will take a month to set, because it's resin only. So never use the mix container to empty and then get tempted to wipe a final bit more off the sides and use that!
The preventative measure is to mix and stir in a deeper narrower container, where stirring is effective, (but a runaway set will surely occur if left there) then immediately pour all free mixed liquid onto a flat wide paint tray with polythene or tinfoil liner, or a paper plate, anything shallow, brush width, and with large cooling surface area. Every drop in the second container can be used.
2
Cover your work after wetting the cloth.
Use duct tape, or polythene plastic, or acetate (think flower shop!) because epoxy won't stick to these, and most of the advantages of vacuum bagging will be achieved, in this sense: covered cloth does not have all the epoxy sink down onto the wood, the capillary action under the plastic will hold an upper layer of epoxy above the cloth, making for a far smoother glassy surface after hardening, with much less (if any) ridging voids in the weave for later layers of glue to fill. Your epoxy cost will go down, and the finished weight will fall dramatically by covering prior to hardening.
I suggest making a "test card" with eg a foot of cloth on a wood offcut, epoxy it, leave one strip open to air, place a strip of duct tape on the next strip, a series of overlapping duct tape strips on the next, and place a strip cut from a clear polythene bag on the last. Later, observe the various finishes achieved.

[bowgarguide]

Zeke
I built a narrow version of that boat,and what worked well for me,stich everything including the tumblehomes. go ahead and apply your filets,inside and out,then apply at least one sheer strip to hold the shape on top.
I then flip the boat set two saw horses level put your boat on them then make sure there are no twist then glass away.
Ron

[bowgarguide]

Zeke
I think I figured out what I am going to do about the time deal on the epoxy drying ,I will just build two boats at once that should keep me busy.
Ron

[Pogo]

I agree with some of the stuff said here, and disagree with other comments, some almost violently. But I think the safest advice someone like me to give is for you to read every word on the subject you can stand, then go ahead and get after it and let the process teach YOU how it likes to be done in YOUR shop.

I've often said that half of learning to build boats is learning how to handle epoxy . . . and I half believe it.

I mix small batches, and spread it quickly, to avoid premature stiffening of goo. I use a brush and squeegee to apply it. Generally start at one end and work my way to the other while maintaining a generous wet edge with lotsa excursions from one side of the boat to the other.

[Light Keeper's Kid]

On the hull that tumbles home just like the wadefish hull the plans called to do one half with the hull tilted over so the fiberglass will not pull loose while your wetting out the glass on that side. Then when doing other half you overlap glass in center of hull and this also gives you two layers of glass down the center of hull for wear. I think this is what Texaszeke is worried about,I'm i correct But when i did this i had to tape cross supports in the areas that come in contact with the saw horses to keep hullpanels from flexing

Mike

[TexasZeke]

sheer, am I correct in thinking this is the edge where the side panel would join with the tumblehome panel?

thanks for of yall's ideas, plus I've got a couple more floating round in my head. How I end up doing it is probably a decision I end up making when I get ready to apply it. I have faith I will pick the wrong one...hehehe

[bowgarguide]

Might want to look at this ,it is my build on the regular T-V
http://www.neilbank.com/phpBB3/viewtopi ... =10&t=4347" onclick="window.open(this.href);return false;

Ron