Prop for power, not speed?

[Diegoboy]

I am building a contraption that is going to have very little surface area in the water, light, and big. It's my rescue contraption idea. Frame is built, just moving to it's power plant.
What prop will give it power to push considering it's very light and high above the water?
It's going to be brushed, 550 motor, 7.2V

Thanks.

[saleens7]

the prop from my high wind had almost no pitch and is large in diameter...its meant to be a surface prop, but using it as subsurface and it has a LOT of tourque...

[Jeepers]

a guy here built a custom rescue rig, It used a Integy lathe motor (rc rock crawlers use them) and turned a 447/3blade, this thing would pull just about any thing. make sure you have alot of rudder though, as this one ended up with a 6"x3" rudder so it would turn when bringin in another boat.

[avengersteve]

what size shaft are you going to use? i have the stock prop from my atlantic harbor if you wanted to try it on for size.

[Diegoboy]

It's a 3/16 prop shaft on a .130 flex cable

[SJFE]

My next rescue rig is gona be outboard powered. Twins to be exact. I the maneuverability of thrust will make it a winner...Not to mention I'm gona use one of the 40 inch ebay cats...:D

[saleens7]

let me guess....twin 820 ob's?

[Doug Smock]

I am building a contraption that is going to have very little surface area in the water, light, and big. It's my rescue contraption idea. Frame is built, just moving to it's power plant.
What prop will give it power to push considering it's very light and high above the water?
It's going to be brushed, 550 motor, 7.2V

Thanks.

Take a look at the Dumas three blade scale props.
http://www.dumasestore.com/catalog/index.php?cPath=72
You don't want to use sub surface props on a submerged drive.

Doug

[Diegoboy]

I took this question to my LHS, they recommended a
#3115 (http://www.dumasestore.com/catalog/product_info.php?cPath=72_75&products_id=553) Bronze Propeller 3 Blade 1 3/4" Dia.

I bought it, do you think it's a good choice?

:confused:

[saleens7]

probably, those are used in scale boats wich usually run low rpm motors, but they push out a LOT of tourque...i think that one is used in the Mr. Darby tug...they use two of those props on it and it has enough thrust to tug around a rowboat with two people in it...and its a heavy tug too.....some end up weighing 50 pounds...

[Doug Smock]

probably, those are used in scale boats wich usually run low rpm motors, but they push out a LOT of tourque...i think that one is used in the Mr. Darby tug...they use two of those props on it and it has enough thrust to tug around a rowboat with two people in it...and its a heavy tug too.....some end up weighing 50 pounds...

50 lbs is just the ballast. LOL
I think that is a good place to start Diegoboy. Check your motor temp, those props can be "adjusted".

Doug