String Tension and Performance...

[Shredd]

               String Tension and it’s Relation to Performance

Higher string tension is the gateway to a better performing bow…  I say gateway because it’s the beginning of getting peak performance from your limbs… It will not be with the highest string tension from your limbs in the end that will give you peak performance…
    The first rule I learned about ST is that it gives you higher performance…  The second rule I learned is that ST does not give you peak performance…
   ST is measured with an inline scale on your bowstring at brace height…  You will find in most cases that the ST of you bow will be under double of what your draw weight is at 28”…  How I find my ST number is a percentage of what my draw weight is doubled…  For example,  ST is 89 lb.  –  bow weight is 50 lb.
                       89 divided by 100 = .89    So my ST is 89%...
A high ST would be over 90%...
    In a nutshell ST comes from how close the string is in relation to the limbs and/or the angle the string is to the limbs…  The closer the string is and/or the lesser the angle of the string to the limb usually results in a higher ST…
   A closer brace height the higher the ST… Reflex through the limb or the tips results in a higher ST… The angle of the limbs off the riser also plays a part in ST… In general, the more the limbs come more in line with the string at brace height the more ST you will get…
    Having higher ST at brace and having higher arrow speed run hand in hand up to a certain point…  The way to give your limbs higher ST is to flatten out or slight reflex if you have a ‘D’ shaped bow or put more reflex if your limbs are reflexed into the outer portion of your limbs… What this does is stiffens up that outer portion of your limb and creates a lever similar to a catapult… The longer the portion of the limb you make stiffer the longer the lever and also the higher the ST because limbs start coming more in line with the string because that stiffened lever is pushing back the bending portion of the limb closer to the riser creating a lesser limb angle to the string… This stiffer outer limb also gives you a better looking DFC in which it gives you higher numbers in the beginning of your draw and lower numbers in the end of your draw also resulting in a smoother drawing bow… This in general is what you are looking for in a DFC for a higher performing bow…
   There are also percentages that the stiffer tips plays in the part of creating a lower poundage bow…  But I am not going to get into that right now…
   You will find that the most highest performing limb of your bow design will be a subtle balance of many things…  For now lets keep it simple…  The balance between the stiffness of the base of your limbs, the consistency of the bend in your limbs, where the bend is in your limbs and the stiffness in the outer portion is crucial to getting the highest performance out of your bow… By achieving this you have created a limb that will cast an arrow at the highest speed it possibly can for that design…
   DISRUPTING THIS BALANCE WILL RESULT IN LOWER LIMB PERFORMANCE..!!
   Now lets say you been tweaking your bow for a while now…  Your DFC numbers are looking better, your ST is getting better, your arrow speed is getting better… So you decide you are gonna tweak it just a little more… You decide you are gonna stiffen up your tips by extending the tip wedge 1” more closer towards the riser…  You measure your string tension and it increased by 2%...  You do a DFC and the numbers look better than ever…  You are excited…  You run your arrow through the chrony and your arrow speed drops by 2 or 3 fps…  You say WTF…  You are perplexed…  What just happened here..??   You say something went wrong with the lams, the layup, the glass…  You try it again…  This time sliding back the tip wedge another ½” towards the riser because you had good numbers last time…  This time a little better looking numbers but another 1 fps slower… 
    Guess what happened..??    YOU DISRUPTED THE BALANCE…   You got higher ST, better DFC numbers and a smoother drawing bow but your arrow speed went down… Now you have a shorter working portion that has to move a longer leaver… Which at some point I believe that longer lever becomes less efficient and starts becoming dead weight…
    This is comparing 2 bows with the same limb design, you will see the numbers will be subtle but they will be there, plain as day…  When comparing 2 different limb designs you could see a big difference in ST and sometimes even see the faster bow with the lower ST, as much as 3 to 4% lower in ST if not more…
   With these carbon super recurves the DFC is off the charts and I can only imagine the ST is 100% or possibly more and they are getting around 190 fps… My fiberglass bow has a ST of about 89% and I am getting 191 to 192 fps…  Performance wise what is wrong here??   LACK OF BALANCE…  That is what I think is wrong… They claim to have the smoothest draw with good performance and I can see that in their DFC’s… But it is not the best performance for the DFC numbers they show…  They sacrificed performance for smooth drawing…  If they maybe concentrated on a higher performer you could drop a pound or two in draw weight and still have the same or more performance…  A lighter drawing bow might be less fatiguing than a higher weight smoother drawing bow…  It’s all a tradeoff… And less big awkward looking limbs to carry around…

