Pedal Boat Design

Actually I don't think it would be all that complex. I am seeing a fixed axle on the pedals that drives a separate loop that has your basic 3 speed dérailleur. the loop would be small and rigid. That loop in turn would drive the wheel. The point being that the "gear changing" portion would be a very rigid fixed ring of chain that was then driven by the pedal loop and in turn drove the wheel loop...not some really long floppy deal that was subject to twisting etc. 3 speed setups are dirt cheep...


Rick is gonna roll his eyes about 800 degrees worth when he sees my scimitar /slash/ hatchet hull lol. Very slab sided, slightly curved bottom...pretty much a hard chine I think it's called. It is 6m (about 20') but only 15.5 cm wide (6"). I am trying to draw 10" of water but I still have about 30-50 lbs too much flotation. 4" hull anyone? Lol.

He said anything bellow 10" was less stable and that the wheels would be somewhat self leveling...and I have sponsors out at 20" so why not go deeper with a thin hull? I figure it would feel like your flying low to the water pretty much on your arse lol.

 

The main criteria for the outboard support is minimum drag not displacement. If they have positive buoyancy it will be helpful but waterplane should be so small that it will not be significant. The waterplane should ideally increase dramatically just above the normal water level like I have previously described.

The steering moment from the side wheels will be quite small. It will turn but very slowly. Rudders anywhere near the middle of the boat will be ineffective. The best place for a rudder is below the hull near the stern. If the increase in draft is an issue then use the dipping style of rudder that is only immersed when you want to turn.

Rick

 

BG
If you have the hull model on Freeship, post it so I can check drag. Going narrower will increase wetted surface and increase viscous drag that will not be completely offset by the reduction in wave drag.

There will be some point where it could be lower drag to just have fins below the sides of the main hull to support the inside of the wheels.

Rick

 

I've been following this thread since the beginning of August when I went on holiday. It is totally rivetting - a real demonstration of great, imaginative combined thinking, and how good the internet can be. I wish I could contribute something useful, other than encouragement: I can only just get my head round the basic principles of the foil wheel.
a tiny tuppenth worth:
Googling 'foil paddle wheel' and similar brought up a lot of interesting stuff in Patentstorm, and other online patent sites, but nothing quite akin to what you are doing.
When Paul MacCready and team won the Kremer prize with Gossamer Condor, part of the reason they got there quickest was the 'build quick and dirty' philosophy, which meant that they learnt quicker than the other teams going for the prize, who built immaculate, sophisticated aeroplanes, which took months to rebuild each time they crashed. He'd be going for proof of concept on the foil wheel, bolted to a bathtub, and then refine: chasing down the detail, I seem to remember Rick saying...
Go guys, go!

 

Tiny Tunip--

You just did =)

I could try as hard as I could and never get my head around the higher math Rick tears through like it was nothing. I could also research for about 10 minutes and then would be asleep. Tin Horn digs through what must be mountains of information and presents the cool little jewels he finds for the rest of us to enjoy. He also has made me a "fan" of the wheel by making it's history important and real for me. Curtis has a way of explaining thing I get right off most times. He is also a non linear thinker. Everyone in here makes this FUN. Can't ever go wrong that way.

As for quick and dirty...I am just not wired that way. I like the aesthetics (boats are beautiful) and the process of building. I look at the boat and automatically start thinking of ways to build it. How would the hull design lend itself to molding? how will I attach all the bits so they are easily adjustable etc.

Going with the 1/3 scale model will speed me up some...but it will likely have to be a beautiful model lol. Welcome to the thread and speak up whenever you want.

 

Hi, TT, welcome to the fun.
BG can afford to be finicky, in a way, since he's got the awesome tools to crank out whatever he can dream up.
That is one of the best parts of all this; with the CAD designs and automated machines, it's now possible to check a design in software, crank out a prototype very rapidly, test and refine it . . . this process used to take forever; now it takes a weekend, so turnover to final design keepsgetting faster. No need for "quick and dirty," now it's closer to "quick and beautiful."

 

I hit a snag with the new laser. Pretty frustrating but will resolve itself one way or the other. The biggest issue with the current one is it is only 40 watts and has an 18" x 24" bed.

