Us composites epoxy 635 2:1

[gofly]

Hi there!
Does anyone have any experience with this epoxy?
I?m redoing my 18? bow rider and choose this resin for the stringers and transom. Already bought 7.5 gal of epoxy/hardener among other things from US Composites.

Everything was going smooth until I got to the point to start using the epoxy, but I?m having concerns now.
My transom is 2 inches thick so I glued two marine plywood together with epoxy, I first pre wet the wood and then glued them together with thickened epoxy, after two days the epoxy cured, but to my surprise it?s dry to the touch but soft, it feels like rubber!

It?s this normal? 5 days have gone now and still soft.

I have called the customer service and they said I?m not mixing it long enough and I need to mix it for at least 7 minutes!?..So I thought that was my mistake and did a couple test after that..

The samples are 3/8 thick by 3 to 5 inches in diameter. Only epoxy without any thickener nor fiberglass.
I?ve used the pumps on some and weight (1oo/46) the others.

The results were all of them cured after 2 days, but all are soft like rubber, the ones that I did remove the bubbles with a drier were a little harder than the others that I didn?t, but still soft, it bends and stretches a little too.
Is this normal? I have no experience with epoxy but I would expect a more brittle end material.

BTW I live in south Florida and that?s why I went with the 635/ 556 hardener (slow 2:1)
Anyone same problems?
Thanks

 

[Auger01]

Re: Us composites epoxy 635 2:1

I ave no experience with that particular epoxy, but that is not normal. I have used west system epoxy and system three silvertip epoxy and both cure hard as nails.

Here is a good souce for Epoxy in Florida. I have heard good things about thier house brand "marineepoxy", but I have not used it.

Boat Builder Central - products | Marine Epoxy | Fiberglass | Marine Plywood

 

[jbcurt00]

Re: Us composites epoxy 635 2:1

Many have used the USComp epoxy & I've never heard anyone of having any similar problems at all. Slow cure, but not 5+ days slow.

 

[jigngrub]

Re: Us composites epoxy 635 2:1

I think there's a reason they call it 635 2:1 SLOW, and I think you've found out what that reason is first hand.

Did you happen to see this note on the 2:1 heading?:

NOTE: Our slow hardener should only be used at temperatures above 80degrees unless an extremely long curing time is desired. Temperatures below 70F during the cure can result in a 2-3 day drying time

I'm pretty sure they're talking about a constant 80*F, not a high of 80's during the day and a low in the 60's or 70's at night.

Put your samples out in the hot sun for a day and see what they do.

I don't have any experience with the 635 2:1 slow, but I've used the 635 3:1 in 90*F+ heat and it still takes 3 or 4 hours to set and at least 12 hours to cure.

What was your filler/thickner of choice? S&M fairing compound, phenolic bubbles... something else?

 

[gofly]

Re: Us composites epoxy 635 2:1

Hi guys.

What was your filler/thickner of choice? S&M fairing compound, phenolic bubbles... something else?

I?m using Aerosil-Cabosil as filler (from US Composites), but was used only when I glued the transom plywood together.
The samples where just epoxy and let them cure in my house at constant 78 F.

I did a test with fiberglass tape (6oz) now, after almost 2 days it is hard and dry to the touch but I can still bend it in half without any cracking and the fiberglass separates at the very edge of the bending from the epoxy.

Since I have no experience with epoxy I bought one of these two parts epoxy ( 0.35 OZ 5 minutes dry 1:1) glue from the hardware store just to make a comparison test, so I can do a little fiberglass laminate with it.

Well, it dries hard as a rock and when I try to bend it you can hear it cracking until it cracks completely, the fiberglass itself gets cut in half, Which is what I would expect from the 635 epoxy.

I will do samples from different bottles now to discard the possibility of one of the epoxy/hardener bottle is bad.
Just don?t know what else I could be doing wrong :facepalm:. Maybe the slow cure is what is affecting is rigidity?

Thanks for your replies.

 

[jigngrub]

Re: Us composites epoxy 635 2:1

Put all of the 2:1 mix pieces outside in the sun for a day and see what happens, I'll bet it hardens up nicely.

