The proa will also require less sail area to drive, as well as have 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 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 cruising and singlehanding.
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 on average 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