Electric motor question

[BigBeakie]

Originally Posted by cwjohm

I would use the standard Oceanvolt shaftdrive system that goes up to 40KW. I am not sure how easy it is to mate the Oceandrive shaft motors to a normal saildrive, and I have not heard of anyone doing that, but I am happy to be educated in this regard.

In regard to support in remote places, yes it is true that standard saildrives are more easily supported, but what about the electric motor. Oceanvolt have more remote support than anybody else. If I put some random electric motor in, I will have no remote support whatsoever.

I don't think you would have much of an issue with prop thrust symmetry. There are 2 sizes ( lengths) of propshaft struts available from Oceanvolt for the AXC series shaft drive motors, and by choosing the right length strut and the fore-aft location of it, you should be able to locate your AXC prop in the same position as the diesel saildrive, ie both prop depth and fore-aft position.

The motor is easy to locate sub-floor in the aft cabin and just use matching propshaft length to put the prop in exactly the same spot as the diesel saildrive. We chose to use the same size & pitch props for the electric and diesel, 3 blade Flexofolds, and they are in the same position, albeit the shaft angle between the two shafts is half a degree different.

[cwjohm]

Originally Posted by BigBeakie

I don't think you would have much of an issue with prop thrust symmetry. There are 2 sizes ( lengths) of propshaft struts available from Oceanvolt for the AXC series shaft drive motors, and by choosing the right length strut and the fore-aft location of it, you should be able to locate your AXC prop in the same position as the diesel saildrive, ie both prop depth and fore-aft position.

The motor is easy to locate sub-floor in the aft cabin and just use matching propshaft length to put the prop in exactly the same spot as the diesel saildrive. We chose to use the same size & pitch props for the electric and diesel, 3 blade Flexofolds, and they are in the same position, albeit the shaft angle between the two shafts is half a degree different.

Yes, i understand. Claude maintains that the sd15 saildrive will drive the boat with at least 5Kn boat speed and given the the main use of the motor is motor-sailing this should be sufficient. He is going to provide the calculations supporting this. In this regard I remain skeptical.

[Tupaia]

Just interested in your reasoning for wanting such a set up?

[valhalla360]

Originally Posted by funjohnson

Attachment 232132

Best I've seen is inboard rotating pods for a catamaran. A member on this site did a similar system using E-Tech drives, but before that, I saw this one from Green eMotion and it worked great. It's the way I'd go if I were going electric.

Unlike outboard motor style electric drives, they don't require nacelles that can pound in a seaway. They can also have longer shafts to get the prop way deeper. But like the outboard style, the drives have no drag or corrosion when lifted. And since you have no drag when they are out of the water, you can put a large fixed blade prop to regen as much as possible.

I know of a two companies that dwarf Oceanvolt for dealer support around the world that will soon offer saildrive electric motors over 15kw. Stay tuned for releases this summer.

Matt

I'm not sure that would be much better in a seaway. With a big prop, every wave is going to have a pretty good impact.

We had a sled for the outboard on our small cat and it was never an issue.

I know other designs where the outboards are mounted in a similar location but raise up completely clear. Never heard of them being a problem.

[Matt Johnson]

Originally Posted by valhalla360

I'm not sure that would be much better in a seaway. With a big prop, every wave is going to have a pretty good impact.

We had a sled for the outboard on our small cat and it was never an issue.

I know other designs where the outboards are mounted in a similar location but raise up completely clear. Never heard of them being a problem.

A sled isn't really needed with electric drives. Unlike an outboard with the driveshaft running the length of the strut, the motor is located in the base of the unit and any length strut is possible.

In the example shown, the lowest point of the props when retracted is close to 25" from the waterline. Not sure how every wave is going to hit them, but if it does, a small nacelles would work well to deflect any waves and still result in a ton of bridgedeck clearance.

When transverse folding drives are articulated down, they can rotate to a position much further outboard and get close to the position of inboard drives. And unless indented or cut away, the chamfered panels on modern cats would cause conventional folding drives to be closer to the centerline.

The benefit with conventional folding is if you hit something it will fold up.

Matt






Here are the fixed nacelles for a Seawind 1160 -




If you sail one, notice how the leeward fairing stays immersed the majority of the time. I would think that the drag from this would be almost as much as folding props on inboard driven boat.

The design for our 42' puts the pods 10" above the waterline using extra long shaft 25hp motors, but in doing so, we do not get the props deep and risk them popping out in a seaway.

[valhalla360]

Originally Posted by funjohnson

A sled isn't really needed with electric drives. Unlike an outboard with the driveshaft running the length of the strut, the motor is located in the base of the unit and any length strut is possible.

In the example shown, the lowest point of the props when retracted is close to 25" from the waterline. Not sure how every wave is going to hit them, but if it does, a small nacelles would work well to deflect any waves and still result in a ton of bridgedeck clearance.

When transverse folding drives are articulated down, they can rotate to a position much further outboard and get close to the position of inboard drives. And unless indented or cut away, the chamfered panels on modern cats would cause conventional folding drives to be closer to the centerline.

The benefit with conventional folding is if you hit something it will fold up.

Matt






Here are the fixed nacelles for a Seawind 1160 -

Attachment 232188


If you sail one, notice how the leeward fairing stays immersed the majority of the time. I would think that the drag from this would be almost as much as folding props on inboard driven boat.

The design for our 42' puts the pods 10" above the waterline using extra long shaft 25hp motors, but in doing so, we do not get the props deep and risk them popping out in a seaway.

Sure you can make the outdrive for electric longer but my point was the picture shown, they were fully exposed (when in the retracted position), so every time a wave hits, there would be a jarring force applied to the drive...especially with a large fixed prop. The response was to a comment that nacels create slamming. I don't see where the design in the picture would be much better for that purpose...just a different type of impact.

Drag is a different issue...if the nacel is dragging all the time, that's not a great design. The ones I've seen will be out of the water most of the time.

A retractable sled is a fairly simple fix that negates both the issues. Retract the sled and tilt the motor forward and there really isn't much of anything for waves to hit without hitting the bridgedeck first.

[smj]

A pivoting pod works well. These pictures show the up position using just the pod. The pod and motors can tuck closer to the bridgedeck with using partial motor and full pod tilt.