Now my blasted pipes are gurgling @#$^$%^

Maybe its the humidity. I've noticed my smokes to be steamier Lately here in Boston...

Good thought Tom, but these pipes never gurgled before (or very seldom at least) regardless of how humid it was when I smoked them.  A couple of things lend to this (I think):

1:  I keep my pipes in a dehumidified cellar - they always dry out completely before coming back up in the rotation.  Basically they're overly dry compared to most folks' pipes.

2:  Nearly every tobacco I smoke is intentionally on the dry side.  I've found that nearly every tobacco tastes better to me when I let them dry out a bit (ok, quite a bit!).

So ... nope, don't think its a humidity problem either with the pipe or with the tobacco.  As far as the only other variable in the equation (the environment), well, they were dry smokers for years and now just after cleaning them they gurgle ... its too obvious ...

Rick Piatt

I also caught another thread.  It also has occured to me that possible the cake being freshly cut itself is causing the problem of the additional turbulence if it is rough.  That being the case it would just need some additional tars deposited to take those rough spots out and the pipes should be right back to peak performance.  

Fume in pace, ckr

of great interest to me.  I had never made a pipe stem and had bought transparent acrylic in order to see how the drills worked effectively, how the flutes filled with shaved material and could heat and melt the walls and actually seize the bit.  It was also to be able to see how to clear the slot and form the funnel.  Now that I have bored you with this how and why discourse in stem making I can get on back topic. 

Since the stem was transparent I also got to observe what is occurring that produces the dreaded gurgle.  We all know how pipe smoking enhances the power of the human mind so I puffed along and what I saw was actually very interesting.  For the first 20 minutes the smoke just traveled up the stem, it would enter advance, sit and advance with my puffing.  After 30 minutes there were very small moisture deposits forming on the stem walls.  These were very tiny, barely pin pricks but noticeable because of their tobacco color.  As I continued to smoke they continued to grow in size and after 45 minutes they grew in mass, very similar to beads of sweat forming on your brow.  Eventually they got to where their weight was enough that they would run down the walls, some would collide with others forming bigger beads of fluid.  Within another ten minutes they had collected enough mass and run (likely down to where I could not see them into the shank) and a dreaded gurgle reared its ugly head and ruined my smoking pleasure.  I refrained from using a cleaner and let the process continue eventually leading to a good amount of liquid flowing into the stummel and starting the sizzle effect.  The sizzle effect being the sound of a steak on a hot platter. 

Anyway, there is this guy named Nick that posts on PipeMakersForum.com that is into all this fluid dynamics stuff and with his help I was able to understand the cause of what I was seeing.  It involves the smoke that comes in contact with the outer walls of the stem encountering resistance, it advances more slowly than the smoke in the center of the airways.  So actually the stream of smoke traveling up the airway is layered and the layers furthest away from the walls are advancing at the highest velocity.  The smoke closest to the walls meets with the most resistance which causes eddies to form on that layer and the eddies disturb the adjacent layer which also forms eddies but further up the stem thus creating what is known as turbulence. Expansion and compression that cause changes in the pressure also come into play, which is why a gap in the mortise tenon area often becomes a moisture collection point.

So here is my best guess, you say you drilled out your shanks.  Where I imagine you took a drill bit the same size and by hand turned it while advancing it all the way to the stummel.  The operation is allowing a greater volume of smoke to enter the stem so it would reason that the smoke stream is under greater pressure which should increase the amount of turbulence in the smoke stream and it is depositing an increased amount of moisture on the inner walls.  A second cause might be something occurred in the shank, a deep scratch or gouge, a smaller drill that did not take all of it out, not really sure but something that is altering the airflow in a way that is causing additional turbulence early on in the stream and disrupting the normal advance up the airway.

Then again, who the hell knows for sure. But I thought I would offer my two cents.

Fume in pace, ckr

You made my eyes roll back in my head on that one ... more detail than I can handle this early in the morning!  Yes, you're right I did use the drill by hand and am sure nothing but tar was removed.  I'm sure I didn't scratch the inside of the air passage in any way (I'd have felt it if I did) and likewise I'm sure there is no residue down there because I swabbed out the air passage after drilling by:

1:  scouring it with one of those bristle brushes dipped in everclear very thoroughly.

2:  ran through numerous thick pipe cleaners like wise dipped in everclear until they came out white (or close to white anyway).

