Supporting and spanning a table top

[James Jayko]

Hi All -

I'm building a table. The top is 1 3/8" African mahogany, 144" x 36". Best I can tell, its about 54 board feet, and about 150 lbs. As it is today, I have two legs which are roughly 24" long by about 3" wide where they meet the table/5-6" wide at the floor, at 3 and 9 feet (so there is a 6' span which is unsupported in the middle of the table). I guess its what you'd call a trestle base; I connected to the two legs with a beam roughly 2" x 6", through-mortised and using a wedge to hold it all together and allow relatively easy disassembly.

My question is about the strength of that top and its ability to support itself over the 6' span, or if it needs to be supported in the middle. The top was originally two pieces, jointed and glued with Titebond 2 and Dominos. Does anyone have any thoughts about this, or is there any formulaic way to determine what is or is not necessary?

J

[Jamie Buxton]

Hardwood 1 3/8" thick, 36" wide, spanning six feet? No, no further support is necessary.
But rather than relying on some random guys on the web, you can test the situation yourself. Prop your top on a couple supports six feet apart. Maybe they're just 2x4s on the shop floor. Stand on the middle. Look to see if you see any deflection. I'd expect you to be able to dance on it.

[David Gutierrez]

Jamie that is some good advice!

[Brian Tymchak]

James,

There is an online tool to compute sag over span - called the Sagulator (http://www.woodbin.com/calcs/sagulator/)

The answer to your question is going to depend on how much weight you need to support and how that weight is distributed over the span. You can play around with the loading in the Sagulator.

Bottom line is that if you are building a dinner table, should be no problems.

Edit: An easy, almost invisible way to add support to the middle of the table would be to add an apron right under the top between the legs down the middle. Maybe 3" or 4" wide, would add a lot of support.

[Andrew Pitonyak]

Hardwood 1 3/8" thick, 36" wide, spanning six feet? No, no further support is necessary.
But rather than relying on some random guys on the web, you can test the situation yourself. Prop your top on a couple supports six feet apart. Maybe they're just 2x4s on the shop floor. Stand on the middle. Look to see if you see any deflection. I'd expect you to be able to dance on it.

I think that Jamie here missed the most important thing... I it is imperative that you video tape yourself while dancing on said table top and then post the video of you doing it :D

[James Jayko]

Thanks for all the help! That is the best case scenario answer.

[Victor Robinson]

I think that Jamie here missed the most important thing... I it is imperative that you video tape yourself while dancing on said table top and then post the video of you doing it :D

Right. Exactly this. How else could we help you determine whether there's any deflection?

[Bradley Gray]

There's no other answer.