Method of determining leak in end cap

[oldflutefan]

Please correct this if it is a damaging terrible idea. I'd hate to cause damage- but- thought others might find it useful. Or it may be a standard already.

My end cap had a suspected leak (sustained suck test, probably stopped sealing after a few seconds, hard to tell.)
So I applied a very small amount of washing-up liquid around the metal-to wood joint area, and did a 'blow' test instead. The resulting bubbles showed me I did have a leak, and where it was, too.

I don't think significant amounts of the stuff would get in.

[LorenzoFlute]

You can use your spit.

[kkrell]

I don't think it matters at all if the end cap leaks, but sounds as if your head cork is leaking.

[James_Alto]

Can't you use one of the flexible light rods to see in the dark if it is leaking?

[Aanvil]

I don't think it matters at all if the end cap leaks, but sounds as if your head cork is leaking.

^^^This is exactly what is happening.

[Jon C.]

Suck test is the best approach. Remove head from barrel, seal end of male slide on palm, crest a vacuum by sucking on the emb hole, see if it holds or leaks. You can put some cork grease on the cork to help it seal better...

[LorenzoFlute]

Jon, I find it easier to cover the embouchure hole with a finger and suck from the end of the slide... Once cleaned of course.

[Maihcol]

One thing I find helps to narrow down a leak specifically to the headjoint cork, is to separate the head from the barrel - and take out the endcap. Then place the palm of the left hand over the top end (where the endcap goes), place the palm of the right hand over the slide end and suck through the embouchure hole, so that the lips get pulled in a bit, creating a seal. The fingers of the right hand can be curled inwards to hold the head. This should give a perfect seal - or else there is a leak between the head and the slide tube, or a crack in the wood.

After about 10 seconds, remove the left hand from the end and note whether it comes away without any feeling of "suction" or vacuum from that end. If you feel something, that's most likely due to a leaking cork.

Garry

[jemtheflute]

Jon, I find it easier to cover the embouchure hole with a finger and suck from the end of the slide... Once cleaned of course.

I was going to write that..... Oh, and to eliminate the rare but possible chance there's a leak at the embouchure between liner tube and wooden tube rather than a stopper leak, it is sensible to remove the crown (but leave the cork in place) and suck at the crown end too to see if the cork is airtight that way.

The washing up liquid or spit won't hurt anything and can be helpful in determining visually exactly where any leak is. It doesn't matter a damn if the crown cap seals, even if it is the kind held in place with lapping rather than on an adjuster screw. It's the stopper cork that is crucial.

[oldflutefan]

Ha! Thank you-
Tried the double-ended suck test, for leaky cork, and after 10 seconds (with quite a strong vacuum) removed the crown hand- definite vacuum there, and the barrel-end vacuum immediately became much stronger...
This cork sanding hoohah is proving rather tricky. I can't find a piece of metal rod with 16mm inside diameter, to do a plastic cork- at least I know the bore is cylindrical, and exactly 16.2 mm, as borrowed internal calipers from neibour, to go with the digital vernier we have.
So, online I can get delrin rod at 16mm- might try that.
The best result I've got from the cork trials so far is a nearly airtight one, made so by dipping a too small-effort repeatedly (on a needle) in a melted mixture of paraffin and beeswax.
Then inserting in while wax still slightly warm. If I'd got the cork (a rather ratty bit )properly round, this might have given a perfect seal- has anyone else tried this?
There are no cracks in the wood- a suck test with nothing in was perfect.

[Denny]

you can use the tenon string technique to tighten up a too loose cork

[Maihcol]

If the cork is almost making a seal, you could try swelling it over a flame. A gas flame will do as long as you keep the cork from scorching - you only want to get the cork hot enough, so that it absorbs some of that grease and swells. You can put a needle in one end of it and rotate it between finger and thumb, above the flame while making sure not to burn the cork. If you see the outside of the cork go dry, add more grease.

If that doesn't do it, you could try wrapping the cork with plumbers tape. Pushing that into the cylindrical bore of the head might then encourage the shape of the cork to become rounder again, if it's not too far off already. Thread might do it too, as Denny suggests.

Or try another cork.

Ordering delrin rod to make a stopper doesn't sound like a good idea, as it would be expensive and you'd still need a piece of sheet cork on the outside to make a seal - and also to allow the wood to move without cracking.

Garry

[oldflutefan]

OOops.
Thanks, Maihcol.
I did wonder about the completely solid nature of the delrin, and movement, and cracks. That Bigio stopper looks as if it's designed for a flute with tuning slide. I have to pull out the head (can get it down from A445 to A440- think it's at Society of Arts pitch).
I won't do the delrin- off now to play with corks, grease and flame.
Oh- I made some cork grease yesterday, having used up the small amount of Dolmetsch grease left from a recorder I don't have time (or that much inclination) to play.
Used, in the end, 3:1 vaseline:beeswax. More beeswax seems to make it too hard and cleggy, tho' for thread, more might be good-

If anyone wants lots of vaseline- we have a few ponds of pharm grade stuff in some drums bought for storing biodeisil. Anyone using huge amounts very welcome, for postage price!
UK.