heating blanket questions (& other questions about bendi

[bernm]

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"Originally Posted on: Wed Jun 23, 2010 3:03 pm"




Hello everyone. I have some questions about heating blankets. Apologies in advance for a long post!

First of all, you might be wondering why I had a question about planes a week ago, and now heating blankets. The reason is that I built my first guitar through an intensive at Thomas Lloyd's a few months back (very happy with the result for a first guitar). And now I'm filling in the gaps in my own workshop so that I'll have the basics at home to keep building. I'm 'researching' my options for some of the tools and equipment, so that I buy wisely.

So thanks in advance to anyone who answers. Hopefully one day I'll have a lot more experience and be able to offer advise rather that just keep requesting it !!!

On to my heating blanket question ...

Okay, I need to figure out how I'm going to bend sides. I was all set to build a side bending unit using globes until I realised that high-wattage incandescent (the old-school) globes are getting harder to buy, with energy-savers taking over.

So I'm wondering about heating blankets. I'm very confused. I know I don't want to buy an overseas model and couple that with a transformer. I know there are options like MEI and LMI.

I actually looked into this about a year ago and read a 2008 post on this forum about blankets, and then looked up MEI and emailed for a quote and received no reply. Recently I contacted LMI and asked about their international 220V model. They were very quick and courteous in their reply, but said that because they do not sell a temperature controller for the 220V model, they do not recommend me buying that one, but instead suggested that I buy the 120V and their voltage step-down transformer. This just seems like an awkward and overly expensive way of doing things.

So here are my jumble of questions:

(1) Do I need a temperature controller / thermocouple? What about just switching the unit on/off? If I did that, would I need a surface thermometer?

(2) If I bought the 220V blanket from LMI, are there Australian suppliers who sell an appropriate controller? What price range do these things go for?

(3) It seems to me from reading on this forum that MEI is the preferred source for blankets. I found the request for a quote form on their website very confusing, e.g. phase, grounding layers, etc. If I was to ask them again for another quote, can someone please spell out quite simply what would be needed? I'm just not familiar with these things at all, the types of connectors, etc.

(4) Now to make it more complicated. I want to build both guitars and ukuleles. Would I need to buy 2 blankets, or could I buy a guitar-sized blanket and use it for both? In theory, couldn't I just build a bender for each, just with the curvature different, but using the same blanket? But does this mean that the need to control temperatures is even more critical, given the smaller dimensions of ukulele timber as compared with overall blanket size?

(5) If I can't sort this, I may just buy an electric bending iron. At this point it seems a lot less complicated?! But, I guess I should ask as well: to those who have used both the iron and side-bending units, which do you prefer and why?

(6) In all of this, finances are a factor, especially since I'm at the point of buying a number of tools at once.

Thanks for persevering in reading this long post !!! Again, thanks in advance for any help for a confused novice.


Regards
Bern

[Kim]

bernm wrote:


(1) Do I need a temperature controller / thermocouple? What about just switching the unit on/off? If I did that, would I need a surface thermometer?

No, a thermometer will do and you can just listen for the sizzle and watch for the wood to relax before you start the bend.

bernm wrote:
(2) If I bought the 220V blanket from LMI, are there Australian suppliers who sell an appropriate controller? What price range do these things go for?

No, not for a comparable price but with research you can make your own. The fact remains that you simply do not NEED a themocouple and PID or even a thermometer with a heat blanket. It just depends how fancy you want to get.

bernm wrote:
(3) It seems to me from reading on this forum that MEI is the preferred source for blankets. I found the request for a quote form on their website very confusing, e.g. phase, grounding layers, etc. If I was to ask them again for another quote, can someone please spell out quite simply what would be needed? I'm just not familiar with these things at all, the types of connectors, etc.

You just want a 240v, single phase, 36" x 6" blanket Bern, if you do not want to use a PID (digital temp controller) then skip the thermocouple, if you do then go for a "J" or a "K" type. PLENTY of guitars have been built without a thermocouple and even if you change your mind later and decide that you do want to use a PID, then you can use a thermocouple externally on the blanket rather than in the blanket.

