Is this a good Analogy?

Discussion in 'Boat Design' started by fritzdfk, Apr 10, 2018.

  1. fritzdfk
    Joined: Jul 2004
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    Location: Alaska

    fritzdfk Junior Member

    I have a 26' Allweather. If you are not familiar with this boat it is a round hulled displacement power boat. ALLWEATHERBOATS.COM http://allweatherboats.com/index.html
    We have had it for a year or so but the other day we got into some rough water and got broadside to the swells. I had been told that the boat rolls and it did. I wasn't too concerned but my wife had serious questions. I have read some theories about stability and tradeoffs in hull design. I explained to my wife that it is like the rockem sockem toys. These were (maybe still are) inflated figures with sand ballast that you can sock, push completely over etc and they come back up. Low initial stability high ultimate stability. Compare this with a tall rectangular box that might even have some ballast. High initial stability low ultimate stability. She was somewhat satisfied with this answer and she trusts me which I find amazing.
    Is there a better way to explain this?
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can roll and give with the onslaught of weather and sea state, or you can resist this movement. Guess which will win, in a long drawn out battle with mother nature. Simply put, it's a complex question to easily answer, but as a rule, you're just not going to beat mother nature, if she get's her hair in a tangle, so the more comfortable and survivable examples (boats), tend to work with her, when possible and fight when absolutely necessary. Can she ultimately get you? You're damn right she can, but most well founded yachts, prefer to roll with her punches, just to come up and take some more, rather then stand firm against the beating, while things break off all around you. It's a matter of how you look at things. Yeah, you can design her to stand tough, get whipped on repeatedly, but what will the crew have to survive, as she proves tough enough? The weak point of any design is how long can the crew, take this type of bashing, so the wise designer, sides on the weak kneed crew and lets the boat take a softer ride, to save or allow the crew to last as long as practical, mostly in hopes this will be long enough, for mother nature to have proved her point and blow herself out, providing you some time to rest and run for shelter.
     
  3. chinaseapirate

    chinaseapirate Previous Member

    Those were Weebles. Weebles wobble but don't fall down. That is a good anology to the Allweather 26'. Rockem sockem robots had manually controlled arms that that one tried to dislodge the opponents sprung head, popping it up into the air. The Allweather looks like a spruced up life boat. I'm sure it is supposed to be very sea worthy. You might want to customize the cockpit drains (larger- I don't see any), reinforce the "doorway" if possible, make it unsinkable with X-40, and buy survival suits for anyone who wants to survive before going to Alaska. I can imagine it being no more than a "buoy" in heavy weather. There is little or no reserve power in the engine being maxed out for mpg at 5knots. Nice rudder and keel though.
    Since it wasn't computer designed, nor built in a factory with politically correct minimum wage high school dropouts in HEPA lab conditions supervised by part-time kindergaten teachers(like Zodiac aerospace), I would expect a series of negative reviews to follow. If you want comfort for your wife "special order" one of these:

    Stock Photo - Bangka or traditional Philippino boat rests near shore while storm approaches Malapascua Island, Cebu, Philippines http://www.alamy.com/stock-photo-bangka-or-traditional-philippino-boat-rests-near-shore-while-storm-5511772.html

    your lucky your wife trusts you. mine pulled a knife on me the first thing I asked her to do when we got to shore after three weeks "at sea" in a craft similar to above. not a drop of water landed on board either. Good luck getting it onto a trailer or finding a dock for it though its possible.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Don't you just love the quote that is with the picture:

    ".....Bangka or traditional Philippino boat rests near shore while storm approaches Malapascua Island, Cebu, Philippines......"

    So, are you offering this as a boat as an example of when to not go out to sea when a storm approaches (which is what the OP is seeking help/advice on)...thus what is the point of this "seaworthy" boat if it can't put to sea when it blows up?
     

  5. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    The hull of the boat you have is strikingly similar to that of many older motorsurf boats that were used by Coast Guards and rescue agencies all over the world. Round bottom boats tend to roll a lot but if designed properly they roll only so far and then roll back up as you described. This is considered a soft ride, that is the boat rolls gently and doesn't whip backup to vertical rapidly. A soft ride is easier on the occupants. A hard ride can be really harsh and wear a person out quickly. I served on Coast Guard ships built in the 30's that had sort of round bottoms and rode very well. Newer ships have more square shaped hulls and really bash the crew around. The trade off is that the old ships weren't very fast, but they could power through even the worst weather. The newer ones are much faster but have to slow down in the slop and they take a real bashing. (stove in superstructure, bent rails and ladders, etc) Anyway your analogy was good. It reminds me of the inflatable punching bags that had weights in the bottom so you could hit them hard and they would always pop back up.
     
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