Bowed long boards - any remedy?

[tibi]

Hi,

I have cut boards to length (and approximate width) for the bed I am working on. The issue is that some boards are too bowed. I need 7 long boards (5x190 cm and 2x 225 cm). When I put a straightedge next to the board, there are 0.5 - 1.5 cm gaps in the middle, when both ends touch the straightedge. If I were to plane it down from 32 mm thickness, my boards would be very thin. Is the only feasible option to look for other straighter boards and use those bowed boards for other projects, where shorter length will be required, thus making the bow less pronounced. Is there any other option, like clamp it against a straight face for some time, steam, etc?

Thank you.

 

[Jacob]

Won't the structure hold them straight enough when you've put it all together?

The procedure for planing is to start with the longest pieces you need on your cutting list, and select them from the shortest possible pieces of straight enough stock. Then work down the list to smallest/shortest.
Maybe you need to improve your planing technique?

 

[TRITON]

Will the internal thin section slats that the mattress sits on not pull them straight ?

 

[tibi]

Won't the structure hold them straight enough when you've put it all together?

The procedure for planing is to start with the longest pieces you need on your cutting list, and select them from the shortest possible pieces of straight enough stock.
Maybe you need to improve your planing technique?

Hi Jacob, maybe it will hold. That was one my ideas as well. But I was afraid that it would be under constant stress and something would crack in the future, especially when the bed will be under load (during the night).

Also it would be quite bad to cut tenons and find out that the board did not straighten enough. I will see how straight are other boards that I have in the lot.

 

[tibi]

Will the internal thin section slats that the mattress sits on not pull them straight ?

It might pull two long side boards, but other 5 boards cannot be pulled this way . 1 board is for the footboard and 4 for the headboard.

 

[TRITON]

It might pull two long side boards, but other 5 boards cannot be pulled this way . 1 board is for the footboard and 4 for the headboard.

For the 4, maybe a loose tongue or even biscuits between each board, and each board reversed so one pulls against the other.

 

[tibi]

For the 4, maybe a loose tongue or even biscuits between each board, and each board reversed so one pulls against the other.

I cannot use loose tongue or biscuites, as the boards will not be edge glued together. This is my design

 

[Jones]

That's fairly straight. The construction should hold it straight in position. You can lean a board against a wall at an angle and it will bend over time which might straighten them , you'll need to overbend it to end up straight so clamping to a straight edge won't work. With such a small bend adding water or steam will probably cause more problems.

 

[Droogs]

Have the central slat and the 2 runners fit into dovetails when assembling the bed and they will pull it straight. Does mean you have to have a beefy supporting lip all the way round

 

[Inspector]

You could glue a strip on the back of each board (so it looks like -| ) in the headboard to straighten it and it wouldn't be visible unless you jamb your head against the wall. Try taking the worst of the bowed boards and clamp a 30mm wide strip to it and see how much it straightens. If it takes out some then you could plane the edge of the strip to intentionally crown it like a clamping caul until it takes out all of it and a bit more.

Pete

 

[profchris]

Inspector's strip could go on the inside. You'd screw the slats to it along the sides. At head and foot you'd have to work out how to integrate it with the two longitudinal braces - I'd probably simply rebate the longitudinal member at its top and screw/bolt it upwards to the strip, that should be strong enough, but I'm sure there are cunning joints which would be even better!

 

[Ttrees]

I think it maybe worth having a go at clamping the splayed ends of a pair in the same state,
having the concave on the outside and introduce some moisture in the centre
and leave for a bit.
Can't see how its not worth a shot if you've got plenty of clamps, presuming that the timber can be persuaded flat in the first place with reasonable pressure?

 

[Doug71]

I wouldn't worry about it too much until you have tried planing it. Sometimes you only need to plane off a small amount and it can change the stresses within the wood totally changing it's shape, a straight piece can become bent, a bent piece can become straight (or unfortunately even more bent!).

 

[Jameshow]

For the headboard you could put a board across the back of them holding them together??

 

[--Tom--]

15mm isn’t much over 2 metres, with that design there will be ways to firm it up as people have suggested. If the level of bowing matches then a slight curve to the headboard could be part of the design and stop it being so rectilinear

 

[Orraloon]

For the long side rails i dont think its a problem. If you can push the bends together by hand on the benchtop it should go in the bed frame OK. Place the bends towards the center of the bed and the support slats will push them into line. Like that. )-(. Anything that pulls into line with reasonable hand force will hold in place when attached to a structure.
With the headboard cross slats nice strait ones would be best as that will show if they are not all in the same plane.
Regards
John

 

[Adam W.]

