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CNC Carving A Trunk5/22
I've had a designer ask about making a custom bench. My sketch below. They would like it to be out of one solid piece of wood. It has some compound curves in it, so I can't do a veneer. Kind of curves underneath like a boat.
I don't know where to start getting info on finding a log with the proper moisture content, to be stable enough to carve away at it. I have thought about hand carving it, but I do have access that I can pay for some 5 axis work.
The bench would be climate controlled and indoors, but I would imagine it will continue to dry forever and at some point would need to crack somewhere.
I guess I have several questions:
I feel I don't have any issues with the fabrication, just sourcing the correct log.
Any tips or examples anyone has would be appreciated.
I believe you need to look for a species that is fairly light weight. You might be able to locate a western cedar log in the PNW. Are you prepared to spend at least $10,000? Alternately, consider a yellow-poplar log, but the variations in color might be unsatisfactory. You might find a redwood log in New Zealand. In any case, it is rare if the center will be solid.
Moisture content is an issue. As this is a rare activity, comments are just a guess. Checking would be minimal with cedar or redwood if you dry it slowly.
Would you accept a thick coat of clear acrylic for the final finish on all surfaces? If not, there is no good sealer finish, so plan to dry it fairly well prior to finishing. Do not seal the wood if there is substantial water in it...mold and even decay can result, plus as it dries, it might warp and crack. The three species I mentioned do indeed dry fairly fast...based on your sizes, perhaps a year or so.
How about an alternative...buy a large log, saw it into parallel pieces maybe 3” thick, dry them, flatten the pieces with a planer or CNC, and glue the back together in the same order as they were sawn, minus sawdust and planer shavings.
I threw out a number of around 10k for the log only and that didn't seem to shock them.
I think I like your idea of sawing a log into slabs and then glueing them back together so that the moisture can get out.
Is it normal for a local mill to have a tree sequenced like that. Or is that something that I would need to more than likely ask for and have specially sequenced for me?
You might do well to study the early works of Wendell Castle. He did lots of heavy looking pieces by brick-laying thick sections to the basic form, then finish shaping the glued up hollow form. this overcomes the checking from drying heavy members, as well as reducing a ton of weight.
But if you feel it has to be made from one log, I would hollow it from the bottom with a chainsaw, so you aren't trying to dry a log, but rather just an odd shaped piece of thick lumber.
If you really think your customer is hot to go, you need to make a maquette to get it started. I'd be surprised if they would sign off on that crude sketch.
I think you are dreaming if you think doing this with CNC is the way to go.
The sequence you need is achieved by "live sawing" and is common for hardwoods when the entire log is sequenced. It is more common outside of North America. Sometimes it is called sawing flitches or sawing through and through.
Catalpa would be a very good choice. Incredibly lightweight and very stable while drying.
I would vote for standing deadwood. Find a tree that died a few years ago, standing in a forest. If the bark is off, and upright, then the rot may not have started, and it would make a fine, fairly dry log. The gray surface can be sanded and shaped if needed, showing the good wood underneath.
If the 10k did not scare them off, then they are looking for a piece of art. A real log is the only thing that looks like a real log, so give it to them.
Contact local landowners, Forest associations, even the National Forest if nearby. Time to go for a walk....
Thanks David, I've got enough now to try to steer them in a direction. I hope I get to post a follow up in the future.
Thanks for everyone's input.
With so many tornadoes, coupled with the excess rainfall, across the middle of the USA, I'm sure there are plenty of large trees that were uprooted, and there for the taking.
However, being always on the hunt for large trees myself, I do know of a large red oak and sycamore over 4' D that are standing but available, and maybe a dead standing walnut in the size range, although I know its got ring-shake.
If the OP really has the commitment with some money up front, I could help by harvesting the tree, roughing the form, and hollowing out from the bottom, and shipping to wherever he is located. Then he can use CNC if that is that is his chosen path.