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Old Sep 20, 2009, 03:52 AM
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Paul.S's Avatar
Aachen, very western Germany
Joined Sep 2007
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Psk

Hello every body,

i would like to introduce my sailboat "PSK". I already documented on a german forum. But because of interests from one out of Brazil I like to try it ones more in english, so I can link every non german speakin person to this forum

This was my first attemt buildig a boat. Normaly I move on rcgroups in the aeroplane area. The idea to this boat came up, after I watched many month to the german "mini40" mulithulls and they started to discuss if there can be a advantage with foils in a race.

I found three old fuselages from a flying wing on the top of my cupboard, and i decided to give it a try for. So I bought some carbon tubes (not pultrusion made, fibers are +-45°) and made the foils. Main target was the weight! Because the fuselages are so small, I fear that the lift could be to small.

Frontfoils are made round a paint bucket out of carbon and foam. I would like to have this round circle, not just a straight v-form. I read that others had problems, that their foilers came with high speed to high out of the water and flipped over. So with this circle the lift should decrease very fast with more altitude. The t-tail in the back is balsa and glas.

So the PSK is 1,2m wide, about 1,2m long and about 1,3-1,4 high. Weight is just 340 g (without the bottle you can see on the video )

RC: (15 g Servo for the fin. A DS3328 for the sail.)

So... video and pictures:
PSK Foiler RC (1 min 52 sec)
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Last edited by Paul.S; Sep 20, 2009 at 04:05 AM.
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Old Sep 20, 2009, 04:23 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Very Very Nice, I'm impressed
Nick
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Old Sep 20, 2009, 08:50 AM
Registered User
Dolores, Colorado
Joined Dec 2007
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Paul,
wie kalt, 0,5 cm

very, very nice built, that thing is fast, aceleration is amazing.
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Old Sep 20, 2009, 09:04 AM
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Bozeman, Montana, United States
Joined Aug 2003
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Ditto Nick's comments, well done!
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Old Sep 20, 2009, 10:37 AM
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Middletown, CT
Joined Dec 2003
272 Posts
Do the foils actually have a foil shape or are the just simple single surfaces? Are they set with an angle of incidence and if so, how much? Lastly, where is the center of gravity? Nice job by the way!
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Old Sep 20, 2009, 11:53 AM
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Aachen, very western Germany
Joined Sep 2007
220 Posts
Thanks for compliments! I think it was a good portion luck with me, the boat is running that well. I didīt expect that this design run so efficient.

@Schrott: Ja, sehr kalt. Irgend was in der Groessenordnung muss es gewesen sein I had to swim about 4 times. Before the bottle was put at the nose, it flipped sometimes over it.

I think there is more potential in the design of the foils (profil) and much more in the sail. As you can see at the fast part, the sail has much distortion. Maybe this winter Iīll try and upgrade it.

Frontfoils have a thin (about 5%) hand shaped profil with flat bottom (the paint bucket). The t-tail has no incidence in order to the fuse. Profil hand shaped, symmetric and thin. The front foils certainly have an incidence of about 5-8°. Otherwise it wouldnīt lift off. Center of gravity is about 10 cm behind the main beam.

Cheers,
Paul
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Old Sep 22, 2009, 04:17 AM
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Aachen, very western Germany
Joined Sep 2007
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Hello,

so if enyone ist interested in rebuild something like this, I like to show some profils which should be quit perfect for the task.

The thing is, that according the estimated speed the foils doing in the water, they had to be quit thin. In my opinion that is important to the performance. I havenīt done the job well at my front foils .So if you try to shape such foils, and you have no idea wich way to go, here is an example.

Paul
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Old Sep 23, 2009, 03:18 AM
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Aachen, very western Germany
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How I made the front foils:

I done it around this paint bucket you see on the picture. One layer 200 gram/sqm, some shaped "Depron" and one more layer carbon. Than lots of clingfilm around the whole bucket. But I have to say, that it tooks me lots of time finishing the foil. The surface on the uperside needed to grind, resin, grind resin... till it was half-decent. Aditional the profil with its flat bottom has on some points fare to much camber, so presumable the drag rises painfull with highspeed. So do it better and the topspeed should increase.

