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I’ve tried laminating sides; it works well but is time consuming. I’ve used the bending iron method which is faster but less accurate. So I’m building a side bender right now and figuring out what heater and controller to get , so this thread is perfect timing for me.

I use their blanket, but avoided their controllers, as some posts indicated problems.
They offered different types, but I put my own together (thread link above) and it works pretty good, +/- 0.5 degree.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

My Keenovo heating blanket works well but I have one gripe about it. The temperature on the controller (which seems fairly accurate) is adjusted by Up and Down buttons. To change the temp you have to hold the button as it slowly scrolls through the temps by .1 increments. Forget about making quick temp changes. Takes for-freeking-ever to go from 300'F to 250'F. I've gotten into the habit of just cutting the power (I use an outlet controlled by both a switch and a mechanical timer) and waiting a couple minutes to get it cooled down, the switching it back on and changing the temp setting. If you hit the "set" button before you shut it off it'll save the setting and restart there so you can take it down in increments if you have the patience.

Maybe I'm just being stupid and there's a much easier way to operate this thing. Does anybody know a better way?

I built a couple controllers and I later saw the LMII model and was surprised at the basic similarities. I think a timer is a very important safety element wouldn't have one without it.

Mine cost more to make than the LMII model but in addition to the timer it is overbuilt. I like being able to turn off the heating circuit and still use the PID to monitor temperature.

I never had the temp accuracy some of you are reporting. My initial heat cycle pours so many watts to the blanket (5w/sq in) that even with the thermocouple between wood and blanket it tends to overshoot the temp setting by 20-30 degrees F. The blanket is hotter than the wood so even when the controller shuts it off, it still takes some time for the blanket to give up it's heat to the wood causing the overshoot. Once the wood heats up the temperature stabilizes.

The PID controls temp by turning the blanket on/off. I've only bent about 10 sets of sides but the heat ramp seemed way to fast for me. It seemed like a lot of heat to dump into one side of the wood so quickly.

When my blanket burns up I'll look for a lower watt replacement.

I had a temp controller for a wood burner rated for something like 1500w. It works in a similar manner by turning the power to the device on/off more or less often depending on where the dial is set (1-10). So I plugged that into my controller and the blanket into that just to crudely simulate a lower watt blanket. I found the whole bending process to be much less stressful and the addition of just a couple minutes to the process seemed to give the wood enough time to heat more evenly and thoroughly. The temp overshoot of the first heat cycle was also reduced. I think a lower watt blanket will be even better when the time comes to buy a new one.

Just thought I'd add my experience and observations. Pic of my home brew controller below. Bottom left red switch turns on control circuit the one to the right of it turns on/off the heating circuit. The LED to the right of the PID just indicates when the PID is sending juice to the blanket. The rotary timer limits how long the heat cycle can run.

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Brian R, Wood Mechanic
N8ZED

Although home built, my controller is virtually identical to the LMII unit (see my posted tutorial). While bending, I also use two additional K-type thermocouples plugged into my multi-meter. A misplaced probe can certainly give a bad reading, so I like the redundancy of having three. At the same time, I like the precision control made easy by the programmable PID. I also put a timer on the output to the blanket.
Lots of ways to control a blanket. A builder-friend who’s built several hundred instruments still uses a simple on-off switch and a parallel light bulb to indicate power going to the blanket. When you’ve built that many guitars, your senses give you all the feedback needed.


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John Hall at Blues Creek Guitars. I’ve had
My blanket going on 15 years.


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Well, I've been snowed in a lot lately and decided it was time to put those temperature controller parts I've been sitting on together into something useful. I'm pretty impressed with it--it's holding temperature within about a 2 or 3 degree range. Plenty good. The total cost including was about $50. I have an external timer I plug into the controller.

The PID I had bought years ago (a REX C100) turned out to be a bogus ripoff and didn't work. Beware the eBay! I bought an "Inkbird" PID from Amazon for about $25, and it works great. 5 K type thermocouples cost $15. I already had a Solid State Relay. Simple project and seems to work great. I'll use it next time I'm bending some sides. I never moved the meat thermometer I have been using once the bending process began, so putting the thermocouple in the same place (near the waist on the lower bout) and leaving it doesn't worry me.

Dave

Bogus parts on eBay - don't get me started. If you think you're getting a bargain, likely NOT.

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Steve Smith
"Music is what feelings sound like"

I'm very happy with having my temp controller integrated with my bender instead of having another unit to store and handle. Unscrew 2 screws and the wooded face panel comes off exposing all the electrical components without the need of a metal box. Here are some pics.

- You can see the model number of the controller in the picture, Google it for the mfg. name, and still find it cheaply for sale on ebay. It holds the temp within a couple of degrees F.

- The timer beside it a safety. The blanket can never be left on (forgotten) for longer than 17 minutes so I can't burn the house down.

