Propellors?

[metalhao]

hi guys. in my design of a hydrofoil i decided to install a propellor. but was wondering whether a air-type or water-type propellors will be better. anyone got a clue?

[lewisboats]

Gotta know more...shape/type of hull...displacement at rest, intended purpose etc.

Steve

[metalhao]

oh, i'm doing a human powered hydrofoil. thus was wondering whether a air-type or water-type propellors will be better. like wondering about the advantages of each propellor over the other. but it seems that the weight difference is the only advantage.?

[metalhao]

guys. anyone know whether a water propellor is better than air propellor? or the other way?

[tuantom]

I'll take the bait.
I'm not a naval engineer by any stretch - but it seems fairly obvious to me that a water propeller would be the way to go. Have you ever seen an airboat where a water propeller can be used?

[Guest625101138]

It probably depends on design speed. I could do the numbers for you if you have a speed in mind and an all up boat weight.

At lower speed the water prop is probably better. Above about 5m/s the air prop will be better.

One of the things that comes into play is appendage drag. The water prop tends to be more disadvantaged by this.

If you want to do your own design then you should come to grips with JavaProp and JavaFoil. Just Google these. I can help you work though them if you like.

Other factors like shrouding of the air prop might be a disadvantage. On the other hand the inertia in air prop makes for smoother pedalling that increases biomechanical efficiency.

Rick W.