Paul
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Old Sep 23, 2009, 03:45 AM
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Aachen, very western Germany
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The tailfoil.

I took some balsa and shaped this symetric shape on it. Than put the layers glas on it and ones more clingfilm. This sandwich between two plates "depron" and two massive woodplates. Than big c-clamps and all the torque my hands can give...(the Depron get pressed and squeeze the waste resin out) Not much to finish at this ones. The entire t-tail has 14 g and is quite strong. Actually it much more proper and lighter than the my carbon-Depron-foils.

Paul
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Old Sep 23, 2009, 10:21 PM
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Dolores, Colorado
Joined Dec 2007
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Paul,
this one is for, look at the very last picture, thats a rocket machine, 50 knots.

http://www.faz.net/s/Rub9AE899D74FA6...~Scontent.html
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Old Sep 24, 2009, 06:30 PM
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Aachen, very western Germany
Joined Sep 2007
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Schrott,
thanks for the article! Very nice (in german )
Well of course I know the Hydroptere. And it is certainly the big brother of my one.

For very high speeds, I am quit sure foils on a boat are a very good solution. The real question is: Is it possible outperforming a conventionel cat or trimaran in a race with a foiler like Hydroptere? Alinghi and BMW-Oracle have choosen to conventionel.

The target from the "PsK" is, to be faster in a whole race (average speed). Donīt know if its achieved. Maybe next year I will join a race.

The really cool thing is, that there are so many different designs today. Maybe it is comparible with aviation 80-100 years ago. Today all high performace aeroplanes looking quit similar... But this boats donīt.

Paul
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Old Sep 24, 2009, 09:01 PM
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Dolores, Colorado
Joined Dec 2007
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Paul you are very welcome,

By the way you aroused my engineering curiosity and since winter is coming rather fast into South West Colorado and after I have done a few truck loads of fire wood and brought in a 100 tons of hay I will sit down and get my thoughts together.
One thing I will explore if the foils conect in a parabolica between the front floats, would that help with stability.

The foils on the racer are angled inwards, towards the center hull, are they curved like yours.
Or are they like wings, straight, and pointed in an angle towards the center hull.

Your foils are are lifting body only, but than after lift, they do not provide a stabil float, its a dragster.
How to built, design a stabil platform.
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Old Sep 25, 2009, 12:47 PM
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Aachen, very western Germany
Joined Sep 2007
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Schrott, nice to hear that your engineering curiosity is inspired.

But concerning your idea of large parabolica front foils: The main job of the foils is reduceing the contact surface to the water. The water produces about 800 times the drag than air. But its just a hint. Iīm looking forward when you came up with your one hydrofoil.
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Old Sep 25, 2009, 01:39 PM
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Middletown, CT
Joined Dec 2003
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Quote:
Originally Posted by Paul.S
Hello,

so if enyone ist interested in rebuild something like this, I like to show some profils which should be quit perfect for the task.

The thing is, that according the estimated speed the foils doing in the water, they had to be quit thin. In my opinion that is important to the performance. I havenīt done the job well at my front foils .So if you try to shape such foils, and you have no idea wich way to go, here is an example.

Paul
I don't get the rudder foil. Shouldn't be turned over to provide positive lift? I somewhat get the front foils but it seems that the lifting part of the foil stops at the radius of the bend and the vertical part of the foil doesn't generate lift at all.

A foil acts just like a wing in the water right? It needs a lifting surface by either a foil cross section or a slight positive angle of attack to generate lift. Am I missing something?
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Old Sep 25, 2009, 01:54 PM
Michael Edwards
Raleigh, NC
Joined Aug 2006
51 Posts
The rudder foil is designed to keep the boat from pitch poling (going nose down).

ME.

EC-12 1969
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