Pedal Powered Boats

posted here and design forums for help

Any suggestions welcome......

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I have read a lot of the pedal powered boat thread and otherthreads here but still am trying to get a plan together for what would work best for what i want to do. I have three perception 12.5' caster kayaks. I am looking to do 2 things.
The purpose will be for recreation/fishing rivers, lakes, bays.
Determine best propulsion method individually and I want to fabricate some sort of trimaran out of the three with aluminum/stainless tubing.
Individually, how long does a trolling motor battery last usually? I think I would be satisfied with the speed but would be concerned with running a battery dead after a couple of hours.
I like the ratchet gear and stairstepper style pedal system with some type of gear box (from mcmaster etc.), or would a regular bicycle pedal and gears setup work better (for being able to get 10-15 different speeds) if I was going to be out for up to 6 or 8 hours? pedaling from the seat in the reclined position.
Or would a pedal powered battery charger pushing a trolling motor be more efficient than directly pedaling a prop all day?

As for making some type of trimaran:

Should I use stainless or aluminum or carbon fiber tubing? I need 1'' diameter. Which is cheapest?
I am looking at the hollaender.com fittings to join them together, still looking for any other sources also.
What is lightweight for decking/? any sources? or would a trampoline hold up?
I wanted to have two kayaks in the back and in the one offset forward like a triangle or would this work better with all three side by side?
I am thinking a 5hp motor on this setup would be easiest but does anyone know how good pedal power would work with three people +(maybe a sail for open water) on a rig like this. Also Id like to know cost wise would it be worth it. Seems like a good 5hp motor would be hard to compete with cost+performance+ease of installation.


Thanks in advance for any help

 

Love it

Hey - I love pedal powered boats. Great discussions here.

Regards,

MJ Boats
Great Boat Plans & Designs

 

That's really nice, but this looks awfully like a shameless shill.

 

Not experienced with pedal power but I know a bit about mucking about in small boats in general.

So just general ramblings in answer to your pretty general questions !

A trolling motor battery lasts as long as it lasts. Sorry. It depends how hard you drive it, how big the battery is (in amp-hours) and how big the motor is (what amps it draws). There are alls sorts of things that alter this, but if you have a battery that is 100 AH and a motor that draws 10 amps (which at 12V would be 120W, or about 1/6 HP), you will theoretically get 10 hours from it, running full time. However batteries hate being fully discharged, so that's true only if the maker's claims are accurate and that the rated amp-hours are what the battery can actually deliver while still within its true working range, and they may well not be. So it varies from battery to battery. Batteries also hate being hard driven, so if you really drive hard compared to the battery's capacity, the running time drops even further.

If you just puttered about with the motor, drawing <1/2 of the amps and that just intermittently, then it would last a lot longer.

So really, it's just like a tank of fuel. Many variables, and rules of thumb.

As far as I can tell, it's felt that using a derailleur gearing system is too complex and unreliable. Also the loads do not change as much on the water as they do when cycling, so it's not needed. You need to look through this thread for gearbox ideas. I do not know what McMaster offers, but I don't think they have been mentioned as a source.

There is some discussion about gearboxes in and around here
http://www.boatdesign.net/forums/boat-design/pedal-powered-boats-23345-11.html


Any system that charges a battery to run a motor is so inefficient (probably 20-30%) that the only way it can be used when efficiency is needed is to use any power wasted during normal operation. So braking etc can be used. But braking is rarely needed on water. It's nice to think that you can pedal when you want, then draw nice and easy when you need it, but it just is not worth it.

You don't actually "need 1" diameter" tubing. The diameter depends on many things, and one of them is the material. Stainless and carbon will be much "stronger" than aluminium given the same piece of material and forces on it. You also have to take into account the forces, wall thickness etc. For general mucking about and moving around, I feel that 1" is inadequate. Check out your average surfcat for some idea of sizes.

Based on price (and availability and workability), aluminium is the way to go.

My gut feeling says that the less fittings and joiners you use, the better.

A trampoline would certainly hold up and is really light. Cats use them for years. but it may not suit your purpose, because they are not called "trampolines" for nothing They also place quite a strain on your beams and connections, because they rely on tension to support your weight. This may or may not be a problem, but you have to design for it. I would look at foam-cored plywood, or foam-cored fibreglass for light weight. That's a whole discussion in itself.

Is there a reason you need to use the three boats? Remember you are putting a deck on here. However, the triangular idea sounds complex and weak with a lot more stresses to take into account, and is probably inefficient as well.

