questions and ideas for rob denney

In terms of performance and ease of building, it is a negative, as long as the hulls can be pitched upwards. All the cruisers have it as this is not viable with crew weight. The tender, the small boats (water taxi, canoes) we've built in Fiji and the cargo proa don't.
The small boats can be pitched bow up with motor or crew, so it is not required. In a month or so, we will have a couple of near identical canoes which we can attach to a beam and tow test with differing amounts of pitch to see the effects.

The cargo proa was an experiment to see if the boat could be made to pitch up (in both directions) without it. This may or may not have been possible with the solutions we had, but is very easy with the kites. If it hadn't worked, it was easy enough to chop and change it.

Easier beaching is possible if the bow is too heavy to lift. I hadn't thought about faster shunting speed, partly as with the schooner rig, the limiting factor is the speed the aft sail can be trimmed in. It would be worth doing some tests.

We are using ski tips for dynamic lift once the speed is high enough rather than full length rocker. Back in the days when I was playing with rockered hulls, the boats would tend to pitch forward and sail on the bow section. Getting them to sit level or on the aft section was a struggle. In those days, it was generally stated that all proas sailed bow down. Once we eliminated the rocker, this didn't happen.

 

We have not done any serious analysis of the boats required as it will be years before we make an appreciable dent and there is more pressing research required. There are several hundred, maybe thousands of fibres/pangas/banana boats in Fiji, similar per capita density in other island nations.

They are near enough the original Yamaha designed boats from way back when. Hand laid fibreglass/chopper guns from 17-30’. There are 2 manufacturers in Fji, turning out 3 or 4 boats a week each as far as I can tell, which is not very.

The fibres are excellent for the task; bullet proof, good sea boats, fairly stable, big load capacity, although the regs only allow about half of what they often carry. However, they need big outboards, 40 hp minimum to get the smaller ones up and planing with a load, 200+ for the bigger ones. Petrol is expensive, imported and emits CO2. 2 strokes are still legal, about 60% the price of 4 strokes. The damage they do is quite obvious in some of the river systems we have been looking at. “My grandpa caught arm (length) fish, we catch finger (length) fish”.

There are also 4-5m hardwood skiffs. These are often built by a local business which hires them to the villagers. A year's rent is often enough to buy a new boat, but cash flow issues stop this happening. These are heavy, leak, rot, aren't self draining, are poor sea boats, but cheap.

Finally, there are the rafts (billi billi) which are a dozen bamboo poles lashed together for near shore fishing. Better than wading out up to your waist and casting a line, but not much.

We are building boats to replace all these. The recycled PET foam/fiberglass/bio epoxy replacements are the same length, but more specialised. Eg, the water taxis are landing craft style for easy planing, high loads and stability for use in flat water. The tender type is a catamaran, better offshore, self draining and more stable than the fibres, the fishing canoes are light, stable and carry big loads. All of them can be built in the village hall without power tools and are lighter than the local boats, but will require more care. This is part of the education program along with teaching maintenance.

We are also putting solar panels on some of them, but due to stability, windage and potential damage, this is not always as good a solution as batteries charged by on shore solar. The motors for these are cheap units which can replace the petrol motors in conventional outboards. Once we get our 3D printer running, we will be making our own small outboards.

English is pretty much universal as a second language throughout the Pacific (maybe not the Philippines and rural Indonesia), as is the need for low cost, easily built, low maintenance boats. The pilot courses we ran last year have been turned into local qualifications, next step is to get them regionally approved and throughout the Pacific. Training people to build and maintain their own boats is far more sustainable than giving them boats.

 

I’ve another question for you Rob. My understanding is that the balestron rig/cat schooner rig on the HPs use bearings at the mast step, with the boom fixed in place on the mast. What’s the advantage to this over fixing the mast to the boat, and then having the boom and the halyard sheave attached to bearings so they can rotate around the fixed mast? I’m imagining giant bearings just dropped around the mast from the top down, and then secured in place…. Seems like it would be easier to service/replace these than bearings embedded into the deck and below (mast can stay in place) and that they would only need to handle sail loads and be spared the bare pole windage at anchor, and perhaps more significantly the self righting buoyancy force in the event of a capsize.


P.S. really appreciate the time you’ve spent discussing these rigs on the various forums - I’ve gone from “surely there’s a way to use my jib efficiently off the wind” to “sounds like I should build a HP” real quick!

 

how does the sail track revolve around the mast if the boom and sheaves are ?

 

Marvellous, keep them coming.

I tried this on the cargo proa masts when we were playing with the telescoping wing sails. It is more complicated than mast bearings and is one of the reasons we struggled to make the wings work.

