Reelfoot tone channel slope experiment

[Henry H]

I've been experimenting a bit the last few days with the impact of tonechannel slope on performance of reelfoot calls, and though I'd share as this may help someone... or provide a place for others to share their experience and learnings.

The initial setup is a reelfoot insert with a flat (no slope) 1/4" tone channel.  The reed was held constant for this experiment, to isolate the impact of changes to the tone channel.

Baseline - flat tone channel (full depth)
Tuning the reed was a challenge, and I was never able to achieve the full range I would normally want.  At a low pressure quack, I had to tune the reed to a very low somewhat flat pitch to get any high pressure performance - but when applying pressure in a hail or highball, pitch was way too high and squealy.

Test 1 - approximate slope by using modeling clay in the tone channel
Little by little, I added modeling clay into the forward end of the tone channel and used a 1/4" dowel to shape it into a gradual slope from the bottom of the original channel.  Even with just a small bit of clay sloping to about halfway back towards the wedge, sound performance imoroved with slightly higher pitched quacks and noticeably less squeal at pressure.  I continued adding clay and slope until I had a fairly consistent slope from roughly the front of the wedge to the forward end of the tone channel.  At the forward end of the tone channel, depth from top of clay to tone board was about 1/16".  At this point, the call was performing best, with a pretty good range and handling high pressure well without lockup or squeal.

My hypothesis at this point was that slope was a critical factor to getting top performance and range out of a reelfoot call... but the possibility existed that the improvement resulted not from slope but simply from the smaller volume capacity tone channel, so I needed to try to test for that, too.

Test 2 - Same amount of clay, but flat (no slope)
To test volume displacement without slope impact, I simply respread the clay from Test 1 flatly along the bottom of the tone channel, from tip of the channel to the back of the wedge.  In other words, Test 2 should have had the same tone channel volume capacity as Test 2 (and less than baseline), but no slope.  While this setup performed better than baseline, it clearly had less range than Test 1 and got squealy again with pressure.

My conclusion is that slope is indeed important to getting a full range, highly performing reelfoot.  I've included links below to soundfiles so you can hear the differences in the setups yourself, as well as a pic of the tone channel with the clay slope.  A couple footnotes are in order.  First, the soft clay certainly has a different impact on sound than wood, so a similarly sloped wood tone channel would certainly sound different than these files.  I wasnt going for perfect sound, rather just trying to test relative sound from different setups.  Second is a reminder that the reed was held constant in these sound files.  Tweaks to curve, shape, thickness, etc. may have made any of the 3 setups better (or worse).

I hope this helps others, and hope others will add to these observations with their own.

Baseline
https://www.dropbox.com/s/as8ap16ui2fktsn/reelfoot-flatTC.m4a

Test 1
https://www.dropbox.com/s/5gpk9pfc06rdxo7/reelfoot-clayslope.m4a

Test 2
https://www.dropbox.com/s/8dfn15pjokqyvxa/reelfoot-clayflat.m4a

[ben]

Interesting.

ben

[FDR]

Interesting as Ben said.  I wonder if the depth of the tone channel under the tip of the reed is just as important as the slope.  I have some old inserts where the tone channel is much  too deep.  I might just see.

Fred

[Waylon at JWT Custom Game Calls]

Thanks Henry. Great info, and will be a lot of help. I've got a question, maybe you or Fred or anybody else could answer. I've been thinking on this since our conversation the other night. What if you drilled your tone channel straight, then tapered your Toneboards a little. Thicker at the wedge end, thinner at the end of the Toneboards. Still have a flat Toneboards, but it would have a slope to it giving you a sloped tone channel. Maybe not work, wanted your guys thoughts in it. Thanks. Waylon.

[Henry H]

Sounds like another experiment, Waylon!  That would certainly mirror a sloped tone channel... I guess the question would be whether sloping the toneboard towards the mouth of the call would create adverse (or beneficial) impact since air flow to it would be from a different angle.  You'd also have to make sure your wedge angle matches.

[FDR]

Unless the tone board slope is excessive I think you will end up with too much depth under the tip of the reed but then again I have not tried it....yet.  As Henry said sounds like another idea/experiment.

Fred

[FDR]

I spent a little time in the shop this morning and conducted a "feasibility" study just to see if I thought the idea might work.
1.--I assumed that a 1/4 inch hole is drilled, on insert center. to the proper end point for the tone channel.
2.--I assumed that I would need 0.050" depth at the reed tip.  For that to happen I would have to cut the tone board 0.075" below center, at the reed tip. 
3.--Since I mill the tone board the wedge angle is not an issue using my setup.
4.--The tip geometry bothers me a little.  The 0.050" remaining would be in the form of the drill bit tip not the sphere segment that I now use.
5.--The tone channel might be a little shallow under the wedge but that is easy to correct.
6.--My biggest problem would be holding the insert to cut it below center. I now cut my tone boards using a fixture that requires a full diameter insert to properly fit into my jig.  I ruined an insert yesterday because I had turned the insert undersize enough that it popped up into the cutter. The shop became real exciting for a few milliseconds!

It looks like it might work out for you guys that have different tooling.  Can't wait to see how the experiments turn out.

Fred