Making uber THICK light-weight panels

[John Maeda]

I'm building this aquarium stand with intersecting tables. The black table is really just a facade, that pulls apart for under stand access. The white table will have a hidden center beam since it'll be holding up 1000lbs of water.

Whats the best way to get the thickness I want for the side pieces(3 inches thick) while keeping this reasonably light-weight? I was thinking 2x4s glued up as a frame, with two 1/4" pieces of ply covering either side, and a veneer on the ends when finished.

Is there a better way to do this?

[Joe Chritz]

Trosion box is the standard for lightweight and strength but I don't know how it would hold up on end. I assume it would resist bowing the same as using it to span a distance.

1/2 ply for everything or 1/2 grids with 1/4 skins. Face it with solid wood. Do the same for the top and it will easily hold that weight if not a lot more. There are calculators out there on the net for figuring the sag in a torsion box.

Must be about a 100 gallon tank? I am planning a stand for a 40 and a 60 right now and will most likely use plywood sides with an applied panel end. If the stand is 20" deep and only rests on the ends that is only 25 pounds per inch of side(at 1000 lbs). Properly supported with stretchers it should be plenty strong.

ETA: If you start to feel bad about your design go look at a commercial stand. The one I have for a 60 gallon is a 2x frame with 1x panels nailed from the inside. Anything you build with any thought is likely to be many times stronger.

Joe

[John Maeda]

ETA: If you start to feel bad about your design go look at a commercial stand. The one I have for a 60 gallon is a 2x frame with 1x panels nailed from the inside. Anything you build with any thought is likely to be many times stronger.

Joe

Thanks Joe,
Actually i'm comming from *gasp* using ikea furniture with cardboard filled skinned panels for aquariums. The hold up... but just barely that. I resorted to this behavior after observing that most commercial stands are particle board at best(with a hefty price tag that does NOT reflect construction/materials).

This being my first LARGE tank I was a little worried.

So torsion box eh? I'm hunting for a calculator as I type this.

[John Maeda]

Bottom piece as well as table top.


Covered in ply.


Side pieces, use the same size interior boards as the top and bottom.


Covered.


Adding edges.


Covering the faces with edge veneered ply.


Cutting out the insides.

Not Pictured
Taking the router to all corners and rounding them over with a 1" bit(?).

Is this too overkill?

As it stands I'll be cutting boards forever! The interior pieces alone amount to 130 short pieces, and 28 long pieces.

[Greg Funk]

I don't think you need or would benefit from torsion boxes for the vertical or bottom pieces.

A torsion box for the top would be good and with a 2" thick torsion box with 1/4" skins you should see less than 1/8" deflection with a 1000lb load. For the sides I would just use 2 pieces of 3/4" plywood separated by some vertical ribs to achieve whatever thickness you want. The bottom could be just a single piece of 3/4 plywood with some supports under each vertical section.

For reference, you might consider buying "More Woodworkers' Essential Facts, Forumulas & Short-Cuts" by Ken Horner. Lots of good info on Torsion boxes.

For construction of the top torsion box I would use 3/8" skins and ribs. When you make the ribs you can cut dados halfway through every 6-8" (or whatever spacing you decide on) then the pieces just interlock together and it simplies the overall assembly.

Greg

[Chris Padilla]

Water weighs a little bit less than 10 lbs/gallon but that is an easy number to design for since your aquarium will have rocks and gravel that weigh much more but will be much less in volume than water.

Using torsion-style boxes for the sides and center support certainly won't hurt anything and since you are doing the top that way, might as well do the whole thing that way if it makes any sense.

I would normally suggest making everything out of MDF but you want it light so I think plywood is the way to go for everything.

The joint Greg suggests is called a half-lap joint although it is not the normal face cut joint one normally thinks of...it is cut half way into the thickness of each piece so you can literally create an interlocking grid. I did this with MDF and had my dado blade dialed in so tight that a dry fit of two pieces of 3/4" MDF were extremely difficult to separate; so difficult that I didn't even bother gluing the MDF grid together; I only glued it to the two skins and side pieces!

