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Hi All... been a while since i built my first (like 3 years ago!!) and am finally starting on #2 and #3...

One of the two (and maybe both) guitars is going to be using laminated sides. So i got some seconds sides (Grenadillo) and thinned them down to .o6o.
I built a bending machine and I already don't like it. The springs are too powerful and awkward to set up, and once i turn on the blanket i panic trying to get things set.

Maybe it's my newbie technique, but when that blanket starts sizzling i found myself getting frazzled trying to get things bent.

Second thing i learned: Heat and Spring steel and water = instant rust! The first side looked like i roasted it over an open flame pit and fell asleep whilst doing it. Literally black. Looks like it'll scrape off but it's damned ugly. It'll be on the inside so i am not too worried. No i didn't follow reccommendations for using butcher paper (seemed too expensive and didn't want to wait) so went ahead without.
Q: Had i not used water (and maybe i don't need to?) will just the oils and water in the wood do that same thing?

For the second side, i looked around for some paper to use and setlled on that pinky red underlayment paper as i always have a roll sitting around... and that worked really well, no discoloartion at all. The nice thing is the roll width is exactly the length of the steel slats so a win there. Not sure if the paper would discolor lighter wood.
Q: Anyone ever try that flooring paper and have cautions against using it?

The third thing i learned: Make sure you have a working thermometer! I don't know how accurate the thermal cutout switch is on the chinese blanket and when the oil from the wood started smoking (maybe it was the wood burning) i flipped out and pulled the plug. I had bought a klein multimeter and was happy to discover it has a themocouple with it and decided to use that. Well the temperature never changed and obviously the smoke told me otherwise. So i have no idea what temperature i had reached. It has a celcius indicator on it, so i let it go just shy of 150C but again, wasn't sure on how accurate it would be.

Looks like the thermocouple has two hairsized wires joined by solder, so i resoldered it and it does seem to be working tonight.

Because i shut the heater off fairly quickly there was considerable springback - even though i had let it sit overnight. So i have redone the side tonight with a working thermometer and held it at roughly 300 F for about 7 minutes. again, i'll let it cool overnight and see if it holds better or if i have failed.
I do think it's close enough to use as a laminating layer as long as the outside bends are perfect.
Q: I noticed that the controller did not reach a temperature and hold it there. Instead, when it got up to temp. it would shut off and the temp would cool down by 100F and then come on again. took about 4 cycles like that through the 7 minutes i left it on. Each time the cycle was longer as more and more mass held the heat, but i am wondering if this type of controller is not adaquate? Does the heat need to be constant for this to work?

I'll post some pictures tomorrow... nice to be back!

Rob

Some comments from someone who has felt your pain.
Non-stainless spring steel slats and rusting - use aluminium foil between slats and wet paper.
Paper - I don't really fancy pink maple for example, (but maybe it'll start a fashion!) - I use heavyweight wallpaper lining paper - white. easily available, works well.
Got to have closer control over the temperature, 100 deg. swings will not help, you'd be better with an on/off switch and a decent temp read-out (but really don't need the hassle when you're bending), you can check accuracy in boiling water or clear steam.
There is some good help in tutorials section to make your own controller, mine works well and cost less than $40
Springs - "chest expander" springs are cheap and work well.
Some water is needed for bending, more or less depending on species and figuring.
Good luck!

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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.

I spray paint the slats with High Temp grill paint. Works great no rust. Have to respray as it will wear off.

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Beautiful and unusual tone woods at a reasonable price.
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Additional info regarding spring back...

When bending Sapele for instance, after completing the bend I cook the side for an additional 20 minutes at in my case 280F, let it come to room temp, then cook it again at 280F for 20 minutes. I repeat this for 2-3 cycles. Sapele will pretty much turn back into a flat stick otherwise (I exaggerate to clearify!).

My setup is an LMI blanket and controller, Blues creak stainless slats, in a custom fox inspired bender.

My recipe is (bench up) slat, blanket, 6" masking paper (lightly wetted), side (lightly wetted), 6" masking paper (lightly wetted), slat. Water is sometimes skipped depending on species. EIR gets no water and zero addition heating cycles.

Best, M

Sapele, anigre, and other woods that seem to be a little more difficult to bend benefit from the use of SuperSoft II - you might search for threads on use. SuperSoft II cooks out of the wood during bending, so no issue with subsequent glue-up into laminates. While there are other veneer softeners on the market, SuperSoft II seems to be unique in its ability to ease bending of difficult woods.

The paper and isolation layer of foil technique is what we use with spring steel slats - this material provides more support than spring stainless for bending tight curves, and avoids the slat cleanup chore with cocobolo and other resin-laden woods. Instead of the inconsistent wetting seen with spray misting or soaking of wood, the paper is used as a calibrated reservoir depending on the moisture needed for the wood (less for woods like mahogany where too much water encourages fiber collapse on the inside of bends). Details are given in the linked video, as well as a few others on YouTube.

https://youtu.be/Q7vd9wGG4LM?t=13

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A constellation only takes shape when one maps the whole.
- Beth Brower

I have stainless slats from Bluescreek, too. They’ve lasted a decade so far and seem like they should last another.

