50' sternwheel design

Hi Guys,
Need some feedback about a boat I want to build.I have always love the classic lines of a sternwheeler. I also won't own a boat that won't do at least 20 mph. Ive been thinking about this for over 30 years. That's why the scanned attachments are of ratty pages (lol). I am planning on plywood / fir pontoons. This will be a wood/epoxy vessel.
I will try to anticipate some of the odvious questions. Why a cat (pontoon design?
1. To provide a free flow of water to the wheel.
2. To provide stability for what could be a top heavy design ( most sternwheelers are tall vessels)
3. To provide bouancy aft to help support the wheel structure.
4. The longer the hulls, the higher the hull speed I can get without having to plane. (these are shown at 2' x 3' x 50' if memory serves me right)

The questions I want answered are.
1. How much power to get to my 20 mph?
2. What would the "hull speed" of the boat be?
3. Are the lines "pleasing"?
Any and all comments appreciated and please ask and questions ya have. thanks

 

Perhaps you have a solution for manuevering, but judging from your drawing and what you have said so far it seems that it would be difficult to steer with the hull all the way along the side of the wheel. One solution might be to have two wheels which could be counter rotating or rotating at different speeds to provide steering.

 

Hull speed = 1.3 * sqrt LWL so at 49" lwl 1.3 * 7 about 10 kts.
I have see the fomula very from 1.2 - 1.5, I think the varince is due in part to variations in wetted surface and hull cross section. it ma also be due to my faulty memory. or X * sqrt lwl in feet = kts Y * sqrt lwl meters = KMPH, and Z * sqrt lwl in feet = MPH so I guse you can look it up.


for looks, try a smaller wheal, or a bigger house / longer wider boat.

 

Doing some rough estimating you have about a 10 ton ship, assuming the hulls draft about a foot about with a full load. It takes a great deal of power to move this mass over the plane threshold, which starts around 1.5 speed/length ratio. With little bearing area aft, she will try to squat bad at those speeds.

As far as looks, you want some sweep in the sheer, a complimentary and similar sweep in the roof line of the main cabin and pilot house, plus some shape to her plan, so she does not look slab sided. The pilot house seems small to me and could use some visual tricks to lower its height a bit, maybe additional roof crown will help. The overall effect of the tallness can be visually lessened with a bulwark, maybe a cove stripe or other artistic trick. The wheel does appear somewhat large and you will want two, noting they handle like a tank, literally and bow thrusters would be a very good idea.

I would also consider hanging the wheels out aft of the hull, instead of between them, hung on brackets, like the big boys. This will give you a lot more cabin volume to work with. As it is now one third of the vessel is occupied by the wheels. Possibly twin exhaust stacks behind the pilot house. These boats also had a forward loading ramp and fancy hand rails with lots of decorative trim or gingerbread which can help in the illusion of a riverboat.

The details in the type of boat you are trying to create will sell the look, or break it, depending on how well you can emulate these vessels. Start close examinations on pictures of other river boats and find the details that make them a river boat, then incorporate these elements into the look of your yacht. This will not help with the structure, propulsion, electronics, etc., but it will look like a river boat.

 

Forget about power - you'll never attain that speed with a paddlewheel of any sort. To calculate the speed you first determine the circumference of the "wheel" (looks like about 16' diameter in this case X 3.1415 = 50') times the efficiency (assume best case scenario of 60% so = 30') to get the real distance the wheel will travel through the water - about 30 feet per revolution. Now find the number of feet the boat will have to travel per minute to do 20 mph - 1,760 ft/min. Thus the wheel will need to turn 58.66 rpms. With a 16 foot diameter wheel. No!

Sorry.

 

