Bow Tolerance in a Apron

[Brandon Lemen]

Long time lurker, first time poster here. These forums are such a useful resource and I appreciate the input from all directions.

I've been woodworking at the house for the last 3 years or so and have slowly accumulated enough stuff to entertain a legitimate project request from the wife which is a slender, minimalist-ish hall table in walnut. The top will be 12.75" x 60" and will sit on haunched mortise and tenoned aprons. After cutting up the long aprons, (51ish" x 1.5" x 3/4" LWT) one of them developed a 5/32" bow. I was wondering if this much of a bow will compromise the table in any way, or if this is just a normal hurdle when building larger projects. I plan on having cross pieces between the long aprons joined with sliding dovetails which should keep the aprons parallel.

I'm attempting to add a pic of the table I made in Fusion if it provides any assistance in answering the question. As a disclaimer, this design is modified and completely influenced from a table we found from Domenic Fiorello Studio.

Table.JPG
Thank you,
Brandon

[Stan Calow]

Brandon, no expert here, but I've had that happen recently, and one consequence was that the tenons on the end of the apron were not 90º to the legs. I think it was a bit less of a bow than you have.

[Frederick Skelly]

Welcome to SMC Brandon - glad you've joined us!

Personally, I think that much bow will be a problem on a relatively delicate table like that. You didn't say what kind of wood you are using. If it is inexpensive material (like poplar), I'd make that part again from scratch. If it's more expensive material (like walnut), I'd at least try to save the part.

I'm brainstorming here. You will be attaching the top to the apron, right? This might be worth a try to save the part, if your design allows it. 1) Clamp the apron bow-down to a flat surface. That straightens it for the next step. 2) Mill/buy a board that is something like 1" x 1" and runs the length of your apron, minus tenons, etc. 3) Glue the 1 x 1" to the inside of the apron, so that you create a L-shape in cross section. I would align the 1x1 with the same edge of the apron that the top will sit on. You could add several screws down the length of it if you want to further strengthen the part. 4) Let everything dry thoroughly, unclamp and see if the 1x1 was enough to hold it straight.

I'm not certain this will pull out that much bow, but it might be worth a try before you throw away an expensive part. Home Depot sells 1 1/4" square poplar that you could use for that 1x1. But again, my first choice would be to remake the part, especially if this is cheaper material.

Let us know what you decide to do and how the table comes out. We like pictures, too!
Fred

[Phil Mueller]

Given the center cross piece(s), I wouldn’t worry one bit about a 5/32” bow over a ~50” length. It won’t compromise the table in any way.

[glenn bradley]

With that design you could also add an unseen piece midway to help physically correct the deviation if you wanted to.

dummy-1.jpg

It's semantics to some degree but, to help clarify terms.

bow-crook-cup-twist.JPG

Much as we use "dado" when we mean "groove". As long as we get the message across, we're good.

[Brandon Lemen]

Thank you for all the responses. Hidden in the OP, I mentioned it will be made of walnut. I plan on securing the top to the aprons and underside cross pieces with buttons. Part of me wants to just move forward and see what happens as part of a learning process, but I do have another piece of walnut that I could mill up. Then I would just use the bowed piece to cut into the shorter aprons so it wouldn't be a complete wash.

Glenn, I already planned on having at least 2 perpendicular pieces on the underside secured to the aprons with sliding dovetails.

Frederick, great idea for the supporting piece. I'll have to store that in the memory bank for the future. For now, I'll prob just move forward as is or mill a whole new piece.

Brandon

[Robert Engel]

I'm pretty sure you're talking about a bow as in the face of the board curves.

Standing a board on edge, a bow becomes evident. Looking at the face of a board a dip could be called a bow but some call it a wane.

In an apron the first is not big problem, the latter might be a huge one.

[Gary Ragatz]

Glenn, I already planned on having at least 2 perpendicular pieces on the underside secured to the aprons with sliding dovetails.

With this, I can't imagine that a 5/32" bow is going to cause you any trouble.

[Brandon Lemen]

I'm pretty sure you're talking about a bow as in the face of the board curves.

Standing a board on edge, a bow becomes evident. Looking at the face of a board a dip could be called a bow but some call it a wane.

In an apron the first is not big problem, the latter might be a huge one.

It's been my understanding that a curve along a face is a bow and a curve along an edge is a crook. Yeah that would definitely make a huge difference. In this case, it is a curve along a face...the better of the two situations here.

[Brian Tymchak]

With this, I can't imagine that a 5/32" bow is going to cause you any trouble.

Welcome to the Creek Brandon!

I agree with Gary. As long as you clamp the board straight when you cut joinery, the dovetails will pull the board straight. 1/8" ish bow over 51" is really not that much distortion and 3/4" thick stock is pretty flexible. If you still have a choice orient the board so that the dovetails pull the bow in.

[Frederick Skelly]

Brandon,
I'm embarrassed to admit this, but I just realized I made a simple math error and gave you bad advice. I read "5/32" at least 4 times - it was clearly stated. But in my head, it registered as 5/16 - nearly 3/8 of an inch.

I agree this shouldn't be an issue.

My apologies.
Fred

[Brandon Lemen]

Great, thanks for all the responses. They've given me reassurance that this amount of bow shouldn't be a huge issue with the cross pieces. I'll press forward and see what happens.

Brandon,
I'm embarrassed to admit this, but I just realized I made a simple math error and gave you bad advice. I read "5/32" at least 4 times - it was clearly stated. But in my head, it registered as 5/16 - nearly 3/8 of an inch.

I agree this shouldn't be an issue.

My apologies.
Fred

No worries, I do the same thing in my head and screw up plywood cut lists every time. Fractional measurements are such a recipe for disaster.

[Brandon Lemen]

Just to follow up, I finished this piece about a year ago and the sliding dovetails to lock in a and eliminate any apron bow worked great. I attached some pics of the joinery, carcass and table in it's final home.

Thanks
IMG-2214.jpgIMG-2221.jpgIMG-2348.jpgIMG-2345.jpg

[Kris Cook]

Looks nice. Well done.

[Lee Schierer]

Nicely done.