West Systems Epoxy

[arachnid]

Hi all.

Has anyone used West Systems epoxy 105&205 for fiberglass laminated bows? I can't get Smooth on but I can get West.

[monterey]

I used it once at the behest of a non bowyer who had the idea of "licensing" the product for bow building.  Now, I don't know anything about that process, but I agreed to build the bow with him agreeing to provide the epoxy and paying for the build.

I don't recall the 105 or 205 designations. It was the same stuff that boat builders use.

I layed everything out and prepped for the layup
Mixed the epoxy in a plastic tub. The build was an ASL with glass back and belly and four maple lams.  It was a proven design so as to be working with the glue as the only new variable.

About 2/3 of the way thru the lay up I noticed the glue in the tub smoking.   :confused:   it was getting very hot:scared:  the glue on the lams was not hot, probably due to being less in mass and therefore affecting the reaction less.

I turned up the hustle and got the bow layed up in record time.  I was sweating bullets as the hose inflated.  No hot box used, just left it to cure for a day.  By the time the hose was inflated, the remaining glue had gotten hot enough to melt the plastic tub and was a fast hardening lump.

So I finished the bow and shot it for a few weeks without any problems.  It functioned as well as any other and came in at the targeted 50#.

I advised the fellow it was not suitable for use for bow building due to the very short pot life.  He reported a few months later that the bow had broken while his brother was stringing it.  No other details offered on his part.  The glass was Brown so if there were problems in the glue up they could not Be seen under the glass.  The glue lines looked fine.

So, I never used it again and the above related experience is fair warning!

[die_dunkelheit]

Originally posted by monterey:
I used it once at the behest of a non bowyer who had the idea of "licensing" the product for bow building.  Now, I don't know anything about that process, but I agreed to build the bow with him agreeing to provide the epoxy and paying for the build.

I don't recall the 105 or 205 designations. It was the same stuff that boat builders use.

I layed everything out and prepped for the layup
Mixed the epoxy in a plastic tub. The build was an ASL with glass back and belly and four maple lams.  It was a proven design so as to be working with the glue as the only new variable.

About 2/3 of the way thru the lay up I noticed the glue in the tub smoking.    :confused:    it was getting very hot:scared:  the glue on the lams was not hot, probably due to being less in mass and therefore affecting the reaction less.

I turned up the hustle and got the bow layed up in record time.  I was sweating bullets as the hose inflated.  No hot box used, just left it to cure for a day.  By the time the hose was inflated, the remaining glue had gotten hot enough to melt the plastic tub and was a fast hardening lump.

So I finished the bow and shot it for a few weeks without any problems.  It functioned as well as any other and came in at the targeted 50#.

I advised the fellow it was not suitable for use for bow building due to the very short pot life.  He reported a few months later that the bow had broken while his brother was stringing it.  No other details offered on his part.  The glass was Brown so if there were problems in the glue up they could not Be seen under the glass.  The glue lines looked fine.

So, I never used it again and the above related experience is fair warning!

:eek:  
I have used West Systems extensively, the ONLY way to get that kind of reaction out of it is to mix it 1:1, or a otherwise hardener rich mixture (105 resin:205 hardener for example is 5:1 by weight).
A hardener rich mixture could also explain the failure so soon after. Yeah, West Systems is not formulated as a bow making epoxy, but if you call them they still maintain that a "major" US bow manufacturer uses it. From my experience dealing with them they are not one to steer you wrong even if it means tell you that their product(s) aren't best for your project. Also, from my experience dealing with the epoxy and observing it's characteristics, I think it should work fine in a bow.

[Msturm]

[mikkekeswick]

Yes sounds like a hardener rich mixture?
One of my friends has used it quite a bit - no problems.

[monterey]

It was far too long ago for me to recall the ratios.  I would have followed directions for the product, But the directions may have been for a whole different application/use of the glue.

Also, I'm not pointing to the glue in reference to the break.  The fact that it broke while stringing it opens up a whole set of possibilities.

Wonder who is the major bowyer using it?

[die_dunkelheit]

Originally posted by monterey:
It was far too long ago for me to recall the ratios.  I would have followed directions for the product, But the directions may have been for a whole different application/use of the glue.

