Lamination help

[Alex1]

Hey I was wondering if somebody can tell me where I went wrong when I was laminating the wood to make my first gun. I bought a padauk board at the lumber store that measured 3/4" thick X 8 1/2" wide X 5' long. I ripped that board into 4 two inch strips. I ripped another one of those boards in half and ended up with a piece probably 1/4" thick. The blank was made of three pieces. The two outside piece were 3/4" thick and the middle piece was about 1/4" thick. I flopped the grain and made the wood bow toward each other. I glued it all up with Titebond III. When I took the wood out of the clamps about 3 days later and was trying to square it up I noticed that the wood was pretty severely twisted. I kept running it through the planer but I had no luck. The only things that I can think went wrong were I didn't clamp it to a good straight edge (maybe it was to weak and it flexed with the wood), when I bought the wood i noticed it had a small bow in it would that affect it? Andthe other reason is that I was using different clamps and maybe the uneven pressure from the different clamps made the wood twist. I wasn't really sure so I wanted to check with you guys to see what your input is??

[fishizzle77]

When you cut your lams did you let them sit for a few days or did you go straight to the glue factory? Clamping to a straight edge is mandatory. What types of clamps did you use? Did you use pressure blocks when clamping? Also, did you buy that piece of wood because it was discounted?

[gear junkie]

A planer only makes the sides parallel. First run one side on a joiner to get the blank flat, then run it through a planer.

[Alex1]

No, when I cut them I glued them right after. I used c clamps and rachet bar clamps. I put about a 4 inch piece of wood under each clamp to try and distribute the pressure evenly. And no the wood wasnt discontinued.

[Ric.Fallu]

Wood is a natural material, and does what it wants. Sometimes strange things just happen.

But, seems to me, the two things that count are:
• grain direction/straightness
• water content

There are internal tensions in many timbers – they are mainly influenced by the grain direction. If the grain is perfectly straight and even, changes to water content probably wouldn’t make much difference, just make the wood expand or contract slightly across the grain – but you never know what is going on inside your stick.

If you have bent grain, and the internal water content changes, the wood will bend (more so in some timbers, and less in others). My personal experience suggests that as wood dries, the grain tried to straighten out (but that may not apply to all timbers).

Ideally, flipping will set one bend against another, balancing it all out, and producing a stable stock, but if the internal bend was not uniform across the stick, the tensions may not match, and a balance may not be achieved.

So:
• What is the grain like in your wood? Is it straight or bent? Is it uneven from side to side?
• Has there been a change in the water content - is the wood still green and water is evaporating off or has there been a dramatic change in atmospheric humidity? Cement can contain water, and strapping wood to a piece of cement can induce a bend, even if the cement is dead flat.

I have a saying that “every problem is fixable” but laminated stocks that bend may be more trouble than they are worth. If you can fix it, you still mightn’t trust it to remain stable. Make another stock, and put the first in the shed for a year – if it stays unchanged, it is stable and probably OK for a speargun stock.


Ric

[fishizzle77]

I agree w/ Ric. Get another piece of padauk & start over. Try to get a piece that doesn't have a bow in it already and after you cut your lams let them sit for a little while. Go to a metal shop or your local hardware store and get a 6' piece of angle iron. Take your 90 degree w/ you for perfection. Wrap it in foil/saran wrap/whatever you choose and glue to this next time.

[HWD]

[Alex1]

Alright that will probably be what I am going to do. How long do you leave it in the clamps before taking it out?

[Ric.Fallu]

Leave the lams in clamps until the epoxy has well and truly set. I usually leave overnight. I also find it easier to do a lam at a time. Takes longer, but you get a neater job.

Ric

PS: seems to me that the reason for letting wood rest after cutting is that the internal moisture content may vary from that at the outside. When the wood rests, the water content has time to come into equilibrium with the external air, and the stick won't move after being attached to the other ones.

[Alex1]

Alright thank you. I will give it another go. Also, instead of just clamping the wood to one straight edge do you think it would be a good idea to sandwhich the blank in between to pieces of angle iron? I was thinking that, that wouldnt allow the wood to move at all. What do you think?

[Ric.Fallu]

You can lay the laminates between two forms if you want, but it seems a little like overkill to me. I dunno how many stocks I have layed up (hundred or so?) but have never used a form sandwich. Just use as many clamps as possible.

Ric

[eward4]

I clamp mine up between two pieces of angle iron. If i'm not in a hurry I usually just leave it clamped up for a few days. The wood can't bend between those pieces of angle iron.