Bent laminations and cross banding.

[iublue]

I have done several bent lamination pieces but I have always oriented all the grain the same direction. Has anyone done bent lams and cross banded it, essentially like plywood?

Are there any advantages to cross banding? Major or otherwise?

Are there any disadvantages?

[Paul K. Murphy]

I've only done bent lamination a few times. Like you, I've always oriented the grain longwise.
I think I would only be persuaded to use crossplys if the assembly started to be more panel-like. A narrow assembly (say 2" to 10" or so) is more like a bent board than a bent piece of plywood. A wider assembly would begin to resemble a bent plywood panel. I think crossplys might make more sense then.

[Baddad]

Are you concern about splitting? Cross banding would prevent it like plywood. The glue lines IMO help prevent it. I don't see a benefit to it.

[iublue]

No, I am not concerned about splitting. I was just curious if anyone did cross banding and if so, why.

[Alan S]

There was an article on p. 35 of the Spring 2009 Woodwork Magazine on "Fineply", or hardwood plywood laminated using epoxy and a vacuum bag. There were some very interesting effects.

[Shovel Man]

I have considered it but not done it yet. My thought is to gain strength by preventing splitting. I would only angle the plys a few degrees each side of straight. That should allow expansion and also prevent splitting. Might be stronger in normal bending than solid wood which can shear (split) in some cases.

[handi]

I have done both, in fact I have helped clients develop formed plywood chairs.

What are you attempting? Chair arms, rockers and such (long and narrow) the cross plys gain you nothing. The narrow parts offer no opportunity for be racking along the long profile.

More panel like projects (chair backs, seats, etc) do require cross plys. The real difficulty is in finding large enough sheets. You usually cannot buy sliced woods wide enough for the cross plys. You need to find rotary sliced wood an eight thick or less, and those are hard to come by.

Ralph

[iublue]

I am right now in the process of laminating some curved panels for table legs. I was in the middle of it when it occurred to me that maybe cross banding might have been an option.

This time all the grain will be parallel but maybe next time I would try cross banding if it is a good thing to do.

[JGrout]

I have done a lot of far more serious bending of wood using laminations laid parallel in a glue up than the bend in a chair arm and find that there is not one good reason to cross band an arch of any sort.

Besides, think about the edge of the lamination if it is cross banded It may be fine if the edge is covered up ( another unnecessary step if the flitches are laid parallel ) otherwise there is still no point

Joe