building a prop

[aojesus]

Somehow our mechanical crew at the shop got entered in a boat race in two weeks. The rules state we have to build the hull ourselves and it has to be human powered.

Our engineer came up with a 8' wide by 16' long pontoon concept. There will be three people on each side pedaling a shiftable chain & sprocket drive line.

The engineer calculated the boat and riders will weigh roughly 2000 lbs.
He also calculated the pedalers will generate 2 hp., 470 RPM's through a 7:1 ratio.

Now we have to figure out what size/style/pitch/rake blah blah blah prop to build. Does anyone have any recommendations?

[Skoontz]

Hook up with Ron Hill. He has made some props for some of the solar powered race boats pretty successfully. If he is too busy, call
John Wayne Janaky, DAH, Pro-Pellers, www.dahpropellors.com.

John will probably get a good chuckle out of it, then most likely dig in and love the challenge.

[johnsonm50]

Cool challenge, Id look outside the box.. electric outboard prop, old weedless prop or even a car radiator fan. This would likely call for a prop favoring diameter over pitch with alot of blade area, at low RPM youll need it. The propshaft might be the key to this.. how bout a tubular shaft with a pin or 2 that can readily accept different props set up with a shaft to be pinned in? Good Luck, sounds like fun. PS. Id also get that water-bourne asap to test and advise the peddlers: itll be like biking uphill against the wind - in the rain.

[sam]

I'd recommend a paddle wheel over a prop

[bh/]

I'd recommend a paddle wheel over a prop

In 1845 the British Admiralty conducted a tug-of-war experiment with two sisterships equipped with identical steam engines. The screw propellor equipped HMS Rattler handily pulled her sister, the paddle wheeled HMS Alecto astern at 3 knots. This experiment convinced the Admiralty , and proved to the world, [save for Sam ] that screw propellors were superior for marine propulsion.

That said it would be easier to build and tune a paddle wheel, but you still have questions of diameter, rpm, and number, area and shape of the blades. Or I would just borrow a prop from an electric trolling motor, and play with the gear ratios.

2000#,
-how big are your peddlers, ???

-will this boat be a 'lay-down',

[sam]

Brian, the power and weight of those boats was higher. I never said it was better for all boats. Haven't you seen the eggbeater outboards and wondered why they aren't more popular?

[aojesus]

2000#,
-how big are your peddlers, ???

-will this boat be a 'lay-down',

Brian,
We are all very slender and small framed. As you know, I am built like a jockey from the horse races. If you lined us all up side by side we would look like 6 needles from a bearing. I am assuming the weight comes from the boat.

Last year we entered a cement boat. It was a pontoon design made of foam and sprayed with stucco. We had six rowers. We were the first ones to cross the finish line in last place.

I do appreciate the input that has been given. I too, was leaning towards a paddle wheel but my doctorate degree is not in engineering.

[aojesus]

In 1845 the British Admiralty conducted a tug-of-war experiment with two sisterships equipped with identical steam engines. The screw propellor equipped HMS Rattler handily pulled her sister, the paddle wheeled HMS Alecto astern at 3 knots. This experiment convinced the Admiralty , and proved to the world, [save for Sam ] that screw propellors were superior for marine propulsion.

Hey Brian,
Your wife showed me pictures of the expeirment! It was cool seeing you on the bow of the prop driven scow with your sword high in the air!


Disclaimer: I am just playing with Brian. He is a tremendous friend whom I have a great deal of respect for.

[25xs]

Think "Hobie Cat" and use the biggest diameter prop you can...

Your pontoon boat should look as much like a Hobie Cat sailboat hull as possible... Pointy on both ends, tall/skinny logs, rudder steering.

Your propeller should be very large diameter and low pitch. Thinnest blades that don't bend under your predicted load.

Get a 5-blade sailboat propeller from a bronze propeller repair shop down there along the coast(s) of FL. Electric trolling motor propellers are out of the question with too small of diameter. Would require gear ratios pretty high to spin them fast enough with human power.

Here is good reading on building/design of electric boats which should be helpful. www.rayeo.com

Tom Brockmeyer
Buford, GA

[Skoontz]

Brain fart, brain fart!

We just came off the lake from testing, and, low and behold, what I saw....Hobie Cat, an old tiny sail boat manufacturer up in Oceanside, Ca. has a fairly new product that many lake goers are buying. It is, a kayak, that you can attach outriggers to for sailing, but, here's the kicker.

It has a tiller handle rudder, and bicycle pedals to drive a foot driven flippers like a fish uses.

Since this apparatus is sort of what I'm envisioning you are building, google Hobie Cat, go under the kayak button and check this thing out.

Pretty innovative if ya axe me.

The other thing I was thinking is, how about an old electric fan blade, and double it up if you need more strength? You may even be able to hammer a cup into it if ya need one....

[Kev43V]

Cool project!
I have to wonder why a pontoon design was chosen? It just seems to me that they require huge amounts of horsepower compared to other hull designs.

[aojesus]

I am not sure why we are doing pontoons two years in a row. I agree that there may be faster designs.

The original drawing had two props that were around 14" each. Since they decided to do props I talked them into one prop and am leaning towards a clover leaf type blade.

I will try to dig up some pictures of last years yacht and will take a few of this years creation.

Thanks for the input!

[david bryan]

paddle boats

we tryed this one 16 inch pontoons out of ply wood coud not get the to potkers in the front to move to the back

[aojesus]

almost done

We have the frame work almost complete. The prop is well on it's way to being complete. Our guy Tony can't wait until it is done.

[25xs]

Nice! Here are your crew hats. ...and that prop? Wow.

Looks like you're taking it up a couple notches from last year!?

I don't recognize that R&D section of Dewald's shop... And I've not known them to wear hardhats prior to this prop job!

Here are your hats... Get them ordered now: http://www.coolcostume.com/subcat_re...ry=Hats-Tiaras