Getting out on the water this year

What does your design brief look like? What are your requirements for the boat? What do you want to use it for? What does your budget look like?
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Manik
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Re: Getting out on the water this year

Post by Manik » 02 Feb 2015, 00:45

A pod would provide a place to sleep, but I imagine that while the boat is underway, I'd probably want to sleep with my gear on, on a net spanned in the aft part of the cabin, so as not to put my weight to leeward. On a boat this small, it really does make quite a difference. If I'm 0.6m to leeward of the vaka centerline, and the ama is 4m out from the vaka CL, then with my 90kgs, it would take 13kgs of water ballast in the ama to cancel that out. That's not tragic, but it is about 2% extra displacement overall, and a loss of about 5-10% of the RM of the boat, if the ama has a 100-200 liter ballast tank. Sleeping on a net in the vaka, aft in the cabin, also helps get weight aft and gets the bow up a bit (at least while I'm lying there), which is good.

One final point for tonight, is that I will definitely have interior steering, so I'll have a hexagonal cupola ontop of the vaka, sort of like the one on the Jester 32 renderings. That cupola will also double as the hatch, and I plan to run all the sheets, tiller extension, and rudder up- and downhauls into the cabin, so that I can do everything except reefing from the interior steering station. I think this an absolute must for sailing in low temperatures with a boat like this. Staying dry is essential. In better weather you can just open the cupola and sit there out in the open, or open the cupola to the leeward side only, to get a bit of fresh air. I've been thinking a bit about the possibility of having a kayak-style skirt in the (open) hatch as well, but then you wouldn't be able to get at the sheets and steering. :? The reason I bring this up right now, is because it's very important for the design of the cabin, I really do need a certain amount of space down there. I just don't know yet which layout is the best way to get it.

Any opinions / ideas? What option from the previous post do you guys like the best? I hope I didn't lose you all with this rather long set of posts, and I'm really looking forward to hearing from you guys! :)

Cheers,
Marco
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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Skip
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Re: Getting out on the water this year

Post by Skip » 02 Feb 2015, 04:15

A few comments to cover several posts on subject.

Time and cost, P52 was built in 3 months (Nov, Dec and Jan) in an open covered area, don't have any idea about hours but I was rushing some of the time and effort was compounded by the fact that I didn't really have a clue about a number of things.

Initial cost was way less than $5000 US, more like half that, but I had the salvage cedar and a fair stock of glass scraps, used cheap plywood your mileage will vary.
Nomad is going to be built far better, but not gold plated and I don't expect to spend more than $3000 or so max. The essence of proa is lightness and the lightest stuff of all is the stuff that's not there.

Cassette quarter rudders transformed P52 was ok before far better with the rudders.

Sleeping underway implies two people on board (I think) in that case the sleeper does best aft. I'm not qualified to express much opinion on the enclosed steering and the like, such things aren't much use on the Texas coast in summer, shade however is golden. OTOH there's a definite need to be able to close things up when the wind dies at night and the mosquitoes come out (in formations).

I'd vote for 2(b) in the previous post, it's the lightest. simplest and I'm wary of the need for a pod in a lot of circumstances but don't have hard data to back up my suppositions. There's a lot of talk about the need but slim accounts of same being necessary or used, topic for another thread?

Cheers,
Skip
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claudio
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Re: Getting out on the water this year

Post by claudio » 02 Feb 2015, 07:01

Hi Marco,
Thanks for posting. This is a very interesting and enjoyable design concept.

A few thoughts from this end...

In the interest of keeping to the simplest/quickest build time...Why not go for vertical, plumb sides? The flare of the hull sides delivers no real advantage, adds to deck weight in relation to the bottom and is more complicated to build. (Every hour counts!).

Vertical sides would also simplify the attachments for the sidehung rudders (which are a great choice, btw!).

Bottom and deck could both be a simple 24 in wide, without any noticeable change to performance...and would make the bottom of the hull much more user friendly and liveable.

The 8 mtr LOA : Anything outside of the standard 8 foot lengths of plywood sheets adds substantial more work and more cost. Butt/scarph joints are time consuming and are costly. Keeping it to a 24 ft length might be worth considering.

The schooner rig is cool. Simple, powerful, safe.

Inside steering is definitely a priority and well worth figuring out. Nothing worse than "cold and wet".

Re the pod: The bigger 1.1 m width would be easier to build than additional add-ons...would be safer...and would also add substantially to the feeling of inside space, which should not be under-valued.

Hope this wasn't too long a feedback!

You're doing great Marco! Something really sweet is shaping itself...

Cheers for now,
claudio
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cpcanoesailor
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Re: Getting out on the water this year

Post by cpcanoesailor » 02 Feb 2015, 15:58

Hey Marco,

I like your design ideas. 470 rigs should work great if you can figure out stay placement.

Using daggerboards with cassette rudders works well (so far), but there are some gotchas: when you shunt, you either flip the daggerboards (up, rotate, down), or you make the cassette rotate through > 180 degrees. Flipping daggerboards means fixed tiller = easier. Rotating cassetttes means complicated tiller (flipping, or push-pull). I went with rotating cassettes and push-pull tillers, which means short rudder arms since the arms are between the cassettes and the vaka on one tack. Hopefully the helm won't be too tiring.

Also, watch out for 'feature creep'. I spent way too much time on making cockpit storage hatches (probably leaky), when $50 and 4 deck plates would have sufficed. Think - how many cuts, how many steps? I liked that the symmetry of proa hulls lends itself to repetition in building. I'm always faster and better the second time I make a piece.

If you haven't seen them, check out Claudio's build videos. That is the essence of simple and fast.

