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Join Date: Sep 2005
Location: New Westminster, BC
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Re: direct drive
So v-drives are similar to a transfer case in a 4wheel drive truck? I wouldn't think that's efficient for long periods or high rpm.
So 180 from the point of the arrow is the gearbox output?
Yes... the coupling you see in the photo is under the arrow in the diagram, the shaft is shown exiting at an appropriate angle for the hull, carries on through the shaft log and strut to the prop.
It's really no 'less efficient', though there's an 'extra' gear or two involved. It's not an unusual practice. It gets the engine more aft vis a vis the prop location, often getting it further out of the accommodation space and opening up other options there.
With today's proliferation of aft cabins, though, I think they are used less often now as the engine can't sit so far under the cockpit anymore. From a service/convenience point of view a straight drive (better term than 'direct) is probably better all round.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)