Bow Performance 55 @ 28 vs 55 @ 30

[michigan bill]

i've been following the thread since the beginning.  suddenly, i am very tired...
bill

[Christov84]

Thanks for all the answers guys!

Now how 'bout another question:  are longer limbs faster then shorter limbs?  :D  

Cheers,

Chris Mallett

[Christov84]

John,

I read your article about bow performance, thank you very much that clears a lot up for me.  Excellent piece thank you. One question though, on page 6 the table about DE has the ACS longbow more efficient then the new ACS recurve.  Is this a mistake or if it isn't any chance you could explain why?

My apologies if this is wandering off topic.


Chris M

[John Havard]

Chris,

I'd be glad to explain.  The ACS recurve has very high DE for a recurve because we're able to make the limb tips very thin through the use of ACS cross-sectional geometry (don't have to make portions of the limb wider or thicker in order to make them stiffer).  However, any recurve limb tip is heavier than the limb tip of a longbow - especially the limb tip of an ACS longbow.  Therefore more of the stored energy is spent in the acceleration of the limb tip forward = lower DE.

Where the ACS recurve makes up for its lower DE (an unavoidable problem with a recurve) is through increased energy storage.  Our ACS recurve stores 7% more energy than our longbow, and is therefore a tad faster in spite of having a lower DE.  In fact (while we're going to wait and let Blacky's third-party impartial test numbers do the talking) I can honestly say that the AMO speeds I have gotten on our ACS recurve tests are at a minimum 2 fps faster than the next fastest bow I have ever tested.

[ChuckC]

Thanks for all the work John.  Now I have to read thru it and TRY to understand it,

ChuckC

[swampthing]

So what would the speed be with a, 66" ACS design, 62# @26.5" draw, shooting a 510g arrow?

[Burnsie]

OK, I'm hanging in there (sort of)but if someone can answer this question for me I think it will make it clear for my little pea brain.
Bowyer Bob builds me a recurve that it is 50lbs at my 28" draw.
Bowyer Bob also builds my buddy the exact same recurve, except it is 50lbs at his 30" draw.
Both bows are strapped in shooting machines and drawn to their respective 28" and 30" draws. They are both loaded with a perfectly tuned 500 grain arrow. Both shooting machines are triggered at the exact same time.  Which arrow reaches the target first?

[wingnut]

Burnsie,

The 30" draw gets there first by about 6 fps.

Mike

With Bear takedowns way back, when we had a truck load of limbs to play with, we found a couple of cases where certain limbs were faster than average and shot about the same and other cases where even a one inch longer draw made 6 fps. I have always been jealous of those long armed guys, but with the Bear takedowns we found that it was about 4 fps per inch either way an inch from 28" on average. Mathematically speaking, I wonder if with any limb length or style there is a point where the increase changes with additional inches of draw, does the fps per inch increase or is there an outside chance that the mechanics of a particular bow can get less efficient with extra long draws? For draws under 28" it does not seem to be an even drop in fps when decreasing the draw multiple inches.

[Christov84]

Guys read John's performance paper (linked earlier in this thread) it really explains it all.  Even if the math is over your head a little, just scroll through to the examples at the end and smile at the awesome  

John, thanks for the response! Sounds like it's time to get saving for a new ACS recurve...

Cheers,
Chris

[Ragnarok Forge]

John,  

I just read thru the link in your earlier post.  I am a die hard Wes Wallace Royal fan. I am going to have to talk with you guys to see if I can have bows made with matching grips or if I can buy bow blanks and form the handles myself.  

 I am looking into African and Australian hunting trips for the wife and I.   She shoots 40 lbs, and I shoot 55.  I have been plotting the purchase of two R/D longbows with increased performance for these hunts. My intent is to get bows that will shoot heavier arrows at speeds matching our existing bows.   I will run the calcs to figure out what weight bow I need to have to shoot a 650 grain arrow at the same speed I am shooting my 560 grain arrows at now.   I will check out your website and see what is available.  

Thanks for posting up your results and links.  I love the technical side and enjoyed learning about your testing process.  You just moved dryad to the top of my next bow purchase list.