Model Ship Builder

Clare: I take back what I said about the efficiency having to be better than 50%.

The friction depends on the cable tension so if you release the capstan, the cable goes slack and the friction drops to next to nothing (compared to the weight of anchor and cable).

The coefficient of friction for hemp on dry wood is given as 0.5 and at that value the cable tension more than doubles, going up by just over 120% and making the overall efficiency around 45%.

The cable would obviously be wet but I don't know how much effect that would have.

OK, One final version and I'll stop cluttering up Gene's build log:

I've assumed that the friction with a wet rope is slightly less than a dry one, but even then the power required has nearly doubled.

I've also set it to assume that the cable is buoyed up by the water, but even so the men couldn't sustain that power requirement.

Surprisingly, putting more men on each bar doesn't make much difference. They're too close to the centre to contribute much power. 

Things obviously get easier as the cable shortens but even when the anchor is almost fully raised it still requires 10HP.

Maybe it turned more slowly than I've assumed, but even then I can only assume that the men were changed regularly.

That's a great model Gene. I'd seen Glenn Grieco's model before and although I could understand the principle, following the construction of your model has raised and answered lots of questions.

As an example, Claire was speculating about the friction of the cables dragging along the deck. In your latest pictures, you can see they're clear of the deck at both the capstan and hawse hole ends.

The figures are a great success at showing how it operated. I'd choose to be the one at the bow looking to see how things are progressing!