How to line up 2-blade propeller

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lindsay

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In the Sept issue of PBO, which I do not have to hand, there is an article about a new home built steel yacht in Wales. In a section on the propeller, it says that a two blade propeller, which results in less drag than a 3-blade, can be "aligned vertically" to minimise this drag.

This sounds great, but how the heck do you align a propeller vertically while underway? By trial and error checking the boat speed?

Thanks
 
On my yacht I lift the cockpit board up and look for a marking on the shaft befor engaging reverse.
 
As Ric says, mark the prop shaft. On one boat we raced with a fixed two bladed prop and lined it up every time. Saved us a few points on the handicap.
 
Marking the propshaft is the sensible way, but I have heard of boats with a transparent window built in for the purpose.

Pete
 
Last time I had the boat out I lined up the prop vertical then put a white paint mark on the coupling and one on the gearbox. If the time ever comes that I want to line them up the marks are there.
 
I can't help thinking if I was going to the bother of a window in the hull to look at the prop', I'd go the next step and fit a trunking like a daggerboard case, to allow a breadknife lashed to a pole cutting away fouled lobster pot lines etc.

Canal boats do this with a 'weed hatch' but there's obviously a good reason why offshore boats don't.

After having to repeatedly remove and fettle a log transducer and getting a demonstration of water pressure, + the leaks around the base of a daggerboard boat I had, I reckon such a setup in an offshore boat would take serious build construction, and there's the problem of a fairing plug to avoid drag.
 
Seajet said:
I can't help thinking if I was going to the bother of a window in the hull to look at the prop', I'd go the next step and fit a trunking like a daggerboard case, to allow a breadknife lashed to a pole cutting away fouled lobster pot lines etc.
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I think he means a window if the engine cover/cockpit floor or wherever you could see a mark on the shaft/coupling.

I hope no one would recommend a hole in the hull!
 
davidej said:
I think he means a window if the engine cover/cockpit floor or wherever you could see a mark on the shaft/coupling.

I hope no one would recommend a hole in the hull!
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No, he means a clear window in the hull. Some sort of clear plastic moulding faired into the hull. Lots of serious racing boats have more than one. Typically to check the keel hasn't picked up a line and perhaps with one for the rudder and one for the prop'. I don't know what your problem is? They are strongly constructed and when did you ever hear if a racing yacht being lost due to one of these inspection windows failing?
 
john_morris_uk said:
No, he means a clear window in the hull. Some sort of clear plastic moulding faired into the hull. Lots of serious racing boats have more than one. Typically to check the keel hasn't picked up a line and perhaps with one for the rudder and one for the prop'. I don't know what your problem is? They are strongly constructed and when did you ever hear if a racing yacht being lost due to one of these inspection windows failing?
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A rather brusque reply!

No, I have never seen one -I don't race.

Just seems a bit drastic when you could look at a mark on the shaft.
 
davidej said:
I hope no one would recommend a hole in the hull!
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davidej said:
A rather brusque reply!

No, I have never seen one -I don't race.

Just seems a bit drastic when you could look at a mark on the shaft.
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I don't race much either and certainly not at the level of the boats that have these windows through their hull.

My apologies if I seemed to be brusque - it was your comment about hoping no-one would recommend a hole through the hull and I perhaps misunderstood you. Holes through the hull seem to generate a lot of angst from some people.

For the racing boat a mark on the shaft isn't relevant as they all have very slim folding propellors. They do need to check that the prop has folded and they also like to check there's no weed or lines caught on the keel or the rudder. Its a very different sort of sailing to what (perhaps) you and I partake in.
 
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