...the Hobie TriFoiler can pull 2+ g's in turns. An exotic car can barely manage 1 g on the skidpad. This claim can't be true, can it?
http://en.wikipedia.org/wiki/Hobie_cat

In theory, I see no reason why not...a car can only turn at 1 G since that's all that is holding it to the pavement, assuming we ignore aerodynamic effects which are not excessive in a typical street car.

I believe the trifoiler has some amount of vertical fin in the water...which will oppose huge amounts of side slipping forces in a turn.

That said, Formula One race cars can turn at greater than 1 G...in fact they typically hit close to 4 G's in turns & breaking. This is entirely due to the highly efficient aerodynamics on this cars. There have also been publicity stunts in tunnels where an F1 car at speed goes up a ramp and corkscrews until it is driving upsidedown on the ceiling of the tunnel....thus there is more than 1G of "downforce" acting on the car to hold it to the ceiling.

Driving upside down.. Wow! Any youtube links to that? Sounds like a cartoon stunt <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

There was a track here in the US that they were going to run F1 on. They had to change the track, drivers were blacking out in one of the corners.

I've driven my MG on the Formula One track at the Indianapolis Motor Speedway, as part of "Indy British Motor Days". They lined us up and told us to keep the speeds to less than 30 MPH, but everyone was giving lots of room between cars so you could floor it and get more speed. I probably got to 80 on the main straight-away, before the track dives into the infield in the series of hairpin turns. Through those flat turns, I could not keep the car from fish-tailing at anything above about 20. I got a real appreciation of the downforce it takes to hold the F1 cars on the track at higher speeds.

For the banked turns, Indy is considered a low-banked track, but you can really feel yourself being pulled down into your seat, even at low speeds with no aerodynamics. So the G-forces at 230 must be incredible.

As for a Tri-foiler, since it can't fish-tail as it turns, I can see it easily generating lots of G-forces, till it flips or something breaks.

If you ever saw Greg Ketterman chucking the Trifoiler about on flat water you may believe - mad bit of kit when it is set up right.

One thing that amazes me...F1 drivers have some of the strongest necks on the planet. The helmets that they wear must be about 10-20 lbs....now apply 2-4 G's several times around a track and make 70 or 80 laps in 2 hours...you'd better have good neck strength!

G force in cars is limited by the maximum lateral friction the tires can generate (plus whatever you get from banked curves).

G force in boats is limited by the maximum lateral lift the foils can generate, much like in planes.

The claim is very probably correct.

I don't actually know what their helmets weigh, but I'd be willing to bet it isn't over 5 lbs. A good Arai motorcycle helmet weighs about 3 1/2 pounds. But you wouldn't have a microphone, drink tube, etc in a full face motorcycle helmet.

And there's not much -head room- in an F1 race car, ie. they don't have to hold them against the G's all day, the helmet has nowhere to go, sideways, because there is a roll cage tube right there. This is for crash protection, so their heads don't snap off when they hit a wall at 200mph.

THat's true, but most of the helmet is not supported above a certain point by the **** sides...about the jaw or cheek line. The driver also needs to turn his head during the turns (checking mirrors, looking around the corner etc).
Finally, it's during the braking where they have to keep the head up against the forward pull during the incredible deccelaration (also close to 4 G's initially...drive has to modulate the brake as the downforce & airspeed drops during braking...otherwise they skid off the track).

Im really glad I dont have to worry about all that when i sail. Most of the time when I'm slowing down its because i just pitchpoled. Maybe I should wear a helmet for that.

Some auto racing there is a tether that limits the forward motion of the helmet for preventing whip lash. I wonder if F1 does that as well. It seems like they jump out of the cars fairly quickly when something goes wrong though.

I remember the first time I sailed a Rave, as I felt it picking up speed I was thinking to myself "this is the first boat I ever wanted a helmet on", then after going farther underwater than ever before on a boat (it was getting dark over head) I thought "and maybe one of those padded restraints like a roller coaster"

F1 drivers must wear a Hans-device...kind of a shoulder-mounted harness out of light weight carbon...to control head from going forward beyond a certain point. This is for crash injury prevention, not for comfort. Most drivers hated it when it was introduced cuz of the restricted movement it created...now it's a normal thing for them.