   This may be my last post...  Anybody that wants to stay in touch with me can friend me on FB under Rich Redd...  Wish you all the Best...

[jess stuart]

Last post?

[Mad Max]

Good information Shredd 

[Buggs]

Excellent take on balance. I don't correlate numbers, but when a respective limb is bending optimally, you can sense it.

[Kirkll]

Outstanding write up Shredd.  You put a lot of thought into this. Limb balance is a critical part of getting maximum performance.

I’d be interested in your thoughts regarding the fine tuning a bowyer can do  to harvest your existing  limbs max potential.

You have done your lay up, have your limbs mounted, and want the best performance you can get out of them. How would yo go about doing it as a bowyer?  I have certain procedures I use, but would sincerely love to hear how you go about doing this in layman’s terms that some of our beginning bowyers here will comprehend.

The archers that get their new bows can adjust brace height using different length strings, and possibly even using different string material to find the sweet spot. Every bow seems to have a wee bit different brace height to find that sweet spot.
But it’s the bowyers design and balance that makes it’s higher performance possible

Look forward to hearing more from you Shredd….   Kirk

[Appalachian Hillbilly]

One aspect I have seen with higher string tension bow at brace height is they have a different sound. Speed may not  always be the best attribute in all situations.

Of the 2 dozen trad bows I own and most of them are not ones I made, I can listen to the ones with higher string tension  and they have a different tone. To me it is a little louder or maybe I just hear that range better?

I know there are other factors that play with the tone or sound as well.

It is all truly a symphony.  The quietest bow I have is a Treadway 56" bow and it's speed is middle of the pack. One of the fastest that I own ,not of my own design, also is the loudest and takes more arrow weight to bring it down to quiter levels.


Saturday I hunt with one of my newest bows. More string tension and faster than my others.
Tone is different,  my son says he can't tell.

I will see if the deer can!

So many aspects of building bows to consider!

[Shredd]

 Kirk here is your quote...  "I’ve never seen a bow with lower string tension and preload that exceeded performance levels of higher preload bows using a 10 gpp @ 28-30” draw base for testing."

    The subject is on String Tension... What do you have to say about your quote..??  And you can leave out the smack talk...

  Make it good cause I am outta here soon...

[Shredd]

  Hillbilly...  I personally not have had the chance to experiment on this yet...  But I believe in making your limbs reach peak performance and then on your next bow stiffen up the base of the limb a little or the outer portion of the limb a little...  It will slow the bow down a little but it may also be quieter because of how the limb bottoms out at the end of the shot cycle...  Or Not...   

   I have R/D bows that are dead quiet when shot split finger and they shoot 184 fps @ 10 gpp...  My recurves on the other hand are not so quiet...  They shoot from 188 to 192 fps...  I don't know if it's the recurve or speed that makes them louder...  But I shoot 3 under and I am not sure if I tried them split finger...

[Kirkll]

Kirk here is your quote...  "I’ve never seen a bow with lower string tension and preload that exceeded performance levels of higher preload bows using a 10 gpp @ 28-30” draw base for testing."

    The subject is on String Tension... What do you have to say about your quote..??  And you can leave out the smack talk...

  Make it good cause I am outta here soon...

First of all…. I do not intend for this thread to end up in a debate. This is your thread…. No smac talk … total respect… cool head..

