Board Bow limb profile suggestions?

[TomBow]

After my 4 fails, I have read extensively TBB I and The Bent Stick and am ready to start the prep work on my 5th try.  Having just a bit of unsurety concerning limb shape and bow dimensions.  I would like 50-55 lbs @28, 64" bow and may go hickory for a core and will back it with HD Fiberglass tape, 2 layers.  Would 2" limbs, rectangular limb profile provide me with a likelihood of success?  Where should I begin tapering from 2" to 1/2" tips, or should tips be smaller?  I believe that I have been creating too-round bellies on my limbs which have concentrated too much stress.  Any suggesions and/or point in the right direction on the above would be greatly appreciated.  Thanks.

[Pat B]

Why did your other board bows break? Do you have any pics of their breaks?
 I don't think the bow shapes have much to do with why the break. Just guessing and having never seen the breaks I'd venture to say it was probably grain runoffs. Properly selected boards are your first step in making a successful bow. FG tape or any other backing will not make a poor bow stave into a good bow.

[Roy from Pa]

Here ya go, Tommy ole boy..  

 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=000122

[Pat B]

That is an excellent build along but I don't doubt it coming from 4est. Thanks for posting it Roy.

[Ice Mike]

I have also broke a TON of boards and can feel your pain.

As was stated, grain selection is ESSENTIAL. Also, I would go with 1.5" width on hickory and taper to .5 at tips starting from about mid limb. Thickness should start at about 5/8" at the fades and taper to about 3/8" at the tips. This will give you plenty of room to tiller on the belly to get where you're trying to go. Also, put the backing on before you start tillering. You may be able to start your thickness a little thinner beings you will use two layers of glass tape on the backing, due a more experienced bowyer than me will havee to chime in on that.

Good luck with it and have fun!

[takefive]

Two inches is plenty wide for a good hickory board.  I'd suggest going longer than 64" though.  66" to 68" would be better unless you have a short draw.  4est's pyramid bow build along is a good one and that profile makes tillering simpler, but if you want to make a flatbow with rectangular limbs, have at it.  If you run into some problems along the way, post pictures and someone will be glad to help.  I agree with keeping the belly flat.  Make sure to sand the edges of the limbs to round them off, though.
Good luck!

[takefive]

Actually, if your hickory board has reasonably straight grain, I wouldn't back it at all.  I back most of my board bows with hickory that is less than perfect.  It is some tough stuff and can handle some degree of grain violation.

[TomBow]

I have no doubt that grain had something to do with the fails, but overstressing too early in the process was also another reason.  I picked the best=grained boards I could find but still got runoffs just above and below the handle sections which were composed of a 1/8 layer of mahogany and 3/4" hickory, worked down into a handle with a shelf.  I have seen and followed the above build along, although I did shorten the bow from 68" to about 65" and tapered from the fades.

[takefive]

That's a good point about avoiding stressing the wood early or at any time during the process.  Even if it holds together, you risk excessive set in the limbs.  These days I draw the bow to just a few pounds under the weight I want on the tillering tree and take it off the tree when I'm 2 inches shy of my DL.  Makes the process a bit longer, but I think it helps keep set low.  Only other thing I can suggest is to make sure you still have safe width on your handle where you cut the shelf in.  I've heard that mahogany is brittle, but don't know if just an 1/8" in the handle would cause a problem.

[TomBow]

I sandwiched the mahogany between 3/4" hickory, then worked the handle down to about an inch wide at the throat.  Should be plenty of wood there, shelf was cut in to an 1/8" outside of center.  Glue ups have gone well.  So far I am making good looking but ultimately failing bows.  I have had set in all tries, except for the first attempt which I glued into about a 2" reflex.  The limbs were firm on that one due to bamboo flooring (ultimately WAY too much thickness for the wood) with the reflexes holding position well but stupid guy over here decided "Oh, I'll string it up with too short of a string".  Chalk it up to my first experience with exploding wood as the maple/bamboo upper limb lost about 10" total length when the tip broke right off.  Yes, yes, yes, not breakin' bows?/not makin'bows! so I've heard. And now experienced.  It's funny when you take the time to actually READ experienced bowyers' "What NOT to do's", rather then trying to go it uneducated and seat o the pants, that you find out uh what..not..to do.  
Gotta say it's been alot of fun making sawdust in the garage.