Short D bow question (birch D bow buildalong)

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I want to make a D bow as written in TBB v.4. I'm using birch. Perhaps silver, but more possibly, some local specie/subspecie (in Russia, Ural) I can't even find a description of. My arm span is 70 inches. Draw length is 28" (perhaps a little over, since I use the "thumb draw") If I make the bow 66 inches long, will it blow? The limbs should be wider? If so, by how much? I am aiming for 45 lb. draw weight.

[Parnell]

You are in the Urals of Russia?

I don't have experience with birch but remember reading of it being used.  I've just been given this resource, perhaps it will be helpful for you...wood-database.com

It looks like Silver Birch comes in around .5-.6 for specific gravity.  66" is long especially if you are going to make it bending through the handle.  For considering a 29" draw I don't see why you couldn't go 62" long without trouble.  If it were me, I'd consider a wider limb at 1 5/8" or 1 3/4" and narrow the grip a bit...leaving it slightly bulbous but bending.  Heat treat the wood, I'd figure...

Hopefully people with experience will chime in.  Good luck.

P.s. Even at 60" of length...I wouldn't call it a short bow.

[simk]

i just did a bow of silver birch, which commonly is not said to be a very snappy and compression-tolerant bow wood. It is 64" with stiff handle and about 45#. I did heavy heat treating which seems to help for the doubtful compression ability and snappyness. a bendy handle should be possible @ 60-62". But do heat treat the belly, build wide and take care about the transitions at the grip whre it maybe should a little narrower for comfort. 2 pennies from me

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Parnell,
yes, I live there. In the city. But for summer I live in rural area. There's not much bow woods. Birch, which is plentiful, GIANT larch trees I would like to turn into 100+ staves  And some other tree I cannot identify, with almost black, scaly bark. Perhaps it's ash. I would look into that. I want the handle to bend only slightly.

So a bendy handle permits the bow to be made shorter than the flatbow of similar draw weight and length? If this is true, I would start making just D bows. My first bow (finished a couple of weeks before), of birch, was a flatbow. I had a hard time tillering 2" limbs (could have made it 1-3/4"). And you have to worry about the fades, the narrow grip, which I have made too short. And for that reason, I want to try a D bow, which I heard are easier to make. I don't want to heat treat as I don't have a vise, a caul, and a heat gun (which are fairly cheap). I imagine it's easy to heat treat with the gear and experience.

So, here's my take: 65" ntn, 1 5/8 limbs, with a straight taper to 1/2 (or a bit less) nocks from midlimb. 45# @ 29". Would that make an efficient, durable bow without heat treating?  I'm making this bow for hunting. My stave has a slight crown. I see some "paradox" (if I'm using this word correctly) in this crown thing. I don't want to make the limbs wide because of the crown. But a wider limb makes more wood for energy storage. But then the top of the limb is more strained and the edges don't work much!

I'm sure I will stop asking such questions with experience.

On the picture, the outline is not my just proposed dimensions.

[DC]

I've never used birch but I wouldn't worry about that crown. I commonly use wood that is crowned a lot more than that.

[bassman]

No it will not make a good bow with your draw  at that length with out heavy ,heavy belly heat treat as said above. And for Birch the wider the better. I have 2 in the basement right now I have been working on.My wife can post pics later  if you like. They are 2 inches wide coming off the fades to 3/4 inch at the tips. The one I have nearly finished is 58 inches long for 26 inch draw  on a good day, and is close to 45 lbs. Started with 4 inches reflex on a form.It has now 1 inch reflex, and I keep heat treating it to hold it their. When I am totally finished with it will probably have a little string follow. If it does I will flip the tips a little, and heat treat again. The handle is bending a little in the last inch ,or two of draw. Start at 2 1/4 wide to 3/4 at the tips, and work from their. Use your wife's hair dryer, and use a make shift form, 2 by 4 flat with a 2 by 4  on end in the middle. Clamp the tips ,and heat treat the hell out of it. My 2 cents.

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bassman,
Of course I would like to see these bows. I really don't want to heat treat it. I will make it wider and longer: 2 inches wide limbs tapering midlimb to 1/2 tips. Perhaps during tillering I will narrow just a little bit.

Now I will turn this thread into a build-along  . All critique is welcome.
 

[Parnell]

May I ask why you are against heat treating?

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Parnell,
I'm not against heat treating. I thought I can just widen the limbs, make the bow a bit longer and here you go -- no bothering with heat treating. Bassman said I could do it with a hair dryer. I will do it. And post photos

[PEARL DRUMS]

A hair dryer will not work, not at all. Save your electricity for your lights.

[PEARL DRUMS]

Most heat guns vary between 750 - 1200 degrees F. Hair dryers get to 140 degrees F at most.

[bassman]

Hey pearl , I,m telling him to heat treat it some how . Over a fire, with a propane torch, or what ever. Never used a hair dryer so you could be right. Fact is that belly needs some heavy heat treat with Birch as well as some other sub par woods to get a decent bow.  We all prefer clean premium woods to make premium bows. I know you do. Doesn't always happen, so we use what we have. He should make some forms, and buy a heat gun any how if he plans on building more bows. He is not heading advice anyhow so I am done.

[bassman]

May be you have some better tips for him with that wood, and he will listen to you since you have a reputation for building a good bow. LOL

[PEARL DRUMS]

I don't have much of a reputation short of using my smart azz mouth when I see fit. I agree, it needs heat to be at its best. I have seen my good buddy temper an elm bow over red hot coals, worked like a dream.

[bassman]

I finished a 58" Birch self bow this morning.It is 44 lbs. at  almost 26 inch draw, and shot a 430 gr. arrow through the chrony at 149 fps average. Wonky as could be both strung ,and unstrung though it is tillered right, and shoots good.Over all weight is 14 ozs. I will get my wife to post pics here  when she comes home.