thanks for the responses

I want to thank you guys for your responses. I also want to address some of your concerns.
Gilbert, This boat would be built as a mule to test various different gearing and rudder options. A twin wheel setup was one of them. The rudders are to be aft of the wheel.
Erine, I think that when ya calculate the hull speed of the vessel you have to use that formula on each of the hulls, (2' x 50' ) not on the entire struture and the more complete formula uses a multiplyer for the beam/ legnth ratio. the 1.3 commonly used is the l/b ratio for a "standard boat". I'm uncertain about that, that's why I asked.
Hunter, I worked out the weight using Gougeon systems for estimate at 15,000 lbs. The idea was to keep it as lite as possible. I couldn't agree more about the need for sweep in the sheer and cabin lines. I've drawn about 20 or 30 of these things and to make them look right, sweep is a must. Some I have included sweep in, some I haven't But I agree that it really makes them look better. This was the easiest of my drawings to scan so that's what I used to give an idea of what I had in mind. As to the large wheel.I think we all agree that every boat is a compromise. One of the compromises in a sternwheeler is the size of the wheel. Because of the geometry involved in the angle of entry of the blades into the water, the larger you make the wheel the more efecient it is. The more time the wheel spends pushing water in the direction of travel and the less it spends pushing water down on entry and lifting it on exit the better off you are. An 8' wheel might look better. But if you have the wheel immersed 1' deep, it will spend more time pushing water up and down than it will pushing it back.as for 'hanging it off the back" that's the prefered method, but it requires a large structure to do so. It also leads to balance problems. In a mono hull sternwheeler, it becomes a a real design effort to draw a stern with enough bouyancy in the stern to float everything and still allow a smooth flow of water to the wheel. In the steam boat days, you had a lot of heavy equipment that you could use to ballance the boat. The rounded sterns also limit the speed boat. Ya want to talk about ugly stern squat. Ive seen sternwheelers over powered to the point where they approached planing. As the bow lifts, they bury the wheel and things break. I even knew one guy with a 120' sternwheeler that had been a comercial towboat . He actually put a set of 4' x 10' trim tabs on the stern to provide lift. Of course, all he did was starve the wheel of water when he had any speed. And then he accidently ripped them off and almost sunk the boat when he tried to reverse and piled a bunch of water on them.
The ginger bread would be added after the boat 's design things were finalized. that stuffs also hard to draw (lol).
Artemis, I did that math in about 1975. I have a large chart that I made then that shows all wheel sizes from 8' to 30' and the various rpm's that the wheels will have to turn to get there so I could look at the gear redux needed. I am aware of the challenge and I readily admitt that you may be correct, but , if it was easy, everyone would be doing it and a guy has to have a hobby.
Thanks for your input guys

 

One of our local tour boats looks and feels like a sternwheeler.... except it has a pair of props buried two feet under the fake wheel. Not nearly the same thing, but 90% of the passengers are either too ignorant of boats, or too drunk on Canadian beer, to notice!
I think you'll have a really easy time pulling 10 mph; 20 is going to be insanely difficult. At 60 rpm, roughly the speed artemis estimated for 20 mph, the blades of that 16' wheel are doing fifteen metres a second, and the force on the blade tips from centripetal acceleration alone is five times the force of gravity. And that's in air, before it even touches the water. How wide is the wheel? Say your blades are 12' wide by 6" high; at 60 rpm that's a hair over nine tons of force on each blade in the water! This is a big part of the reason there are no fast paddlewheelers. A paddlewheel is essentially a drag device; a propeller is a lift device- much more efficient.
So if you want the style of the paddlewheeler, which I think would be seriously cool, I'd say your options are to either stick with slow, or to add a hidden prop for high speed operation.

 

If you get to experimenting, try this and let me know how it works. Sam

 

This guy thought he might be able to. I don't know if he ever did or not. It would seem to me the water would be whipped into a froth, like a propellor cavitating. Sam

 

If you get to experimenting, try this and let me know how it works. Sam Sam, In my reading I have come across several authors comparing the "european" way vrs the "american". Aparently in europe they used small high speed wheels simalar to the one you showed as opposed to large wooden wheels on this side of the pond. I have also seen a design which used a second wheel with bars attached to articulating buckets that acomplished the same thing.

 

I would also like to point out that the large sidewheelers of the steam age regularly ran in the 20 mph range for extended periods. they had wheels from 50' to 70' ft in diameter.

 

I think it would make a great Margarita blender.

Seriously though, if you really want to do this, I suggest you visit: http://www.riverboatdaves.com and go to his links page. There are over 2,000 links to paddlewheel sites there.

 

thanks for the link and the replies

thanks for the link Artemis, didn't have that one. as for the blender. I remember a "sternwheeler " that a guy used to bring to the Charleston Sternwheel regata that he billed as the "worlds fastest sternwheeler" they would let him make exibition runs between race heats to entertain the crowd. It was a motorcycle with thin floats on either side of the bike with a plate metal (flat) front and rear wheels. The rear had blades attached to it. He had trouble getting the power to the water similar to the way high power boats blow out trying to take off, it would take him several minutes to get it "hooked up". But after he got going, He would come up through the gears untill he reached what appeared t o be the mid 40's and he ran out of room. Made an interesting rooster tail. This was back in the late 70's. Looked like a PWC running down the river.

 

That's the EXACT thought I had when I looked at it. 'Maybe if it was about 6" long it could be used mixing drinks.'