Hi,

I have cut boards to length (and approximate width) for the bed I am working on. The issue is that some boards are too bowed. I need 7 long boards (5x190 cm and 2x 225 cm). When I put a straightedge next to the board, there are 0.5 - 1.5 cm gaps in the middle, when both ends touch the straightedge. If I were to plane it down from 32 mm thickness, my boards would be very thin. Is the only feasible option to look for other straighter boards and use those bowed boards for other projects, where shorter length will be required, thus making the bow less pronounced. Is there any other option, like clamp it against a straight face for some time, steam, etc?

Thank you.

View attachment 137225

View attachment 137226View attachment 137227

What part of the bed is it that we are looking at in the pictures ?

 

[Stevekane]

I think your only problem is the headboard, the three slats need to be parallel to each other even if all three have a curve, how about a small narrow piece screwed across the three at the rear middle, just to hold then square to each other, or taken a stage further, let into the rear so that its just say 10mm back from the front edge and holding the gap between the boards constant too,,btw I liked the ref to it all being “under load at night”
Conjures up all sort of goings on,,,,isnt it enough just to be able lay down gently on it?
Steve.

 

[Sgian Dubh]

What part of the bed is it that we are looking at in the pictures ?

Adam, he's concerned about the four boards required for the headboard and the board between the legs at the footboard, five in total.

A possible solution for the footboard end is to flatten the board as best he can, which might leave it somewhat bowed, but of consistent thickness throughout its length. Then he could glue and screw a roughly 60 X ~20 mm piece on to the inside face to straighten the footboard rail: effectively this piece would become one of the mattress supporting slats. The same strategy could be employed for the lowest rail between the headboard legs. That takes care of two boards out of five.

This leaves three rails above the lowest headboard rail. In this case they're mostly going to be hidden by the mattress and pillows anyway. Overall I'd say tibi might be getting overly concerned about being able to get a usable thickness for these three parts after flattening because he's starting with 32 mm thick stuff and I suspect he'd have enough stiffness even if he had to end up with boards that are only 18 - 20 mm thick. Even with this thickness the rear face of these three boards sit back from the rear face of the headboard legs, and if stiffening and/or straightening is required a similar stiffening piece of suitable width, i.e., not protruding beyond the rear face of the headboard legs, could be glued and screwed to the rear face of each board.

I think tibi may be somewhat anxiously anticipating difficulties that may just disappear once he gets the basic machining for true and square completed. Slainte.

PS. Edit. I forgot to mention he's also concerned about the two side rails. Straightening these, if required could be accomplished much as above with a return (bearer) glued and screwed to the inside face upon which the slats sit, as seen below where the side rails are ~20 mm thick. Also a judicious screw or two at the end of a couple of slats where/if the side rails bow outwards would also serve to straighten them. I did something similar with this bed where the slats are stapled to a couple of hessian strips. The slats come in two halves, one at the headboard end stretching to the side rail to almost the mid-point, and the second set roll out again almost to the mid-point from the footboard end. The last slat at both ends of each set slip over a stop screwed to the bearer and it's at the mid point where a screw goes through a slat into the bearer below.

 

[Fitzroy]

I find this an interesting conversation as I reflect I have had similar issues when building bits of furniture. As a novice woodworked self 'trained' from youtube it is these kinds of issues that cause me hours of thinking time, as I've no reference point for what will be ok and what won't be ok. My concern is always about wasting timber or making a part that then does not fit correctly.

On my workbench I am laminating up boards for the Roubo top (yes i owe my WIP a big update). In theory each board does not need to be perfectly straight as when I glue them up I can clamp out any bow, they only need to be uniform thickness. However the boards had significant twist and I couldn't workout how to get out the twist without using the surface planer, which would also take out the bow and hence I'd loose thickness. I'm sure a more experienced woodworker would know the answer / be confident in just thicknessing the boards and then worrying about dealing with the twist/bow during the joinery phase.

As a beginner this is why this forum is great, it gives us some confidence to crack on with a certain route without having prior experience of the issue,