Am I crazy, or is this design stupid? - Woodworking Talk - Woodworkers Forum
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post #1 of 10 Old 04-23-2019, 11:32 PM Thread Starter
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Am I crazy, or is this design stupid?

I'm refinishing a table for some friends. I took a leaf and turned it over to remove the skirt (or whatever it's called when it's just a strip of wood supporting a leaf), and I see...this.

This is just bad design, right? I mean, isn't it backwards? Shouldn't the fixed points be near the center, and the nice, movable clips be at the edges (you know, where the movement will actually be happening)? As it is, the z-clip isn't doing a thing right there in the middle, is it?

Am I crazy?
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post #2 of 10 Old 04-23-2019, 11:41 PM
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Quote:
Originally Posted by mackman View Post
I'm refinishing a table for some friends. I took a leaf and turned it over to remove the skirt (or whatever it's called when it's just a strip of wood supporting a leaf), and I see...this.

This is just bad design, right? I mean, isn't it backwards? Shouldn't the fixed points be near the center, and the nice, movable clips be at the edges (you know, where the movement will actually be happening)? As it is, the z-clip isn't doing a thing right there in the middle, is it?

Am I crazy?
Sorry but it's completely normal. Actually the skirt is just there for appearance. It's not at all uncommon for a leaf to have no skirt. With multiple leaves it's a lot easier to store if they are just flat boards.

The Z-clip is a table top fastener. The skirt for the leaf is probably run through the same machine as the skirt for the table. The table top fastener holds the skirt to the top in a way that allows the wood on the top to expand and contract with the weather. If a skirt is fastened too solid and the top shrinks it causes the top to split.
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post #3 of 10 Old 04-23-2019, 11:52 PM
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If the leaf is still in good condition then I guess it the design works in that case.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #4 of 10 Old 04-24-2019, 12:36 AM Thread Starter
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Originally Posted by Steve Neul View Post
Sorry but it's completely normal. Actually the skirt is just there for appearance. It's not at all uncommon for a leaf to have no skirt. With multiple leaves it's a lot easier to store if they are just flat boards.

The Z-clip is a table top fastener. The skirt for the leaf is probably run through the same machine as the skirt for the table. The table top fastener holds the skirt to the top in a way that allows the wood on the top to expand and contract with the weather. If a skirt is fastened too solid and the top shrinks it causes the top to split.
No, i get that, and I've made a ton of table tops with clips very similar.

But in this case, unless I'm very wrong, the clip can't allow the top to expand or contract, because it's in the middle (where there can't be any movement) while the outer edges of the piece are fixed in place by screwed and glued wedges. That means that the wedges, since they're at the edges, prevent the piece from expanding or contracting, while the clip does nothing. Right? Shouldn't it be the other way around: Screwed at the center, clips at the edges? As it is, the glue holding the wedges in place has completely failed, precisely because (I imagine) the wood had nowhere else to go and those wedges were the failure point.

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If the leaf is still in good condition then I guess it the design works in that case.
There is a crack developing on one side, but that could just be bad luck. And as I mention above, the glue holding the wedges in place has failed completely, meaning that the wood had nowhere else to go and that glue was the point of failure.
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post #5 of 10 Old 04-24-2019, 06:28 AM
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the clip
also resists against the leaf bowing upwards
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post #6 of 10 Old 04-24-2019, 09:12 AM
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No, i get that, and I've made a ton of table tops with clips very similar.

But in this case, unless I'm very wrong, the clip can't allow the top to expand or contract, because it's in the middle (where there can't be any movement) while the outer edges of the piece are fixed in place by screwed and glued wedges. That means that the wedges, since they're at the edges, prevent the piece from expanding or contracting, while the clip does nothing. Right? Shouldn't it be the other way around: Screwed at the center, clips at the edges? As it is, the glue holding the wedges in place has completely failed, precisely because (I imagine) the wood had nowhere else to go and those wedges were the failure point.



There is a crack developing on one side, but that could just be bad luck. And as I mention above, the glue holding the wedges in place has failed completely, meaning that the wood had nowhere else to go and that glue was the point of failure.
Technically you are correct however in reality it's very difficult to keep a skirt on a leaf like that when handling or shoving under a bed. If it didn't have the brackets on the ends the skirt would be broken off. It happens more than you think to get broken off anyway.

