Well....
While building my seat some questions pop up.
As with every kind of wing, curves generate faster airflow and as such, less pressure at the curved part.
I see many seats with veeeeery nice curves (aus230, I love yours! 
), but I wonder how these curves influence speed and downforce.
2 specific (closely related?) things I have in mind:
1. At 70kph, the curved seat could/would create under-pressure between ground & seat that it might pull the seat down, with extra load on rear axes?
If you 're chasing the wind in soft sand, wouldn't it pull you deeper into the sand, increasing drag on the wheels and reducing speed?
Do we want it? Is there a benefit in doing this?
2. As with any kind of surfing (I used to build boards), release of fluids (like air) is quite important. The rear part of many boards are built specifically to allow the water to release easily. If it's not, your board is sucked into the water and slowed down until the water manages to get of.
Reflecting this onto seat-form, it appears that few seats take this into account, letting the airflow just following the whole entire shape until ...
Imagine a sailboat having a rear end just like the front, the aft would get sucked down and speed would be totally fubar.
Look at the Iron Duck
And GreenBird
and its predecessors...
They all have a rear which allows easy air-release.
Why not look for an option to try this in Cl5?
I get what you mean but with a seat restriction length of 2.5m there is no way to taper the rear of the seat.(that I know of)
Cheers
aus230
I am fairly sure that the rules state you are not alowed to have any part of the seat as a wing shape in Class5. I may be wrong though
Mmm... okay... maybe 2.50 is quite restrictive...
Buuuut.... what are the consequences of these shapes?
Btw, how long are your seats?
And what's the definition of "seat"?
* Anything called hull?
* Distance mast<->end of seat?
* ...
As I'm 1.87 tall, I hardly need a complete hull bigger that 1.90m.
That would leave me with about 60cm to add taper, even below the back seems like an option?
I'm not sure that I can get it all inside the box, but it's just a thougth...
I remember reading a paper that at the back of a race car if the angle exceeds 9 degrees than it might as well be flat. And I know that with the new wings on the 737 the air is so tight to the wing surface that the ailerons wouldn't work properly. That is why they have the little vortex generators mounted on the top. I can see where the shape of the seat could change the up or down forces, even side to side. But I am at a loss as to how you would change it while sailing short of changing the seat. As for the airodinamics, would you consider a lap robe?? Just something that would smooth the air flow over your legs. Just a thought.............Terry
Bonjour,
please read Manfred Curry book written around 1930 in Germany.
"the aerodynamics of sails and racing tactics"
Manfred Curry wrote a pioneering book on yacht aerodynamics and racing tactics, he studied sailing-boat design scientifically, testing numerous rig configurations in the wind-tunnel at Göttingen. The importance of his book within yachting has been described as having brought scientific sailboat design into the public eye/ He describes several of his inventions or developments that are in widespread use today, including the fully battened mainsail, the Genoa jib (so called because first used competitively in a regatta at Genoa) and the cam cleat (Called the "Curryklemme" in German).
he worked from the theoretical to the real,
by measuring how wind flowed over sails and accurately describing the
patterns. A breakthrough discovery made by Curry was that "the suction
effect in the lee of the sail amounts to three to four times the
positive pressure on its windward surface."
He also worked on bicycles aerodynamics being the only one to focus on low speeds
(planes, racing cars are too speedy for us)
Mmmm... sounds interesting...
But, related to the subject, what conclusion may we make?
How much would it affect speed?
Would it be useful on a yacht built for soft sand to eliminate higher pressure on the wheels?
What do you experts think?
After the first Mini championship last week we must admit that a fast yacht is:
a pilot,
a sail.
All kind of chassis,some with pod some with very soft axle,some just
all rusted,and almost no differences at the end.
Of course circuit was small and windy enough.
and if you sail miles and miles on the salt, you'll need better aerodynamic.
I should have remembered your yacht Clem.
, Do you find any benefit in the body taper.
Cheers
Vic
Benefit? Yes definitely. I can stash a half doz tinnies in there for drinks at half time. Also gives me some well needed down force.
Here is a pic of a Faze5 and the seat back in the 80's note the tapered end to the seat and the main sheet traveler system.
One of Bill Finch's yachts.
Greetings all,
As a newbie I intended to start my posts describing a build. However, I didn't want to begin until I had most of the parts so as satisfy the impatient
.
Having read through the volumes of posts (yes I now the mast tube is 10 degrees), and considered the same question you asked, I think a partial answer may be in recognizing the effective (aka: "apparent") wind direction is something like 12-15 degrees (from memory) off axis. That is, traveling at optimum speed and accounting for the static wind direction, it hits the body at an apparent 15 degrees off center. This may be why the usual impulse to put a tapered end (to address base drag) is not as warranted as one might observe in say, a hypermilage low drag car body.
How about a canard?? A horizontal wing that could be adjusted up and down to apply or remove weight from the front wheel.
en.wikipedia.org/wiki/Category:Canard_aircraft
Some class rules prohibit aero dynamic fairings.... others don't.http://www.fisly.org/scripts/index.php?loc=rules&it=2
Keep in mind that the use of canards / wings will create either an upward or downward force depending on how they are set up.
So with that in mind upward / downward force = drag = lower overall speed = why?
Where and how is the force generated to make the yacht go in the first place... and you want to waste any of that?
Normally its at slower speeds that you want more downward force, on the rear axles to stop the yacht tipping or on the front wheel to assist in steering. Wings etc don't give that. Yachts tip over at slow speeds not high speeds.
A balanced yacht with good alignment of CG, CR, CE is a much better way to go rather than correcting poor design.
Now before you go down the serious Aero path you do intend to wear lycra suits and streamline helmets while your sailing.......? Just like cycling, ski sports etc.
