Westerly sealord sailing performance and 3 bladed propeller

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aussimed

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I have recently purchased a westerly sealord with a Buhk DV36 hp engine and a two bladed propeller.

I am still getting to know the boat and how to sail it properly, particularly with an in-mast furling mainsail since I am used to traditional slab reefing mainsails. The boat does not seem to sail well to windward in strong winds, as she does not point high into the wind, is this due to the furling mainsail without any battens and also could it be due to the roller genoa which does not have the right cut to sail, when it is reefed in?

At around 2000 to 2400 r.p.m. cruising speed is 5.5 to 6 or 6.5 knots depending on sea state and wind conditions. I would like to know what type of fixed three bladed propeller suits this type of sailing yacht, so as to increase the cruising speed while mantaining the same engine revs and with the same fuel consumption.

Does Anybody have any experience with changing a propeller from 2 bladed to 3 bladed? On a cruising yacht I assume drag would be minimal. But does changing the propeller require alterations to the shaft or gearbox? Is it true that a shaft lock would have to be fitted to prevent shaft from turning during sailing?

I Thank you for your feedback in advance.
 
If you go to the Westerly Owners Website there is a discussion group you can register for and you will normally get answers to most questions. There is also a forum which while not as active, does have a thread on the Sealord and Oceanlord. In fact here is the link to the thread.

http://www.westerly-owners.co.uk/woaforum/viewtopic.php?f=1&t=529

You will find that some of these guys are in the states so there may be some time lag. They maybe off cruising as I believe one was crossing the pond this summer.

Hope that helps.
 
A few thoughts:

A W Sealord wont be the highest pointing boat in any conditions.

Battenless in-mast mains will never work as well as well-cut slab reefing mains.

Poorly shaped (esp reefed) headsails wont be as efficient as good ones.

Fixed props will have more drag than folder/feathering types (thus reducing pointing/sailing ability) but fixed is cheaper than folding which is cheaper than feathering - you pays your money and takes your choice.

The drag from a prop is the same on whatever yacht its on and a fixed prop will loose 0.5-1kt vs a folder\featherer

You shouldn't need to change shaft to change prop - you usually have the prop hub adjusted to the shaft.
 
The sailing part of your question has been answered very well. I have changed from a 2 to 3 blade prop. The biggest difference is in the smoothness of the power delivery under engine. Three blades will provide a noticable reduction in vibration when under power. Under sail you will loose at least one knot. My current boat has a volvo 3 blade folding prop and it's brilliant. Not as good as a maxprop astern but the drag reduction under sail is as good.

I used Propworks.com to size my prop and the brains of French marine in Brightlingsea who came up with the same answer after 30 seconds thought! The trick is to size the prop to the engine, i.e deliver the power from the engine to the water.
 
Sure... and whilst .5 to 1 kt under sail doesn't sound significant if you are planning on sailing any distance then I would think that as you are already planning to re-prop it would be a good idea to consider a three-bladed featherer.

I can recommend from personal experience Darglow (google them) and their featherstream prop. Really happy with mine.
 
[ QUOTE ]
Sure... and whilst .5 to 1 kt under sail doesn't sound significant if you are planning on sailing any distance then I would think that as you are already planning to re-prop it would be a good idea to consider a three-bladed featherer.

I can recommend from personal experience Darglow (google them) and their featherstream prop. Really happy with mine.

[/ QUOTE ]1 knot might be 20% of our boat speed in lightish conditions!

A few thoughts from a Sealord owner.

We are in our 5th season with our Sealord and one of the best changes we have made was changing the three bladed fixed prop to a feathering prop. We chose a max-prop, but you can take your pick from any of the folding/feathering props with the only proviso that folding props don't always give very much drive in reverse!

Regards sailing performance. Whilst a Sealord is not a stripped out high performance racer, ours points reasonably well. We don't have an inmast reefing main (we specifically put NOT having one on our list of what we were looking for in boats when we bought her). We tack through between 85 degrees and 100 degrees (depending on wind and weather) which I think is about par for a cruising boat. In any reasonable conditions I would expect to sail at about 45 degrees to the true wind, sometimes slightly less, sometimes a little more.

Our sails are not new, but reasonable for their age.

Don't blame the design of the boat - they are quite OK for what they are. My gut reaction is to have a good hard look at your sails....
 
The drag from a fixed-blade prop is very significant (it can be of the same order as hull skin friction in some situations). We've reported research on this at:
http://eprints.cdlr.strath.ac.uk/5670/01/MacKenzie_PM_Sailboat_Propeller_drag_Jan_08.pdf
The graphs towards the end have the important comparisons of prop types, as do the concluding remarks.
Not only does prop drag hold you back, it also impacts on your true pointing ability. This is because as you lower your speed through the water, the keel requires a greater angle of attack in order to produce the force necessary to balance the sideways component of the sails; this is manifest as substantially increased leeway angle.
 
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