Extra buoyance

Discussion in 'Sailboats' started by BertKu, Jul 8, 2016.

  1. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Hi there,

    I need to add some more buoyance to my boat and consider to use an amount of small table tennis balls mixed with the 2 component expandable foam which expands 20 times. Somebody mentioned I should use a number 2 liter plastic coke bottles. What are your views.
    Many thanks
    Bert
     
  2. gonzo
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    gonzo Senior Member

    It depends on the location and what conditions it operates in. For example, if there is any load on the floatation, coke bottles are not a good idea because they will collapse. Ping pong balls would be better. However, you don't need foam for reserve flotation. Inflatable bags do the job too.
     
  3. TANSL
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    TANSL Senior Member

    By adding things inside compartment not more buoyancy is achieved. Buoyancy compartment is what it is and can not be changed. What you can do is try to prevent water from entering the compartment. To do this, you must fill it with a material that is lightweight and as compact as possible. Table tennis balls seem OK.
    The best, from my point of view, placing a balloon, sufficiently rigid wall, which perfectly suits the compartment shape.
     
    Last edited: Jul 11, 2016
  4. BertKu
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    BertKu Senior Member

    Hi Gonzo, yes indeed. I could thus even use 5 liter inflatable wine bags. They are quite strong and easy to fill. The reason why I want to fill it with foam, when I hit a leak, I loose immediately quite a lot of buoyance. They are my 2 extensions I build onto my transom. My solar panels are mounted on the extension. By filling them, I may lose a liter when hit a leak, but that is all.
    thanks for your reply.
     
  5. BertKu
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    BertKu Senior Member

    Thanks Tansl, as explained to Gonzo, it is my two x 86 liter extensions I have build onto my transom to hold the solar panels. Should I hit a leak, my bow will go higher up, well that is what I have calculated. By filling them with either table tennis balls and foam, I am better off. Thanks Bert
     
  6. PAR
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    PAR Yacht Designer/Builder

    Ping pong balls are a relatively heavy way prevent water intrusion. Just skip all the contrivance ideas and fill the space with pour in polyurethane foam. You'll get the maximum amount of space occupation, for the least amount of weight.
     
  7. TANSL
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    TANSL Senior Member

    "... fill the space with pour in polyurethane foam".
    In this way, when you have, for whatever reason, to remove it, you will suffer much more than if you fill it with table tennis balls.
     
  8. BertKu
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    BertKu Senior Member

    That is indeed a very good point. Bert

    PAR, I don’t know whether that is true. (if you allow me to disagree)
    A 2 Liter coke bottle is 70 gram for 180 litre I need 90 bottles x 70 gram = 6,3 Kg. The foam is 1,1 kg per 1 litre expandable to 20 litre (if I can believe the rumours) thus I need for foam 9,9 Kg for 180 litre. I should thus save weight, if I do a combination. However I haven’t weighed the 5 litre very strong wine bags, which can easy blown with some extra air.
    You are correct that for 180 litre I need at least 3000 table tennis balls, which are 2.7 gram each (according to international standards 4 cm each) and that also makes 8,1 kg minimum, but probably more.
    As soon I have weighed the 5 liter Wine bags, I can discuss what the best would be. There I would need 36 bags or less and then with foam.

    Only foam, a combination between wine bags and foam, or maybe a combination of the above. Time will learn to see what the overall cost will be and the maximum weight saving. Also what would be the easiest if I indeed had to get to my bolts or whatever.
    Bert
     
  9. BertKu
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    BertKu Senior Member

    PAR, you are right, I placed a number of table tens balls in a litre jar, and after calculating, the number of balls (4578) are much heavier than the foam alone.
    It seems that I have to go for just foam or where the bolts are some bags and fill the rest up with foam. At least I will be able then to get to the bolts and nuts. Should I ever sell the boat, I am then able to remove the solar panels, transom extension and all extra's on the electric boat and sell just the cabin cruiser to somebody who likes to put 2 outboards on it.
    Thanks Gonzo, PAR and TANSL, it is always good to exchange views on this forum and get the correct final direction to take. Much obliged. Bert
     
    Last edited: Jul 12, 2016
  10. PAR
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    PAR Yacht Designer/Builder

    Foam is very easy to remove, if you approuch the problem appropriately. Most just cut out the bulk of it with wood working tools, then move to pressure washer and/or chemicals. If the foam is installed with the idea it will be removed, it can be partitioned off into easily removable chunks, which requires some form of surface release. Plastic shrink wrap works well, wax and even plastic bags can accomplish this role.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Ping pong balls ? Are they really that cheap ?
     
