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WOOD BENDING (PART 1)

Since the step notches on the modified frame protrude into the bed, the bed floor would have to be modified to fit around the notches and the diff when the truck is fully lowered. I had a few choices, raise the entire floor to clear.... but then the beads rolled in the stock bed side panels would no longer match the floor interface. Or....leave the floor at the same elevation but raise the floor local to the notches and differential. I decided to do the latter.

The next decision was how to raise the local area. I could box it out using the same wood used on the rest of the bed or I could fab a metal tunnel or hump for this area. After looking at every way imaginable way to do this I settled on trying to see if I could form the wood in this area.

I had already dipped my toes in the steam bending foray but like I mentioned before the process needed some refinement for this more difficult level of bending. Bending 1/2” thick wood to gentle curvatures in-place was somewhat difficult but bending 3/4” thick wood to a tighter radius on a separate tool was going to be exponentially harder. So off to consult the internet for more answers....

Like I previously had read, quarter sawn oak was supposedly a good wood to steam bend. This was stated by several online sources, but after further investigation the preferred curing method hierarchy for steaming wood was green wood, followed by air dried wood, then....................kiln dried wood (a distant 3rd). Unfortunately green qtr sawn oak wood was impossible to find (and would take forever to fully dry and stabilize after forming without proper equipment), air dried oak was next to impossible to find and kiln dried was just simply difficult to find (and all of it was expensive). I ended up special ordering some kiln dried from Home Depot, but there were a few others I could have gotten it from online (but Home Depot offered free shipping).

After further research, I lucked out and found this guy on YouTube that did a ton of steam forming of old wagon parts (wheel and top bows) that had some good tips for doing it with kiln dried wood. I also found somewhere that mentioned that if they formed kiln dried wood they soaked it for a week (in a creek near their house) instead of a few days like I had done before. The other tidbit that I picked up was that someone suggested adding Downey fabric softener to the water to loosen the wood lichen to make it more pliable.

Now that I knew to soak the wood for a week in a water solution with fabric softener in it (½ cup per gallon) the next issue was the actually forming process of the wood. The wagon guy and several others also stated that you needed to keep the wood in compression as much as possible to keep it from cracking. Apparently wood can compress a larger amount (18-20% ….but don't quote me) but can only stretch (tension) a small amount (3% or so...again, don't quote me) before cracking. To keep it in tension, a metal strap was placed on the outside surface of the wood while bending and the ends are clamped or constrained to the strap. This basically shifts the neutral axis of the wood being bent to be in line with the strap and the entire wood plank is compressed while being formed instead of part of it being in tension.

So now I had a plan for prepping the wood and bending the wood but the last unknown was trying to nail down the spring-back on the wood. Just like metal, you have to over-bend the wood and once it is released, then it will spring back into a different shape. The Youtube wagon guy had formed some thicker pieces of a different wood species at 90 degrees at a tighter radius than what I needed and had a 2” spring-back. Using the ever-so-accurate WAG method (wild-*** guess), I decided to use half his number. Since I had thinner wood, a smaller bend angle and a more gentle curve (bend radius) than he had then that seemed about right to me. After measuring the frame structure geometry on the truck, I determined that I needed and inside radius of approx 15.25” to clear the suspension and frame. So I needed a form block of 14.25”R to get there (15.25” minus 1” spring-back) and hopefully (fingers crossed) it would relax to the 15.25R.

I had a stash of lumber left over from my pole barn construction that I planned to use to build the forming tool. The tool I had in mind was roughly based on the wagon guys more elaborate set-up. His tool was powered with an electric or hydraulic driven pull cable but I would simply use two large ratchet straps to pull the board ends around my wood mandrel.

For the compression strap, I ordered a roll of .025 thk x 6” wide stainless shim stock and welded carbon steel angles onto the strap ends to restrain the ends of the wood. I also welded some ¼ dia steel loops on each end for the ratchet straps to hook into since the hooks were rather large. The strap was designed to tightly fit a 47” plank (so I could get 2 pieces out of a 8' board). There is also a hole in each angle so that I could put a 3/8 dia eye-bolt thru it and the board. When I did my initial forming pull on the wood with the ratchet strap, the ratchet strap would run out of travel before the pull was complete so this would allow me to put a smaller strap from eye-bolt to eye-bolt to hold it while I reset the ratchet straps. I also used it as a secondary safety strap once the pull was complete.

Prior to soaking the wood, I cut it to 47” length, drilled holes to accommodate the eye-bolts and I had read somewhere that you needed to seal the end grain to control the water infiltration in this local area and essentially keep the ends from getting too mushy (since end grain absorbs water when unsealed). I coated the ends of the boards with a wood sealer/primer.

To soak the wood, I took some 2x4's I had and made a simple rectangular frame. I then sit that frame on my shop floor, draped a moving blanket inside of it and then placed about 6 or 7 layers of plastic on top of the blanket to hold the water and boards. I placed the board in this set-up and poured the softener/water solution onto it and covered it with another plastic sheet to minimize evaporation.

Part 2 will cover the actual forming....