Well, XL2 is some boat, but now that I have the proa bug, I can't say
I'll be making any offers.
I look forward to hearing about all the details (at least at
harryproa.com) when you do sell XL2 and start a proa. I won't have the
time to consider a new boat for a few years yet, so I'll have to content
myself with upgrading my current one and watching the proa scene from afar.
--
In the meantime, I'm curious as to your choice of rudders and boards.
I keep on looking at the harry design, not liking it, but then not
liking anything else I come up with.
With daggerboards and spades, you could tiller steer, or even use an
autopilot, without having to worry about reversing rudders on each
shunt, the spades will create less drag, and you could put the major
stresses on the boards in trunks. However, beaching the boat could be a
problem, as could hitting an unexpected sand bar or rock. Rudders plus
boards would also add some more drag.
As funky as Rob's system is, it does prevent leeway while also
steering, and does so with a kickup failsafe. The fragile looks make me
hesitate a bit, but I suppose that the forces aren't that difficult to
design for if you know what you're doing. I just wish the rudders
didn't have to be rotated 180 degrees every time the boat shunts.
Blind Date originally was supposed to have symmetric foils (
http://www.basiliscus.com/ProaSections/ProaIndex.html ) that wouldn't
have to be rotated around when shunted. I asked Rob about this, and he
said that a vertical foil would be too unstable, which is why they went
with the swept foils. That made sense, but then I started looking at
catamaran daggerboards, many of which are vertical. Are these too unstable?
On a proa, the daggerboards would certainly need to be vertical if
they're going to work in both directions. If you can make that work,
then you should be able to make a steering system work with vertical
symmetric foils, in which case you could skip the spade rudders and
still keep the tiller steering.
Of course, you might say that boards in trunks are sturdier or more
reliable, and if you're always pushing the boat to the edge, this is
something to consider.
---
I keep hoping that with enough people looking at the problem, new
solutions will emerge.
- Mike
nudd@ozemail.com.au wrote:
Quoting Mike Crawford <jmichael@gwi.net>:
You make good points with respect to stays and headsails. However,
one could also make the case that technological developments in the
past fifteen years have made stays and headsails less important than
they used to be.
Arguments for a wishbone boom, unstayed, wingmasted una rig (in
either a single or schooner setup):
- It's common for boats competing for the speed record to lack a
headsail, and instead use a variation of an unstayed, wingmasted,
shaped main.
- The speed record current is owned by a windsurfer using a wishbone
una rig. Granted, Maynard uses a planing board the size of a large
spoon, but he's still using an una rig.
- A lower speeds, Wyliecat boats (catboats that use a single
wishbone-boomed una rig) have beaten larger boats upwind, when many
people would argue that a headsail will really help.
- The una rig, especially if nicely tensioned, presents a very
efficient swept back profile that works well without a headsail.
- Stays generate a surprising amount of drag without contributing
anything to forward motion. While a portion of a flexble unstayed rig
will also generate drag when the rig flexes leeward, it will pop right
back into generating lift once a gust passes.
- The wishbone una rig is particularly adept at generating lift, and
should require relatively light winch loads unless running. With the
sail being self-vanging, the only load on the mainsheet is that which
is required to pull the sail just past the point where it luffs.
- With only a boom tensioner and a mainsheet, the wishbone una
requires less time and effort to achieve optimal sail shape. Unless
you have a full crew to pull strings all the time, the simpler design
is likely to enhance speed over the course of a race.
- The ability to fly the windward hull is actually much more
critical to reducing overall drag than extra sail area or stays. But
keeping that hull airborne, or just skimming the water, is a delicate
balancing act. In this scenario, you're much more likely to be able
to hold that balance with a rig that can absorb gusts than with a rig
that doesn't give at all.
- The lower center of effort on a schooner una rig, as compared to a
taller easyrig, will likely allow it to generate more lift for the
same heeling moment. Given that both boats use two sails, and a
stayed easyrig will have some additional drag of its own, the lift to
drag ratio of the schooner rig will probably be equivalent or better.
---
With that said, I do love the easy rig -- it's hard to dislike a rig
that's so darn easy to sail.
It's just that any boat in my future plans needs to fit under 65'
bridges, and a 64' easy rig on a boat the size of the visionarry isn't
going to give me the light wind performace I'd like. Thus, I've
adopted a schooner rig with wishbone-boomed mains as my new dream, and
have in the process become quite a fan of the una rig.
- Mike
---------------------------
I agree with pretty much everything Mike has said here.
As soon as someone will give me A$250K for XL2 I will start on a 50'
Harry with
unstayed schooner rig with wishbones, fixed spade rudders, tiller
steering and
daggerboards.
Paul Nudd
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