Very short wooden prod.

So I'm attempting to get the most out of some scrap wood I have leftover from other projects and decided to build a small lockbow.
The piece I have for the prod is ash wood, very straight grained, but only 26 inches long. I realize that at this length I'm not going to be breaking any power records, but I want to get the most out of it that I can.
My thought is to back the prod with rawhide, and have a pretty short draw and a low brace height. Specifically I'm going to attempt 70~80lbs at 10 inches with a 2 inch brace.
I would appreciate your thoughts on this matter

Tehartificer,

GET AFTER IT !

Chaz

Make certain you have no or very little grain runoff, otherwise the prod may explode. Rawhide is a good backing, but if you have severe runoff, then it will only serve to protect you when the bow gives. Of course, a shorter draw of a crossbow many help. Just thoughts from making traditional wooden hand bows. And be certain the wood is seasoned enough that it doesn't take severe set. You loose power in that case. Ash is a decent bow wood, though, so good luck!

Dane

As a fellow selfbow maker I would say that if the bow does take set it will be slower but should be safer to draw. I have a red cedar unbacked bow with plenty of knots and cracks (lengthwise) that I made with just a hatchet. It draws 65 to 70 pounds and been shot hundreds of times. I think it has about 5 or more inches of set which is why it is safe to draw. I think the old steel prods had a lot deflex also to the point they had to be bent only slightly to string them.



Todd

I made some selfbows from Ash, and read a lot about it in our german forums.

It is depending on the quality of the wood but ash is known to get relatively big amount of set.
As for the prod, you should have a intact annual ring on the back of the bow and grains should not run out of the tiller if possible.

If you make an even tiller your measurements (especially your draw lenght) will be possible for a working prod.
In selfbow cases the maximum draw lenght of a wooden bow is calculated bow lenght minus (non bending) grip area divided by two minus tip area (material not to be calculated at end behind string).

As for the design you should try a pyramidal bow with not a too high profile.

You should give it a try, but possible draw weight will depend on the wood (the better the wood, the thicker will be possible without chrysals, extraordinary set or breaking)

Rizzar

By 10" draw 2" brace height you mean 8" stroke?
Sounds feasible for 26" long good quality stave.
But a stave that can handle that could also take 140# with 6" stroke. If left 30% thicker.

How wide is the stave?
For a narrow bow mere heath style tiller with wide tips and good amount of thickness taper would be safer than pyramid.

You do know that usually 5 grams of bending wood can store 1 joule of energy - there is an easy way calculate an estimated safety margin.

The design of this bow is a pyramid as Rizzar suggested. It starts at 1 1/2 inches wide and tapers down to a 1/2 inch at the tips.
The wood itself is the leftover piece of an ash board 2.75 wide, and 3/4 thick. it has a slight warp of about 1/8th of an inch that I had planned to use to my advantage as a natural reflex, but now I am not so sure, it may be better to use this as deflex instead.
In any case I will be backing with goat rawhide to make up for my lack of having a growth ring along the back.
So now I ask you all, do you think I should make the prod wider (I have not cut it out of the board yet, so the design can still be changed), and should I use the natural bend as reflex or deflex considering the application?

Uhhh, to be honest, I am not sure if rawhide will catch up the lack of an intact growth ring (suggestion or the complete absence of rings).
It can help with a damaged one for sure, but everything has its limits.
As for Ash wood is relatively easy and cheap to get here I question myself why you are using leftovers instead of good quality bow material.

Besides, bow wood can be overdried too and tends to explode (especially yew) or break spontaneously. This comes to a point when using industrial dried wood like something not meant to be a bow when chamberdried.

Concerning the deflex/reflex thing: The only possible direction is in my opinion the growth direction of the wood. Outside ist outside!
And why is there a natural deflex on a board? For my understanding that seems to be a warp from either unilateral drying or moisture since boards are normally cut straight.

Only wood I would consider using regardless of consistence and then not pushed to the limits is Hickory since it is tolerant due to special adhesive powers through the grains.

The ash would probably be deflexed after tiller regardless of reflexed before or not.

Sorry for my pessimistic estimation, but I learnt it is much less demotivating to build with proper materials instead of being thrown back by suboptimal preparation and conditions.
Unless you have good experience in selfbow building i would´t dare judging the wood positive.
If you use proper wood it is possible to build a good bow though it is harder the shorter.

Greetings Rizzar

The dimensions should be possible but I don't know about that wood choice. I would go with hickory or osage orange or best...hickory backed Osage. If you aren't against it, a strip of fiberglass as backing will probably make the the best backing if the wood doesn't chrysal under its tensile strength.

Forgive me for sliding in here late but I came to see if anyone made prods with wood. I too have made several selfbows backed and unbacked. I have a nice piece of oak that is backed with bamboo. Sounds like you are starting with 26 " chunk of wood, with limb widths of 1.5" going down to .5". What would you suggest the limb or prod thickness be if trying to get a 100" draw weight?