| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2085.1 | LOA or LOD?? | USCTR1::FLEISCHMANN | | Fri Sep 24 1993 12:37 | 5 |
| Alan, not sure what factors are being accounted for by LOA....if there
is a significant bowsprit, would LOD be more proper??
Tom
|
| 2085.2 | yes, use LOD | MASTR::BERENS | Alan Berens | Fri Sep 24 1993 13:08 | 7 |
| re .1:
Yes, certainly, I would assume that LOD (length on deck) would be
correct. LOD = LOA for those boats without bowsprits, boomkins,
windvanes, and other fore and/or aft appendages.
|
| 2085.3 | Can you clarify the formula a little? | NEWOA::NEALE | Who can, do - who can't, consult | Wed Oct 06 1993 09:42 | 16 |
| Alan,
Can you clarify the formula a little more, e.g. with the use of
plentiful brackets?
In particular, I cannot understand the point of the "0.65" factor, as
this just affects the overall value of an arbitrary figure, unless the
whole of the bottom line should be (....)**1.33. Always did have
problems with conventions about "operator precedence"!
I find it an interesting calculation in any case, and I have been using
it to compare several boats in which I am currently interested. In
other words, I think it's a great idea, as long as it agrees with my
own personal prejudices!
- Brian
|
| 2085.4 | this help? | MASTR::BERENS | Alan Berens | Wed Oct 06 1993 10:29 | 15 |
|
D
ratio = ------------------------------------------
0.65 * ((0.7*LWL) + (0.3*LOA)) * (B**1.33)
where D is the displacement
B the beam
LWL the length on the waterline
LOD the length on deck
The larger the ratio, the better.
I would assume that the factor 0.65 in the denominator is a (possibly
arbitrary) scaling factor. The multiplications in the denominator can be
done in any order.
|
| 2085.5 | | STARCH::HAGERMAN | Flames to /dev/null | Wed Oct 06 1993 14:45 | 4 |
| Did you see that thing in the paper a couple of days ago where a big
ship (the QE II?) did a very large roll and 50 people or something got
hurt, including Rolf Harris, famous Australian singer...
|
| 2085.6 | Heavy Rolling | SALEM::GILMAN | | Wed Oct 06 1993 16:49 | 15 |
| Determining the 'proper' amount of stability into a ships design is a
tough call. Too much stability and the ship will likely never roll
over but will be a snappy fast roller which tends to throw people and
equipment aorund. Passengers don't like being seasick or being thrown
around. On the other hand.... design an 'easy rider' and you have
reduced the vessels stability, she will roll nice and slowly and easily
UNLESS she rolls right on over, and passengers don't like THAT either.
Smile. U.S. liners tend to have higher metacentric heights because U.S.
design standards are stricter regarding stabilty safety margins.
European designs (which I assume the QE II is) tend to be less stable
and easier riders than U.S. ships. BUT, get synchronous rolling started
or that occasional rogue wave and we read about it in the papers. I
would take the U.S. ship anyday.
Jeff
|
| 2085.7 | Thanks for clarification | ESPO01::NEALE | Who can, do - who can't, consult | Thu Oct 07 1993 11:07 | 10 |
| Re: .4
Thanks, Alan. Still don't understand the 0.65 (arbitrary scaling factor in what
is anyway an arbitrary formula?) but so what!
Re: .5,.6
Anyone have the raw data to do the sums for the QE2 :-)?
- Brian
|
| 2085.8 | Rolling | SALEM::GILMAN | | Thu Oct 07 1993 14:51 | 22 |
| Wish I did have the raw data for the QE2. When was the last time you
heard of a passenger liner capsizing due to rough seas vs. due to
excess flooding?
Liners do tend to be top heavy though compared to many other ships such
as tankers for cargo ships.
Quite a number of liners have rolled due to fire fighting efforts and
flooding. The Normandie for one.
When in the Navy on the carrier Franklin D. Roosevelt we were operating
light because of a pending dry docking which made us top heavy. We got
rolling once in phase with the prevaling seas and I though we were
going to go right on over. Equipment was falling and sliding the length
of the ship (beam) as we rolled in seemingly ever increasing rolls,
until finally we broke out of phase and the rolling eased... but it was
SCARY.
I can imagine what it must have been like on the QE2 with a bunch of
'soft' passengers.
Jeff
|
| 2085.9 | | STARCH::HAGERMAN | Flames to /dev/null | Thu Oct 07 1993 15:21 | 3 |
| This formula doesn't take into consideration how high the center of
gravity is. A deep keel boat and a centerboard boat of the same
dimensions would not have the same motion characteristics.
|
| 2085.10 | Some Data | MEMIT::HO | | Fri Oct 08 1993 19:47 | 96 |
|
Here are calculations for some familiar craft:
QE2
displ 140,000,000.0 pounds RATIO 165.9
lwl 950.0 feet
loa 1,100.0 feet
beam 220.0 feet
LASER
displ 120.0 pounds RATIO 1.8
lwl 13.5 feet
loa 14.5 feet
beam 4.5 feet
C&C 34
displ 10,500.0 pounds RATIO 23.8
lwl 28.0 feet
loa 34.0 feet
beam 10.5 feet
SANTA CRUZ 70
displ 26,000.0 pounds RATIO 23.3
lwl 60.0 feet
loa 70.0 feet
beam 12.0 feet
J24
displ 3,000.0 pounds RATIO 12.2
lwl 21.0 feet
loa 24.0 feet
beam 8.5 feet
ETCHELLS
displ 3,400.0 pounds RATIO 17.7
lwl 22.0 feet
loa 30.5 feet
beam 6.5 feet
TOYOTA COROLLA
displ 2,500.0 pounds RATIO 19.9
lwl 16.0 feet
loa 16.0 feet
beam 6.5 feet
HINCKLEY B40
displ 20,000.0 pounds RATIO 40.1
lwl 28.0 feet
loa 40.0 feet
beam 11.0 feet
SHIELDS
displ 7,500.0 pounds RATIO 41.6
lwl 20.0 feet
loa 30.0 feet
beam 6.5 feet
12 METER
displ 70,000.0 pounds RATIO 65.2
lwl 50.0 feet
loa 65.0 feet
beam 13.0 feet
MACK TRACTOR TRAILER TRUCK
displ 45,000.0 pounds RATIO 62.2
lwl 70.0 feet
loa 70.0 feet
beam 8.0 feet
From the above we can draw the following scientific conclusions:
1. The QE2 is more comfortable than a Laser.
2. A Santa Cruz 70 and a C&C 34 will get you equally sick but
you'll get over it faster in the SC70.
3. A Toyota Corolla is more comfortable than an Etchells and both are
better than a J24.
4. You can be as comfortable sailing to Bermuda in a Shields as in a
Hinckley.
5. A 12 meter and a Mack Truck are equally good sailors.
A rigorous analysis of the variables in the formula reveals that more
displacement is good and more lwl, loa, and beam are bad.
Displacement is what causes a boat to sink.
LWL, LOA, and beam are what cause a boat to float.
Therefore, the most comfortable boat is the one most likely to sink.
|
| 2085.11 | Never call starboard on a Mack from a Toyota | MILKWY::WAGNER | Scott | Mon Oct 11 1993 12:15 | 14 |
|
I sunk my rowboat, which displaces less than my Zodiac...
Great analyses Gene! Now what tank did you get the DWL of the Mack
truck?
I was never more sick than on an old Bristol 40. The waves were
just right for hobbyhorsing and yanking any flow away from the
sails.
I think, like comparing IMS and PHRF rules, the more data, properly
applied, the better.
Scott_who_gets_blinded_with_Science
|