Bending sides-

[rowka]

Looks like folks use either a bending iron or variations of the Fox bending machine that uses those silicone heating blankets. I never see anyone mention a steam box and bending forms. Is there a reason for this?

[sunburst]

Wood that is under about 1/4" thickness doesn't really need to be steamed in a steam box to be successfully bent. Since mandolin/guitar/uke/violin/etc. sides are generally under 1/8" in thickness, steam boxes, steam sources and bending jigs are not needed, so why sacrifice shop space for them?
Nearly anyone can eventually bend an acceptable set of sides using a hot pipe, many on the first try. It takes some skill and some time to develop the skill to quickly and efficiently bend accurately curved sides on a bending iron but it is the simplest method in terms of equipment and space, so that makes it the best method for a small shop like mine IMO, making only a few instruments per year. For small production, the speed and accuracy of the Fox-style systems is hard to beat.

Interestingly, until recent years (10? 15?) CF Martin was only using bending forms for dreadnought guitars and all other models had sides bent by hand by skilled workers using a hot pipe.

[mirwa]

Steam boxes don’t work for bending sides. In the time it takes to get the wood out of the box and into a position to be bent, they have cooled down too much.

When we bend on a pipe or say fox bender we are actually steam bending, we use the water sprayed on the wood to atomise instantly and create steam in the thin walls

Steve

[John Kelly]

I use a thin sheet of nickel (from my railway-modelling days) to sandwich the sides between the bending iron and the nickel. It helps me get more regular curves and helps prevent the wood from splitting if I get too enthusiastic with my bending! It probably works in much the same way as the bending devices metioned in this thread and helps to keep the heat where it is needed.

[amowry]

Another reason not to use a steam box is that it can easily get the wood too wet, which actually makes figured wood easier to break. For bending figured sides it's best to use as little moisture as possible, i.e. just enough to keep the wood from scorching. A quick spritz before bending on a hot pipe is all it takes.

[HoGo]

I think Siminoff did use steam chamber, but he bent very thick sides at 1/8".
Unless you are making large batches it is much simpler just bend sides on iron than investing in a bender. Good bending belt is necessary for highly fiured wood and iron that is fied to the bench and will take fair amount of pressure for smooth tight bends.

[buckhorn]

I've gotten pretty good at bending rims and have sold many sets.. Tried a steam box and just didn't work out.. It made the slats too soft and would split either along the grain or I would get the scroll almost done and would then crack.. I use a piece of 1 inch conduit pipe and a propane tank to heat.. I put a steal semi-plug in the end to keep flame from going all the way thru the pipe (and burning myself up).. Sand the slats smooth of any mill marks.. Mist the wood as little as possible with a spray bottle and keep it up to stop scorching.. It will scorch a bit but keep misting, it will sand out.. If it's a real tight curl, do it in multi steps and let cool between.. I've also made forms out of 2 x 6s to match the scroll shape and when done forming, mist well and put in forms and let dry.. May need a little touch-up before glue-up , but the forms really do help....If you just put aside to dry, the wood will try to go back to original shape.. And it's okay to reduce thickness around head blocks and points, just not too thin ( I've reduced thickness from about .090 to as thin as .050 in some cases).. and of course each piece of wood reacts differently to the heat, and you need to get a feel for it, after a few tries you will know when too much is "too much"......