Pedal Cat design

[Peddler]

Hi there, I have been building bikes and recumbents for some time, but I am new to boats.

I am trying to build something like this:E45447C9-58D9-474A-BF87-5723D84CC019.jpeg

I plan to use it on the rivers and lakes of the uk, nothing very rough.

me, gear, and the pedal drive should come under 100kg, I’d like to be able to hold 6mph. I can produce 150w continuously.

how do I go about designing and building the fastest possible hulls? I am open to trying different construction methods.

thanks for your time!

[P.I. Stazzer-Newt]

Fastest?

[Peerie Maa]

Researching this might uncover something useful.
THE WATER CRAFT MAKITA CORDLESS CANOE CHALLENGE

Published November 17, 2017 | By Beale Park Team

Organised by
Sponsored by
It started as a silly idea: a weekend tournament for boats, any kind of boats under 16’ (5.3m), powered solely by cordless workshop power tools, racing against each other at the Beale Park Boat & Outdoor Show. And funnily enough, over the past 5 years the silly idea has become more serious with some boats now purpose-designed and built for the Cordless Canoe Challenge (CCC) – maybe that’s down to the great power tool prizes from sponsors Makita UK. For 2018, we’ll have:

[Peddler]

Fastest?

ha not really fastest, I want to be able to cruise for 5-8 hours at the fastest speed I can, not the fastest for a 10 second sprint.

[Woxbox]

The fastest catamaran hulls have U-shaped hull sections and are about 12 times longer on the waterline than the width. For example, an 18" wide hull that is 18' long. Skinnier and longer will give more speed potential, up to a point. Take the formula too far and the "wetted surface" of the craft will create excessive drag from all that hull in contact with the water, preventing any real gains from that fact that the hulls don't make significant waves.

The practical limit tends to be what length boat you want to cart around. More than 20' gets difficult to store and transport.

The drive unit is just as important as the hulls. Propeller size, pitch and speed are all critical. If this were my project, I'd start with an old beach catamaran platform and refine the drive system first, and then build some faster hulls to go under it. I don't know how it is in the UK, but in the US you can pick up old beach cats on trailers for next to nothing. Something like an old Hobie 18.

Sounds like a fun project. Good luck with it.

[Three Cedars]

Probably you have seen this website already http://ihpva.org/water.htm the archives might hold useful info

[P.I. Stazzer-Newt]

Any of the A class cats should have hulls which look promising

https://www.unicorncatamaran.org/tech-specs the unicorn is a classic example

Which British rivers had you in mind?

[NeilMB]

Rick Willoughby is one of the masters of this type of design. https://openwaterbike.com/ has some of his ideas. He has also designed pedal drives for a number of the Race to Alaska teams. You could consider contacting him directly with your questions.

[MattMKE]

I think any catamaran design is going to be relatively fast. But if you just want to try something before committing to the fastest possible design, could you make a cat out of two cheap used kayaks of the same manufacture/model? 10’ used kayaks here are plentiful and cheap here at the end of summer.

[Peddler]

Thank you for the thoughtful reply.


I guess I should have given you more info. I think the maximum length that is practical on the rivers I want to travel is 5m. Any longer than that will be difficult to manoeuvre. Obviously this will effect potential speed.


I think any standard beach cat is going to be too big for my pedal purposes. I have been looking at kayakats and the like.


as you have suggested my plan is building the drive unit first and then trying different hulls underneath.


id like to make the boat from plywood initially, but I am a bit lost on how to design the hull profile.

[Peddler]

That’s is a cool design, are the plans freely available? I have emailed them.

im planning on doing the Thames, the Ouse, Medway and other rivers in the south east.

[P.I. Stazzer-Newt]

That’s is a cool design, are the plans freely available? I have emailed them.

im planning on doing the Thames, the Ouse, Medway and other rivers in the south east.

If you're talking about the unicorn, then plans and build method are sort of available follow the link I gave above.

If you're thinking of sub 5 metres then there's a lot to be said for white water race kayak hulls - buy an old one, rip off a hull mould - ignore the deck- build a second hull and off you go.

All of the rivers you mention need the appropriate licence, if this craft is a canoe (flexible definition) then the lifence comes free with BCU membership

Portage around locks could get entertaining.

WWR boats are 4.5 metres long and, at the waterline, about 500 mm wide - a slippery shape - out of date examples can usually be found in the UK for very small money - this one cost me six quid and a couple of hundred miles of driving.

sicksquid.jpg

[rgthom]

This sounds like an interesting project. Your goal of 6 mph with 150 W input might be do-able on flat water, but it is probably as good as it gets for a 5 m displacement boat and will take efficient hulls, an efficient drive system and light weight.
Are you looking for an existing catamaran design to modify for pedal power? There are a few rowing catamarans, member Clarkey here turned me on to the Pattino boats from Italy. There was an article in Woodenboat from a recent builder: https://www.woodenboat.com/timeless-pattino



Plans for a similar boat are shown at Duckworks in the US. This Moschino is right at the 5 m length. Displacement is listed at 135 kg, but it can take two people and hull weight is not listed. Umbrella not required...
https://duckworks.com/moschino-plans/



This may seem a bit more substantial than your first image, but I would keep in mind that the rivers you mention can still have some strong wave areas and a boat with more buoyancy able to ride over might be more practical if somewhat slower on the flat.

-Rick

[NickW]

Have you seen the RUMCAT 3.1 VB by Rumble Boats. From Practical Boat Owner mag https://www.pbo.co.uk/news/new-boat-...nd-power-66909

6. RumCat 3.1 VB – Variable beam catamaran paddleboard

RumCat: 10ft x 34in but can be wider or narrower depending on usage

RumCat 3.1 – can be supplied as a kit or fully finished.

Neil Rumble at Rumble Boats sent us this: ‘It’s taken a while (3 prototypes) to get it fully sorted for production but here is my new design of catamaran paddleboard, the RumCat 3.1 VB.


‘I think I can claim its the worlds first variable beam paddleboard. This one is 10ft x 34ins but can be wider or narrower depending on usage. Ideal for novices/experienced SUP, or as a sit-on kayak, sailing, motoring, yoga etc.
I can supply a comprehensive kit or fully finished. Simple and quick to build. Flat bottom, 3mm & 4mm gaboon ply, standard stitch and glue, epoxy sheathed. All up weight around 14kgs.
Cheers Neil!

May give you a few pointers.

Nick

Edited to add that the embedded FB link above doesn't work. Contact details for Neil are as follows (taken from Ad in the latest issue of Watercraft) neilrumble@aol.com landline 01258 858712 mobile 07866 041680

[Peddler]

Due to portage I was hoping to make the boat a small and light as is practically possible, without compromising speed too much.

when I originally started thinking about a peddle boat, I imagined a kayak, but in reality I don’t see how you can stabilise a kayak without a paddle. You could add outriggers I suppose for a kind of trimaran. Im thinking I might start an different thread more broadly about pedal boat designs.

[Clarkey]

Remarkably, after years of procrastination I am actually building (or rather assembling) a Pattino-like catamaran. Can't talk about it here though because it won't have an ounce of wood in it.