A strange prop design

[tom kane]

Some years ago I was shown a propeller fitted to a mercury racing motor by an owner with a collection of outboards.I did not get the time to discuss the prop with the owner and did not get info about it.I have often thought about it and wish I had followed up on the prop.Does anyone know anything about such a prop as shown in the drawing? The owner is not incapable of pulling ones leg. It could be capable of putting a load on a motor for test purposes.

[Frosty]

I would say, consider your leg well and truly pulled.

[kistinie]

Frosty, can you explain ?
Is this because in your eyes, at a first technical glance, you can see it is a joke, or because it is from the 60's, so, as is it is not used today, it must be a joke ?
Both will you say, i guess ;-)
Frosty, I do not have such technical eyes, you seem to have...so i cannot get, as fast as you, a conclusion.

I only can say, i noticed that NZ was a fertile country, for designing smart simple unique solutions in many domains, like boating, or ecological organic design.


KIWI prop using composite blades is an example

Many thanks for this input Tom

[Kaluvic]

I actually think I've seen something like that....cant recall where...but it does look familiar.
Not saying its efficient at all, but it doesn’t take much to create a differential in pressure assuming the grove is only on one side.

[jehardiman]

Are you sure it's not the other way around? I.e. the cavity on the back (fwd) side of the blade and the face (aft side) solid? It had some twist and an ogive section?

[tom kane]

It is possible I have shown the wrong surface position and I realised this when drawing the diagram.The prop was small maybee 8 inches and I think it would be possible to achieve 180 pounds of thrust. It appeared to be made of fine metal and was well engineered.

[jehardiman]

Yes, it could be a supercavitating prop, but at that size (8" dia) it would be for a high rpm, low torque motor. So it was for a little 2-cycle hydroplane?

[tom kane]

The motor would have been very high RPM and possibly direct drive or even geared up. It was wth a collection of other interesting old motors.About 30 HP range standard.

[thudpucker]

I 'See' two things there.
One is something similar to the Sail the Ocean Explorer guy (Jaque Costeau) had on one of his Calypso boats that looked like a tall fat shaft, but it was a wind foil.
This prop in Tom's post is probably a water foil also but the drawings don't show it well.

The Second thing was something I saw in the Air Force museum at the Wright Brothers section.
Those two guys built a Wind tunnel and experimented with air foils. One thing they learned was a Round cable had less drag and much less distortions in the wind than a flat or tapered strut.
Meaning anything besides 'round' tried to fly. So I think that drawing must be short a couple of details. Thats why we don't see it as anything beyond a joke.

[jehardiman]

Originally Posted by tom kane

The motor would have been very high RPM and possibly direct drive or even geared up. It was wth a collection of other interesting old motors.About 30 HP range standard.

Like a Quincy Looper Mercury?

http://www.quincylooperracing.us/



or a non-looper merc.

[powerabout]

Dunno
But a test prop looks a bit like a water jet impellor.
Merc ones looked like 2 dinner plates one large one small with the blades between them ( like 20 blades)
Merc had the in the 60 and early 70's bit dropped them, I dont know why.
OMC/BRP still have them
The engine will run to a set rpm at WOT and sit there.
You can make them from very low pitch props by welding a ring around the blades (like a kort nozzle) Merc had a service bulletin on how to do it.
We used to use OMC ones on Merc (V6 and sterndrives have the same spline)

A great tool for troubleshooting

[sandhammaren05]

Originally Posted by jehardiman

Like a Quincy Looper Mercury?

http://www.quincylooperracing.us/



or a non-looper merc.

I think the design could have been one of Popeye's earlier ones, he may have had in mind this outboard rather than Quincy machinery.