Panel Saw Tensioning

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Isn't he saying, it doesn't make the saw stiffer?
(hammer) (hammer) (hammer) (hammer) (hammer) (hammer) (hammer)

Yes but I think he's also saying that it has an effect on the 'wobble'. So if it isn't stiffer it must mean that it alters the way the whole saw plate responds to vibration/ chatter - call it what you will.
I'm making a lot of this up. I'm not scientific enough to be able to understand or explain this stuff.
We clearly need an engineering solution to analyse this problem. I propose that we design a wobble-ometer to attach to the toe-end of saws in use. In order to do this, we need some funding, so we could apply for a research grant, asking for funds to analyse handsaw toe-end wobble with special reference to it's effect on climate change and it's contribution to world peace (because we could do with a bit of that round here) - we'd be bound to get extra cash if we phrase it that way. Then we could investigate the vibration of saws, maybe using different forms of damping to see whether tensioning was as effective as (say) putting a bucket of water under the toe-end of the saw, or sticking a lump of chewing-gum to the toe-end of the saw to stop it flapping around. Once the research information had been collated, the design and development programme for the wobble-ometer could go ahead, and manufacture arranged. With luck, the whole lot could be done to allow a release to market on 1st April 2017, allowing hand-tool users to check their saws for toe-end wobble.

Alternatively, we could do as Mignal suggested earlier; wait until Rob Streeper (or somebody else) has done a bit more work, then pass two otherwise identical saws, one tensioned and one not, to a few competent woodworkers and ask, "What do you reckon to these, chaps?"
I don't have any confidence that Rob Streeper is going to figure it out. I have had too many arguments with him about some saws being mid 60s hardness (which he believed to be true).

If you want to learn about tensioning saws, you have a small window of time to make friends with a japanese sawmaker who still scrapes and hammers saws by hand. Nobody else is doing it professionally, and they have been trained based on incremental improvement, not educated or uneducated guessing and hoping.
Just a semi-formed thought about what's happening.

Corneel's photos above show that when a 'tensioned' saw blade is flat, it is flat across it's width, but when bent into a slow curve, it starts to develop a couple of humps across the blade. Not very pronounced humps, but humps nonetheless.

A piece of flat sheet steel bends fairly readily. A piece of corrugated iron (made from the same thickness of steel as the flat piece) bends just as readily longitudinally, but not at all easily 'across the grain' of the corrugations.

The 'tensioned' saw blade when bent starts to develop humps like corrugated iron - so, the more it's bent, and the more pronounced the humps get, the less it likes it, and the keener it is to return to flat. Once it's flat again - no corrugations.

Not sure I've explained that very well, mainly because I haven't really worked out what's going on and why. However, it's a sort of 'working idea in progress' - thinking aloud, if you like.
Excuse me resurrecting such a long thread without reading every word of it again, but I think I have a new bit of information to add.
One of the many pleasures of attending Richard Arnold's charity do on Saturday was the chance to meet sawmaker Shane Skelton, try one of his saws, and hear him talk about how he makes his saws, which are both modern and thoroughly traditional at the same time. He may well be the only sawmaker in Britain who hand tensions his saws, by hammering with a sawmaker's hammer.

It's not just a gimmick, he has made a thorough study of old techniques and explored how to apply them to currently available steel. The panel saw he showed us is closely modelled on a surviving eighteenth century original in the Seaton Chest.

Shane described the effect of tensioning as making the saw stiffer without removing its ability to flex and spring back.

The saw in question did seem to have a magical ability to cut in a straight line, no matter whose hand was on the end of it.

You can read a bit more about it here - scroll down to find the 26" panel saw.
This looks familar, think I sent an email to them while trying to get more info on this. Never got a reply.

Was there any more detail on how the tensioing is performed?
He said he hammered a line along the whole length, about an inch back from the teeth. He also said that there was a lot of work to get the taper grinding right with the saw straight and free of blemishes (which it certainly was.)
Fortunately for those not able to be there, Jim was there with his phone on video mode and caught most of a long conversation between expert saw maker Shane Skelton and expert saw user Richard Maguire.
You can watch it here - go to about 7 minutes in for the discussion of tensioning.

(There's a bonus if you watch to the end - Shane's plausible explanation for the nib on a saw!)
I wish I could understand him! Especially in the part about tensioning, the sound quality isn't great, and that combined with the accent...
Cheap as chips Corneel. You could purchase the Skelton 26" Handsaw & the Skelton 26" Panel as a pair for the low price of (euro) $ 1113.20 + shipping. #-o
This is one of those rare instances where I would be inclined to buy a boutique tool. If I had the money. I think this is a rather special job, really worth something, and I can't make it myself.

Luckilly for a poor sod like me, there are still plenty of fine antique saws available.
I'd be inclined to try to make a saw like that for myself, but aside from that, I'd probably expect to get paid that were I making it and as is implied, it has the qualities that we are discussing about tensioning (staying centered well, stiffer , etc).

Of course, such performance is available in old saws readily found here in the states, they just generally aren't as pretty.

I always figured (keeping in mind that I have no interest in selling try planes), that were I to make try planes professionally (with a few more iterations), I would expect about $500-$550 for one with a double iron. I have never sold one for more than $100, though (the cost of materials). It is just the reality of making tools unsubsidized, to make something so nice, it will not be $150 (the saw, or a long plane like any of the current good makers are making).