requirements to avoid ANY hurricane (at a given speed vs warning time)

Discussion in 'Boat Design' started by black_sails, Sep 8, 2017.

  1. black_sails
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    black_sails Junior Member

    For obvious reasons of whats in the news right now my mind has been wandering on this topic...

    There's always two strategies to survive through bad weather - be tough enough to get through it or have enough advance warning and performance to go around it. I'd consider the latter strategy to be prudent since even if a boat can survive bad weather you'll be pretty unhappy trying.

    Considering a "Worst case Category 6 hurricane" of the largest sizes ever seen, growing from a nothing blip on the radar as fast as has been witnessed in the past and moving as fast as has ever been seen... ie "the perfect storm", whats the minimum sustained speed combined with warning time that could let you safely avoid boat and sanity destroying conditions? Like if you moved fast enough but still hit an outer ring of Force 7 that's probably a rough ride but with a decent sized boat you shouldn't die - that counts as escaping.

    Since an 8 knot trawler isn't escaping anything lets just assume a couple of rough category speeds:

    20 knots
    30 knots
    40 knots
    50 knots

    Assume each boat can maintain that speed for at least 500 miles with no problem (allowing port hopping to gas and go) or even more (if it radically changes things to be able to go 1000 or even 2000 miles, and that gives more options like not going along the coast that's fine too) when does it start to become possible to hear a warning you're concerned about on weather reports far enough ahead of time, to set a course and avoid a 'perfect storm' worst case hurricane?
     
  2. Ike
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    Ike Senior Member

    Actually it is easier to survive hurricane offshore than near shore. That's why ships put to sea at the approach of a Hurricane. In 1967 I was in GITMO on a Coast Guard Cutter when Hurricane Beulah came through (sept 1967, worst Hurricane of the year, did lots of damage to Brownsville Texas.) The fleet that was in Gitmo went to sea to the west and rode out the storm. We were slower so we went south into the lee of Jamaica. Jamaica blocked the brunt of it.
    In 1974 rode out another one off Cape Hatteras. Don't remember the name. We had to stay where we were. The eye went right over us. It ripped a ladder off the gun mount and took the gangway (which was lashed down on the deck) over the side. Nasty but we survived. Those ships could do 19 knots max on a flat calm day with a tailwind. So we just pointed the bow into the waves and gave it enough to keep it moving slowly ahead.

    Hurricanes may have high winds but they don't move that fast over the ground, and a fast ship or boat can run away from it if you have adequate warning and know it's predicted path.
     
  3. black_sails
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    black_sails Junior Member

    How scary do the sea states get though? Is that notably less intense or substantially out at sea than along the coastline, I mean enough that I would want to be aiming in any way towards it (whether straight at it or 45 degree angle for instance, as opposed to a beeline north or south trying to get past the expected landing path)? How far out does one have to be from the coast to diminish the severity and by how much?

    I'm spending a little time perusing thru "list of atlantic hurricane records" and see lots of scary facts. For rate of increasing intensity, from 35mph to 85mph winds in about 12 hours. (and to 180mph winds in 24 hours), some moving as much as 60-70mph, the largest nearly 1000 miles in diameter. I'm not sure what the speeds are at the outer rim of that but it makes me think 500 miles in one direction is theoretically the minimum safe distance from the largest. (as long as it doesn't steer towards where you decided to set out going anyways) Meaning taking off at 20-50 knots for 10-25 hours (inversely proportional to speed) could be necessary to avoid the worst cases. Yet even that could require more if the hurricane was heading straight for you when you turned one direction and starts steering in your direction! (i'm not sure what the maximum rate of observed trajectory change has ever been, hard to find a recorded listing for that, but even guesstimates would be welcome.. how reliable are those trajectory predictions and whats the worst it's ever been off or had to be revised in the past?)

    Yet as you said, instead of sticking to the coast what if it's better to meet things more in the ocean, if you're mostly trying to minimize the sea state the vessel experiences (because maybe it's not the strongest in the world or you fear what the ride will be like) what are the options and what would the best strategy be? Would others here "just head due north/due south" or "head straight for the eye" or "go off at an angle"?
     
  4. PAR
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    PAR Yacht Designer/Builder

    The basic difficulty is prediction. Now, we've gotten pretty good at it, but I've been caught running and have had them roll over me, in spite of predicted routes.