Also, I'm not pointing to the glue in reference to the break.  The fact that it broke while stringing it opens up a whole set of possibilities.

Wonder who is the major bowyer using it?

Don't know, though they are friendly and open with their knowledge they are closed very tight with customer information, just as we hope every company would be.

I totally missed that it occurred while stringing it, let alone while someone else was stringing it. It very well could have been a step-through gone wrong.

[Mark R]

I have used West System G Flex epoxy on one bow I made years ago using some left over material, (glass laminated) it shoots great, its been pulled past 30" many times and I'm still waiting for it to break. Its a short hybred and is showing signs of stress on the belly fades but I don't think its an epoxy issue more of an experiment design issue I was playing with, with that being said I only use smooth on because its proven and available to me. If you can't get smooth on and nothing suitable is available and you can get west system G Flex epoxy try it.

[monterey]

What is the character of the Gflex?

[arachnid]

I can`t get G-Flex, only 105+205

IMO... The epoxy heating up is not from extra hardner...  You just reached and went over the pot-life of the product... That's why they make slower hardners to give you a longer pot life...  Smooth-on is unusual in the fact that you can add more resin for a stronger bond... Most all other epoxies need exact measurements or their properties will be compromised... Polyester resin on the other hand will speed up pot life by putting more hardner in it... A good example is if you ever worked with bondo...
  Different Epoxies have different qualities...  Some are specifically made for wetting out and laminating fiberglass and such and others are made to be adhesive like ea-40...  
   I would research it and or contact the Gougeon brothers and tell him what you want to do...  I talked to one of the brothers years ago when I was building sailboards...  Nice Guy and full of knowledge...  He may tell you to put in an additive  such as Cabosil, talc or milled fiber for better bonding...  
   You also may want to do some tests first before using it... Try some at room temp. cured and some at oven cured...

   Good luck...  Let us know how you make out...

 http://www.westsystem.com/ss/filler-selection-guide/

 http://www.vansairforce.com/community/showthread.php?t=41047

[arachnid]

I actually checked and the prices for West are pretty high here. I'm checking out an epoxy called "Biresin cr80" made by a german company called Sika. I asked about it here some time ago and didn't got a clear answer since no one here ever used it. I was told on PA that any epoxy made by a good manufacturer will be good for bow making.

[Ringbill]

I have used West system for building boats as well as Raka and US Composites. I have had the fast hardener smoke and melt the cup it was mixed in and it was measured by weight. This has happened a couples time when I mixed to much and was done with it and just let it sit there on the bench. The epoxy will generate heat during the curing reaction and this will just speed up the curing process. One way to counteract this is to spread out the epoxy after it is mixed in a small paint tray. Usually I just make a tray out of foil. This allows the heat to dissipate giving you a longer pot life. I have only built all wood bows so have not used epoxy yet in bow building.

2nd that,   About spreading it out in a larger pan...  Also working in a little cooler temperature... Or keeping your epoxy cool but not cold enough that you risk the chance of attracting moisture because of sweating...

[Roy from Pa]

This is why I like smooth on.

arachnid , hope you finsd a solultion.

[die_dunkelheit]

Originally posted by Ringbill:
I have used West system for building boats as well as Raka and US Composites. I have had the fast hardener smoke and melt the cup it was mixed in and it was measured by weight. This has happened a couples time when I mixed to much and was done with it and just let it sit there on the bench. The epoxy will generate heat during the curing reaction and this will just speed up the curing process. One way to counteract this is to spread out the epoxy after it is mixed in a small paint tray. Usually I just make a tray out of foil. This allows the heat to dissipate giving you a longer pot life. I have only built all wood bows so have not used epoxy yet in bow building.

Funny...
My first BIG project with epoxy was some major boat repairs and I did it with west systems. Before the project I read their book "The Gougeon Brothers on Boat Construction" because then, and still today, I'd really like to cold mold a 40 or so footer and even have plans for a small 11' sailboat I'll be cold molding. In the book they make some good points about spreading it for longer pot life. I didn't even think about that as a possible issue simply because since then I've always done it when I'm using enough epoxy to worry about. Funny how through projection we assume certain things about how someone else is doing something.

[monterey]

I can see that the spreading would have helped and I also mixed far more than needed for the project which made for a good sized mass in the mixing tub.