I have just done two days of hard labour.
My offence was to make a mast that is 50mm across at the top, 80mm across at the base and 6.1m long. There was plenty of time to contemplate why sanding took so long on this project. I’ve made several masts with cross sections around 50mm during the lockdown, and sanding them never took more than a few hours. I actually made my physical and mental torment worse by starting at the narrow end.
I acknowledge that the punishment fits the crime, and it’s all a matter of pi (π, about 3.14) and his mates radius (r) and 2. Yes folks, I’ve discovered that the circumference of a circle is 2 multiplied by 3.14 times r, so for every 1mm increase in radius there is more than 6mm extra surface to sand.
You can see the difference in the photograph. The offcut to the left is from the top and has been partly rounded. The base of the mast to the right shows just how much rounding there is to do.
At the top end of the mast there was 25 times 2 times π = 157 mm of surface to sand. By the time I got to the base of the mast there was 40 times 2 times π = 251mm to sand. That’s 60% more. No wonder the job got slower and slower as I approached the wide end.
The mast now has a coat of epoxy and when that cures it will be time to sand the mast again. Next time I start at the big end because that will make the job go faster.