    Ike is correct in that you need to be well off shore to have the room to run and you need to have the speed to make this a wise decision. Most displacement mode vessels simply can't out run one, without a significant lead time in warning, which by it's nature is difficult. I saw a story about a news cameraman that filmed the aftermath of Harvey. He'd taken a needed and previously well planned vacation, sailing in the leeward islands. He was now stuck in a hotel, without power or a roof. Sad coincidence or a fool that planned a sailboat vacation in hurricane season?

    In the end, you can't beat mother nature, as she has a nasty habit of teaching you why this is true. This leaves preparation and respect. I have two large boats (40' and 65') in berths on the east coast, with few worries I'll need to claim a total lose next week. I might have some damage, but I'm safe. This isn't my first rodeo, so I've prepared them for the event.

    FWIW, there's only 5 hurricane categories, though this one at times could have been classed a 6, if the scale went that high. We get these types of questions occasionally, but in reality, you can't design a boat that will survive every eventuality. As a rule you establish what you need, add typical storms and weather implications to this and accept you're not sailing a Nimitz class, so adopt appropriate precautions. This might seem callous, but it's just too costly to consider what you'd have, if every eventuality was covered. Building codes in my area are some of the toughest in the country, as a result of lessons learned in Andrew, but wind loads are still about 120 -130 MPH on say a garage door design. Yeah it could be built to 150 or 170 MPH loads, but it would cost twice as much, simply because of physics. Practicality just has to step in, as well as preparation and an acceptance of reality, unless of course, you can afford a Nimitz class . . .
     
  5. black_sails
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    black_sails Junior Member

    I understand all that, and i'm mostly curious whether 30 knots or even 20 knots is fast enough to "plan a reasonable escape" as things get closer, and whether my instinct to go due north or south would be wrong.

    I'm aware there's only 5, but some people are saying there should be a class 6/extrapolating the current system out. I wanted to be clear "worst possible ever" mostly.

    Practicality and cost will always be issues, but just like one strategy is "design it to survive Force 12 conditions" another is "plan to run" and I was wondering what the logistics of that would be. I'd think something doing 40 knots for 500 miles could darn near get out ahead of anything but that's a tall order, i'm more curious if it's still as feasible with 'only' 20-30 knot capable craft I guess.
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    VERY...!!!!!

    Just hope you never have to sail through one...
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    If you're in it's path, don't forget to put a brick in each pocket if you go outside your house.
     
  8. tom28571
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    tom28571 Senior Member

    If you have ever actually looked up at 40 to 50 foot wave walls in the open sea in a cyclone, you know that the only really safe decision is to not be there. As for the in port/at sea argument, I would prefer for the boat to be well secured in port and me on dry land. My personal experience was in the Pacific with no prior outside warning, only what could be gleaned from aboard the ship. My main advantage at the time was youth and ignorance of possible consequences plus good luck as well as the competence of others charged with operating the vessel. I have little regard for those who moan about the incompetence of the National Weather Service and their early warnings. Weather prediction is becoming increasingly more accurate in storm direction, severity and coverage. Irma is a very good illustration of their abilities to see the path ahead and make warnings more and more accurate with each new report.

    Current cutting of the budget of the NWS as well as many other agencies useful to the general population is shortsighted in the extreme. I notice that both Senators of TX who voted against aid for NJ for hurricane Sandy relief are now vocal in promising aid for their constituents.
     
  9. PAR
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    PAR Yacht Designer/Builder

    Yeah, you need to understand, it's not enough to outrun one. The boat has to tolerate the sea state, which will be bad (real bad) and then there's the fatigue factor, which you can never outrun. I just don't think you understand what you're asking for. Can a moderate size yacht be designed to tolerate a Cat. 5, yeah, but it'll be a slug on every other occasion you might have her out. This is the point I tried to raise previously, you just can't design for every eventuality, at some point common sense and seamanship will need to help. I've sailed through a number of hurricanes and trust me, this isn't something you want to do. Their paths are unpredictable and even if your boat is fast, you'll be flying off 20' swells at 30 knots (actually you'll only do this once or twice), which isn't going to last long for you, the crew or the boat.

