Pedal Powered Boats

http://www.bbc.co.uk/news/uk-england-devon-36993834

 

100m below the surface ?!
That thing doesn't look That sturdy.

 

David,

Great idea.
Are you volunteering?

 

Looking at there website at http://www.projetpoissonpilote.com/en the pressure vessel looks substantial.

 

Best outrigger design for pedal trimaran with very long, narrow centre hull

Hi all,
I recently acquired a beat up carbon fibre Olympic racing type single scull hull for my trimaran project. These are available very cheap if no longer competitive like this one especially if the sliding seat and outriggers have been lost as was the case with mine.
To dispose of them they have to be cut up and go to landfill- and we're talking a 26 foot long tapered tube- so every rowing club seems to have one or two kicking around on the outside racks- with various bits missing and never to be sculled in again.

I was not willing, when it is possible to purchase such a beautifully efficient hull for less than the cost of a kg of epoxy at the yacht chandlers, to struggle with designing and building my central hull from scratch.

Oh, I should have mentioned at the beginning this is a Mirage Drive (too much weed and shallow water round here for an efficiently sized prop) pedal trimaran. If it works nicely, I'll perhaps go the prop route also so I can compare the two systems on a super efficient hull.

Talking about propulsion, I have a view that people who say the Mirage drive is hands down inferior to a HPB type prop drive are forgetting an important point. While I agree that you can take a fixed power output and put it through both devices and see that a large diameter slow spinning prop is a more efficient use of ROTARY POWER, it's only considering the boat end of the process. This is because we tend to measure power using rotary shafts. If you start off with rotary power like a motor or engine, it's highly inefficient to change it into reciprocating motion and only ever complete half a revolution in each direction- when you have a rotary motion- don't for goodness sake change it to a stop/ start motion. But humans don't really output rotary power. They can do through cycle cranks- but much of the crank rotation is inefficient in its use of human physiology. At the human end is an organism that has evolved over millennia to produce something much closer to reciprocating leg power (walking, running)- not rotary leg power (cycling). This important part of the equation is usually forgotten about and I think levels the playing field a fair bit. It explains why the Hobie Mirage Drive appears to work better than basic scientific comparisons suggest it should.

Back to the boat, the drive box is epoxied in. The rudder is fitted. I had to extend the saxboards a couple of feet forward, as when you sit the right way round (Rowers of course sit the wrong way round) and kick your legs out nearly straight, the weight distribution changes a bit and I don't want the tail to squat. Anyway, I worked it all out and the C of G is now the same as it was when it was being sculled.

I still haven't got onto my question...
Outer hulls, Amas, whatever you want to call them, I sure as heck won't be able to stay the right way up for long without them. I have many ideas, but I guess folk on here have tried many of the dead ends before me.
My main principle: They don't need to be very big if they are a long way out (within reason!) and perhaps not permanently touching the water- they really are just subtle stabilisers:

Ideas:
SWATH stabilisers made from torpedos of PVC pipe (probably about household downpipe size). Advantages: Cheap materials, relatively light- only real job is making the fore and aft hydrodynamic end caps- but there has been a recent explosion in amateur rocketry (pun intended), so long, beautifully tapered plastic end caps can be bought quite cheap.
Disadvantages: How much righting moment do submerged hulls provide? I'm thinking less than surface hulls. I envisage using SWATH stabilisers might make the boat continuously roll about its main hull, albeit in a slow- very damped fashion- so their actual stabilising ability may be insufficient. They are always under the water creating (skin and appendage- but not much wavemaking) drag- other stabilisers might not need to be in the water at all most of the time.

Flat skimming, buoyant 'slapper hulls' Advantages: I already own a pair. I made them for a single scull I wanted to use in open sea conditions, and for this purpose they worked very well. I mounted them about 2 inches above the water level so they only slapped the tops of waves or to prevent disaster when required. They are square in profile, foam, glass, epoxy- actually long thin chunks cut from the central area of a windsurfing board then glassed over.
Disadvantages: With the Mirage drive, I might not get away with having them mounted high up above the water balancing on just the central hull for long stretches- they might nightmarishly slap down alternately every foot stroke. This may mean that they end up being adjusted to be permanently touching the water, in which case they will be draggier than fine, displacement hulls. Has anyone ever put a Mirage drive in such a fine hull? How hard does it try to roll about during the pedaling motion?

