doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com OT - Laminating plywood?

This winter I want to build a portable shooting bench (rifles) and the plans I have call for gluing two sheets of 3/4" plywood together to get an 1-1/2" thick top.

My experience is that plywood sheets are never perfectly flat so how do I go about clamping them together to get a full contact bond between the two sheets? Screws?

Thanks, Rob

Not knowing how large of a top you are making not sure if clamps would be possible or not, Screws would work fine if you dont mind them being there when you are done, of course you could remove them after the glue sets but then you would have holes. Possibly buy some 1 1/4" screws and screw from the bottom side and dont let them pull through. Is this bench staying out in the weather? If not the you should be able to buy 1 1/2" high density particle board we use for making counter tops, its hard and smooth and you can buy different thicknesses but it won't take weather.

Take the two pieces you are going to use, and then get some 2"x3"(2"x4")that are a foot longer than your plywood pieces. What ever the length is make sure that the 2"x3" are spaced about 10" apart. Glue the boards together and place the 2"x3" with the long side up. Set your clamps close to the plywood on the 2"x3" and clamp them. You should have a minimum of 4 clamps, 2 on each side. You are making a sandwitch. The pressure on the long end of the 2"x3" will make sure that they won't bend. No holes.

What JDW said. It is also wise to site down the edge of the 2x4 to see if it is cupped and put the convex, belly side down toward the plywood. If you can, two finish nails will hold the two pieces of plywood from sliding on each other while you are setting up the clamps

You can also weight down the sandwich with something like cinder blocks if you don't have clamps although the clamps are a surer way to get good contact.

Glue the two pieces, lay them on your garage floor, then put a bunch of scrap 2x4's or 2x6's etc. on top of them. Then drive your diesel dually on top and let it sit for a few hours.

If you buy two new sheets off the same stack they should already fit together perfectly. 3/4" plywood is pretty heavy. You're going to be using fasteners through the plywood anyway to secure the tabletop, so just a bead of wood glue around the edge between the two pieces should be sufficient. Don't over think this...

If you utilize a laminate Baltic birch, like Finnform or McFinn, made for use in building conctere forms, you will have nice prefinished weatherproof surfaces and it much stiffer than ordinary plywwods, so you can probably use a 3/4" thickness for your top and have plenty of rigidity. You will need to seal the edges where its cut for best weather protection, but otherwise it is near impervious to weather and reasonable abuse. I built a deck on the front of a small boat over 30 years ago from a piece of Finnform and it is still sound today. The edges have been resealed several times.

FWIW, Alfred Nobel's father, Immanuel, was the inventor of modern plywood & the rotary plywood lathe that peels the thin verneer from logs. He founded a company called Torpedo to make it.

Hi All:

I too made a shooting table out of 2 sheets of glued up plywood. I too parked my car on the wood in the garage as GregSY describrd. This worked quite well,

One thing that I will suggest is that is that one drives two small nail into each corner on one side of the wood. This will prevent the wood from sliding out of place when one drives on it. Be sure to use plenty of glue! Trowel it on for 100% coverage. I prefer the yellow carpenter's glue. It may be an aliphatic resin type that can also be assembled dry and then heat activated. Of course there is always contact cement but thaat is another story!

Good Luck,

Franchi

The top will be roughly 3x4 ft., the bench will not be left out in the weather, it will have 1-1/2 galv. pipe for legs.

I want something as close to rock solid as possible so I'm going with the 1-1/2"

No dually to use,will a single tire cause it to bow?

I have some West marine epoxy left around here and was planning on that or Gorilla glue but if the yellow carpenters glue will do it clean up will certainly be easier.

One last question, I was planing to glue the pieces up and then cut the final pattern and shape. Will any of the glues mentioned be easier on the saw and router than the others?
thanks, Rob.

Yep, get 90% contact by moving your glue around with a toothed mastic trowel, notched piece of plastic laminate or whatever. 2X battens with the crown towards the ply and clamped at edge; yep, that's good too. One other possibility is a plywood "torsion box". This is basically a frame skinned both sides. Let's say you use plywood for the frame, maybe between 1" and 2" rip. This plus 2 skins of 1/2" ply would give you a benchtop 2 to 3" thick. If you are careful with construction of the frame (2 studs, ribs and plates on 16 or 24" centers) and you make sure that any crown in the skins is opposed (crown up both sides), you should get a fairly true surface which might end up a bit lighter than the double plywood laminate. A torsion box panel with four legs will maintain it's rigidity such that three will touch the ground and the fourth can be shimmed up. Very little chance of it twisting when it's set on uneven surface or ground. Another .02 worth.

I see now that you mention cutting "final pattern" which I take to be cutout for shooter, so perhaps this is not the very best idea unless you build the frame to match.

jack