How can I make a water trap?

I've long been very frustrated by the moisture problems in the band and finally have found a way to resolve it...

In my opinion, the GHB has a design flaw. The blowstick should NEVER have been aimed at the chanter reed. This causes the air stream from your mouth, which is highly humidified and contains some "particulate water" (i.e. spit) to impinge directly on the reed. This results in a soaking wet chanter reed - which then goes flat or soft or "wonky".

Many attempts have been made to resolve this problem. Most simple "cup" traps try to knock out some of the spit. My feeling is that they are two small/short to do any real good. Other designs using tubes to carry the air to the back of the pipe have the right idea. The long tube will allow the spit to settle out of the air stream. (I commonly see spit about 12" back in my tube, thus validating my statement that the cup type traps are too short.) By bringing air out the back of the bag, it will also equilibrate with the temperature at the walls of the bag and will be dehumidified which is great for winter! A third design based on desiccants might have advantages, but these are arguable and, in practice, I haven't really found reduction of water on the reeds as compared to the simple tube trap.

Various approaches have been taken to use tubes. The main problem is that tubes stuck through the blowstick stock tend to kink. I've considered using corrugated tubing, but it whistles (i.e. it turns out that this is a version of an instrument called a corrugahorn!) and I want more diameter than are generally provided so that i would have less restriction to air flow.

There are designs that get past the size problem with a concentric set of tubes in the stock. One I've seen allows the inner tube to be slid out.  However, It can kink - and it's expensive - and it probably doesn't exactly match your stocks..

I've been using a very permanent mondo-mega sized tube trap for several years and have had NO moisture problems. However, I've had to severely modify my blowstick stock to use this approach. I bored out the bottom of the stock and threaded it to receive a right angle plastic fitting threaded into the bottom of the blowstick stock. (I had a machinist friend do a second set for me because it was so nerve-wracking to do it the first time!) A large diameter tube is attached. The tube extends to the back of the bag where it is capped with another plastic fitting. About four inches from the end, the tube has several holes cut into it facing into the bag so that any spit will remain in the tube, but allow the air out. The holes are placed to allow the spit to be caught in the end of the tube when the bag is deflated and at rest.

To "drain" the trap, you remove the blowstick and flip the bag upside down. It's pretty grotesque in operation, but it works!

With a new set of Dunbars, I ordered their tube trap. The 1/2" id tubing was too small - spit went through because the air velocity was too high and the tube kinked, so it was the worst of both worlds.

I looked carefully at my design, which works but which was difficult to implement and the Dunbar design which didn't work but was pretty simple. I realized that there was a middle ground.

I now have a scaled down version of a slightly less mondo-mega water trap in the Dunbars. It consists of a 1/2" NPT to 3/4" tube right angle nylon fitting threaded into the bottom of the blowstick stock, about two and a half feet of 3/4" vinyl tubing (I bought three feet and cut to length), a 1/2" NPT nylon cap stuck in the end of the tubing and holes as described above. All sharp or rough edges and molding imperfections in the nylon bits were sanded off. The threads were cut using a 1/2" NPT tap stuck in my lathe and the blowstick stock was hand held during the cutting (i.e., pretty gentle process!). The amount of blowstick stock material removed is small - about 2 grams (maybe 1/2 a teaspoon.)

(If you do this in wood, use a layer of teflon tape between the wood and the nylon threads to prevent any remote chance of binding.)

Experimentally, the spit doesn't make it much more than half way down the tube before settling out. (slightly smaller diameter of tubing compared to my other set, slightly higher velocity of air, settling distance slightly increased, but still kept in the tube!)

After doing this, the blowstick will permanently angle back toward your mouth. It feels natural to me, but may not be right for everyone. The other added advantage of this trap, as many of you know, is that it can provide valuable rigidity to the Canmore bag.

So...That's what it is and how to do it.  

Since the original design, I've made a few modifications: 

  1. I've come to realize that the tube trap may be longer than necessary, so recently I've been making them as short as 20". 
  2. Also, over time, the tubing may begin to rotate on the barb fitting and you'll end up with a very awkward bit sticking out in all the wrong directions.  To overcome this, I now drill a small hole on the "inside" of the elbow through the tubing into the barb fitting and put in a short stainless steel screw.  It keeps the tubing from rotating, is a lot less bulky than a hose clamp and has no sharp edges.


Copyright S.K. MacLeod 1996-2016