Fiberglass resin backing

[gobbler716]

I am building a board bow of red oak.  In needing some backing, I saw some were using this and that.  My question is: will fiberglass resin & hardener work well as backing on a 68" longbow, or do I really need some sort of fabric?   :confused:

[inksoup]

i think i will work.
at the moment i am trying this way and i will get some results in short time. if you can wait some more time, i can share the info.
only think that you need to be careful about, resin should be as little as possible since i can crack or break. at least fiberglass people said like that.

best.

[Trad Dad]

I think it was Sam Harper that told me once that it works well but don't use the resin at the auto parts store. I think he recommended using a resin for marine use.

[monterey]

I did one usng hobby glue 50/50 mix and some auto repair fiberglass matt.  Results were good.  The matt would not add that much extra weight to the limbs so might be a good idea for that extra margin of safety.

[inksoup]

oh yes, forget to say, yes use marine ones. since they are thinner and elastic than others.

up to now it is ok.

i will share the results soon.

[gobbler716]

Thanks guys!

[gringol]

I've used the fiberglass matting before and it worked, but made the bow super slow.  With the woven matt you have twice as much material as you actually need, because you really only need the fibers in the longitudinal direction.  All the lateral fibers are just dead weight.  

I've never tried the resin by itself.

[Pat B]

I would think that polyester resin would be too brittle to use as a backing. The matrix of the resin and cloth is what makes FG strong. Also, FG might overpower the red oak belly. A hickory or maple backing would be more appropriate for red oak.

[dfrois]

In my (limited) experience, polyester resin is no good for this, because it has very little flexibility once cured. You would be better off using epoxy resin, preferably of the kind that is used to make laminated fiberglass bows (which is what I use it for, with good results...so far!). Also, the point on longitudinal vs. transverse fibers is a good one. You only need the longitudinal fibers, and using a mat of any kind means using a lot of unecessary fibers, just adding weight. Glass is very heavy per volume, as is resin, which is probably why the fiberglass matted bow was sluggish...just MHO.

Good luck. DF

[fujimo]

uni directional tape 2" wide can be purchased- it is simply longitudinal fibers stitched cross wise  along the length of the tape. certinally use an epoxy- you will find both polester and vinylester too brittle.
       http://www.aircraftspruce.ca/catalog/cmpages/unitape.php      

and here is some stuff that is backed with a scrim
      http://www.freemansupply.com/FiberglassTape.htm    
uni directional material will utilise a lot less resin- the resin is the weak link in the equation. vacuume bagging is the real answer here- to get the max glass to resin ratio. i did read a post somehere of a guy who vacuume bagged a bow with his food processing vac bagger- sounds like a reasonable idea- worth trying-

but hear what Pat B says about backings overpowering bellies- he knows his stuff.
 
what about a silk or linen or even butcher paper backing. i have used silk a few times- it is awesome- hardly adds any weight to the bow- easy to work with- just used titebond 3, no mess no smell- cheap, and sometimes free- i am sure your wife will not miss a 2" strip down the side of those fancy sheets     :D     .
not against fiberglass- in fact quite a proponent for its uses however- like all materials they have their place where their properties are best utilised. just my thoughts for a penny!
whichever way you go- good luck - and show us some pics!!    

[truman]

This is great information I ordered some plans from Bingham's  and plan on building the 64" reflex deflex longbow but I will try a board bow first.  right now I have to finish getting my kids skating rink ready or I will never have peace LOL

[gobbler716]

Buy epoxy resin where?

[Schmidtster]

I did a Red oak long bow and backed it with fibreglass cloth I got from home depot and used regular old wood glue to glue it on and it worked good for me, shoots pretty good, no speed demon but it gets them away pretty decent.

[gobbler716]

The one I bought is 3M, fiberglass resin.  According to the instructions, it is for boat repairs....with the glass cloth.  I will use the glass cloth I bought for something else.  Since this is my first try, I think I'll try it out.  I have other new red oak boards that are sitting and waiting to become bows.

[milehi101]

I have used West systems Epoxy for years and used it to back bows with the 2 inch tape.  Be sure you get the slow dry hardener so you have plenty of working time and it has more time to penetrate the wood