Angled hydrofoils. Advantages: This is my favourite idea, I would mount the foils at about 45 degrees tip inboard angle. They would need static buoyancy above them for when the boat isn't moving- probably the foam slapper hulls mentioned above- but to be honest a couple of 2 litre lemonade bottles would probably do just as well and be lighter- they will be out of the water once the boat is moving. Could they (depending on where placed fore and aft, start to lift the main hull up out of its displacement hole a bit, reducing its drag? I'm not talking about full foiling- I've seen how marginal and hard that is with a fully optimised HPB prop. I'm talking about foil stabilisers that lift the main hull bodily up out of the hole it is displacing by perhaps a few centimetres, thus reducing part of both its skin and wavemaking drag.
Disadvantages: Will be a pain to make (properly). I could initially make them (not properly) by getting two identical windsurf fins and belt sanding the bottom, high pressure, side of them both flat- just to get a feel of whether it might work. The aka (crossbeam) will need to be stronger and hence heavier- especially if I'm going for a bit of main hull lift from them. Everything will need to be made adjustable so I can get the trim right- again more weight.

And, last but not least... Dispalcement Hulls. Advantages: Proven technology- there is no chance they won't work reasonably well. I've got a pair of 7 foot stitch and glued plywood amas in the loft from an old project- but they would probably be a bit big and heavy for this. They are also hard chine and I'd be happier with a more efficient u-shaped underwater profile for this project.
Disadvantages: Not as 'interesting' as some of the above ideas. Who wouldn't like to say they have one of, I expect, very few foil-stabilised or SWATH-stabilised pedal trimarans in the world?

Maybe I need to start by making a pair of hulls and then start experimenting from there? What have people done? Any advice for making light, cheap, efficient stabiliser hulls?
Many thanks
Jake

PS, I originally thought the whole vessel idea up when reading the 'Best hull for a Hobie Mirage drive' thread years ago (might not be on this forum). What delayed it, for years, was getting hold of a good, used Mirage drive. Once I got that- I was able to acquire the hull a week later. The reason I've not posted my question on that thread is to not take away the element of surprise. I'm hoping to get the boat up and working well before I post on there. There are a couple of other elements to my design that I've not yet mentioned and I'm hoping will be quite surprising.

 

I think you're bang on with the slappers.<cough.>

Exactly what Rick Willoughby uses:

http://www.rickwill.bigpondhosting.com/V11.htm

His are mounted just above normal waterline. Rick and Greg Kolodziejzyk have experiemented with foil stabilisers and IIRC found them fiddly and draggy.

I have used drainpipe stabilisers and found them draggy.

 

Yes, thanks for the heads-up TT, as I said they were surprisingly good on a single scull.
I've always wondered why the adaptive rowers use little displacement hull stabilisers. As these sort of stabilisers are only about 2 feet long they will want to plane at only a couple of knots on a boat that will be normally expected to cruise at about 8 knots.
Just because the centre hull is a displacement hull- it does not mean the stabilisers cannot be planing hulls.
I once rigged mine at water level on the scull to see how they looked underway. They were definitely planing, skipping along the surface.

I guess the unknown for me is how far above the water I can set them with a Mirage Drive propelled hull, ie., how easy it will be to balance the boat- but it will be fun finding out. Remember it's not like a kayak and not wide enough to get my bum inside- so I'll be perched on top a bit.
An easy way of making these stabilisers a bit lighter than my foam ones could be with square section PVC downpipe. I expect it would bend easily with a heatgun to curve a bit of bow rocker into them. Bit of a plywood/ epoxy grid inside them to screw the mounting points in the middle into and the job's a goodun! Mirage drive world speed record here we come!

I didn't mention in my original posting that I'm also making the main hull sectional and hinged for easy storage. It will fold (in a slight zigzag- so bulkheads not completely perpendicular to the hull) into three sections each about 8.5 ft long. With some thought I've worked out how to do it without losing the straightness and efficiency of the hull- ie., not creating any steps for the water flow. I'm building each set of two bulkheads together- pre bolted together with the fixings and hinges that will hold it together when its finally part of the boat- with a few spacers of 1.5mm balsa glued between them. I'll access the deck canvas with holes cut where I want the bulkheads - Carbon tape/epoxy/ fillet in the bulkheads each side - then remove the fixings and run a 1.5 mm wide wood saw in one go through the balsa spacers and the hull. Then finish the outside parts of the bulkheads with a layer of thin carbon cloth/ epoxy- the two of which will make up my lost 1.5mm. HOPEFULLY this will result in a boat that stores at about 9 ft long max, but has that 25 foot waterline length when folded out- but forms a straight, fair hull when done so.

This bit will have to wait til the spring though as I have nowhere indoors that's 26 feet long and it's too cold outside for epoxy now.

