RE: [bolger] MJ Musings

Enjoy that recommended educational reading from below:

http://groups.yahoo.com/neo/groups/bolger/files/Shoal%20Draft%20Sharpies%2C%20and%20Bolger%20on%20lugsail%20peak%20halyards/

                    

In a message dated 3/13/2000 6:04:16 AM Eastern Standard Time,
giuseppe.bianco@...writes:

<< I think that MJ is a very clever design, and I like it except for the
name and the leeboards, buth this is just a personal bias.

Best, Pippo >>

Pippo!!!! Who cares about self righting, self bailing and "most significant"?
It's the name and the leeboards that count! Steve

John - not only is zephyr a class a1 cruiser - so are you! A dingy and an
extra stove. I love it! Steve ( I'm grinning)

Hi John

"john gerty" <gertyjand-@...> wrote:

> Pippo - Thanks for the semantics lesson

I didn't intend to teach anything, I was just self-ruminating. Sorry if
appeared like that. I use the term COG as well, as it's used in all
boat design books. Luckily enough, the gravity field around a boat is
sufficiently constant to make the two points coincide within microns, I
guess! ;-)

> with Mike O'Brien's summary,"Built as drawn, MARTHA JANE should be
> self-bailing, self-righting, unsinkable, easily trailerable, and fast
> under sail. She's a most significant sharpie."

I think that MJ is a very clever design, and I like it except for the
name and the leeboards, buth this is just a personal bias.

Best, Pippo

Hello Steve - Keep grinning. Your loading assessment is not too far
off. My Honda is only 8 HP not 9.9 so shave off a couple lbs. Guess
what - I DO have an inflatable up there, but it only weighs 17 lb. bag
and all, and can't count as ballast on house top. I agree, I have an a1
cruising vessel, but isn't that what Martha Jane is all about? Her
capabilities are wasted if the only use is day sailing which we seldom
do being so far from launch sites. In fact only once did I take a
couple of friends down to Buzzards Bay for the day. Far more drive,
launch, retrieve, drive than sailing. When we go it's usually long
distance and supplies for a week or two with usual overkill. 2 anchors,
tools and all the plugger nicities. One of our SWS friends forgot his
camp stove up on Lake Champlain, so I found a spare one burner job
under the bunk for them. Be prepared! Can't complain though, cause she
usually out performs her companions even loaded down and with me at the
helm. - John

Pippo - Thanks for the semantics lesson, and I agree 'center of mass
would be more proper', but back in my early engineering days, center of
gravity was commonly used; I was not attempting nautical airs just
reverting to old habits - old fart privilege. You are of course
correct about the O.21 ballast/displacement ratio based on the 2350
lb.nominal displacement. Did you read Steve's grinning (?) response to
my message? He is close to the mark on how loaded down Zephyr tends to
be. Add another 300 or so pounds of miscellaneous gear to the
displacement, and you can calculate ratios of 0.19 or 0.30 depending on
whether you add it just to displacement or to both displacement and
ballast. Figures don't lie, but liars sure can figure?? At least some
of the 'extras' are low enough to be ballast as long as they stay put!
By your benchmarks you may now consider my MJ either more or less
tender than designed. Your choice.

I'm not sure what Zephyr's actual displacement is with or without
impedimenta, but it is probably somewhere near that range. Based on how
she sits in the water I would reduce your 30 cm to about 23 cm for what
that is worth. Since you allow that 'tender' is a relative term, I can
consider Zephyr not a tender boat based on how she has performed, and
how forgiving she has been. From my experience so far I have no quarrel
with Mike O'Brien's summary,"Built as drawn, MARTHA JANE should be
self-bailing, self-righting, unsinkable, easily trailerable, and fast
under sail. She's a most significant sharpie." Like Bennett I have no
intentions of further testing self-righting, but she has lived up to
all my other expectations. Meanwhile I'll live with PCB's "a good range
of stability" and try to improve my skills.
Best to you, too - John

John - Martha Jane's ballast/displacement ratio is 0.21, and I estimate
by looking at the drawings in BWAOM that the center of gravity (center
of mass would be more proper, but less nautical) is at least 30 cm
above the water level. Well, you may not agree, but I consider this a
tender boat. This of course is a relative term. My benchmarks are Micro
and Long Micro. PCB himself speaks of "a good range of stability": he
correctly never mentions self-righting, which ever boat is within its
range of stability.
Best, Pippo

"john gerty" <gertyjand-@...> wrote:

> experiences I cannnot agree with `Pippo's, "---MJ is an inherently
> tender design." or, forgive me Steve, your comment, "----needs little

-

> a mizzen is enough - to knock her over." Are all MJs created equal?

Hi John - I am smiling down here !:-) Grinning actually - as I read about how
stiff zephyr is because I remember how much you told me she weights!
According to the number you gave me a couple months ago I figure that you
have at least three times the ballast that I have! Of course it comes in the
form of batteries, electronics, extra gasoline, drinkable water, canned
goods, books, a 9.9 honda, paddles, head, whatever is in the head, galley,
maps, anchors, line, camera, clothing, lights ( you don't have an inflatable
dingy in there do you?) . John! You could shinny up to the top of the mast in
a gale and not wobble one centimeter - which also explains how you could even
fly a tops'l above your main! Landroval on the other hand has a piddly 500 (
600 now - I added another hundred) pounds of sand and whatever the cooler
weights after lunch is gone! And my little honda only weights 25 lbs and
doesn't even have an eternal gas can :-(

And of course - should you ever need a sea anchor - you have plenty to choose
from
- in my case I would have to choose between my sand bags and my wife. But we
won't go there :-0

Happy cruising. You have a class a1 cruising vessel.

