Epoxy cure time

[DC]

I use cabosil with the 105/205.
 Since I was going to leave it sit for a couple of days I reverse braced it a little bit. Not much. When I unbraced it this morning it had gained 1/4" reflex. Whether this has anything to do with the epoxy creeping or if t would have happened anyway I don't know. I'll recheck it after the shop warms up and I finish my coffee.

[DLH]

Do you think there is any “work” being done by the glue line? Does a strong bond at the glue line have potential to reduce stress of the wood and carry some of the load instead? The SDS of most of these epoxies seem like a simple bishenol a or f epoxy. Might be interesting for someone to explore higher Tg epoxies or higher temp cure schedules. The higher Tg epoxies can boost modulus/stiffness might require less wood to hit target weight. This is loosely looking at some information through an epoxy supplier. Mostly blowing smoke here but polymers interest me and I doubt anyone has explored this. Not sure about the origins of smooth on but I think a top tier bowyer and a epoxy chemist/engineer collaboration could have potential for a optimized bow glue or there might not be a big enough difference to discern.

[PatM]

The glueline isn't thick enough to be stiff by itself.   It does come down to locking things in place.

 Apparently quite a few bowyers have switched to a "better"  epoxy.

 I actually have an epoxy on hand similar to West that has double the strength numbers more or less.

[willie]

how strong is that Pat and what is it?  I work with system 3 because it is available locally, and noticed (when I looked last), that their products using thickeners were proportionately reduced in strength with the amount of additives used.. I use heat or cold to modify viscosity to my benefit when gluing up, rather than adding more cabosil than needed

[PatM]

It's called Poly Epoxy.

 Try the Gel Magic from System Three.  It's great stuff.

[HH~]

Huntsman epoxy. Made specifically for wood lamination. Has A LONG pot time and cures over night. Best stuff I have ever used.

Had a billet bow where the billet joint held and the Osage failed (violently at 75lbs of string weight) before the glue joint. So, I put it all back together with Huntsman. Its 42@28lbs and the Wrecking Bow was born. That glue joint and repair is prolly stronger than the Osage was.

Like the color of this epoxy when dry as well.

HH~

[buddyb]

Hedgehunter, do you use heat or let it cure at room temperture?

Buddy

[HH~]

If your going to have finished product over 100 degrees i would warm up your work. For wood to wood contact i just warm up my glue. This type epoxy is best used with laminating. I do use it for splicing but I let it cook off a bit after wetting all surfaces with epoxy.  It will fill gaps better when it stiffens a bit.
I have had wood fail before a glueline with this stuff.

Hedge~

[buddyb]

This Huntsman epoxy is the TDR 1100-11 Resin and hardener correct?

[HH~]

Yes
You cam lam without roughing wood to the degree you need to with EA40. You roll it on with small dia roller. Comes out slick as owl snot. I love the stuff.

HH~

[buddyb]

I want to make an all wood longbow and don't want to use a heat source, similar to a trilam. If Huntsman fills that bill then I'll order some.

Buddy

[stationlunda]

This is an old post, but I don´t find any answers in this post, so I thought I would make a reply here...

The question of epoxy and its curing time is not simple. Despite what manufacturers like West System tell us about the curing time during different temperature conditions, it is not really true. All epoxies I have used will actually continue to harden for several weeks. With bow making, I have found the problem with West System 105/206 that it is getting too brittle during the time and it cracks like glass. For a bow, this can show up as a sudden break of the bow after weeks of use!
  I have used Wests G-flex, and it is flexible the first days, but also this epoxy become rather brittle after a longer time...
  As bending a bow creates a tremendous stress on the wood lamination and exoxy, I suggest that you wait at least 4 days with the bow in room temperature before you start to tiller it. Althoug increased heat may reduce the time, it may also reduce the quality of the epoxy, which might become more brittle...
  All this is said by many years of use with many kinds of epoxy...

[bownarra]

Yes
You cam lam without roughing wood to the degree you need to with EA40. You roll it on with small dia roller. Comes out slick as owl snot. I love the stuff.

HH~

Smooth-On recommend sanding to 120 grit with EA40. Most people go a bit coarser but 120 is what is recommended. I have never roughed up the lams before using EA40 and wouldn't recommend it!
stationlunda - good info!

[PlanB]

As a long time user of WEST system products (since early 70's as a professional boatbuilder) I'd have no hesitation using their epoxy in laminating a bow. BUT you do have to understand the products and specifics of application. I strongly recommend downloading reading the free 400 page book "Gougeon Brothers on Boat Construction", my old paper copy is from 1979.

20,000 pound ocean racers and 60 mph DN racing iceboats owe nothing to a laminated self bow in terms of "tremendous stress". And many of the more famous of these racers built by the Gougeons are still performing 50 years later. I don't think laminate epoxy aging is a factor for these, and they have been subjected to a lot worse conditions of moisture, and impact, etc. than a bow ever is.

[PlanB]

I think also of interest to us for all glue types:

http://www.oldbrownglue.com/images/articles/HowStrongisYourGlue_FWW.pdf