[John Maeda]

Interlocking pieces sounds like a good way to go for the grid.

I will have to resort to doing this with a chisel, or the router as I don't have a table saw (just the ts55).

If I can't make a good halflap joint, I can always stack the 2x4's and cut them all at once very carefully. It only comes out to 8 cuts a side.

[Joe Chritz]

Without a tablesaw I would use 1/2 grids and just brad nail or staple them together with some glue. Search out David Marks torsion box or the very similar one by Mark Spagnuolo.

You don't "need" the torsion box sides but they are pretty easy to build once you have a nice flat surface to work from. If you don't have one yet I would build one box to work on and then build the others on that. Money well spent believe me.

Do you have a miter saw? You will need someway to cut a lot of pieces exactly the same length and width. The TS55 is a great saw (have one myself) but a tablesaw would speed up the process greatly for the grid pieces. Anyone you know that has one you could cut the pieces on? It wouldn't take an hour if you knock the pieces down to manageable size at home first.

Joe

[John Maeda]

I'm resorting to sneaking into my former schools woodshop, and 'borrow'
some miter saw time and pray nobody notices...

I've already been booted from the laser engraver more times then I'd like.

Otherwise i'll just borrow/buy a cheap saw, or get creative with the ol'circular saw. I'll figure something out.

[Joe Chritz]

The cross pieces look like seperate pieces in your sketch up. They should be one piece with short pieces between.

I don't know where you are located but you may be able to borrow some tablesaw time from someone. Other thing is to gang up as many pieces as you can and cut them to width all at once with the festool.

Joe

[John Maeda]

Yah, ignore those pieces. Just left over bits i forgot to erase.

I think i'm going to try my hand at the stack and cut. It works well for plywood, I don't see why it won't work for 2x4's.

[Joe Chritz]

I must be confused but all the grid pieces of a torsion box are generally fairly thin sheet goods.

You should be able to rip 4 sheets stacked up with the TS55 easy. That would be enough to do all of the top I think.

If you haven't checked out the torsion box sites mentioned it is well worth the time. You could build that from all 1/4 ply and it would be strong enough. The biggest reason to use 1/2" grids is for easy of fastening.

Joe

[John Maeda]

I must be confused but all the grid pieces of a torsion box are generally fairly thin sheet goods.

You should be able to rip 4 sheets stacked up with the TS55 easy. That would be enough to do all of the top I think.

If you haven't checked out the torsion box sites mentioned it is well worth the time. You could build that from all 1/4 ply and it would be strong enough. The biggest reason to use 1/2" grids is for easy of fastening.

Joe

The inside grid was built using 1/2" thick boards and the skin is 1/4 inch.

I've been looking at a few sites. This type of design will make my future furniture building projects a lot cheaper to make (a little more time consuming though). Are there any specific ones to look at? I didn't see any mentioned in the thread.

[Paul Simmel]

The torsion box concept is a great one, and I made myself a 4' x 6' assembly table with 3" tall 1/2" MDF grid pieces sandwiched between skins. I may be wrong here, but the reason for the grid is because you want the strength and flatness to be "everywhere" in every direction... hence a stiff work surface.

But, for your application, where you are more concerned about sag, *especially* with your center support, I believe you do not need the grid. All you need are slats running lengthwise. Less materials, less work. Strength is where you need it. Your two ends and the center support will stabilize things laterally. I am assuming you're going to have a back.

I've been building shelves this way for years (1" slats with 1/4" skins for top/bottom, with wood face edging. They are light, and very strong.

You're still going to need a flat reference surface, though.

Here's a decent video on TB construction:

http://e3.video.blip.tv/157000048459...ableTop311.mp4

[John Maeda]

Hey Paul,
Sadly there won't be a back. This table/stand thing is for an aquarium that goes in the middle of a room.

If its possible i'd like to take out the middle brace actually, but i'm very frightened by the prospect of 1000lbs of water coming crashing down, along with a lot of money in glass and live animals.