Draw length and fps

[Steiger3208]

On mild r/d D shaped bows is there a basic fps increase per inch of draw length? Thanks, Wes

[Knawbone]

Yes. but it's minor unless way under loading the limbs of the bow. A couple of in. under or over draw with a bow measured at 28" should not drastically affect given arrow speed. Just how much would vary with the draw curve of that paticular bow.

[Orion]

On a mid weight bow, you're adding about 2#-3# of draw weight for each inch of draw length bneyond 28 inches.  That translates into about 5 fps per inch of increased draw length. Not enough to worry about.

[swampthing]

Depends on arrow weight. 8gpp arrows might go 12fps per inch. 10gpp may go 6fps per inch...

[ishoot4thrills]

Originally posted by Orion:
On a mid weight bow, you're adding about 2#-3# of draw weight for each inch of draw length bneyond 28 inches.  That translates into about 5 fps per inch of increased draw length. Not enough to worry about.

Plus you gotta factor in the increase in the power stroke with the added draw LENGTH, not just the increase in draw WEIGHT. That is, if you're using the same bow.

[FarmerMarley]

I just read in "Shooting the Stickbow" that the increase in the length of the power stroke has a bigger impact then just the increase in 2.5 to 3 lbs draw weight per inch. It's definitely a factor.

[Knawbone]

Farmer, That's why I included the draw curve in my post. The power stroke is part of that curve.The draw curve can/is shown as a graph.

[mmilinovich]

Tony Camera, in "Shooting the Stickbow, says that an extra inch of draw length (beyond 28") has  WAY MORE impact than might be expected from the extra draw-weight of 2.5 pounds.

A friend shoots a vintage 38#Wing and he, in my presence, has chronoed it on two separate occasions. Both times he topped 200fps, albeit with light arrows.

Still, to achieve those numbers, his 30" draw has to be credited with 25-30 of those fps.

The longer power stroke is a huge advantage!

Mark

[trubltrubl]

ok guys what is the difference if you shoot two different bows of... in theory exact same design and one is 55 lb at 28 and you shoot it at 28" and the other is 55 lb at 26 and you shoot it 26" ...so you have the same poundage but two inches more "push on the arrow"...there should be a difference but how much? just curious....

[Shawn Leonard]

What ishootforthrills said, I know on static tipped bows ecsp. really radical ones like my Borders it can make quite a difference as you want to get the tips to really open up, also braceheight comes into play as well. Shawn

I don't think that that there is a basic increase, depends on the bow. If your draw is under 28", like mine is, you can get some of the arrow speed back by getting a shorter bow or a bow that is adjusted to open up at the shorter draw. With some bows this works and others not so much. I have noticed that with one r/d bow that I have that is two inches longer than my others, that is tillered to be optimised for the shorter draw, the tips come around more than another bow by the same maker that is the same length but tillered to a standard draw. I have not chronoed that bow but it seems plenty zippy and likes arrows with one spine stiffer than the Stu Miller charts suggest just like my shorter bows from the smae maker.