A 5hp petrol motor would just about take what you are talking of into space! A 5hp electric motor would be crazy (and yeah you would have serious battery issues)! It would certainly be ok with a pedal setup but remember you have to pedal. An electric trolling outboard is probably in the order of 0.5 HP, not 5 hp. Work on each pedaller putting out about 100-150 W, or about 0.15-0.2 HP, sustained. That's easy going, but you do not want to be heaving and puffing.

Allowing for the fact that you need nothing like 5 HP, you are right. It cannot be beaten for ease of installation. Petrol is still way best method of energy storage. Petrol gets 70-100 times the energy density (energy per kilogram weight to store) of batteries. Even allowing for greater engine weight, you have to go a long way to beat it. We are not talking effectiveness or efficiency here, just the weight of "fuel" needed to store running time.

Setting up pedal power will either cost money or take a fair bit of research and DIY. Three ready-made pedal stations would definitely cost more than a 2HP outboard. Al lot of guys here are at the level of building their own propellers. Others have adapted various scrou8nged parts. Other have bought ready-made stuff.

 

Some comments inserted.

There is a lot of detail in setting up a pedal drive that is not immediately apparent. The loads that you can be produce in legs are large in in terms of the boat structure you have. You need to understand how these loads are carried. Can be done with trial and error but it is a long and frustrating process. Bikes are a simple but strong structure that is easy to overlook when taking the pedal technology to a boat.

You also need to consider where the pedals will be located and the clearance for the heels in particular. If the pedals are mounted too high then you will get numb feet as blood drains out.

It is unlikely that a side mounted shaft would suit the hull so you need to place a shaft tube and set it up to align with a right angle drive.

The boat hull should be stable enough but you no longer have the use of a paddle to assist with stability and your CofG is higher by virtue of the feet on the pedals. So you have a boat more prone to rolling over.

The hull for a fast pedal boat is not much effort if you are not too concerned about weight. 3mm ply is OK for stabilisers and 4mm for the main hull. With a narrow hull and stabilisers you get a faster and safer boat. You can use a side-mounted prop that is much easier to set up.

 

Thanks guys for taking the time. I want to use all three kayaks because It is two of my brothers and I. I want to be able to fish together off of this rig.
I wanted to use 1'' od tubing because I was planning on attaching directly into the rodholder slots on the kayak with rubber stops around the tubing to hold them in place so I dont have to drill any holes. I think they are in a good spot to evenly distribute weight if I attach to the two behind the seat and another support through the rodholder in front of the seat. Or there is a spot to attach another circular base where a sail is supposed to go in front of that rodholder. I tried to attach pics. Dont know if they will come through or not.
And Yea Rick I think 5hp is a little much, Ha maybe a 3.3 would be better. 4mph is fast enough.
As for the pedal power there is already a scupper hole in the floor in front of the seat with a 1.5'' diameter hole. I would like to put a shaft through this hole without drilling which would require a two piece assembly where only the shaft would insert from the bottom up and attach to the drive assembly inside the kayak. I was thinking something like a large thin flat plate assembly would sit flat in the floor of the kayak with pedals attached to it. What about something where I would just push each pedal alternatively in a horizontal motion on a slide much like and in the same place where the footrests are located. These kayaks are about 32'' wide and pretty stable. no problem to stand up in one.
As far as a trolling motor I have seen all the rigs with a milk crate and motor to the sideand others, I am just looking at all available optoins at this point and would like to hear any opinions on trolling motor vs pedal power for long distance and long hours on the water. Also there is a scupper hole in the back that is placed in the center of a slot made for a 5 gal bucket where a shaft could be. Same issue here with having to install from the bottom and top with just a shaft running through the 1.5'' od hole in the kayak.

 

Casey
For now lets focus on a mechanical pedal system and see what might work.

What shop capability do you have access to - turning,welding etc?

How much were you aiming to spend to get a nice pedal system?

 

I have access to someone's shop. I was thinking of just buying from a machine shop, but If prices are unreasonable on these parts I can get to a welder and lathe. I was going to spend whatever it cost to get something that would last pretty much forever and most importantly work, but would also like some low budget alternatives. Naturally I would like to spend as little as possible, but i know that high quality parts are not cheap. So Im not totally against buying a finished product out there if its a good deal but I haven't seen anything I like enough yet.
How Much should I expect to spend?

 

Casey
Looking at the drain hole I think you might get a toothed belt through it.

Something to do a design on and price it would be 3/8" toothed belt with a 12 or 15 tooth pulley on the prop shaft and a 40 or 60T pulley on a shaft extension of a gearbox. Belt would need to 1/2" or 3/4" wide - the biggest that will fit throudh a tube in the drain hole. I use metric size T10 pulleys per attached with pulley direct to crank so this is bigger than you need.

