Pedal Boat Design

You can purchase new sonar units for under $100, or much cheaper at garage sales. Few, if any, are accurate once depths become less than a foot or so. Plus, they all require electrical power of some sort.

 

I have Mesquite and palms lol. Ones lovely, ones a trash tree. You can't imagine the birds we get here. I get woke up some mornings at 5 AM by huge flocks of giant green parrots that just scream bloody murder. I have been outside on the phone and had to go inside because I can't hear and the other person always is amazed that there are so many birds in the background. When all the birds in North America fly south...they come here lol.

The Rio Grande is far from dried up right now with all the storms. One of the best fishing estuaries in the world. I have never been when we didn't catch fish. You know the fishing is good when you hear "Only 18" toss it back" and the fish in question is a trout or red fish. Tilapia is served everywhere. Raw (cooked by lime juice) with onions, cilantro and chilies. Mexican Sushi =)

 

See, thats the caliber of work I want to do. Just a beautiful solid well built cat =)

Looks like it would be fun if it worked lol.

 

Also, say were cruising along at 15kph checking out the scenery and chit chatting and it lets us know with a beep or tone or whatever that the bottom rises up 15 feet ahead...with no reverse or breaks...throw down your feet Fred Flintstones Style?

=)

 

Mmm, that, or something like it, maybe . . .

actually, you could have reverse -- maybe . . .

You've mentioned that if this incarnation fails, you'd go back to a regular paddlewheel, but I think a Voith type configuration deserves consideration here. I'm reasonably certain that it could be done by simply redesigning the cam track, and I think that deserves a look. I've thought for a while that you could build side-by-side versions of this squirrel-cage (one Voith-style, one not) and have most of the parts interchangeable.

Of course, a Voith based on a cam track would not be reversible, so you'd have to go to a kinematic system, but then you'd have reverse, as well as variable thrust for given speeds. I could see lowering the thrust as you approach your destination, to "warm down" as it were; same cadence with lowered resistance (if that's even a good idea).

Of course, the kinematic system will be more complex (heavier) -- and stronger, (heavier yet) if you anticipate having to suddenly reverse thrust.

Just something to think about.

As to the sonar, I don't see why a custom configuration can't be developed with the proper range and sensitivity for your needs. I also don't see why such a thing couldn't be made to run off a solar cell or a 9V battery. See, it really doesn't need to do very much -- just tell you that the water is getting deeper or shallower, and do so at a short range. It may be made to operate with something other than sound waves, as well; radio, laser, anything that will send a signal cheaply through about ten yards or so of water. Think of a TV remote control, for example.

 

Curtis
The Voith design is for low speed application and is not particularly efficient.

With oscillating foils you will find the theory often gets into the Strouhal number. When you look deeper into the optimum range it starts to define the size of the foil relative to the size of the body being propelled.

The proposed W-S prop will work in a very efficient regime and there is no need for blade reversal. Have a look at things like dolphins, sharks, whales tuna, penguins - fast moving sea creatures. Consider the relative size of their oscillating foil relative to the size of the body and also consider the reduced drag without wave making. You find a relatively large working surface. This is the sort of proportions for optimum performance. You can do the same exercise for birds with allowance for the low density of air.

For the typical towing application you would need huge foils to get into the optimum regime so the compromise is to work at foil speeds higher than optimum with little foils. The foils have to be able to face astern to avoid flow reversal over the blade. Having this capability also means you can provide thrust in any direction, which is also desirable for towing.

So if the cam system does not work well it is a matter of finding another method of activating or go to simpler solution using paddlewheels. The ability to fully reverse the blades is not required for an easily driven hull combined with large foil surface area.

Rick

 

Hmmm . . . anybody got a copy of "Strouhal For Dummies"?

What I see about your fish/dolphin comparison is that these animals are capable of tremendous acceleration, which this boat doesn't need. So, maybe it's because I need the above-mentioned book, but it seems to me that a Voith system can be tailored for cruising. I have seen on their site that they do have different designs for open water props as opposed to their "tractors." Perhaps you could explain this further for me . . . or point me to a "dummies" book.

 

It WILL work so no worries.

Seagulls have virtually the same wing loading as prop driven fighter planes which surprised me lol.

