Newbie- Need Lam Grinding Assistance to Hit Weight

[gables]

I recently built a bow grinding my own limbs for the first time. The bow came in at 22#'s when I was expecting at least 50#s. It is a 62" longbow with a 18", .30 center power lam (ibeam riser)and has 12" reversed tapers at the tips. I laminated one parallel lam of ipe at .157 butt thickness on the back and a tapered lam, .002, at .157 thickness on the belly. Sandwiched between the two lams was a .030 lam of uniweft glass set in front of the riser.

On my next try I want to keep everything the same except use 5 laminations: four wood lams with a center core of the uniweft.

Any suggestions on a recipe that would get me closer to a 50-55# draw?

[Bradford]

I did the same thing.. I forgot to look at the length of the bow.. I was building a 56" bow and hit 38 lbs.. so when I built my next bow, I forgot to add in that I was building a 62" bow.  Check out binghams website for the thickness you need to get the pounds you need.  Usually you can still just use the two lams, but need to go thicker with the lams and a wider limb will help too.

[soopernate]

I am wondering why you put the fiberglass between the two lams...could you explain this to a newbie?

[jess stuart]

You could add another strip of glass to the back or belly.  I have done that a couple of times on a new design that came in way light.  It will add mass and you will lose some performance, but better than way light

[sw]

Depending on how long the bow is and design - a .050 glass backing might bring you up some pounds - BUT it depends on the length and design of the bow. A general rule is every .002 is good for 1#.

Honestly however - i'd just start over rather then adding to a light bow.

Try the same lams you did before but ADD a .250 thick by 18" long power lam between the .157 lams at DEAD center of the bow (tapered of course).

Add a barrel tapered bamboo backing that is 1/4" thick at the center and tapering to 1/8" at the tips

Add 4" of R/D at the tips with .050 butt thickness wedge tapers that are 8" long at the tips to stiffen them.

Back of the handle (center) add three layers of .300" by 18" long lams (for your handle).


The bow is actually listed in the bowyers bible i think Vol. 4.. I have built a ton of them and they work VERY wel, smooth and pretty easy to build. With a good thickness sander the lams can be kicked out in under an hour with almost ZERO tillering at the end....

The two bows below are cherry/osage and cherry/walnut.. both came out in the 45 to 55# range and where very stable, smooth and fast. I say 'was" as both sold very fast. The walnut bow you can see the backing - power lam - para lam, tapered lam and then the three handle pieces pretty clear.

 

 

[gables]

Thanks for the input. Seigeworks, I constructed the bow close to your description. I was hoping for 50#, 62" with the lam bundle I described. I like the look of an all-wood bow but do not yet want to use bamboo backing. My draw is 31" and I have been told a few times I would need a longer bow than 62" to not compromise a bamboo backing. I did use a center power lam and reverse tapers at the tips. The center strip of glass is for durability and stability as described in Byron Ferguson's book.

If I were to follow my same process for building but went to 4 lams of wood with a center core of .030 glass then for a 62", 55# bow I figure I need a bundle of .41. Does that sound right?