What size Prop to use

[Jimboc]

This is my intrim boat over the stern wheeler I am planning to build but this first one is an explorer to find out where to moor a larger boat later on. I am building a 28` trailable house boat, weight max 2.5 ton, Powering it with a 20 hp Diesel with hydraulic drivemotor to turn the prop. RPM of Hydraulic motor is max 470. (average say 300 rpm cruising), Hull speed aprox 10 mph. pitch required according to calculator is 35 so.. what size prop would I need to buy? any ideas? thanks
Jim

[gonzo]

What rating is your hydraulic motor. You will usually loose about 30% of the power. That leaves 14HP to move the boat. There is no way you will do 10mph. With luck you'll get 5.

[Jimboc]

Thanks Gonzo. I need a place to start and you have given me that. Really appreciated. I will work out my HP and obtainable speed accordingly.
Cheers
Jim

[mccaffrey]

Hey Jim,

I came across your post and although I cant provide an answer to your post, I'm doing a very similar thing to you only im in the earlier stages. Im thinking of using an 80 hp engine nd hydraulic system from an excavator ex120. Im just wondering how you worked out what size of drive motor you would use? Im very curious how you get on.. Good luck

Ian

[Jimboc]

Hi Ian.
Thanks for the reply.
I too am only in the planning stages but as I build eathmoving equipment from scratch I have a reasonable idea of how to power machinery with hydraulics. My idea is to use a hydraulic motor that is used to power a posthole borer. With a double controll valve I am able to operate the hydraulic joystick steering from one and the Forwad/ Reverse on the other.. It will have the torque and the strenght to push a flat bottomed scow hull. I am not looking at water skiing or even much speed. THAT is not the idea at all. I build a 4wd Eathmoving machine called the OZtrac and its powered by a 18 hp Vanguard which drives the Hydraulic pump. This power plant is fufficent to push the machine along at about 10kpm and also has enough power to load a 1/3 meter bucket and run a small backhoe with an 2.4 reach and breakout force of 2500kgs. Thats is where I am getting my ideas from. I can see all the purestes sitting there now shaking thier heads but I learn everything by trial and error. This House boat will be no exception.
It took a year to get the OZtrac right but in the finish its world class so now on to the next challange. l Good luck mate and If I can help anytime let me know.
( Hydraulic pump, Control Valve & Post Hole borer motor are all available from Bare-Co... I can get them for you or any tractor parts supplier will have them. )

Cheers
Jim

[TollyWally]

"I can see all the purestes sitting there now shaking thier heads but I learn everything by trial and error. This House boat will be no exception."

I bet it turns out just fine in the end.

[Jimboc]

Hell no we need them... It makes us feel good when we prove them wrong!!! AGAIN!