Patsy
I’ve been busy getting sailing days in on my outrigger, including some real wind for the first time. Hats off to you, Mr Dierking, that is one nice sailing little boat!
In my sketchbook, I’m thinking about Birdwatchers. There’s something about the big boost in stability on its side that reminds me of proas…with pods or safety amas. But the thing I really love is sitting inside a sheltered space when you drive. For a microcruiser, getting out of the elements when you want to is the greatest luxury. I’ve drawn a sit inside 22’ trimaran and an 18’ scow-bow-birdwatcher/Scram Pram-esque mono. I love that the scow bows are kicking ass in the Mini 6.5 class. Old dogs can learn new tricks.
And now back to proas. I threw out some sacred cows to get a fresh start. The biggest was that you have to be able to drive sitting windward of the vaka. This is a toughie. Sitting a bit to windward add lots of adjustable rigting moment. And in a sit inside, that opens up the windward side of the cabin—adding complication, reducing structural integrity, and letting more water in. But letting go of that constraint opened up a floodgate of consequences.
Simplicity is the biggest. This boat is just a dory with the topsides stretched up into the cabin sides. Three boards, a deck and a pod.
And its a kooky pod. The headline is that white facets on the bottom of the pod are angled 20 degrees up from the water’s surface. So when the boat is heeled 15 degrees, the tip of that facet touches the water. 20 degrees is the AoA of a perfect skipping stone, and that’s their purpose; dynamic lift. These are the result of some conversations with Dave Culp about pod curvature and coanda effect.
https://www.youtube.com/watch?v=AvLwqRCbGKY
Dave’s point was that the coanda effect should cause dynamic suck, not lift. I made a little pod and ran it under the faucet, and sure enough, it acted just like the spoon in the video above. I don’ t know what’s happening on a pod skimming the surface, in real conditions. How strong are the dynamic effects compared to hydrostatic forces? But, as a thought experiment I set out to figure out how to make a planing surface on a pod, and this geodesic/stealth looking thing is the result. In any case, it looks kind of bitchin.
This concept is called Patsy because its inspired by Newick’s Pats. Like Pats, Patsy has a schooner rig with roller reefing and no booms, but in this case using off the shelf Hobie Bravo rigs. The Bravo has a bigger distance between the bearings on the mast, higher aspect and a shorter sheeting base than the Adventure Tandem. Like Pats, you live in the hull, pretty much. Celebrating the long, narrow space in the center results an a cabin 52” max headroom, with the sliding hatch closed, nine feet long. The floor is just 19 inches wide, but it flares out to 43 inches at the top of the coachroof. This in a 24’ boat with a 12:1 L:B. Headroom with the hatch open is infinite. The hatch, which slides to leeward, has a 24” plexi dome, for 360 degree views when steering inside in bad weather.
Steering ONLY from inside simplifies a lot of systems. And, for a schooner proa, things are already simple. Two booms, outhauls, boomvangs, halyards, sail tracks, lazy jacks and several reefing lines are already left out. And the ability to instantly reduce sail, is pretty damned cool. As is micro adjustable sail area fore and aft. There are some sail shape compromises with boomless sails. But for a Raid/Microcruiser,this is pretty racy. Oh, and lots of development work has already been done ion these rigs. The question is are they stiff enough for this bigger boat.
The ama is a blatant rip off of Skip’‘s Nomad/Broomstick; a keel without a boat on top of it. There are 16” of draft at 300lbs. Full immersion is close to 1000lbs. Vaka draft is 10” at 1200lbs. Skip’s keel feels like it belongs on this simple boat. I even think it looks kinda cool. I’ll be drawing a plywood banana ama with a daggerboard too…but this just feels so simple.
Steering is by dagger-rudders. The pushrods go right into the pilot seats in the cabin, with vinyl boots to keep water from coming in the front. The total draft, dagger rudders down, is 34” at full displacement. In really thin water (down to 16”—the ama draft) we should be able to sail with both boards up, steering with the sails on most courses.
Anyway, this is my latest microcruiser. Its not as elemental as Kensho. But its going to keep me in better shape on a cruise or a raid.
okay…its only taking one pic at a time…
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last one for now…
The ama is a blatant rip off of Skip’‘s Nomad/Broomstick;
Imitation is the sincerest form of flattery 😉
Skip
.....How strong are the dynamic effects compared to hydrostatic forces? But, as a thought experiment I set out to figure out how to make a planing surface on a pod…..
Another example of the Coanda effect:
http://chevaliertaglang.blogspot.com.au/2013_11_03_archive.html
Magic Carpet or Magic Submarine?
Chris, you might also enjoy the scow a bit further down the blog.
Rob
Rob-loved the scow, but missed the coanda effect reference? Right link?
Skip—indeed it is. In fact P52’s ama has already inspired a marshallese vaka shaped ama. Any thoughts on the difference between the ama with a keel, vs the floating keel as ama?
Rob-loved the scow, but missed the coanda effect reference? Right link?
Sorry,it was my indirect cheap swipe at those who think that leepods and flares to leeward will get sucked into the water, not dynamically lifted.,,,,,,Magic Carpet by Reichel Pugh heavily flares out above the waterline specifically for dynamic lift and stability, as do a lot of box rule boats as explained in that link.
There may very well be a Coanda effect on a flared hul or podl, but dynamic lift has to be much greater….otherwise there would be a lot of submarines rather than yachts out there….
Did you know that the latest Pogos (biggest French builder of mini transats) now have bow spray rails fitted for the same purpose?
Rob
Skip—indeed it is. In fact P52’s ama has already inspired a marshallese vaka shaped ama. Any thoughts on the difference between the ama with a keel, vs the floating keel as ama?
Am tempted to fall back on its a “distinction with out a difference”..... But in reality you would have to compare the two approaches with some hard numbers, buoyancy, wetted surface, draft, L/D ratio, waterplane loading, and the like. Might be easier, and more fun, to just build both and try them.
Should be fairly obvious that I think there is a LOT to like in Patsy, 3 sheet dory hull, schooner rig, buoyant foil float, general simplicity.
Should also be fairly obvious that I’m not in the leepod camp, having not ever built one or carried the concept beyond a very preliminary sketch. Part of this is I’ve tried diligently to avoid water that’s cold enough to kill me, balance is I lean towards the very conservative side of proadom preferring cruising to racing (quick cruising to be sure but I don’t have the competitive drive of the racer’s I’ve designed boats for).
Still I like Patsy’s pod in the sense that the faceted shape is really slick (old gearhead term was “Trick”). OTOH a couple of ‘steps’ or discontinuities in a more conventional pod might eliminate the Coanada effect.
Always glad to see a new design posted.
Skip
Part of this is I’ve tried diligently to avoid water that’s cold enough to kill me
Hi Skip,
You were at Weymouth in 1986-7 were you not? I have a bit of video of the boat—and you—at that event. If I can isolate it—it’s only 20 seconds or so, would you like a copy? 😊
Dave
Part of this is I’ve tried diligently to avoid water that’s cold enough to kill me
Hi Skip,
You were at Weymouth in 1986-7 were you not? I have a bit of video of the boat—and you—at that event. If I can isolate it—it’s only 20 seconds or so, would you like a copy? 😊
Dave
Different Skip, never been to England, 1986-7 was firmly entrenched in Texas designing racing canoes as a hobby.
Thanks for the thought.
Skip