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Gasoline powered Tugboat

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1967Brutus:
Since most likely in this section there is the most experience with propulsion systems on tugboats, I'd like to ask you guys:

For a 105 mm diameter fourbladed prop in a tugboat, what would be the expected thrust at a given amount of power, and what kind of RPM would I be looking at? Does anybody know if there is this kind of info availlable in for example tables or online propcalculators or such?

Akira:
You have listed the diameter of the prop, but other factors need consideration. 1) the shape of the prop, 2) the pitch of the prop, the operating rpm of the prop. I'm not a naval engineer so there are probably more factors involved. %)

1967Brutus:
That's the thing: I actually AM a naval engineer, and I do know what factors are in play, but...


I cannot give a pitch, because it is a controllable pitch propeller (4 blades), and I do not know an RPM, I only know that I most likely have 80 Watt availlable at somewhere between 1000 and 1500 RPM.
So I need "general propeller data" to be able to make an estimate on the eventual reduction ratio, IF needed...

If anything else fails, I would be interested in for example, people that use a 4 bladed 105-ish mm prop and ever have measured, to hear their ree running and moored shaft RPM and Watts (Volt x Amps)

tonyH:
I think you could be better off by reversing the matter and using old propellor design formulae which seem to be simpler.
You'll have to choose a series of discrete pitches covering the range you're working in and you should get a graph.
Good luck anyway :-))

1967Brutus:

--- Quote from: tonyH on December 13, 2023, 05:20:52 pm ---I think you could be better off by reversing the matter and using old propellor design formulae which seem to be simpler.
You'll have to choose a series of discrete pitches covering the range you're working in and you should get a graph.
Good luck anyway :-))

--- End quote ---


That is exactly what I intend to do, because I am aware that a controllable pitch propeller does not have a fixed set of parameters... IF ONLY... If only I could find propellerdata, and I seem not to be able to find that.
All I see is propcalculators that are laid out to find a prop for a boat and installed power, but I want it the other way around: I want to find a power and RPM for a given prop. The imput fields of those prop calculators however do not allow the search the way I want it. So I am a bit depending on those of you that have measurements done on their props, so I can collect data and construct a graph.

I have contacted the original manufacturer, Raboesch, which still exists and even is located in my home country, but I have not yet heard back (sent my question Sunday evening).

I am at sea right now, but if I haven't heard from them by the time I get home, I'll either call them or even visit them (they are about 100 km away from me).

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