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Hanno,

Re smaller Fullers. My current mini Fuller2  prototype is roughly same size as a Bygrave and folds up to about 13 inches long. Cant get it any smaller, already need magnifiers to clearly read condensed scales and smaller diameter tubes would lose accuracy due to reduced scale length..  However, because the design is Otis King style, it has 2 copies of main scale and a “handle” which extends the length accordingly. You could just build an exact copy of Fuller 2 at this diameter size, with only 1 main scale and the log(or maybe a cos scale instead?) and sine scale + the 2 brass cursers. This would be shorter, but have the disadvantage of the old Fuller re brass cursers on the high seas and anyway, see my previous reports on the moves. The Otis King style requires less moves with multiplication and division and you can do both direct from the sine scales easily. My next “improvement” will hopefully be a new sine scale with cosines in red going the other way. (If not too cluttered). At the moment, I have to convert all cos to sines first. Anyways, I may have a go at a “short mini Fuller 2” ie original design. That may be in a few months time.

I don’t know if you have read John Letcher’s book? He says he could do his lunar calc with a ordinary trig slide rule. Never tried it, but can anyone explain it if true? Hewitt Schlereth, in his book talks about using an 8 inch circular rule for his calcs.

Currently, the only slide rule that I  know that fits your bill is my mini Fuller 2.

I shall watch this space with interest. I’m basically shore bound and beached this summer, so no sailing but therefore plenty of arm chair navigation!

Best wishes all

Francis