My sandwhich is slat/wood/slat/blanket, with the blanket being on top.

Other than that, I use Todd’s method in the videos Woodie linked to. To a T. I think my kraft paper was from Home Depot?

I used a very inexpensive digital thermometer until getting a thermocouple for my multimeter. I mean, I think it was under $5. The thermometer worked great, and the thermocouple works even faster. I’ve always controlled the temp with a router speed controller from Harbor Freight. I have everything to put a blanket controller together though and have it on my project list.

Good luck!


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Regular, rustable (is that a word?) slats for me. I dampen the wood with a spray bottle, then wrap in foil. Same slat/wood/slat/blanket order for mine. I have a decent thermometer that I had for some water temperature monitoring work I was doing. The controller is a little touchy, but if you pay attention, you can keep a decent temp. The foil definitely gives you a bit more working time before the water steams away. I've bent some decent cutaways, including on figured maple, without any breakage. Having a second set of hands helps to keep things aligned as you are dealing with all the layers of the sandwich.

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Tony Thatcher
Bozeman, Montana

Here's a cheap source for stainless slats that I've used. McMasterCarr item number 53755K44. Their Stainless 18-8 shim stock comes in a roll 100" long by 6" wide and can be cut to length with tin snips. Various thicknesses available (I use 0.025"). For under $40, you can get three slats and have an extra.

So much thanks for all the feed back.

I rebent both sides today. I went out and bought the harbor freight router controller that seems so common to use and .... am not happy with it.

First i rebent the Scortched side. With the harbor freight controller i could get it relatively close to 300F but it was touchy. I got it up to 295 and decide that was enough. Let it sit for about 10 minutes and it crept up to 319F... pulled the plug and let her sit overnight and it was pefect. no additional scortching and it stayed nicely bent.

So i redid the other side as well and as luck would have it i broke the thermocoupler again (don't really think i fixed it.) but i had marked the controller and just used that to judge. Again it went fine and both sets are bent to may satisfaction. Tomorrow i will attempt the out sides (Paduak at ~0.75)

I am fairly happy with what i did,but i can see the need to build the PID controller in the tutorials...ut they were tooexpensive.

Paul... ythanks for the source. I would have bought the SS bought the SS slats but thought they were too expensive. This source sounds fine. But i think i will use the ones i have for a while and did go out and cet a can of the stove black paint. Love that ideas that come though here.

and tony, thanks for the pics of your side bender. I thnk the springs i used are way too tight and i like the idea of the rubber straps.

No problem. Those bungee chords are adjustable, so I can dial in the tension depending on what size side I'm bending. Seems to work fine.

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Tony Thatcher
Bozeman, Montana

i once had the creases from aluminum foil embed into my sides at the waist.

that was interesting.

Decided to start new thread..

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Pat

We don't wrap the foil or paper so as to form an envelope - separate sheets sized to the slat work well, and will not pull, bunch up, or wrinkle.

We no longer worry about temperature for woods like mahogany, cherry, curly maple, sapele, etc. which are treated with SuperSoft 2...on a 5 watt per square inch blanket, we begin the waist bend as soon as steam appears (blanket is running full open), and follow with the lower bout and then upper bout or cutaway. Once the bends are complete, there should be at most a few minutes more of steam, so as soon as we stop seeing any, we click the controller over to 'variable' and about 3/4 setting on the rheostat for a single 35 minute drying cycle. This avoids exhausting the moisture in the bending stack before the bends are completed, which may occur if the start of bending is delayed waiting for some arbitrary temperature.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Paul,
I'm interested in trying these slats. I've never used Hardened SS before. How does it behave? Does it hold the bend or spring back like spring steel blue slats? Thanks!

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Joe Beaver
Maker of Sawdust

A good tip i got from this video - https://www.youtube.com/watch?v=gS78naDiB4k&t=1137s - (05min13sec)

Is to use little blocks of wood to keep the blanket away from the upper and lower bout whilst you bend the waist... this really reduces the chance of over cooking those sections.

G.

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www.leddingtonguitars.com

I have a digital controller, but went years without one. It doesn't have to be hard, especially with no cutaway. Paper and or foil for the staining. Spray the sides with a mister bottle. Pretreat with SSII if it's riskier. Plug in the blanket. When you start hearing the sizzle, do the waist slowly, and stop a bit short. Then the lower bout, then the upper. Finally take out the slop by cinching up the waist. Then unplug the blanket and let it cool off. After it's cool (an hour?), plug the blanket back in and let it heat back up and unplug it. I used a cheap meat thermometer to shoot for 300F or so, but your nose can tell you when it's getting warm. Repeat the cycle a few times to get the bend set and the wood dry before you take it all apart.

After I hear the water sizzling, I bet it's less than a minute total for the first cycle.

Most of all, DON'T LEAVE IT ALONE WHEN IT'S PLUGGED IN! Not even for a quick second when you run to sign for UPS. It takes very little distraction to end up with a fire.

Someone I saw was very patient or stubborn and drilled their spring steel into perf-steel so things would dry faster. Has anyone else tried that? Is there a reasonable source for perforated spring steel? How about stainless perf spring?

Mike

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Mike Lindstrom