Heat blankets: What do you do?

[Kerry Krishna]

 I was looking over LMI's site and saw both the pretty darn expensive blankets ($65 up to $180 I think)  plus the heat regulator and thermometer being another $150 (?) bucks. Man, this is just so expensive!

 Are there other heat blanket options? Is it possible to make them ourselves, and the heat regulator too, or a cheaper option? 

[J R Emmett]

There was an excellent thread authored by Robbie Collins on building a temperature controller a few months back:

 

http://fretsnet.ning.com/forum/topics/diy-temperature-controller-fo...

 

You can also use a varo-stat to control the heater but this option runs open loop and you will need to profile heater temperature with respect to settings using (preferably) a digital thermometer.  It would be best to permanently attach a thermocouple to the heater blanket (using a self adhesive type) and continuously monitor temperature.  Most modern DVM's have a temperature monitoring feature.  I used to work with a technician that did advanced materials research using this technique due to the fact that once set - the temperature is rock stable (unlike a digital controller that will vary slightly).

 

With respect to heater blankets, you might benchmark the prices for the various parts you will need from the following sources:

 

http://www.mcmaster.com/#heat-sheets/=pmzu3v

http://www.omega.com/

http://watlow.com/contactus/salesloc_submit.cfm

 

Watlow is a manufacturer so they should have the best prices. 

 

A few cautions:

 

1.  Attempt building your own controller only if you have the necessary skills to work on AC circuits (a mistake is potentially fatal).

2.  You need a temperature sensor (thermocouple, RTD, etc) to sense the heater temperature directly (i.e. in contact) to prevent damage to the instrument and (potentially) fire. If the sensor is not in contact, the heater will just run to maximum temperature.

3.  If you design and/or build your own heater controller, make sure that it is designed for safe operation.  As a minimum, have someone (Electrical Engineer, Electrician) look over your design and construction work.

4.  Never run a heat source unattended (Yes, I am the guy that unplugs his soldering iron when he steps away from the bench).  I have an aversion to fire... unless it is burning under a nice steak .

5.  You will need to protect yourself from burns.  Always measure a surface temperature before touching it.

 

Part of what you are paying for from LM is a solution that has already been Engineered for safe operation, customer support and something that is tailored for your application.  That being said, I like building my own tools  :-).  Hope this helps.

[Robbie Collins]

Well said!

Add Benchmark to the list of blanket manufacturers. Their contact person is Tina Carmona :

[e-mail]

[Ernest Kleinman]

I get my heating blankets from omega or watlow, and the heat controller for smaller  blankets is a cheap router speed controller rated to 15 amps.RTR speed control from harbor freight , paid $15.

[Steve G]

How much did you pay for the blankets?

[Ernest Kleinman]

 Shop around  all the listed mfr./s sizes and prices vary .I bought mine  years ago. Size the blanket  for it./s intended use. Safety first.

[J R Emmett]

Ernest, that is a very creative lost cost solution.  Most router controllers are SCR based which effectively regulate what portion of the AC voltage is supplied over time.  Here's a pretty good description of how they work:

 

http://www.mcgoff-bethune.com/manufact/cci/technical/SCR-Guide.PDF

 

Please note that SCR's usually fail as a short, which will result in continuous full power application to the heater.   My previous comments about continuous temperature monitoring and unattended apply.

 

I am not criticizing the approach one bit (in fact, I am going to look for my old router speed control to try this out) - just communicating the safety concerns so that it can be used safely!

 

[nathan clark]

I have the older LMI timer/temp control, a bridge removal blanket and bridge plate removal blanket.  The bridge plate removal blanket is great but the bridge blanket is smaller than I would like for belly bridges.  Consequently, I still use a heat lamp for some reglues.  I've never bothered buying the fretboard tongue blanket for fretboard extensions although I've been meaning to.

[Mark A. Kane]

 I have Watlow strips and regulate them with a dimmer switch. Works fine. Having said that, I use a heat lamp for most removal jobs. It's what I'm used to, so I don't reach for the heater very often. I made up a bunch of guitar-specific heat shields/reflectors from heavy cardboard wrapped in heavy aluminum foil. Some have specific bridge shaped cutouts in them (Martin, Taylor, etc.) The heat goes where I want it, plus I have direct visual cues in addition to a pyrometer to tell me how hot the surface is. The blanket hides the visual, and I really want to see whats going on. 

[Hesh Breakstone]

Great post JR!!!  Very well said.

Kerry I'm not sure what you want the heat blankets for but the only thing that I use mine for is bending acoustic guitar sides.  Although the rig is a bit pricy so too is a highly figured set of "The Tree" so for me it was actually cheap insurance, cheaper than replacing exotic wood sides that is.

For repair work I'm with Mark and most of our removal of exterior stuff, i.e. bridges, fret board extensions, etc. we use a 250 watt heat lamp and custom fitted, cardboard shields covered in heavy foil.  Any exposed cracks are taped up with that metallic tape used for duct work, not duct tape, the metal stuff.

If your application is for a large blanket for side bending when I was looking around for mine John Hall at Blues Creek guitars (he has a web site) had the best prices and my blanket and controller have served me very well with no issues.

[Ernest Kleinman]

 JR  emmett  FYI  I only use the router on my 1 1/4in by 18in  omega blanket , as it does not draw  too  many  amps  it climbs to 250 F  vy slowly I set the router speed control to 150  deg F  and place my bridge on the blanket in preperation for using   315 test hide glue. I  put  glue  the bridge and  the top and clamp quickly as it sets up in 1 minute cleanup with soda straws and hot water. I have an oven thermostat $20  that regulates  the temp.

[J R Emmett]

Very nice and thank you for the complete description of your system!