String Tension

Max I did not see your last post when I was posting my post...
 Trust me, more tension = higher performance...
So measure the tension if you want to compare bows with numbers to fine tune your design...

[mikkekeswick]

Recurves store more energy than straight bows hence the speed difference. String tension on a recurve is related to the reflex in the bow just the same as any other bow design.
Wolftrail string tension at brace is a factor determined by the preloading of the limbs eg. how reflexed the unstrung bow is. what the OP is talking about is nothing to do with adjusting brace height.

[BenBow]

BTW sting tension goes down as the bow is drawn. It has to do with string to ilmb angle and leverage. Took me a while to wrap my head around that. One would think that as draw weight went up so would string tension but that's not the case. Shredd do you have any numbers with your rig other than at brace?

Finally...  Somebody talkin' My language...  No I did not record any numbers on drawing a string but only at different brace heights... But you are definitely right about tension going down as you draw... If you push in on the string towards the riser the tension goes up...

  Here are a few numbers on a 43# hybrid...

Brace  --  Tension
7 1/2"  --  74.54#
7 --0"  --  76.24#
6 3/8"  --  78.97#

[monterey]

So, are those numbers derived from pushing the string in towards the riser?

It would seem that the way to compare tension at brace height would be with a brace height reduced with a longer string.

Not entirely clear on the theory you are talking about, but since Ben is somewhat on board, I guess there may be something to it.  

Those are brace heights...  No pushing on the string... No theory just facts...  Just as a longer draw will give you a faster arrow...  More string tension will also give you a faster arrow...

[Roy from Pa]

Geeze, now I gotta fugger string tension into my trilams. Heck I might invent a round thing ah ma jig and glue it on the end of the limbs. I'll call it a wheel.
LOL Rich, no harm intended.

[frank bullitt]

Pope wrote about string tension in his book. Page 79, in chapter 5, how to make a bow!                                                                                    

Nothing new. A good read!

[Mad Max]

Roy, you need a wheel, yours is shot! LOL    

Shredd
How does that work on a Static recurve?
How many lb. are you looking for 86 ?

[BenBow]

Mike don't say things like that, you don't know how screwed up I am. And no comments from the peanut gallery Roy!

[die_dunkelheit]

What you are describing is ultimately a function of string angle. Consider the values given by Shredd:

Originally posted by Shredd:
Brace  --  Tension
7 1/2"  --  74.54#
7 --0"  --  76.24#
6 3/8"  --  78.97#

As the brace height goes down and the string gets closer to the belly the angle between the string and limb also goes down.

String Angle refers to the actual measured angle between the limb and the string when measured at the nocks. The tighter the better. The mechanics behind this are similar to that of a hammock and the angle of the suspension lines. As that angle is reduced the tension increases radically using T=mg/2sina where "T" is tension, "a" is angle, and "mg" is load applied by the limb.



This isn't perfect because we aren't actually considering a static load as in the equation, but it works to explain the relationship of string angle at the nocks to cast speed.
This explains the seemingly paradoxical pattern that though the limb is less loaded by a lower brace height the tension in the string goes up.

[Roy from Pa]

Not gonna say nuffin, Benny Boy...

Well said Ghost...

  Max...  I only mess with R/D's  A recurve is a different animal...  My guess is that it would be a bit higher because at brace you are actually dealing with a shorter limb which could give you a bit more tension...

[BenBow]

Now that's what I'm talking about Anthony!
Thank you Roy, you're becoming more of a gentleman every day but dang you're setting the bar high and I need to clean up my act.    

[mikkekeswick]

Originally posted by Shredd:
Well said Ghost...

  Max...  I only mess with R/D's  A recurve is a different animal...  My guess is that it would be a bit higher because at brace you are actually dealing with a shorter limb which could give you a bit more tension...

No string tension is determined by how much reflex the bow has unstrung. Recurve or longbow - it doesn't matter, just total reflex. It is only comparable one bow to the next at the same brace height. If you want more string tension then you should use more reflex. It is as simple as that.
It is more a byproduct of a good design rather than a specific thing to aim for on its own.

[die_dunkelheit]

Originally posted by mikkekeswick:
 

Originally posted by Shredd:
Well said Ghost...

  Max...  I only mess with R/D's  A recurve is a different animal...  My guess is that it would be a bit higher because at brace you are actually dealing with a shorter limb which could give you a bit more tension...

No string tension is determined by how much reflex the bow has unstrung. Recurve or longbow - it doesn't matter, just total reflex. It is only comparable one bow to the next at the same brace height. If you want more string tension then you should use more reflex. It is as simple as that.
It is more a byproduct of a good design rather than a specific thing to aim for on its own. [/b]

That argument implies that string tension is totally dependent on limb load. What you are saying is basically; "The further reflexed the limbs are the greater the load when braced thus the string tension must be higher." But it fails to answer why when measured from a lower brace, thus the limbs are less loaded, does the tension go up instead of down?

Does reflex (and thus limb load) play a part here? Yes, but the string angle affects how the limbs impart that load into the string.
The really cool thing is how string angle does one thing on draw, but something very different in cast. But that's a different story and a lot more math..

Shredd,
You got it buddy, recurves unlocked a couple things in archery when someone accidentally discovered them. One, you have compounded lengths at work as it gets longer as it is drawn. Two, the string angle is consistently lower throughout the draw as the string angle is never higher than the angle between the limb and the string at the point the string breaks contact with the limb.

In part, my reference here and in my initial response was TTBB vol. 1 chapter 3 wherein Tim Baker discusses the effects of various elements of bow design; my other reference is my love for physics which, like Honest Abe, never lies.

I thought the question was on general percentages... Where recurve's draw wght to tension will be different to an R/D...
  So you are saying that reflex only determines string tension.?? Not other variables like limb thickness, glass thickness and length of limb.??

 I agree it is a by product just like arrow speed, DFC and draw weight... And they all can also be measured to see what direction you are headed when making and designig bows...

My post was directed at Mike...

Hey Ghost... I am interested in you cast/string angle theory...  If you get some time pm me or post it on the forum... Would love to see it... Its been something I been thinking about recently...

[Mad Max]

Shredd
what kind of speed's are you getting with 10gpp?