This is a bit of a summary to tie a few loose threads together.
There are a lot of things being said that are true on their own, yet
don't indicate the bigger picture for weight-to-windward proas.
GENERAL
Basically, the way to evaluate a harryproa is to see how the full
boat performs across a broad range of criteria.
A catamaran will carry more weight. A trimaran with a Bermuda rig
will be faster at times if sailed properly. And so forth. The
harrproa is not going to be a better catamaran than a catamaran, nor
a better trimaran than a trimaran. It would be very easy to say
"Wow, that's a small load capacity, or tiny accommodations, for a
40'-er".
Or, you cold say, "Cool! I get better accommodations than a 30'
trimaran, with the benefits of a 40' hull, and for a much lower
cost!"
If you take a fixed budget of hull weight and/or dollars spent
(which relates to hull weight), the harryproa will likely :
- Be significantly faster over the course of a day for a
non-expert crew
- Be smoother, more seaworthy, and more seakindly
- Offer more accommodations in terms of double/queen bunks
HULL LENGTH, SPEED, AND SEAWORTHINESS / SEAKINDLINESS
"A transom stern damp out most of the hobbyhorsing."
"As I understand it, the key factors to reduced hobbyhorsing is
longer hull, bows that do not accelerate upwards as they bury, fine
sterns that don't lift as they are lifted on a wave, no rocker, and
mass closer to the center of mass"
"Do you mean to suggest that a proa does not ride well for its
size?"
"Its a good question, field evidence has it that longer hulls
pitch less, and here we seem to be talking longer in terms of 33%"
"That may not incorporate the factors of sailing amongst and
through waves. For this you want as thin and pointy as possible."
A purpose-designed catamaran or trimaran, with a Bermuda rig
located relatively aft, will pitch less when sailing in decent
water, particularly when driven hard.
This is because the hull can flare aft to support more weight,
such as crew, motors, and rig, the aftward weight of the rig will
counter pitching moment, and the larger head sail due to the aftward
rig will provide a bit of vertical lift. The physics of a
single-ender make it easy to optimize in these areas.
BUT... A harrproa will be a better, and faster, boat given
either: a) hull weight, and/or b) hull cost.
- Slender wave-piercing and wave-shedding hulls make it less
likely to dig in and actually pitchpole.
- The lift on the bows and sterns will be muted because of their
shapes, cutting down on hobby-horsing (particularly without the
buoyant aft flare).
- The longer leeward hull allows both hulls to hit waves at the
same time when beating, cutting way down on the corkscrew effect.
- The longer hulls, given the same weight or cost, will be
faster and more seaworthy.
- The unstayed rigs can completely depower at any point of sail,
for as long as you need, from the cockpit, by dumping the sheets,
even when singlehanded, allowing you to carry more sail area more
safely.
- The flex in the unstayed carbon masts allows for automatic
dumping of wind during gusts, allowing you to carry more sail area
more safely.
- Shunting allows you to come about reliably and safely, without
panic and fanfare, in huge winds as well as very light winds.
- The same goes for gybing in heavy winds (gybing in light winds
is easy in any multi).
- The ability to safely reverse course prevents you from getting
pinched into a dangerous spot with the boom pinned to the shrouds,
unable to turn when needed.
- Weight-to-windward results in a higher righting moment per
hull pound and hull foot.
All told, when you look at a complete race course, or a complete
voyage, the proa's longer hulls and unstayed bidirectional rigs
allow for a higher average speed due to its ability to carry more
sail area, more safely, per pound and per dollar. It also will
require less sail area to drive, as well as having a higher righting
moment for the same weight.
Caveat: this may or may not be true for a hardcore racer. If
you've got an expert athletic crew that's ready and focused 100% of
the trip, then the optimized trimaran or catamaran will likely come
out ahead, though with a rougher ride and higher risk factor.
However, that base assumption might be too optimistic for many
races, and is definitely way too optimistic for standard crews,
singlehanders, and cruisers looking to keep higher average speeds
per dollar spent.
The proa is going to be smoother and faster on most points of
sail, with less effort and risk.
---
The same thing, said differently...
In terms of hull weight and dollar spent, brute force, if
implemented with an elegant design (in which case perhaps it's not
brute force) is more effective than detailed optimization.
If you can fit a longer more wave-piercing flat-bottomed hull into
your weight and dollar budget, it's going to be faster and more
sea-kindly than a shorter hull with fancy/optimal geometry.
Likewise, length is going to be more effective in a broader range
of circumstances than foils, while also being less expensive, and is
definitely going to be a lot less complex and prone to damage or
failure (which then slow you down).
If you can fly more sail, higher up, because the unstayed rig
automatically dumps some power in gusts, and can be completely
depowered with a quick tug even while singlehanded, then the boat
will be faster than a Bermuda rig with 46 sail-adjusting lines.
(and 117 points of failure).
---
And one more try, from a third direction...
Some of my sailing friends think I harp too much on safety. Which
is fine -- everyone has his own set of criteria.
(Of course, my friends having been in a 1,100 pound 27' catamaran,
in November, off the coast of Maine, on the way to the boatyard for
the winter, in a blizzard, with 7' seas, feeling the entire boat
lift slightly as it crests each wave -- that experience, among
others, inspired me to place a whole new value on safety and
seaworthiness).
But that said, simpler and safer, with fewer points of failure,
also means a higher average speed through varied conditions.
Take the bad tack that didn't get the multi through the wind, or
the headsail that somehow got caught on a spreader, even though the
spreaders have rollers, or perhaps got stuck in a backwinded
position, then torn, when a crew forgot to uncleat it in time. In
any given race you might see one of these things happen. And
certainly during a voyage. Heck, that's also when the headsail
furler jams and leaves the full genoa up during a surprise squall.
Even if that doesn't destroy the sail or furler, or capsize the
boat, it's still going to mess with your average speed.
Those long, slender, wave-piercing hulls with flat bottoms, and
the simple single or schooner una-rigs, along with the ability to
shunt instead of tack, eliminate dozens of factors that slow you
down at best, and cause damage to crew or equipment at worst.
HULL SHAPE
"So very interesting! It seems hull bottoms don't matter much?
Is it possible to see the effects of a flat bottom? Can you do
round corners vs square? Different radius corners?"
"So I think the flattish bottoms of the latest Harryproas will
work well. I think Rick W has done some simulations and reached the
same conclusion."
Much has been written on hull shape, with many varied opinions.
I'm predisposed to agree with Rick Willoughby on the flat bottoms
for two reasons: a) The flat bottoms work better with intelligent
infusion than a half-circle (meaning: I will eventually be able to
afford to build the boat), and b) One of Rick's designs for a
human-powered pedal boat held the 24-hour distance world record at
one point.
http://openwaterbike.com/news/rick-willoughby-releases-v15-design-document
For many more details on hull shape, see March 2015 in the forum,
particularly two posts that started a very lengthy discussion:
Post 10599 - Flat Bottom Harryproa
https://au.groups.yahoo.com/neo/groups/harryproa/conversations/messages/10599
Post 10621 - Hard Chine & Attached Flow
https://au.groups.yahoo.com/neo/groups/harryproa/conversations/messages/10621
Perhaps the world-record-holding design for pedalboats is also
fastest for proas; it's possible the flat bottom will help a bit
with drag and anti-pitch lift if there's a touch of rocker. Perhaps
not.
But if it can be intelligently infused, then it's the fastest
design within my budget.
- Mike