hickory backed cherry- why so fast!!?

[sulphur]

had an oppurtunity to see a bow i made a few years ago that was hickory backed cherry.  i was surprised by how fast it was.  the tiller was not particularly good in fact i would say it was whip ended.  its 1.5 " wide till the last 15" of the limb then tapering to .5 nocks.  I really am trying to understand why this bow was so fast, it was every bit as fast as a hickory backed osage bow that was 8# heavier and much better built (one of my more recent).   any ideas guys?  i tell you what though, its got me going to the lumber yard tomorrow to pick up some more cherry!

[KShip85]

I'm no expert but I have heard cherry has one of the lowest hystersis values of many woods.  That could be a reason for good performance.

[DanaM]

If you follow badgers mass theory its not so much the wood as it is the design that makes the bow efficient(fast).

[coyote pup]

I'm thinking along the same lines as Dana. What kind of cross-section does the cherry have?

[adb]

If you can get cherry to hold together or not fret, it makes one of the fastest bows there is.

[Hillbilly]

Low limb mass.

[Badger]

      As said above, cherry has almost no hystreisis. It does tend to chrysal though. My favorite hunting bow was a hickory backed cherry for many years but the chrsals final go to the point where I was worried about it. Steve

[Justin Snyder]

Whip tiller also means that you have low mass on the outer limbs to move. It can make for a fast bow, but it is a gamble between speed and durability.

[sulphur]

thanks for the hints fellas.  I did notice the top limb had a ever so slight chrysal.  i am gonna give it another go with some good ash i have been saving for backings

[dmann]

the real reason for the unbelievable speed is the fact that cherry has amazing compressional strength. While hickory has possibly the most tensile strength of any wood. Putting cherry as the belly and hickory as the back is a recipe for speed

[elk country rp]

cherry is evil, that's why it's so fast. it wants you to love it so it can crush you with a loud BANG!- clatter, clatter   

[sulphur]

thats funny   i used cherry a lot when i first go started because it was cheap and i found a few really straight boards.  i didn't realize it was so touchy. probably why i had so many failures.  i bought some more today at woodcraft.  I am looking forward to the challenge.  right now i am thinking maple might be a better match for a backing.  Its been hard to find hickory lately.  i may have to take a trip to the saw mill.

[Hrothgar]

Several years back I bought a hickory-backed "u-finish" bow from Dan Quillian. Still have that bow. Its taken quite a bit of set, but the weight and smoothness are pretty amazing.

[elk country rp]

i'd recommend making the maple backing a little thicker than usual, unless you find some maple with absolutely flawless grain. i had a MBC explode after well over 600 arrows due to a slight (very slight) ripple in the grain of the maple right at the handle (thought it would be safe there  ). it kinda put me off maple for awhile.   

[Del the cat]

I've always felt whip ending should give more speed, despite plenty of opinion to the contrary.
If you take a stiff limb tip and say it takes say 10milliseconds to recover from full draw, if you then remove material from the the last say 5", and draw it to the point where that point 5" down the limb is at it's previous deflection, you will actually be drawing further (due to the additional tip flex).
The point 5" in should still take 10 milliseconds to recover (as you havn't changed anything on the handle side of that point), but while it has been recovering the last 5" has recovered the extra draw (assuming a 5" limb with very small deflection will recover at least as quick as the remaining 20+" of limb).
Thus your longer draw has recovered in the same time and is therefore faster...now factor in that you have removed mass, even quicker still.
Off course this my be an over simplification and total bull, because in reality you would have lowered the draw weight of your existing bow at the same draw...but if you do it before the bow is reduced to final weight to get the effect at your required draw length the logic should hold good.
Presumably the reason a Holmgaard design works is that the stiff levers are light as well as stiff due to their narrow/deep section.
Common sense would tend to say that all parts of the limb should work together for maximum efficiency (ignoring the string angle/recurve arguments)
Del
(blimey, I need to lie down now)