It's the tension my friend -- the tension.

I like the tension in the metal slats, but I don't understand the point of equal tension in both slats. Shouldn't all of the tension be on the outer slat? Isn't tension on the inner slat just pulling the wood away from the form? I understand that what is the inner slat at one stage, becomes the outer slat at the next, but wouldn't it be better to shift the tension when that happens?
I'd like to try to apply the heat to the inside of each bend. I could do that with heated cauls, or with separate, smaller, heating blankets. Am I being to cautious? Is this carrying the bending pipe analogy too far?
How sensitive is any bending machine to variations in side thickness? I'm thinking about the transition from inside cauls to outside cauls. With slats, and blankets, and wood, and paper, it seems like variations could add up to some faceting at the transition. Is this a problem?
Thanks all.

Both the Charis and the Way bender look pretty slick, but they seem a bit out of reach for the average guy. I don't know how to weld, attach hydraulics etc., and I imagine
most of us don't. Mind you, I ain't knocking those machines, but something of that complexity is not strictly necessary. You can do a perfectly good cutaway on the benders you can get from Blues Creek, so don't think that they won't do the job.

I would agree with you that there are many ways to bend wood. There is no reason that a simple bending pipe can't work and certainly a fox setup has been proven to work well. My reason for creating a better bending machine was trying to eliminate as many variables as possible. When developing the process I found that everyone had all sorts of different formula's for bending different types of woods. (ie amount of water, what to wrap the wood in, super soft, temperature, number of heating blankets, and the list goes on). What I found is that with a good tentioned slat it is easier to bend wood without needing all the "black magic". Working with Nelson Palen (who builds archtops) he found that bending curly maple to a 7/8 radius was a challange on this fox style bender and often had to thin his cutaway sides to ensure he would not have problems. I bent a series of samples (dry with no water) to a 7/8 radius using .095 and .110 thick curly maple pieces with no problems which is what convinced Nelson that the process want improved over the fox process. Here are some of the pictures from the tests...

Curly Maple Sample

7/8 Radius Bend...

.110 thick maple bent to a 7/8" radius.

Is the top edge of a side really flat? Even with a 28' radius?