 

If you have a heat gun you can reshape the ends of pvc fairly easily with a little practice.

 

Rick's V11 at 230mm is likely even narrower than your scull shell. However, it has a rectangular section hull, and is likely to have higher initial stability if your shell has a rounded cross section.

If your shell is a round cross section I suspect that balancing it (without oars) will be extremely challenging.

The rationale behind setting the outriggers just above the normal waterline is that the 'normal' condition will be with just one outrigger float in the water, and there is the possibility with practice of balancing the hull with both floats out.

my only experience of attempting to balance was in an 18" wide square section canoe, and I found the balancing so difficult I ended up setting both floats fairly well into the water.

Perhaps it is worth making the altitude of the outriggers adjustable for easy experimentation.

One area I would devote some thought and experimentation to is the length of the outrigger float.

If you are sure you can maintain them in planing mode, then I suspect that shorter will be good, as long as you maintain enough righting moment (through both buoyancy and planing action.) If you find that the righting moment needed is tending to push the outrigger float deeper in so it is operating in displacement mode, then shorter is likely to be more draggy, and you may get on better with (much) longer skinnier floats.

 

Yes, I'm planning on making everything adjustable, from seating position for trim to outrigger height and angle of attack.

 

Jakeeeef, I did a tri powered by cordless drills a few years ago (for a competition) using an old slalom canoe as the basis - not nearly as skinny as your boat.

I started with plywood displacement floats 8ft long, 6" wide on deck and about 2" wide on the bottom. They had far too much bouyancy and weight for the job so I replaced them with floats made from 68mm downpipe; one length cut in half was enough, with a flat "transom" and a tapered bullet shape cone at the front made from extruded PS foam as used for house insulation. They gave plenty of stability at 6 ft centres. Neither type appeared to cause much visible wake at about 6kt.

I really like your idea of angled hinges to allow the folded ends to overlap, please link, or post some pictures when you have something to show us.

 

Thanks Alan,
I'm a great fan of the Cordless Canoe Challenge and every year cannot wait to see the entrants on the video that Pete puts on Youtube a few weeks later. It is firmly on my 'to do' list.
(I have a plan for an outboard motor type drill drive that will simply clamp onto any transom - just waiting for the price of lithium ion 18V drills to come down a bit more). With the outboard drive approach, I only need to do the difficult (mech eng.) bit once. I can then try it on multiple hulls over successive years, and I have a number of plans from displacement cats, to planing cats, to stabilised tri to, ultimately full hydrofoiling.

The zigzag folding idea is one I came up with almost by accident. I knew I wanted to section the hull and was initially thinking a split somewhere in the middle so it went into two pieces. Then I thought I'd always be storing the bits together so why not put hinges in and make it fold? (All sectional rowing boats just bolt together and so come completely apart- so they can be put side by side on a roofrack etc.)
My original concern was how I would get the bulkheads glassed in completely perpendicular to the hull so when folded it would look nice and symmetrical- just one degree off would make the fold two degrees off- which with a 13 foot long section would look really obvious. Then I thought why not embrace the idea of the slight zigzag fold- into three parts so that the bow and stern overlap each other and sit each side of the centre section.
Another point on this is safety. With this in mind I might make the centre section as long as is manageable for me storage wise (about 12 feet)- which also should leave it with enough volume if not swamped to support the occupant in case of the bow or stern section snapping off. The bow and stern sections would then be (26-12)/2 =7 feet long each.

If that was the approach the zig zagging would in fact not need to be significant and would be actually achievable with plumb bulkheads and by putting undersize pins in the hinges to introduce a bit of play when folded to allow the bow and stern sections to be pulled laterally a few inches each way. With a 7/12/7 sectioning the overlap of bow and stern will be 2 feet- and this boat is only about 6 inches wide 2 feet from the ends.

I'll also make the crossbeam (25mm carbon tube) and outriggers store inside the general shape of the folded package. The Mirage drive will pull out for folding and should sit in the scooped out area which is where the sculler's feet went when it was a sculling boat- but mostly it will be kept separately under lock and key as these are not cheap or easy to replace.

 

Pedal Power?

Pedal Power?

https://www.youtube.com/watch?v=uvU2f-t612o&feature=youtu.be

Note that the blade is horizontally when it moves forward, minimal wind drag against the wind.

js

 

What a lovely video. While feet rowing is clearly physiologically and mechanically interesting, the clearer message for me is how happy it is possible for people to be without owning tons of plastic and/or electronic rubbish.

 

Anybody who is making a video is going to try and look happy.

What about the video camera?

Looks like aluminum from old airplanes, I guess that's better than plastic?