Can a EP saildrive be mounted as rotary and lift up ?

[Dave_S]

I'm looking for advice and opinions on EP. I'm interested in high return regeneration as the only realistic way to make it work for me. I believe it will only work with regeneration similar to the levels seemingly made by the servo-prop system that is used by Oceanvolt. I don't like, or trust Oceanvolt so an alternative supplier would be great, if you know of one.

My plans are longer distance coastal travel and long term hopefully south Pacific.

Currently, I have 2 X 40hp petrol outboards that go up and down in a well, right through the centerline of each hull on a Schionning cat. They pull up clear of the water when not in use and have a fixed but adjustable angle to hull alignment. Currently maximum speed is 11-12kn at around 5,000rpm and cruise at 8-9kn at 4,000rpm with a respectable fuel use. I like the current speeds, faster is always better, slower... not so much but if it's only one of a few negatives it's not a deal breaker.

I'm just thinking out aloud at the moment, I don't know how serious I am at this point, but I'd like to know how good a fit EP might be for me. I'm looking at a Oceanvolt saildrive (because it seems to be the only one with servo- prop regeneration). Outwardly it appears a saildrive design would be suitable to be mounted with an "up/down & 360° rotation" that would be a system designed by myself, (unless something is already available).

• Is it ok to use a saildrive like this, I should be able to keep the head dry?
• Do these props have similar grip in the water to a full sized prop on an inboard?
• Is the ability to rotate the motors an advantage or to much complexity?
• Are there similar systems out there?
• Is 2 X 15kw electric motors enough?

TIA
Dave

[Pete7]

Dave, there are some posts by Adele about efficiency of adjustable blades on props to maximise the output of regen.

However, we already know that the ideal propeller shape for regen isn't the same shape for propulsion. Its one or the other with either regen or propulsion taking second place. You might look at the YT videos of Jimmy Cornell's failed EP cat which couldn't even heat food at one point despite 1.3kW of solar and 500w of regen whilst doing 8 knots. Boat made it to the Canaries, then turned around, went back to France and was sold. Think it had an OV propulsion system.

However, suppose you had a fixed propeller shaped for regen if that is the priority and could then be lifted into the hull out of the way reducing drag whilst sailing. Not a new idea and I think Beneteau have it on one of the 30ft performance monos.

Alternatively I saw this yesterday:

https://diverseps.com/product/retractable-drives/

This puts the motor were ever you want it and if stationary lifts the lot out of the way to keep the weed and barnacles from growing on it.

Pete

[Tupaia]

Originally Posted by Pete7

Alternatively I saw this yesterday:

https://diverseps.com/product/retractable-drives/

This puts the motor were ever you want it and if stationary lifts the lot out of the way to keep the weed and barnacles from growing on it.

Pete

Saw this on a Gunboat a few years ago. It spent more time out of the water getting it fixed or un-jammed than it did sailing.

Test your ideas by deploying your outboards as a temporary propeller the drag has a considerable effect on sailing performance especially on a cat less so on a mono where they are at or around hull speed.
A decent performance cat like yours should be using so little engine hours I can't see what would be the benefit of EP in your circumstances. As Jimmy Cornell discovered you will need a generator anyway,

[Dave_S]

Originally Posted by Pete7

Dave, there are some posts by Adele about efficiency of adjustable blades on props to maximise the output of regen.

However, we already know that the ideal propeller shape for regen isn't the same shape for propulsion. Its one or the other with either regen or propulsion taking second place. You might look at the YT videos of Jimmy Cornell's failed EP cat which couldn't even heat food at one point despite 1.3kW of solar and 500w of regen whilst doing 8 knots. Boat made it to the Canaries, then turned around, went back to France and was sold. Think it had an OV propulsion system.

However, suppose you had a fixed propeller shaped for regen if that is the priority and could then be lifted into the hull out of the way reducing drag whilst sailing. Not a new idea and I think Beneteau have it on one of the 30ft performance monos.

Alternatively I saw this yesterday:

https://diverseps.com/product/retractable-drives/

This puts the motor were ever you want it and if stationary lifts the lot out of the way to keep the weed and barnacles from growing on it.

Pete

Thanks Pete

I had a bit of a look for posts by Adele but couldn't find any. Is that how to spell her name?

