Bridge or boat?

[peter-harrison]

Whoever taught me to use a planer/thicknesser (it's so long ago that I've forgotten who it was!) said that you should sight along that board you are about to surface to tell which way it's bowed, and then to turn it so that is like a bridge, and to pass it over the surfacer until the two planed surfaces meet in the middle.
I have done it this way for most of the last 35 years, but lately when I had a huge pile of tulipwood that had to be as straight as it possibly could be, I had a change of mind and did them boat- fashion, surfacing from the middle until the planed surface got to the ends.
Mechanically this seems better, as bridge- wise, especially with long and not very thick boards, the middle can sag when the board is being planed, leading to a non-straight surface. Boat fashion, the sag happens outwards and I don't think it has the same effect.
This may have some or all of you saying, "what an idiot to do it wrong for 35 years", or maybe you are of the bridge persuasion and think that age has turned my brain to putty.
Any comments?

 

[Amplidyne]

It does mean that with the "boat" method the middle being planed first you don't have to remove every bit of rough if you have any leeway on length.
Really though I've done it both ways and always found it easier "bridge" style.

 

[Inspector]

I was taught the bridge method and prefer it but I can boat if the mood strikes. Whatever works for you.

Pete

 

[Fitzroy]

I tend to take the bridge approach most often but will go the boat route if I am trying to do something specific, like manage board thickness, or twist or some grain issue. I will also often plane only one end of the bridge is I have variable thickness in a board.

 

[Beau]

I've always tended to do it concave side down but get what your saying about planing a curve into the board.

 

[Cabinetman]

I prefer Bridge- concave side down, the other way seems out of control and difficult to hold “level”.

 

[HOJ]

I do it both ways, depending on how bent or twisted the board is, did today on 12 Oak planks, purely to get the stock clean for stickering and stabilising.

I'm sure our resident expert will be along soon!

 

[niall Y]

If you do it boat fashion you can easily plane a flat on the bulge that isn't in line with the two ends. Rectifying this mistake could easily lead to loosing too much from the thickness.
Doing it bridge fashion, you are gradually reducing from both ends to eventually meet in the middle, which I believe is a more efficient method.

 

[Doug71]

Both ways depending on what I'm dealing with, I actually often do both on the same piece of wood as I find it keeps any stress in the wood more balanced. If you take material off both ends of a piece over the planer to get it nice and straight sometimes when you come to thickness it and take material off just the middle of the other side it can cause it to bend again.

The whole straightening bent boards thing is why I think for me the planer is probably the most dangerous machine in the workshop. With both the table saw and spindle moulder you are normally just pushing a straight piece of wood through but with the planer I'm constantly flipping wood over or turning it round end to end and also applying downward force at different points. I do try to have the guard properly in place but it does get in the way at times..........

 

[Sideways]

Bridge.
I think "boat" is too prone to error but I'm no purist and would combine the two if I thought it would help.

 

[RobNichols]

I'm relatively new to planer/thinknessers and am currently migrating to thinknesser+sledge/thicknesser, but for what it's worth I think what's important is which is the most stable starting orientation.

In most of the boards I've flattened, they are most stable initially in the bridge (convex up) orientation. It's usually easy to keep them steady. In boat (convex down) mode they rock and are therefore more difficult to keep steady. What you're trying to avoid is having the board change orientation as it travels through the planer after all.

That said I am sure there are instances where the nature of the twist is such that a board is initially more stable convex down.

So I tend to get the board on my bench (or other flat reference surface) and see if it rocks. Then flip it over and see if it rocks less on the other side. Then use the side that rocks least as the starting reference.

 

[niall Y]

One doesn't have to slavishly remove all evidence of the sawn surface when surface planing long lengths of wood.There comes a point when the board is flat enough to pass through the thicknesser without rocking.
My technique from this moment is to take equal amounts off both sides, so the wood remains more stable and to this end I number each pass with a pencil to keep track.

 

[peter-harrison]

I get what people say about the timber rocking when it's boat fashion. To try to avoid that I would put all the pressure, in the first couple of passes, at the low point.
If it's appearing that you are going to end up taking more off one end than the other, you can either stop the pass before you get to the end of the planed surface, if the back end is too thin, or place the board on the planer with a bit of planed surface resting on the outfeed table, if the front end is too thin. Do this as many times as is needed to rectify it.
Some of you may say that this is dangerous. I've been doing it for years without a problem- but I am always very careful- IE don't drop it on, and don't be taking too big a cut when you do it.