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17-01-2014, 05:30
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#226
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Registered User
Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,108
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by sigmasailor
Thick walled pipe of the same weight is stronger than solid bar. Most of the load will occur in the outer fibers of a shaft. The farther away these are from the neutral line (the center) the stronger the pipe gets. Compare this with oversized tubes on bicycles. Strength increases by at least the square (close to cubed) of the diameter. I know of similar sized cats with 70 mm rudder shafts.
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All you say is true. However, 1.5" tube is weaker than 1.5" solid stock. Your point is that when they weigh the same, the tube is stronger. By that time, the tube is also 2-3 times larger diameter!
Mark
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www.svreach.com
You do not need a parachute to skydive. You only need a parachute to skydive twice.
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17-01-2014, 05:33
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#227
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Registered User
Join Date: Jan 2012
Location: Yuma Island
Posts: 1,579
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Oh, where oh where is Mario Vittone?
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17-01-2014, 05:39
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#228
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Registered User
Join Date: Jan 2010
Location: Netherlands, Holland
Boat: Sold Sigma 33 OOD some time ago, will be chartering in Turkey really soon
Posts: 361
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
That's my point exactly! Strength can best be found in diamater. The material in the middle of a bar gives very little resistance against bending since it is so close to the neutral line and can be put to better use at the outside diameter of a pipe.
If I could choose I would prefer a 3 inch pipe above 1.5 inch bar stock (at the same weight) anytime. I realise there are more variables like rudder thickness.
__________________
Sailors do it with the wind...
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17-01-2014, 05:44
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#229
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Registered User
Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,108
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by Southern Star
I had suggested the possibility of a rogue wave driving the boat back so that the rudders were not only damaged, but bent at an acute angle making it impossible to steer the boat. This now seems to be the case, if one accepts the word of the captain (and I do). Yes, Yeloya is correct that running the starboard engine would only push the boat further to port - rather obvious and hardly a mistake that a captain with the experience of Captain Schmitt would make and not realize over several days. Surely it is far more likely that he misspoke.
One can scoff at the notion of a rogue wave, but they exist and in greater numbers than had previously been thought. Remember, in 2004 European Space Agency satellite images were used by scientists for three weeks to study the phenomenon and in that short period they were able to pick up 10 rogues that were 82 feet or higher! Remember, a rogue is defined as being AT LEAST 2 time the significant wave height (rather than just the mean). The scientists were also able to confirm that they occur on every ocean on the planet.
Certainly, to drive a boat backwards that has forward momentum and 18,000 lbs displacement would take a very large and powerful wave. Would other rudders have survived this event? Possibly, but unless someone has evidence that the rudder stock on most cats of this size are substantially stronger, I would be hesitant to call it a design or construction flaw.
Is it surprising that the rig would have survived this event? Not unless the boat did a backwards pitchpole - something which has happened to boats encountering rogue waves in the past, but which blessedly did not occur here.
The captain indicates that the diesels were functioning after the event - but again, with the boat only able to go in circles, they were of no more use than the sails. After a few days at the mercy of the waves in a disabled boat in a very cold North Atlantic, what were they to do with a forcast for worsening conditions? Wait until they were at imminent risk and rescue might be impossible? IMO that would have been irresponsible.
Brad
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It is the damn spin that gets to me. I would believe in a rogue wave if they were not also trying to sell me on the boat traveling 8kts at the time when they were suddenly stopped dead and " violently" thrown backwards. AND, they " never felt like they were in imminent danger". Maybe I'm a wimp, but I would have browned my pants and suffered whiplash if our boat encountered a wave rogue enough to stop it dead from 8kts and throw it violently backwards.
Mark
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www.svreach.com
You do not need a parachute to skydive. You only need a parachute to skydive twice.
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17-01-2014, 05:45
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#230
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Registered User
Join Date: Aug 2013
Location: Warwick RI
Boat: Catalina 30
Posts: 1,873
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by Cotemar
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NOOOOOOO I didn't make the top 3 . At least I had the pleasure of being nominated. I would like to thank my family, all of my friends that have supported me, and of course God for this opportunity. Next time around I promise I will try harder to get a medal
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-Si Vis Pacem Parabellum
-Molon Labe
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17-01-2014, 05:46
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#231
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Registered User
Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,108
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by sigmasailor
That's my point exactly! Strength can best be found in diamater. The material in the middle of a bar gives very little resistance against bending since it is so close to the neutral line and can be put to better use at the outside diameter of a pipe.
If I could choose I would prefer a 3 inch pipe above 1.5 inch bar stock (at the same weight) anytime. I realise there are more variables like rudder thickness.
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OK, we agree! Now, do you think 1.5" tube is appropriate as rudder stock on a 42' 20,000lb boat? If so, do you think it is also "massive", like Tarjan does?
Mark
__________________
www.svreach.com
You do not need a parachute to skydive. You only need a parachute to skydive twice.
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17-01-2014, 05:48
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#232
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Moderator Emeritus
Join Date: May 2008
Location: Fort Lauderdale, FL
Boat: 48 Wauquiez Pilot Saloon
Posts: 5,975
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
After days of watching the thread I finally have to pipe in... (bos'n if you please....)
Obviously Tarjan and Aero have HUNDREDS OF THOUSANDS OF HOURS... designing, building, and commissioning highly successful yachts.... I wish them and everybody else nothing but complete success in furthering the industry which we all love....
BUT as been previously ponted out.... (especially by Mark=colemj)
"It should be noted that the rudders of the boat were built of massive 1.5 inch solid stainless round tube welded to a closed framework of 2″ wide by 1/4″ thick stainless bars with (2) vertical and (3) horizontal members. Unfortunately no rudder is designed to suddenly lurch into reverse and have 10 Tons of torque applied to them."
