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Will my table top be strong enough?

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3K views 20 replies 13 participants last post by  Colosnoball  
#1 ·
Hello all. I’m designing a table for serving food and am wondering what you all think about the sturdiness of it as it will be quiet long but relatively narrow. I will be designing the table top at 9 ft long and 16 in wide with 3 x 3 in square legs on the outside corners and an apron going around the back and sides but with drawers at the front. because it is a flip top table, it will either be 3/4 in or 1 1/2 in thick. The apron will be attached by mortise and tenon to the legs. I’m thinking of adding corner blocks to the insides of the legs. I am still worried about the length of the table however and potential sagging or integrity issues. What do you all think? Do I need extra legs or the corner blocks? Would I be okay potentially just adding something else underneath the tabletop for increased strength? I’d prefer not to add the extra legs if I don’t have to as I don’t like the way it looks. I’ve attached pictures of my design so you know what I’m talking about. Any help would be appreciated. I’m still learning here.
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#2 ·
First. I like the thinner top. Second. For rigidity, I think you need to make the top/drawer/apron assembly as a torsion box. The bottom of the torsion box should be 3/4" ply with the exposed edge under the drawers faced with the same hardwood as the rest of the table. Likewise, the top of the box should also be the same as the bottom. Then the top can be mounted to the top ply with screws through elongated holes to allow seasonal movement. All of the drawer dividers should be glued into dados in the top and bottom plywood. All of this will provide substantial stiffness over the length of the table. If the torsion box is mortised into the legs, I don't think you will need the corner blocks.

The bottom shelf could also be a torsion box to further add to the overall rigidity.
 
#3 ·
I think you could run into a problem with this. 8'6" between legs is a long run for a stretcher. Add to that the front will not have a stretcher as it will be drawers. Perhaps vertical support at the midpoint would help. That support would likely have to be carried to the floor. If that is going to be used as a serving table it will likely have decent load on it. Just my thoughts.
 
#4 ·
I have reservations about safety.
Have you taken into account the weight of the food and trays holding it? That length will hold a LOT of metal and food.
Second, with only four legs and that distance and people leaning on it, "racking" is a very serious possibility.
Third, that is so narrow that you need to seriously consider the possibility of it tipping when a few people lean on the front edge at the same time. All of the weight is right on the top edge. It would need to be secured to a wall .
 
#6 ·
Build a suspension bridge over the whole thing? So it'll look ridiculous. What else is new? A lot is obviously going to depend on the materials you plan to use. Some materials are far more dependable than others, but I think B Coll makes a valid point.
Think about the center of gravity. Seems to me you would want the bottom shelf to be much heavier because if the top is heavier tipping is going to be more than just paying someone a gratuity..First time someone opens the drawers, especially if there's considerable weight in the drawers you might want to stand behind the whole thing while opening them..
You could splay the legs outward, but it'll probably look a bit awkward to say the least...
 
#8 ·
The first issue I see are the drawers will cause the loss of both the structural support of a solid apron, and a solid way to attach the legs. I suggest you build it as a regular table and put the drawers underneath the apron. Although it’s a standard design for drawers, I think its risky on a table this long.

Top support is the #1 design consideration. I think a torsion box is overkill and will raise the center of gravity. Thick aprons 4” wide should suffice. If you will be piling a lot of weight on top you can add a stretcher lengthwise between the front and rear apron.

So the table unfolds and then you slide the whole top so it overhangs evenly? How wide would the extended top be? Rather than slide outs, I would use folding buttress supports that hinge off the legs. Since this is a long table a leg in the middle, at least in the rear to add a middle buttress. It will also add a little more weight at the rear which will counteract any tipping force.

So, I would reconsider the apron structure, the folding top and whether a 20 or 24” table would work.
 
#10 ·
#1… You’ll need an 8/4 top. 3/4 will offer no support over time. Width and length not so much a problem as the drawers. You can stiff up the frame , but weight in the drawers is going to be a problem over time.

Ive done a lot of long trestle tables, but have all had solid skirts..
 
#15 ·
I don't think anyone mentioned a back panel? Even a 3/8" full back panel would resist any downward movement of the top if it's attached to the lower shelf.
I agree that a torsion box may not work with drawers spaced in between. It requires continuous sheets on the top and bottom for it's strength.
It's essentially a ''grid" of 3/4" thick strips glued together at 90 degrees and sheeted on the top and bottom with plywood or MDF from 1/2" to 3/4" thick.
This one is 10 ft long and 30" wide as an outfeed and assembly table:
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#16 ·
I agree that a torsion box may not work with drawers spaced in between. It requires continuous sheets on the top and bottom for it's strength.
It's essentially a ''grid" of 3/4" thick strips glued together at 90 degrees and sheeted on the top and bottom with plywood or MDF from 1/2" to 3/4" thick.
I suggest you try it as recommended before you make a conclusion. With thick (3/4") top and bottom skins, as long as they can be adequately separated it will work. You don't necessarily need the "grid" to be continuous. Thin skins require more continuous "grids" in order to maintain stiffness. Also, keep in mind that if the table top is also screwed to the top skin, it will provide additional stiffness.
 
#21 ·
What kind of wood are you planning to use for its construction. Some good grade cabinet hardwoods are plenty stable at 3/4" if supported about every 42" or less.
You need a much deeper skirt to adequately support the drawers and drawer contents, especially if they will be heavily loaded with metal tableware. This will also add stability and provide more anti-racking movement. Especially with the skirts tenoned into the legs. You might want to make the skirts 1.25"-- 1.5" thick, also.
Your flip out top idea will interfere with access to the drawers below being insufficiently deep enough to expose the contents, unless you are only opening the drawers with the table top folded up. You'll want to put dedicated drawer stops on the drawers so that they are not inadvertantley pulled all the way out of the table with the top flipped outward.The flip out top will also add a substantial amount of instability for a narrow long table.

Depending on how much room you need for storage on the lower shelf/stretcher The space between the bottom of the skirt below the drawers and the top of the bottom shelf/stretcher would possibly limit a deeper skirt idea.

A 1.5" thick top with another 3/4" flip out extension would be best, in my opinion, if you are determined to use a flip out top. Supporting it with several soss type hinges or longer mortised inlet chest or drop-leaf desk top support hinges would allow the front edges of the top to be somewhat self supporting. If instead you will want to use pull out sliders between the drawers, I would make them at least 1.5" in height set to catch the flipped out part of the top and spaced 30"--42" between the drawers. You will want the two boards on both sides of each drawer support to be the full height of the top and bottom 2.25" plus the drawer height.

You may want to add a 2.25" in the front skirt panel above the drawers giving easier access to the drawer opening and add an additional 2.25" in the skirt depth below the drawers. For this length of table stretcher for the shelf, I would make this in one continuous length with one or two cross supports and add another short skirt balancing the 2.25" upper design lines on the drawer skirt.

There are lots of ways to construct all of the joints. Look at several ways and decide what is best for you. Glue and screws, dowels, biscuits, mortise/tenon, sliding dovetails and dovetail drawer joints are all good ways to proceed. If you are using strictly softwoods such as cedars, pines etcetera you may want to be adding several glue blocks and table buttons.

I believe (like Johnip) that you will want to bolt the back skirt of the table to the wall so that you can have dancers on top of the table. It's not going to be stable otherwise. Its way top heavy, even if it was only 24" tall. I suspect your planning a height of somewhere between 34" and 44". It's a nice project and if you decide to dress up the design with moulded, tapered or intarsia inlays and bandings, it could be a real thing of beauty.