Lam questions

[JSMOFFITT03]

I have a few questions regarding lam thickness calculations.  the Obvious answer is you add up the total deminsions to get your total stack... but in my readings I see a few different locations/directions to measure the total lam thickness.  

First question:

Some say measure at the butt thickness of the lams(thickest section if tapered)all stacked prior to glue up.

Others say measure at the riser limb juction after glue up.

I have even seen measure 1" past the riser on the limb after glue up

My guess for accuracy you would need to measure the butt of the lam.  that way it would be at the same point all the time. Is that right?

Also everything  that is stacked to make a laminated bow should be included in the total stack deminsion correct?  that would be all wood lams,glass, etc .....

The next question is how thin is to thin for a wood lamination?  my guess would be there isnt a "too thin" as long as its backed with glass....

Thanks in advance, just need some clarity

[Glunt]

I'm no expert but I don't think where you measure matters as long as you stay consistent.  I use butt thickness because its easy and thats how I order them.  You have to keep track of taper rate, limb length, limb width, & riser length to get a feel for how to hit certain weights.

I use total stack including glass to keep track.

I just built a new form  with a new shape and my 60# recipe came out at 75#+

Thin is fine for lams but you can split real thin lams. I haven't messed with anything under .030 and haven't had an issue.  Folks do go thinner especially when going over carbon that they are trying to keep close to the outside of the stack.

[Bowjunkie]

Yes, myself and the guys I know that build laminated bows, and all of the suppliers I've ever bought from, measure the butt ends of the lams.

Yes, measure all lams, including glass.

Too thin? Heck, you can use very thin veneers for a certain look under clear glass.

With tapered lams, they can get 'too thin' because you eventually run out of wood on the thin end.

[Bradford]

So I measure at the butt when building.. but measure at the end of the fade of the wedge when built.  So the where the wedge fades away and is no more, I measure about 1/4" above that.  It seams to be an accurate spot for me.. plus this is where the bow is working (bending).

paper thin works... heck, you can use paper!  I made some veneers once, and if you held them up to the light, you could see right thru them.

good luck

[kennym]

I measure at butt when making lams, so I don't have to measure a different distance on each set due to diff riser or wedge lengths.

If you need to measure a bow already glued up, you can go out past wedge or fade on riser, then calculate the butt thickness(after determining taper rate)

[Dick in Seattle]

My "system" is to measure at the butt when grinding, like Kenny, but I (mostly) use only one thickness of glass, .040.   I keep a record of every bow built with careful notation of "Wood Stack", separate from glass and/or power lam.   Obviously, in those few instances where I got a wild hair and used thicker or thinner glass, I note that as well, but for the most part, when I start a bow, I go through "The Book" (no, not that Book) and check all the previous bows close to the weight I want.  Then I check what woods I used, the wood can make a heck of a difference in finished weight.

Good luck!

[JSMOFFITT03]

Thanks guys... As always great info

Cleared it up nicely!!!