Scow paddle boat length

[whb]

Okay so Dingo's posting of Atkins lady of the lake has me thinking about paddle wheels.

I have drawn up a tentative scow design of 6' by 16'. Weight excluding wheel about 500 pounds.

Draft with four adults and gear about 4".

Here's the problem, I have heard that the beam should be no more than 1/3 the length. How important is it.

I could go up to 18' (I like a 6 foot width). Won't add that much in weight but will add a fair bit in trailering annoyance.

Just to make things complicated, I'm going to try to power the whole thing with a bicycle or two.

Thanks for your patience,

Howard

[Wild Dingo]

An interesting looksee could be Escargot (http://classics.nu/boat/) designed by Phil Thiel and built in this sites case by a fella in Seattle named Bryan along with his son and daughter... and really a worthy read! I have emailed him a few times about his build and his life the story of which he goes into during the build process... excellent site! a worthy endeavour and a great ending for a real nice mob of people.

Even if you just read it its a good yarn... but it could sharpen or give you some more ideas... it wouldnt be too hard I shouldnt imagine to put a paddlewheel aft of the peddles as drawn?... Ive redrawn it from the size given out to 25ft and reworked the inside to be more like the old English narrowboats {Discussed in WB mag #41 I believe} but I just aint got the skills yet to get it right... but Im workin on it!!... and sides Im a bit of a lazy buggar so there would HAVE to be an outboard there somewhere! :cool:

[ 02-10-2003, 10:17 PM: Message edited by: Wild Dingo ]

[John E Hardiman]

whb ;

Hate to say it, but thiner=better up to a length:beam ratio of ~ 8:1; after that it doesn't matter as much. Upper ratio is about 2.5:1, after that the penalty is STEEP.

As a thought; make the wheel the entire width of the transom and torture the bottom skin of the rise into a belly to make the waterplane entry an ellipse. This will improve power:thrust by ~30% and reduce power required by ~ 20-30%.

[whb]

Shane, Thanks I saved that site to my favourites to look at when I have a little more time. For the present I am planning an open boat with no superstructure but the strength will be there to allow it in the future and I quite agree that the canal boat seems well thought out.

John, A couple of questions. By torturing the plywood I will modify the bow to something in between a scow and a V shape. How much V do I need to get the performance improvement? I had thought about going to a sharpie type bow but the scow shape is much better for landing on mud banks and will take less damage when I find gravel bars (not an if but a when).

I was planning on building the sides straight up with no sheer. The river is flat and this shouldn't cause to much grief??

I was also planning a scow type stern to reduce drag. Would the same treatment you proposed for the bow reduce the drag further?

Finally, the wheel. The wheel I had planned would be two feet in diameter with six 6" wide blades. The actual wheels (placed every foot) will be solid 1" ply with a diameter 1" wider than the diameter of the blades. This way I hope it will roll up and over bottom topography rather than crashing. The elevation of the wheel will be adjustable so that I can take advantage of deeper waters. I also had hoped the solid wheel would provide a bit of a flywheel effect???

I had thought about a shorter wheel (say 2 feet long) to allow swimming/fishing access at the back of the boat and to make it easier for my legs to push. :D If I were to double the length of the wheel would the increased energy to push also double and would the propulsion double as well??

Thanks very much Shane and John.

Howard

[John E Hardiman]

Howard;

What I was thinking your hull shape was just a rectanglar box with a rake (i.e. slopeing) bow. I had thought to give some belly to the bottom in the rake, which will tend to give the waterplane an ellipitcal entry. You don't need much to make an appriciable difference depending on the amount of rake. Another big gain can be had in rounding (say 10-20% of draft) the immersed edges of the hull. You see both these things on barges to improve drag.

For a paddlewheeler, you want the maximum velocity difference between the blade and the water. A sternwheeler develops this by having a square transom to develop a very slow wake just ahead of the wheel. The bottom should only come up to the lower edge of the blade, well ahead of the wheel.

The amount of power required to achieve a given speed is not effected by the width of the blade, but the width of the blade effects the speed of the wheel necessary to develop that power. A wider blade requires less speed of the wheel to develop the same thrust, the wake being equal. This is why sternwheelers were more economical than sidewheelers, they could use lower speed machinery.

BTW, many sternwheelers had split wheels for steering. You will need large rudders under tha aft rake, and maybe flanking rudders just ahead of the wheel.

