[re-posted, without the  characters that sometimes appear with
Unicode -- sorry]
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Gardner,
You're welcome. Thanks for taking the time to read them.
BROAD REACHES
The trick with the airoil, generally, is to treat the main like a
jib: let the sail out until it starts to luff/stall, and then pull it
in just enough to get good shape. The telltales will tell you what you
really need to do, but that's a general description.
So, in very light wind, assuming you have a fixed boom or a vang to
keep leech tension, you might have the boom out at 30-40 degrees.
Inevitably some of the drive will come from catching the wind, but that
lift on the leeward edge is very valuable.
At higher wind speeds the boom will definitely come in. The first
(and only) time I sailed an R33 catamaran, I had to be told repeatedly
to haul in on the main, and/or windward with the traveler. I didn't
really get the process until it was explained to me that the easiest
thing to do was to pretend I was sailing upwind the entire time. After
that the boat really picked up speed.
The same thing happens on a broad reach, depending upon how much sail
you have up and how strong the wind is. If you've got enough sail up
in a light wind, the angle really comes forward, and you can get a
surprising amount of lift from the sails. The boat won't be
lightning-quick, but you can go downwind faster than if you run.
You might just want to sail dead downwind and not deal with tacking.
If you've got open water and you want good VMG leeward, tacking isn't
too bad -- just once every now and then.
If you want to duel with a mono in a half-mile-wide inlet, that's a
lot of gybing. I've done it when someone caught up to me downwind in
my fancy multi, and sneered in triumph, but it was a lot of work. I
probably had four times his boat speed, which was fun, but only gained
about 200 yards on him per tack, which was less satisfying.
Nonetheless, that's a mile after nine tacks, which does amount to
something.
The comment on lift on a broad reach was mostly to illustrate what
you can do with a rig if you want to, particularly an una or an easyrig
that can be gybed quickly and without five crew handling sails. Most
of the time it's just easier to run.
CONTAINERS
I assume you're talking about a hi-cube container a 9' rather than a
standard container at 8'. Is that correct?
What about a 48' container? They don't go everywhere, but you might
not need to go everywhere. Maybe just to a major port where you'll
then sail to your real destination. Perhaps the goal of the container
is more for secure storage, and the ability to skip the big crossing,
rather than to get to the final destination.
Or two containers? If you may never ship via container, but want the
option, two containers could really open up your design. Going to a
major port, the expense might not be prohibitive, with both containers
costing noticeably less than a 40' x 20' multihull. Plus you get the
security of having your boat in a strong, weatherproof, steel box, and
will also have room to bring along extras. Perhaps even without trying
to fit everything with 1" of the side.
It's possible that you'll be happier with a larger boat that's not
constricted by a single container, even if you do have to spend a few
thousand dollars more to ship it. The real key is how likely and how
often you think you'll be shipping via container. Like the people who
get a 45' monster that will handle the Southern Ocean, because they
want to go cruising someday, and then never use it because they really
only daysail, it's important to think about how important that
probability is.
I'm just musing here. I haven't looked into container costs for a
while.
I take it that, now that you are going with two-part masts, the ICW
bridge height is your design limitation? I can see how that hard
bimini would cramp your style if you want a BN near 2.0. The long
foot, and a very large roach (curved gaff like Robert's plan?), would
be a minimum. Schooner would be nice, but would also be more work. It
really depends upon how often you think you'll need to tack or shunt.
- Mike
Gardner Pomper wrote:
Mike,
I love getting those long replies of yours. They are always well thought out and interesting reading.
One thing that they also tend to do, is to highlight the unspoken assumptions I am laboring under. But, before we get to those, I have a very basic sail question: How does the airfoil help with downwind (broad reach or more) sailing? Perhaps I am just stuck in the old stayed rig mindset, where the sail really can't be let out past 45 degrees without the sail chafing against the shrouds.
With a rotating, unstayed rig, do you just put the boom out at 90 degrees to get lift from a broad reach? Then beyond, up to 135 degrees when running? It would seem that the lift vector would then be on the opposite side of the boat from the boom (i.e. if the boom was out to starboard, the boat (if a monohull) would heel to port). Of course, if the boat really will sail at wind speed, then it seems that the speed of the boat will move the apparent wind forward of the beam most of the time.
Rob, is that true on the Rare Bird?
Back to my unspoken assumptions. You are correct that I want a boat that I can singlehand and that will perform well in light winds (Chesapeake Bay) and upwind (beating down through the Bahamas). There are a couple other things I also want; large bridgedeck, covered with either a hardtop or bimini. To do this, I either need the boom higher than the hardtop, or shorter than the distance from the lw hull to the bridgedeck.
I have a layout that I like for everything other than the rig at the moment. It comes apart and will fit into a container for shipping (although I am not really sure that saves enough over a delivery to make it worth while). In order to make that fit, the lw hull can be no more than 4.5' high. Anyway, this means that if I use an easyrig, with a 2 part mast, the boom needs to be only 7.5 feet long, or 6' in the air (so it doesnt hit the hardtop). I could go with a schooner rig, but the masts would still have to be 39', which means they need to be 2 part masts, which sounds expensive? (Did I mention that my most important unspoken assumption is that the boat be low cost so that I can actually build it??)
Anyway, I am currently at am impasse on this one. I am trying to build a 3D model in google sketchup and then I will post the plans and 3D rendering in the group to get suggestions. At the end of the day, I am pretty sure I am just going to get Rob to do a design of his own, based on my favorite layout. His plans always seem to be better than mine, so it will be worth the money to me.
Thanks again for the feedback,
- Gardner
York, PA
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