[Sbthomas13]

Bob,
I decided to go with the torsion box table because I loved how stable it made the Joe's 2006. When you say line up the cores do you mean have interlocking interior ribs? Or do you mean just keep the interior grids in a straight line?

I considered interlocking them but it would be so much extra work routing/slotting each rib to have them fit together. It really wouldn't add much in terms of stability I don't think by interlocking them.

However, as advised by madtownrob I am going to change the design and line-up the interior short grid pieces and not stagger them. So I will be modifying the design tonight to keep the short pieces in-line. It won't be too much harder to do this, I will just have to toenail them.

The table is based off of this design: http://www.taunton.com/finewoodworki....aspx?id=28855

I did some calculations on the weight of the torsion box top:
I just did some calculations on the weight of the Torsion Box Top:
From Manufacturer:
- (1/2" MDF) = ~ 2.5 lbs per sq ft
- (3/4" MDF) = ~ 3 lbs per sq ft

So for the interior grid (1/2" MDF) there are the following parts:

(63) 7.25" x 3" x .5" Short Grid Piece
(8) 57.5" x 3" x .5" Long Grid Pieces

So I did the following math to calculate their weight:

(144/2.5)=(21.75/x) so x=.377 lbs per short grid piece .377*63=23.789lbs
(144/2.5)=(172.5/x) so x=2.994 lbs per long grid piece 2.994*8=23.985 lbs

The outer frame of the grid (3/4" MDF) includes the following pieces:

(2) 3" x 59" x 3/4" Sides
(2) 3" x 69.75" x 3/4" Sides

To calculate weight:

(144/3)=(177/x) so x=3.6875 for (2) of the sides so 3.6875*2=7.375 lbs
(144/3)=(209.25/x) so x=4.359 for (2) of the side so 4.359*2= 8.718 lbs

And I am not going to show the calculations for the skins but (2) skins should = 144.94 @ (72.469 lbs per skin)
So all together the torsion box top should be:

23.789 + 7.375 + 8.718 + 23.985 + 144.94 = 208.807 lbs

So including the hardwood wrapping around the edge of the torsion box the top is going to be ~215lbs !

For a more in depth view at the torsion box table build I am doing a more detailed work log here: http://woodwhispererforum.com/showthread.php?t=1702

I'll keep you guys updated,
- Spencer

[harryn]

Hi Spencer - it is good to have you back and building again.

If I may, I would like to suggest a possible alternative to the MDF torsion box construction. It is true that the torsion box is a conceptually strong design with a number of benefits. I don't like building them, mostly because it is too much work to make a nice one.

As an alternative, may I suggest instead to use a single sheet of structural panel. There are both foam core and honeycomb core versions of these, and even 1 inch thick of these boards is stiffer and flatter than most any MDF torsion box.

Here is an example of the Al honeycomb version: http://pacificpanels.com/

It is not an inexpensive material, but there is a lot of scrap generated when it is cut to size industrially. I managed to drive over to this place and get some scrap for free from the owner for my son's science project. (some I still have for my build)

The foam cored material is actually quite strong as well, and you can get it with either MDF or plywood skins.

Anyway, good luck on whatever path you pick.

HarryN