I's possible that I'm missing something.
Could you show me how to stall a square/elliptical rig, and leave
it stalled for a few minutes, even if the wind direction changes or
the boat drifts? That would do a lot to help me see the safety of
the rig, and should be easily demonstrated on a model if it's
possible.
I've flow four-line kites since the 1990's, so I'm familiar with
how they power and depower. My favorite thing is to use the kites
on a flat beach during low tide, flying along on a three-wheeled
kite buggy. Great fun. That said, I've never been able to just
leave my kite alone while I get up to pee.
There's also the worry of the momentary shock loading of the
system during a shunt as the wing turns from one side to another.
Your "Planning Proa squared" appears to demonstrate this issue,
with the windward hull popping off the water momentarily during many
of the shunts. Get hit with a gust at the same time, and the boat
is gone.
Which is not to say it's a bad rig. Your tests have clearly shown
how fast it can be. I just personally have an issue putting this on
a boat with a stove, fuel, water, head, and passengers.
---
This is actually one big reason that I'm planning on a proa in the
first place.
If I dump my current catamaran in water less than 30' deep, it
will likely cost me between two and six thousand dollars to replace
the equipment that could get damaged. I love having a boat with an
SA/D over 50, but it does worry me when pushing the boat. That kind
of cost figure for a capsize tends to lead to white knuckles when
flying a hull. Especially if I'm at an angle where dumping the
sheets will actually increase the heeling moment, leading to a
knockdown or pitchpole.
So it's my dream to get a boat of similar speed, but with greater
righting moment and longer waterline, and a more powerful rig that I
can always just depower by letting go. Up to this point, you
wouldn't think that fast and safe could go together with the same
boat. But a WTW proa, or catprao, can be an impressive design.
- Mike
tsstproa wrote:
When you stall a foil there is no load. Thats reason why planes fall out of the sky Or Kites fall back into the windwindow.
The key is the no load and when and how to achieve it and when and how to bring it back on with out the sudden snap. 4/5 line Kites do this by controling the leading edge and adjusting aoa with the back line pulling in or out accordingly. If you don't have the experience its harder to imagine the possiblity.
http://www.youtube.com/watch?v=LrezrEfQj68
Todd
--- In harryproa@yahoogroups.com.au, Mike Crawford <mcrawf@...> wrote:
>
>
> The Maltese Falcon is most impressive.
>
> However, the rig worries me because there's no easy way to depower it,
> and keep it depowered without attention/effort, if you're not on a mega
> yacht.
>
> The Falcon is an extremely heavy monohull with full electronic control
> of those sails. Need less power? Push a button, and motors roll the
> sails in between the fixed arms. If things get hairy, the boat is heavy
> enough and strong enough to hang on until the sails are in. While
> sailing, electronics will also keep the sails at an optimum angle to the
> wind.
>
> Assuming a proa won't have those features, I'd have to say this is
> more of a racing rig, to be used only by those who really know what
> they're doing, and are prepared to capsize, than on a boat where you
> might go cruising, or on a single or dual-handed distance race.
>
> Presenting that full face of the sail to the wind during a tack or
> shunt is a problem. On a small boat, or a model, it might be fun to pop
> the windward hull out of the water during a shunt, and then to zoom off
> at the amazing speeds the dynarig is capable of. But what if you're on
> a large boat that's not easily rightable after a capsize, perhaps in
> high seas with gusty winds? That could be a disaster waiting to happen,
> particularly if there's only one person to handle the sail.
>
> Reefing the sail in those same high seas and gusty winds could also be
> a problem. With an easy rig, una rig, or junk rig, you can let the
> sheets out, the sail will weathercock, and you can take your time while
> reefing, getting a drink, peeing, or tending to an injury or equipment
> failure. For as long as you want. On the other hand, the square rig
> won't stay weathercocked in one direction, and stands the chance of
> presenting the full face of the sail to the wind, even if for a short
> period of time.
>
> Even if the boat does not capsize, shock-loading components to that
> level isn't a recipe for equipment longevity.//
>
> Again, I think the square/dynarig would be great fun on a 20'-er in
> warm waters (or with wetsuits), where you could play with the boat like
> a Hobie, flying a hull, and righting the boat if things don't work out.
> But I couldn't imagine putting that sort of stress on a lightweight proa
> in the 30' to 50' range. Putting a boat that size on its side is a bad
> day, no matter what happens afterwards.
>
> - Mike
>