The problem, as I understand it it on Jimmy Cornell's boat was the boffins at Oceanvolt had only tested in fairly calm waters and when it was in larger swell of open water the computer couldn't settle on a pitch for regeneration and the servo-prop shut down. That's the reason given in one blog, from my experience with them, the truth has probably been disappeared a long time ago.

Assuming they have sorted their problems with JC 's catastrophe, (hopefully we will see when La Vagabonde trial it on their Rapido 60). On my boat, I would hope that with two regeneration motors running it should bank better than 4.5kW at 10kn and 8kW at 15kn. A really fast Schionning without servo-props made 12kW at 20kn.

I like the look of that sizzor action retractable prop system. My outboards work by sliding the outboards straight up and down vertically through the bottom of the hull, I'll have to stick with that.

[Dave_S]

Originally Posted by Tupaia

Saw this on a Gunboat a few years ago. It spent more time out of the water getting it fixed or un-jammed than it did sailing.
Attachment 269391
Test your ideas by deploying your outboards as a temporary propeller the drag has a considerable effect on sailing performance especially on a cat less so on a mono where they are at or around hull speed.
A decent performance cat like yours should be using so little engine hours I can't see what would be the benefit of EP in your circumstances. As Jimmy Cornell discovered you will need a generator anyway,

I'm just exploring the idea, I think it's not great for me but I'm wrestling with a couple of changes and before I go to a lot of trouble to lock me into the petrol outboards I thought I'd have another look at EP.

One issue is sealing the outboard well in the boat with the engines up and a nice round hole is easier to work with than what I have.

Secondly the outboard props don't move enough volume of water to give the grunt in the marina without reving it's head off.

I would have a generator but not one capable of providing a motoring amount of power.

[Tupaia]

The best sealing I have seen on cat outboards was to create a Kort nozzle circular then add a square(ish) fairing to the lower half. The lip between the fairing and the nozzle opening creates a dam that prevent water entering at the front and back and the vertical sides seal against the sides of the well.


Excuse the drawing. Obviously the lower plate is curved and shaped to suit the hull. Not sure but may even improve slow speed steering.

[Dave_S]

Originally Posted by Tupaia

The best sealing I have seen on cat outboards was to create a Kort nozzle circular then add a square(ish) fairing to the lower half. The lip between the fairing and the nozzle opening creates a dam that prevent water entering at the front and back and the vertical sides seal against the sides of the well.


Excuse the drawing. Obviously the lower plate is curved and shaped to suit the hull. Not sure but may even improve slow speed steering.


Attachment 269398

The sealing system it came with had an aluminium plate attached to the skeg of the outboard. It was only fixed at one point so it could pivot in the water flow. It needed to pivot so it could match the angle of the hull when sealed (up) and be able to adjust to match the water flow when the outboard was down. The pivot was positioned such that there was more plate behind the pivot so in forward motion the the plate would self align with the water flow. However, in reverse it pivoted to it's maximum extension to block the water flow. Not a good system. This also meant when the outboard was up, the leg was still in the water.

My current cunning plan #632 is to have a semi circle shaped well and a seperate flap/hatch to seal once the leg is up enough to close it, down, then an over-centre lock to get the pressure required to make a seal as I want to pump the water out instead of carrying it around, the extra floatation won't hurt either.

Before doing this though, I need to be 100% satisfied with the type of motors I'm going to use.

[Chotu]

What exact outboard setup and props do you have that you are getting 11-12 knots at 5000 rpm and 8-9 knots at 4000 rpm??

What are the pitch and diameter of those props? How many blades?

Sorry I could not answer the thread question. However, the performance you have under Outboard is incredible.

[Adelie]

Originally Posted by Dave_S

Thanks Pete



I had a bit of a look for posts by Adele but couldn't find any. Is that how to spell her name?



The problem, as I understand it it on Jimmy Cornell's boat was the boffins at Oceanvolt had only tested in fairly calm waters and when it was in larger swell of open water the computer couldn't settle on a pitch for regeneration and the servo-prop shut down. That's the reason given in one blog, from my experience with them, the truth has probably been disappeared a long time ago.



Assuming they have sorted their problems with JC 's catastrophe, (hopefully we will see when La Vagabonde trial it on their Rapido 60). On my boat, I would hope that with two regeneration motors running it should bank better than 4.5kW at 10kn and 8kW at 15kn. A really fast Schionning without servo-props made 12kW at 20kn.



