WHY are short bows slower?

[Kegan]

Trying to sort this out while my short irons are still in the fire:

Say there are two well designed bows, one 66" the other 56". The 66" is straight and the 56" is reflexed enough to have a similiar F-D curve. However, it seems that even with less mass and no stack the short bows don't shoot faster. I can only guess that their less mass is cancelled out by the less leverage, correct? Is that the trade off or am I missing something else?

Thanks in advance, hopefully the next set of sticks I finish will be able to shed some light as well

[fishfinder401]

mabey you removed some of the weight in the wrong place, cancelling out the weight reduction, some of my fastest bows are short
hope this helps a little
noel

[Del the cat]

I dissagree with your assertion.
However for any particular style of bow and wood there must be an optimum length, longer or shorter than that would reduce the performance.
If you take a set of carbon limbs from a modern target bow (spits on floor) and mount them in risers of widely differing lengths you will change the performance...but we then get into the realms of geometry beyond my furry cat brain.
Del

[medicinewheel]

...
If you take a set of carbon limbs from a modern target bow (spits on floor) ...

Funny

[Shaun]

It is my unscientific observation that shorter bows are faster. 

or am I missing something else?  ...distance traveled by the limb mass (where the mass is on the limb), length of working limb, modules of elasticity of the limb material, etc. 

also... faster can be relative to arrow mass/draw weight ratio, ie. flight bows vs hunting bows.

[NTD]

"One of the cruel realities of bow design is that shorter straight bows can't be as fast per pound as longer straight bows even at equal draw length.  Bewteen 35" and 60" possible performance rises roughly 1 fps per inch of bow length.  Cast rises slowly from there to around 68" then only minor improvement from there to 80" and only then if given a more elliptical tiller."

-Tim Baker
Traditional Bowyer's Bible IV

[NTD]

So that supports Kegans assertion, Del, Fish, and Shaun, Now let's get back to WHY.

[sharpend60]

I always thought of it like a power stroke.
Thus making longer draws and longer bows faster.

The Bowyers Bible 4 seems to support that.

On the other hand, shorter bows do seem faster and are quite cool.
I think it would take a large sample to eek out any results of an fps test such as done in the Bowyers Bible.
Craftsmanship and design are much greater factors than limb length alone. The shooter is also a huge part of a bows ultimate performance.

[Del the cat]

"One of the cruel realities of bow design is that shorter straight bows can't be as fast per pound as longer straight bows even at equal draw length.  Bewteen 35" and 60" possible performance rises roughly 1 fps per inch of bow length.  Cast rises slowly from there to around 68" then only minor improvement from there to 80" and only then if given a more elliptical tiller."

-Tim Baker
Traditional Bowyer's Bible IV

Yeah but you are changing the rules here and suddenly taking 60" as your reference.... like pulling a rabbit from a hat.
"lies damn lies and statistics" as the famous qoute goes.
From my ELB based view as you reduce length from say 74" you do get faster... indeed having built a 89" longbow I can assure you that longer gets slower.
It all depends on where you take your start point in terms of length.
The real problem is a badly worded post in the first place.
'Shorter' is meaningless without a reference.
Del
(Grumpy cat )

[George Tsoukalas]

A 52" bow drawn 26" will stack and take a lot of set.  Jawge

[NTD]

Del,
35-60"  You cherry picked the 60".  And these aren't my words they are Tim Baker's, maybe you missed the quotations   He also goes on to say that cast only improves up to 80" IF if the tiller is adjusted.  So your example of an 89" longbow being a dog is probably quite accurate but hardly a repudiation of the quote. 

You also said that the original post is meaningless without a reference...Maybe cats have poor vision...he said 56" and 66"

A 52" bow drawn 26" will stack and take a lot of set.  Jawge

A bow made with stiff outer limbs and inner limbs wide enough to compensate for the extra work being done would not take excessive set or have stacking issues, especially at 26".  A molle design for instance...

[Del the cat]

Post deleted...too grumpy
Del

[Cacatch]

Most of us shoot short arrows with short bows so the arrow weighs less than an arrow from a longer bow, thus compensating for some of the shorter power stroke. Also, shorter limbs take less time to snap back to brace position than longer ones do, causing the illusion that the arrow is going faster because it comes off the bow a fraction of a second earlier. Nonetheless, the power stroke is shorter, so they won't usually shoot as far or as fast as a longer bow, although they might appear to. That's my take on it.

CP

[Buckeye Guy]

All this talk of cats and dogs and it aint even raining !!!

[JackCrafty]

Short relative to what?  For a given draw length, there is an optimum bow length (or range of lengths) for maximizing the speed of the arrow.