Utilizing free wheeling prop spin

[Jim Cate]

Originally Posted by robmclennan

Jim Cate here's one of many video's, enjoy. Notice it is a Sail Drive, but there are other youtube video's as well.

CRUNCH!!!

Sorry, I don't do videos, being on a limited data plan. But sure, it is possible to bugger up anything, including fixed props, especially if you don't maintain them correctly. There are many thousands of folding props in use, and the incident rate of collisions due to one suddenly not working is kinda vanishingly small.

At any rate, is it your point that we shouldn't use folding props because they will lead to collisions, and thus we will not notice the loss of sailing performance due to some regeneration scheme?

[robmclennan]

What I have replied to were sailors that questioned a spinning prop. It was posted that it was done before, in the 80's with success. I suppose the best option would be a type of outboard outdrive that can be fully retracted. The purpose is to add another way to keep the batteries fully charged. Nothing more, nothing less.

[StuM]

Originally Posted by robmclennan

What I have replied to were sailors that questioned a spinning prop. It was posted that it was done before, in the 80's with success. I suppose the best option would be a type of outboard outdrive that can be fully retracted. The purpose is to add another way to keep the batteries fully charged. Nothing more, nothing less.

You mean like a Watt & Sea which is also your auxilliary propulsion?

Outboard propulsion has many problems on a sailing vessel which I won't bother to go into.

[Cherod]

Originally Posted by StuM

I would bet the two different possible answers are available from two different manufacturers of engines and transmissions.

The appropriate mode depends on the specific combination of engine and transmission (gearbox and bearing lubrication and clutch type being important factors)

Sorry if not clear , I was meaning the same set up ,,,, as is the case with most things " expert " . (Note to myself ) , must try calling a few yanmar dealers / " experts "

[Captsteve53]

Basically an electro-mechanical clutch capable of running the horsepower from say a 30-60 Hp engine would be very large and offset the power you generated from free wheeling to keep it engaged when running the engine,

Reality as i have found it you get nothing for free!

[Pete7]

Originally Posted by robmclennan

Mango51 Thank you as it is feasible! The only difference is I proposed adding a electromechanical clutch so the prop could Free spin while under sail.

Why, most marine gearboxes will allow a free turning propellor, why have the extra complication?

Also you didn't answer my question, what would you advise, a $100 solar panel or your very expensive solution for other to get the best bang for buck?

If its only occasional use a Honda 20i takes some beating and regular use well how about this idea: http://betamarine.co.uk/portfolio-it...id-propulsion/

Pete

[Cherod]

Does not have to be some expensive set up , how much can a cog a chain ( drive ) and an alternator cost , not a lot .

[robmclennan]

Pete7, Do you sail at night? How are those solar panels working for you from sunset to sun rise? Isn't the point of having a sailboat going green? If your prop free spins why not utilize that potential power? Why add a clutch? Stop the wear to the transmission. The engine and transmission are taken out of the equation. Why would you even consider changing out your engine for a hybrid one?

[Adelie]

Originally Posted by HopCar

Mark, have you ever seen an explanation as to why a freewheeling boat prop generates less drag and a freewheeling airplane prop generates more drag?

Because airplane props are generally adjustable pitch and can be fully feathered.

For fixed pitch props, air & water, free spinning is lower drag than stopped.

For adjustable pitch props feathered & stopped is lower drag than freewheeling unfeathered.

[robmclennan]

There is always a better way! It is the expense that has to be considered. If 1982 Amel Mango utilized a similar device and it worked, then why not? Not all clutches use friction materials, but I was going on the cheap. Some have teeth that mesh. Worried about corrosion then change to a high grade Stainless like 316.

[StuM]

Originally Posted by Adelie

Because airplane props are generally adjustable pitch and can be fully feathered.

For fixed pitch props, air & water, free spinning is lower drag than stopped.

For adjustable pitch props feathered & stopped is lower drag than freewheeling unfeathered.

And generally, aircraft props don't have a clutch - so when they spin, they are turning the engine.

[robmclennan]

[robmclennan]

StuM why bring aircraft into the conversation? You are comparing an aircraft flying at 100 plus mph to a Mono Hull sailboat travelling at 2 to 8 knots. Might as well bring helicopters into the conversation as well as they can land safely by auto gyration. Feathering aircraft props, feathering helicopter blades, all of which are terribly expensive! What is the relevance?

[StuM]

Originally Posted by robmclennan

StuM why bring aircraft into the conversation? You are comparing an aircraft flying at 100 plus mph to a Mono Hull sailboat travelling at 2 to 8 knots. Might as well bring helicopters into the conversation as well as they can land safely by auto gyration. Feathering aircraft props, feathering helicopter blades, all of which are terribly expensive! What is the relevance?

Why? Because Hopcar asked:

"Mark, have you ever seen an explanation as to why a freewheeling boat prop generates less drag and a freewheeling airplane prop generates more drag?"

This is a frequent issue raised when the topic of freewheeling v locked props is raised and many people mistakenly believe that the aircraft comparison is a legitimate reason for locking their prop. (And yep, we also regularly see helicopters brought into the same discussions).

Stick around for a while. Many subjects keep recurring and new members ask the same old questions and don't realise how many times their ideas have already had the pros and cons discussed in depth. (And such threads frequently drift into "slightly" off-topic directions - it's the nature of forums)

BTW, aircraft may be moving much faster, but the medium the prop is travelling in is a lot less dense than water. One factor counters the other

[robmclennan]

The vessel is being pushed through water at 2 to 8 knots. When the prop is free spinning it is cutting it's way through, said water. The faster the speed the faster the rotation. The propeller that is locked produces 250% more drag then a rotating prop. I think we have beat this subject to death!