Magnetic Drive

[valhalla360]

Originally Posted by NahanniV

A rim driven propeller could have no penetrations.



The magnetic rotor ring around the propeller tips is driven by a stator inside.

Cheers,
JM.

Of course for primary propulsion, you are essentially building a jet drive. Small jet drives are known to be very inefficent and you have to create a space within the hull for what is probably a 1' diameter pick up tube.

The other magnetic coupler doesn't look like the output side is designed for salt water immersion.

If you really want to eliminate holes in the hull get boat designed for an outboard. That's what we have and it works great.

[Ukeluthier]

Originally Posted by valhalla360

Of course for primary propulsion, you are essentially building a jet drive. Small jet drives are known to be very inefficent and you have to create a space within the hull for what is probably a 1' diameter pick up tube.

The other magnetic coupler doesn't look like the output side is designed for salt water immersion.

If you really want to eliminate holes in the hull get boat designed for an outboard. That's what we have and it works great.

On the contrary, such a device could readily be mounted in a conventional prop aperture at the aft end of the skeg with a skeg-hung rudder. Hell, it could even be mounted in an aperture in the rudder itself, where it might offer great advantages for maneuverability, especially in reverse. The intake water doesn't need to be ducted... it can simply flow in on either side of the skeg.

Outboards as sailboat auxiliaries have many known disadvantages, especially if they must be transom-hung, off center (I know, I've had both inboard and outboard auxiliary boats). If you try to motorsail with the motor on the windward side, your prop may be out of the water much of the time. Similarly, making progress to windward in a bad chop that causes the boat to hobby-horse is problematic. Besides all that, there is nothing uglier than an outboard hanging off the transom of an otherwise beautiful sailboat.

A rim-driven prop mounted in an aperture would also likely be very immune to fouling by dropped lines or prop warps.

[motion30]

a regular straight inboard is a very low maintenance system. Inexpensive and efficient system. It seems like a magnetic drive with ads cost and maintenance do that

[valhalla360]

Originally Posted by Ukeluthier

On the contrary, such a device could readily be mounted in a conventional prop aperture at the aft end of the skeg with a skeg-hung rudder. Hell, it could even be mounted in an aperture in the rudder itself, where it might offer great advantages for maneuverability, especially in reverse. The intake water doesn't need to be ducted... it can simply flow in on either side of the skeg.

Outboards as sailboat auxiliaries have many known disadvantages, especially if they must be transom-hung, off center (I know, I've had both inboard and outboard auxiliary boats). If you try to motorsail with the motor on the windward side, your prop may be out of the water much of the time. Similarly, making progress to windward in a bad chop that causes the boat to hobby-horse is problematic. Besides all that, there is nothing uglier than an outboard hanging off the transom of an otherwise beautiful sailboat.

A rim-driven prop mounted in an aperture would also likely be very immune to fouling by dropped lines or prop warps.

If I understand correctly, the device shown requires the actual drive on the outside of the ring but protected from saltwater. You could build some sort of large bulb outside the ring to hold it I guess but now you create a lot of drag.

If you go electric drives, I have seen bolt on drives but haven't heard good things about the reliability and you are still bolting something thru the hull.

I agree. Strapping an outboard on a boat not designed for one is a bad idea. That's why I suggested getting a boat designed for use with an outboard.

[Ukeluthier]

Nope, the rim IS the drive. It contains the stator windings (one half of the electric motor). The permanent neodymium magnets (the other half) are in the gold ring surrounding the prop blades. You would need some sort of streamlined toroidal housing, but it needn't be significantly bigger than the drive shown. The only hull penetration would be for the wires, and even these could be encased within the skeg/housing.

[valhalla360]

In that case we have wandered off into electric propulsion, which has proven itself so well on cruising boats (not).

While closer to the request, you still need a hull penetration for the electric feeds and you need a way to securely attache the unit (likely thru bolting into the hull). I've seen bolt on pods that effect the same thing if the goal is an electric drive.

[zerompg]

Just a newbe here but these look so cool.

Torquejet

On a Cat with two, you just eliminated 2 diesel engines. Replace their weight with batteries and keep your Genset as a backup for elect.

Now only one diesel instead of 3.
For much of your motoring it's elect, quiet and gas free, add more solar.

It would appear that the hub-less mag driven prop would be very efficient and maybe safer over rope and debris..

Just thoughts from a newbe, but I'm hoping they bring the tech up enough this is possible in 4 years

[St. Elsewhere]

Magnetic Drive solved a problem for me years ago. It was not a propulsion application, it was a sea water pumps. Conventional pumps, with a motor and stainless steel shafts were prone to seal failures. Stainless steel corrodes when exposed to stagnant sea water, and this caused frequent seal failures. Since using mag drive pumps, I have had no pump failures. I am using them in cooling systems and a bait tank.

[SaltyMonkey]

I think it might set off floating ww II mines.

[IdoraKeeper]

Originally Posted by SaltyMonkey

I think it might set off floating ww II mines.

This exactly my concern, if the mines didn't get you then it would likely attract containers...it would swing the compass and last but not least....attract sharks!😈

[Ukeluthier]

Originally Posted by valhalla360

In that case we have wandered off into electric propulsion, which has proven itself so well on cruising boats (not).

While closer to the request, you still need a hull penetration for the electric feeds and you need a way to securely attache the unit (likely thru bolting into the hull). I've seen bolt on pods that effect the same thing if the goal is an electric drive.

While pure electrical propulsion isn't ready for prime time in cruising boats mainly due to limitations in battery technology, there is no such limitation for diesel/electric hybrids that don't rely on a huge battery bank. A big advantage would be that the unit could be driven from either the main propulsion diesel or a genset.

As to attachment, the logical approach for a fiberglass boat would be to have the housing molded as a unit with the skeg or whatever part of the boat is the logical mounting point. The electrical lines could then be all internal.

Not saying that such an installation wouldn't require some outside-the-box thinking or very sound engineering, but it appears do-able and more practical than a magnetic drive with a conventional prop.

[zerompg]

Wouldn't this just replace the sail drive and motor in one step?



I drive a Nissan Leaf hence moving to all electric is more a shift in mindset than impossible.

[Juniper]

Originally Posted by zerompg

Wouldn't this just replace the sail drive and motor in one step?



I drive a Nissan Leaf hence moving to all electric is more a shift in mindset than impossible.

Where do you get those, and how much do they cost, and how much power?

[zerompg]

I have no idea on prices, but they could be mounted in a number of ways. Also the drive could re-gen under sail.

Here's the site I found the mounting, no it not in Eng.

Hennegat Einbausatz - Elektrische Bootsantriebe - Manövriersysteme - Elektobootsmotoren - Bugstrahlantriebe - Heckstrahlantriebe - Elektrische Außenborder - Thruster - E-Motoren für maritime Anwendungen - ROV -Tauchboot -

[Stumble]

Doing this with a diesel-electric would work fine. It would cost a little bit in efficiency, but would eliminate some thru hulls.

The downside to me is you go from three diesels (2 drive 1 generator) to two generators (drive and house) with the drive motor needing to be much larger than the old drive motors... Frankly I don't think the system works very well, but it does have some advantages. Trying to run this off batteries just doesn't work, you need too large of a battery bank for real run times.