lam thickness.. check my math

[Bradford]

Okay.. check me:

I am doing a take down recurve 65-70lbs @ 30" - 18" riser.. 19 degree limb pad.. 62" AMO (noc to noc).  According to binghams I am looking at a stack of .280 (or just a hair over 1/4") thick.

Does this sound right?

Just getting a few opinions.  Using hard rock maple as the core material.. clear glass on belly and black glass on back.

[Robertfishes]

I have only built one piece bows. are you building a Binghams bow? the information on their site will work for their design, I tweaked one of their bow designs just a little and the bow came out 10 lbs over draw weight for the stack listed on their site.

[Don Armstrong]

I think Binghams pads are 21 degrees. Will their stack work for 19 degree riser pads?

[Crooked Stic]

Everything thing else being the same including limb profile the 19 degree angle will make it heavy. By how much I aint sure. It does not thake much difference in a curve stack to change the outcome of draw weight.

[BrushWolf]

When I changed from 21 degrees to 19 it added about 5-6# to my bow.

[Bradford]

Thats the info I was looking for.  Yes, Binghams is at 21 degrees.  I am also adding in tip wedges and power lams.. so I will gain a little there also.

So sounds like I need to be around .250.. I will double check that.

Keep the ideas a coming if you have any.

So Binghams is a 18" riser but at 21 degrees.. I also changed the limb pattern a bit.. a little less curve at the fade area and more recurve in the tip area.

[BrushWolf]

Unless Bingham has changed something their riser for a 62" bow was 19". The first bow I made was with their plans but that has been a long time ago.

[Bradford]

Well I still have that part of the blue prints and measured it.  I will double check it tonight.

I re did all the calculations adding in for things and taking away for others and am coming up with a stack thickness of .270".

[strungstick]

It sounds like I have a pretty similar TD design.  What thickness of glass and what tapers are you using?  I use .040 glass and .001 tapers .270 should put you really close by my books, off the form maybe towards the upper end of your desired range but I'd rather go that route knowing I can reduce weight but it's pretty tough to add it.

[Bradford]

I hear ya... I am also using .040 glass and .001 tapers.

This guy is a beast with a bow anyway, so if I hit 72# he wouldnt mind.  But for the saftey of the bow I rather be in the 68# range.

Well, we will find out tomorrow.  I am going to be gluing up the limbs tomorrow.  I think I might shoot for .273 or .275.. and narrow the limb a bit if need be.

Thanks for the confirmation.. as long as I am close, should be good.  I will post when I get the numbers back.