Speaking of software. Rick...I can't find a description of the views anywhere in the FREEship manual (and its a .pdf document which are worthless IMHO). I do not know how to orient my hull in SW before I save the file so it imports correctly in FREEship.

Plan View is the top view (lower left window) I know, but I found 14 different definitions for body plan view (most sounded like an end view, but which end?). Profile view could mean side view (though why not just say that?) or like an end view/cross sectional like bulkheads view.

A little help here please =)

 

You're dead right, Curtis - the advent of the varied rapid prototyping methods (still amazing to me) have changed the design process hugely - quick with no sacrificing the beautiful.
BG - that's what I've really been enjoying - seeing everybody bringing very different ways of thinking, and huge energy to the project, and it all clicking beautifully.
On the 'boats are beautiful' and 'process of building' front, I've been enjoying the GA (Geodeisic Aerolite) boats website since it got a heads up on the 'tiny canal cruiser' thread. An 8lb boat! do you reckon it would take your foil wheel?

 

Got a linky?

Man oh man wait till you guys see this "hull form". I am really channeling my inner Kris Kraft--but in a 20 foot long 6" wide kinda way. Should have something to post in an hour or so.

 

aerolite boats:

http://gaboats.com/boats/

I don't know if any of these are strong enough to have much of anything mounted on them.

 

There you go. 20 feet long, 6 inches wide with some (to me) sexy lines. I want to make the bow rake (the curve coming from the front under the boat) a bit more swept back to fair it in better but I know Rick will make the poo poo clucking sound he reserves for those of us that design with our hearts and not our brains--not that he isn't going to anyway =)

As it stands right now, with the waterline at the long line shown (about 4 inches bellow the "main deck") it displaces right on 6 cu ft or 384 pounds of sea water. The wet surface area at that water line is about 40 sq ft.

I figure 30-40 pounds for the boat and 325 for the engines (least till I pedal off about 20 pounds =) for an all up 355 to 365 pounds. Thats about 20-30 pounds or our middle dog to high in the water. I think I can shave some of that off with a deeper radius and more aggressive bow and possible stern rake.

Closer anyway, and I like the look. Be a wonderfully fun hull to carve and lay up.

 

Since Rick is off either sleeping or watching his footie, lets have the lesser math minded predict what he says. I'll start:

The bow rake (if I am using the correct term) inst really needed because its a displacement hull and not a planing hull. Some to get it rising into a wave or aid in beaching is fine of course.

TOO MUCH DRAW--just use faired fins for the wheel.

Too much pretty and not enough math! Just plot these 5 bulkheads and fold some tin over em and get it done already!



Kidding aside Rick...I can't seem to get the views squared away in FREEship (see my earlier post please). If you can explain those I can save the FREEship file and you can see just how bad the deep draw hurts performance compared to fins.

 

I have paid employment you know.

The biggest factor for my non-raked bows is that they catch weed and give point loading when beaching. Some rake is very handy for practical purposes.

I will run a quick model in Freeship and see what Michlet thinks of it. Wetted surface sounds high so might be significant. My boats usually run around 2sq.m but they are lighter displacement. The ratio should be a displacement ratio ^(2/3).

Rick

 

Wow, BG, nice shape. I'll take up for Rick, here, though, I think that's a little fancier than you need for a test bed for the drive system. And what's that got, about a foot of draft? Is that going to be enough to keep you off the bottom where you'll be running it? I think -- if I'm following things correctly -- that the deep draft is to keep a clean line on the bottom and still make room for the drive mechanics, right?

 

Rather than redraw this hull it was faster to get Godzilla to produce the best 6m long boat limited to 0.15m beam. The attached files have the offsets that can be imported into Freeship. Don't forget to set the length dimension to 6m to get the the correct presentation of the Body Plan. This is only the underwater section. It does not have slab sides and draft is about 220mm.

You could expect 12kph with this hull so it is quite impressive. It will respond well to increased power so might sprint above 18kph. The wave drag is almost constant and quite low so this compensates somewhat for the high wetted surface.

Rick