Just my opinion….
Book was written in 1845. Average height of a man in 1845 was 65″.
The book recommends 2′-8″ for bench height.
Therefore, 32″ + 2″(for plane) + 4-5″(average height today is 70″) = 38-39″ bench height for today.

I think there are a few reasons for shorter bench lengths. Only one person works at a bench today. In the past there would have been an apprentice. Available work space has become much smaller as well. I think most of us would build a 10-12′ bench if we had the space. What I see more of on here are people building there benches shorter than 5′ to fit there work space.

Bench tops thickness varied even in 1845. The French still were building there benches out of thick slabs, i.e. Roubo’. The book covers an American-English design. We have thicker tops today mostly due to the quality of wood available. In 1845 the wood was most likely much tighter grained. Resulting in heavier and stiffer lumber than we have now. So we build thicker to compensate for the quality of available lumber.

Forgot to mention…in 1845 it was a young man’s game. If I was 20 something years old the height of my bench would not be that critical. I’m welllll past that. So bench height quickly becomes a factor for my back. I’ll bet the average age on here is well past 40, so we are very susceptible to back strain. It sucks to get old.

Sam…
Was the wood they were using twice as dense? I don’t know. The wood they were using was from old growth trees though. That is why they were able to easily obtain 24″ wide boards on a regular basis. Most construction lumber today is from fast growing younger tress.

The weight also plays a factor. Our benches are shorter, so we need to increase the mass as well.

For most of us 2×4 lumber is readily available. A 2-1/2″ thick top might be all we need, but why go to all the effort to take the inch off when we need the mass anyway.

You can build a very nice bench with 1-1/2″ thick top but you will have to add more support to the under structure in order to compensate for the stiffness of you top.

One other possible reason for the lower bench hight back then was the fact that they where doing a lot more of the thicknessing and planing down from rough stock by hand, and if you are planing down all day, it is useful to be able to get over the top of the wood, especially for wide boards.

I’m not saying it’s not possible with a higher bench, I’ve flattened quite a few cupped or hollowed wide boards on my 42″ high bench (I’m 6’4″). It works fine, you just have to manoeuvre the board so you can get at it.

The other thing I’ve noticed is that, if you feel like it’s starting to be hard work and you can’t put enough pressure on from the top, it’s probably time to sharpen your plane (-: Paul always says that a sharp plane blade should almost pull itself down onto the wood.

I have and used for years bench’s that were 30 – 32″ in height. I have a bad back and had surgery as well and I don’t mind telling you working at that height crunched over kill’s me in a short time. I also used an older Drawing Table for my Blue Prints and that was killer also, I never learned auto cad and did everything by hand and still do.

Now since I have built Paul’s bench at the 38 1/2″ height I can work all day or until my feet tell me to sit without many issues. I am so glad I built this bench in lieu of the Nicholson which I was going to build.

Steve