Design of variable pitch propellers? anybody got a clue?

[Freddy Lemieux]

I'm an engineering student and i'm pretty new to the boat building thing, and i've been trying to design a hub for a propeller which can change the pitch of the propeller to increace efficiancy of the engine. But, i'm not sure what to use for the variable pitch (gears, hydrolics?) and dynamic seals and finally as an actuator to control the pitch change from the boat? if anyone has any design drawings, pics, or ideas they will be much appreciated.
Thanx

[dionysis]

You have a shaft within a shaft, the inner one drives the propeller, the outer one moves in and out to vary the pitch. Linkage is pretty straight forward.

I hope this helps, cheers.

[Mark Richardson]

Hi fred, its Mark from your course, might not remember me....guess u beat me to it cos i was just about to ask the same question here!

maybe some people could post links to websites with diagrams of these drives? that would be really helpful.....

[Chris Rapson]

Try
http://www.kastenmarine.com/CPprops.htm
Michael Kasten is a big fan of variable pitch propellors.
I would realy like to know what advantage can be gained, particulary comparing the huge range of new and old fixed pitch propellors and gearboxes with a new complex setup.
I have built and sailed a boat (Hartley RORC 32 Ferro) with a small fixed pitch propellor and found it to be quite satisfactory.
I brought a boat with a folding propellor(Dufor 26) and that worked quite well also.

[Vahid mokhtari]

I am looking for :

1- how we select a propeller for a water vessel?

My water vessel specifications are:

Weight : 6000 Kg
Dim : L6.5 * W2.2 * H 1 (m)
Max water line : 0.48 m
Max speed : 0.4 m/s

Looks like the whole of Nottingham Uni has congregated to solve Middletons evil project. Try : http://www.mt-propeller.com/en/manuals.htm it's got detail drawings at the bototm of each manual. Luck and love to you all

[PauloT]

Hi, This remembers me the time I spent at UCL.

Try to find a book called "Marine Proppelers and Propulsion", writen in 1994 by J S Carlton, and printed by Butterworth Heinemann, I think it is not going to be difficult to find it at your main library.

To have a general ideia of how the system works check page 18, but if you need something more specific just tell me.

Take care

[Lew Morris]

there's nothing like a youthful, unencumbered, creative, approach....

[Freddy Lemieux]

God bless

I am trying to obtain a copy of Marine Propellers and Propulsion and have been unsuccessful at locating a copy. Does anyone know where I can buy one or is willing to sell me a copy?

Thanks,

[rcb]

Originally Posted by Freddy Lemieux

I'm an engineering student and i'm pretty new to the boat building thing, and i've been trying to design a hub for a propeller which can change the pitch of the propeller to increace efficiancy of the engine. But, i'm not sure what to use for the variable pitch (gears, hydrolics?) and dynamic seals and finally as an actuator to control the pitch change from the boat? if anyone has any design drawings, pics, or ideas they will be much appreciated.
Thanx

check out land and sea the have a torque shift propeller that seems to be what you are after in your design

[rcb]

check out land and sea torque shift propellers on the web it seems to be what you are trying to design maybe you can improve on theirs

[Jets]

Ok guys. Back to school. A variable pitch prop varies the pitch across the blade. A constant pitch has the same pitch across the blade. A controllable pitch prop allows the blades to turn within the hub.
Controllable pitch props require a large draggy hub and blades that have a lot of skew so that the load ahead of the pivot equals the load after the pivot. They are ideal however on turbine powered warships because of the narrow RPM range of the engines. The Lips props use rods to change pitch and VA-Tech (formerly Sulzer Escher Wyss) uses hydraulics with inner and outer shaft tubes for oil flow. These props are expensive and too fragile for small boats. It is better to use a 2 or 3 speed transmission as used in Weismann transmissions instead.

There are also "deformables" propellers. I dont remind where I saw them (perhaps on www.vripack.com, but the site is being redesigned) , but it was marine composite propellers structurally designed in such a way that when forces increase on the blades, the pitch flattens.

François