Shinnery Oak, Selfbows take a board which can have a perfect back, or one where a good ring can be reached for the back..Also humidity plays into this a bit..Amazon natives don't have a problem, and some of their bows look similar to the same ones I have made.. Ipe is the name for the lapacho tree and there are a 100 sub species all dense, and fairly straight. There are boards which look almost like a dense black walnut board which I would make a selfbow out of. I don't always see a board like this at the yard, but I do find plenty which work great with a bamboo backing.
I have found it much easier for most to tiller out a blank with bamboo on the back as opposed to a selfbow..Partially because ipe being so dense is much different than NA woods, and this causes folks to try and string these bows when they are too heavy for their design or have a small hinge somewhere which get exxagerated in the limbs since they are smaller relative to "normal" bows.. Getting a perfect curve floor tillering is what I do and I make sure it's not too hard to string..even on the heavier ones..When I string an ipe selfbow for the first time it looks like a finished bow, and then I finish tillering it with the string on.. Yes its more challenging, and a bit gut wrenching, but the results have been worth it..and if over time it lifts a splinter due to grain or dryness, then a backing will solve this..
The backed bows have proven themselves in the driest and wettest of conditions..Selfbows generally like a bit more humidity. Just make it longer for drawlength, and if it holds up the shorten it if you want more poundage...
