the mass principle in one sentence

[Justin Snyder]

   Half I pointed out they were making bows just fine for the last 10,000 years with no need for the bowyers bibles and he was right on when he said that, instead they were using 10,000 years of experience that was lost a while back. The quality of bows has come up immensely in the last 10 years I think because of internet sharing of experience. a new guy can come in today and be making excellent bows in a very short amount of time. If he chooses he can still strive to make them better. If not he can just enjoy the journey. I enjoy both, I have the greatest appreciation and respect for the ancient bowyers, I can't say it enough times, they really knew their stuff. Just for the record, in some cultures bows were not measured by draw weight they were measured by mass weight, so it is nothing new. Steve

I appreciate your hard work Steve. I really enjoy pushing, and have broken less bows while improving performance since using your bow mass calculator. For me, pushing the limits is part of "just enjoying the journey."

[Badger]

  Justin, I appreciate that. I thin all of us enjoy this in different ways, none of them are bad. Steve

[Gordon]

Steve,

I'm building a set of bows for a husband and wife. The 48# bow came in right about where your table in TBB4 says it should. The 30# bow, however, came in about 2 oz light. It does not seem underbuilt and didn't take any noticable set. Does your formula require some adjustment in the lighter range?

[Badger]

  Gordon, not really should remain pretty close down to 35#. It is a bit conservative. Just for the heck of it could you post the bow and let me figure the suggested weight without you telling me what it was. Give me the draw weight, front view ( description or picture) handle size. Draw length and tiller shape. There are several woods I tend to come in light with all the time, yew, cherry, cedar, are a few of them.

[Gordon]

Here it is Steve. Draw weight is 30# at 26", 4" handle with 2.5" fades, length is 63.5" ntn. The tiller is more or less circular. The wood is hazelnut which seems to have a similar density to yew.
 

[Badger]

  Gordon if the bow is a straight bow with no deflex or reflex and the finished profile is within 1" of the strting profile I have 13.9 oz,  I would usually tweak that down to about 13 oz. Steve

[Gordon]

Steve, the bows holds about 1" of reflex at rest and is straight right after shooting. And the reflex was induced. Does that change your weight calculation?

[Badger]

Thats pretty good, perfect would be the same before and after shooting but seldom do any of us see perfect. That would stay about the same maybe 13.5 after tweaking. Looks like you refined the tips and such as I would have. 14.3 would be conservative.

[Badger]

one more question, how much reflex did it have when glued up? Steve

[Gordon]

Steve, it's a self-bow. The stave started with about 1" of deflex. I heated in 3" of reflex before tillering and lost most of it.

[Badger]

  I figred it as a backed bow, I would have built it at about 16.5  with all that reflex. Steve

[Gordon]

The bow weights 11.7 oz.  Maybe I underbuilt it?

[Gordon]

One other thing to note. It was made from a 2" sapling so has a relatively high crown. I don't know if that makes any difference?

[Justin Snyder]

One thing that I have found is that when you are doing bows for people with small hands you often loose a little bit more weight in the handle. Womens bows with rigid handles can easily weigh 1-2 oz less just in handle weight.

[Badger]

Thats not bad Gordon, heat treating takes off some weight also. I would say you slightly underbuit it. One thing I have found if a bow is comming in lighter than I expect is sometimes the moisture is on the low side. A 6% moisture bow will come in lighter and not take set than an 8% moisture bow. I have a couple of light bows I checked and they are a bit lighter also. You may have a small handle which you have to judge yourself that might be worth an ounce or so. Handles are one of the things the bowyer has to take into account, it is based on a 4" by 1 1/2 handle roughly. Once I start tweaking I try to get the mass as low as I can without changing the tiler.