Looking forward to your design and proa,
Curtis
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Re: Getting out on the water this year

Post by timothy » 03 Feb 2015, 00:56

Looks good . I remember reading,I can`t remember where, that a safety pod relies more on dynamic lift than buoyancy and I am wondering if you were to just extend the blister deck outwards and add a slightly rockered and angled bottom , pram like ends and a flat exterior panel,if it would put more volume further outboard and provide more usable space inboard without increasing the beam or incurring a weight penalty. Of course it would not look nearly as elegant.
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Rob Zabukovec
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Re: Getting out on the water this year

Post by Rob Zabukovec » 03 Feb 2015, 07:05

Hi Marco,

A few comments:

1) Cannibalising old boats for suitable parts is a good idea...cheap and saves build time........
However, staying 470 rigs could be interesting, especially how to deal with the spreaders. The rig (possibly under strength anyhow for an 8 metre boat) will be even more so without functioning spreaders.

2) 420 rudder blades could be on the small and (especially) short side if you are trying to keep the cassettes up away from waves and spray. Maybe you could use centreboards instead??

3) Re the design, Option 2b would be my pick also.

4) The small topside splays seem to serve no real purpose that I can see, and are extra work for not a lot, so I would design them out somehow.

5) The underside of the pod could be splayed to give extra reserve knockdown buoyancy,some dynamic lift and extra space / storage inside.

6) Have you given up on spray rail steps to get some more space inside and help keep the boat drier???

Cheers

Rob
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Manik
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Re: Getting out on the water this year

Post by Manik » 03 Feb 2015, 14:44

Hey guys, thanks for all the feedback! :)

To clarify the situation on the rudders: I will use two 420 daggerboards (centerboards) for the casette rudders. I think the 420 or 470 rudders would be way too small for this boat, especially when in a casette above the water, and at a quarter position along the hull. I plan to use the rear rudder only (front one hoisted), and have a bidirectional daggerboard in the ama, in the interest of keeping things simple.

Where sleeping is concerned, I want to try to keep the boat moving some 16-18 hours a day, getting 4,5 - 6 hours of sleep at anchor, and then covering the rest with 15 min catnaps every few hours. I will be sleeping while the boat is doing it's thing, without anyone at the helm, on a pretty regular basis, though only for short periods. In the Gulf of Bothnia (north of Stockholm / Turku) there's basically no commerical traffic whatsoever, so up there that'll definitely be a workable solution, on the North Sea, I have my doubts -- I'll just have to see.

As for the pod, I'm still pretty divided between a pod and a safety ama. :? I'm convinced that having some sort of leeward flotation is an absolute must. How much, depends a lot on how you sail the boat, but if you're driving it close to the stability margin (which I can see myself doing), then having a pod/ama which stops the rolling early on as opposed to later, is probably more pleasant.

I agree with Skip's point that the lightest stuff of all, is the stuff which is not there. It's hard to say off the top of my head, which comes out lighter, leeward beams and a trampoline with an inflatable safety ama, or a single-berth pod... I figure they'd probably both come in about the same, maybe the safety ama solution would be slightly heavier on account of the beams. Where construction time is concerned, the safety ama vairant is probably quicker, but only so long as I leave the pod out entirely. Building a 30cm wide pod or a 90cm wide pod is probably about the same amount of work, so if I do need the space, then it's probably faster to just go all in for the pod.

If I do opt for a pod, then Timothy's point about making it fuller at its ends is a really good one. I haven't checked at what heel angle this pod makes contact with the water, but the angle at which it actually starts to carry something, is probably enormous on account of its curvature. A 'Madness' style pod, would result in a much lower final heeling angle, for the same width.

Cheers,
Marco
"Man's mind and spirit grow with the space in which they are allowed to operate." - Krafft A. Ehricke, rocket pioneer
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Rob Zabukovec
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Re: Getting out on the water this year

Post by Rob Zabukovec » 03 Feb 2015, 14:46

Marco,

Speaking about cannibalising old boats: what about finding a suitable small catamaran, cutting off the hulls at Bmax or thereabouts and joining the 2 bows to form an ama???

Cross beams and centre boards might prove useful as well??

Rob

PS With regard to sleeping whilst sailing solo, even catnaps, not a good idea anywhere near land (eg 100 Nm).....a fast boat can cover a lot of ground in 15 minutes, worse still if you oversleep or the boat steers off somehow in the wrong direction. I can recall crashes by at least 2 hugely experienced well known yachtsmen near the end of long voyages, because they relaxed and overslept, because they thought were nearly there.......

Long daysail hops are the safest solo option. you can go for weeks like that if you have to.Planning ahead is the key.
old school
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Re: Getting out on the water this year

Post by old school » 03 Feb 2015, 19:14

Marco,
Having no intention to discourage you (sure I think it is a good idea to make a start rather than ponder endlessly) but I do not agree with saving a few hours work on the basic boat and committing to many hours on detail stuff.

A single extra chine is not going to be a big construction demand, and the design provision for some flexibility in geometry will save cutting sewing/mending later on when you could rather be sailing.
People have spent a lot of time making brackets and hardware then changing them to strengthen or move them up from draggy positions on the hull sides. So if you are aiming on a reliable, quick build design suitable for the North sea, there are better options. Certainly there is a way to use boards (even large recycled dagger boards) hung between vaka and ama to effect steering as well as leeway resistance, without extra stuff like cassettes.

Also, the best candidate for a single chine flat bottom, is the ama……..if it is intended for the ama to be light and skim the water, why have a V or rounded bottom here?
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Rob Zabukovec
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Re: Getting out on the water this year

Post by Rob Zabukovec » 03 Feb 2015, 20:57

old school wrote: Also, the best candidate for a single chine flat bottom, is the ama……..if it is intended for the ama to be light and skim the water, why have a V or rounded bottom here?
I am with you on that one.......
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