Relief from strangulation?

[Terry McGee]

OK, so I cracked first. I just couldn't contain myself until MTGuru comes back from holidays to unlock the previous thread. Lots of new findings and observations on the flute thread wrapping to report, including the possibility of reversing at least some of the damage, see:

http://www.mcgee-flutes.com/effects_of_ ... apping.htm

MTGuru, should we continue to discuss them here, or wait till you reopen the older thread?

Whatever, let's leave the highly contentious question of calculating forces until one or other of the professionals reports back.

Terry

[Nanohedron]

MTGuru is having to field an array of stuff at the moment, so allow me to stand in and suggest that we all hold off for a wee bit.

[Casey Burns]

Terry, I just read your writeup. Certainly there is evidence of bore compression on some historical flutes but still lacking in your data are such factors as how these flutes were handled and cared for (impossible to determine), the original bore shape, and something that could be measured which would be the wall thickness of the tenon on the strangled historical examples. My theory is that this last factor is the key - that thin walled tenons are perhaps at risk to this bore compression.

To really test this one should set up an experiment with different types of woods, and different wall thicknesses for each, based on real world examples (I remeasured my tenons and these are all greater than 2mm in wall thickness for instance - I also see no evidence of compression in my flutes, including the occasional old one in for servicing). A set should be made with corresponding sockets, left on. A dry set and a cycling set (wet and dry) would also be helpful. Finally, a similar set of the above wrapped in cork and with sockets applied would be fair, in case its the socket itself bearing on the thread wrapping material (cork or thread) causing the compressions.

Then based on the results of these tests, one could perhaps make some statements about the effect of thread wrapping of tenons on bore compression. Until then, your conclusions are only true for a boxwood tenon with a substandard 1mm wall thickness. I agree that a tenon that thin would deform under pressure, especially when wetted. However, I think its unfair to imply that all thread wrapped tenons are a bad thing from this one experiment.

As to the math and the forces applied, this is irrelevant, and not worth getting bogged down with. Direct measurements instead.

I might go ahead and set up this experiment properly as described above and see what results I get (though with boxwood and blackwood only - I don't "do" cocus). It will probably have to wait a few months as my schedule simply won't allow it until then!

Casey

[hans]

I imagine that thread material is also an important factor and should be taken account for in tests. Man-made fibres like polyester and nylon have some elasticity, whereas a natural fibre like cotton has very little. A test on a polyester sewing thread showed me that it stretches 1% of length for every 1N tension force (1N=1Newton, ca. 100g weight force), whereas a cotton thread only stretched 0.2% for every 1N increase, a fifth of the polyester thread. It suggests that a cotton thread will resist any wood expansion much more than a polyester thread.

And it may be wise to test for the effects of thread tension as well, with wraps using normal or low tension compared to high tension wraps.

[I.D.10-t]

Did not BXhm find a better solution?

[Julia Delaney]

There are lots of ways to screw up a flute. Wrapping a tenon too tightly with thread is one way. Another way is to wrap the tenon with cork that is so fat that it cracks the socket at some point in time. Sockets can crack despite the ring, which is supposed to strengthen the socket.
It is obvious to me, at any rate, that the fault is with neither the thread nor the cork, but with the person who is applying either. I have seen many more flutes with cracked sockets than with strangled tenons. Fancy graphs and “scientific studies” can’t include –- or account for -- user error.

[Denny]

so...

what is obvious to the non oblivious
is not obvious to the oblivious, eh

hmm

[benhall.1]

I'm disappointed. This thread has been going for hours now, and we still have less than 10 pages.

[Rob Sharer]

There are lots of ways to screw up a flute. Wrapping a tenon too tightly with thread is one way. Another way is to wrap the tenon with cork that is so fat that it cracks the socket at some point in time. Sockets can crack despite the ring, which is supposed to strengthen the socket.
It is obvious to me, at any rate, that the fault is with neither the thread nor the cork, but with the person who is applying either. I have seen many more flutes with cracked sockets than with strangled tenons. Fancy graphs and “scientific studies” can’t include –- or account for -- user error.

This is spot on.


Rob

[jemtheflute]

Initially I observed Nanohedron's exhortation to be patient.... but as we're running with this (and sensibly, so far) I think it appropriate to publish (slightly edited) thoughts I sent to Terry as a private e-mail having read his latest additions to his web-page. I think they are germane to Casey's proposal here in particular, especially as Terry intimated he won't for now be spending any more practical time on this.

Hi Terry,
I've just re-read your web-page including the new observations.... fascinating stuff. Without in any way doubting your observations and most of your extrapolations from them, I think there is one very important, if maybe unlikely aspect you have not covered, and could easily do so as a control in the same time frame as the work you have already done. It seems to me possible that a tenon cut like your test one or like the thinner walled historic ones most prone to waisting/"collapse" (I'm not sure, in view of your latest observations of recovery, that that is the best term!) might just possibly exhibit at least some of the same tendencies without any lapping on it whatever. It could be at least partially a function of the way the wood is cut - the very thin tube walls at the lapping trough, the thicker rings at tip and shoulder, - and how they react as a system in the climatic/use cycle. I'm not saying I think this is likely, just possible, and ought therefore to be accounted for in any experiment if only to eliminate it. Look at your own expressed surprise at the swelling end - which may well (probably IMO) have nothing whatever to do with the lapping!

Can I suggest you make a pair of identical (so near as timber allows) tenons and repeat your experiment with the two in parallel, one thread-lapped, the other left naked? Or better still, do a triple set and include a corked one for the sake of it! You can't reuse the first one for obvious reasons and running it with just a new bare one, even though you can redo the regime pretty closely, isn't as objective as you can easily be by running two or three together, plus a rerun with a different lapped one will reinforce your conclusions from the first in all likelihood.

Beyond that, I agree that a full investigative programme would be too big and time-consuming a job (particularly if it tried to take account of the stuff I wrote about thread in the original discussion!) But I don't think you can really satisfy your own curiosity, let alone possible objections, without the control naked one at least, and preferably the corked one too.

[Nanohedron]

Initially I observed Nanohedron's exhortation to be patient....

Ah, you're a peach, Jem. A peach, and I'll bet you understood that "a wee bit" was a euphemism for holding off until MTG had his say - for indeed, he was the moderator invoked here.

Hmm. What was I, then...? Paramoderator, I suppose. Odd place to be in...

[benhall.1]

Interesting message of yours to Terry, Jem. Exactly what I proposed on the other, locked, thread.

[jemtheflute]

Interesting message of yours to Terry, Jem. Exactly what I proposed on the other, locked, thread.

"Exactly"? I won't deny influence, though..... even if my own thoughts had already tended that way and you beat me to expressing that particular point at that time. Quite a few valid points/questions raised in the original thread never got picked up on, perhaps due to the distractions going on!

[benhall.1]

Yep. Exactly. Identical. Literally the same.

[Terry McGee]

And as I responded to Jem....

Heh heh, tempting, Jem, but I really have to let this one go. As I mentioned, I'm not accepting any orders at this time in order to deal with my backlog. But instead of dealing with my backlog, I'm spending days on this experiment. Argghhh! Have I no self control at all? Answer, clearly not, but I'd better get some! With a bit of luck, Casey might have a go at some of this - it's more his territory anyway!

I am seriously thinking that it would be good if someone (me, if necessary) now did a real live test with a full LH piece, tapered bore carefully measured, tenons at both ends wrapped, and subjected to the humidity cycling I used. It might take many months to get a result, but it might help us reinterpret our measurements of old flutes.

Terry