 

[lokonn]

Re: Us composites epoxy 635 2:1

Trust what Jig tells you. I used the 3 to 1 635 and needed to add halogen lights for extra heat. I also think I remeber reading in US Composites FAQs that their epoxy is more flexible than you would expect when using with glass. Might be wrong but worth looking at their site. Good luck.

 

[gofly]

Re: Us composites epoxy 635 2:1

Hi jigngrub
We have had miserable weather for the last two weeks, raining every day two or three times a day here in south Fl.

I will try that as soon as the weather clears up, however I did put the softest sample that I have under a lamp for about 12 hs, it softens immediately under the heat but once it?s removed from the lamp and cools down, it comes back to its initial state, not even a bit harder than it was before.???

By now I have put 6 more samples:

I have purged the pumps and changed bottles.

1. 3 layers of epoxy/fiberglass and heated for 5 minutes with a air drier (mixed epoxy for 7 minutes before apply) using pumps 2:1

2. 3 layers of epoxy/fiberglass (mixed epoxy for 7 minutes before apply) using pumps 2:1

3. 3 layers of epoxy/fiberglass (mixed epoxy for 7 minutes before apply) using pumps 2:1 left this sample outside to see how high humidity will affect it.

4. 3 layers of epoxy/fiberglass (mixed epoxy for 7 minutes before apply) using pumps 2:1 and placed under a heating lamp (will leave it there for 24hs.)

5. Just epoxy alone 50 ml sample ? 7 minutes mix ? then air drier (to get bubbles out 5 minutes)

6. Just epoxy alone 50 ml sample ? 7 minutes mix ? (at this point 1.5 hs later (2:20 pm) this sample has not even get warm nor exothermic reaction yet ??????

The samples were made at 12:40 pm today, will let them cure for 24 hs and see what happens
The reason what I?m using air drier on some samples is that I?ve used that before on some samples and they are the ones that got harder after cured, so I?m trying to replicate the results.

Thanks

 

[gofly]

Re: Us composites epoxy 635 2:1

Hi lokonn

I also think I remember reading in US Composites FAQs that their epoxy is more flexible than you would expect when using with glass

I just found that from Us Comp:facepalm:.

The (2:1)#556 slow hardener is meant for tropical conditions(above 80 degrees). This hardener also cures as the most flexible laminate.

Didn't read that before, I have chosen this 2:1 kit as is what they recommend for high humidity and temp places.
Do you think it would work for my stringers/transom or it will be too soft?

Thanks for your reply/help

 

[lokonn]

Re: Us composites epoxy 635 2:1

Hi lokonn



I just found that from Us Comp:facepalm:.



Didn't read that before, I have chosen this 2:1 kit as is what they recommend for high humidity and temp places.
Do you think it would work for my stringers/transom or it will be too soft?

Thanks for your reply/help

Wish I could answer that for you, but as of now I am a tin guy. I'm sure someone with glass expierence will get you an answer. I'm using the epoxy to seal the plywood for my transom and floors.

 

[gofly]

Re: Us composites epoxy 635 2:1

Hi all

I’ve called US composites today, after I finally have convinced myself that the slow hardener is what is making the samples too soft.
All the test samples that I did end up cured but very soft, the ones that air dried for 5 minutes are a bit harder but not near as hard as I would expect, I have some old poly tabs that I’ve chiseled out of the hull and they are noticeable harder/stiffer.

So.. the guy from US Comp. now told me that the SLOW hardener is NOT recommended for stringer/transom repair due to its flexibility and he recommended me to buy the medium hardener 3:1. and work with that one.

Their website is a little confusing for a new boater like me, they recommend the 635 resin for fiberglass lamination, and then say to choose your hardener based on your TEMPERATURE, curing thickness, working time and drying time…..but nothing about stiffness. However they do say that on the F.A.Q. link.

Not blaming it on them, but if you are a newbie like me and happens to read this post DON’T DO THE SAME MISTAKE I DID, order the 3:1 Medium hardener even if you are in a very humid and hot place like me.

Thanks