FYI: A thermocouple is no more than two conductors of dissimilar metals such as one of iron and the other of nickle alloy. When joined together they make a current, when the temp changes, so does the strength of the current and that is all that the PID reads, it does not care if it is in or on the blanket.

bernm wrote:
(4) Now to make it more complicated. I want to build both guitars and ukuleles. Would I need to buy 2 blankets, or could I buy a guitar-sized blanket and use it for both? In theory, couldn't I just build a bender for each, just with the curvature different, but using the same blanket? But does this mean that the need to control temperatures is even more critical, given the smaller dimensions of ukulele timber as compared with overall blanket size?

You could but you are better with two blankets, one for gits and the other for ukes.

bernm wrote:
(5) If I can't sort this, I may just buy an electric bending iron. At this point it seems a lot less complicated?! But, I guess I should ask as well: to those who have used both the iron and side-bending units, which do you prefer and why?

I would recommend that you get both a blanket and an iron for touch-up work. You can get by with a bending iron but a blanket set up properly offers better scope for success especially with well figured or temperamental woods.

bernm wrote:
(6) In all of this, finances are a factor, especially since I'm at the point of buying a number of tools at once.

Suck it up princess Very Happy

Bern it does cost a bit to set up, it's just one of those nasty things about good stuff, but ongoing's aint too bad so you just gotta live with it. You can save here and there but there are also plenty of false economies to catch you out so your best bet is to read the archives and the tutorial on this site and others, there is loads of info out there that will help you especially in regards to setting up for bending with a heater.

Hope this helps a bit.

Cheers

Kim
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Pull me Finga

[vandenboom]

I'd support all of Kim's feedback but would add the following...

If you plan to keep building, then the blanket will be probably be purchased sooner or later. But you can get away with 3 x 150W light globes for a while. I used that for 3 years before buying a blanket last year for the same reason as yourself - priorities. The same moulds can then be used with the blanket with little to no modification if you think about the design a bit.

As Kim said, even after using the blanket, I almost always need to touch things up on a pipe or bending iron. You also need the iron for things like headstock bindings etc. I used an electric element to heat a hot pipe which was great, but after recently blowing my second element in 2 years, I have given up on electric elements and spent $70 on a gas torch and hose from Bunnings that hook up to a larger gas bottle and use that. I only need it for short periods and it does the job.

When I first looked into getting blanket, I was similarly overwhelmed by all the info on thermocouples, controllers etc. Bob made it very clear to me - you don't need any of it. Just the 240V blanket. You just need to be very disciplined when using it not to get distrated, or spend $50 on a timer that turns off after x minutes if you don't turn it off first.
Frank

[Taffy Evans]

I use the light globe heating method and heating irons, and now its been mentioned I'd better get some spares globes now. I have a kitchen type timer that rings a bell at a preset time , and if for some reason I do not hear it a timer at the power source cuts the power. I stick the probe of a multimeter, that has a heat range on it, in-between the slats just to see what the temperature is.
_________________
Taff

[J.F. Custom]

Hi Bern,

Not much to add here to that above but...

Side blankets in conjunction with a bending mold of sorts, are very worthwhile purchases/setups. I forego one for years, simply using the bending iron but now that I have it, I rue just how simple, quick and repeatable they make the job. If I'd have known, I would have set one up first go.

LMI are just covering their backs so to speak. You just need to be very aware that the blankets get very hot, very quickly, and will, given the chance, burn down your workshop in similarly quick fashion. Don't walk away. Don't multitask. Don't get distracted. It only takes a couple of minutes.

A digital thermometer is handy to use in conjunction with a heat blanket. A cheap one (under $15 from Dick Smith or similar) will be fine. Just useful to monitor temperature for repeatable and consistent bending and tends to keep your attention focused so that you remember to turn the thing off!!

It would be easier to use a dedicated blanket for ukes, but with budget considerations, you can use the larger one with care. I do.

Bending irons are useful - period. However, you needn't think that you ought to buy the expensive electric model. A simple 'gas torch in a pipe' will suffice.

Hope it helps.

Jeremy.
_________________
J.F. Custom Guitars
www.jfcustom.com.au

Cannons Don't Kill People...
Pirates with Cannons Kill People.

[bernm]

Once again, thanks everyone ... Very very helpful comments in there.
Bern




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