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Polarity
Senior Member
Registered: December 2001
Location: UK
Posts: 478
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wouldnt the prop be in a big turbulent patch.. ?
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yipster
Senior Member
Registered: October 2002
Location: netherlands
Posts: 2,344
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ah, thanks wise guy, help me think! propulsion as shown at http://boatdesign.net/forums/attachm...s=&postid=7192 is supposed to be very good.
but again you make sense, flow from a foil is turbulent indeed and not so easy to predict... how much is that, how different from a boats bottom etc. let me think... there have been airplanes with props behind the wings... when having the ventilation plate above the prop (or is it cavitation plate?) flush with the bottom of the pod... in the "whats the best software" department i was reading about this and i'll take a deeper dive there. anyway i'll hope to be trying it out soon!
keep trowing those darts! ;-)
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Tim Dunn
Junior Member
Registered: May 2003
Location: Arlington, WA, USA
Posts: 21
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Kool. If you haven't, you might want to deep v the bottom of the passenger pod, in case of pounding in waves and swells.
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Tim Dunn
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SailDesign
Senior Member
Registered: January 2003
Location: Jamestown, RI, USA
Posts: 1,608
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Yipster - is that a La-Z-Boy I see in the helmsman's cockpit? You my want to add a transom flap so you can recline the beast ;-)
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Tim Dunn
Junior Member
Registered: May 2003
Location: Arlington, WA, USA
Posts: 21
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On the other hand, the center of gravity is really high. How would that play out with rollers on the beam, and/or making a quick turn? Maybe you want some beam foreward, and two of those pods foreward. It would probably be safest to go back to the type of catamarran that I assume inspired it. Of course, you'd probably need to move the engine aft for good steering, but the prop would be in nice, undisturbed water.
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Tim Dunn
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yipster
Senior Member
Registered: October 2002
Location: netherlands
Posts: 2,344
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...
polarity, on second thought the top stream of a foil should be the fasted flow, still thinking here, best be propulsion from inside the stern pod(s)...
tim dunn, a deep v makes sence also but has sooner water contact. CG is high but wide standing legs give slow heeling and pitching strability in the "small waterplane area". propulsion up front has a more constant submergion on one OB or 2 canted outboards on the stern legs would be just GREAT but for now its only a poor mans prototype. in total it is more than a normal compromise but it should enable minimal wave resistance, thus economy and a comfortable high speed ride in waves (medium chop). boarding it you need the stick or a plank tho. see also http://boatdesign.net/forums/showthr...5&pagenumber=3 and http://boatdesign.net/forums/showthr...ighlight=swath to see what inspired me, after reading about high displacement torpedo speeds etc.
saildesign steve, didnt get "La-Z-Boy". mean i dont work hard enouch? you might be rite there! i should be in reinolds numbers etc rite?
 yipster
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SailDesign
Senior Member
Registered: January 2003
Location: Jamestown, RI, USA
Posts: 1,608
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Yipster - "La-Z-Boy" is an American lounge chair manufacturer. They are reclining chairs, hence the need for a transom flap.
I'm sorry - it is all too easy to forget that American culture does not permeate the world (thank Heavens!)
Steve
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Lew Morris
Industrial Designer
Registered: June 2001
Location: Pismo Beach, Ca
Posts: 122
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June-10-2003 12:03am
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Rating: 10
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mount a surface peircing foil ON the outboard lower unit (canards?) ... and a submerged foil aft.
get rid of the second seat (yeah, i know, it's more fun if you can take someone with you) ... and make it run on less than 15HP.
THE BEST PART... not a computer generated line ANYWHERE!
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yipster
Senior Member
Registered: October 2002
Location: netherlands
Posts: 2,344
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thanks guy's! getting the piping done now, all details (work too) is more than ya think but satisfying also.
yes, single seat start on 7.5 hp that needs a long tail, high pitch prop, autotrim ob support is in the cards and enough to start trying it out in 1 to 2 months i hope.
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Tim Dunn
Junior Member
Registered: May 2003
Location: Arlington, WA, USA
Posts: 21
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Warby shakes his head and says, "That guy in Seattle, Russ Wicks, wants to use a reverse three-pointer" - a boat that rides on one planing surface in the bow and two at the stern, like a tricycle - "but everyone who's tried one is dead. They have a slim aerodynamic shape and they work great in wind tunnels. But you can't scale water, and in reality they have balance problems. If you get on the front sponson, it'll turn you almost like a tricycle. I told Arfons he was going to die, and he did."
"Wicks says he's gonna make his reverse three-pointer stable by having a computer adjusting things. But one-thousandth of a second isn't fast enough on a moving surface with lots of hills and valleys. The computer is dealing with what's behind you, not what's in front. My boat has inverted airfoils and all sorts of trick stuff that I can't tell you about in case Wicks reads your article."
(Found in "Wired" magazine)
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Tim Dunn
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yipster
Senior Member
Registered: October 2002
Location: netherlands
Posts: 2,344
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yeah, those speed record hunters where my heros. the bike i'm building you cant compare and is different, its not skimming the surface bumping waves, more like flying below the surface i think -on a tricycle yes- not meant to go faster as 40 knt tops.
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lockhughes
ElectricGuy
Registered: June 2002
Location: Wards Island Toronto north shore, Lake Ontario
Posts: 109
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OK... so, two "legs" fwd. and one aft. Props on the bows of each leg?
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human-electric hybrid
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yipster
Senior Member
Registered: October 2002
Location: netherlands
Posts: 2,344
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"on the drawing board" to use an ancient expression :d
pictured one is under production tho, now aligning sleeves for frame and sizing engine mount couse that end plate best be level with the bottom of the frond pod, and that is only just possible with a still to get extra long tail, make the mount trimmable...
i'll try to sit on that floating small waterplane area triangle first :d
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Nomad
Mold Trader/Boat Builder
Registered: February 2002
Location: Perry, Florida
Posts: 450
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September-4-2003 4:51pm
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Rating: 9
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Nice work Yip!! I't would look more stream-lined if you could cut the legs down some. If not it looks good still. If you could work something out with the turblance having the Engine and steering forward, that would be pretty neat. Car like steering....
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ywainap
Junior Member
Registered: October 2002
Location: Southampton
Posts: 14
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September-17-2003 8:07am
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Rating: 8
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It's nice to see some hand drawings these days! .... Howver computer design gives you some prediction of stability. SWATHS are great for fixed loads, but at the same time, have you considered the change in performance when carrying two people as opposed to two? They also have an inherent problem with reserve stability to resist pitching and rolling motion; the main problem that I see occuring here is that due to the lack of reserve buoyancy in the bow, your outboard engine may get swamped.
The other inherent problem with SWATHS is that they are very sensitive to load changes. With minimum load [one person @80kg and a few litres of petrol] you'll want the submerged volume and the prop to sit well below the surface to avoid interaction. What happens when you fill up the tanks and add another 80kg of human? That means that being a SWATH [with what seems to be three tiny waterplane areas] you'll get quite a lot of sinkage. To combat this you could make the legs 'fatter', but then you adversly affect the performance. The other solution is to keep the same leg section but make them deeper, however this increases your wetted surface area and reduces your ability to operate in shallow areas.
Great Idea though. It would be nice to see some photos.
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Ywain
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