1" thick plywood?

[sacherjj]

Our local woodworking group has a yearly challenge. I guess it would be similar to the 2x6 contest here. (Last year it was a 2x4 contest.) This year, it is a half a sheet of plywood contest. You can use whatever thickness of plywood you want, but just 16 square feet of it. The piece I am designing would be much better with thicker wood, as it is going to be built up by gluing cut out shapes of the plywood together, with the edges exposed. A sheet of 3/4" is going to be cutting it very close. I would prefer 1" or slightly over. However, I have never seen this before. Does 1" or 1-1/4" 5-7 ply plywood exist? If it does, where does one pick up a sheet?

[gmack5]

Check out a product called "Appleply", available here in the States, similar to Baltic Birch and is available in 1" thick pieces. Because it's relatively expensive, you're going to have trouble finding it. Good Luck!

[cwsmith]

One inch and thicker plywood used to be fairly common and is the preferred material for table use on the once popular Radial Arm Saws. I'd check with your better lumber suppliers to see if they can order it for you. The big box and similar chain stores do not carry this and probably don't have it on their supplier's list.

CWS

[Tequila]

If you glue the two half sheets together, you've made yourself a half sheet of 1-1/2" plywood. Seems like that would meet the rules.

[sacherjj]

If you glue the two half sheets together, you've made yourself a half sheet of 1-1/2" plywood. Seems like that would meet the rules.

Yeah, I thought about using that as a loop hole. They really couldn't tell, because I want to use fairly rough, 5 or 7 ply. My plan was to make the prototype out of 1/4" at 1/4 scale, from 12" square piece, on the scroll saw. If that worked well and I could make the cutlist work, go with 1". If I use 1.5", that would give me even more leeway.

Thanks for the info all. I will post pictures of the chair as I finish it. Hopefully it will work.

[sacherjj]

For further information, in case someone is looking for the same thing via search, I have located a local supplier who carries 1" thick AC plywood. Just what I was looking for. So it is available at cheaper cost than Appleply.

[sacherjj]

I built a quick prototype on the scrollsaw, at 1/4 scale. The actual chair will be 17" wide (17 pieces of 1" ply, so just under 17"). This only has 12 plys, because I cut out 5 of the back and seat pieces that are the same. I mainly wanted to make sure that the design I made on paper looks decent as a chair in three dimentions.

Each layer alternates, so the two legs layer on each side will be 90 degrees apart on surface grain. This should give me the effect of over 100 alternating layers making up the chair, with the laminations of the actual plywood sheets unable to be picked out from the actual laminations inside the sheets. I think it will be an interesting look.



I plan on using small aluminum tubes to align the seat and back, then threaded rod to provide clamping pressure. These will be inside final outside ply. Once that is dry, I will clamp the final outer layer onto the side, which will hide these holes. I'm not sure what to use for final shaping. I've heard abrasive tools work better on plywood and some have used an angle grinder for this type of work. Not sure if that is better and a surform or something similar. I think I will add a little ridge underneath the seat for little larger space between the compression and tension forces. Although 3" is a pretty thick seat to begin with. Decisions, decisions.

[jdschulteis]

From the prototype, I think it will look pretty good. Using most (?) of a half sheet of 1" plywood, is it gonna be a bit on the heavy side?

[just4funsies]

It'll probably weigh what a half-sheet of plywood, plus a bottle of glue, would weigh... Now if you could only find a half-sheet of 24" thick plywood, you could make several chairs, and win the contest hands-down!

[sacherjj]

It'll probably weigh what a half-sheet of plywood, plus a bottle of glue, would weigh... Now if you could only find a half-sheet of 24" thick plywood, you could make several chairs, and win the contest hands-down!

And that would give me a great excuse to get that 25" riser kit for my band saw. Although I'm not sure my cut down table can handle a 2400 lb piece of wood. The design is for 17" wide, so I could get by with an 18" piece...

It will be heavier than your average chair, that is for sure. I think the majority of the seat strength will be from the portions within 1" of the top and bottom of the seat, as those will be the main places for tension and compression. So I may drill out a little more in the center, in an offsetting pattern. From the patterns that I'm coming up with, I believe the initial rough glue up will be about 75-80% of the sheet of plywood. After rounding and final shaping, I think I'll be down to 60-70% of the half sheet. And it won't be the weight of a whole bottle of glue. It will be the weight of a whole bottle of glue that has been dried (that will save a couple ounces over the wet glue). OK, maybe a bottle and a half.

I've heard of 25 lbs per 1/4" for a full 4x8 sheet. So I would estimate a 4x4 sheet of 1" would be around 50 lbs. 50*70% = 35 lbs. That is heavy, but not overly so. I think of it like a mix between furniture and sculpture. If I can find the right stain to contrast the end grain from the side grain, the look will be striking.

[linear]

I like the prototype a lot, Joe.

Have you seen this guy's work?

http://kerryvesper.com/

He somewhat describes his technique (not in much detail) here:

http://kerryvesper.com/chairs1.htm

Maybe that will give you some ideas. Best of luck on the contest.

[leehljp]

I like the design! Please post the final results! I would love to see it.

[sacherjj]

I had not seen those. Thanks for the links. I guess it always seems that you are never trully original, even when you think you are.

I'm thinking about glue up time with the main assembly. I don't think I'll have enough working time with standard Titebond II or similar. What glues should I look into that would give me enough time to spread it on 15 layers (58 seperate surfaces), assemble and clamp? My plan is still to use two pieces of all thread through the seat and two more through the back to clamp those pieces and use blocks with washers on the outside. There will only be one outside layer on (legs and run up to back), so the last layer will hide those holes. Hmm. Reading the links for Kerry Vesper's work, he seems to glue and screw the layers together. I guess if I mark each screw location, I can run a three layer stagger. That would also reduce the glue drying issue and I could use standard Titebond II.

Now the chair will weight 1/2 sheet of 1" plywood, bottle of glue, and 5 lbs of screws.

[sacherjj]

I decided that drawing this in Sketchup would be the easiest way to put grids on the patterns to allow me to scale them up. Having Sketchup would have saved 2 hours of work to get to the 1/4 scale prototype. I could see what it will look like in 30 minutes work. I didn't close the outside edge, because I want the sections clean for patterns. I just drew all the profiles on one layer and extruded them to different depths. Then I copied half the chair and scaled it for a mirror image. Grouped each side with its parts and slid them together.

[LCHIEN]

hope the wood is void free!