[whb]

Thanks John,

I think I am getting the picture regarding the hull shape. To get a wider deck but still maximize the length to width ratio I am thinking of cantilevering SP? the deck out beyond the hull above the water line. If I lengthen my plan to 18 feet I should have about 17 feet at the waterline. With a total beam of 6' with cantilevers of 8" on each side I have a beam at waterline of 4'8". This will give me a ratio of 3.6:1 .

Re: Rounding the side edges of the hull. I think a 3" radius round off shouldn't be too problematic. Will it give me the benefit you mentioned.

I was thinking of have the leading edge of the blades about a foot back from the transom is this enough.

Thanks John, I really appreciate your help.

Howard

[John E Hardiman]

Originally posted by whb:

To get a wider deck but still maximize the length to width ratio I am thinking of cantilevering SP? the deck out beyond the hull above the water line.

Re: Rounding the side edges of the hull. I think a 3" radius round off shouldn't be too problematic. Will it give me the benefit you mentioned.

I was thinking of have the leading edge of the blades about a foot back from the transom is this enough.

1) They are called sponsons hulls and many modern ferries and old paddlewheelers have them. You just need to be sure that the righting curve is always positive at zero heel so they don't loll.

2) I've used 6" radius on structures ~10' in beam by 8' draft and had no problems so 3" radius is in the ball park.

3) More important is where the centerline of the wheel is. It should be directly above the crest of the first transverse hull wave (to improve relative velocity and blade immersion), which is dependent on service speed. As you are looking for low power, I really don't think this is a major issue. More a problem is the proper selection of wheel diameter. A large diameter slow moving high torque wheel, or a small diameter high speed low torque one. I'd opt for a larger slower turning one, but I'd work the numbers first WRT the power plant capability.

[whb]

Thanks John, the powerplant capability seems to get less every year. :D But if I'm doing much pedalling of my boat maybe I can get it back up close to peak efficiency.

The actual wheel will take a reasonably small amount of material and I am willing to do a bit of trial and error to offset comfort with effectiveness. There is also the possibility that I might install two sets of pedals for when another power plant is on the boat with me.

The more I see of sternwheelers the more I like them for river travel such as I will be doing.

Thanks again, I might even get this project onto the river this year but not yet its still too cold in the garage/boat shop.

Howard

[ion barnes]

This is probably useless info but, at the Port Townsend WoodenBoat Show, a chap had on display what I could only describe as an amphibious canoe. It had bicycle wheels port and starboard, and a smaller spoked wheel for stearing hung on the stern. He had taken a bike frame and turned it upside down and facing with the normally rear end of the frame facing forward and where the rear sproket would be, was the cross shaft with the two main wheels. To propel in the H2O, there were paddle blades attached to the spokes and in the case of the steering wheel, it had a disc attached. He sat in a reclining seat. Sorry no pic available from me but someone else may have. It was quite marvelous.

[Wild Dingo]

Okay Howard me ol mate I hope Im still in the chase over here!! :eek:

Sooo we have another old fella paddlewheeler
http://www.imagestation.com/picture/sraid51/p767319d9559699da7313ee5845c2f0fb/fca6690a.jpg

Sent to me by Anita {thank you me dear! :cool: }

And another in the same index ...a paddlewheeler bass boat
http://www.imagestation.com/picture/sraid51/p004fb25f53584e37fbe32cca3f600d82/fca66788.jpg
That If I recall correctly came from svensons? I could be wrong but I think thats where they came from... never mind the whole article is there so thats important! ;)

Three pages each here (http://www.imagestation.com/album/?id=4290816399) ... worth a gander? click on the pic to get the full sized ones then print them off and have a real sticky beak at your leasure! :D

Take it easy

[whb]

Thanks Guys,

I'm building up a file of ideas that will get into the final boat. Now if the river was just a foot deeper everywhere those big ole river boats sure have some style.

Thanks,

Howard

[John E Hardiman]

Take a look at this web site, the people in the IHPVA can be a lot of help.

IHPVA web site (http://www.ihpva.org)

[ion barnes]

WHB, have you seen this site?
//gemort.wirefire.com/contents.htm

Scroll down a long ways and you will come to a title about paddlewheel boat designs. Have fun.

[whb]

Thanks John and Ionbarnes

I have both sites bookmarked and have been looking over their stuff.

Howard

[ion barnes]

Hey WHB, got a son living out there in the NW section behind the University. I'll give you a heads up the next time I'm out there. Ion

[whb]

Sounds good

Howard