How thick is a glue joint between laminations?

Hi Y'all,

I was gluing up some teak blanks the other day and I got to wondering just how thick the glue joint is between lams. So I did a little test. I was gluing up a blank with 4 vertical lams so I thought I'd just measure the overall thickness before and after the glue up, then divide the difference by the number of glue joints.

I clamped the lams with 2 squeeze bar clamps about 6" apart and measured 1.622" with the lams dry. Then I proceeded with the glue up. After the glue was dry, I measured 1.640", for a difference of .018" for the 3 glue joints, or .006" for each joint.

Admittedly, the scientific protocol wasn't all that great. I can't really say that the pressure generated by the clamps is equal to that generated by my glue up device since I couldn't figure out an easy way to measure it, or calculate it. I'm not sure it really matters, anyway, other than the thinner the better, based on a breaking test I did on some glued up lams awhile back. That test showed a planed joint between lams was much stronger than leaving the sawmarks in the wood, resulting in a thicker glue joint.

I was just wondering if anyone else has tried to check the thickness of the glue joints on their blanks. It might be kind of interesting to compare notes.

Bill

I know some guys use filler to fill the space better. That's what got me wondering how thick the space really was. I'm not going to worry too much about not filling the space if it's only .006".

I was discussing whether or not carbon fibers actually strengthened the joint awhile ago with Jeff. I actually got some carbon fiber cloth and worked out a little test where I would bulid a blank with and without the fiber using the same piece of wood and the same dimensions, then measure the deflection with a known weiight hanging from them. With the price of teak, I would probably use pine since it would probably be fine for a relative comparison. I just never got around to doing it.

I would think that they would have very good consistency since they would be set up to do the same thing the same way over and over. That said, iconsistent doesn't mean better. Mistakes are also reproduced over and over until they are recognized- recalls on cars, for example. I think the biggest advantage of "one off" anything is that the design and construction are constantly being "tweaked" to improve. Look at Grizwald and Tin Man. I'm not sure if they have built two of anything they've built. They are always trying to do the next one a little different to improve it- usually with success!