My NON-MASSIVE 22 footer has 1-1/2" tube rudderstock... My 34k displacement boat, 3" solid stock....
I'm no naval architect.... but I AM a mechanical engineer.... I do understand bending moments and MOI (moment of inertia) of roundy thingys very well....
IMHO..... ridiculously undersized
Fix it and let the people who love ugly boats sail them well into the future!
__________________
In the harsh marine environment, something is always in need of repair...
Mai Tai's fix everything...
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17-01-2014, 06:02
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#233
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Registered User
Join Date: Jan 2010
Location: Netherlands, Holland
Boat: Sold Sigma 33 OOD some time ago, will be chartering in Turkey really soon
Posts: 361
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by colemj
OK, we agree! Now, do you think 1.5" tube is appropriate as rudder stock on a 42' 20,000lb boat? If so, do you think it is also "massive", like Tarjan does?
Mark
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I think massive (Dutch 'massief' stands for solid) would mean solid and it probably is. I think it is not massive in relation to the weight and size of this cat. As I said earlier (did I?) I have seen similar sized boats with 3 inch (70 mm) stocks. I would say there is room for improvement. I also say that nothing is completely bullet proof.
I used to own a 33ft Sigma 33 OOD; have looked it up; the rudder stock on that boat (9000 pounds) was close to 2 inch (45 mm). Rule 6.2: http://homepage.eircom.net/~bowringd...gn%20Rules.doc
__________________
Sailors do it with the wind...
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17-01-2014, 06:14
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#234
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CF Adviser
Join Date: Dec 2007
Location: Wherever our boat is; Playa Zaragoza, Isla Margarita
Boat: 1994 Solaris Sunstream 40
Posts: 2,449
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Thanks to those with experience in terms of rudder stock - so it is beginning to sound as if those on the Alpha 42 may have been undersized (albeit the individual rudders on a cat are smaller than those on monohull).
Brad
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17-01-2014, 06:35
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#235
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Moderator Emeritus
Join Date: May 2008
Location: Fort Lauderdale, FL
Boat: 48 Wauquiez Pilot Saloon
Posts: 5,975
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by Southern Star
Thanks to those with experience in terms of rudder stock - so it is beginning to sound as if those on the Alpha 42 may have been undersized (albeit the individual rudders on a cat are smaller than those on monohull).
Brad
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This is the caveat about not being a naval architect!
Could I make a rudder from scratch that would point the pointy end the direction I wanted to point?
You Bet!
Could I design one with optimal balance for the hull form, sail plan, keel wash, and acceptable helm effort on the first go???
Uh... Maybe on design revision #23 or so....
__________________
In the harsh marine environment, something is always in need of repair...
Mai Tai's fix everything...
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17-01-2014, 07:01
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#236
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Resin Head
Join Date: Aug 2007
Location: Seattle WA
Boat: Nauticat
Posts: 7,205
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by Doe818
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Ridiculously undersized indeed. This is what happens when you are so concerned about weight that you build everything undersized. No margin of error for safety. It's the ocean, everything should be built oversized instead.
Five guys to install a teeny tiny rudder like that? How many are on the inside? No wonder the damn thing costs so much! If I was the foreman in this yard, these guys would meet the ogre! This is a two man job, one out, one in. New Yorkers. What a terrible place to build a boat...
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O you who turn the wheel and look to windward,
Consider Phlebas, who was once handsome and tall as you.
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17-01-2014, 07:29
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#238
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Moderator Emeritus
Join Date: May 2008
Location: Fort Lauderdale, FL
Boat: 48 Wauquiez Pilot Saloon
Posts: 5,975
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by minaret
Ridiculously undersized indeed. This is what happens when you are so concerned about weight that you build everything undersized. No margin of error for safety. It's the ocean, everything should be built oversized instead.
Five guys to install a teeny tiny rudder like that? How many are on the inside? No wonder the damn thing costs so much! If I was the foreman in this yard, these guys would meet the ogre! This is a two man job, one out, one in. New Yorkers. What a terrible place to build a boat...
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Standard FS (factor of safety) in design is 1.5 to 2.... lemme run calculations on 1-1/2" SS tube and rod....
Looks like there is room for 2 guys to guide the shaft inside the hull, probably two more at the top bearing with parts... and one deck super...
So my guess is 10 guys total....
__________________
In the harsh marine environment, something is always in need of repair...
Mai Tai's fix everything...
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17-01-2014, 07:36
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#239
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Registered User
Join Date: Dec 2009
Boat: JBW club 420, MFG Bandit, Snark
Posts: 871
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It looks nearly identical to this FP rudder and stock. This rudder got damaged while the boat was towed off some rocks. The stock was not bent.
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I love big boats and I can not lie.
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17-01-2014, 07:50
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#240
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Moderator Emeritus
Join Date: May 2008
Location: Fort Lauderdale, FL
Boat: 48 Wauquiez Pilot Saloon
Posts: 5,975
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re: Alpha 42 "Be Good Too" rescue 300 miles off Cape Henry Merged
Quote:
Originally Posted by Fiveslide
It looks nearly identical to this FP rudder and stock. This rudder got damaged while the boat was towed off some rocks. The stock was not bent.
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Gawwwwd... You guys are right.... Multi blades are tiny!!!
Those are standard building bricks holding it up right????
__________________
In the harsh marine environment, something is always in need of repair...
Mai Tai's fix everything...
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