MIMF

Hello all,
Here I go! I am going to build a mandolin this summer. I would like to build a flat top with the outer shape of a Martin or the Crystal Forrest design. Not very extreme on the bends.

I am looking to build a bender, but would rather not buy the blanket. I plan on building more than one.

If I use metal strapping on top of the wood, does a couple of light bulbs inside the box supply enough heat for the gentle bends I am looking for?

In the past, many people used incandescent lightbulbs as a heat source, usually in the base box. I think you'll find info and pics in the Library.

Also, there's hot pipe bending, basically a piece of pipe with a torch or a electric BBQ charcoal lighter inside. I'd go with the charcoal lighter.

What he said ^^^^^^

I'd go with the blanket! Contact Watlow and find out more about it...They're God's gift to the luthier!

Nothing wrong with using the hot pipe, it's my preference, usually. But there is a learning curve.

An old clothes iron and a bending form works also. I do have light bulbs inside my bending form, but they're more for heating to set the bend than actual bending.

One thing that sometimes is not mentioned when a beginner asks this question is the importance of doing a good job thicknessing the sides. You are going to want to make sure they are pretty uniform in thickness or the bends can be difficult to get right. Also, you will want to have a way to measure the thickness when you are done. With material this thin, a small change in thickness can make a great difference in stiffness. I know when I got started, I tried to bend way too thick. It took me a while to accept that 0.085" thick wood would be up to the task of holding an instrument together. Once I got comfortable with the notion of thinner side, bending got much easier. I remember bending 0.125" sides (not guitar size, much smaller and shallower) with a heat gun, water and inside mold. It got done but once I made a hot pipe and cut the thickness down considerably, the next one was much more enjoyable!

Bryan's advice about proper thicknessing is right on, especially about uniform thickness. When bending, a thicker or thinner area will often result in a lump or a snap on the side.

In another thread, I mentioned the idea of modding a toaster oven for heating the base. I think it would be a substantial improvement over lightbulbs in part because a reliable thermostat is included in a toaster oven (and probably an 'overheat' cutoff switch too), but because that nowadays, that incandescent bulbs with higher wattage ratings are getting more difficult to find, and will become more difficult to find.

About buying a blanket, I bought one years ago from Omega Scientific and it was much less expensive than other vendors at that time.

I have several blankets of different sizes for different uses. I always buy directly from the manufacturer, Watlow.

A small gas torch inside a thick walled aluminum pipe or oval works wonders as well though it's a little harder to control the temp that way. A steel pipe will work but the aluminum spreads the heat much more evenly being the better conductor.

I have been bending with a pipe for quite a while. I have sawn a nice fat softball bat in pieces and use the butt end an handle with a torch to bend.

I was hoping to not invest the blanket yet, seems inevitable though....

Nothing is inevitable. If you are comfortable bending on a hot pipe then stuff a charcoal starter inside your aluminum bat. If it won't fit inside the pipe let it get red hot before trying to bend it, otherwise you will break it. Instruments have been made for centuries without blankets, though they are very useful once you get used to them.

... see the new thread for the Toasta Special...

A 1/4" walled aluminum pipe, 500 watt halogen bulb, and dimmer switch has worked quite nicely for me. I believe the heat from the bulb is distributed much more evenly than it would be with a torch or charcoal starter (w/o hot spots). No doubt a lot of pipe rigs have been made with bent charcoal starters, but I never liked the idea of bending the element on one for fear of it shorting out. Not sure if that's a valid concern, but my hair is already as curly as I'd like it to be.

Halogen, charcoal starter, cartridge heater. . . Whatever you use, do yourself a favor and run it through a timer. It can be easier than you think to walk away and forget to shut it off. I run my pipe and blanket through an outlet box that plugs into the wall and ru a through a diner switch and hot tub timer before feeding the outlet I plug the bender into. Mind you, my blanket is the 2.5 watts per square inch variety so these hardware store items can handle it. Whatever you make for yourself, make sure you check your math. . .