Pedal Boat Design

[clmanges]

BG,
I forgot to say, I like the new design a lot. I could imagine it would be a real attention-getter out on the water. Nice touch, getting the pod all faired into the main hull. I think you could smooth out the contour over the axle hump on the pod, too. Just be sure to apply a graphic to the top of the pod saying "NO STEP" like they have on airplane wings, lol.

 

[Guest625101138]

Curtis
Your ply hulls would be close to optimum for a hard chine catamaran. They would work well. Much faster travel then the dinghy. The pitch while boarding is usually taken care of by having it beached.

A lever arm down to oscillating foils on each side of the seat would be much easier than rowing.

Rick W

 

[clmanges]

Curtis
Your ply hulls would be close to optimum for a hard chine catamaran. They would work well. Much faster travel then the dinghy. The pitch while boarding is usually taken care of by having it beached.

A lever arm down to oscillating foils on each side of the seat would be much easier than rowing.

Rick W

Oh, much faster, no doubt.
That pitching tendency was pointed out to me by someone on the Yahoo group as a tendency to "hobby-horse" in waves. The suggested solution would be a different shape at the aft end, to break the symmetry. Personally, if I could build it, I'd use the bulkier shape of the first design, for the extra pitch stability, since, with the skinny hulls, I noticed a lot more pitch variation with just a small change in CoG. It would be a little slower, but that wouldn't bother me, I'd prefer the stability.

One of the reasons I never built it was an unanswered question I had about whether I could paddle it with the kayak paddles without repeatedly striking the crossbeams. I put a lot of thought into trying to design around that, but never came up with a satisfactory solution. I figured that the best way would be to somehow put the attachment fixture on the inward side of the pontoons instead of on top, and I never got comfortable with any ideas for that. Of course, a different propulsion method was not on my mind at the time.

The big thing that stopped me from building it was this: I had gotten a sheet of plywood to build the seat/deck assembly, but just the work of penciling out the shapes of the parts on it resulted in a few days of extra back pain. I thought, "What's this going to do to me when I'm wrangling power tools and big pieces of material?" That's when I decided to buy the rowboat. That sheet of plywood -- uncut -- now forms the floor under my shooting bench in the back yard.

 

[BG_Geno]

BG,
Glad you like the model. No balsa, just plywood, and faux-glassed foam pontoons on the first one.

The deck/seat assembly would be half-inch ply at full size.

The foam pontoons were built after Gary Dierking's Quick-Ama instructions;

http://homepages.paradise.net.nz/garyd/quikama.html

there's a central ply web with rigid insulation foam on both sides. You can see I copied his crossbeam attachments. I wanted to emulate a glass-epoxy coating, so I used a very thin cotton cloth and plastered epoxy on; it's very rough and ugly up close, but came very close to my calculations.

The plywood for the hulls would be quarter-inch in full size, and even with the monstrous overbuilding shown (upside-down, without stringers or skin) was still much lighter than the foam job.

There was a method to my madness in making it this way. All the pieces fit together with keys and slots. Notice that there is no glue on it as shown, but it's all straight and square. If the parts are all nicely cut, the assembly squares and straightens itself without forms or clamps. I figured that I'd be working solo on this, and hobbling around with a cane and trying to manhandle long pieces into place and clamp them would be too much for me. So, this.

Yeah, it'll survive a level of disaster that would certainly kill the pilot. I showed it to my brother, and he said, "That's way overbuilt!" I posted pics to the Yahoo Boatdesign group, and they said the same thing. If I were to actually attempt this in full scale, I would narrow the webs and eliminate most of them, but I like safety, so I'd keep the solid bulkheads.

As I was building these, I thought they were too flexible, even with the stringers, but once I put the skin on, I figured out that I could stretch strings on them and play music if I wanted to.

I am an old R/C airplane guy from way back so I LOVE structures like that. Next time heres a very simple, cheap, and easy trick for your "glass" on the outside. Take one of your wifes old nylon stockings (preferably sheer toe) and shove the float into it. The stocking clings to all the contours exceptionally well. Brush on a coat or 2 of resin, sand a little if you like, and your done. I doubt there is an easier method.

 

[BG_Geno]

BG,
I forgot to say, I like the new design a lot. I could imagine it would be a real attention-getter out on the water. Nice touch, getting the pod all faired into the main hull. I think you could smooth out the contour over the axle hump on the pod, too. Just be sure to apply a graphic to the top of the pod saying "NO STEP" like they have on airplane wings, lol.

I want to drop the saddle down 2 inches and build a back on it that matches the hull but I can't get the dang boat deep enough lol.

 

[BG_Geno]

Oh, much faster, no doubt.
That pitching tendency was pointed out to me by someone on the Yahoo group as a tendency to "hobby-horse" in waves. The suggested solution would be a different shape at the aft end, to break the symmetry. Personally, if I could build it, I'd use the bulkier shape of the first design, for the extra pitch stability, since, with the skinny hulls, I noticed a lot more pitch variation with just a small change in CoG. It would be a little slower, but that wouldn't bother me, I'd prefer the stability.

