Tom

You mentioned, "Mast flutter can be prevented by
mass-balancing the mast so the center of gravity is on or ahead of the
pivot axis, but almost nobody does this for masts although it's pretty
commonly done for rigid wing rigs."

What method is used to mass-balance a rigid wing?

Thanks
Jerry



--- In wingboats@yahoogroups.com, Tom Speer <me@...> wrote:
>
>
> On Jul 6, 2009, at 11:22 AM, Jerry Frost wrote:
>
> > I've been poking around some big boat websites and have noticed
> > there is little to no information regarding the potential hazards
> > and risks involved in moving across a dry lake bed at speeds in
> > excess of 80 mph with your butt hanging less than a foot off the
> > ground while being blown by high winds in limited visiblity. Heck,
> > that sounds like fun to me, but are there any reports of accidents
> > and their potential causes?
>
> Collision is the main hazard. I know of one landsailor fatality when
> a motorcycle ran into him. If I recall the story correctly, the
> motorcycle rider was looking backward at the time to see if people on
> shore were watching him.
>
> I saw Charlie O'Leary break an axle on Speed Squared when he hit a
> post on Ivanpah. He was doing around 60 mph, and the yacht slid
> sideways on its side. The friction wanted to make the body roll, but
> the weight of the rig - supported by the stay to the good axle
> sticking straight in the air - wouldn't let it. The mast acted like a
> drogue to keep the yacht sliding belly first. Charlie was cocooned
> inside the body and wasn't hurt.
>
> If you search around the internet, you can probably find a video of
> Bill Dale's crash when his mast fluttered. The wind was too high for
> racing, so a couple of yachts went out under mast alone to try to set
> a speed record. The cable controlling his mast rotation broke, and
> the mast fluttered, causing very high drag. The yacht pitchpoled
> backward, then leapt into the air and pitched down. The body buckled
> when the front wheel hit, and the hub was ripped out of one of the
> rear wheels (Indy car racing slicks). He was wearing seat belt and
> shoulder harness, and was unhurt. (Mast flutter can be prevented by
> mass-balancing the mast so the center of gravity is on or ahead of the
> pivot axis, but almost nobody does this for masts although it's pretty
> commonly done for rigid wing rigs.)
>
> I saw the result of a Manta that sailed into a barbed wire fence. The
> yacht was pretty cut up, but the pilot was not seriously hurt because
> the V-bar on the Manta protected the pilot.
>
> You need to make sure the body of your yacht has an adequate roll bar
> that will keep your head off the desert if you break an axle and the
> yacht rolls because the stays are now slack.
>
> I think the main things are to be able to see adequately, especially
> to leeward because that's where the other guy will be coming at you
> when going upwind. Look to windward because that where the other guy
> will be coming at you when going downwind. Make sure you have a good
> restraint system and wear a decent helmet - bike helmets are good for
> bike speeds, not big boat speeds. Make sure the roll bar will
> actually keep the yacht off of you. Watch out for mast flutter when
> tacking (keep sheet tension on to restrain the mast). Keep enough
> weight on the front wheel that you can control the yacht.
>
> Cheers,
>
> Tom Speer
>