I like the look of that sizzor action retractable prop system. My outboards work by sliding the outboards straight up and down vertically through the bottom of the hull, I'll have to stick with that.

Adelie

A system that is going to be decent for propulsion and regen will use a Controllable Pitch Prop (CPP) with symmetrical blades, that is they are convex on both forward and aft faces. I don’t know how much twist the blades could have, probably the normal amount but that’s a question to ask the supplier whenever you get serious enough to talk to them.

The symmetrical blade will sacrifice some forward thrust efficiency (10%?) in exchange for vastly better regen (2x).

This is what OV did. The downside to the system is the expense and I believe they put the blade pitch motor in the pod which will be a maintenance nightmare in the long run.

If you really are interested in this you would want to talk to the vendors, there are a bunch of them in Europe where fuel has long been expensive so the added cost of CPP was worth it because of the fuel savings.

CPP combined with a hybrid system would increase fuel efficiency over one or the other which are each a step up from iCE-Fixed prop.

I have a list of Vendors somewhere, if you are serious about contacting them let me know and I’ll dig it up for you.

[Dave_S]

Originally Posted by Chotu

What exact outboard setup and props do you have that you are getting 11-12 knots at 5000 rpm and 8-9 knots at 4000 rpm??

What are the pitch and diameter of those props? How many blades?

Sorry I could not answer the thread question. However, the performance you have under Outboard is incredible.

They are both EFI BF40 4 stroke Honda's, not high thrust (I think HT were the 50 or 60hp and much heavier). I couldn't get 4 blade props at the time so they are 3 blade aftermarket props. They are Solas props, I "think" from memory they are just over 12" and 9"??? pitch but I might be wrong about the pitch. Max revs is 5,300 and max revs in Eco mode is about 4,100 (it will rev passed that but Eco mode switches off). I cruise just within the rev range of Eco mode and burn about 1.4lt per nm at 8-9kn. 4 blade would give me more grip in the marina but less speed and efficiency I believe.

I spent a fair amount of time calibrating the alignment with the hulls and trim and depth in water. Surprisingly both motors ended up towing in about 5° and shallow in the water flow for best speed, but I'm taking my toe measurements from some guestimates so I can't be 100% on the toe angle. The boat doesn't like running on one motor, so all these numbers are with both engines going.

The outboards slide straight up and down on two each Ronstan 32mm T tracks.

I hope to make the hulls a bit slicker so I'm hoping for better numbers, maybe a max of 14, but I could be kidding myself. The boat varies around 7,250 kgs +/- 250kgs dependant on crap on board and the hulls length/width ratio is 15:1, it draws 0.4m.

It used to have 2 X Yamaha 25hp, high thrust outboards. Flat out was 9kn, cruise at 6-7 and it burnt more fuel. At a wild guess, I'd say 25% more, but I've got no figures to back that up with. I don't know what props or revs etc they were.

[Dave_S]

Originally Posted by Adelie

Adelie

A system that is going to be decent for propulsion and regen will use a Controllable Pitch Prop (CPP) with symmetrical blades, that is they are convex on both forward and aft faces. I don’t know how much twist the blades could have, probably the normal amount but that’s a question to ask the supplier whenever you get serious enough to talk to them.

The symmetrical blade will sacrifice some forward thrust efficiency (10%?) in exchange for vastly better regen (2x).

This is what OV did. The downside to the system is the expense and I believe they put the blade pitch motor in the pod which will be a maintenance nightmare in the long run.

If you really are interested in this you would want to talk to the vendors, there are a bunch of them in Europe where fuel has long been expensive so the added cost of CPP was worth it because of the fuel savings.

CPP combined with a hybrid system would increase fuel efficiency over one or the other which are each a step up from iCE-Fixed prop.

I have a list of Vendors somewhere, if you are serious about contacting them let me know and I’ll dig it up for you.

Thanks Adelie
I've pretty much talked myself out of the EP, I just don't think it's a fit for me. It's a shame, it's an attractive thought. So no need for the contacts. I very much appreciate the offer.

It is interesting what you've said about the blades been convex on both sides they must look very odd.

