Missed weight

[jsweka]

I started a bow this weekend that is going to be for a friend of mine from work.  I used the following recipe:

0.040 clear glass
0.090 walnut parallel
0.090 actionboo parallel
0.090 actionboo parallel
0.110 walnut 0.002 taper
0.040 clear glass
16" riser

This bow is the same exact design as the Hill style I did the build along here back in December except that bow had all acitonboo lams and it ended up at 54# @28" when it was all finished (58# when I first put the sting on it).  The current bow was 66# @28" when I first got a string on it.  Assuming it would lose 3 - 5# by the time I rounded over the edges of the limbs and final sanding, that still puts me at about 61 - 63#.  I narrowed the limbs a bit (currently 1 5/32" wide) and got it down to 62# and I don't want to go any narrower.

I wanted this bow to end up a couple lbs lighter than the one I did in the build along and walnut generally makes a lighter bow than other woods with the same stack, so I figured by going with the same stack I would hit weight without any problems.  I was wrong.  

I'll finish this one out, but I'm thinking it will be more than what my friend will be able to shoot comfortably.  I guess there's really no downside - The bow will be a nice weight for me, the walnut lams from Kenny are AWESOME, and I got an excuse to build another bow        

The only thing I can think is that the one I did the build along for had all laminations on the back of the riser and only the belly glass running up the fades.  This one has a tapered walnut lam running up the fades under the glass.  Could this be the difference why it came in heavy?  Have any of you had similar experiences with/without lams on the belly side of the fade outs?    

[heartlandbowyer]

Glass only on the belly may have something to do with it but maybe the walnut and bamboo work differently against each other than all boo. Maybe some of the experts will have better thought on that.

You could always trap the back 1/8  and see where your at lb wise.

You probably need another bow just as bad as I do    
Good luck either way.

Cory

[kennym]

I remember those walnuts, you sure you aren't just wantin another bow?    

You should be able to lose 3-4# by trapping like Cory said..

[kennym]

Ah,

Looked back at weights, don't think that is gonna happen without any more edge to sand.

[jsweka]

Yeah, I thought about trapping the back, but I'm still not sure if it would get down to where I want it - 50#.  

You're right, I really don't need another bow, but the walnut from Kenny is just so nice.....  

[heartlandbowyer]

Yeah that's pretty narrow huh,  other though since you added the walnut taper to the belly would that change compression values versus the previous bow?

Come on experts chime in I would like to hear your thought on this.

[jsweka]

What I'm thinking is that the walnut coming down the belly of the fades is basically making the fades stronger and decreasing the working length of the limb and thus a higher draw weight. At least that's my theory.  

I double checked the thickness of the two bows at the ends of the fades and they are exactly the same (I didn't screw up by grabbing a 0.050 piece of glass from my stash).  I'd like to see if anyone else has experimented with bows that have a belly lam vs. those that don't and how they compare.

[MoeM]

1 5/32" man sometimes Ireally love the metric system^^
I would not mind to narrow it a little more, I`ve recently seen a Hillstyle 2,2cm wide (keep in mind 1" is 2,54cm)
The usual trapped belly won`t bring really weight decrease I guess- so narrowing shall be best way...

[kennym]

Don't know about making the fades stronger, but that is very interesting. I figured it was a composite when glued up?

So a bow with all lams on belly of riser should make same weight with less thickness...

Hmmmmmm.....

Might be a way to tweak more speed, lighter limb with same draw weight.

So who's gonna test this?   :D  

I did have a bowyer tell me that his fastest bow to date had pretty thick jatoba lams on belly. Said it was a screamer.

You may have something here.....  

[Millhimes]

I feel your pain john,same thing happened to me at the doctors last week,only i came in 25# over the target weight  
Does the original bend into the fades deeper?

[jsweka]

I just toook a couple pics to compare the strung profiles of both bows.  Top one is the bow without a belly lam - just glass running up the fades.  The bottom one is the bow in progress that I missed weight on.  It's the same string on both to eliminate that variable.  I don't notice any difference in their strung profiles, so my theory of a stronger fade is busted.

 

[east_tx_pineknot]

Trace each bow on the same sheet of paper and see if there is a difference.

[jsweka]

Yup - Was gonna do that tomorrow night.  Thought I'd do the quick picture thing to see if anything really jumped out as being different between the two.

[bigbob2]

John,  all my HH style  flat laid bows are 1 1/8'' wide at the fades tapering to 1/2'' at the string groove so you still have a little you could play with.I also put one lam up the belly on all my bows so don't have a reference versus one with only glass on the belly. My only thought is that the walnut is an anomaly and added to the weight. Wood is dynamic and each piece is a little different. Thats why I like the 'boo for its consistency.

[jsweka]

So I traced both bows tonight on a piece of paper.  I made marks on the paper where I lined up the tips of the fadeouts of each bow to make sure each was in the same spot on the paper.  The bow without the belly lam did bend slightly more into the fadeouts, but hardly noticeable.  By the time I traced out to the limb tips the tracings were less than 1/4" appart.  

I'm stumped.        But it will still make a nice bow.  Just heavier than what its intended owner can shoot comfortably.  I guess I'm just gonna have to build another    

[Roy from Pa]

Just drill some 1/4 inch holes in the limbs equally spaced. That will reduce the weight and make it 10% faster cause the air will pass through the holes and cause less wind drag on the limbs.

[talkingcabbage]

Lol Roy.

[monterey]

I just toook a couple pics to compare the strung profiles of both bows.

This just about must be photo related or perspective related, but the second bow in the pic looks to have just a bit longer riser.

[jsweka]

Roy - How about you try that on one of them whittled sticks of yours first and if it works out for ya I'll give it a try.

Monterey - Maybe it is the pic.  I did have to fool around resizing them to try to make them match.  The risers are the same length.  That was one of the first things I compared between the too.

After rounding the edges of the limbs over, I've got it down to 58#.  Too much for its intended owner, but good for me.  My wife thinks I screwed it up on purpose.

[jess stuart]

I used to use vertical aboo flooring for lams.  After Lumber Liquidators stopped carrying it I went back to good old maple.  First bow with maple lams about 10# heavy, thought I had made a mistake but the calipers said everything was the same thickness.  Have adjusted on every bow since and they all required a reduction in stack in order to not be to heavy.  My limited experience has lead me to believe that aboo will make a lighter limb with the same stack compared to maple.  
Not saying it makes a inferior limb just lighter at the same stack height.