String Tension

[die_dunkelheit]

Originally posted by Mad Max:
die_dunkelheit

"more educated about what makes a bow efficient so that we can achieve above average cast speeds with a given draw weight".

two bows off the same form, one 30# the other 50#
will they cast the same speed with 10gpp ?

How on earth did you take something that ridiculous away from my post? My interest here is what makes them efficient. As in what design elements. If you can effect a change in the design that makes your 50# bow shoot faster without sacrificing a smooth draw would you scoff at that too?

[Mad Max]

I have been wondering about the speed for some time now so I thought this would be a good time to ask.
I'am not trying to take anything away.

I find this whole post very interesting.

[die_dunkelheit]

I'm sorry Max, my dyslexia kicked in pretty hard when I read your post and I fired off a half cocked response thinking I'd been insulted by some kind of mockery. I'm sorry about that.

[Mad Max]

cool

[EwokArcher]

Wow...

[mikkekeswick]

30# and 50# off the same form will not cast a 10gpp arrow at the same speed. They will be close because the design is the same BUT thicker limbs return faster. Thinner limbs return slower.

String tension isn't something to really think about - it is a byproduct of a good design.
Keep It Simple Stupid!
All things have to be equal to compare one bow to another. If two bows have different brace heights you can't make a direct comparision.

[Mad Max]

mikkekeswick
Thank you for that Info.
when I started doing tool and die work in the 80's we always used the KISS factor.

[die_dunkelheit]

Originally posted by mikkekeswick:
String tension isn't something to really think about - it is a byproduct of a good design.
Keep It Simple Stupid!
All things have to be equal to compare one bow to another. If two bows have different brace heights you can't make a direct comparision.

Okay, there is some miscommunication of what I've been trying to say. All I've been trying to say is that by adding some mid-limb reflex or changing the degree of recurve you lower string angle, and string angle is key. Tight string angle reduces stack, and speeds up cast. The only difference between the hypothetical bows in comparison would be recurve, mid-limb reflex, or otherwise that effects string angle; not draw weight or brace height. So the point being when designing your next bow, as in literally the form on which you will glue it up, keep in mind the angle between the string and the limb at the tips when braced and what you can change in that design to lower the string angle.

BTW, My interest in string tension here is only that it illustrated the effect of the string angle.

I been away with no internet and wrassling with a hurricane...  
   I see you boys been chatting it up...  

   There is something beautiful about simply making a bow a shooting it... There is also something beautiful about delving deep into the inner workings of a bow...
    Some may use a rule of thumb, copy other designs and come out with a good shooting fairly fast bow that looks pretty... Some others get off on developing their own design and shoot for a high performance bow that shoots well...
   If you are into pushing the limits and producing a high performance bow I would think you should arm yourself with every tool available to give you better insight into the inner workings of a bow...  Yes, string tension is a by product... But it can be measured and used as info into figuring out how to get better performance... If you have two similar bows and they have the same string tension or DFC and one shoots 10fps slower than the other... Or two bows are similar but one has more string tension... Knowing certain info can help you to narrow down how to improve a bows performance... I think its kind of a shame to have a good designed bow shooting 10- 20fps less than it is capable of because of a lack of knowing its full potential...

   Some of you are making this sound way more complicated than it is...  Just put a scale on a string, measure the weight at desired brace and record it to compare to other bows to help you narrow things down...  Pretty simple...  If you choose not to do it...  It is fine... If you chose not to measure arrow speed, arrow wght,string angles and draw weight, that is ok also...    

[jess stuart]

Good info Shredd!  I see it as just another method to improve a bow design.  Just like using a force draw curve, a tillering tree to observe how and where the limbs bend etc.  I see no downside to finding out what string tension is, and using it for future modifications.  Thank you for sharing your thoughts and findings with us. Gains in performance are often made in very small increments and this should certainly help.

[Mad Max]

shredd
I like this post
Your info is very interesting to me.

Tip weight, or less of it will speed up your arrow.
Narrow/thicker tips.

 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=012157#000000

Thanks Jess....  Yes...  If you only measure draw weight, arrow weight and arrow speed you are kinda working blind if you are looking for improvements... Like you said, Gains can come in small increments and you would never see them without them numbers...
   DFC's are a good tool also but you are pissing in the wind  if you are trying to compare bows and they are not accurate...  I go more by the numbers than the curve... Maybe that will be a good topic to discuss...

 Max...   Yes I wanted to talk to you about that...  I tried to message you last night but the message boss said I can only write you after you write me back...  What a jip...  I like your design and was gonna suggest molding some carbon fiber for your tips...

[jess stuart]

DFC would be much more helpful if we can come up with a consistent method of getting the exact draw length.  Just a quarter inch either way and the DFC is off, probably not significant in the big picture but, if we want to squeeze every bit of performance out of a design, well then it is.

Jess it doesn't need to be a 1/4"... 2- 3/100's will start messing things up...

[die_dunkelheit]

Welcome back from the dark Shredd, how bad did it hit you?

I'm still working on that long explanation of string angle. Making some simple graphics to help explain it a little more clearly too.

It was a close shave... Lots of broken branches and debris... No missing shingles...