Draw length versus speed

[Shooterboy]

I understand that a draw length of 30 inches increases the bow poundage as compared to pulling 28 inches and thus increases arrow speed; however how much added arrow speed is a direct result of the arrow staying on the string 2 additional inches?  

I have talked to a couple different bow makers who said the added draw length past 28 inches substantially increased the speed.  For example, one bow maker stated that he was able to generate arrow speeds over 220 fps with a 55# bow.  I called to inquire and he said that the way he got this incredibly high speed was his bow was around a 49# bow at 28 draw, but he was drawing 30 inches and this additional 2 inch draw length created incredible added speed.  

My own tests only show about a 4 to 5 fps increase for each 1 inch draw length over 28 inches.

Thanks for your comments.

[HATCHCHASER]

Your tests are the normal.  4 to 5 fps per inch of draw with respected weight.  A bow drawn 55@28" will be 8 to 10 fps slower than the same bow drawn 55@30".  Release plays a role from person to person.  If someone is getting 220 fps @ 30" draw shooting 9 grains per pound then I want one.  Fps is relative to arrow weight.  We have to compare apples to apples.

[Shooterboy]

Thanks Hatchchaser.  That's why I called to find out how a 55# bow shoots 220 fps.  It makes sense that pulling 29 inches or 30 inches would provide some additional speed other than just the increased pull weight; possibly from the increased energy generated from the bow being pulled close to it's maximum draw length.

[ibehiking]

I saw a little more than 4-5 on my Howatt Hunter. I got about 7-8 fps for an extra inch of draw (28' to 29"). I think it was due to a combination of the extra weight at the length, the extra inch on the string and my release seemed to improve (I think I was short drawing a bit).

[wingnut]

You need to remember that the area under the force draw curve is the stored energy.  So that being said, when adding two additional inches to the high end of the curve you are adding a bunch of stored energy and at about 80-85% effeciency you return that stored energy onto the arrow.

It's not uncommon to pick up 8+ fps with each additional inch at 9 gpp.

People with longdraws have it easy.  Oh wait a minute, I have a long draw.  LOL

Mike

[George D. Stout]

The longer draw doesn't make anything easier, but it does add power stroke.  If you can control all aspects of that form you will have a power advantage.  How that equates to what you do in the field is more a reflection on that archer and how efficiently he or she is able to utilize that gain.  There are trade-offs for each so-called advantage 8^).

[widow sax]

Back in my wheely days I knew all the numbers fps numbers on plus or minus grs of arrow, lbs of pull and lenth of pull. What is the average speed differance on each lbs added or subtracted I know bow design has alot to do with it but what is the general expectation in speed differance. I would probably just add arrow weight and keep the same speed but was just wondering. Thanks  Widow

[Flying Dutchman]

For the pounds there is a rule of thumb: 5% more for every inch more in drawlenght....

So if you have a bow of 50#@28" and you draw 30", you will end up with 55lbs.

Okay, now your arrows.... speed is defined by the type of bow and the amount of grains per pound.

Suppose you were shooting 500 grains arrows.
With a 28" draw (50#)  you will end up with 10GGP.
With a 30"draw (55#) you will end up with apr. 9GPP.

This is a gain of 1 GGP, which will result in a speed gain of 4 to 7 FPS (another rule of thumb), depending of the type of bow and actual drawweight.

Mostly, bows who are way above the 200 fps, are shot with a very light arrow (8GGP or even less) Shooting this way will shorten the lifetime of your bow dramatically!

With my modern modestly R/D longbow I shoot aprr. 190 fps with 9 GPP.

[Rob DiStefano]

yeah, and bare shafts will fly faster than fletched shafts.  none this matters to any great degree.  sounds like 'cabin fever' talk, to me.  :D

[Flying Dutchman]

To who or what are you reacting Rob?

[Rob DiStefano]

Originally posted by Flying Dutchman:
To who or what are you reacting Rob?

me!   :D      

if ya haven't already noticed, i can really get caught up in all this gear tweaking talk! LOL!     :eek:

[Flying Dutchman]

Ah, ok. I love this stuff! And I improved my shooting with it...

[George D. Stout]

It's all good Flying Dutchman, just be careful of the shiney things....they can drag you in with their luster.        Some of that information is real, and applicable to what we do,  but some should be cast out with the chaff.

The one law you must remember...Newton's Law of Motion:
"For every action, there is an equal and opposite reaction."

[Flying Dutchman]

That's all true George. There are a lot of people who throw around formulas without any experience in the field.
The figures I gave I learned to be truth from practice.

[Don Stokes]

Dan Quillian was fond of saying that adding an inch of draw length was like adding 10# of draw weight. He was prone to exaggeration...       There's no doubt that you get a significant performance increase with a longer draw, as long as form doesn't suffer as a result and mess up your accuracy.

Not all bows gain the same number of pounds per inch. It can vary from a couple of pounds to several, depending on the force/draw curve that results from the bow's design. "Stacking" means that the draw weight increases per inch as the draw gets longer, i.e. 2# from 28 to 29, 4# from 29 to 30, etc.

[LBR]

"Dan Quillian was fond of saying that adding an inch of draw length was like adding 10# of draw weight."

Don, he was talking about a Canebreak drawn to 30".      

You do pick up some extra energy with a longer draw.  As I understand it, that's one of the primary problems with an x-bow, and why they have such high draw weights--short power strokes make them inefficient.

I agree with being careful what you read.  There's one (so-called) expert who says in his book that you basically gain 10# worth of performance for every inch you draw past 28".  For example, a bow pulling 40@32 will shoot as fast/hard as the exact same bow pulling 80@28.  Of course that's a big load of bull splatter, but it's "in the book" so some people believe it must be true.

Chad

[Don Stokes]

Yep, those Canebreaks would shoot way over 200 fps with the AMO standard of a 540 grain arrow and 60# draw weight at 30" draw, as fast as compounds at the time.

[skarcher]

In my opinion (which may not be worth much to some) speed increase with increased draw length is somewhat meaningless. Now before I get a quiver full of arrows shot at me, let me explain. For each individual, there is a certain draw length that will work best for them. If that individual decides to try for more performance by increasing his draw lengtn, almost always his form and accuracy will suffer. (I happern to knnow this from the school of hard knocks). A much better aproach is to figure out your comfortable and accurate draw length and use the bow that fits.

For example, I draw to 27" and am comfortable with approx 50 lbs, so my bows are 53-54 @28.
My buddy draws to 30" so he has 45@28. Our speeds are virtually identical with similar bows.

So my motto is shoot the draw and poundage you're comfortable with and the speed will take care of itself.

[KSdan]

I like the original question and it seems that we are crossing/confusing the point in question:  Seems to me that the question is NOT about increased poundage with a longer draw-

BUT given two identically designed bows drawing the same wt. arrow, at the same poundage, with consistent form, BUT one has a power stroke of 30" and one 28".  Would the 30" give better speed?  

Answer: I would sure think so.

[Biggie Hoffman]

This doesn't add anything to the "science" of what you guys are talking about but the only time I was around a chronograph, I had a 65# 21st Century Longbow and 750 grain arrows. With my 32" draw it shot a consistant 212fps.