In other words, the boat is ballasted with a lot of mass far forward,
as Jeff was contending earlier.


JimC wrote:
I never stated that the ballast mass is "far forward", DSK, and I don't
think Jeff did either.

If Jeff didn't, then why were you arguing with him over that
exact point?

... As to the moment of inertia during pitching, the
motor, after all, is about the same weight as a crew member

A very very large & well-fed crew member.

... and though
its slightly aft of the cockpit

In other words, it is as far aft as it can be, and still be
part of the boat.

.... its weight (mass) is not a great
factor, as some of your buddies claim. (As previously stated: "I doubt
seriously that the weight of the motor is a major factor.")


Whoever stated that is an idiot.
It's 200+ pounds at the farthest aft extremity of the boat.
You want to claim this doesn't affect pitching moment "very
much" whereas knowledgable sailors know that weight in the
far ends of the boat is bad for steering & worse for
pitching. Not a "major factor?"




Between the ballast far forward and the engine wieght far aft, it's
hard to imagine a worse set-up for good sailing performance.


Actually, of course, the ballast is centered only slightly forward of
amidships, as we have already discussed. The motor, weighing only 200 -
250 lb., is of little consequence.


Yeah, I bet you can carry it with one hand.

"Of little consequence" except for the boat's poor steering
& worse pitching.


Does the weight of the keel affect pointing? Funny, I always thought
that had to do with the basic rig design... aspect ratio, sheeting
base, etc etc... keel foil configuration plays into it somewhat I'm
sure, but how does the wind know (and why would it care) about the
weight of the keel?


As you probably know, a weighted keel positioned five or six feet below
the hull entails more leverage

Which does *what* exactly, for POINTING?
Please explain.


.... provides a more efficient righting
moment than the same weight of ballast,particularly water ballast,
positioned within the hull.

Why "particularly" water ballast? Does gravity care if a ton
of ballast is water or lead or feathers?

.... For its size, it a deep, weighted keel is
more efficient in keeping the boat in a nearly upright position as winds
increase, permitting more efficient translation of the force of the wind
into forwardly directioned forces.

That may help it's speed, but how will it affect the boat's
pointing?


... The aspect ration of the keel is, of
course, also a factor in preventing lateral "sliding" of the boat,

No it isn't. The aspect ratio is a factor in the expected
lift/drag ratio of the foil.

The total amount of lift generated by the foil determines
the leeway or lateral sliding of the boat.



.... and
the Mac 26M has a retractable dagger board that is quite narrow.

Meaning what?
You started out to explain pointing, and so far you've
fumbled around in the dark in left field. You *almost*
mentioned something that might be related to pointing, but
you got it worng anyway.



... To
compensate for the relative inefficiency of the water ballast as
compared with a heavy,weighted keel, the Mac has a total ballast
sufficiently large to keep the boat upright. After years of mods and
improvements, the current model, with appropriate reefing, sails ratehr
well in pretty heavy weather. (For example, mine was heeling at only 20
degrees Saturday in 15 knot winds, with the first reef taken in.)


And what was your VMG to windward? Best speed on a reach? If
the wind is strong enough to reef, then you should be able
to plane.

You say the boat sails rather well, my observation (many
times over) is that they sail poorly. Almost any decent
sailboat will beat them downwind and a potting shed will
beat them upwind.



Are you tacitly admitting that Mac-26Ms don't sail to windward very
well? We already know that's true of the M26X.


No I'm not tacitly admitting anything. I'm openly stating (once again)
that they don't sail to windward as well as conventional sailboats with
weighted keels. It's one of the compromises of the particular design.


So... we can agree it sucks at sailing to windward.

Do you think perhaps the weight of the motor... and the huge
flat aft sections necessary to float it... have anything to
do with that?



I'll remember that the next time I'm racing, DSK. But actually, I didn't
buy the Mac with that in mind. I bought it to enjoy the overall sailing
experience.


Actually, if you're reefing & heeling & all that stuff, it
must be almost the same as sailing.You mean, the experience
of sitting on a boat with sails up? Pity you need that huge
motor to actually go anywhere.

BTW many sailboats will go faster than 13 knots.



... Rather, it's the compromises relating to the internal ballast,
trailerable hull, and lack of weighted keel. (The metactric effect.)




Please explain. I know about metacentric height, but have never heard
of "the metacentric effect."


The metacentric height is considered the distance between the center of
gravity and the metacenter. By "metacentric effect", I was referring to
the fact that the righting force is proportional to the metacentric
height times the sine of the angle of heel. Thus, a conventional boat,
with weighted keel low in the water, would have a lower center of
gravity than the Mac and would therefor tend to be less tender.


Good, but not quite right. The metacenter is figured as
height above the waterline. A lower center of gravity
doesn't affect the metacenter at all, it is strictly a
function of hull shape.

Shall I explain curves of righting moment? It's a key to
understanding how different boats sail differently... nah,
maybe some other time. For now, let's just say that there
are effectively 2 forces producing righting moment, one is
the hull shape which produces initial stability... how
tender the boat feels when you step onto the gun'l from the
dock, for example... and the other is reserve stability,
which is affected by how low & heavy the ballast is, and
produces righting moment at high angles of heel.


... Again,
the Mac 26M does entail compromises, but after a number of years of
development and modifications, it does the job. (If it didn't, I would
have capsized Saturday in the 15-knot winds instead of sailing along
with a 20 degree heel.- Right?


The fact that the boat doesn't fall over helplessly in 15
knot winds is good, agreed.



No, the 2M isn't flat aft.

I guess it depends on what you call "flat."
http://www.improb.com/airchives/pape...i3/kansas.html


... In contrast with your statement, it does plane easily and
smoothly.

Then why won't it plane under sail?
Lots and lots and lots of boats plane under sail. It has
been known how to design sailboat hulls & rigs to plane
since 1928. How the heck modern can the Mac 26 M be if it
doesn't incorporate this concept?



And just where did I say that the Mac 26M is a "sooper-dooper hot
performing sailing machine", or anything of the kind?

Well, lately, you've been admitting that it's slow. But hey,
that's of no consequence, just like the increased
hobby-horsing due to the weight of the engine on the transom.


... I've said that the
Mac 26M is fun to sail, but I have consistently stated that it doesn't
sail or point as well as a large displacement boat.

Or a small one.

... Instead of saying
the Mac is a great sailing machine, I've said that it has limitations
and disadvantages when compared with conventional vessels.


It's all about compromises.


Do you consider lying about what I said, as you just did, a necessary
evil acceptable when convenient, DSK?

I haven't lied at all. You however have not only lied but
also contradicted yourself a number of times. Why is that
necessary to defend your boat?



... Do you have no self-respect whatsoever, DSK?


Of course. I also have a lot of fun sailing, only not on a
Mac 26 M or X.

I am glad you enjoy sailing your boat. That's what it should
be all about.

DSK