Check this out:http://www.boards.co.uk/articles/index.asp?ID_A=298&article_type=16
I think page 3 is a bit... random 
The article leads me to pose a quandry that I have always had. Slalom boards typically have little or no tail rocker, so straight tail / no tail rocker is fast, but you need to have low wetted area of the board to be as fast as possible. So why is straight fast, would'nt this mean that all of the straight section is wetted ? Or in reality, is only % of the board in the water wetted because the water surface is not perfectly flat ?
Trouble with rocker is it "sucks" you down it presents a curved surface to the water, this produces "lift" unfortunately in exactly the wrong direction. I had this demonstrated one day when I tried to tow a cray pot float to shore behind my sailboard. Expected it to just "skip" over the surface, but the faster I tried to go the deeper it sunk! couldn't get on the plane, so I ditched the thing.
You can probably get away with a subtle rocker in front of your minimum planing area
the straight section has an angle of attack. 2 deg for eg. so not all of it is in contact with the water.
quote:
Originally posted by greenleader
everone's making it up as they go along.
yep it's all made up.
early planing is all about the nose hey, that's why we see so many pin tail formula boards. agree a wide nose makes a massive difference but what about waterline length?
what about channels, concaves and how they change the pressures on the hull. how do you reduce the suction or pressure created in the channel of the hull or concaves etc.
what about steps, these change the way the water is effected at the tail.
or even air pipes like on the f2 boards.
quote:
Originally posted by Gestalt
what about channels, concaves and how they change the pressures on the hull. how do you reduce the suction or pressure created in the channel of the hull or concaves etc.
Then speed boards must also provide good control at maximum speed. So there are quite a few needs here 
quote:
Originally posted by decrepit
This is what's interesting me at the moment. Ground effect vehicles can fly because of air being compressed underneath them.
And here's one for Nebs, race cars use downforce generated by air flow underneath them. So you can have 2 opposite effects.
I guess controlled by if the air is compressed or whatever it's opposite is, (sorry getting old, help welcomed)
quote:
Looking at Gestalt's board's bottom shape, the channel at the front is flared, guess that's to funnel air in and increase pressure, good to get you planning earlier, but does it increase aerodynamic drag at top speed?
What he means by this statement
The main down force generated by a proper racing car is done by the diffuser underneath the rear wheels. All the fancy wings and splitters you see on the outside just tune this diffuser so that it sucks the rear tyres harder to the road
is that by fitting skirts, the air pressure on top of the car is greater than below inside the skirts, thus down force to help it stay on the black stuff, particularly when breaking and steering through corners.
With a board, and channels along the underside, the attempt is to allow more air into this space, like an air cushion or a hovercraft scenario. So instead of the board riding its own bow wave, its enhanced by additional air cushion and planes easier. However too much squishy stuff in there, and a whole lot of other problems surface. The target is to get just the right amount by design, and design has to take into account the variation in water profiles the board will be subjected too while it skims the surface.
Anything you do with air to your hull, be it lift or downforce is work that shouldn't have to be done and is therefore drag. The biggest virtue of short noses (imho) is less windage.
nice one mineral. couldn't have said it better myself.
the boards are built with both conventional bottom and the one that causes debate. i prefer the one that causes debate and so all my boards are built as such. i order them that way from nxs
the idea with the channel step was to reduce wetted surface area. well that's why nxs/manta started the concept how ever many years ago when pete was designing speed boards. i also found they had other advantages too when i rode them
obviously when sailing in rough water more than just the flats are in the water so the wetted surface argument is nill at that point. BUT down the middle of the board is a deep v or double concaves of sorts. these really lock the thing inline and smooth out the ride. (same thing as concaves on other boards)
also having the channels keeps the board on the plane longer and also gives excellent bite when tracking to windward.
hmm, now some problems. (which were resolved through R&D)
drag can be caused be the channel entry hitting the swells in front. careful attention was given to that.
another is the drag inside the channel. gotta let all that air and stuff escape whithout backing up.
channels add drag when dredging. also the step seems to reduce early planing. this has been the case when compared to the flat bottom versions as said previously. normally i needed 1-2 extra pumps to get planning but find the extra top end speed, stability and gliding during lulls is worth it. all of these things are resultant from channel depth. to shallow and it sucks to the water basically. NXS tried different depths along the way.
the water profile is another big consideration. the slalom speed board in the photo www.seabreeze.com.au/gallery/gallery.asp?imageid=4583 is built for flat water and speed in marginal wind conditions. so it has very little rocker. that's gong to be fun in the swells. other versions have had more nose kick so swells weren't a prob. then when you do hit the flat stuff the board excellerates on the flats and that's where the reduced wetted surface comes in to play.
the other board, the speed proto with the same bottom concept is a test board. shaped from an old blank and only glass finished. it's back in the factory having some tweaks from the last session added. then it will be reglassed and back on the water. it's short and wide too but speed board wide not slalom wide. www.seabreeze.com.au/gallery/gallery.asp?imageid=4643
it is very thick so it is more suited for my fat @#$# and QLD conditions.
as i said before, the hull type suits the short wide modern plan shape. the older 90's version i once had was a normal shape 270 long 65cm wide slalom board etc. the length and channel combined made it lift off and which reduced the wind range. but a shorter swing length removes this problem all together. i also find that the steps at the tail give amazing grip and carve arc potential for a wide tail boards when turning.
i was doing some research online and stumbled across this link
here is what drake said about the hyper... www.windsurfingmag.com
quote:
Originally posted by Gestalt
nice one mineral. couldn't have said it better myself.
Then introduce stealth and treachery and steal the latest developments from all your hard work
