Concerning feathered paddlewheels...

Here's some thinking displayed...

 

Low horsepower...

 

Here is that Agostino Ramelli planetary gear reading wheel...

 

Hi Fred,
I love your boat, looking forward to seeing it with the articulated wheels.

Hi upchurchmr,
He claims 30mph on less than 88hp.
The large square brown lump looks like an extension of the hull underneath the the diff.

http://www.youtube.com/watch?v=02DKzQFsgJU
http://www.youtube.com/watch?v=meDcNK0-tio
http://www.youtube.com/watch?v=upc7twfFCuM
http://www.youtube.com/watch?v=Wd-zjtScnaw

Comments from youtube.....

[""The boat displaces 2000 lbs and has a 2TC Toyota car engine from a 1973 Carina rated 88 hp at 6500 rpm. With this setup it tops out at 5800 rpm so it doesn't quite make the full 88 hp. It has only enough power to pull first gear. I calculated the paddlewheel has only 28% slip making it pretty close to the efficiency of a prop.

At low speed the twin rudders turn it pretty well. At high speed it makes broad turns; there is no keel. With the open differential, the twin wheels could be braked separately and the boat would steer very quickly.

The boat is still solid and running 30 mph 20 yrs after it was built.""]

 

SamSam,

I really like the "low powered" flywheels. I wonder what they would be like in person.
The car on barrels is "interesting" but not a direction I would go.

The reading wheel - looks more like the inventor was part artist and wanted to to show off his love of mechanics. The wikipedia article said one person criticised it as being too complicated - I would probably assume that was true, although I don't have an alternative suggestion.

I have a few projects to finish before I think about one for myself.

Number4

Looks like a workman like boat, but I remember an old ski boat from the 60's that had about 65 hp outboard, 16' length, 600 -800# hull, which ran 55mph. Nothing is the same but the paddlewheel seems to not really deliver the efficiency.

Interesting stuff!

 

"the paddlewheel has only 28% slip making it pretty close to the efficiency of a prop."

Many confuse slip with efficiency, they are not the same thing. In fact, real propulsive efficiency is always less than (100 - % slip ). For example, There could be a propeller (or paddlewheel) with a slip of only a few percent, and a propulsive efficiency well below 10%.

Generally properly designed propellers on displacement craft typically have propulsive efficiency on the order of 50% to 75%, and slip around 20%, more or less. Many misfit outboards have propulsive efficiency that is far lower than 50%.

 

.

I think this one might be as fast as the OP boat and it looks better. There's a car engine under the brown cabinet, the transmission sticks out at the back of it and then the drive shaft runs back to the differential, to which the paddlewheels are attached.

Captain Binckley


Here's another low horsepower paddlewheeler...



Stealth Houseboat...

 

SamSam,

Do you have a closer picture of the feathered paddlewheels on these?
You might want to take the houseboat to the Random picture thread.

 

I don't understand how there can be a slip of only a few percent but effeciency below 10%...? How is slip calculated?

With your articulated paddlewheel, I assume there would be an arm for each paddle...? Which way is forward? Would that wheel turn clockwise or counterclockwise to go forward? I would think it would be better to have tension on the arms instead of compression, as they could be made lighter then, but then reverse would be a problem and possibly the arms picking up trash too.

 

SamSam,
Looks like fwd is to the right to me and clockwise would be the rotation.
fredrosse writes .... "I expect a 20% increase in boat speed with the articulated wheels". I'm guessing that would require a great deal more than 20% increase in thrust.

 

"I don't understand how there can be a slip of only a few percent but effeciency below 10%...?"

ANS: Since we are talking about paddlewheels, I think the best analogy is perhaps an automobile tire on asphalt pavement, slip is very close to zero in normal driving, yet there is friction in bending the rubber tires, that is why they get hot with extended high speed driving. Under-inflate the tires, there is more flexing of the tires, still virtually no slip, but even lower efficiency. While this is not exactly the same as a paddlewheel in water, it illustrates how various parasitic fluid frictional losses can add up, independent of the slip.

The best example for an actual paddlewheel I can think of is by looking at extremes. My sidewheeler has floats that are 12 inches wide and 8 inches deep. I think many can visualize that if they were made the size of a postage stamp, they would slip excessively (near 100% slip), and not propel the boat. On the other side of extremes, the paddles could be made, say 120 inches wide, and slip would be very much reduced, probably to only a few percent, however when those long floats are pushed into the water, there is a much bigger parasitic loss in fluid turbulence, and when they leave the water, they will be throwing 10X the amount of water up to the air, wasting even more power. A reasonable compromise falls between the two extremes of no slip and 100% slip, and this reasonable compromise gives the best propulsive efficiency.

The same story can be put together for a screw propeller, just a little more complicated, as you have to twist your head sideways, but very similar principles.

 

How is slip calculated? ANS: The paddlewheel, or srcew propeller, would advance a certian distance in one turn of the wheel. In fact, the motion of the paddlewheel (or screw propeller) moves thru the water in the actual boat a lesser amount. For example, a ten foot nominal diameter paddlewheel, in one revolution without slip, would advance 3.14 x 10 = 31.4 feet per revolution. The real boat does not go so far in one revolution, say only 24 feet. The advance ratio is 24 / 31.4 = .764, or 76.4%. Percent Slip is defined as One hundred minus the % advance ratio, in this case 100 - 76.4 = 23.6 % slip.

 

"With your articulated paddlewheel, I assume there would be an arm for each paddle...?" ANS: Yes, same as the old drawing shown earlier on this thread.

"Which way is forward? Would that wheel turn clockwise or counterclockwise to go forward?" ANS: Boat forward is clockwise, putting compression on the arms that tilt the paddle floats.

"I would think it would be better to have tension on the arms instead of compression, as they could be made lighter then." ANS: Yes the arms could be much lighter in tension, but when the floats hit a submerged log or floating debris, that arrangement is very rigid, and something has to break. The design has these arms as somewhat flexable columns. In normal operation, they act as rigid columns, (actually connecting rods) but when they are seriously overloaded they can flex (think of an archer's bow) and allow some give to the floats, reducing the probability of breaking something.

The simple wheels I have now use fiberglass floats, strong enough for normal operation, but they break if I hit something, long before the collision would cause possible damage to the main wheel or engine. I have broken several of them already on the Delaware river, plus a few on Lake Winnapausakee. I usually have about a dozen spares on board, and if I run out of them I just have to go to the nearest cafeteria and grab a few more, they are lunch trays.

 

" (with 20% increase in speed, "I'm guessing that would require a great deal more than 20% increase in thrust." That is correct.

However a more distinct statement is the increase in Net Forward Thrust. To get a 20% speed increase in a slow displacement boat like mine, 1.2 squared, = 1.44, an increase of net forward thrust of about 44% is needed.

The non-articulated wheels enter the water at an angle, and leave the water at an angle, wasting thrust pushing water down, then raising water up. The articulated wheels are designed to avoid this pushing of water up and down, so more of the engine's available torque and energy can be directed to pushing the boat forward. Of course they figured all this out more than a century ago, and most old large sidewheelers used articulated wheels.

 

How did the new articulated wheels work?