Bowmaker Question

[Todd Alexander]

My buddy and I were debating a bow making question but neither of us is a bowmaker. If a bow is made to be a specific weight and draw length, say 55# @ 27" is that bow markedly different from a similar bow that is built to pull 58# @ 28" or are they really the same bow?  Do bowyers do something that makes that desired draw length hit the "sweet spot" ?   Similarly, does that 27" bow start stacking at 28 or 29, or is that in our head? Finally, should a guy with say a 28" draw steer clear of a bow that draws 27" or not necessarily? OK you get the idea. Any free education would be appreciated.

[eflanders]

I will take stab at answwering this for you but I am definately not a master bowyer.

The answer to your question varys with the type of bow the bowyer is making and with what materials.  Based on my limited bowyering skills, self bows and all wood bows are definately tillered for the desired draw length and draw weight combination.  These bows can be very seriously damaged if drawn past their intended or designated draw length.  Fiberglass laminated bows are not as likely to be damaged if they are drawn a bit past their intended draw length.  However I do believe all of your really good glass bowyers (like Bill Dunn of Zipper) use very specific & proven formulas and will change materials and/or dimensions accordingly to maximize your experience in the chosen draw weight and draw length.

Remember to always, ALWAYS ask the bow owner if you can draw their bow before actually doing it or you could seriously damage their bow unintentially, especially if it is a selfbow or an all wooden bow!

[Sixby]

Some custom bowyers build length specific. This means that the bow is designed to perform at a specified draw length. They will also perform well with a couple of inches either way of that lenght but when built to precision will perform best at that given length. When buying a bow that says 28 inches on it and you pull 30 inches it is best to ask the bowyer or to check out that bow to make sure that you will not be overdrawing it. When you are drawing into the stack you are radicaly stressing the limbs and sooner or later that bow will go boom.

I consider a gain in draw force of a couple of lbs over the curve you have going stack. String angle tells you a lot too but not all. If the string is 90 degrees to the limb I advise to not pull it further. Still even before it is 90 some designs may   stress a short working limb.

Hope this helps,. God bless you, steve

[Orion]

If you look at almost all the commercial glass laminated bows made in the 40s -60s, most were marked at 28 inches.  For a given bow design/length, they didn't do different lay-ups, i.e., different lamination tapers, limb angles, etc., for a 27 or 29-inch, or other draw length.  Neither do most current day builders.

[Todd Alexander]

ttt
Any more comments?

[Dimondback]

The individual laminated tapers have an effect on this as well. I am no expert either but I was having an issue on the first couple of glass laminated bows that I made with the actual draw weight at 28" coming in around 5 pounds shy of my calculated/expected draw weight. By calculated, I mean the total thickness of all of the individual laminations stacked together for a 68" flat longbow on my form that was expected to be 35# at 28" should measure .344". I acutally came in at around 30# at this butt thickness. I found out that the reference numbers I was using were based on using .002/per running inch of taper on each limb. I had been building using .003/per running inch on all of my bows and thus had less wood/thicknees in the working part of the limb resulting in the loss of draw weight. I discovered this in the middle of my last build and simply cut 1 inch of the end of each limb which gained me around 6# of draw weight but a slightly shorter bow.

Long story short....there are A LOT of variables that can be manipulated to affect the draw weight of a bow and many of these also to change the draw "feel", stacking, tiller, as well as efficiency of launching an arrow.

Guess what....they all seem to shoot arrows just fine despite my efforts to the contrary....  :D