Explain Draw length

[Marcus]

I've heard reference to people having the correct length arms to get propoer draw length etc. I have heard that the Koreans measure their archers arms to determine if they will make a good archer etc. Can Jim or someone else explain how this works?

[robbo]

Me too, I want to know if I have to give up my dream of world domination.(on the archery course) :D

[James Park]

Marcus,
My understanding is that it has to do with being able to get your bowarm shoulder in close to the arrow and your string arm elbow to the line of force, and simultaneously being able to get an anchor point not too far from the corner of your chin.
If your proportions are not suited to recurve you will find that the anchor point needs to be too far along the side of your face when the other criteria are met. With compound this is not a problem, but with recurve the first movement of the string is towards your face (to the left for a right-hander) and that is a problem.
If your proportions are such that the above cannot be met simultaneously then it is necessary to compromise on one of the aspects of top technique and you will probably not score quite as high as someone who can get them all correct (like Dave).
Hence my comments in the parallel thread on what attributes make a champion.
Another one that is a dead give-away is the apparent length of an archer's neck. If the apparent length is long (eg Marcus) then that archer's shoulders can sit down nice and low and it is easier to use the holding weight of the bow to push the bowarm shoulder down (and hence be successful with the higher holding weights of a recurve). If the apparent neck length is medium (eg Jim) then it is a bit more difficult. If the archer's apparent neck length is short then it becomes quite difficult. The apparent neck length is related to the ratio of shoulder width to chest depth (distance from Sterum to Spine) and determines how low the Clavicle can sit before it bumps into the ribs. This together with the relative length of forearms, upper arms, and shoulder width determine the mechanical possibilities.
I should add that it is far less critical for a compounder because of the greater freedom in anchor point location and lower holding weight.

[Marcus]

So I have a good neck for recurve. Glad it's good for something. :)

So what are the measurements? Can you put up a diagram of an archer and able to say "measure the shoulder width which must be the arm width minus X" or something like that? Is that how it works?

[recurve boy]

Looks like I can have a go at world domination then. Yay!

[Flame]

http://www.archery-forum.com/4sale/20030913141604.jpg

[James Park]

So what are the measurements? Can you put up a diagram of an archer and able to say "measure the shoulder width which must be the arm width minus X" or something like that? Is that how it works?
Yes, that is how I do it. In "Mastering Compound Bows" you can see the diagrams for me shooting a compound. The complicated bit is knowing where the joints actually are - I have used X-rays for this for me. After that, the most complex bit is locating the shoulder joints in their lowest position. Note that to calculate the forces on the joints you have to take quite some care with where they are located - particularly the elbow joints. I measure them in two planes as shown in MCB, and then you can do the maths.
What I would like to be able to do is to have a much simpler process where you can take a few quick measurements, pot them into an equation, and have it pop out a few key parameters.
(Actually: my grand plan is to be able to take two pictures of an archer, one from the side and one from above, then use a remarkably clever computer program to work out where the bones and joints are, and then to have the program draw the bones and joints and calculate the forces, and after that recommend changes the archer should make to optimise his technique. I have started on this a couple of times, but it is quite a challenge to work out where the joints are. The program would be "Accurate Archery", or something like that.)

Flame,
Excellent. Now we just need them to stand up on the hind feet .......

[robbo]

Now I've got a new excuse why I don't shoot so good, my neck is too short. :wink:

[Kuru]

James maybe you could explain this one to me. I have noticed alot of compounders have the string coming up infront of their face and others have the string pulled past their face and have the string on the side of their face. From what I can work out those that shoot shorter ATA bows pull the string to the side of their face and long ATA shooters seem to have the srting pulled to the front of their face touching their nose. Is that to also see better thru the peep site ?

[James Park]

Gareth,
They should set their draw length such that their shoulders are in the correct places and that their string arm elbow joint is on the line of force. Their anchor should then be wherever it comes out.
However, I notice that compounders frequently get this wrong (often too long). The length of the bow should not make any difference (but with a short bow it is an advantage to get the peep a bit closer to your eye).