348 FPS?
02-20-2003, 07:14 PM
#21
Join Date: Feb 2003
Location: Murrysville PA USA
Posts: 119
RE: 348 FPS?
ORIGINAL: PABowhntr
Krisken,
I do not mean to be argumentative but this is not necessarily a true statement. For example....
...When you increase bow poundage you will have an average gain of approximately 1.75 fps for each pound of draw weight. ...But since you are increasing arrow weight by 50 grains to keep the ratio at 5 grains per pound you also need to subtract approximately 10 fps. ...I did not want to seem like I was lecturing but this is a commonly misunderstood issue.
Bow poundage wont do a thing for x-tra speed if you remain at 5gr. per. pound.
I do not mean to be argumentative but this is not necessarily a true statement. For example....
...When you increase bow poundage you will have an average gain of approximately 1.75 fps for each pound of draw weight. ...But since you are increasing arrow weight by 50 grains to keep the ratio at 5 grains per pound you also need to subtract approximately 10 fps. ...I did not want to seem like I was lecturing but this is a commonly misunderstood issue.
KE = m*v*v/2 = energy stored in the bow * bow efficiency = S * E
v = square root of ( S * E * 2 / m)
Increasing the poundage increases the stored energy at the same rate as the mass is increased and the velocity is unchanged, if one shoots the same grains per pound.
I.e., Krisken is exactly correct as long as you keep all the efficiencies the same.
02-20-2003, 09:27 PM
#22
Join Date: Feb 2003
Location: Detroit
Posts: 858
RE: 348 FPS?
All I know is this guy has a 3 year old PSE and shoots 327fps??? How the hell? He says he pulls 90#, but I made him put it on the scale and it was maxed at 86#. He also told me he shot 6.5 grains/ pound, but I didn' t weigh the arrows so???
02-21-2003, 06:23 AM
#24
Boone & Crockett
Join Date: Feb 2003
Location: Lehigh County PA USA
Posts: 12,157
RE: 348 FPS?
bprepn,
Not to contradict you my friend but my above example is right on the money for a majority of the bows out there. There is a larger speed increase for the increase in draw weight in comparison to the decrease in speed for the increase in arrow weight.
I would be more than happy to do this comparison on any bow out there.
To put it very simply, a 70 lb peak draw weight bow shooting at 5 grains per pound of draw weight will shoot several feet per second faster than a 60 lb peak draw weight bow shooting at 5 grains per pound of draw weight. One effect does not equally cancel out the effect of the other. Equations on paper are fine but practical experience tells me otherwise.
Not to contradict you my friend but my above example is right on the money for a majority of the bows out there. There is a larger speed increase for the increase in draw weight in comparison to the decrease in speed for the increase in arrow weight.
I would be more than happy to do this comparison on any bow out there.
To put it very simply, a 70 lb peak draw weight bow shooting at 5 grains per pound of draw weight will shoot several feet per second faster than a 60 lb peak draw weight bow shooting at 5 grains per pound of draw weight. One effect does not equally cancel out the effect of the other. Equations on paper are fine but practical experience tells me otherwise.
02-21-2003, 01:07 PM
#25
Join Date: Feb 2003
Location: Imperial, MO
Posts: 140
RE: 348 FPS?
PABowhunter,
I never tested this with two different cams but you are correct if we are talking about the same cam set at 60# and then at 70#. I have always been told and have read a cam is always designed have the highest efficiency at it highest draw weight and longest draw length.
Have you tested this with two different cams? A max at 60# and a max at 70#.
Toby
I never tested this with two different cams but you are correct if we are talking about the same cam set at 60# and then at 70#. I have always been told and have read a cam is always designed have the highest efficiency at it highest draw weight and longest draw length.
Have you tested this with two different cams? A max at 60# and a max at 70#.
Toby
02-22-2003, 04:20 PM
#26
Boone & Crockett
Join Date: Feb 2003
Location: Lehigh County PA USA
Posts: 12,157
RE: 348 FPS?
Toby,
Sorry it took so long to get back to you. I have tested it on several different make and model bows. Both a 60 and 70 pound peak draw weight comparison as well as one bow set at 60 and 70 pounds. There is a much more pronounced difference with the latter but there is still a difference in speed with the former as well.
However, the actual speed difference varies significantly from model to model and also depending on the grains per pound of draw weight ratio being used. Some bows might only see a speed difference of 2-3 fps whereas I have shot others that varied by 8-9 fps (60 and 70 lb peak draw weight comparison). My suggestion of 7 fps was the easiest to actually prove using the normal generalizations, however, 4-5 fps would be more of the average of what I have found.
Sorry it took so long to get back to you. I have tested it on several different make and model bows. Both a 60 and 70 pound peak draw weight comparison as well as one bow set at 60 and 70 pounds. There is a much more pronounced difference with the latter but there is still a difference in speed with the former as well.
However, the actual speed difference varies significantly from model to model and also depending on the grains per pound of draw weight ratio being used. Some bows might only see a speed difference of 2-3 fps whereas I have shot others that varied by 8-9 fps (60 and 70 lb peak draw weight comparison). My suggestion of 7 fps was the easiest to actually prove using the normal generalizations, however, 4-5 fps would be more of the average of what I have found.
