board damage from jumping in harness

board damage from jumping in harness

Post by finta » Mon, 31 Jul 2000 04:00:00


Does jumping and landing hooked in put more or less stress on your
board?  I know it probably depends on a bunch of stuff.  I'd think for
nose first landings it's probably worse because in the worst case
scenario where your weight is too far forward you could end up putting
a large point load through the mast foot.  For tail first landings I'd
imagine there could be less stress because the harness is spreading
the loads between your feet and the mast foot.

Any other opinions?

Fintan.

 
 
 

board damage from jumping in harness

Post by Mike » Mon, 31 Jul 2000 04:00:00

Your analysis sounds fine to me. But why not just switch to a Chinook
Hydroshok and stop worrying about it? The more we spread the load betwen
feet and mastfoot and the more energy we dissipate in shock-absorbing deck
pads and uni, the longer our decks will last.

Mike \m/
To reply directly, remove the SpamDam.

Quote:
> Does jumping and landing hooked in put more or less stress on your
> board?  I know it probably depends on a bunch of stuff.  I'd think for
> nose first landings it's probably worse because in the worst case
> scenario where your weight is too far forward you could end up putting
> a large point load through the mast foot.  For tail first landings I'd
> imagine there could be less stress because the harness is spreading
> the loads between your feet and the mast foot.

> Any other opinions?

> Fintan.


 
 
 

board damage from jumping in harness

Post by Hoppe » Mon, 31 Jul 2000 04:00:00

Mike, how much of a difference do those chinook suspension-like
mast bases make?

I think a big factor in whether or not you come down hard from a
jump depends on what happenned during the flight.   As I have
learned recently, there is some great flight physics if you will
associated with using the sail to stay aloft and float down as
much as possible.  The people who can jump around here talk
about staying sheeted in as much as landings.

Just my $0.02, but you are probably aware of this sort of thing,
in which case, I encourage you all to write more about jumping,
so I can learn more about it.

Dave

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board damage from jumping in harness

Post by Mike » Tue, 01 Aug 2000 04:00:00

The parachute ... er, sail ... can dramatically soften the landings, and in
two dimensions, so to speak. Even I can use it in two ways to affect the
landing harshness; I've seen Bruce appear to use it a third, which he
denied. Other jumpers, far  better than I, use it in many other ways to
affect their flight attitude and path in other ways, such as loops,
nose-first landings, etc.

As far as the parachute effect goes, it can make a huge difference in
landing impact. If one just takes off, sheets out, and lets gravity do the
rest, he's likely to land like a ton of bricks if the air was high enough.
After all, I haven't jumped off the roof of my home since I was 50 or so,
out of concern for my ankles. Yet I jump higher than that every chance I get
on the water, and land roughly only when it's MY fault, not gravity's.

The two dimensions I referred to are impact and forward speed, and the same
rig control technique can dramatically reduce both for easier landings, even
though it's real purpose, to me, is to increase the height of the jump. You
can try it next time you get 3-4 feet of air. Just jump hooked in, and once
your fin clears the water, look up. Just face upwards hooked in, and you'll
feel like you doubled your jump height. This does two things, judging by the
feel: it converts forward momentum into altitude, which can slow your
touchdown speed to what feels like zero, as though you could land on an egg
without breaking it. Then you just bear off, bounce the tail with
foot/leg-power a time or two to unstick the board from the water, and resume
planing.

The first time I tried that after a friend suggested it was on a 3.2 in
2.6-2.8 conditions (there were only two or three of us left on the water in
a big Gorge spot, with the other few dozen sailors long since on shore), and
it wasn't until just after I nailed an overhead ramp head-on at speed while
heading north towards Washington, looked up at the sky, and saw Oregon enter
my field of view inverted at the top of my screen, that I realized John hadn
't advised me how to get OUT of this position. I thought of several options,
including sheeting in or out, reading up on sail control (it felt like I had
that much time on my hands), or bailing. I didn't know whether to sheet
differently, I didn't have a book with me, and I don't throw away my
parachute, so I chose to freeze, hooked in and sheeted in.

