Draw Lengths and Arrow Weights

[Wyrda]

I used to think that 32" was the standard draw now it seems that 30" has been trending as the standard for warbows. Even though I'm only 5'11" I've been shooting a 78# bow @ 32", and using the arrow heads on my knuckles as a reference point. I am sure as I shoot heavier bows my draw will be "compressed", though only drawing to 30" felt a bit weird and unnatural, so for my next bow I ordered 31" draw. It got me thinking though, is there any actual advantage to long draw lengths? I was watching one of Joe Gibb's (a warbow archer who shoots heavy bows) videos where he does a speed test of Mary Rose replicas. https://www.youtube.com/watch?v=OyEc8tkGBJc

What surprised me is that the 28" arrow in a lot of cases was just as good in terms of velocity as the 30" arrow of about the same weight. So basically no benefit for extra draw length. The other thing is though, is that these arrows, even the 75g one, are very light for those poundage bows - so my hypothesis is they are so light the bows have essentially maxed out on velocity (well over 200fps in a lot of cases!) therefore the extra power stroke and draw weight does nothing. So, with a heavy arrow, say 10gpp, would the extra draw length of 30" or 32" give a benefit? And is there any evidence for heavy 1500gr arrows? The Mary Rose ones seem to be under 1000gr.

These results would lead me into thinking that a shorter bow with lower limb mass shooting at 28-30" is going to have better cast that a longer bow shooting at 32". However, Mark Stretton's blog says that 32" is the most efficient draw length and archers should prioritise shooting 32". However, Tim from Black Arrow Longbows recommends 30" for average height men, for easier anchoring. Can any experienced warbow shooters corroborate this, and recommend whether I should aim to shoot 32" or 30" for better cast and accuracy?

[Del the cat]

So many conflicting questions:-
The following is just my opinion.
1. Your draw length, is what you can draw with reasonable control, repeatedly at your desired draw weight. e.g I can draw 32" but it causes me to throw the arrow left as I am over extending, 30" is a sensible maximum for me. For field shooting I used to draw 28", but now 27" is more comfortable (I seem to get older every year... not sure why this is )
2. Longer draw length (at the same draw weight) gives more stored energy, however the bow will probably have longer heavier limbs. Also longer arrows are less aerodynamic.
3. Arrow weight :- there are "standard" warbow arrow specifications with 1/2" and 3/8" shafts and specific weights. There are also  ideas about 10gpp and spine. These all go out the window when flight shooting with heavy bows as I've sot very light weight/low spine arrows from heavy bows (or rather my test pilot JT has)
These factors are all inter-related and it also depends what you are trying to achieve. Do you want to deliver maximum energy to the target or throw the arrow as far as possible?
I have made warbows for flight shooting and some were shorter bows with shorter draw, these were shooting both "standard" arrows and flight arrows.
Any flight bow is liable to explode, and at heavy weights this can be dramatic.
There are no simple answers. IMO, find a full draw that suits you, and go with that. If you want maximum distance, do your own experiments as it is exceedingly hard to get reliable result to draw valid conclusions as the arrow itself has so many variables.
Del

[Wyrda]

My main question was about the benefit of longer draw lengths as the video I watched seemed to contradict the idea that a longer power stroke gave better arrow speeds. However after doing some research and looking at several tests, I've simply come to the conclusion that the findings of tests performed without adequate scientific rigour often return anomalous results that apparently defy principles of physics and thus should be dismissed. For example Mark Stretton's test seemed to demonstrate that arrows shot at long range have more energy than arrows shot at intermediate range, and another test by the author of the Bowyer's Bible apparently seemed to indicate that putting weights on the limb tips gave better arrow speed. So my thinking is to first focus on the science behind the mechanics before being convinced of something seen in a Youtube video or something similar.

[Del the cat]

Indeed, do you own experiments, draw your own conclusions.
You may find this post from my blog interesting.
https://bowyersdiary.blogspot.com/2011/11/mass-velocity-and-energy.html
Del

[Strelets]

Wyrda wrote;

I've simply come to the conclusion that the findings of tests performed without adequate scientific rigour often return anomalous results that apparently defy principles of physics and thus should be dismissed.

Yes indeed.  Many of these tests lack replicate experiments under identical conditions, and without these replicates we do not know what variance in results may be expected.   

[Wyrda]

Indeed, do you own experiments, draw your own conclusions.
You may find this post from my blog interesting.
https://bowyersdiary.blogspot.com/2011/11/mass-velocity-and-energy.html
Del

Thank you del. The relationship between arrow weight and efficiency is well established but I always like graphs. What I am interested in as mentioned, is the relationship between draw length, bow length, arrow weight, and efficiency. For example, we know that a longer draw length stores more energy, but we also know in the case of ELBs, longer bows are more inefficient. So the question is, how fast would a longer ELB drawn to 32", compare to a shorter ELB drawn to 28"? And as I mentioned, I am wondering if the advantage of longer draw length only shows a benefit with heavier arrows, as Joe Gibb's test with relatively light arrows did not seem to yield any benefit drawing from 28" to 30". I have been doing some more research which does seem to support the idea that longer draw lengths are better with heavier arrows in terms of GPP, eg., bows like yumi or Chinese manchu bows with very long draw lengths of 35" or more do very well with arrows of 15gpp or even higher, often shooting them over 170fps . Meanwhile Turkish flight bows optimised to shoot light arrows over 300fps and only have draw lengths of around 28"

I would like to do my own experiments but I don't have the resources right now. This forum has a lot of great info I've been reading but it seems dead now. I assume the warbow scene is still active, is there any place still on the internet for warbow archers to talk that isn't a facebook group?

[Del the cat]

Hi, I don't know of any forums that aren't FB based, except this one, but there isn't much heavy bow stuff on here.
I agree with what you are saying about 28" vs longer draw lengths.
There are just so many variables to play with and one of my favourite engineering techniques is to take things to extremes to prove a theory, but with bows this doesn't really work.
Something I mean to try is a long bow but with short working limbs, theoretically the extra string length gives an advantage.
For flight shooting I think most people make their arrows too heavy, but again there are so many variables in the arrow, not to mention finding that elusive clean loose.
Del

[sleek]

Del, I've been thinking about the long riser with short limbs too, almost built one a couple years back. If I find the right stave, I probably will do it. It would be a fun experiment.