Fiberglass on just one side?

[Bradford]

Hey all.  With Christmas just around the corner I have just enough time to build some bows for the kids for christmas.  In the interest of saving time and money, is using one fiberglass lam on the back good enough?

I have built all my take down recurves with glass both back and belly.. and all work well.  But reading post on here and thinking on things, I am thinking that for the younger kids, where the pounds will only be around 15 or so, that fiberglass on the back and a solid piece of maple for the belly.

What are your thoughts.. Thanks!

[Pat B]

Adding glass to one side of the bow is, IMO, not a good idea. With a kids bow with low poundage it is probably not necessary to have a backing at all but if you want one silk, linen or brown bag paper works well and would be plenty sufficient for these light weight bows.

[Swissbow]

I agree with Pat that for a kids bow you probably don't need a glass for backing. If you want a heavier bow it can be done only with glass on the back, but you have to use wood that can take the stress otherwise it will be overpowered.

Phil and I have made bows like this dude shows in that video and they turned out well...

 

Instead of pretillered board we took a board about half an inch thick glued a riser on it and glued it the way he shows in that video. After it's cured you have to tiller it on the belly and you have a bow.

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Andy

[Bradford]

Okay.. Thought of that.  But why not a "good" idea??.. just because you don't need it, or will there be a problem that you can think of.

I also have some Hickory that is straight grain that I could use, but I know my kids.. If it gets left outside on rainy day, or gets used as a sword.... thinking that the fiberglass will just help it out.

[jess stuart]

I am, and have built several low poundage kids bows using only one strip of glass.  I use a two inch strip and split into two one inch wide strips one for the back and one for the belly.  They have lasted well and the kids really enjoy them and they are only half the cost in materials.

[Bradford]

Okay.. good deal.  Will give it a try.  I already made a form for a one piece recurve that is 48" knock to knock.  Figured I would do a lam of maple, the riser block then the fiberglass.
Everything is set at an 1 1/2", but figured I would tiller down the sides till it was in the poundage area.

I guess we shall see.  I might try one with Maple, riser, Hickory and see what happens.. be cheap enough.

I have not yet tried a board bow... everything I have is set up for laminations.  Will try a board some day down the road.

[Bradford]

I like that video.. thanks for the link.  I am already seeing ways to expand on that and make it really cool.... hehehe.. I just can not leave well enough alone.

[ChristopherO]

Bradford,
The "But why not a "good" idea??.. " is because the fiberglass can overpower the belly if only the back is glassed.  If you think the kids will leave it outside or keep it strung all the time then you are better off glassing both belly and back, any way.  Hope it all turns out well.

[Bradford]

I guess I am having a hard time understanding this.  Overpower??  So what will that feel like?.. to hard to pull or to much spring in the release?

Just getting all my info together.

Thanks everyone for your 2 cents.. keep it coming.

[Saskquach]

What is meant by "overpower" is the wood on the belly, if the fiberglass is on the back, will be under extreme compression when drawn. The possibility is the wood will fail. You will see lines across the belly where the cells in the wood have collapsed. At that point those cells no longer store energy or support the shape of the bow. I don't no if I am explaining it totally correct but I learned from experience. I needed a bow for an upcoming hunt and all I had was one piece of glass and some walnut. It made a beautiful R/D longbow. It got me through the hunt but afterwards I noticed the lines across the belly above the fades. The bow had lost about five pounds of draw weight. I tried to save the bow by tapering the limbs and adding a glass layer to the belly but it eventually failed just above the fades.

Had fun doing the build and learned a bunch the hard way so all was not lost.

Dean

Dean

[Pat B]

The wood cells in the belly of the bow will be crushed by the tension strong fiberglass backing. The lines that Dean was talking about are called Frets or chrysals; ie. compression fractures. Excessive set is also a sign.
 The back of a drawn bow is in tension and the belly of the bow is in compression. Making a bow where these opposing stresses are compatible is what we are all trying to do.

[Bradford]

okay.. that helps.  Thanks.  That is why it is recommended just to do a backing.  Not adding much in weight, but not allowing splinters.

I just need to learn how to make my own fiberglass.  Getting tired of paying so much money for the glass.  My mind tells me.."it's just fiberglass".. Exotic wood is fine to spend some cash, but it kills me to spend 15 to 20 bucks per glass.

Thanks for everyone's input.  Great to be able to learn from everyone else instead of my own mistakes when possible.

[JamesV]

Bradford, I have built several kids bow that turned out really nice with .030 glass on the back and IPE for the core or belly. The IPE is strong in compression. I also split 2 inch glass to save money and it would be possible to build one and one half all glass bows from one piece of glass, if not over 48".

[Bradford]

Thanks.. I never thought about only making 1" bows.. I made my form and everything for 1 1/2".. but that is a great idea.  So will re-arrange my goodies for 1".

I know I saw at some time a way to make my own fiberglass lams.  But can not seem to find it.  It might have been on the other bowyer forum that went down about a year ago.  I would love to make my own, so I can make the colors I want and sizes I want.

Thanks all!