MIMF

I'm new to acoustic building, so please forgive some of my newb questions. Maybe this should have gone into the acoustic section.

I am building a side bender, similar to the Fox style machine.
It will have a screw down press type, waist bender, and most likely use spring retention for the front and back profiles.
I am going to use a heating blanket.

There are a couple different types of bending slats available, and I am wondering which one is best for this type of bender?

SPRING STEEL.
I've heard that when these slats come out of the bender after use, they tend to spring straight, possibly causing damage to the newly bent side.
Is that correct? If so, how do you protect the side from damage?

STAINLESS STEEL.
Apparently these stay bent to a certain degree after use, solving the spring action breakage problem.
Do you have to straighten them out for the next use?
Stainless can be a bit brittle, how does this affect that part of it?
Being pre-bent would make it difficult to align the side for the next use wouldn't it?

What do you use, and how do you use it?

I use galvanized flashing sold at the hardware store 6 inch width.

Here are a couple pictures of my form.
The top bending slat is the galvanized steel also.

I nail the flashing to the form.

I know that the spring steel and the stainless steel work well also.

flashing has always worked for me too.
I don't use a Fox style bender but rather a solid mold, with a sandwich of variations on: Flashing, blanket, wood, flashing. Wood moistened if it's Spanish cedar, usually dry otherwise.
I do wrap either the wood or the flashing with aluminum foil in case the galvanizing might discolor whatever wood is being bent.

I use spring steel because it gives additional support to the wood during bending. It absolutely comes out of the bender flat which is a good and bad thing. The bad part is that you do have to be careful on sides that have a cutaway. But that can be mitigated by restraining the lower slat. You don't have to worry about non-cutaway sides.

Aluminum flashing...!!
Tom

Thanks for all your input guys.
I think I will go with the spring steel. After listening to you, and watching a few more videos, it looks easier to restrain the bottom slat when taking the piece out of the bender, than trying to straighten out a bent piece of steel for the next use.

The main thing to watch out for with the spring steel is it will stain and rust from contact with water. But this is easy to prevent if you place a piece of aluminum foil on the inside of each slat.

A good 'stack' is spring steel/foil/wet white or brown butcher paper/wood/wet paper/foil/slat/blanket/slat...the amount of water that the wood sees is controlled by how wet the paper is before bending...pretty useful for mahogany and other woods that that need to be a little dryer to prevent fiber collapse in tight cutaways and waist bends. As mentioned, spring steel provides a lot of support for tight bends, but requires some technique getting the wood out of the bender to prevent breaks in more brittle side woods or purflings. If you google/bing 'Bending+figured+mahogany+fox+bender', I am pretty sure you'll find a couple videos and articles of use.