Help with listing stability.

Discussion in 'Stability' started by bakeefe4, Aug 26, 2014.

  1. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The boat in question is more a novelty item than a practical one, though I don't know it is inherently a menace, if restricted to quiet backwaters, any more than other small boats of similar size. If all that superstructure encourages people to brace against it, that is no good. Keep the crew weight down, and all seated at all times ! You could install a bouyancy collar along each side, for peace of mind. Like this:

    http://www.kaptenboatcollar.com/
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You're absolutely correct, I should ignore the obvious and not worry about the 3 teenagers aboard (as an example afternoon outing), with you at the helm, all sitting per your instructions, when a pink something or other happens to appear to starboard, attracting their attention. Naturally, they all jump up, run to starboard, just as you cross a beam sea wave train, maybe some of them climbing up on the starboard seat box, for a better vantage point. Yeah, whats the harm in swimming around, as you watch the engine, drag that non-floatation equipped contrivance to the bottom of the puddle you've capsized in. I've investigated way too many "incidents" to let you off without the warning. I joined this thread, after you seemingly cast aside the physics and science behind some concerns, thinking maybe a good slap might do. Now, it's in your hands, so spare me the attempts at a guilt trip, I've been part of too many "recovery" operations, to allow a misplaced decision justification, to cloud the obvious issues associated with your little jem.
     
  3. bakeefe4
    Joined: Aug 2014
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    bakeefe4 Junior Member

    Dear Mr. PAR, your attempt at a warning was not taken as a warning. The other people here did not insult but to spell out the physics. You came off as very conceding and smug. Now it looks like an attempt at acting like a victim and injured. Not only that lets see you are a designer, bolder home demolition, boat accident investigator, and a meme er of search and rescue. Talk about wearing many hats. That is ok. I understand your need to be superior. It doesn't lm after what you or say you will always defend your actions. The truth most likely is if this was an open public arena where you could be seen you would either say nothing or come across a bit less arrogant. I do thank you for you concern.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The emotions and attitude you've injected into my posts, are purely self generated and considering this rather sterile and seemingly impersonal presentation, can be easily misinterpreted into something it wasn't intended to be. This isn't uncommon with discussion forums and with the occasional exception, I think you'll find my posts are careful about this, with this thread being an exception. In person, you'd find my voice inflection and facial expression as a guide, to intent of the comments and I'll still be as bold, though the tongue in cheek and off hand comments, would be immediately disarming with an observed smile. In fact, you'd probably smile and laugh, as others might in a similar situation. It's difficult to convey these things in this format.

    Lets try again. Yes, I've been involved in recover operations, though never as a search and rescue swimmer or other USCG or Navy personal. When at sea, it's everyone's responsibility to perform these tasks, a commonly accepted duty, simply because next time, it might be you they're looking for. In our state, we're much more likely to find this type of situation. We have more boating deaths than any other, for some obvious, other less so reasons. Yep, I've repaired homes too, often my own, typically investment properties I'm looking to roll over, after bringing them up to snuff. Sorry about the mis-ID on the pool hose, though it does look just like larger gauge Smurf and an easy to understand mistake. Though in my defense, pool hose still wouldn't be a good rub rail material. Yes, I investigate accidents for a large insurance company and also perform survey work for them as well. In fact in this area, there are only two guys qualified to make certain surveys on certain types of boats, and I'm one of them. Ft. Myers is in my overlapping range of influence. I don't expect I'll survey your little boat, though if it was involved in an "incident", I might very well be the guy on the scene talking with the claims adjuster and other authorities. I discovered diversification in the early 90's as the best way to avoid economic changes in the industry, so when one aspect falls flat, I can rely on another to keep up with the mortgage, so yeah, lots of hats.

    The stability issues raised by some of the professionals and in regard to some of your suggested modifications, should be understood, in spite of my poking fun at your boat. Simply put, a boat of that volume and shape requires the skipper and guests remain low (seated) and no sudden movements, particularly in unison. If you take it out by yourself, sure you can stand at the helm and drive, though I'll bet you find you're standing more on the centerline then directly behind the wheel, just to keep her tracking straight instead of naturally turning right. This is common of all boats of this general arrangement, not just yours.

    Modest volume, flat bottoms, such as sharpies and small skiffs (like your boat) have fairly high initial stability, much like a catamaran, but this goes away very quickly (demonstrated by a graph posted previously) and this can lead to capsize or swamping. The access door on the port side, having an opening just a few inches above the LWL, is a major concern too. This boat is just way to small to require this feature. Now I realize that the designer/builder might have needed this access, given his age, but you'd be best advised to seal it closed. The very last thing you'd want to do to this puppy (read smiling) is raise the sole (floor) as this would have quite an adverse affect on her stability. Now you could put a box keel on her, which would increase her draft a bit, but it would also supply the boat with more volume and if this volume was ballasted, maybe with water, possibly a route to explore, though should be worked out by someone with a good grasp of the shapes and centers involved in this type of modification.