As the combination of forward speed and increasing descent speed created
drag on the rig behind and below me,  I "outfell" it, and rotated back into
a normal attitude for a planing touchdown. THAT'S why John hadn't told me
how to get down from the jump; you don't do ANYTHING.

When doing this on lesser jumps, anything from 4 feet to over mast-high, you
can almost hang there with your board nose up high, then just look down for
a landing spot to initiate the forward rotation that brings you back to the
water in a normal attitude. It's a quick jump/float/rotate/land sequence in
a 4-5-foot jump; in a 10-footer it FEELS more like jump/look up/hang there
defying gravity for a few seconds/look back at the water/land on an egg. In
this manner even a big jump can produce a touchdown you literally will not
feel.

You can jump high while pinching hard into the wind, raise the windward rail
to expose the board bottom to the wind and sheet in a bit extra, and land in
a broad reach for a screaming-fast-landing aerial off-the-lip.  You can NOT
show the board bottom to the wind and land still planing in that same high
pinching reach, extending your legs to "pre-land" the jump with no force on
the fin to avoid a spinout while not giving up any apparent upwind speed.

You can jump, look for a landing spot (a downhill landing beats an uphill
landing all to heck), and advance or delay your landing time to hit the spot
you want by extending your legs or sucking your heels up your ***to alter
your touchdown time by a few fractions of a second and thus your landing
place by several feet. I've seen Bruce hang up there pumping quite hard and
fast. I asked him whether he was doing that to control hang time and thus
pick his landing spot, but he said no, he was just extending hang time in
general.

You can just use your legs/feet to shove the nose down to accomplish a safe
and reversible nose-first landing, or you can use sheeting angle to achieve
forward rotation to produce a less reversible nose-first. I can do the
former sometimes (especially when powered lightly so the risk of a hooked-in
power dive is less); I haven't reliably figured out the latter yet.

I sheet in throughout most jumps, sheeting out only very briefly at
touchdown and only if I think I'm going to land subplaning but way powered
up -- i.e., in a loaded catapult. This also depowers the sail during the
instant of touchdown to prevent spinout. Then I IMMEDIATELY sheet in again
to hunt for a plane again if I haven't landed at full speed. If I landed
with no obvious speed I'll often just stay in both straps, hang in the
harness to keep the nose down while I bear off on a swell face and pump back
onto a plane. If  land on a full plane, I just pretend I never left the
water and keep on sailin'.

And, compared to scores or hundreds of Gorge sailors, I can't jump for crap.

Just throw that sucker into the air, freeze, and you'll have fun. Sailing
away from landings is icing on the cake that comes with more experience. If
you have any fear (aka BRAINS) at all, slap on a helmet and some rib
protection and you'll double your attitude and altitude immediately. I pay
ABSOLUTELY no attention to landing absolutely flat on my back from above
others' mast tips because my back and kidneys are padded by my float vest. I
never bail frum jumps, for a few reasons. It's only water. I'm not getting
these double and triple mast-high jumps some guys get (I'm still trying). I
wear rib, head and face protection. I don't throw away perfectly good
parachutes. And after jumping dirt bikes and snowmobiles much higher and
farther (off dunes and cornices) than I'll ever get a windsurfer off water,
the altitides I achieve in swell are just FUN, not scary.

To get more lift off any given jump, thrust your legs into the base of the
ramp as though trying to get max height off a ***oline from a standing
jump.

That's an off-the-cuff start. I'm sure some of the better wave and big-swell
sailors than I can add a great deal to this.

Mike \m/
To reply directly, remove the SpamDam.

Quote:
> Mike, how much of a difference do those chinook suspension-like
> mast bases make?

> I think a big factor in whether or not you come down hard from a
> jump depends on what happenned during the flight.   As I have
> learned recently, there is some great flight physics if you will
> associated with using the sail to stay aloft and float down as
> much as possible.  The people who can jump around here talk
> about staying sheeted in as much as landings.

> Just my $0.02, but you are probably aware of this sort of thing,
> in which case, I encourage you all to write more about jumping,
> so I can learn more about it.