Brace height and speed

[DC]

In the TBB it mentioned that a lower BH gave a higher speed. I've found the opposite. I was just testing a bow and at 3.5" BH I was getting about 3 FPS less than at 4.75" BH. I'm wondering if 3.5" is just ridiculously low and I'm not getting a clean release. Anyone else notice anything funny?

[Tommy D]

Do you think if the bow was center shot it would not reduce the speed? Perhaps the fact that the arrow has to paradox more might be the reason?

[bownarra]

If it was a true centershot...you might find it keeps climbing? Having the same arrow bending further and further (releasing from the string later) at a lower and lower brace, eventually you will see what you saw
Like most things in bow making the physics even out one gain with another loss

[bradsmith2010]

 agreed bout that,, if the arrow is not tuned well you will experience loss of speed as well
but a reasonalby low braced bow with arrow thats tuned to that,,, can shoot well,,

[mmattockx]

In the TBB it mentioned that a lower BH gave a higher speed. I've found the opposite. I was just testing a bow and at 3.5" BH I was getting about 3 FPS less than at 4.75" BH. I'm wondering if 3.5" is just ridiculously low and I'm not getting a clean release. Anyone else notice anything funny?

A lower brace height generally increases energy storage in the bows I have modeled, but that doesn't necessarily mean faster arrows in the end. Why not continue your brace height experiment up towards 7+" and see if there is a sweet spot in there somewhere?


Mark

[DC]

The arrow is not optimum that's true. My machine breaks wooden arrows so I had to go to a carbon. I have two carbons(500's) with screw in tips. I have 7 tips of various weights and I ballasted the arrows so the light arrow goes from 32 to 38 lbs and the heavier arrow goes from 39 to 45. The lightest tip is 65 grains and the heaviest is 125. It's quite obvious that most of the combos will be wrong but it's the best I've got at the moment. I did notice on one bow that I gained a couple of fps when I filed the arrow pass a little deeper. Don't know if I have enough wood to go centershot. They are already starting to look like a FG bow and I'm not to pleased with that

[DC]

In the TBB it mentioned that a lower BH gave a higher speed. I've found the opposite. I was just testing a bow and at 3.5" BH I was getting about 3 FPS less than at 4.75" BH. I'm wondering if 3.5" is just ridiculously low and I'm not getting a clean release. Anyone else notice anything funny?

A lower brace height generally increases energy storage in the bows I have modeled, but that doesn't necessarily mean faster arrows in the end. Why not continue your brace height experiment up towards 7+" and see if there is a sweet spot in there somewhere?


Mark

5 1/4" got me to 198(about+2) and 6" was the same so I stopped.

[bradsmith2010]

wow nice, you almost there,, you can do it,,
   Im just thinking out loud, but if you had a lighter spine  arrow that would shoot at 4 inch brace you might hit the 200
I was testing a bow the other day,, and did gain couple fps when I got down to about 4 inches brace,,

[Selfbowman]

The arrow is not optimum that's true. My machine breaks wooden arrows so I had to go to a carbon. I have two carbons(500's) with screw in tips. I have 7 tips of various weights and I ballasted the arrows so the light arrow goes from 32 to 38 lbs and the heavier arrow goes from 39 to 45. The lightest tip is 65 grains and the heaviest is 125. It's quite obvious that most of the combos will be wrong but it's the best I've got at the moment. I did notice on one bow that I gained a couple of fps when I filed the arrow pass a little deeper. Don't know if I have enough wood to go centershot. They are already starting to look like a FG bow and I'm not to pleased with that

DC how bad do you want to go fast?  If you want it to shoot like a FG it needs to kinda look like one only thicker.😁😁😁😁all in fun with some truth. Arvin

[Sagebrush]

DC you make fast bows!!!  I think an FD curve would give you the answer.  I think less than 5 inches of brace height would lose efficiency (not to mention bugger your wrist).  In target recurves we would see a speed drop off above about 7 3/4.

[bradsmith2010]

   if your at 198,, there is a brace height and arrow that will do 200,, and maybe string strand count,, I feel like the loss of speed at lower brace is more about the arrow ,, than the bow,,
   I was testing a few days ago,, I had two arrows, the heavier arrow shot faster,,,, it was coming off the bow smooth,, the lighter arrow was too stiff and even though lighter, it was about 5 fps slower,,,

 

[DC]

 I've done a few FDC's and haven't gotten much out of them. They all(for my RD's) look similar. Just a little bit fatter than a straight bow but nothing jumps out at me. Maybe someone with a more experienced eye would spot something. This one has stiffer outer limbs and I'm wondering if the limb harmonics that Badger and Alan were talking about are helping me. I had just posted that I had the best luck with more reflex and then this one gets better when I cut the tips off. I keep thinking that the FDC only shows what's happening when you draw the bow, not when you release it.

 These test arrows are 500's. I may go looking for a 600. Do you have any clues that stiffer kills speed more than limper. Obviously perfect spine would be ideal but that's hard to do with an adjustable system. If I optimise it for this bow it will probably be wrong for the next one.
 

[bradsmith2010]

  I dont think its really stiffer kills the speed,, but an arrow that is not matched, I think it could go either way,, if your wood arrows were breaking hitting the target,, it would might indicate they are not matched,,they should hit straight enough not to break,,the arrow I was testing that lost speed was hitting a bit sideways,,
  just to be clear, I was hitting high 170's with a short draw bow,, I shot it again with lower brace and was bout 182,,
it could have been my release,, nothing scientific,,,,but wouldnt hurt to try everything to get your 200

[DC]

As best as I could with the arrows at hand it was weight that trumped everything else. I had two arrows, one static spined at 35#, the other at 60#. They both shot the same speed. It was kind of inconclusive because one was too stiff and the other was too limp although the 60 should have been close.

[mmattockx]

  I dont think its really stiffer kills the speed,, but an arrow that is not matched, I think it could go either way,,

This isn't speed related, but the Olympic archers prefer a set up that is slightly weak spined to one that is slightly stiff because the weaker set up is more forgiving of archer errors. The same may be true for DC's speed quest. Of course, if it is way off then I don't know that it matters much which way it is off.


Mark