    I remember leaving Norfolk, because a Hurricane was coming up the coast (early 70's). I saw the navy packup the big boys and head to sea, so I figured to do the same. Unfortunately, they could go a lot faster than I and worse, we all headed east into deep Atlantic water, while the storm was supposed to head inland and peter out. Naturally, my luck prevailed and she made a right hand turn and rolled right over me. Me and a nearby container ship rolled from rail to rail, for a day. I'm not kidding this puppy dumped containers over the side more than once and rolled from starboard gunnel to port, every 5 or 6 seconds. I did the same though my motion was a bit faster. I tried to contact them, but my radio was down and I was left with a handheld that had very little range. I could hear them occasionally, but then they'd roll away or I would and the signal was lost. Eventually, after about 30 hours of an *** whooping, I raised them up. She was Liberian, with a Portuguese crew and a Japanese skipper. Between my pigeon Italian, the skipper's pigeon Spanish, though the who knows what heritage cookie, we figured out who was who and how bad off we were. I lost most of my most of my rig and had to motor home under a jury rig. They took a few days to get both engines firing properly and repairs to their decks and hoisting gear.

    This wasn't a Cat. 5, but a Cat. 1, trying its best to die into a tropical depression. The point is, even a Nimitz class will sea some damage in a Cat. 5, so you don't want any part of anything smaller in one, even if you could afford to have one built. If you want to get an idea of the "condisions" you might have to experence, rent or borrow an inflatable raft, no engine, just some oars. Go down to the local beach and see how long you can keep your lunch down, while rowing in the shoreside surf. Now imagine a full day or two of this and you get somewhat close.
     
  10. JSL
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    JSL Senior Member

    Some years ago on a run from Hawaii to Victoria,BC we ended up on the rim of a North Pacific typhoon. We knew something was 'up' but could not get a proper weather report. The barometer was dropping about 1/10"/hour and the waves got larger by the hour. The entire 'ride' lasted about 2-3 days and we estimated the waves as high as our boat length (60-65'- we guessed) and winds to about 85 to 95 knots (they read 75 kn. + until the anemometer blew away).
    I doubt that you could build a boat fast,or strong, or habitable, enough to avoid a hurricane.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    There are few excuses these days to be caught out in extreme weather, forecasting has become much more reliable, and warnings aplenty is the rule.
     
  12. jorgepease
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    jorgepease Senior Member

    They pretty much follow the same route ... This is 150 years of hurricane tracks in the Atlantic, I wouldn't plan on trying to outrun it for thousands of miles, they don't zigzag much, and these days with the software models they can create, it's very accurate 3-5 days out. Given their size and influence on surrounding seas, I would plan to give them wide berth and not rely on fast evasive actions.
    hurTrack.jpg
     
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  13. Ike
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    Ike Senior Member

    Conditions? Pretty damn Scary. In the hurricane off Cape Hatteras we we taking breaking waves over the flying bridge which is about 80 feet above the waterline. Of course those old Coast Guard ships (327 feet built in the late 30's) were built for taking a beating in the North Atlantic, but still, the boat is not the limiting factor. You Are. I have lost count of the times the Coast Guard lifted people off a boat because the occupant(s)were taking a beating, and then the boat was found a month later doing just fine. Humans are not built to withstand that kind of thing. The best way to avoid a hurricane is be somewhere else during the season.

    We used to talk about the safe quadrant, and dangerous quadrant. Total BS in a cat 4 or 5 hurricane. It's all dangerous. Even large ships have had serious damage in hurricanes. Frankly I'd prefer to be in a ship like that old cutter rather than one of those big cruise ships with a huge amount of sail area and top hammer. Even the Nimitz would have some serious difficulties in that kind of sea state. (I have a good friend who is a Master Chief on the Nimitz).
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    Of course large ships are not immune, the US Navy prioritized accurate weather forecasting after the experience of WW2, where losses from dangerous weather systems at times exceeded battle damage.
     

  15. philSweet
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    philSweet Senior Member

    A more reasonable and useful range of speeds would be 2kn, 3kn, 4kn etc. up to about 8kts. When I need to get out of the way of weather, I also need to catch up on sleep. So I will rig for heavy weather self tending and go crash until the worst of it hits. That means about 2-3 knots in 35kt wind and building. Yes, you can navigate around stuff at those speeds. Maybe not the coast of North America, but you can escape getting pinched in the Caribbean and Gulf of Mexico. You need to consider the wave field these things produce. I've seen waves at 12-16' in the Caribbean for a continuous month, and I don't even know where that storm was. Nobody went anywhere at more than 4 knots in anything.
     
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