Light wind sails advice

[Chiara’s slave]

If you can sleep off watch with your spinning prop all the way across the Atlantic I will be impressed. Those kind of noises have a habit of being very irritating very quickly in my experience.

Letting it spin for 3000 miles will have other interesting side effects too.

 

[RupertW]

If you can sleep off watch with your spinning prop all the way across the Atlantic I will be impressed. Those kind of noises have a habit of being very irritating very quickly in my experience.

I am concerned as we have only tried it spinning once for a long day sail - and that’s after decades of sailing with fixed props. We may well just fix it a couple of days out and add a day (or whatever) to our journey. But we have enough experience both at work and sailing to know you don’t change something fundamental before a major event unless you have no choice.

 

[RupertW]

Letting it spin for 3000 miles will have other interesting side effects too.

Go on?

 

[Chiara’s slave]

Go on?

Some manufacturers do specify leaving the prop to spin. However, nobody assumes you are sailing across oceans. The wear on bearings and gearbox needs to be taken into account. These are leisure products, for weekend sailors.

 

[geem]

Some manufacturers do specify leaving the prop to spin. However, nobody assumes you are sailing across oceans. The wear on bearings and gearbox needs to be taken into account. These are leisure products, for weekend sailors.

So about 500hrs of additional wear assuming a 21 day crossing

 

[lustyd]

So about 500hrs of additional wear assuming a 21 day crossing

Which in theory is 2 years wear for the average yacht on the engine etc. I don't think it's significant but for those watching the hour meter instead of maintenance it would certainly seem so.

 

[geem]

Which in theory is 2 years wear for the average yacht on the engine etc. I don't think it's significant but for those watching the hour meter instead of maintenance it would certainly seem so.

Yep. I love our three blade Brunton folder. Great performance under engine and no drag when sailing. The other great benefit of a folder is the vastly reduced risk of snagging the prop when sailing through pot infested areas. We have done this numerous times and simply slid over pot lines.
Earlier this year we managed to catch a huge net strung across the route between Antigua and Guadeloupe. The line that caught our skeg was 3/4" or 1", hard to tell. We sustained no damage even though we were towing everything whilst under sail for about a mile. We could see two large orange boys way off in the distance at each ends of the net, heading for us! It could have been a totally different story had we had a fixed prop with the kind of load we were towing from our skeg

 

[Tranona]

The 1 knot I got when letting it spin compare to fixed was simply observed but is trivial compared the the proper repeated tests done by magazines and experts.

I am simply reading the second graph from YM. If anybody is reading it differently or have other tests on relative speed and drag and power then it would be great to learn more.

It seems counter-intuitive that there is such a tiny advantage to folding rather than spinning but we can only learn from proper tests and it’s great to be surprised in life by unexpected truths - one test doesn’t change conventional opinion but it raises an interesting question.

But those graphs are not "tests" and neither say anything about speed changes relative to drag. You are hanging your argument on your increase of 1 knot - that is above what most prop makers suggest for folding and feathering propellers which is why I query it. Just suggest you go back and check that. I am not aware of any "proper" tests that actually measure speed improvements for the reasons I explained earlier. The only test I am aware of was a comparative test that concentrated on speed, stopping and bollard pull. The graphs you show are tank tests and give an idea of the levels of drag and potential reductions. There is no attempt to translate this into speed differences.

The only things that are certain is that the reduction in drag is there all the time and its effect on the boat's resistance is constant. The gain in speed is greater %age wise at lower speeds because prop drag is a greater proportion of overall drag. So a 0.5 knot gain at 3 knots is roughly 20%. At 5 knots it is 10%. Overall users report improvements in passage times of +/- 10%.

 

[Bristolfashion]

We do ok in light air with the standard cruising sails. Focussing on the basics of sail trim, fingertip tiller control and introducing the right amount of heel by crew distribution seems to work pretty well for us.

 

[dgadee]

I fancy a Hoyt gun mount spinnaker.

 

[RupertW]

But those graphs are not "tests" and neither say anything about speed changes relative to drag. You are hanging your argument on your increase of 1 knot - that is above what most prop makers suggest for folding and feathering propellers which is why I query it. Just suggest you go back and check that. I am not aware of any "proper" tests that actually measure speed improvements for the reasons I explained earlier. The only test I am aware of was a comparative test that concentrated on speed, stopping and bollard pull. The graphs you show are tank tests and give an idea of the levels of drag and potential reductions. There is no attempt to translate this into speed differences.

The only things that are certain is that the reduction in drag is there all the time and its effect on the boat's resistance is constant. The gain in speed is greater %age wise at lower speeds because prop drag is a greater proportion of overall drag. So a 0.5 knot gain at 3 knots is roughly 20%. At 5 knots it is 10%. Overall users report improvements in passage times of +/- 10%.

Have you read the article or understood the graphs? I have said my anecdotes like yours are trivial. It’s real world tests we can learn from - what is your interpretation of the YM tests and results and have you found any better or conflicting results so we all can learn?