Reducing draw weight

[alaninoz]

I need to take about 4# off one of my longbows (glass and bamboo) and I read here that this can be done by trapping the back of the bow, so I though I give that a go. It does raise two questions though:

1) what do you use to remove the edges? File, and if so what sort, sandpaper, something else?

2) what do you use to hold the bow while you are working on it? Bench vice, something else?

This will be my first time doing any major work on a bow so any help or advice will be greatly appreciated.

Alan

[KenH]

I've used a "palm sander" with a couple different grits of paper for stock removal, and a bench vice to hold the bow while I work.      A sander is less "aggressive" at removing stock, and going slow is IMHO better.

[Crooked Stic]

Most times for me a aggressive corner rounding can get 3-4 lbs. off. I do it with a spindle sander at 45 degrees and a little flatter towards the glass. You got to keep it moving so not to gouge.

[Flem]

I'm not as brave as these guy's. Once I get past the rough shaping stage, I switch to hand tools. Just don't trust myself with aggressive, small contact area tools for fine work. That and I like to get a long stroke on my limbs
This is my final sanding arrangement. It's convoluted, but it works well for me.

[monterey]

 I have used a palm sander but the last time was "the last time".  The paper tore and in an instant made a mess of the glass.   

This is my final sanding arrangement. It's convoluted, but it works well for me.

   

[kennym]

I have a quick jig for my disc sander, you better be careful tho!!

And if you use sandpaper in hand, be sure to sand only toward limb tips. Glass has grain in it like wood, you can catch an edge of paper under a sliver and really make a big sliver of glass pull loose.

Don't even ask...

[Stagmitis]

1) Round corners first then Flat sand both back and belly.......

Safest way to keep string alignment.

2) Trap the Belly-

I dont like trapping the back on my Hill bows because thats what holds backset-Too much belly trap though and you lose performance- Ive used both power tools and hand sanding-Either way the same angle and ammount of material needs to be removed or your alighment will get off. Sometimes Ill use a micrometer set to the width I need and use it to scribe the side of the limb then block sand.

I am assuming you have already final sanded?

[Shredd]

It is kinda important to know how your bow is bending...  At brace and at full draw... Also what is the width at the fade area and at the nock area???  Post some pics and some bowyers might have some advice as where to remove stock from your limbs...  Removing stock in the right place could actually improve performance and in the wrong place decrease performance...

   For example if you remove 1/16" from the whole limb it will make the first 3rd of the limb more stiff and the last 3rd near the tips less stiff...

[alaninoz]

Thanks folks - lots of stuff to think about there. I like the idea of the disk sander and the spindle sander, but given my level of skill the palm sander or hand sanding might be a better idea.

Shredd: Your point about removing 1/16" having a different effect depending on where it's taken from is something I hadn't though of. Thanks.

[Crooked Stic]

   For example if you remove 1/16" from the whole limb it will make the first 3rd of the limb more stiff and the last 3rd near the tips less stiff...
[/quote]

Expplain this Shredd

[Mad Max]

   For example if you remove 1/16" from the whole limb it will make the first 3rd of the limb more stiff and the last 3rd near the tips less stiff...
[/quote] Not true Shreddy

Binghams Bow Draw weight chart shows that going from 2" to 1-3/4" wide is approximately 5# less for the same stack.

[Shredd]

Haven't you guys noticed that if you equally reduce the width of the whole limb that it changes the way the limb bends and effects performance??   

   Lets say your limb is 1 1/2" at the butt and 1/2" at the tips...  That equals to 24/16" at the butt and 8/16" at the tip...  If you remove 1/16" from the butt you are only removing a small fraction of material, 1/24 of the total butt width...  If you remove 1/16 off the tip you are removing a lot more material at 1/8 of the tip...

   Lets use a bigger number so it it is more easy to see and definitely effecting the limbs bending properties... 

      Take 1/4" off the butt and you still have 1 1/4" left, reducing its strength by 1/6...  Take 1/4" off the tips and you reduced the tips strength by half...

When some guys reduce the draw weight in a limb to get better performance it may not be the loss of weight that is giving them the better performance but the change in the bending of the limb...   Or Visa versa...  Lose performance...  Or break even by gaining performance by losing weight and losing performance by less than optimal bend...

   It goes deep my friends...

[Crooked Stic]

Most guys are not going to 1/16  off the whole bow and make it more narrow. T may 1/6 th at the tips and draw a line to the fades and hardly nothing off at the fades. For sure you are gonna go to the fades on a TD. 

[Shredd]

So....  What's your point??   You can take stock off wherever you want...

 I was just bringing up the point that depending where you take it off could change how a bow shoots...  And just because you make the whole limb consistently thinner does not mean the bow is gonna shoot the same...  You can use this to your knowledge to fine tune a bow...

  In what you said of taking 1/16" off the tips and next to none off the butt will definitely make the last third near the tips bend more...  That is good if you want the the area near the tips to bend more...  If you don't then you are shooting yourself in the foot... 

Stic...  When you shoot yourself in the foot, do you prefer a 22 or a 44??       

[Crooked Stic]

Well that would hurt to shoot my foot.  :scared:And if I wanted a lot of weight off the original question I would sand the glass. then round the corners. If you got to narrow the limb you need to start over with a smaller stack.

[Crooked Stic]

A bow with a cracked riser could not hurt really bad   

[monterey]

Well, Shredd, I get it and have used the principal to change limb behavior and to correct my mistakes.  There's a limit but the principle is undeniable.

[Shredd]

  Glad someone gets it...   

 When in doubt or making a new design leave the last third a little stiff...  It is easier to take down to get the right shape plus lose a little weight from the where it matters most...  Better to be fat and narrow than thin and wide...  Unless you need some kind of torsional stability...