    To most of us, it's a "Dolly Parton" - 5 pounds of boob in a 2 pound bra (look for the smile again). She's too small for her configuration and intended use, which leads to several concerns, particularly by old farts (like me) who've seen this too often over the decades and would prefer not to see any more injuries (or worse) of folks the age of our grandkids. Lastly my apologies for any perceived personal insults, they weren't intend to be taken as seriously as I think you may have (my assumption).
     
  5. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    One thing that does concern me apart from the issues raised by PAR is the outboard mounting. It looks as if the motor is mounted/clamped direct to the 1/2"(?) plywood transom. This is not good practice and far too weak even for a modest 4HP engine. If you look at almost any small boat - skiff, RIB, dinghy etc you will note a pad approximately 1 1/2" thick to spread the load. Not only that, but the load and thrust of the motor is further spread to the structure of the boat ie into the transom corners, maybe the floor, partly dependent on design.

    With the weakness from the port side hinging opening (which acts as a notch for stress) and a thin mount thickness that is not well supported, I would be concerned that the motor may cause further problems. It is not clear from the photos if this is the case, but if so it would be wise to ensure sufficient strength.
     
  6. bakeefe4
    Joined: Aug 2014
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    bakeefe4 Junior Member

    Transom is a full 1 3/4 thick from notch point on the mount to the floor and the access boor is locked off and sucure when in the water it is only for access while on the trailer. It is also fully supported and braced.
     
  7. bakeefe4
    Joined: Aug 2014
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    bakeefe4 Junior Member

    Par sorry I didn't get back to you sooner it has been very hectic at work.... I do want to say sorry I took you wrong. I do understand what it is your concerns are and that is one of the reasons I was seeking advice to increase the stability of the craft with out totaly taking away from the work a friend did before passing. Also this is not something that will be used on the open sea. I mainly was looking to just a bit more stable in the waters that are not perfect glass.
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Improving stability will require you lower the CG, add to the beam or both. I think the wisest thing would be to add a ballasted box keel. Bolger was fond of this tactic on small craft. It's essentially a streamlined box shape, attached to the bottom of the boat that can be filled with or automatically fills with water. Water is a lousy ballast material, but there's a lot of it available under a boat. For a boat of this size, you might be able to get 300 or 400 pounds of ballast in a box. This would do two things first is to lower the CG, but second, would add to the hulls immersed volume, so you can justify the weight increase with the offsetting volume.

    What are the WOT and cruise speeds for this boat now? Do you have an idea on how much she weighs with the engine and tank aboard? Assuming a 10% slip, 800 pound load (boat, it's equipment and skipper) and a conservative "constant", you should do in the mid teens (MPH) range on that 6 HP outboard. With much more load, you'll have trouble maintaining or getting up on plane, without more HP.
     
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    You could buy a used jon boat and install the existing motor.
     
  10. JSL
    Joined: Nov 2012
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    JSL Senior Member

    an unfortunate situation.
    I have seen 'boats' like this in kiddies playgrounds but I can see a lot of changes needed before this 'boat' could be donated.
     
  11. gonzo
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    gonzo Senior Member

    Planter?
     
  12. boatbuilder41
    Joined: Feb 2013
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    boatbuilder41 Senior Member

    He may have been a little harsh about it... But when it comes to the safety of your kids and others around you...nothing could be to harsh.... I live every day with the loss of a child. And I would rather have someone stomp on my pride than to have it happen to anybody.... Just appreciate that there is people out there who do care more about the safety of others. You asked for an opinion ... And you got the best opinion possible from a verry educated professional. Just remember. You asked for it..... Sorry you didnt hear what you wanted to.... I would burn it myself before I let my children set sail in it.
     

  13. Nick_Sinev
    Joined: Aug 2014
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    Location: Sydney

    Nick_Sinev Junior Member

    I'm not a naval architect, my opinion could be a mistake.

    According to the dimensions of the boat, the boat is supposed to be extremely stable.
    Compare, e.g., with this boat, considered to be successful
    [​IMG]
    picture from http://www.katera-lodki.su/shema.html
    (I just googled something with approx. the same dimensions.)

    In reality, your boat is not stable. So, you need to understand why it happens.

    Yes, the problem could be solved.
    Possible variants.

    1) Water ballast (yes, it will work)
    2) Unremovable ballast.
    3) Cut off the top of the boat.
    4) Something else. E.g. you can add bouyancy blocks and do not care about high angles of list.

    Before doing anything it is reasonable.

    1) To eavaluate the weight of the boat.
    I.e. empty boat + outboard motor + supposed weight of the crew.

    2) To evaluate the height of the centre of gravity.
    You need to find a site with a flat surface and to heel the boat. You need to find the angle when the boat is balancing on its chine.
     
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