brace height

Crossbow Hunting

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Postby Pydpiper » Mon Aug 03, 2009 7:30 am

It does change the point of impact, yes. It increases the time the arrow will stay in contact as well as the throw of the limbs, and in turn speeds up the arrow, raising the POI slightly. For hunting the difference is minimal, from a tinkerer's perspective the change is monumental.
A good string will stop creeping eventually, I haven't adjusted my Boo string in over a year, daily use too.
For eliminating stretch there is no substitution for shooting it in to place, a close second would be leaving it cocked over night.
I put the same care and caution in to my crossbow for accuracy as a bench shooter does his rifle, just another hobby that is fun to take serious.

Image

Dave1 wrote:I am curious about this brace height thing. If a new string stretches and the brace height changes slightly, does that increase or decrease the poundage and change the arrow speed and/or point of impact?

How much variation in bow poundage, arrow speed, and point of impact can brace height change have?

Is brace height change something the owner/shooter should watch for closely, adjust by twisting the string when any change is noticed, and try to keep at precisely the same place?

Is there a standard procedure so to speak such as wait a week or shoot xx number of times then adjust brace height for new bows or string replacements for checking/setting and maintaining brace height?

Dave
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Postby vixenmaster » Mon Aug 03, 2009 7:57 am

Pydpiper seems to have covered the bases. i have several FFF strings for 4 yrs now & they haven't stopped stretching!
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Postby Dave1 » Mon Aug 03, 2009 8:38 am

"i have several FFF strings for 4 yrs now & they haven't stopped stretching!"

That sounds scary. Wouldn't it eventually weaken to the point of possibly breaking? Why would a string continue to stretch or not?

What are the advantages (or disadvantages) of a custom made xbow string?

BTW, what does fff stand for?

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Postby ManX » Mon Aug 03, 2009 8:46 am

Dave1 wrote:....BTW, what does fff stand for?
Dave

Flemish
Fast
Flight
flemish is the way to make the string without frame http://www.geocities.com/salampsio/flemish1.htm,
fast flight is the type of material Image
hope to be useful :wink:
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Postby Pydpiper » Mon Aug 03, 2009 9:00 am

Dave1 wrote:"i have several FFF strings for 4 yrs now & they haven't stopped stretching!"

That sounds scary. Wouldn't it eventually weaken to the point of possibly breaking? Why would a string continue to stretch or not?

What are the advantages (or disadvantages) of a custom made xbow string?

BTW, what does fff stand for?

Dave



String stretch is a bit misunderstood, it is actually creeping. I am sure there is a bit of "stretch involved, but not much.
Creep is what happens when the wax and air voids slowly get worked out from between the strands and fibers, as a string creeps it is just getting tighter, thus longer. Eventually all the wax will be forced from the string and abrasion/breakdown will happen, otherwise known as simple wear. That's why the guys who know and understand strings (like Boo) will stress the importance of wax and it's proper application.
It's not like a rubber band that gets weaker as the pressure is applied, it is more like a rope that is allowing the strands to get closer, the end result is the same, the appearance of stretch.
Dacron can and will stretch, but isn't as common as it once was, today's strings have less creep.
A custom string is a handmade string taking all the variables in to consideration that a machine can't do. Custom strings are prestretched, eliminating most creep, servings are tighter and last significantly longer (often offsetting the extra cost of custom alone). Lots more too, I shoot them far better than I understand them though. :D
Fast flight is a string material, Flemish is the way the end loops are prepared, FFF is the combination of the two.

Have a read here Dave:
http://www.excaliburcrossbow.com/phpBB2 ... gs+strings
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Postby Dave1 » Mon Aug 03, 2009 9:21 am

Good information and photos, great explanations.

I now know enough to be dangerous. :-)

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Postby vixenmaster » Mon Aug 03, 2009 10:01 am

good info going here, my strings just creep along over the yrs. i just wax them after couple hundred shots. when a strand does break i take that string off and dispose of it.
i have some Boo strings that i will start using when my 3 FFF strings bite the dust. i won't & haven't bought any cept the 4 i got when ordering my phoenix, 1st one early 05.
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Postby Big D » Mon Aug 03, 2009 11:04 am

Most state 1 1/8. Do most of you measure the string from the side towards the scope or the other? The string has some width thats why I ask. I see doemaster measures on the side of string closes to the scope. Thanks for your help.
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Postby vixenmaster » Mon Aug 03, 2009 2:10 pm

i measure mine from riser joint to center of string. sometimes its not going to fall on the 1 1/8" because of string twist up. so if its 1 3/16 or 1 1/4 then its all good
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Postby Boo » Mon Aug 03, 2009 2:36 pm

Creep in the permanent elongation of an object. David you are correct in your description about strings creeping but there is creep of string material itself. Dacron is a good example of lots of creep and Fast Flight or Dynaflight (same formulation) have low creep. Then there is 452X or Excel(both the same formulation) which all exhibit even less creep. Do not confuse creep with elasticity which is the temporary elongation like an elastic band. Both elasticity and stretch can both be used in your favor but can also be a bugaboo.
Personally I used to keep my strings one or two string widths below the highest mark but nowadays I keep it a bit lower to accommodate my STS with the rods cut down to allow the bumpers to be supported by the STS. I found that the bumpers last longer if they are supported by the rods as well as the base of the rubber bumpers. With the STS, I can no longer see a difference in shock no mater where the brace height is.
The one piece of advice I can give you is to mark the side of the rail where your string sits so you can have an immediate and precise way of seeing your preferred brace height.
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brace height adjustment

Postby cholafxsti » Tue Aug 04, 2009 9:03 pm

Guys.. I must adjust string to the 1.125 measurment but am I right that I have to twist string? Any thing I should know about that? i.e. which way to twist? Just ordered the stringer aid! NOWAY could I get string off like the dude in the video. He must do that for a living..ha ha
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Postby Cossack » Tue Aug 04, 2009 11:30 pm

Personally I twist in the direction that the serving is wrapped i.e. tighten the serving rater than unwind it.
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Postby ManX » Wed Aug 05, 2009 2:55 am

Cossack wrote:Personally I twist in the direction that the serving is wrapped i.e. tighten the serving rater than unwind it.

all right
specially a FLEMISH string, serving-loops and twists must follow the same direction :wink:
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Postby awshucks » Thu Aug 06, 2009 2:04 pm

Dave1 wrote:I am curious about this brace height thing. If a new string stretches and the brace height changes slightly, does that increase or decrease the poundage and change the arrow speed and/or point of impact?

How much variation in bow poundage, arrow speed, and point of impact can brace height change have?

Is brace height change something the owner/shooter should watch for closely, adjust by twisting the string when any change is noticed, and try to keep at precisely the same place?

Is there a standard procedure so to speak such as wait a week or shoot xx number of times then adjust brace height for new bows or string replacements for checking/setting and maintaining brace height?

Dave


Just pick one you like and keep it set that way. Too many variables involved to be more specific.

When your bheight changes, your poi changes too, just enough to be irritating, imho.

Before I started shooting Boo strings [come pre-stretched] I shot FFF which took a long time to 'settle' in. You can speed the process up by leaving the bow cocked overnight a time or two.
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