Osage board bow layout question

[razorsharptokill]

I have made a BBO bow before but it was with a parallel and a taper lamination as in Wingnuts "Hunter" design. I haven't attempted a backed board bow yet and have some questions.

I have a quarter sawn osage board 72" x 7/8" thick x 1 1/2" wide. Here is how I have layed out the bow, tell me what if anything I should change. This is all still drawn in pencil, no cuts made yet. I want a 55lb at 28" bow.

I went out past the fades 13" and tapered from there to 5/8" tips(for now). So the limbs are parallel for 13" then start their width taper to the tips. Should I taper from the fades instead?

Also I made one limb an inch longer(34") than the other(33") intending it to be my top limb. The bow is laid out to be 67 tip to tip. These measurments are from the center of the handle.

I intend on hickory or bamboo backing this bow. I plan on cutting the limb width tapers before I apply the backing. I want to introduce some reflex before I glue the backing on, how much should I thin the belly down to heat bend the reflex in? I was thinking 3/8" thick at the tips?

For the handle I have several types of hard wood available. I want a stiff handled bow. Should I cut the handle material into thinner strips to help prevent it from popping off? I plan on using TBIII for the backing and handle.

[Pat B]

At 7/8" thick you won't need much more thickness to make a handle. Another 1/2" is all you will need.
  I generally take the belly down to floor tiller stage(4" of tip movement)with a good even bend in each limb. This will give your reflex a good even bend on each limb. I never measure but take enough wood off to accomplish this.
  Is there a reason you are making this bow 67" long? 62" to 64" is plenty for a 28" bow. Also I would go out parallel for 6" to 8" before tapering to the tips.

[razorsharptokill]

That's just how it ended up. I was 33" to each tip but then decided to have one limb longer for tiller. I like a 64" bow, I guess I'll go 31.5 and 32.5. or is it really needed to have top limb longer?
So on the taper... are you saying only go 6-8 inches from the fade before tapering to the tips as opposed to my 13"?

[walkabout]

i started building all my bows with a longer top limb to help keep some stress off the bottom limb and put the arrow closer to center. they dont really suffer any from it that i know. also i taper my limbs from about 1 inch or so past midlimb, i've found that if i taper from the fades or close its similar to the pyramid design and can get scary thin, not leaving much room for error. tips i leave 3/8 inch thick and 1/2 inch wide till final stage then i take off some width till im a little over 3/8" wide or satisfied with it.handle shouldn,t really pop off unless you get a bad glue up or if you overscrape right close to the fades and it bends alot. one thing i have found about asymetrical tillered bows is that depending on the handle layout they can prefer a more loose two finger grip than a full hand tight grip. keep us posted on how it turns out

[John Scifres]

I think I'd do like Pat said and shorten the full width to maybe 6".  I also think you are wise to shorten a couple inches.  All the osage bows I have made longer than 65" had more handshock than I wanted.

[Pat B]

Richard, If you find your limbs getting to thin start scraping wood from the sides and reduce the weight as you reduce the width instead of the thickness.

[razorsharptokill]

John,  you mean shorten full length  by 6" right? Walkabout, by 3/8" do you mean at the string grooves?

I'll go for 64" with top limb being 32.5 and lower limb being 31.5

[walkabout]

yea i keep the limb 3/8" thick at about 5 inches of the tip so i can take width off later to reduce handshock. pat thanks for the advice, that makes alot of sense,a example of the width to strength ratio, from what i know width is easier to work with than thickness sometimes.

[razorsharptokill]

Got it trimmed down to length and cut the width tapers today. Worked out good the piece I cut off should be perfect for a handle.

[John Scifres]

Here is what I'd recommend for the dimensions:

Length:  62-64" nock to nock, top limb 1-1/2" longer than bottom

Width:  1-1/4" from fade to 6" past fade, tapering to 1/2" nocks.  After final tillering, you can narrow these to 3/8".

I know it's too late for this one but I would also recommend that you cut your profile on your backing first and then glue it up to a slightly thickness (NOT WIDTH) tapered slat.  Thickness is the back-to-belly distance.  Width is the side to side distance.

If you're doing bamboo, you almost have to do it this way or your bamboo will be too thick at the tips.  I highly recommend you get Dean Torges' "Hunting the Bamboo Backed Bow" video.  It'll save you some of the frustration.

[razorsharptokill]

John, is that to aid in the glue up and inducing reflex? I always taper my boo for thickness at the ends.

If I glue the profiled backing on before I re-taper from 6" past the fades, I should have an easier go on the glue up.

Thanks for clearing that up for me.

[Steve Kendrot]

Jim. Tapering the thickness of the limbs before glue up helps retain the reflex deflex design. I forgot this step on one of my bows and it did not take the shape out of the form that others with tapered limbs did.  As John suggested it's a whole lot easier to cut the back to shape, taper it and glue it to the uncut board and then trim the board to the backing. The Torges video is a must buy if you are making a bbo. I just finished one I've had in the hopper for nearly a year tonight. 64"NTN 55#@29". Finally got to tillering it.

[razorsharptokill]

Makes perfect sense.