Man Jim but you sure made alot of sawdust! Did you thru mortise the header thru the posts? That must've been fun :-)

Hi,
About ten hours for the first one, 8 or so for the second. This does not include time spent setting up the lathe and making some modifications. I did not keep a close time sheet.
The fixture could have handled a bigger log than the 15"x11.5' ones.
The Harbor Freight router replaced a Freud FT-2000e (almost new) that failed(speed control module) about half-way through the first column. The HF did the job.

That's interesting. I once read about turning ship masts using this technique. As I recall the masts were about 60 feet long. They were all turned with a slowly revolving lathe and a traveling router.

What RPM were you using?

Did you go through more than one bit?

What was the depth of cut on each pass?

Would you anticipate that a log say 18" in diameter and 25 feet long would sag enough to change the taper or straightness of the sides?

Thanks for stretching my mind.

Lots of chips, for sure.
The mortises were made with a drill press and 2" hole saw that was about 2" deep. Holes were drilled on 1" centers and slugs knocked out with a chisel. I made four extensions from 3/4" round bar to drill past the center, then rotated the post to drill from the other side. Pilot holes, 1/4", were pre-drilled. The corners were squared up with a Husky electric chain saw.

I did not check the rpm, I would guess 1"/sec. at the cutter. A too strong cut would slow the rpm and give time to back out the router. One 1/2" x2" carbide inserted bit did the job. Depth of cut was about 1/2". The logs were pretty dry Douglas fir, cedar would be softer and probably last longer.
No idea on the 18"x25'. A center roller rest could be added with a fabricated ring fitted to the log. They must have had some intermediate rests for a 60' mast unless it was for a ship-of-the-line!