Does an R/D design shorten available draw?

[Zradix]

Hey guys.
With all wood bows in particular...
When you have more reflex in the limbs will the bow have less available draw length before breaking?

My thought was..Wood can only bend so far. If it has to bend 9" to get to brace the amount the bow can be drawn is shortened.

I understand the whole 90˚+ limb tip/string angle increases stack.

Really just trying to figure out if it's easier on the wood to make a 64" bow that will be drawn to a true 29.5" draw..fairly straight with a little flip to the tips to keep the string angle good.
...or a typical R/D design that more or less keeps the string angle good by reflexing the limb as a whole.

Thanks for your thoughts guys.

John

[Roy from Pa]

No and for a 29.5" draw I'd make the bow 66" to 68" long. Fujimo has a 29 inch draw. I made his bow 66" and pulled it to 30" on the tree.

[Bowjunkie]

John, with all else equal, I'd say yes, the bow will have less draw length available before overstressing because, like you said, if it's got 4" of reflex, it will have to flex 4" farther from its unstrung profile to reach the same full draw length.

That said, it's easy enough to change a few other design parameters to offset it.... deflex in the handle area, thinner, wider, longer limbs, shorter stiff handle area to allow for more working limb, etc.

I'm working on a pair of osage billets now that have a good bit of natural reflex, as well as some serious character and limited length, so I'm going to have to find a way to keep the stress to a moderate level. I'll likely deflex them a bit at the Z splice and make them a hair wider than I would otherwise.

[EwokArcher]

I also say yes. By preloading the limbs with pure reflex past the handle I feel like you will be increasing the strain on the limbs, however this can be compensated for with increased width of the limbs to distribute the stress.
Also I agree with Roy and would go for the longer bow for that draw length.

[Zradix]

Thanks for the replies.

I  agree...A 66-68" would be easier.
...this post of Roy's showing a 62" pulled to 29" at least showed it could be done. Dang did he have to do a good job tillering to make that bow bend like that...
 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=013884;p=1#000000

I was thinking if I added a little length to the bow, made it a touch wider, and jigged it to the profile easiest on the wood...I might have at least a slim chance of getting things to work out.

[LittleBen]

I see what you are getting at with your question.

I approach it a little differently. I start by deciding what type of bow I want. My goal is not to make a bow that will survive, but to make a bow that will perform in its intended role.

Let's say I need to make a bow for someone with a 29.5" draw, and the guy wants to hunt from a blind, so the bow can't exceed 62", and needs to be minimum 45#, and assume the guy wants a stiff handle bow. I know that a straight limb bow of that length will stack badly, so I know I need to have deflex in order to improve string angle, and I will need some reflex to keep performance up to a reasonable level.

D/R bows have that benefit, they let you make a shorter bow for a given draw length without sacrificing string angle.

So in my example, I now know I will make a 62" D/R bow, it may be a recurve or may be a longbow depending on if I also flip the tips a lot. Then I will decide on materials and dimensions to achieve that.

In this case I might use ipe or osage belly, hickory or bamboo backing, and whatever core material I've got available. The critical decision really is 'how wide do I need to make it'.

No one can tell you exactly, but I would probably go 1.5" wide. Then it's just down to tillering.

But to answer your question directly, if you had two, well let's make it three bows of the same length and width and materials, one with straight limbs and flipped tips, one with even reflex along the limbs, and one with deflex and reflex, all three have the tips in the same position relative to the throat of the grip. In this case, there should be almost no difference in strain on the wood (aside from the benefits of perry reflexing).

The D/R bow should perform the best at a given draw weight.

Both the DR and the reflex bow will benefit to some degree from the perry reflexing, and the bow with flipped tips I would expect to take the most set.

You're question is which is easier .... They are all the same difficulty. If you tiller well, all will work fine, if you tiller poorly, all will break.

Sorry for the essay.

[Zradix]

Thank you Ben.

I understand what you said.

...and I always appreciate an essay answer!