  12. PAR
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    PAR Yacht Designer/Builder

    No, not really, but it is what some amateurs like to employ, thinking they're clever. The same applies to milk jugs, pool noodles and the like. The reality is, if you have a compartment, just seal the thing up and stop worrying about things that will never happen.

    I built a raid boat not long ago with 4 floatation compartments. The owner tried to insist on foam filling them and I ask why, do you expect all 4 of these puppies to get breached at the same time and if you do, wouldn't you think you'd have bigger concerns than a swamped boat, if they did. He said he hadn't looked at it that way and asked what would happen if only one chamber was breached, to which I replied the boat would still float, just not as high as I'd like and you might have to live with tossing the cooler of beer over the side, until you baled out enough water to bring it aboard again. I installed four 6" deck plates, one in each chamber as planned and though he has capsized the boat twice that I know of, it hasn't been broadsided by anything big enough to breach any of the compartments yet and best of all, he stores his cell phone and GPS in one of them.

    I run into this sort of thing regularly, an owner or client developing a SOR, with unreasonable expectations. "I want a shoal draft cruiser, that's self righting, with full standing headroom throughout, of course it has to be very light because my little car can't trailer a very heavy boat, and it needs to be 23' on deck or I can't get it into my garage, in between trips across the Pacific Ocean." Really . . .

    A sealed compartment is better floatation than a sealed compartment with foam (or ping pong balls) in it. It can be used for storage, it can be inspected and it can be sealed up tight to act like a floatation chamber, if desired. Ask yourself some serious questions about your experiences and operational area. Have you ever been holed? Was it sufficiently problematic enough to cause you to consider coping with a fully swamped boat? Have you ever sunk a boat, because you lacked sufficient floatation? If you're anything like 99% of the pleasure boaters of the world, you've never even come close to these situations, so why 'the end of the world is near' approuch to something that will never likely occur? Just in case? Well, it's possible an airliner can fall from the sky and land on your head, so maybe you might consider carrying around a radar unit, just in case . . .

    All the joking aside, provide access ports and make these hull areas water tight and move onto your next problem or concerns.
     
  13. BertKu
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    BertKu Senior Member

    Hi Mr. Efficiency, You probably have never heard about the joke. Here is a little boy hitting nails in a very expensive piano. A visitor came along and remarked: Geehh, that is a very expensive hobby!. No, said the father of the boy , not at all. I am getting the nails at wholesale price!.

    Look, if nobody explores new ideas, we all would be sailing the same shape and model boat. Bert
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    Hello mate, nothing wrong with adapting things to different purposes, but it seems to me it would be a very expensive form of floation.
     

  15. Steve W
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    Steve W Senior Member

    The best form of floatation is just sealed tanks, air is the lightest. However, if the tank gets breached you may loose buoyancy which of course is why a lot of folks don't trust just plain air. I have built boats with pour in coast guard approved polyurethane foam but will no longer do so as even though it is claimed to be closed cell it soaks up water like a sponge anyway, we pulled over 100lbs of the stuff out of an area under the fwd berth of a boat last summer and ive removed a lot of it from under the sole in fishing boats so, until the come up with something that really does not absorb water I will not be using it again. I used to own a Macgregor 36 catamaran that had every extra space filled with polystyrene foam which I did remove (to do work) and none of it was waterlogged even though there had been water in the compartments so in my opinion it is much better but of course you cant pour it in place and fill every space. Up here in the Midwest they sell dock billets of polystyrene that sit unprotected in the water supporting docks. However a couple of years ago I cut up an old beach cat that had blocks of polystyrene in the hulls and to my surprise some of them were waterlogged, it shook my confidence I must say. So, ping pong balls, pop bottles etc look pretty good to me as if they are in a sealed tank the are really a just a backup. I don't think I would bother with foaming around them though. BTW, where do you buy ping pong balls in bulk for a reasonable price?
     
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