Sizing a prop?...

I'm considering buying a sailboat that is 27 feet on the waterline and will displace 18,000 lbs. loaded for cruising. It only has a 12 HP engine (Yanmar YSE12) which is turning a 4-Blade fixed prop (13x7). The boat has never been in the water and I'm not sure if that type or size of prop is the best available. Naturally, I would like to maximize the propulsion without having to change the engine. Any suggestions/ideas?...

 

Have the boat put in the water! You wanna know how it feels, sailing and motoring. Any comments on the prop can't be made without knowing the particulars of the boat and the propulsion train, although the power on the engine seams a bit on the low side.

 

You will need to launch and after the engine is broken in , do a chart of RPM / speed in K .

The 4 blade will make the boat sail very sluggishly in light winds.

A feathering or folding prop is far better for fast sailing .


Also needed is the reduction gear ratio.

FAST FRED

 

Gear Reduction Ratio

The gear reduction is either 2:1 or 3:1 - I'm checking with the owner. There is no real opportunity to do a sea trial at this time.

 

With this displacement, engine size may very well be a bigger problem than prop size (and more expensive to cure), so if I were you, I'd insist on at least one sea trial!

 

who needs an engine? are you driving places or sailing places? ohhh i forgot, you have to drive out of your mooring. i know a guy, who had a 24 fter that could sail up to his mooring & off his mooring, he only had his wife & himself on the boat as well.

 

This was going to be my first response, but as this is a worldwide forum I remembered that the need of an engine depends largely on local circumstances. In Holland harbours are so cramped, entering without an engine is not permitted! Also skill can be an issue, if someone feels more confident with a back up that’s all right!

Drkirk,

Interrogate the current and, if possible, previous owners on the behaviour of the boat under power. What about the harbour master or his neighbours, maybe they can give an independent view on the boat handling characteristics!?

 

It's never been launched!

That's the tricky part... the boat is essentially new - it's never been launched so NO ONE has any experience with ANY aspect of the boat! I'd be "the first" which is both exciting and scary (sounds like sailing )


Capt. Kirk

 

If I were you, I would certainly not buy it without a sea trial first, unless it's really, really cheap or designed by a well-known designer. And I would insist on a full money-back guarantee!

 

Can't agree more with that!! Taking a sea trial is THE way of seizing a boat, not only for the propulsion, also for the rigging, sails etc.
The only way to get around this is to find out about this type of boat, is it a one-off or a series? If so there is maybe an owners club! They can give helpfull info.
Good luck Captain K

("Beam me up" is TOO EASY!!!!)

 

Steel Pilot Cutter

The boat is designed almost identically to a Bristol Channel Cutter - one of the best plastic cruising sail boats ever made under 30 feet. Who cares how it sails - as long as it looks "salty" at the dock!

 

Well, at the dock noone sees the prop

 

You're quite right! I reconsider, 12 HP is enough for showing off.

 

As long as it can throw a 3 foot blade... "If I had a long enough lever I could move the earth"... (or something to that effect)!

Basically, if this deal goes through, I'll be the "test pilot" for the boat. I'm leaving today to drive 500 miles one way to check this craft out to see if a trade would be worthwhile.

 

You asked for our opinion, you got it.
I hope you make a good deal and keep us posted.

Happy sailing