I really need some "mass principle" help

[willie]

So how do you know what your starting dimensions should be? If it were that simple it would seem someone could post the perfect dimensions and thickness and then you could just follow those dimensions every time for the perfect bow. But that doesn't work, right?

In TBB Vol 1 I think they say a 66” bow that’s 2” wide to mid limb and tapering to the tips will pull a draw weight about the same as the woods‘a specific gravity.

A specific gravity test is easy, and other rules of thumb are mentioned in TBB. As I recall, different starting widths for different densities

[Don W]

That's because most people fit tiller to front view shape so you only need to take wood off the belly to work on tiller. You could take wood off the sides if you thought you had too much mass but most folks already have starting dimensions in mind when they shape the bow

So how do you know what your starting dimensions should be? If it were that simple it would seem someone could post the perfect dimensions and thickness and then you could just follow those dimensions every time for the perfect bow. But that doesn't work, right?

I base my dimensions on experience based off of all of the bows I’ve ever made and trying to find dimension of bows others have made. I know based off of previous designs that if a wood is a certain density then I will need to make it a certain width based on the design/draw weight I want to make. The thickness is more determined by the working limb length and draw length as that doesn’t seem to vary much across hardwood species. I’m not so nit picky that I’m going for absolute perfection but I’ve been able to achieve low set (<1”) pretty consistently. A couple times where bows have not taken any set I started to remove wood from the sides later in the tillering process and those were with exceptional pieces of wood.  Judging wood based on density can allow you to use new woods with higher success as the other properties of compression/tension strength are usually not a huge factor if making conservative flat bow designs with flat bellies.

Does this maintain the average or better arrow speeds?

[RyanY]

Great question. I’m not much of a shot, especially in front of a chronograph. But from the few I’ve tested they seem to be above the averages described in the bowyers bible. Now-a-days people are putting out awesome bows so I bet they’re pretty average overall.

[bradsmith2010]

make it as complicated as you need,, but 66 inches 1 1/2 wide,, will make a nice shooting bow,,fast flight string, and it will out shoot average bows from 20 years ago,, just try it and see what you think,, stiff handle or bendy,,