How to tiller a Pyramid bow?

[Chuck Jones]

To start out I wanted to cut out two bows.  A Eastern Indian design and a Pyramid bow.  Soon the two bows became 4 bows cut out.  On the Eastern Indian design I can not remember now why I started the second bow I believe it was something about the taper.  Oh well, give me a break 67 now and they say the memory is one of the things that dont work so good at older years.  Now the Pyramid is another story because I do know why I started the second one.  Not really knowing what I was doing and I searches didnt bring up much information I cut the belly now to 3/8" like I have done on my other bows.  Then I read that the Pyramid is say 3/4" thick from grip to tips so that is what I am roughing out now.  Now back to the original question I dont know if I tiller this one the way I do my other bows by removing wood off the belly or (read somewhere you take it off the sides) take wood off the edges of the limb and how much?  Are we talking about from 1/4" from the back to the center of the belly or is that to radical?  Thanks...I really appreciate all the help that I have had from this forum so far from my begining back in November....chuck

Oh yeah the bow is 68" ttt and will be 3/4" thick when I get that part done.  The fades are 3" wide and it is Cherry wood.  Not sure what variety it is a light colored wood.  I plan to back it with either Jute laid out like sinew would be or Rawhide.

[Badger]

Chuck, the idea behind a pyramid bow is that it is equal thickness the entire limb and the pyramis shape makes it bend evenly. You get it to final draw weight by just thinning th elimb until it hits draw weight at your specified draw lenght. The center potion of the bow (8" handle and fade area) should be about 3/4 thick at least in this area.  steve

[Chuck Jones]

Thanks Steve---Learning a little bit more all the time.  I am working on getting it to 3/4" not to far away now.  I did try to bend it at floor tiller like I always do after I cut the profile out.  It just barely bends a little now.  I will probably have a lot of thinning to do to get it to start bending...thanks..chuck

[huntermike]

Just to give you an idea of how thick it may be: I just finished an oak pyramid bow for my wife.  58in n2n and 36lbs at 27in.  The limb width tapers from 2 3/8in at the fades to 3/16in at the tips.  The limb thickness is 5/16in out to 4 from the tips, which are then 7/16in thick.
Mike

[richpierce]

Just remember that wood removed from the belly reduced pull weight dramatically- making it half as thin results in a bow 8 times weaker.  Reducing thickness by 10% reduces pull weight by 25%.  So go very slowly.

[Chuck Jones]

Thanks for the respose.  I am very concerned about the grain in the cherry that I have.  I just finished backing a cherry pyramid bow made out of the same cherry board.  I backed it with some backset in it using jute twine and it really became stiff.  More so than I would have expected.  If the smaller bow works out I may try the same process on the larger bow.  Bow 1 that I call has a smaller width at the fades than the bow I call the larger.

The way I understand the tiller process is the remove wood from the length of the limb until you get to the designed draw weight.  I am very close to start this process on bow 1....thanks for the input...chuck

[tom sawyer]

In practice, a pyramid takes some tillering just like a parallel-taper bow.  The straight width taper does help, but it does take some additional thickness tapering to get the right bend.

[Chuck Jones]

Thanks Tom for that advice.  I will go down that road.