Because of the large diameter, slow rotation speed and (relatively) low loads, the in boat mast bearings are simple. I have used sheet plastic bent into a circle and pvc drainpipe on the smaller boats. On the Cruisers, they are machined from a block of UHMPWE, a common engineering plastic. Cost a couple of hundred bucks. They are fixed in place and only need supporting horizontally. The thrust bearing only supports the weight of the rig so only needs a thin piece of plastic under the mast.
Halyard blocks on bearings at the mast head are difficult to maintain and check.
Both halyard bearings need to be located vertically, which is easy enough at the top, not so much at the base. Top and bottom bearings would probably need to be roller type so they would rotate as the sail aoa changes.

A big advantage of unstayed rotating masts are that the sail can weathercock, regardless of the wind direction. To do this on a fixed mast requires hoops holding the sail to the mast. These are pretty effective on constant diameter masts, but hopeless on tapered masts as the top ones are oversize when hoisted. On Bucket List I used one piece strings instead of hoops, which worked OK, but took a while to get the slack out. Might have been quicker with blocks instead of string on string. There is scope for development here.

The capsized loads on the mast are pretty small as the rig acts as a sea anchor and the boat is quickly blow downwind. With enough windage and a wave to lift some of the sail off the water, self righting might happen. Might not too, which is why we came up with the (near) idiot proof sheet release triggered by a float which dumps the sheet when the windward hull reaches a preset height above the water. Idiot proof as it works for pitchpoles and heeling, regardless of whether the sheet is cleated, on a winch or wrapped around your ankle.

Thanks. Suggesting people look outside their comfort zone does not always get a good reaction. ;-) It's nice to get acknowledged occasionally.

 

Was also thinking mast hoops or rope loops a la gaff rig rather than a track here, but wasn't considering the complication of a tapered mast. Makes sense that this would lead down a rabbit hole of more and more complexity without much gain, which is rather the antithesis of this rig design.

So the mast bearings are effectively just concentric plastic tube sections, with the outer glued to the boat and the inner glued to the mast, and the thrust bearing is just carbon fiber resting on a plastic sheet?

Very curious about how this works, primarily about how you determine the height of the hull above the water?

 

True, although still a lot lower cost and less to go wrong than an alloy track bolted to the mast, roller cars and expensive batten ends.

Even simpler. The bearing (with a couple of layers of brown tape on it) is used as a cast for an epoxy silica mix which forms the inner bearing surface. In the early days with thin wall bearings, machined bearings were rarely perfectly round as the lathe jaw tended to squash them. Consequently, the casting was not round and needed to be sanded. A strip of 60 grit pulled back and forth around the mast until they fit. Ten years later, no obvious wear. [/QUOTE]

 

Crazy that the bearing can be so simple, but I guess it’s just waving around every now and then, not doing 3k rpm in a hot engine…

Neat idea - something I’d have a hard time trusting to not trip accidentally in weird waves, though I guess there’s no danger to it and it’s easy enough to just pop it back in the cleat and sheet in again.

Careful what you wish for!

Next question is about kites: is there a benefit to a proa here? More generally from a design standpoint, what do you need to sail upwind on a kite? I imagine you need some sort of center/dagger/HP rudder boards to satisfy the “wing in 2 fluids in relative motion” thing? Is righting moment still needed?

Silent yachts has a kite system as an option, but there’s very little info on it I can find. Seems like it could be a great cruising setup going on solar for short jumps, and the kite for long ones. However if there’s no need for the righting moment, can you scrap the multiple hulls or heavy keel and cruise on a power monohull without the associated diesel costs/eco guilt?

Sounds too good to be true, but so does the HP and you’ve managed to make that work

Also is there any way to see the older incarnations of Harryproa.com? I find a lot of links to it in various threads, none of which work anymore. Seems like there was a lot of good info on there that would be a shame to lose.

 

Sorry for the delay. Issues with the electric car shipping, plastic recycling politics, a couple of food poisonings and the internet. Plus a couple of weeks of full time teaching and firming up a C50 to build in February. Fun place! All under control now. I think.

Simple is always the target. I prefer starting with light simple and cheap and adding complexity, weight and cost rather than the other way round. Often means things don’t work initially but you get a much better understanding of what is involved.

Making it work below the waves involves a little more drag. If the waves are gnarly enough to trip it on a cruising boat, it’s probably time to think about easing off

Not at all. Ideas and discussion are why I use forums. Describing what I am doing and why helps clear my thinking. Plus a lot of good ideas have come from contributors.

Kites are easier on proas due to shunting. Same as on kite boards. There are some interesting kite discussions going on at HarryProa groups.io Group https://groups.io/g/HarryProa

Yes. Also handy for steering if the kite is not powered up

No.

$20,000 for an untried system was enough information for me. OKE also has one, but also too expensive at the moment

Get the kite sorted and it is fine for short trips. Much quicker and easier than hoisting and trimming sails

Yes, but there are a few things yet to be sorted, such as launching and retrieving. Systems are getting better for this but none that I know of are cruising boat ready.

