Draw length theory ???

[Grizzzly]

I was wondering about what your theory is on building bows to a specific draw length. I've only built a couple of selfbows & looking to have a laminated recurve built soon & maybe make one myself. I know there are alot of 28" draw length bows for sale out there but if you shoot at 26" or 27" you would not be getting the full potential from the 28" bow. Correct ?? I would think that if someone was to build 2 identical bows only difference being draw length,say a 26" and 28" the bows limbs should be opening at different times to make the limbs work to their full potential at the specific draw length. If I draw a 26" bow my limbs should reach total open sooner than the 28" bow, correct ? Not just stop short in the draw cycle. I hope I'm making sense here. I have bought bows in the past at a 28" draw at a peak weight of a little more than I like to shoot & people have said " well at your draw length you'll be shooting the lighter weight" Obviously but I wouldn't think that is the way to go. Isn't a limb designed to work at a specific draw length ? Sometimes hard to find used bows made to my shorter draw 25-26". I just would like some more opinions on this from some of the bowyers out there. I'm going to have someone make me either a 1 piece or 3 piece t/d recurve soon, a short 52" 45#ish @ 26" draw. So if anyone out there is interested in a bow build job, let's talk. Thanks for your input, John

[jess stuart]

I suspect that few bows are built for a specfic draw lenght i.e. 26" or 27".  The cost of changing designs to meet different draw lentghs would be prohibitive.  Bowyers have to make money, and time is well money.  In some ways you are lucky if you have a shorter draw length as the short bows as well as the longer bows will work well for you.  The same probably will not true for the guy with a 31" draw.

[DVSHUNTER]

I would like to think that your theory is true.  I wonder what kind of difference it makes when the draw force curve is shortened.

[monterey]

Charting the bow should tell you something.  

Most bows would probably show you more energy being stored per inch of draw at the lesser length, but the bow also gives up those last two or ???? inches of draw length which will reduce overall stored energy.

I could be way off, but it seems that if you built a design meant to be drawn to 28" with a fd curve that would hit your desired draw weight at 26" then you would be shooting a more efficient bow.  Especially if the design begins to stack at all between 26 and 28 inches.

[DVSHUNTER]

that is what I was thinking as well, I just havenlt figured out how to build em like that yet.

[Jason Scott]

I agree monterey. If that curve starts to indicate stacking at all that means the bow is starting to become less effeicient. Could it be that most bow cuves indicate a higher dynamic efficiency factor at 26" than 28"? That would mean it doesn't matter how the timing of the limb loading is or what intensions the bowyer meant, or what they promiss they can do for a special short draw customer... if the curve says it is most efficient then that is what you should be wanting. You would have to speed test a given bow at 28" draw w/10gpp and then at 26" w/10gpp (and figure the KE for each). Then divide those two KEs by the draw weight at the two lengths. The higher % is the most effient draw length for that bow. I would be interested in the relults if anyone can do this test for one of there bows. I bet most bows start to tail off after 26" or 27" by looking at the shape of most curves. And that's why longer draws need longer working limbs.

[DVSHUNTER]

very well put.  Hopefully someone out there can give us a solid answer.  My interest is in selfbows at this time.  Would there be differences? It seems there would be.

[Jason Scott]

yeah, I think with selfbows, from my understanding, is that the bow is tillered for the owners draw length. The compression on the belly is set for that specific draw length. Any other draw length would be less efficient or damage the bow so it would be hard to perform a variable test.

[Jason Scott]

I guess you could experiment with different gpp arrows at a given dl to find the most efficient setup for a selfbow. But most of the time you would prefer to get good ke or momentum, arrow flight and ingrain the trajectory in your subconscious mind and call it quits.

[Pat B]

My Treadway bow(older style circa 1990) was built for my draw length and that is 56#@26". I'm pretty sure it would draw to 28" but I have never tried it or measured the weight at 28". My guess it would increase 3# per inch but that is only a guess.

[Jason Scott]

If you drew it to 28" would it overcompress the belly fibers therefor leaving it a lesser performing bow at 26" than it was before? That is after it has been shot a few times at 28".