3:  ran through a couple of thin pipe cleaners that I spun around a lot to be sure I got all the moisture out - and then sat them in a rack to dry.

No, the only change has been the removal of the tar at the last 3/16" of the air passage.  That Bjarne had quite a big build up as did a couple of others.  Like I said, they draw wonderfully now but they (a few, not all) do tend to gurgle somewhat.  I'm sure ... positive ... hopeful ... please God ... that once the tar starts to build back up the gurgling will go away ... but I'm not a happy camper about it!

Rick Piatt

long winded.  It sounds as though they just need a few smokes to get back into the swing of things.

Fume in pace, ckr

This is interesting you've mentioned eddies and turbulence. Some estimates were made for the Reynold number and it turns out that in order to have turbulence in a stem the pipe should be sucked as crazy (I do not remember numbers, of course, I forgot them at the instant they hit my ears). It never occured to me, however, that the pipe could be smoked with a transparent stem and the actual pictures could be taken. This would be great!

Misha

However, here are a few links

http://www.naspc.org/airflow.htm

http://hyperphysics.phy-astr.gsu.edu/hbase/pfric.html

Pipe makers try lots of things to make the air flow as laminar as possible but turbulence is there and it is to what degree that will determine how quickly moisture forms.   Smoothing out the edge of the airway in the stummel, non removable stem drilled while on the stummel, shotgun stems, twin bore’s and then the other side of the coin stingers, chambers and sumps the list is likely longer than I am aware of.

Regarding pictures.  I had thought of that at the time, place the pipe on a clock take a shot and repeat every ten minutes.  I should have done it then.  The particular stem is so blackened with tar it would not do so well.  Additionally, it was only a two inch stem.  So preferably, I would like a long stem on a short shank.  I have a 1/8 bent pot that would make a good candidate.  Do not expect a quality stem.  On the other hand I have a prince that needs a stem so I will kill two birds with one stone. Nah, the pot holds more tobacco, so it will be the former.

Fume in pace, ckr

This is actually complicate issue. Turbulence is a specific phenomena that is often mixed with sound. A stem can whistle but there might be not turbulence whatsoever. Just to give a feeling for typical numbers, in order to approach turbulence in a standard stem one should breath through stem while walking (say, around, 3 mph). People rarely smoke at such rate.

In turn, sound alone is not so crucial for condensation. While back I've participated in a research related to propagation of sound (roughly) in the air near dew point. It was expected, in particular, that sound would be absorbed more effectively because of facilitated condensation. The effect was not pronounced, meaning that sound per se does not cause a lot of condensations.

The points where sound forms, however, have that typical feature that the lines of flow strongly diverge behind them. One could expect enhanced condensation at these points merely because of this effect. Principally, this could even be relevant for Rick's experience and I am almost sure that this stands behind the engineering solutions you've described.

The physics here is very complex. For example, opening the smoke channel from 4/32 to 5/32 halves the flow resistance. It might be the explanation for positive opening effect or might be not. By the way, the condition of turbulence formation relaxes with increasing the radius of the channel, so from this perspective opened pipes should smoke wetter, which is not the case as experience shows. This may serve as an additional illustration of why turbulence might be not the prevailing factor in pipe smoking.

[On the side note. This is really inconvenient that there are no e-mail notifications for responses in threads other than in my own blog.]

Misha

It might be simpler than what ckr has written.

If, at the bottom of the bowl where the airway enters it, a small dish is formed from the opening of the airway back up, this will create a place for moisture to collect instead of spreading out and going up through the bowl as steam.  If this is the case, it'll clear up with time, or a dremel (or even sandpaper) could be used to carefully round off the sharp edges. 

Joel
http://www.jspipes.c...

I guess the tar build up at the bottom of the air passage happens fairly quickly because most of the pipes that were gurgling are now behaving much better (after less than 6 smokes each).  Typically they now gurgle a tiny bit after about 2 minutes of smoking - I swab out the moisture with a pipe cleaner and then I'm pretty dry for the rest of the bowl.  Thats more like it!  One is back to its old perfection where it just never needs a pipe cleaner at all - love that!  Oddly enough that pipe is one that was misdrilled when I bought it and I took some jeweler's files and modified the air passage.  Obviously I enlarged the drilled hole, but I also rounded out the bottom of the passage (its a bent pipe) so a pipe cleaner would pass through easier.  I guess I did a good thing!

Rick Piatt