Ta. Our kite solution is a bit different. We share the zero heeling, low loads and costs attributes but in the interests of being able to launch and retrieve we lose the benefits (and drawbacks) of more breeze up high and the ability to increase the kites apparent wind by figure eighting . Our solution is also improving. The latest iteration is being tested in NZ this week, has easier handling, shorter mast than the current one.

The Wayback machine usually works. Wayback Machine https://web.archive.org

 

Oooooooh wow that’s so clear in retrospect.

Heard. These guys: https://libertykite.com/en/produit/libertykite-40m²/ sound like they're on a similar track to you (kites up to 80m2!), and the pricing is a little better but I think they're skipping the mast for retrieval and just hauling them out of the water.

Thanks for the groups.io and way back machine links - looks like my reading list just grew exponentially! I’ll give those a read through before bombarding you with more questions you’ve probably already answered elsewhere…

Maybe just one though: it seems like every multi I’ve come across has daggerboards through the hull rather than the beside the hull as you have with the HP rudders. It seems crazy to me to willfully put a giant hole in your boat, which in a grounding is going to get battered from the inside out, unless there’s some massive performance advantage. These are quite expensive performance oriented boats, so is it just a matter of cost being no object, and any little improvement being worth it? Or is there a significant performance penalty (my layman’s understanding is ventilation makes the top part of the rudder not really do much and make some extra drag) to putting them beside the hull?

 

They are doing cool stuff, but it's pricey and does not go upwind. Pulling kites out of the water is a mug's game.

Look forward to it.

"Crazy" pretty much sums it up.
1) Hitting something solid (whale, container, big log, ship) at speed will either:
a) break the board, then break the saildrive (equally crazy) and rudder.
b) damage the case necessitating slipping the boat.
c) not break anything, in which case the crew go from 20 knots to zero very quickly. If they aren't tied on and there is a bulkhead or a stay in the way, the injury will be severe. It is weird how many offshore 'experts' sleep feet forward so they don't get head injuries in a crash, but don't worry about it when they are awake. Check out the car crash tests at 25 mph (22 knots) to see what happens to the occupants.
2) the cost and weight of beefing up the case to withstand impacts is not trivial. Even less trivial is the cost of repairing/replacing boards.
3) making a board that kicks up in a collision is not hard. Either a Tornado catamaran style (these were the fastest beach cats pre foilers, so the boards can't be too bad) or a long case with the slot aft of the board filled in with something to smooth the slot but collapse in a collision. The downside is a small loss of internal space. A crush element in a slightly larger case is ok at low speeds with a light boat, pretty useless at high and heavy.
4) The added drag from surface piercing foils with a side mounted foil is negligible, although the design of such is tricky. It's taken us 20 odd years to get it right, and there is still room for development. The potential for ventilation exists, but is pretty easy to design for.
The only reasons I can think of for having daggerboards on a cruiser are following fashion and/or death wish tendencies.

 

The current Americas Cup boats are using surface piercing foils to great effect so it can work, If you look at the foils at the waterline some or maybe its all have a streamlined blob which I imagine is used to create an endplate effect though it may also work like the tubercles of whale fins, if you put tubercles in the search function here there is some discussion.

 

G'day Rob.
A few DIY unstayed mast queries. I've seen pics of a mast half-mold for a C50.
I assume the mold frame has to be fully planked and glassed(?) to make a seal for infusion?
Do you supply CNC cutting files for the frames?
What is the design and procedure for joining the two halves?
With a balestron, how is the boom attached to the stick?
Reading your description of the bearings is reassuring. Simple is good.

I'm interested in the Ex40. For simplicity and reduced cost/time, with a single mast balestron.
For visibility, light, and entry headroom, a small Cruiser-style cabin top.

 

It is a straight taper, so any piece of airtight material that can be bent to shape will do. Fibreglass sheet works well as it is easily joined on the back side and the laminate can be varied to get the curvature. The flanges for the bag seal can also be included when it is laid up. At least 2 layers for airtight. It does not need to be shiny or smooth, just fair.

Can do, but they are semi circles, so easy enough to draw and cut. The mould surface smooths out any wobbly cuts, the flange keeps it straight.

An inside lap join, explained in the plans, as are the single line (for all reef points) reefing, carbon rcb mast track and the dead simple halyard lock (not possible with the ballestron). The mast join does not need any fastenings (temporary or permanent) across the join.

Burger: With a balestron, how is the boom attached to the stick?
Rob: Depends on the system. I've gone off balestrons in favour of schooners, but it would be easy enough. All it needs is a lump on the mast to locate the boom fore and aft and up and down with enough laminate for it to be able to turn the mast. Can do it more complex than this, but this works.

Burger:Reading your description of the bearings is reassuring. Simple is good. I'm interested in the Ex40. For simplicity and reduced cost/time, with a single mast balestron.
Rob: No problem.

Burger:For visibility, light, and entry headroom, a small Cruiser-style cabin top.
Rob: Easy enough, although it may look a bit top heavy if you want full headroom.

 

This popped up on my YouTube.