Pedal Boat Design

You sure it's not a kayak Curtis?

lol.

 

BG,

The large diameter (vertical dimension on the right) is now 11", I never measure the smaller one. It's a 120 degree cone, as before. I'm about at the point of giving up on this thing, in case you hadn't noticed.

The other topic thread is here:

http://www.boatdesign.net/forums/showthread.php?t=23998

 

Another thought Grob.

The next one I build I will make the lid on a long side. You can seal the tank up pretty quick with 2 guys and and cordless drivers so the extra screws needed for the bigger lid are no big deal. Would make glassing the thing a good bit easier. Getting your part in would be easier as well.

I also had a small aluminum computer fan in it originally to circulate the air but it tended to blow any dust onto places I didn't want it so I removed the fan.

 

Curtis--

Just the blades out of 1/16" aluminum with no hub/axle are 4.8 pounds...not horrible by any stretch.

Sorry your giving it up...

 

Yeah, well, as I noted, 16 1/2 sq in per float -- that is literally smaller than the flat of my hand . . . the blades of my oars are about 108 sq in each. To get anywhere at all with this thing I'd have to beat the water into a froth with it -- and when I make anything bigger, I just wind up stirring more water than I was pushing. Maybe you or someone else could convince me to continue with this idea, but it doesn't look that way. That's why I switched gears, so to speak, with the new thread.

I'm thinking of digging out my old kayak paddle next time I go to the water, and seeing if I can get any satisfaction from that with the rowboat. Remember that my main motivation in all of this was to propel the rowboat facing forward.

Curtis

 

Well, just build a forward facing oar machine. There are tons of plans and kits cheap.

http://www.forwardfacingrowingsystem.com/whatis.htm

 

OK. I have most of the main frame geometry worked out. I also have the articulated (aka swivel) arm for the paddle wheel sorted out pretty much as well. I am attaching a little animation/movie of it swiveling.

It is shown with 3 holes for positions but I will likely just use one arc that covers all the space between the holes so you can position anywhere in the arc. I have about 10" of travel so I can raise the wheel completely out of the water if needed for beaching or coasting etc. I am considering a locking lever driving a push rod to a horn for in use adjustment.

The I beam main frame and wheel arm are going to be CF and weigh 8-9 pounds. It is looking like the entire frame assembly with down struts and all the hardware is going to be 18-20 pounds. Hulls will be 15-18 pounds for about 30-36 pounds. Paddle wheels at about 25 pounds. I thing 90 to 100 pounds for a solid boat is pretty doable. I know I could do a race version at 70-75 pounds no problem. Maybe V2 =)

 

Curtis--

Sorry man, I just cant get it to render to quick time. Here are some stills.

 

The one you linked to is beautiful, but with a set of oars included (or bought separately) would equal the entire price of my boat ($500 + $200 shipping).

I've looked at these before; actually, it's the first thing I considered, but the prices drove me away . . . and I just looked again . . . the one you linked to is the cheap one -- of the three systems I found. I didn't find reference to any plans for DIY.

 

This one had a neat concept I though too.

http://www.frontrower.com/aboutfrontrower.htm

As for DIY...how could it get easier or cheaper then this?

Not even any bearings or anything lol. I bet you could use PVC parts from the hardware store with a hack saw and some bolts even...

 

BG
I do design in 3D. Even with Autocad my preference was 3D. I could not see the point in making 3 separate views once you had the computing power to produce a replica of what you wanted to build.

May last serious engineering project was all 3D down to 25mm piping but there was a team of draftsmen working on that. We had walk-throughs for design reviews. THe clash detection took 4 hours to run each Saturday morning. That was ten years ago now.

I had a look at the SolidWorks web site and it seems you have to request a quote. What can one expect to pay for a useful home system?

 

Well, I couldn't use the Frontrower even if I wanted to, although the drop-in idea is pretty slick -- bum hip, gotta use the arms.

As for hacking one of the gig Harbor jobs . . . I might put some serious thought into that. No, PVC won't handle the stresses, I'm sure, LOL, and if you read their whole website, they built prototypes of aluminum, installed them on real boats, and drove them to failure to see where they broke before they made the final products out of stainless. So it does need to be strong, but the geometry shouldn't be impossible to suss out. All the alignments need to be just right, though . . . hmm . . . I have a drill press, but not much else, no welder, and the worst is that I don't even have a good vise for that kind of work.

Looking at this with more perspective, if I were to go with a paddlewheel or some other whirligig, I'd most assuredly have to hire out some of the fabrication to some custom shop, and what would that cost?

Boats . . . a hole in the water that you throw money into . . .

Curtis

 

BG
I do not have any idea of your actual ability to calculate stresses so this might be telling you things you already know but you did ask for design review.

When you are pedalling there are are high torsional loads imparted on the frame through offset loading from the feet. Under heavy going you will be pushing with forces up around 300N that has a significant moment arm to the line of the frame. Point is the frame has to resolve the torsional component. Enclosed section area gives torsional rigidity. That is why bikes use tubular frames.

I can tell you from experience that there is nothing worse to pedal than a frame that twist as soon as you apply some load. I have never done it but probably akin to riding a snake. It wobbles all over the place.

So one of the load cases is to compare deflection under torsional load of your flanged frame with that of a tubular frame of the same weight.

My V7 boat (see attached) has a Greenspeed (http://www.greenspeed.com.au/trikes.html) trike frame factory built for the boat. It is the absolute best thing to cycle because it is so nicely set up and is very rigid. It is a little heavy in steel and I now prefer to use the hull to resolve my leg forces as it saves weight and my hulls are rigid torsionally (large enclosed section).


Rick W

 

Rick--

By home system do you mean a PC capable of running the program or the software itself? As for the system, any decent PC newer then say 2-4 years old will run it fine. If you want to be able to work in a semi photo realistic environment, as in rotate and manipulate your view, then a workstation FireGL class video card is needed (about $1,500 USD and up for those). To me thats a distraction so I just use the standard shaded cell type output.

As for the software, I have no idea of its price as I get copies for review purposes for my web site. I know they have several levels and modules etc like student and so on, but it is still in the AutoCAD price range.

Torsional stiffness. Yeah, I am keeping an eye on that as well because I know a lot of energy is lost to frame flexing. Without the down struts attached it is borderline but once they are on and with an N strut it gets pretty stiff. Once it is all done we can go over it and worst case i have to go with a box tube.beam type set up.

I remember your yellow boat lol. See, I love that hull shape....except the out rigger banana =)

 

I have an 18 month old DELL XPS for desk work. It is unencumbered with any background programs apart from a couple for connection purposes. For example I do not use any virus detection. I use a MacMini for email and web connection as it seems less prone to picking up unwanted stuff.

It seems I need to shop around to see if I can get a price for SolidWorks.


Rick W