Lam thickness

[Big Stew]

I plan on building  a 66" R/D LB , 42 @ 28 ( I will be drawing 30.5) . Riser will be 18", 050 glass. I think 4 pr 065 tapers should be in the ballpark. I haven't  made any for 15 years and can't find my size chart. Any thoughts?

[kennym]

On my form, .360 with .003 taper,18" riser, and .040 glass would be about 40#,  so depending on the taper rate , amount of D/R and width, you should be pretty good. The .050 glass will add a bit, some say up to 10# but I haven't used it in my design.

Let us know!  

[Big Stew]

Thanks Kenny. My bows are 1.28 at fade outs and .56 at tip overlays. Some of them end up 67" instead of  66".

[Big Stew]

Kenny I forgot to mention taper rate of .001.

[kennym]

With .004 total I bet you will be close.

[Big Stew]

Any problem using  15 year old lams and glass if they are cleaned well with acetone? I think they are dry by now!

[kennym]

I would probably scuff the wood lams with a sanding block and blow off. Glass should be good with a bit of cleaning IMO...

[bamboo]

won't hurt to lightly sand the glass to freshen it [by hand with a block] then brush clean

[Big Stew]

Thanks Bamboo! I didn't have 065 lams so I going to use 2 pairs 075's and 2 pairs 060's . Acording to Binghams weight chart it should be right on.

[kennym]

Does Binghams use .004 total taper now? They used to be all .002 total except the TD longbow...

[Crooked Stic]

You can clean the glass with acetone. But not the wood. Maybe scratch the wood with a hacksaw blade and blow clean.

[Big Stew]

Lams were from OMC and 002 taper

[Robertfishes]

Stew, are you saying the 075s and 060s are 002/inch tapered? That would give you 008/inch total taper. You have any parallels? Even if you reverse 2 pair of your tapers you will need parallels to make the .370 stack height.

[Big Stew]

Robertfishes what size parallels do you think I need? I called Binghams and they said they never send out all tapers with their design. I have my first bow I made from them and the lams are all tapers. I am really confused now!

[Robertfishes]

Big Stew, I'm not feeling good tonight but I'll try to work thru this... Since I dont know what your D/R design is...I don't know what your Total stack height should be..But I'm sure it can be worked out here on TG since there  are a lot of guys here with good experiance..So are you using a Binghams design? if so which one? do you have a good dial or digital caliper for measuring lamination thicknesses? It's possible Binghams reverses half of their tapers to make stack "parallel"..

[Robertfishes]

Stew, the only longbow I build is the original 62/64 KennyM design from 2010, but I have built more 66" bows off of my form so I can give you stack heights for that build only..I usually have a limb width of 1.45" at fades. Kennys awesome design uses a total taper of .003/inch so I use one 002/inch taper and one 001/inch taper for a total taper of 003/inch..I use a parallel or parallels as needed to make stack height.

[Robertfishes]

Stew, I am looking at my build log now.. 66" D/R. Riser 18.5",amberboo lams, 24" 030 Powerlam, 002 taper .116, 001 taper.070, parallel 0.048, two .028 zebrawood veneers, two .040 clear glass..total stack 0.370, I do not include the power lam in the stack height. 1.40 wide at end of riser fade, tip 0.60 wide at string groove. 46# @ 28"

[Big Stew]

Thanks Robert, hope you are feeling better. My form is the 68" longbow from Bingham. I just went and bought another caliper and it is as all over the place as the other one! I think it will be easier calling OMC and ordering new lams and glue.

[Robertfishes]

There is a stack height chart on the Binghams web site. I have a Igaging absolute zero digital caliper that is pretty good.. But I wanted something better.. I bought 2 used dial calipers..both are Japanese made Mitutoyo's and both check out perfect using known standards. I check them every time I use them.

[Big Stew]

Robertfishes I got an Igaging digital, what a difference!  4 pairs of .075 @ 001 should be .364 with .050 glass subtracting 9 inches for 18" riser. That should be right on for 42 lbs @ 28". Thanks