- The "white" wire plugged in the box is a thermocouple. It can be easily be quickly unplugged and then a second one plugged in to give you two temperatures in two different locations. An the choice of where to control the blanket temp.

- There is only one 120V cord (white color into the box end) to plug in which powers everything including the heating blanket. The blanket cord (black cord into the box end) is plugged inside the unit so that it can't get in the way of anything. (There is no need to unplug the blanket. The chord end is anchored to the bending unit so it doesn't float around. The 3 slats of spring steel are also fixed and don't float around.)

- There is one lighted master switch which turns everything on or off.

- There is one lighted blanket switch which turns the blanket on or off. Normally when bending this switch is turned on so the blanket can operate based on the the controller turning it on and off. If this switch is turned off, then the blanket will not turn on even when the controller is "telling" it to turn on. This is handy so that you can leave everything powered and monitor temps with the controller or set the controller set temperature without the blanket coming on. A quick flip of a switch is easier than plugging and unplugging a blanket.












The guitar side shape comes off the top of the bender/controller box" so any shape can be put on top of the "box". This is MUCH smaller than a Fox style bender and offers much more support and control of the wood when bending to avoid breaking sides.

Is it just me that can't see the images?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

What I’ve noticed in using mine a few times now is that the temp will initially shoot past the set temp by about 20 degrees, and after some temperature surfing it holds within a few degrees. It doesn’t seem to be an issue in any practical sense, but have any of you experienced anything similar?


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When I first powered mine up, it overshot by about 7 or 8 degrees and then calmed down. After I performed the "Auto Tune" routine, it only overshoots by a couple of degrees on startup.

Dave

Somewhat off topic but Ed I notice you do the same as me - lock the steel slats at on end then tension both at the other thus providing support for inside and outside bends. An awful lot tidier than my setup! This is very necessary for me when bending quite tight cutaways s I do. Cheers Dave

Dave,
Yes, I agree that the tensioned slats offer much more bending support and faster heat transfer than the Fox/floating slat approach.

I bend cutaways in mine without a problem. My caul which pulls in the cutaway is the same as yours.

My bender pulls/tensions the slats down vertically while yours pulls/tensions the slats out horizontally.

I have 3 steel slats while you have 2. My order sequence from bottom to top is:
1 wooden form
2 steel slat (aluminum foil covered)
3 wood to be bent
4 steel slat (aluminum foil covered)
5 heating blanket
6 steel slat (aluminum foil covered)


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When I attended Charles Fox's school in Vermont back in the 70's, I was introduced to the new Fox bender. Charles tensioned the slats on his machine via leather cords that fastened to steel rods attached at each end of the top slat. These cords then were pulled tight and fastened to cleats on the ends of the bender, pulling down like Ed is doing. The bending shoes were pulled down after that.

I still do mine that way, I guess mainly because that's the way I've always done it. It's always worked well for me. Takes a bit more work when you're building the bender to put the rods in the end of the outer slat, but no biggie. I guess that we've come a long way since the lightbulbs on the originals, but the Fox bender is still one of the more ingenious machines for guitar making that I've seen.

Dave

Yes, this correct. The controller needs to be calibrated with an “Auto Tune” cycle whenever a different blanket (load) is used.


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Charles Fox has contributed much to the art and science of guitar building and I have great respect for him. As you said, things continue to evolve and improve.

I didn't come up with the basic design of my bender, Mike Doolin did. However I improved his slightly by having the blanket cord exit the rear big bout insteasd of a cumbersome front exit which was constantly an obstruction. Plus a few other small improvements.

All 3 steel slats are individually tensioned with multiple springs on the end of each slat. This forces a tight sandwich of blanket and wood during bending together steel support on both sides of the wood being bent.

Since the wood is registered and clamped down I can cut the wood to exact length prior to bending. There is no need to try and line up a floating stack of sharp edged steel and wood and blanket with a waist line mark that may be hard to see and align.

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Very cool Ed!

Dave

Thanks! I'm going to have to look up how to do that with an Auber Instruments PID.

It’s documented (in smallish print) in the Auber pdf manual, and you can also find the Auber method demonstrated in the video by Robbie O for the LMI controller.


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Sure couldn't be any easier than that. Thanks for the reference, Tim.

I finally got around to buying a temperature controller and and a timer for my side bender. Unfortunately, there wasn’t much info that came with either unit. Does any one have a wiring diagram for using these two units in a side bender context?

I googled "TET612 wiring diagram images" and came up with a few in the results.
Pick your chose, and you'll need probably a suitable relay/heat sink.
For the timer, similar results may be got from the net, it should go on the supply side, to the controller I believe.
https://www.aliexpress.com/item/32792163504.html
or if you prefer Chinese,
Like https://www.newbecca.com/product/556631538191
Please check the specs are suitable, voltage, power rating, etc., BUT
If in doubt at all, consult an electrician.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.