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Buoyancy foam EmptyYesterday at 3:35 pm by david f

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    Buoyancy foam

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    Michaelc


    Posts : 20
    Join date : 2021-04-22

    Buoyancy foam Empty Buoyancy foam

    Post  Michaelc Sat May 29, 2021 5:56 pm

    Hi all. I need to know the best method to add some buoyancy to the hull of my T class submarine. I know people use foam, but what type is it that will not take in water. I have been thinking of cutting up the inners of an old life jacket. What are your views.thanks
    salmon
    salmon
    AMS Forum Owner


    Posts : 312
    Join date : 2011-09-02
    Age : 62
    Location : Las Vegas, Nevada - USA

    Buoyancy foam Empty Re: Buoyancy foam

    Post  salmon Sun May 30, 2021 2:03 pm

    The important consideration is closed cell foam. Polystyrene XPS foam boards are what I use.
    In the U.S. there is the pink stuff like this:

    https://www.homedepot.com/p/Owens-Corning-FOAMULAR-1-2-in-x-4-ft-x-8-ft-R-3-Square-Edge-Rigid-Foam-Board-Insulation-Sheathing-36L/100320356

    There is also a blue version too, but not an Owen Corning
    https://taichun.en.alibaba.com/product/60815928267-222422514/Modified_XPS_Extruded_Polystyrene_Sheet_Blue_Foam_Board_Insulation_Price.html

    These boards offer great buoyancy and are dense enough that you can cut, sand, and saw into the shapes you need to fit.


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    If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.
    avatar
    Michaelc


    Posts : 20
    Join date : 2021-04-22

    Buoyancy foam Empty Thanks

    Post  Michaelc Sun May 30, 2021 2:19 pm

    Thanks, not sure this board is available in the uk. At the moment due to problems with Chinese most shops in the uk have many empty shelf’s. But will try and find some.
    david f
    david f
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    Buoyancy foam Empty Re: Buoyancy foam

    Post  david f Wed Jun 02, 2021 9:37 am

    You can get blue closed cell foam here in the UK. Probably available at B & Q etc but the last lot I got I ordered a small sheet from an eBay supplier (it was also described as closed cell) and it has been enough for several models.

    David
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    Michaelc


    Posts : 20
    Join date : 2021-04-22

    Buoyancy foam Empty Blue foam

    Post  Michaelc Wed Jun 02, 2021 10:07 am

    Just returned from wickes, no blue foam, but purchased some kingspan. It looks like it works for lining the inner hull, but for the closed nose section which needs filling a bit I am thinking of cutting up some swim noodles. Test still on going, and my take longer then I hoped due to wife being home and wanting the house DIY completed. They just don’t understand that subs have needs.

    david f likes this post

    salmon
    salmon
    AMS Forum Owner


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    Buoyancy foam Empty Re: Buoyancy foam

    Post  salmon Thu Jun 03, 2021 4:11 pm

    Michaelc wrote:They just don’t understand that subs have needs.


    LOL - that is funny.

    I have seen people use the pool noodles. I would think it works, but I cannot say from first hand experience.
    The key to adding weight and foam is keep the weight as low as possible and the foam as high as possible. The only time you put foam above the waterline is for submerged trim. All other foam is at or below waterline. These are general rules, but depending on the room you have it may need to be broken.

    That being said are you familiar with why I mention keeping weight low and foam as high as possible? If so, then ignore my next statement. You want the highest metacentric height as possible. The further your weight is from the foam the more stable the sub will be. I have a Skipjack that I barely put any foam in (only enough for submerged trim) and if I use my full throttle, the sub will turn on its side (I do not use full throttle very often). Why? I have a small metacentric height. The WTC/ballast tank is in the center of the boat so, close to the weight. Now if I added more weigh and more foam I can build up that dynamic between the weight and foam and the sub will run incredibly stable on the surface at any speed. Why didn't I do that? Trimming a sub becomes a frustrating thing at times, adding weight and more foam is a artwork in itself and the more weight added means the more I have to lift and hoist out of the water (I am getting old). I also wanted to see how it handled with minimum foam - and could I do it. The answer is yes.  I am inspired/learning from a gentleman who has done this for decades longer than I and willing to try something new if I can see it demonstrated that it works. His subs are perfection. My Skipjack runs great, but I know the performance limitations, but would not change a thing.


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    Michaelc


    Posts : 20
    Join date : 2021-04-22

    Buoyancy foam Empty Foam

    Post  Michaelc Thu Jun 03, 2021 6:01 pm

    Hi, thanks for the advice. The problem I have with the T class is that the bow is part closed in. On putting the sub in the water it drops by the bow. So I hope that by filling the bow section with noodles it will lift it up a bit. I have used kingspan in the lower hull space only and so far almost have the sub at the correct trim.all a bit of fun.

    salmon likes this post

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