Lam Stack

[Wolftrail]

I have the Binghams stack calculator sheet, but what I'm building is different, the bow will be 66" NTN and 1 3/8" in the fades, using mostly maple. Two lams with a 1/8" 34" taper in the core and 3/16" for the belly and back lams. I will taper somewhat both those to get the reflex in the tip ends.
Is this combo ok or should I use something else. What glass thickness would be good for the belly and back. The maple lams are all 1 1/2" wide.

[Robertfishes]

3/16" laminations = 0.1875" thick, that is pretty thick for a glass bow. You will have a hard time getting wood that thick to bend up the riser ramp. I use 0.070" or thinner for my belly side tapers and no thicker than 0.120 for back side tapers. 0.040 glass for bows under 45#, 0.050 for longbows over 50# seems to work for me.

[Robertfishes]

If I read your post correctly, you are using a Taper rate of 0.0037/inch..Taper rate varies with design and I don't know about yours. I build the KennyM design 62/64" D/R longbow and use a 003/inch taper for that design.

[Wolftrail]

My stack would be about 0.3750 with the 2 lams. Taper is 0.0037/inch.. so what total stack you recommend including the 0.040x2 glass lams. Like I said the bow width would end up been  1 3/8" at the fades.
I'm coming up with 0.270 total for just the wood.  Does that sound right..?

[Robertfishes]

what style bow? straight limb Hill, mild d/r or heavy d/r hybrid? And what draw weight at 28"?

[Crooked Stic]

You cant go by Binghams unless you are building their design
 You have to build one on a new design just to see where you are. Take a swag then go a little less. Most times for me my first guess came out too heavy.  :confused:

[Wolftrail]

Thanks guys for the info.  I know I left out the important stuff.
It will be 66" NTN with slightly reflexed tips.  Longbow, draw 28" weight 42-44# .

[Robertfishes]

I agree with Crooked Stic, no way to know till you build one.. Can you post a picture of your form?

[Wolftrail]

I'm using an open form.  Not much to see there.

[mikkekeswick]

Without the shape of the bow nobody can help....

[Wolftrail]

Originally posted by mikkekeswick:
Without the shape of the bow nobody can help....    

Like I said basically flat bow with reflexed tips, dont get much more basic than that.  I think at 68" NTN a stack of .3750 should make over 45#.. I can always tweak the side taper.

[kennym]

Here is a WAG - no guarantees

Binghams strait 68" 45# = .375 with .002 taper

cut to 66"           = + 5#

narrow to 1 3/8"     = - 2#

reflex tips slightly = + 2#

.003 taper from .002 = - 2#

2 lams instead of 4  = - 2#

So 46# @ 28" (maybe)  :D  

You can trap 3-5# off if you don't mind the look on a more traditional bow.

Keep notes well and adjust the next one! Good luck!! Building new designs is a blast, but can be costly. I am starting an ILF longbow limb form today  , I'm in the same boat as you are!    

Disclaimer !!!  No guarantees!!!   :p

[Wolftrail]

Thanks for the break down on all possible combos you listed.

[kennym]

Those may be different on every bow style, but should be kinda close.  

[Wolftrail]

Experimenting is always fun and ya never learn much by building the same bow over and over again. My second wooden takedown was ok albeit some limb twist, it shoots very well but I learned from that and carried on.  The challenge is doing whether its a total failure or a success.  Like they say ya aint breaking ya aint building.!