The belt will need guide rollers at the bottom so the belt will fit up through the tube that goes through the hole. The tube would socket into a collar above the drain hole that carries upper pulley.

The gearbox I suggest is Mitrpak shown here:
http://www.mitrpak.com/product_datasheet.php?product_id=84
This is large enough to mount cranks directly to the though shaft. The output shaft will spin twice the crank speed.

You need to mount the gearbox rigidly to the hull but it has lots of mounting points so should be possible. The output shaft of the box needs an extension with outboard support to carry the large pulley. One issue to check is that the pulley can be placed so your legs are not colliding with it.

For transport you would roll the belt off the large pulley, undo the through hull tube from its deck socket and pull the tube from the hull with the belt.

For trials you could start with a 12X8 model plane prop. It will be strong enough to do some testing but you will probably need to make your own prop from stainless or aluminium for long-term use.

I would seal the prop shaft so the belt does not act as a pump pulling water into the boat. You would need a bit of space around the tube to allow water to slowly drain from the cockpit.

If you think this might work and the prices are not daunting then sketch it up relative to the seating position, gearbox mounting and the drain hole. I can then advise you on the dimensions you need to have.

You will need to work out how to connect cranks to the gearbox as it is just a straight keyed shaft. I have asked Mitrpak to provide a price for boxes with square taper to suit cranks but so far there has been no reply. They have made them for a larger box but it is not standard either.

Swing arms with ratchet drives are a possibility but way more complex to set up than the belt.

 

I expect you will get something of similar performance to this but a lot cheaper:
http://www.diveandkayak.com/servlet/the-785/Hobie-Mirage-Pro-Angler/Detail
It will have a nicer action on the legs and be more efficient. Speed in both cases is limited by the hull form.

The gearbox and belt combination will be very smooth. It will feel smoother than a bike because the toothed belts do not have the slight cogging you can feel with a chain. The belts do not need lubricating either.

You could also use the gearbox mounted to an angled tube that runs right through the hull. The tube would need a flange on the bottom that seals into the hull. It would be the cheaper with fewer things to go wrong. It would need a large prop but that is no issue. It would run behind the boat.

 

Im not completely following you on the belt routes with the mitrebox setup. I think you are talking about directly mounting pedals to the box first but I am confused from there. Are you talking about a pulley on the output side of the box that would turn the belt that would run horizontally and then through another pulley that would turn it vertically to go down through the shaft and hull? I dont know if you have a picture of any design might help. I have seen the one with a twisted belt or chain that looks simple but I think it is different. Also do you think there is a setup to use sliding push pedals instead of rotating pedals like a bike? So that it could be used at a lower elevation.

 

Twisted chain or belt drives a fiddly to set up.

The pulley set up I am referring to would be off an extension of the output shaft of the gearbox. That places the puley directly above the drain hole. The belt runs up and down through the drain hole.

Setting up swing arm drives is also quite fiddly. I made one that was OK. It has the limitation of no reverse. There are photos back through this thread. If you cannot find them I can have a look but not for a few days.

 

New Boat

I have now taken the proa as about as far as it will go. Has been modified quite a few times to improve it and its now a good reliable boat. Only problem with all the changes is every time I do something the weight goes up. Currently the boat weighs 43kg, including the gearbox. I have started designing a new proa based on what I have done with the present boat. Going to stick with the proa concept as I don’t have to put a hole in the hull and can launch off the beach. New boat will have one outrigger pole which will double as support beam for the seat.
Rick, saw on your photo gallery the 4HP_Racer, looks very fast. Is this your new Murray Marathon boat? Is the square stern to stop the aft end squatting in the water at speed?

Ian

 

Ah, the weight challenge. That's the ultimate once you get other things honed down. I'm constantly working on that myself. Ultimately I had to stay away from metal as much as possible. Lightweight alternative to metal gearbox and flex shaft if possible. CF construction if you can justify cost. I had to go with the lightest frame Al parts and inflatable hulls to keep cost down in my case. But the rewards of having a lightweight, collapsible unit have been worth it for me.

Porta

 

folding prop

Rigged up folding prop from RC glider to my flex shaft. Haven't had a chance to test on weeds and leaves yet because of the huge rainfall we've had, which clear out everything. The spinner is larger than Ricks setup and much larger than I would like, but it's a start. Just to see if the concept has possibilities. So far it can handle 50 watts easily, but don't know what happens when the blades impact something solid. The hinges are composite and only 8mm thick. Also notice that they fold back too far and are hard starting up (unbalanced) while submerged. Putting in some restrictors so they remain partially deployed....

Porta