weight reduction

[tat2dgrizz]

Hey guys, I'm new to the forum and have a problem that I hope someone can help shed some light on. I have a glass backed longbow that I would guess is in the 70-75# range(have not put it on the scale yet). How can I reduce the weight of this bow? Sand the belly? Sand the back? Both? Radius the glass on the limbs? Any suggestions would be helpful and appreciated. Thanks, T2G

[talkingcabbage]

The best way would be to take a scraper to the wood on the belly.  Take off 10 strokes off each limb and check the tiller and weight after each adjustment.  When you get close to your target weight, stop and use sandpaper to smooth everything out.  More than likely, if you stop within 5# of your target weight, you'll come real close after shooting in.  

You definately don't want to do much more than a super light sanding to the glass.  

What kind of weight were you wanting?  And do you have any pics?

Joe

[tat2dgrizz]

I'm sorry, should have given more info. This is a laminated bow that I just built. Maple and Purpleheart lams with .050 glass on the back and belly. I'm kinda new to building lam bows but my research indicated that I need .389 at the fadeouts for a 50-55# draw weight. My finished thickness is .383 and the draw weight is WAAAAY too heavy. I am guessing 70-75# @ 28". If I could get it down to the mid 60's I would be happy. Talk about MISSING your draw weight....oh well live and learn. Can anyone point me in the right direction?

[Asafan]

What width the bow at fadeouts has?

[tat2dgrizz]

The bow is 11/2" at the fadeouts and 3/8" at the tip. 66" tip to tip.

[Pat B]

It will probably be difficult to get 20# off of the bow. You could reduce the width quite a bit and that will help. I don't build glass bows so this is just a guess. You might be better off trying to sell it at the weight it is and make another. You can probably get a recipe from someone here on TG that will put you where you want to be weight wise.   Pat

[tat2dgrizz]

Thanks for the help everyone, I was able to get it down to 66# @ 28" by narrowing the limbs. As I am getting older, it is still too heavy for me to hunt with so I will probably give it to my son to use(he is a brute). Does anyone have a chart or recipe as Pat stated above to use as a guideline? Once again thank you all for your reponses.
T2G

[kennym]

Here is a pretty good chart,I use it for reference....
   http://www.binghamprojects.com/drawweight.htm  

These 68" straight longbows have an 18" riser and .002" per inch taper. These are the butt thickness of the entire stack including glass at the thick end.

[Asafan]

Grinding of a glass on thickness with 0,04" up to 0,02" will reduce force for 10#, but this work demands skill. It is better make a package of correct thickness at once...

[John Scifres]

You should be able to narrow it to get to your weight. You could easily take 1/8" off each side I bet.  Or build another one.  That's fun too.

[sub-zero]

you could trap the limbs also

[Chuck Hoopes]

Ive reduced poundage in numerous glass bows by simply taking it off the sides w/ a file or palm sander.  If you count the stokes on both sides of the limb, top and bottom, you should not have a prob. keeping it in tiller-- at least this has always worked for me.  I reduced an old Howett Hunter from 70# to 55# 2yrs ago.  This is a bow I shoot daily-- no probs. it's never been sweeter. I have done this with at least 1/2 doz. bows of mine over the yrs.  As I recall the total amt I took off the width of the Hunter was about 3/16".  I have a glass longbow (Hamilton) that's 62# @26"- Iam going to go at this one the same way- until I get something like 55#@28".

[tat2dgrizz]

Here she is guys
Maple, Purpleheart and 0.50 black glass limbs
Bocote, Pupleheart, Cocobolo riser with white accent stripe
Burgundy and black linen micarta tip overlays
66"
66# @ 28"
 
 
 

[tat2dgrizz]

Sorry about the pic size and quality, never was a photographer!!!

[Holm-Made]

No reason at all you can't flat sand the glass starting with 100-150 grit and working to 220. You are using .050 glass so you have plenty of fiber there to work with.  Don't worry about counting the strokes when sanding, just keep an eye on the tiller as you go.  If you haven't flat sanded the glass then you can get another 4-5 pounds off it.  
Round the edges over good will take a pound or two off as well.  1 1/4" at the fades is wide enough as well.  Chad

[Holm-Made]

Also it doesn't look like the lams have any taper in them.  Are they all parallel?  If they are then that is probably why the bow came out so heavy.  The formula probably called for some taper in the limbs which would have reduced the poundage a lot.  
Pretty riser by the way and nice leather work.  Chad

[tat2dgrizz]

Thanks for the input Chad. The lams do have a slight taper but not .002 per inch. I tapered them the best that I could on my surface sander and still keep them uniform.

[tat2dgrizz]

This has probably been discussed a million times but for those of you who make your own tapered lams what type of fixture or jig do you use? Any prints on how to build something like this? I have tried a search but to no avail. Thanks,
T2G