I think what he is saying is that in a dolphin or fish you find very nearly half their body surface is propulsion. A bottle nose has about the same cruise speed as Rick in his V12 and about the same top speed as well. To go faster they have to start clearing the water. Speed is relative of course but for the energy being used they are pretty efficient. If you increased the energy available to a bottle nose's mode of locomotion your not going to see much improvement. The voith is the same way and thats why you see them more as tractors then say cruise ships etc.

I really do feel this will work, my worry is the mechanics. Building it light enough, thin enough, and strong enough. I was no so worried at the original 75 RPM or even 100 but 200 is a new order of difficulty for the mechanics involved IMHO.

 

Many sonar units currently available have a shallow-water warning system, but by the time you are warned, if it is getting shallow quickly, you have no time to take evasive action.

They do make sonar units that scan for shallow waters up ahead of the boat, but these are expensive and require deeper water than we are talking about here - they are made for ships that draft 30 feet or more.

There is a HUGE market for a 'sonar' that would detect shallow water (say, one to three feet deep at about 30 yards or so ahead of the boat). Someone who could come up with such a device with an affordable price would become a millionaire (or billionaire) almost overnight.

 

Sonar on a HPB or PPB just "feels" wrong to me somehow. Not sure why as a bike computer doesn't. Silly I know lol.

 

Just think of the conversation starter it would be . . .

"Say, what's that funny-looking bulb on the front of your hull for?"

 

Curtis
If you google Strouhal and oscillating foil you will get a lot of hits I expect.

My point before on the Voith is that there is no need for full blade reversal. The required angle change for the W-S prop is quite small so it should be possible to keep the angle control system simple. I expect on an easily driven application the Voith blades may not need to reverse but this was not clear.

Rick

 

I've done that, and wasn't able to get much understanding of it. Strouhal is only one of the problem concepts for me, along with Reynolds numbers . . . foil behavior in general. I think that my problem with this is that I was never trained in the background of these things. Aeronautics is a specialty, and I'm kind of jumping into the middle of it in a random fashion and having to make the connections as I go. I have an associate degree in electrical engineering (which I never got a job at), and it didn't prepare me for this.

The biggest problem I have understanding the W-S prop is that I don't have a good grasp of how the foil produces thrust when its motion is so much perpendicular to the chord. Thus, my understanding of the W-S foils is that they always work in stall regime. I look at the Voith, and see that the foil utilizes its aerodynamic lift at every point around the circle, and this looks better to me because I know that the foil's lift is greater than its chordwise thrust. I guess that what I'm missing (among other things) is the way efficiency is tied in with these modes of operation. I do see that the Voith system is optimized for thrust.

The Voith can run at low pitch angles, so a track like the W-S would work. It's easy to plot a cam track for a Voith system, and it looks a lot like the W-S, just more eccentric. I have plotted a 12-point curve for one; I can give you the numbers if you're interested. It has a plus/minus 20 degree pitch excursion; very mild.

As to reverse, if you have the cam track carved into a "lazy susan," it could be rotated 180 deg, and there you have it. Another level of mechanical complexity, though.

BG might need to revert to the Fred Flintstone braking method.

 

Curtis
There is nothing very complicated about the operation of the foils in the W-S prop. It works identically to the Voith prop other than the boat velocity is high relative to the rotational speed of the foil.

You have not taken time to determine the flow vectors when the unit is in operation. Once you have done this you can determine the force vectors on the foil. A feature of the wheel with using 3 foils is that the vertical component of forces acting on the foils almost cancel.

Rick

 

Which the dumb guy (me) pointed out back when I mentioned your AoA's were not the same on the up stroke as they were on the down stroke =)

I had a hard time with this too Curtis till I started thinking about all the stall points and lift more as thrust. In flight it really is not air flow pushing the wing up as much as it is low pressure on top ...kinda sucking the the wing upwards. In the prop everything is sort of reversed. Lift is actually a negative, or undesired force and thrust is the goal.

I looked at Rick's diagram with AoA's and thrust vectors and they seemed backwards to me. Then I sort of imagine the forces on a boats hull when tacking as thrust, and the forces acting on the sails as lift (not true strictly speaking). Flip this over on it's side and I suddenly see The thrust vectors in his diagram working the correct direction.

I know Rick looks at the numbers and instantly grasps the concept. I sort of need to build analogies in my head lol.