There was a time about 10 years ago when I spent quite a bit of time checking string tension with an in line scale when I was trying to seduce a bit more performance out of my recurve design. I was testing different shapes, using different wedge lengths, taper rates, and tip wedge configurations. I was convinced this was a great way to measure preload.

Quite  honestly…I  did not ever run into a bow that had “significantly” lower string tension that had “significantly” higher performance at 10 gpp 28” testing parameters.

You will notice the word I used “significantly” this time….. maybe if I had used that word in my original statement it would not have been contested. In my experience the difference from one bow to the next bow coming out of the same form will have slightly different test results. A few fps one way or the other is to be expected. You get your hot ones… and you get your slower ones. I even looked into buying a high dollar tension meter so I could check my tension more accurately and easier, but passed on that idea after seeing the cost.

Your statement that “string tension at brace is the gateway to higher performance” was excellent. I wish I could have started with an opening statement like that. It’s very true.

This is your thread, and my question stands. Every bowyer has their own way to skin a cat and come up with a finished product. Please read my first post again. I’m very curious on your procedures used in developing a higher performance bow.

This isn’t about how I build bows… this is your spot lite.        Kirk

[Mad Max]

Humidity has to be a factor for testing bows.
More than likely they don’t have a finish on them yet.
And the humidity was higher or lower the day you tested the bow you are comparing the new design to.

I keep my bow room dehumidified but I’m not interested in doing all that testing now.

[Buggs]

Famous last post(s)?  Why? because you have been dissed?

[Kirkll]

Humidity has to be a factor for testing bows.
More than likely they don’t have a finish on them yet.
And the humidity was higher or lower the day you tested the bow you are comparing the new design to.

I keep my bow room dehumidified but I’m not interested in doing all that testing now.

I tried setting up a 12x12 insulated room with a dehumidifier years ago for wood storage and bows, and the cost wasn’t worth the efforts to me. It ran my electric bill up $70 a month running that thing.

You are right about all the testing being very time consuming to get accurate results. There are many ways to skew the numbers on a chronograph too. Lighting is a huge factor. Type of shafts and tips used , fletching or bare shaft, string used, Etc … etc… it’s really difficult to get apples and apples comparison from one bow to the next.

I’ll bet you are right about humidity being a factor too. Look at the draw weight changes you get in board bows or self bows at different times of the year. MC levels change the physical properties of wood.

I got away from all the DFC charts and speed testing myself after getting though the prototype stage on new limb designs. But every now and then I check a hot one out on the chronograph just for fun….  Kirk

[Mad Max]

It raised my bill about $30.00 but once you get everything dry in there it doesn’t have to run so much.
In the winter time it doesn’t run much at all.

[Kirkll]

i'm fighting a loosing battle here in oregon. From late september to late June every stick of wood in my shop runs about 11-12% MC level and lowers during the summer months. Sometimes i'm good thru October.... Depends on when the rains start in again.

 But once I have a dried piece of 8/4 stock below 9-10% the moisture reading is higher on the surface than the core of the wood in winter time and it can easily be dried out as you build your bow. I do my riser construction way ahead of my bow if possible so i can put it in my spray booth where i keep it heated and at a much drier humidity level too. In winter months i'll get a pretty good stack of riser blocks stashed in there to keep them stable.

The thing i really need to watch carefully is where i'm shipping a bow. On bows going to a real dry climate, i'll get the riser shaped and hang it in the spray booth for a couple days in 90 degree temp. In winter months i factor an extra day or two just for MC stabilization before spraying clear coating. If i don't do that it could shrink a bit when it acclimates in a desert dry environment.  i've had to refinish a few that i didn't get dry enough. The ones with G-10 I beams need to be bone dry or i have issues. Those always get an extra day or two in the spray booth after shaping the riser. I just use incandescent light bulbs for my heat source in my tiny spray booth. Works well ....    Kirk

[Mad Max]

Yeah our summer times are very hot most years with 80%/90% humidity also.
I have to run a A/C window unit just to stay in the bow shop.

