Need some advice on making a large table

[Barry Lyndon]

My boss has asked me to make a conference table for the company and I have a couple things I need some advice on.
He wants a 4ft x 10ft Cherry conference table. Very simple, basically just boards running the length of the table (so 10ft long boards) glued up to make the 4ft x 10ft surface on hairpin legs. Basically this -

https://goo.gl/images/yU5vSp

No apron. Do you all think I'm going to have problems with sag if I use 8/4 boards? I plugged numbers into some of those sag calculators online and it looks like they are saying anything 1.25" and thicker would be fine but most of the calculators seem to be for shelves and have some unnecessary variables so I'm not sure it's completely applicable.
Second question: what about racking? Normally with a more traditional table I’d be making an apron and wooden legs and the apron/base would essentially eliminate any racking issue. I’ve never seen a hairpin leg table with an apron. They are always just a top with legs screwed into the corners. Is that because hairpin legs account for racking somehow? I was talking with some people in another group and they were most concerned with racking on a table this size. Are hairpin legs just not meant for large tables?


These are the legs we were looking at -


https://www.hairpinlegs.com/products/raw-steel-original-leg


1/2" steel rods. Their FAQ indicates 4 of them can support a couch with 3 or more adults. That would be 600+ lbs. The table top will be 80bf of Cherry. Cherry is 3lbs per bf so total 240lbs. Seems like it should support it no problem. I'll call them tomorrow to confirm though.

[Andrew Hughes]

No way, That's a terrible idea.
Go back to the drawing board with him.

[Barry Lyndon]

No way, That's a terrible idea.
Go back to the drawing board with him.

Can you expand a little on that?

[Jamie Buxton]

An 8/4 slab top will be completely solid. That's presuming you can get nice 8/4 cherry which is 10 feet long, and straight.

Those hairpin legs are structurally worrisome on a big table like that. You have to expect people to grab the table, and drag it sideways. The legs should not rack or get ripped out by that move. It would help to know how wide those legs' tops are. They look like 3-4 inches, which isn't much.

And, to my mind's eye, hairpin legs just look too teensy on a big conference table that's ten feet by four feet. I'd want something more substantial looking.

[Wayne Lomman]

Make a 25x50mm RHS steel frame and bolt the legs to this. It solves all the structural worries of racking and sagging. At only 25 deep it will be almost invisible. It looks slender but remember that a large conference table is rarely moved. Also, attach the top to the steel in a way that allows for timber movement. There is no problem successfully creating this design. Cheers

[Robert Engel]

A table that long I can guarantee it will sag w/o support, 8/4 or not. But I'll bet there is some support system under this table.

Since its for the boss, I think it has to be doable :).

My initial thought would be angle iron running lengthwise in a groove and rabbet that keeps it flush to bottom. I would also run a few cross sections to counter act any cupping forces. Basically, construct a frame that will be rabbeted into the bottom. Make sense?

Yes, for a table that big you don't want spindly legs. You can use the same design, but go with 1" round stock.

I think the biggest issue is vetting out the wood source and getting the wood acclimated because like any top, warping and cupping are the big issues.

[Jim Becker]

I agree that more support structure is needed for that size table top...consider how heavy it's going to be! And then add the weight of people leaning on it as well as other things they put on top of it while working. Personally, I'd design a base and legs that mimic the idea, but have a more stout structure, including a supportive frame for the top and have it welded up and painted.

[Barry Lyndon]

Thanks everyone for the info and for your advice! We're going to go with a base of some sort now (likely metal). I appreciate it!

[lowell holmes]

I would be concerned about the top warping with no aprons on it.

[Roger Marty]

I would be concerned about warpage, not sag. If you did a 2" thick edge-grained table, it would likely work.