How to straighten thin sheet

glue it to some 3/4" plywood

Can't do that. I'm making a lens board for my large-format camera.

Do I need to find a straight piece to start with?

yep.

Struts, like used in Guitar top bracing could be used OR

Wellllll- sticking my neck out here. If you can enclose it in a frame of some kind during it's application, that might help OR !!!

Try this: Weigh your board Dampen the board-- both sides Find a REALLY flat surface-- maybe your TS Lay down newsprint ( NOT NEWSPAPER- newsprint is the paper they make newspaper from - get some at the local crafts supply - paper towels work, but use more-- an extra layer)- maybe 5 layers (plastic on the TS or it will rust) Lay down your board lay down More newsprint add a REALLY flat piece of Steel same size or larger than board-- Aluminum will work, MDF??? maybe if it is about 1 1/2 " thick (two layers) If you use MDF or plywood put plastic between the newsprint or wood on top will warp also Clamp like HELL-- Really full 5 gal paint cans come to mind.-- use two or three

After 24 hrs change news print for dry stuff- Keep this up for at LEAST three days ( make sure your 1/8" piece of wood is dry) Keep weighing your board- when it weighs the same as when you started, it is sstable -- USE & finish immediately (if it's flat enough for your purpose

If this is TMT, buy a flat board

What about getting it wet, and then sandwich it between 2 flat objects with some weight on it? Paper towels in between to speed the drying.

go ahead if you want. for your particular board, this one time, somehow, it might work. all you have to lose is a little wood and time.

let us know what happens.

You could rim it with a really sturdy frame, if not slots in a box then a thick metal frame. (Sorry, I don't know what a lens board is so I can't tell if that makes sense in your application.)

That's your best bet. It's a small enough board.

- Owen -

Depends. Shoot everything at f64 and you might be ok.

It seems to me that 1/8" wood is pretty thin for for a lensboard. I'd just as soon use a piece of aluminum. It won't be subject to seasonal expansion/contraction issues, and will have no problem supporting a heavy lens. Cover the front with leatherette and the back with flocking and it won't look too bad. If you want to stick with solid wood maybe you could laminate two thin pieces of wood together under pressure. It'll be thicker than 1/8" but you could always rebate the the edges and the rear of the lens hole if you need to.

My plan was to reinforce the 1/8" with strips on the inside, outside of the lens hole. 1/8" might not even fit in the slot of my camera, however I planned on sanding down the edges to form a wedge.

I've thought about aluminum however working with wood will be far easier on my limited tools.

I also have a piece of teak wood that is perfectly straight. I may just use this rather than the cherry.

Thanks for the feedback!

A lens board is part of a view camera. It fits into a frame on the front of the bellows to hold the lens. To change lenses, you change the board.

The advantage of this arrangement is that you can tilt the lens to correct for parallel distortion and such as well as moving the lens up and down to get 'impossible' shots.

I'd definitely get a better piece of wood. Flatness of the lens board is critical on one of those camera.

--RC

"Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

How about veneering the outside of a piece of 3/32" aluminum with a really nice wood? Should remain flat if it's properly clamped when drying...

In that case -- he shouldn't be using wood at all, but something that won't change shape in response to changing humidity (plastic or metal).

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

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It may be perfectly straight now, but will it *still* be perfectly straight in six months when the humidity is significantly different?

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

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You need to make the lens board in three pieces (tongue and grooved together), consisting of two side pieces (vertical grain), and one center piece (horizontal grain). This worked well for my 810 lensboards. I used 3/8 mahogany, but cherry should be fine.

Curt Blood

PGG wrote in news:pan.2005.02.02.05.04.56.996000@NO_SP_A_Myahoo.com:

Cherry is not really a good choice for what you're trying to do. It doesn't tend to have that straight of a grain, and that introduces the small stresses that, when cut very thin, take it out of flatness. If you wet & weight it, as has been suggested, there's a good chance it will just flex back into the same shape as it dries back out.

Teak might be a better choice. Pattern grade mahogany would probably be even better (and cheaper than teak).

John