String Tension

September 30, 2016, 07:13:00 PM

Here's a tip for you if you are into the numbers on developing and comparing bows to reach a higher level of performance...

I have been comparing and measuring the string tension at a 7" brace height on my 62" string hybrid bows ... The number to shoot for on my bows is double the poundage at 28"... So if you have a 50# bow you would want a 100# or more string tension for good performance... 90% or 90# for a 50# bow may get you up to the 180fps mark or more... There are other variables involved also so this is not a definite but it can be used as a barometer if you stick to one design or similar design bows... Higher string tension definitely makes for a faster bow...

I am curious if anyone else has been measuring string tensions and what kinda results they are getting... Please let me know what string size, style, poundage, brace height, string tension and what FPS you are getting... Thanks... Rich

Dan Landis · September 30, 2016, 07:32:00 PM

Just curious, how do you measure it?

passion for knowledge · September 30, 2016, 08:35:00 PM

The forces acting on a bow string are not static.

The deceleration forces acting on the string as an arrow is shot are much higher than a gentle pull.

A bit along the lines of 'jumping off the roof isn't the problem, it's the sudden stop.

monterey · September 30, 2016, 09:47:00 PM

QuoteOriginally posted by Dan Landis:
Just curious, how do you measure it?

Yeah. I'll play, but I don't know how.

September 30, 2016, 09:48:00 PM

I put a digital scale and a turnbuckle on a bow string...

I am not sure I follow you Passion... Can you explain more in detail?? Or explain why or if you disagree with my findings on string tension otherwise known as preload...
If you take your fastest bows you should find that they will all have a higher string tension than your slower ones...

Dan Landis · October 01, 2016, 09:37:00 AM

In other words you have the scale mounted between the ends of the string, if I understand what you are saying. A pic would sure help me get my head around your set up.

October 01, 2016, 12:30:00 PM

Yes... You have the string loop followed by about 12" of string then one end of the turnbuckle attached to the string and the other end of the turnbuckle attached to the scale followed by more string attached to the other side of the scale then the loop...
Basically just run everything in line with two lengths of string on the ends...

Sorry my friend has my camera and I won't be seeing it until mon. or tues....

kennym · October 01, 2016, 12:46:00 PM

"If you take your fastest bows you should find that they will all have a higher string tension than your slower ones... "

I'll second that, but have never checked tension of string. Surprising that it is that much.

October 01, 2016, 01:51:00 PM

If you have two bows with the same length string just pluck them both like a guitar string and listen to the pitch...

Roy from Pa · October 01, 2016, 02:31:00 PM

So if you have two 50# bows with the same specs, how do you get a higher tension string, other than going to a shorter string?

October 01, 2016, 04:42:00 PM

Start changing up things... Limb angle, lam tapers, profile taper, move your wedges around if you use them, how much reflex or deflex, length of limb, glass thickness...

Use it as a tool like a DFC chart to make comparisons or to see if your changes are going in the right direction... Remember also changes can make or break how a bow shoots...

Wolftrail · October 01, 2016, 05:23:00 PM

Always thought a lower brace height will increase arrow speed. This Is is a performance enhancer, so why increase string tension.

October 01, 2016, 11:50:00 PM

By lowering brace height you are actually increasing string tension... More string tension equals a faster bow...

PEARL DRUMS · October 02, 2016, 08:46:00 AM

And now we know why recurves are generally faster

October 02, 2016, 11:11:00 AM

QuoteOriginally posted by PEARL DRUMS:
And now we know why recurves are generally faster

Are you sure about that???

Wolftrail · October 02, 2016, 12:52:00 PM

QuoteOriginally posted by Shredd:
By lowering brace height you are actually increasing string tension... More string tension equals a faster bow...

The arrow stays on the string longer having lower brace, the tension may be increased at full draw but not brace.

Mad Max · October 02, 2016, 08:17:00 PM

QuoteOriginally posted by Shredd:
Start changing up things... Limb angle, lam tapers, profile taper, move your wedges around if you use them, how much reflex or deflex, length of limb, glass thickness...

Use it as a tool like a DFC chart to make comparisons or to see if your changes are going in the right direction... Remember also changes can make or break how a bow shoots...

The tool IS the Draw force curve chart.
Don't reinvent the wheel

Mad Max · October 02, 2016, 09:38:00 PM

I will take that back.
I have been thinking

(be quite roy)
You band saw blade tention (up and down)is more lb's. than it takes to pull or push the blade left and right lb's

When you are making a self bow the brace profile is different from the long string and the short string.
the short string is pulling from nock to nock in a straight line.

this post could go on and on and on and on

October 02, 2016, 10:18:00 PM

Don't reinvent the wheel... Lol.. Good One...

The tool is the DFC chart??? Yes if you can make an accurate one... How can you truly compare bows if the readings are inaccurate... I have not seen anyone make an accurate one yet... Maybe someone on this forum can...

Measuring string tension is a simple valuable tool that can help you to understand the inner workings of a bow and can help you to achieve higher performance...

Anyone that has an interest in this and wants to discuss it more in detail can PM me... Class is over gents...

Mad Max · October 02, 2016, 10:32:00 PM

QuoteOriginally posted by Shredd:
Don't reinvent the wheel... Lol.. Good One...

The tool is the DFC chart??? Yes if you can make an accurate one... How can you truly compare bows if the readings are inaccurate... I have not seen anyone make an accurate one yet... Maybe someone on this forum can...

Measuring string tension is a simple valuable tool that can help you to understand the inner workings of a bow and can help you to achieve higher performance...

Anyone that has an interest in this and wants to discuss it more in detail can PM me... Class is over gents...

x2