[Kirkll]

I run a big swamp cooler with a 10" squirrel cage that blows right across my work bench, but i dont have any water hooked to it. So its just working as a fan. With no insulation and high ceilings, an AC wouldn't work in my shop. Once it gets over 90-95 degrees i just shut it down until it cools off in the evening. Then if i don't eat too much at dinner I may go out again for awhile.... typically not..

[onetone]

Shredd - you have any sources for a tensiometer that works for testing string tension? I’d like to investigate that some and how it relates to reflex.

[Shredd]

Famous last post(s)?  Why? because you have been dissed?

   Nah...  That petty attempt at bullying does not bother me... Lots of hot air and zero class...    What bothers me is misinformation given to you guys...  I am very passionate and worked very hard to get where I got in this craft and would like to see anyone make good gains to improve their bows performance... When you make a statement like, "The speed and performance of your limbs is completely dependent on preload string tension at brace."  Some poor sucker may take that to heart and 4 or 5 bows into it end up with a bow at 95% string tension shooting 172 fps, scratching his head, saying where did I go wrong...  It's so critical that you say the right things when handing out info...  Achieving better performance can be elusive so you need all the chips stacked in your favor...  If it was easy everyone would be making 190 fps bows...

   If I stay on I will be battling it out about once a month with is guy...  I don't want that negative energy for the forum and I don't wanna be involved in wasting time, energy and losing sleep over crap like this... This is Bowyer 101 basic chit and he should be all over this and should have seen the light when I posted my first comment... This arguing stuff is just not my style...  Besides I learned mostly what I need to know on this forum although you can always learn more and what I have to offer, most are not interested in so my time here is done... As for performance Kirk will get you 75 to 85% there...

  Kirk as I told you before, I know of about a half dozen holes in your game and can prove them wrong...  Please watch what you say to the Brothers...  I am sure you would not want them wasting their time and money going down some rabbit hole...  As far as this "significant" thing...  All totally sounds like backpedaling BS to me...  Makes me question your methods and/or your accuracy of testing...  When you gain 2 to 3% string tension and lose 3 to 4 fps that sounds pretty significant to me...   You better triple check your notes Bro...
   Your attempt at belittling and berating me makes you look like a shmuck... Especially when I proved your statement wrong... Hope you man-up and straighten out...

   Signing Off...   Rich Redd

[Shredd]

Shredd - you have any sources for a tensiometer that works for testing string tension? I’d like to investigate that some and how it relates to reflex.

   A tensiometer is not gonna be nearly as accurate as a inline scale...   And for a good one they will probably be expensive....   

    Lets think about this for a moment...  How would your test your tensiometer for accuracy...  My guess is you would hang a 100 lb. weight on a string and hook up a tensiometer to the string...  How do you measure the weight to make sure it is a 100 lb. ??  By using a scale...  So why not just put a scale between two pieces of bow string...  I think tensiometers are used when you can't have a scale in the middle of a wire or cable because it is fixed in place....  A simple inline scale will work for you...  For luggage or fishing...  Make sure you measure all your bows at the same brace height to keep things accurate and fair... Or keep notes at what brace height you tested it at...  Put a turnbuckle on your bowstring to adjust the brace height...

[Kirkll]

Good grief…. Where on earth did all  that come from?

All I said was I’d be interested in how you go about getting the best performance out of a limb once it’s mounted on the riser, and share it in layman’s terms with the guys here… this is not about how I do, or do not do things. This is your thread. You can do what you want with it….

A lot of bowyers are just not into all the detailed testing. You of all guys know how much time is involved. But ….. there are certain techniques and procedures that can be used and incorporated into your build to refine and balance things out without all the DFC charts and in depth testing, and still come up with some excellent products. There a lot of different ways to skin a cat…. I was just curious how you go about it…. You know… kind of walk the talk a bit in layman’s terms.

No pressure … it’s your thread.    Kirk