Incidentally - I just heard recently that the nis23 normally carries 700 lbs
of ballast but that the racers ( those who aren't loaded up with cruising
stuff ) normally add 300 more pounds. That's a 1000 lbs. of ballast. Wow -.

steve

Can we handle one more message w/o sinking? Here's Zephyr's
contribution:

New to the group, so who is he? Since October 1993, proud and happy
owner/skipper of Zephyr, the first Martha Jane (and the one in the
BwaOM picture on page 259 despite the caption), built by Richard
Cullison who launched her in June 1990. Richard took Zephyr up to
Gloucester that summer, and Mr. Bolger sailed her. Maybe I'm the oldest
codger in the group with less sailing experience than most of you, but
I have enjoyed my MJ for nearly seven years. I have found her stable,
fast and forgiving of even my worst mistakes. Also Steve and I have had
voluminous e-mail correspondence starting even before he purchased his
plans (Steve, do you hold me responsible?) and continuing throughout
the building of Landroval. With that background, may I be allowed to
add my two cents to the pot? My only previous contribution was no. 3497
Mar. 7 suggesting a possible scenario for Steve's situation leading to
capsize.

I started this before seeing the most recent batch of messages, but I
can now add "well said Donald" to his "Well said Bennett" in their
postings of 10 Mar. Like Bennett, Cullison also built Zephyr `to
plan' with the same exception of 3/8" ply for the cabin top. One does a
lot of walking over that top. And like Donald, I cautioned Steve about
modifications and about the effect of his 200 pounds further aft in
that tempting extra space. I don't know how that might affect handling,
but I have found Zephyr can be made to go a bit faster when I move
further forward in the cockpit, and being `tail heavy' might make it
more difficult to head up in marginal conditions. Try turning a canoe
to windward while paddling from the stern as an extreme example.

The only times Zephyr has approached knockdown were when I made
mistakes like an accidentally cleated sheet in strong, gusty conditions
on Lake Champlain and a poorly controlled jibe on the Chester River
severe enough to catapult me overboard and snap the downhaul which of
course had a weak link I had neglected to fix. That time we were headed
down wind with mizzen furled, wind at least 20, being forced toward a
lee shore and unable to tack around without the mizzen. Fortunately we
had the anchor in the cockpit, so my wife could stop the boat and I
could get back aboard to deal with 200 (less reefs) square feet of kite
(mainsail/boom/yard) tethered only by sheet and halyard, and flailing
madly about trying to destroy everything within reach including me. One
of the mizzen ties had also slipped down releasing a balloon of sail
slatting in the wind violently enough to shear off the mizzen mast
step. Throughout all this mistreatment Zephyr never heeled far enough
to ship any water, and only I got wet. She dutifully held to her anchor
(and probably snickered) while I straightened out the mess. From my
experiences I cannnot agree with `Pippo's, "---MJ is an inherently
tender design." or, forgive me Steve, your comment, "----needs little -
a mizzen is enough - to knock her over." Are all MJs created equal?

Perhaps it is time to sort and assess the mountain of messages produced
so far, and I too am glad Mr. Bolger has returned -his `ruminating'
usually produces excellent results. For what they ar3e worth, here are
some questions and comments that come to my mind:

1. How many Martha Janes have been built and sailed, how many have
really suffered ninety degree knockdownI (is it really 6 of 7?), and
under what conditons did they occur?

2. Which were built strictly to plan and which have design or
construction differences which could contribute to easier knockdown?
For instance, at least one seems to have a heavy mast, and Steve has
said he built Landroval to be bullet proof (is that the correct word,
Steve?) to survive the Florida climate. If memory serves me all his
plywood panels have fiberglass/epoxy skins on both surfaces. Would that
add significant topside weight to require more ballast?

3. All the discussions of ballast material and location boil down to
`500 pounds is 500 pounds' as long as it is in the designated space and
cannot shift. And that sealed space is what determines that part of
total buoyancy not the material within. That is why I first suggested
to Steve that he might consider sand bags at least as a simple
temporary way of providing ballast if he wanted to avoid wet tanks and
thru hull openings and was willing to tote the extra trailer weight. (I
suggested 25 ten pound bags tightly packed in each tank.) Unless I'm
mistaken the important thing about ballast is its contribution to the
location of the center of gravity (c.g.) of the whole vessel. Stability
or righting moment at any attitude of roll is determined by where the
c.g. is with respect to the center of buoyancy (c.b.) which in turn
depends on the geometry of whatever part of the boat is in the water
(preferably the hull!) and changes location with attitude as in
heeling. The c.g. also can change position with any change in weight or
location of crew, equipment, etc. In other words you cannot get the
whole picture considering only ballast.

I strongly recommend all of you Bolgeristas get "WoodenBoat" magazine
Number 114, September/October 1993, and read Mike O'Brien's article
`Shoal-Draft Sharpies' - Simple, self-righting, and roomy, starting
on page 64. Mike is a recognized authority on these subjects, and his
article gives loads of information on various sharpie design concepts,
components and performnce including several Bolger boats. There is more
good stuff on stability including "Surprising Stability Curves" of
Bruce Kirby's 31' Norwalk Islands Sharpie calculated by AeroHydro, Inc.
It is an excellent graphic explanation of c.g./ c.b. interaction. Look
carefully and you will even find mention of Martha Jane. Turn the page
and you will find PCB's article "A New (?) Tack for a Dipping Lug".
This issue is a short course education for all Bolger devotees. Enjoy!

If this is too long, at least it's free - and worth every penny. --John
Gerty