Where to get honeycomb material? (for torsion box)

[Doug Hobkirk]

Torsion box design = GOOD
Grid of ply or MDF = BAD
heavy, lots of work, makes box too deep
Cardboard (PVC, plastic) honeycomb = GOOD?
airplanes use it But I don't know for sure:
that it really works
or how thick it should be
or where to buy it cheap!Any thoughts? Thanks!

[Scott Velie]

Fiberglass boat builders use it. That might be a place to start.

Scott

[Matt Mutus]

It definitely works. more thickness = more stiffness. you can buy some here.

http://www.vacupress.com/accessories.htm#honeycomb


If light weight is your priority, I think it's definitely better to use honeycomb or some other material designed for this purpose (like end grain balsa core).

But setup, uniformity control and gluing, is far easier with grids, which is why I think a lot of people go that route (especially if you are not set up to vacuum bag it - which most people aren't).

[Glenn Shotwell]

You could try these places too:
http://www.cstsales.com/honeycomb.html
http://www.aircraftspruce.com/catalog/cmpages/01-00488.php

[Doug Hobkirk]

Why would vacuum clamping be necessary?
It seems to (inexperienced) me that 2 sheets of 3/8 or 1/2 plywood would bond well using sandbags or any serious pressure.
Despite my questioning your words, I am very pleased at your responses, the links you gave, and your seeming expertise. Thank you all!

[Matt Mutus]

this is just my humble opinion so your mileage may vary.

You need to attache the skins to the core perfectly flat and parallel. This is easier to manage when the core is a rigid grid, than when using a sheeted product which flexes. By flexes, I mean prior to the attachment of the skins not after. I.E. you can take a sheet of cardboard honeycomb and bend it and depress it with your hands - wheras a solid gridwork will retain it's shape under considerable pressure. That means - when using a grid - you can be reasonably sure there will be no deflection out of the plane once the adhesive is applied, and you start applying pressure to the skin.

So I'm not talking about winding up with a good bond, so much as retaining shape under pressure - before the pieces are bonded together.

Using honeycomb, sandbags weighting down plywood is not likely to give you the even pressure you would need to retain uniformity. With a vacuum, you wouldn't have to worry about which points are being applied too much or not enough pressure.

I'm not saying you can't do it without vacuum, you could use other means of spreading the pressure evenly. But it's a lot trickier than using a solid grid core.

Just out of curiosity what size box are you making? what dimensions and what thickness?

[Doug Hobkirk]

First, thanks for your humble answer. Makes sense. Thanks.

I was considering using it for several worktables:
20x30 or 24x36 for my tablesaw, router, drill press, etc.
30x60 for an EZ system table

In all these cases it would be better to have thinner tables. But in all cases I could also simply use plywood! I was just considering being ultra trick. (Oops - did I just admit that?)

[Frank Caponi]

If all your after is a filler for a firm rigid table then why not just use a piece of 3 inch thick rigid insulation - It comes in 4' X 8' sheets - Since it will be sandwiched between two sheets of plywood or whatever then it will work - It can only fail if you can concentrate force onto a small area or point - There are poly adhesives that are made for this product that will fasten it to your skin - Not eat the foam and never let go - The idea of a torsion box is that it is First rigid - Second dead flat - The only way I know of to be assured of that is to use a material that can be machined exactly and each piece can be attached to the skin - It is a genuine time consuming pain in the rear process to build one - But - Once done and well maintained you shouldn't have to make another one in your lifetime

[Cliff Rohrabacher]

For shop tables I'd suggest you trade off the light weight for hefty and make you boxes heavy and strong

Here was my approach.
http://www.sawmillcreek.org/showthread.php?t=64965&highlight=Torsion


I mounted removable legs to mine, applied white Formica to the top, and painted the thing white. It's a beast but it's bullet proof and storable.

[Rich Schneider]

My torsion box is made of 1/2" and 3/4" MDF, is 4ft by 8ft and is about 5 inches thick, finished with tung oil...very heavy no doubt...very stable and flat, never a problem....I have mine mounted on a 6000 lb capacity electric/hydraulic lift table that raises it up and down from floor level to 36" and is on rollers so I can move it around the shop really easily (I got the lift at a printing equipment company auction for $25..needless to say the auction wasn't very well attended and it was one of those once in a lifetime deals for me)...love it, wouldn't do it any different....

[Dave Cav]

I made mine out of 1 x 6 lumber ripped/jointed to 5" for the grid and 3/8 ply for the skins; glued and screwed the skins on. Made it 4 x 8' for a work/outfeed table top. Below the top are several 4 x 8 shelves where I store my sheet goods, and the whole thing is mounted on large heavy duty casters. Works pretty well, very solid.

[Mark Rios]

Okay, I've done a whole ton of research and I finally came up with this material. Seems perfect for your project. Comes in a 5-pack.

http://www.amazon.com/Post-Honeycomb-Cereal-14-5-Ounce-Boxes/dp/B000FKBO9G/ref=sr_1_6?ie=UTF8&m=ATVPDKIKX0DER&s=grocery&qid=1199253854&sr=1-6

[Dave Lindgren]

ROFLMAO!!! You may want to treat it with something to keep kids and mice away :D

[Alan Schaffter]

The honey comb pictured in all the posts is too thin. You want a web that is at least 3" -4" tall. It can probably be made from thinner stock than 1/2 MDF. As far as the skins go, it depends on what kind of concentrated loads you will have and the spacing of your web pieces. For a flat table with no concentrated loads you could use 1/4" MDF! Engineering-wise the skins are in compression (top skin) and tension (bottom skin) in the plane of the material. The web just keeps the two skins apart. For a flat, light-weight, table that doesn't need to have a strong top, a hollow core (cardboard core) door works just fine.

I used a 1/2" MDF web and 3/4" skins and edges for my assembly table that takes a lot of abuse- It is flat and strong, but heavy. I made my own manually adjustable legs.

http://www.ncwoodworker.net/pp/data/500/medium/P4290038.JPG
http://www.ncwoodworker.net/pp/data/500/medium/P4290041.JPG
http://www.ncwoodworker.net/pp/data/500/medium/P4290045.JPG
http://www.ncwoodworker.net/pp/data/500/medium/P5080003.JPG

[Matt Meiser]

If all your after is a filler for a firm rigid table then why not just use a piece of 3 inch thick rigid insulation - It comes in 4' X 8' sheets - Since it will be sandwiched between two sheets of plywood or whatever then it will work - It can only fail if you can concentrate force onto a small area or point -

I wonder if a scrap piece of Insulspan or similar might work for this? Who knows how flat it is though?

[David Sharp]

http://www.nida-core.com/englishsearch.htm (http://www.nida-core.com/english/search.htm)
this material comes in several thicknesses and has an outside skin which would make bonding easier. I personally have never used it. The thickness that I have seen used was about 1" for boat decks and hatches.

[Ted Jay]

http://www.nida-core.com/englishsearch.htm (http://www.nida-core.com/english/search.htm)
this material comes in several thicknesses and has an outside skin which would make bonding easier. I personally have never used it. The thickness that I have seen used was about 1" for boat decks and hatches.

Check out the sandwhich construction article:
http://www.nida-core.com/english/nidaprod_honeyinfo_sandwich.htm
That should do it....:cool:
Ted