Dave Goode broke his leg this weekend

[eleeski]

I filled my buoys with water to assist with the fluctuation in my water levels. I use about 1m of bungee. With a full air buoy and a full lake the bungee would be under very high tension. As the lake lowered, the buoy would float higher (presenting a threat to my ankles). With the water filled buoys, less bungee tension is needed so the bungees did not get overstretched. As the water dropped (over 1ft) there was still tension on the bungee so the buoys stayed accurately placed. My course looked the best it has ever looked, ball wise. The floppy boat guides were another story...

Eric

[eleeski]

A few years ago I tested some "safety buoys" on my course. They worked quite well for skiing (over!) and had excellent visibility. They didn't last too long (5 months) but we all loved them. They were (probably) legal - at least they were the huge tall style. The rule change to smaller lower buoys reduced the risk to an acceptable level (maybe not for Dave) so I dropped the project. Maybe I'll make a new one and send it to Dave.

 

We also tried a spiky buoy. We used noodles shredded into 1in tubes and tied together at the base. These looked different but worked OK. But we didn't run them for long in the lake - I'm not sure why. These would need a rules change/interpretation. There are other options for buoys.

Eric

[aguylikeshark]

last year i worked on two concept bouys.

1. the bouy is a half moon shaped so there is min water displacement - onl;y the regulation profile/volume is exposed. it's the displaced water that is the biggest component in upsetting the ski.

2. a soft form that fits around existing bouys so there is no need to buy new, and courses can be retro-fit.

3. A new non-inflatable bouy made from the ultralon foam, the same foam used in our (intuition) liners. coated like a crock shoe - very durable, never sink.

I got stuck on #2 and the cost/benefit for #3 there was no budget to do this. 

 

[Thomas Wayne]

...

[Milford]

TW,

 

I would be interested in your thoughts about a "half moon" buoy and why it would not work. Any additional info would be much appreciated.

 

Thanks,

 

Jeff

[MAD11]

Milford,

I saw a great photo of you at nationals and it didn't look like you had any trouble with the current buoys. Have you seen that shot? Kelvin Kelm took it I think. Not even sure how you kept skiing.

Marc

[Milford]

Marc,

 Yeah, I saw the photo.  Very cool shot.  I remember hitting the buoy, but luckily my boots must have made it to the outside, otherwise I would have been swimming.  I have hit many buoys skiing and think that it is only a matter of time before something bad happens.  I hit the 2 ball at 39, 4 days before the Diablo Shores Pro Am and didn't know if I would be able to ski.  Tweaked my ankle pretty good, when the ski jumped off of the buoy and reconnected with the water.  I know several people that are out with broken ankles, torn tendons, etc, so this is something that needs to be addressed.  A redesign of the buoy is in order.  Until it happens, I do think filling the buoys with some water is a good idea.

 

Jeff

[MAD11]

 Couldn't agree more on the buoys. Hate to see anyone get hurt.

[boarditup]

Hemispherical buoys -

 They have an edge.  You can displace against the edge.  You can get tangled in the line below (I have seen a fin with a metal hook through a hole) - nasty OTF fall, but luckily, no injury.  You also can have the ski essentially stop if it hits it at the right angle.  You need the bottom skirt to prevent this from happening.  A ball shape is much better.

Finally, you need tension to keep the buoy in the right place.  Take away too much of the bottom, you have a moving buoy.  Having enough tension, you have a lot of the hemisphere underwater.  You are back where we started....

 This winter I'll work with a spiny buoy.  Maybe I can find a plastic or rubber compound that will not support algae...

[Bulldog]

Why are the balls so wide?  Could there not be a balance between the size accross and the ability to see it?  Tennis ball size or maybe a softball size. A smaller bouy would be harder to hit and would have less of an impact if it was hit.  Just a question that I always wondered. 

[Thomas Wayne]

...

[HO 410]

That makes sense.

For some reason, when I was reading "Half moon" I was envisioning the bell of a mushroom, Must have been thinking crescent moon.

 

 

 

TW,

Have you give any thought to using a perforated, plastic shell (think a whiffle ball the size of a turn buoy).

It would look, kind of like a mushroom [go figure]. It would be low mass, would not require much flotation to

keep it on the surface or return it once being submerged, and the holes should allow it to move through the

water without causing too much drag.

[Bulldog]

What about the material that "Crocs" are made of?  Does it float or could a small interior inflatable bladder hold it up??

[Thomas Wayne]

...

[DW]

If you look at aerodynamic drag coefficients, these are for air but the relative comparison is still valid if we ignore the compressability factor of air, which for this exercise is probably valid as it would actually help the sphere numbers.

Cd for a sphere = .47, for a flat plate = 2.0 so that is the big reason the flat bottom buoy would make the problem much worse.  The force = Cd*A so the shape and area or volume are the key factors in required force to move the object.  You then have to add the buoyancy factor on top of that, which is also significant and that is where the half filled buoy offers it's advantage.

If you look at the Cd for a blimp or streamlined shape, it goes down to .02-.05.  Not directly transferrable because the buoy would never be moved exactly along the long axis and once offset it shape becomes much more like a sphere, but could generate some provocative thoughts on ideas for buoys.

[Marco]

Would a cone shaped buoy with a rounded top (picture an ice cream cone with a single scoop)  offset the problems with resistance to submersion that TW/DW point out, and still offer less resitance to lateral movement?

On a related note, a friend of mine center punched 2 ball at 38 a few days ago, tearing all the ligaments in his ankle, (requiring surgery I believe).  Oddly enough, 2 at 38 is also what broke Dave Goodes ankle, and ruptured my achilles this fall.