Requesting Small Sternwheeler hull design and analysis help

Thank you.

Odd, to me, that the resistance would be increasing, since the hull should sit higher in the water, with more evenly spread buoyancy. With less hull projecting into the water, it seems to me it would have less resistance.

That pontoon-like box configuration is actually close to the way she'll be done, one way, or the other. I figure 6in in from the gunwales, to the combing. on the interior, that will be straight down to the floor, and the space will be filled wuth buoyancy foam, which will also stiffen the hull a bit. More weight here, but less in the frames. It evens out, somewhere down the line... Foam increases the safety margin, so it's a win!

I really appreciate the work. I know how hard I have been working at the overall design, and I would not even try to guess how many hours of research I have put in, both before and since starting this thread.

via Google Translate:

Grazie.

Strano, a me, che la resistenza sarebbe in aumento, dal momento che lo scafo dovrebbe sedere maggiore in acqua, con galleggiabilità più diffuso in modo uniforme. Con meno scafo sporgente in acqua, mi sembra che sarebbe meno resistenza.

Questa configurazione scatola pontone-come è in realtà vicino al modo in cui lei sarà fatto, in un modo o l'altro. Immagino 6in in dalle gunwales, alla pettinatura. per l'interno, che sarà dritto fino al pavimento, e lo spazio sarà riempito wuth galleggiabilità di schiuma, che sarà anche irrigidire la carena un po '. Più peso qui, ma meno nei frame. Si uniforma, da qualche parte lungo la linea ... Foam aumenta il margine di sicurezza, quindi è una vittoria! : D

Apprezzo molto il lavoro. So quanto sia difficile ho lavorato presso il disegno complessivo, e non avrei nemmeno cercare di indovinare quante ore di ricerca ho messo in, sia prima che da quando ha iniziato questa discussione.

 

Resistance in a vessel moving through the water comes in 2 formats... friction and wave creation. I expect you are only considering the friction resistance. At very low speeds friction resistance is a consideration, however as speed goes up, it rapidly takes a back seat to wave making resistance.

 

Jeff, I applaud your determination and hope you have an absorbing and satisfying time working on your project

I have a 14' planing skiff with a vee bottom and only 1.1m beam at waterline. With the outboard on its still very light estimated total well under 200lb. I am a wide strong bloke. I recently found myself in a bit of pickle when I went to launch the boat and found it sitting on mud with about 20 odd metres to the water mark. That was on the day of our lowest tide. Usually I just float it to a ledge and climb in

I had to walk out in knee deep mud to the boat. You are right, the vee helps working it loose, but what then? I have a strong back and legs, it was bloody hard yakka finding purchase to push it not only to the water mark but further into a few inches of water till it floated

If having to work the boat is that significant design feature then you also need to include in the design how you will get it in the water with your troublesome back. I think the snowmobile idea mentioned previously in this thread has some merit and encourage you to explore it a bit

I might be speaking out of my arse for I know but an obvious and logical solution where a rear paddle wheel types propulsion unit might shine over outboard or jet would be to incorporate a pair off small tractor/dune buggy tyres filled with flotation foam on a light aluminium rim to either end of your paddle wheel and the diameter of the tyre wider then paddle diameter. Or even just one tyre in the middle of the paddle wheel. A setup like that can prolly cross any bogg if enough power is applied. The tyre tread bits might even add propulsion on the water

 

For the through-hull direct-drive EV prop system, something like this, only 2 units, half the power each, one to either side of the keel?

http://www.ecoboats.com.au/bellmann/inboard_motor.php





As straight-forward as the design is, I think I would not need to throw big-money at it. Motor, bracket, shaft w/packing and prop... Simple enough design.

 

I plan to cheat... Fill a couple of 55 gallon drums with concrete and make permanent anchorage points, plus some plank walkway sections, for support over the mud. May rig a cable system, so I can move her further out, when necessary. Only time I'd have to worry, then, is when I need her out, ahead of flooding.

If there's a slow rise, ahead of the flooding, I can ride her down stream and get her out of the flow, ride it out in an eddy, then come back up, before it gets too low. Backup generator for the electric power will allow that, and then some.

There's an rv park with a public ramp, fairly close, and a public park with a good ramp, even further downstream, both within 30 minutes of driving-time, from the house. Not sure how far to the nearest public ramp, but it's upstream a few miles, with a long way around, for cars to get there.

 

I can see the hull, but, have no idea how to read the graph. I don't have the background to know what it means, or how to apply it. Calculated resistance at 1ft intervals? Does that take into account the whole hull, and each station, or is it a resistance only by cross-section? A flat cross section is obviously harder to move through water, than a streamlined one.

I appreciate the effort and look forward to the lesson... One of my favorite sayings is: When you stop learning, you start dying.

 

phrogjlf @ yahoo. phrogjlf @ yahoo

That line is the trend volumes Hull: shows graphically how it develops the submerged part of the boat.
The numbers indicate: the displacement - the center of buoyancy and flotation - and the metacentric height, which is the static stability of the boat.

 

In real-world practice, if plotted on the actual hull, from the center-line to the side, would it approximate the static water-line, in still water, something like the white displacement area, of the plotted bottom?

I don't have a clue as to what programs, or how to use them. Been about 20 years since I barely passed Lotus 1-2-3, my most advanced computer course...

 

phrogjlf @ yahoo

that line curve graphically represents the trend of the volumes of the submerged part of the hull.
It also calculates the centers, the weight of the boat and its stability.
Once, all these calculations were made by hand on the drawing board, now design programs with the PC makes everything faster.
But.
Having a PC program is only more comfortable, but if you do not know what you're doing and why, the result will be disaster.
The ship design is a science-art that requires many years of learning.

 

I have shown that
graph, to illustrate this:
is the boat that I'm drawing, when it goes with the push of electrical engin, at low speed.
Here is a table showing all resistances



You Can See That to 3 knots does not exist residual resistence and the power that Has need the boat is very bit.
ok?
------------
Here what happen when the boat is use by normal engin with more power and more speed



with more power and speed the resistance increases, and the boat sits a bit 'on the stern flat.
ok?

 

ah, you can see also that the main deck (grey line) is flat.
But i drew the wale, because in the deck totaly flat you can not keep enithing coz at the minimum heeling slips in water.

 

Thrust line

I noticed that there is a line through the bow, at the static water-line, that also passes through 2 of the points in the drawing. Would that be close to an ideal thrust line? It seems to me, it would try to push up and lift out of that squat, even though the contact area would still move back.

 

phrogjlf @ yahoo,

not get lost in useless speculations.
The term 'static' is used only for calculating the metacentric height that indicating the stability.
Instead to understand what happens dynamically, compares the profile that I posted in post 154 with the profile of the post 161.

 

Forgive me if I come to the wrong conclusions, I do not have the background to understand it well, but, if I do not ask, how can I learn what it is?