Mollegabet Layout

[Jackpineboyz]

So I've been playing with the molle designs for a year and am getting them to work pretty well.  I had a 40 # red elm at 29" I hunted with this year.  Unfortunately it splintered mid limb on my bottom limb while I was shooting it in a couple weeks ago.  I am pretty sure it was due to moisture, looking back my house was only around 30-32 relative humidity which placed the bow around 4-5% i'm guessing.  It spent countless hours strung and hunting hard this fall in all weather conditions with no set.  I had a good 200-300 arrows through it without any concerns previously. The belly was heat treated, unbacked.
So while I started laying out my next molly, I thought I'd get feedback on my proportions, and have a proportioning question that I'm hoping someone like half eye could enlighten me on.
First my question that got me posting.  I typically design a "safe" self bow with limb length = 2 x draw, plus 1" for nocks + nonworking handle if used (usually 6 or 8"). With a lever bow I have never seen a real rule.  Since we are increasing the strain on the working limb by forming nonworking levers, what should the proportions really be?  Do you follow the same rule and just go wider?  Or do the improved string angles from the levers allow more string and to work and amplify the limb motion enough to offset this difference.  I have been adding an extra 0.5 to the width compared to an AFB (hickory I went from 1.75-2.25")  I do put a very slight taper on my limbs as they narrow to the outer fades.
As an example, my red elm dimensions were
69 ttt, 68 ntn, 4" handle, 2" inner fades, 17" working limb, 1.5" outter fade, 11.5" lever.  Limb width was 2.25" inner fade with gradual taper to 1.75" at outter fade.  ( this was my first red elm bow.) This would be a 57:43 ratio.
For this next bow I am using hickory which I will heat treat.  I would like to do a 3" handle with 1.5 " fades.  By shortening my Handle from 8" to 6" can I shorten my overall length 2", or does this also effect the string angle and stress on molly limbs. I am ok with 68" ntn, but really like the 66" I hunt with so was hoping to save the length.  My goal for the hickory is 55-60# with the 29" draw for elk season in WY next year.  For the weight and my 29 " draw (30" with proper form) I think going 68" might be more durable.
Thank you for your thoughts.  I saw a few of Half eye's posts with some of this in them, but the pics were deleted.

[willie]

a rule of thumb when comparing widths and poundage is to use density as a guide. If you can actually compare the two staves,
(or a sample from the broken bow to the stave at hand) it might be better than looking in a book to see what the different species are supposed to be. see baker in TBB 4 density rule of thumb p. 114-115.

As for shortening the new bow, could you make the the working limb a bit longer to make up for the extra strain?

[Jackpineboyz]

Thanks Willie.
I have the TBB 4 pages you mentioned dog eared.  I was following this as a guide, and my plan since this is meant for elk hunting is to add the extra inch of handle into the working limb I think.  Dependability is more important than size for this one.  Also, I will have six months at least of shooting it for a better break in.  The elm bow wasn't shot much because it was the only hunting grade selfbow I had and finished it in October.  I am just using my glass bows for practice and form.  After the elm blew I just couldn't bring myself to take my glass r/d bow out.
I think I'll actually test my specific gravity on this hickory as well to guide my weight.    It's nice to have someone share my thought process.

Part of my post was conceptual on how the handle length/etc played into a lever bow rather than a flatbow or ELB which has a lot of literature on string angles, cross section, work load distribution, etc.
A 30" limb on an AFB will fit a 30 " draw generally with 6-8 stiff tips which is 24-26" working limb.  A 60/40 molly at 30 " has an 18" working limb.  Is it width or levers that allow this to function?  If it is levers allowing this, would reducing my handle length or allowing a slightly working handle allow shortening of the bow? 


I'm getting comfortable with the design and even pushing its limits, but sometimes I think my brain gets in the way.

[bubby]

I always make my handles 4", 3" grip puts the fades in the way with my big mitts.  I like a 60/40 ration on mine plus I usually recurve the levers. I have built 60" not @29" draw with this design no problem with a stiff handle. If you want to shorten your bow just build it with a slightly bending handle

[Jackpineboyz]

Bubby,
29" on 60" NTN is impressive.  Backing?, Elm?  I might just be chicken, but my pucker meeting is already firing with a 68" and those short limbs.  Would love to see a picture if you have one to share.
I have a good size hand also, but spent a little time with Arnie Moe and have most of my hand off the handle, so I figured if I'm not using it, might as well get rid of it. 

My handle isn't cut in from the fades yet, so I think I'll take your advice and work in a bulbous handle with a bit of motion in it. 
Maybe something ishi-ish.  I've been reading on some of his history and could see this making the stress less abrupt on the working limbs form the fades.

[Springbuck]

So, not to be too nit-picky, but this helped me understand this idea better.

 "Since we are increasing the strain on the working limb by forming nonworking levers, what should the...................?"

  This design COULD increase the strain on the working limb, but it doesn't HAVE to.  We ARE definitely asking the bending portion of the limbs to bend MORE, to a tighter arc, etc.  but the whole genius of the design is that we can do things, like widen the limb, to ensure that the inner limb isn't overstrained, and we can do that at at no cost (or very little) to tip weight.  Wider limbs are heavier, but the extra weight doesn't cost you nearly what it would in the outer third of the limbs.  I also believe that the stiff portion of the limbs adds stability, creating a very crisp but dampened string drop as the arrow leaves.

I haven't had success like Bubby has, but I like the 60/40 ratio, too.  I have made a 66" 56 lbs Mollie, good elm, < 5" diameter sapling, 2.5" + wide inner limbs, short stiff handle, an inch of reflex at the levers, heat treated belly, that took ZERO set at over 29" of draw.

[Jackpineboyz]

sprinbuck,
thanks for the feedback, I'm out of elm, but have a hickory starting to floor tiller with your same specs.  I have some elm I need to cut for the future, but had a pile of hickory.  I like a 66" for hunting.