Podded propellers for low power range

[ANAND SANKAR]

Im working on a pleasure boat design of 14 m length, since space is a major constraint i thought of providing podded propellers which is an efficient propulsion system and does not require a seperate steering gear and hence reduce space.
Where can i find podded propellers with small power from 20-30 KW?

 

[Joakim]

Where can i find podded propellers with small power from 20-30 KW?

Yanmar has a rotating saildrive. I don't know, if you can find it on their site already, but it was at METS and has already been used a couple of years in Jeanneau sailboats.

It has quite small lateral area and may not work well without a rudder. At least propeller thrust is needed for steering at low speeds. It was introduced for joystick steering system. Not for replacing a rudder.

 

[mydauphin]

Some kind of rudders or rudder like keel is need otherwise boat will crawl sideways. You may have thrust but boat will get turned around by wind.

 

[Mr Efficiency]

I can't imagine a lot of applications in this hp range where an outboard motor wouldn't do the job, a whole lot cheaper, and with the option to raise the drive when needed.

 

[ANAND SANKAR]

I can't imagine a lot of applications in this hp range where an outboard motor wouldn't do the job, a whole lot cheaper, and with the option to raise the drive when needed.

The design is actually a steel houseboat with two tiers and the total weight and power required was estimated as 50 tonnes and 38 KW (at speed of 6.4 knots) respectively
i can provide a propeller diameter of 750 mm(max) if i use two inboard engine of 20KW and the usual shaft and propeller assembly. But if i provide outboard engines, the maximum diameter available at 20 KW is only 250-350mm, which would increase the overall power required drastically to 75KW.

 

[Joakim]

I can't imagine a lot of applications in this hp range where an outboard motor wouldn't do the job, a whole lot cheaper, and with the option to raise the drive when needed.

All sailboats and similar true displacement motorboats are such applications. Sure they can use an outboard and it is much cheaper, but with many drawbacks like poor reverse, fuel economy and charging. Also they are noisier and in many designs the propeller will be out off water in heavy seas.

 

[Mr Efficiency]

The design is actually a steel houseboat with two tiers and the total weight and power required was estimated as 50 tonnes and 38 KW (at speed of 6.4 knots) respectively
i can provide a propeller diameter of 750 mm(max) if i use two inboard engine of 20KW and the usual shaft and propeller assembly. But if i provide outboard engines, the maximum diameter available at 20 KW is only 250-350mm, which would increase the overall power required drastically to 75KW.

But you said you wanted pods ? Pods would worry me if there is a strong risk of grounding, unless there is some other grounding protection in play, to keep them out of strife.

 

[Mr Efficiency]

All sailboats and similar true displacement motorboats are such applications. Sure they can use an outboard and it is much cheaper, but with many drawbacks like poor reverse, fuel economy and charging. Also they are noisier and in many designs the propeller will be out off water in heavy seas.

Of course it depends on the application, but where once there was little use for outboards, they are now an option in some cases because of four-stroke economy, extended drive legs, better gear ratios, more suitable props, etc.