OK so first of all let me say i dont want to get into a discussion on the need for speed, i just like to play around and test bows!
so i was trying to do a comparison test on numerous bows that i have to see which was faster. They are all within 2# of each other, i am using the same arrow at 9 gpp, same release, etc. i THOUGHT i was drawing to the same draw length every time by making a mark at 30" on the arrow and having someone watch the mark to make sure i did the same thing every time. Now here is the question - is it fair to say the back edge of the riser is the point at which i should draw the arrow to for my 30" draw length measurement? since all risers have different depths (shelf lengths) am i short changing some bows. for example the schafer shelf is over 2", the toelke is only an 11/4", etc
How do i make sure i am drawing the same on every bow?
mike
Mark an arrow at the pivot point of the grip at your draw.
wouldn't think measuring to the back would be any more consistent. Are you using a shooting machine or just drawing like normal. The way I compare is to shoot each bow three times trying to make sure I hit my anchor consistently. Average that out and you will have a good idea of that bow with your normal draw.
I would suppose the most accurate measure would be to draw each arrow the same distance from point of rest, or in other words, make the power stroke the same length. If one bow has a 7" brace height, and another bow a 6" brace height, the bow with the 6" brace height would have a longer power stroke if they're both drawn to the same distance from the pivot point of the bow.
That said, in testing I've done, changing brace height on a bow has little effect on it's speed maybe a foot or two per second.
Since you're concerned about how the bows perform for you, draw them all to the same distance from the belly of the grip, which would be your normal draw length, and see how they perform. That would be the true draw length.
I would suggest this:
1) Mark the ground to place your feet on the same spots.
2) Place the chrono out at an identified place, mark where this is if testing takes a few days.
3) Shoot a 20-50 shot string from each bow concentrating on good form and anchor points. Record only the average speed and standard deviations for each bow. Make certain to use only the same arrow for all of the testing.
Doing this will give you a better idea of relative speeds between bows as you naturally shoot them as well as give you an idea of how consistent you shoot each bow as related to speed.
For what it's worth, I shoot through my chronograph on days I go out strictly to work on form only to help objectively see how consistent my draw and release are as based on deviations in velocities. I set the chronograph to start clocking the arrow about 40" in front of my bow and use only one arrow over and over. I put the chronograph at about 40" in front of me so that it's right up close and I don't have to concentrate on aim to not hit it as well as so that it'll clock my arrows right after they have cleared my bow for a quick reading of what's happening at the release.
The distance from the deepoest part of the grip to the front of the bow will be 1 3/4 on most bows. You measure to from the string or deepest part of the arrow nock to the extreme front of the bow site widow. Nock to outside extremity of riser When the bow is put on the machine the fulcrim is the deepest part of the grip/That is what locates on the machine/ most testers deduct 1 3/4 from the draw length that they want to test / That would make 26 1/4 from the grip to the release of the bow when drawn/
Hope this does not confuse/ Manufacturer sets the length of power stroke with his reccomended brace height/ The tester sets the string to reccomended brace/ You do not set all bows to same brace to test them. If you are testing for 28 inches it is 26 1/4 from the deepest point or fulcrim of the grip/. All of them are pulled to that point. For instance all my bows are set at 7 1/4in brace. I design the limbs for that/ some bowyers vary with models/ if theirs is 6 inches to brace then they have 1 1/4inch power stroke over my bow. Their blessing , my problem/
God bless, Steve
no shooting machine - just me and a helper (daughter).
i think i need to get a consistent measurement from the grip - everything else will be inconsistent. I think 1 3/4" from the grip was what i remember from wheelie days. i think i can move my mark on the arrow back to 28 1/4" and draw that mark to grip.
i have to say GDPolk's idea makes sense - should be able to do the same form every time - right?
QuoteOriginally posted by Sixby:
The distance from the deepoest part of the grip to the front of the bow will be 1 3/4 on most bows. You measure to from the string or deepest part of the arrow nock to the extreme front of the bow site widow. Nock to outside extremity of riser When the bow is put on the machine the fulcrim is the deepest part of the grip/That is what locates on the machine/ most testers deduct 1 3/4 from the draw length that they want to test / That would make 26 1/4 from the grip to the release of the bow when drawn/
Hope this does not confuse/ Manufacturer sets the length of power stroke with his reccomended brace height/ The tester sets the string to reccomended brace/ You do not set all bows to same brace to test them. If you are testing for 28 inches it is 26 1/4 from the deepest point or fulcrim of the grip/. All of them are pulled to that point. For instance all my bows are set at 7 1/4in brace. I design the limbs for that/ some bowyers vary with models/ if theirs is 6 inches to brace then they have 1 1/4inch power stroke over my bow. Their blessing , my problem/
God bless, Steve
What I was trying to say. :campfire:
Daughters are good. I got one and she is my best helper./
God bless you all, Steve