[valhalla360]

It won't help with regeneration but there are electric outboards that should be a simple install on the same mounts as the current outboards. (Elio, I believe is one manufacturer)

15kw is about 20hp, so you are cutting your available power by around half. If you would be happy with 20hp petrol engines, it should be fine. Unless you regularly are running them at more than 1/2 throttle while docking, there is zero magic electric HP. Cruising at a steady speed takes a given amount of HP regardless of the power source.

In calm conditions running at 60-70% of hull speed, it's probably fine. If you are trying to push closer to 100% of hull speed, you may find you run out of power. More importantly, you will need a really big battery bank to put out 30kw for more than a couple hours.

As others have said, a prop optimized for regeneration isn't optimized for propulsion. On a big cat, it makes more sense to install some solar panels but that really only handles the house loads.

EP always comes back to how are you going to produce and store electricity. Do that cheap, light and compact and electric motors win every time. Problem is, that's not so easy to do.

[Chotu]

Originally Posted by Dave_S

They are both EFI BF40 4 stroke Honda's, not high thrust (I think HT were the 50 or 60hp and much heavier). I couldn't get 4 blade props at the time so they are 3 blade aftermarket props. They are Solas props, I "think" from memory they are just over 12" and 9"??? pitch but I might be wrong about the pitch. Max revs is 5,300 and max revs in Eco mode is about 4,100 (it will rev passed that but Eco mode switches off). I cruise just within the rev range of Eco mode and burn about 1.4lt per nm at 8-9kn. 4 blade would give me more grip in the marina but less speed and efficiency I believe.

I spent a fair amount of time calibrating the alignment with the hulls and trim and depth in water. Surprisingly both motors ended up towing in about 5° and shallow in the water flow for best speed, but I'm taking my toe measurements from some guestimates so I can't be 100% on the toe angle. The boat doesn't like running on one motor, so all these numbers are with both engines going.

The outboards slide straight up and down on two each Ronstan 32mm T tracks.

I hope to make the hulls a bit slicker so I'm hoping for better numbers, maybe a max of 14, but I could be kidding myself. The boat varies around 7,250 kgs +/- 250kgs dependant on crap on board and the hulls length/width ratio is 15:1, it draws 0.4m.

It used to have 2 X Yamaha 25hp, high thrust outboards. Flat out was 9kn, cruise at 6-7 and it burnt more fuel. At a wild guess, I'd say 25% more, but I've got no figures to back that up with. I don't know what props or revs etc they were.

Thank you very much for sharing that information. I was really curious because we have a very similar boat and a very similar outboard set up. And I see nothing like what you see for speed.

But I do see almost exactly what you saw with the 25 hp high thrust. I have twin 30’s.

I have 11” props with a 7” pitch. 4 blades. Plenty of low end power around the marina. Less fuel economy I think.

A while back on here I had a thread about this and it seemed like everyone was in agreement that the 11 inch prop was just losing grip on the water. But after reading your post, I don’t think they were right.

I have always felt that I ran out of RPMs before I ran out of power. Based on your post it looks like this is true. If I could pitch these up a little bit I could probably get better fuel economy. Thanks so much for sharing.

[Dave_S]

Originally Posted by Chotu

Thank you very much for sharing that information. I was really curious because we have a very similar boat and a very similar outboard set up. And I see nothing like what you see for speed.

But I do see almost exactly what you saw with the 25 hp high thrust. I have twin 30’s.

I have 11” props with a 7” pitch. 4 blades. Plenty of low end power around the marina. Less fuel economy I think.

A while back on here I had a thread about this and it seemed like everyone was in agreement that the 11 inch prop was just losing grip on the water. But after reading your post, I don’t think they were right.

I have always felt that I ran out of RPMs before I ran out of power. Based on your post it looks like this is true. If I could pitch these up a little bit I could probably get better fuel economy. Thanks so much for sharing.

Hi Chotu

I read halfway down P1 of the thread on your props so I may have missed some information later in the thread.

Here's what I understand, you have the largest diameter prop that will fit - 11" x 7" pitch props, you have no cavitation, the boat accelerates smoothly right through the rev range untill it hits the rev limiter prematurely.

That's pretty straightforward, you need taller gearing, I'd try 8 or 9" pitch in the largest diameter available. 3 or 4 blade, blade shape? I'm not sure.

Best to talk to Solas, they will sell you the right props.