One of the reasons I never built it was an unanswered question I had about whether I could paddle it with the kayak paddles without repeatedly striking the crossbeams. I put a lot of thought into trying to design around that, but never came up with a satisfactory solution. I figured that the best way would be to somehow put the attachment fixture on the inward side of the pontoons instead of on top, and I never got comfortable with any ideas for that. Of course, a different propulsion method was not on my mind at the time.

The big thing that stopped me from building it was this: I had gotten a sheet of plywood to build the seat/deck assembly, but just the work of penciling out the shapes of the parts on it resulted in a few days of extra back pain. I thought, "What's this going to do to me when I'm wrangling power tools and big pieces of material?" That's when I decided to buy the rowboat. That sheet of plywood -- uncut -- now forms the floor under my shooting bench in the back yard.

No need to shoot your bench just cause your back was sore man...

Like the guy with his mower lol

 

[clmanges]

Hey, I haven't shot my bench -- I'm shooting from it, lol.

Right now, I'm waiting to see if you guys can get this squirrel-cage thing working, and figure out if I can stick one on my rowboat! With tires on it! I want it to roll!

Really, that actually would satisfy me quite a bit.

 

[BG_Geno]

working on the designs now...was thinking maybe I could give the bottom some curve from the center towards each end maybe to make it draw more water...thoughts anyone?

 

[clmanges]

What kind of curve? Pictures, please?

 

[BG_Geno]

Just a gentle sweep from near the center to the bow---same fro the stern. Remove some displacement.

 

[Guest625101138]

Hey, I haven't shot my bench -- I'm shooting from it, lol.

Right now, I'm waiting to see if you guys can get this squirrel-cage thing working, and figure out if I can stick one on my rowboat! With tires on it! I want it to roll!

Really, that actually would satisfy me quite a bit.

Curtis
Squirrel-cage describes it aptly. You could have them clamped to the side of the boat with small hand cranks driving the chain or toothed belt. With them operating separately you could turn in your own length.

They could be smaller than proposed here. Say 8" long and 6" diameter.
Rick

 

[Guest625101138]

Curtis
Your posts on arm power reminded me of a fellow who used to bring a sailing boat to the lake a couple of years ago. He was probably mid sixties and asked for a ride in my boat after seeing me in it on a few weekends. At that stage it was V6. I have posted the video I took.

Actually just realised it gives a good speed comparison with a sit-on kayak in the background.

Frank had been contemplating setting up a pedal powered rowing boat.

Anyhow Frank found the recumbent position awkward and managed to do better speed just hand cranking the pedals. I had already tried pedal powered vertical foils and found them terrible for a range of reasons so I think I poured cold water on his idea, particularly when he found what he could do by hand cranking. There are quite a few bike set ups with hand cranks. There is a Canadian builder specialising in them.

Rick

 

[BG_Geno]

looks like a submerged rowing shell lol

 

[clmanges]

BG,

Just a gentle sweep from near the center to the bow---same fro the stern. Remove some displacement.

That might work okay, but I think you could narrow the hull some instead. Rick can optimize a hull shape for you.

looks like a submerged rowing shell lol

Yeah, no windage on that hull, is there? I recognize that 'yak in the background, it's the same make and model I had. I really miss that little boat.

Rick, I'd be fine with hand cranks. I just hadn't been thinking in that direction, due to the complexity; one of the things I'd like is to be able to build all my own stuff, and I don't have the shop equipment to do it. I could hack up an old bike, but I don't know if I could finish what I started . . . I'd have to buy a welder. I can think about it. The boat would need lots of stability for me to get on and off of it safely. Don't know if I could install a hand-crank in my rowboat and have it work . . . gotta think about that.

I'm familiar with hand bikes; I worked on wheelchairs for twelve years. That was quite a few years ago, so the newer ones are better. I see that Greenspeed makes one also -- for the price of a good used car. I'd order one, but there's no safe place for me to ride such a thing here; I'm on a main road, and there isn't adequate safe space on the shoulders of the roads out here to keep from getting pasted by the fast traffic. Bicycling is another thing I miss (along with hikes in the woods).

 

[clmanges]

Curtis
Squirrel-cage describes it aptly. You could have them clamped to the side of the boat with small hand cranks driving the chain or toothed belt. With them operating separately you could turn in your own length.

They could be smaller than proposed here. Say 8" long and 6" diameter.
Rick
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You'll have to excuse me, I haven't finished my first cup of coffee yet.
That would really be great. I don't think it would be too much of a stretch to devise a fold-away crank handle with some kind of secure latch; then I could wobble my way into position without the mechanicals getting in my way. Just need to figure out a mounting system. They'd have to come off for transport.

Really, though, if the squirrel cage had tires on it, I could leave a stern-wheel configuration permanently mounted. I'd have to add kick-up rudders, but that's acceptable. Maybe a dipping rudder system; I like that even better.