Why no rotary engines?

[capz]

You would think there would be a market niche for the rotary in boating. Wouldn't a boat builder love to put these little lightweight monsters in their bilges? One argument I've heard is awful fuel consumption at low rpm's. Pushing a boat through water is just too much work. But once on plane, is it that much more work than pushing a car through air?

 

[fwebster]

Horrible efficiency and extremely low torque. If you could twist 'em up and leave them there, they might be ok, but boats just ain't made that way.

 

[Southpaw II]

The most efficient marine propulsion, especially for heavy loads, is low rpms, and lots of torque. Fuel efficiency is a more paramount concern these days than ever before. Oh yea, keeping a boat on plane takes lots of power. And, boats can't coast downhill.

 

[dpmulvey]

It's been tried. Just not enough power to drive anything large though.

http://www.atkinsrotarymarine.com/

The military experimented with rotaries for a while. I don't know what ever happened to the project. I do recall the concept was to add rotors as required to increase HP.

 

[sebagoman007]

Frank's right, you have to wind the wee out of one to make any power, and the fuel economy is pretty awful. They're relatively loud, too.

Mazda did win the 24 Hours of LeMans a few years back, as I recall. Thumped the competition so soundly that the governing body quickly banned them.

Now if you were looking to build a specialy vessel for high speed Banzai runs, that might be another story...............

Cheers,

 

[fc3]

That weird combustion chamber shape provides a massive quench area, which kills thermal efficiency. The physics of the engine is inherently inefficient.

 

[Henry Boyd]

The most efficient marine propulsion, especially for heavy loads, is low rpms, and lots of torque. Fuel efficiency is a more paramount concern these days than ever before. Oh yea, keeping a boat on plane takes lots of power. And, boats can't coast downhill.

An example for you; A diesel that would be used for say a containership is generally rated between 85,000 and 100,000 KW (KW x 1.341 = HP). These babies are optimized to run at between 104 and 106 RPM. Fuel consumption is measured in tons per day.

Henry

 

[JediJD]

That weird combustion chamber shape provides a massive quench area, which kills thermal efficiency. The physics of the engine is inherently inefficient.

+1 I vaguely remember my stepfather working for the Navy in Panama City on the Wankel project...probably thirtyfive years ago. I pretty clearly remember your post being a nearly direct quote when I asked him about it years later.

The advantage of Wankel was the small size and thus an excellent power to weight ratio. The disadvantages were lack of torque and relative fuel inefficiencies. It worked great in my 1979 Mazda RX7...imagine not so in my 240 SD pulling skiers.