Subject: Re: [harryproa] Proa sail downwind poorly? |
From: Mike Crawford |
Date: 4/19/2009, 12:14 PM |
To: harryproa@yahoogroups.com.au |
Reply-to: harryproa@yahoogroups.com.au |
Proas are no more likely to capsize han other multis. It's a simple
equation of heeling moment (sail area) versus righting moment (boat
weight, moveable ballast, crew).
As you point out, the pacific proa crowd feels their design is
perfect. As Rob points out in his online articles, it's perfect with a
crab's claw sail, on a beam reach, in trade winds, with highly-trained
nimble crew who can dance windward and leeward to keep the log at the
right level. Since the goal is to sail at the maximum heeling moment
most of the time, this invites disaster if you don't have the perfect
crew and conditions.
It's the same reason why the Reynolds 33 is proclaimed a dangerous
boat and forbidden from some race circuits. It's got a massive rig,
and people like to use that rig to fly a hull as much as they can.
I've been on one and while I was only able to fly a hull for a few
seconds at a time due to light winds, I have to say it's great fun.
But I don't do that with my own cat because I'm normally out alone. If
you fly a hull long enough, you're going down. Maybe not for months or
years, but it's only a matter of time. It doesn't make catamarans
dangerous, and it doesn't even mean the r33 is dangerous. It means
that capsizes happen when people sail multihulls right on the edge for
long periods of time.
You can argue that a Harry is less likely to capsize than an
equivalent cat or or tri for the following reasons:
- Longer waterline keeps the bows from digging in.
- Sailing forces directly in line with the leeward hull, which is
also the longest hull, help to keep the boat from tripping over an
equivalently shorter catamaran hull, or worse, an even shorter trimaran
hull.
- A greater percentage of weight to windward will provide greater
righting moment for the same sail area. This is a safety feature as
long as you use it carefully though -- you could just keep pushing
until you're flying a hull, and then you're on the edge again.
Nonetheless, this righting moment may let you hit your max reasonable
speed long before it's time to fly a hull anyway, in which case there's
no need for white knuckles.
- The flexible carbon mast will absorb gusts that would put a stayed
boat right over. If you're near the edge with a stayed mast, there's
no way to stop quick a gust (quick enough to where dumping a sheet or
traveler won't help -- because you're on the edge), which might be 40%
stronger than the average wind speed. But if the mast can flex, you
gain a lot more reaction time, especially if you're got a rig that can
dump force at a moment's notice (see next point).
- A balanced easyrig will let you go to near zero heeling moment at
any time. This is extremely important (whether on a proa or other
multi) if you want to push the envelope safely. Dumping a mainsheet on
a normal sloop rig sometimes adds to power and heeling moment, and
sometimes can't be done. Dumping a large headsail can also be
problematic. Trying to dump both at the same time, singlehanded, is
highly unlikely. Going to zero on an easyrig Harry is as simple as
releasing a single sheet.
- A balanced rig will let you infinitely tune the heeling moment at
any point of sail, even dead downwind. Anyone who has ever been caught
in a multi running in winds close to the pitchpoling force will tell
you how vital this is. It's quite scary to be out there knowing that
you can't reduce sail area because the main in pinned to the shrouds,
and you can't simply round up because that might cause you to dig in a
bow and either capsize or pitchpole.
- You can always shunt, at any time, even if you're 50' off a lee
shore, and do so while feathering the sails on "just so", in order to
avoid any sudden stresses. Trying to gybe, or come about through 200+
degrees, in a catamaran or tri, while eyeing the granite of a lee
shore, is not a good feeling. Being able to just switch direction is a
superb safety feature.
- You can always just reverse. There are times when the wind and
wave period/height make a given angle of sail too dangerous to
continue, but at the same time too dangerous to let a cat or trimaran
turn around safely. Instead of trying to negotiation the mother of all
turnabouts, you just head back in the other direction. That's as
valuable in preventing capsize as the ability to shunt.
- This is the one multi design that could elegantly self-right after
a knockdown without any outside assistance. If your boat is light
enough and the wing mast is tall enough (to provide enough flotation),
this turns a nightmare into simply a bad day. Trying to do that on a
40' multi of any other design wold be highly unlikely. While I don't
think anyone has tried this, or wants to try it, on the cruising
Harry's, Rob has done it many times on his Elementarry , and the
physics work the same with a heaver boat and taller masts.
---
I'd say that as long as you're sailing wisely, and not trying fly a
hull all the time, you won't find a safer design.
I'd personally go with a taller and/or telescoping mast if you want
more speed. That preserves all the benefits of the balanced rig listed
above. Besides, does anyone other than a Decision 35 crew on Lake
Genevia really need to push the SA/D past 50 or 60? If you're already
there, I'm not sure it makes sense to ask for more sail area.
But as Robert points out, this does mean you'll either have a taller
mast or a telescoping mast. I'd probably go for taller, both for the
sake of simplicity and also for preventing going past 90 degrees in the
event of a knockdown. But since I'm primarily a daysailer, my opinion
is skewed.
- Mike
Gardner Pomper wrote:
Hi,
I have been listening to a podcast called "Furled Sails" which is
mostly about small sailing craft. One of the events they have covered
alot has been the Everglades Challenge, which is a 300 mile race from
Tampa, FL to Key Largo through the Everglades. It is mostly kayaks and
open monohulls, but they have had a few proas as well.
The reason I am posting is that they have made a number (3 or 4)
comments about proas having not being able to sail downwind well. I
don't know if they mean speed or stability. Most of the criticism I
have heard about proas has been capsizing; not downwind performance.
Can anyone here tell me if there is an issue with proas sailing
downwind?
I assume the proas they are referring to are traditional pacific
proas, so I figured I would just get denials from the regular proa
groups. I thought people here might have more objective and informed
opinions.
If this is purely a sail size issue, I have a related question. Would
it be possible/reasonable to extend the forward boom on an easyrig and
mount a roller furled screacher there for light wind and downwind
performance? Maybe sheet it off to the end of the main boom?
Thanks,
- Gardner