Launch with a low prop shaft

[Martin Field 1Participant @martinfield1]

I have a hull which I am making into a steam launch, but the prop shaft will, I'm sure, end up below waterline level. I've not had that before and wonder how you all seal a shaft where that's the case. Is a tube full of grease enough?

Martin

[Martin Field 1Participant @martinfield1]

[Kev.WParticipant @kev-w]

Silicon washer at the prop end, the thrust from the prop going forward will help stem water ingress, I also put a helical groove on the shaft, that helps push any water back out of the tube.

It works for me, but I still get a small amount of water into the boat, so try to incorporate a bulkhead to limit the forward progress of any that gets in & keep your electrics forward of the bulkhead if possible.

[Martin Field 1Participant @martinfield1]

Thanks, Kip. A helical groove? How the Hellical do you cut one of those? My wee lathe doesn't have screwcutting on board.

Perhaps some absorbant material in the bilges may help, but I take your warning and will keep the electrics well tucked away.

Cheers,

Martin

[Dodgy Geezer 1Participant @dodgygeezer1]

Another trick is a thin-walled silicone tube – ID slightly less than the prop-shaft. Push it on over the prop-tube at the motor end, and let 1/8" or so overhang the prop-tube onto the shaft, so that it makes a seal. See below:

[Kev.WParticipant @kev-w]

I cut my helical groove with nothing more than a junior hacksaw ( where needs must, man finds a way )

It took a bit of time and a steady hand, but it worked.

[Kev.WParticipant @kev-w]

Thanks DG, will note that one down to try, will save a lot of time & effort if it succeeds.

[Colin BishopModerator @colinbishop34627]

Getting a little bit of water in under those circumstances is pretty normal but it will only be a small quantity and, as Kip says, you can build in a small dam inside the hull to stop it spreading.

Colin

[Martin Field 1Participant @martinfield1]

Gentlemen, once again, thanks. A hacksaw eh? A man of my own kind there!

Just modified the old wood in the hull to accept a nice waterproofable area for any drips, but I like the silicon tube idea as well and will see if I can find any. But on this model the shaft is "nutted" close up to the tube.

Martin

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