The only benefit of having the clip in the middle is if the leaf tried to cup warp the clip would help hold it against the skirt. Most of the time the skirts have pocket screws in the middle. It was probably easier for this manufacturer to use the table top fasteners.
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post #7 of 10 Old 04-24-2019, 09:32 AM
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After reading all the posts, I agree 100% with mackman (O.P.) unless the screw holes in the blocks are elongated slightly. The wood species and MC when built determines the expansion rate/contraction rate. Most dense hardwoods, like hard maple, dont move very much. I'm also guessing that the leaf is between 13" - 18" wide
The fact that the blocks moved enough to break the glue bond says something. Did the screws rip out of the holes?

If it were me, I would move the corner blocks inward an inch or two on both ends, enlarge the holes and put a washer on each screw and then set and glue in place. After the glue sets, i would back off the screws slightly.

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post #8 of 10 Old 04-24-2019, 10:13 AM
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Let me ask this, is the leaf solid wood or plywood? Most leaves like that are some kind of plywood and that wouldn't be affected by wood movement. Still even solid wood I would rather have the corner blocks glued and screwed than any other means of fastening. I've had to repair too many of those with the skirt broken off.
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post #9 of 10 Old 04-24-2019, 12:02 PM Thread Starter
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Originally Posted by Steve Neul View Post
Technically you are correct however in reality it's very difficult to keep a skirt on a leaf like that when handling or shoving under a bed. If it didn't have the brackets on the ends the skirt would be broken off. It happens more than you think to get broken off anyway.

The only benefit of having the clip in the middle is if the leaf tried to cup warp the clip would help hold it against the skirt. Most of the time the skirts have pocket screws in the middle. It was probably easier for this manufacturer to use the table top fasteners.
That makes sense. So the clip, in this case, is just because it's easier than putting in a pocket screw, and doesn't really accomplish anything special that a screw wouldn't do just as well?

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Originally Posted by Tony B View Post
After reading all the posts, I agree 100% with mackman (O.P.) unless the screw holes in the blocks are elongated slightly. The wood species and MC when built determines the expansion rate/contraction rate. Most dense hardwoods, like hard maple, dont move very much. I'm also guessing that the leaf is between 13" - 18" wide
The fact that the blocks moved enough to break the glue bond says something. Did the screws rip out of the holes?

If it were me, I would move the corner blocks inward an inch or two on both ends, enlarge the holes and put a washer on each screw and then set and glue in place. After the glue sets, i would back off the screws slightly.
The screws didn't rip out of the holes, or at least, not completely. But since they were only attached by 1 screw to the skirt and 1 screw to the top, it looks like the screw in the skirt served as a pivot point once the glue failed, allowing for most of the necessary movement.

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Let me ask this, is the leaf solid wood or plywood? Most leaves like that are some kind of plywood and that wouldn't be affected by wood movement. Still even solid wood I would rather have the corner blocks glued and screwed than any other means of fastening. I've had to repair too many of those with the skirt broken off.
Solid wood, for sure. But wouldn't it be better to have the blocks closer to each other, and then clips or figure 8 fasteners at the edges? Wouldn't that keep the skirt intact while still allowing for more movement?

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post #10 of 10 Old 04-24-2019, 02:27 PM
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Without knowing how the manufacturer is set up I can only guess the clip is an easier fastening system. It's the only scenario I can think of for going with that method.

The stress of the skirt is going to be on the ends. This is why the corner blocks are nearly always within a 1/2" of the edge. The table I'm sure is done the same way. On antique tables it's common to see the corner blocks at the ends of a skirt and have pocket screws all the way around from there. It does though present problems with wood movement. I inherited an oak table that someone got used in 1900. I got it in about 1980 in Illinois. The wood of the table was in perfect condition and I moved it to Texas. Within six months the top of the table split in 8 or 10 places due to the drier climate and the fact it had pocket screws about every 10" on the skirt. Had some kind of table top fasteners been used the top would not have split. The leaves on this table had no skirt so there was no issue there.

What I would recommend as an alternative to mounting the skirt to that leaf is to glue a 3/4"x 2" board with the blocks to the skirt and then drill some elongated mounting holes in the face of that strip to screw to the leaf. This would allow for wood movement while giving a strong structure to the skirt.
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