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Author Topic: Rigidity and Buoyancy  (Read 612 times)

LJ Crew

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Rigidity and Buoyancy
« on: June 26, 2018, 10:20:57 AM »

Has anyone used the expanding foam from Screwfix to fill empty spaces in a hull and provide rigidity and buoyancy? From the spec it looks as though it is "open cell" and will absorb water. The reviews on the "B&Q" version are not good but Screwfix's are better. Experience and advice please.
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plastic

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Re: Rigidity and Buoyancy
« Reply #1 on: June 26, 2018, 11:50:03 AM »

I use it sometimes - my boats contain no wood so there's nothing to damage if any water is absorbed and trapped between the foam & hull.
The main purpose is anti-sinking so if the boat is completely filled with water, I can still get it back.
I also use polystyrene beads mixed with waterproof PVA glue in confined spaces to fill voids and compartments.
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Bob K

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Re: Rigidity and Buoyancy
« Reply #2 on: June 26, 2018, 12:07:17 PM »

Personally, if you intend going down this route please use a closed cell PU foam.
An open cell foam is likely to soak up water like a sponge, which could defeat the object you are trying to achieve, and can't be bailed out using a syringe.
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tsenecal

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Re: Rigidity and Buoyancy
« Reply #3 on: June 26, 2018, 05:26:21 PM »

some of the over the counter expanding foam that comes in a spray can, available at hardware stores, also will never actually stop expanding...  never fill a void completely, otherwise a few years down the road, you may find a a bulge or a crack where the foam has expanded beyond the volume of the void.
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unbuiltnautilus

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Re: Rigidity and Buoyancy
« Reply #4 on: June 26, 2018, 06:18:53 PM »

Roll up some bubble wrap...
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Netleyned

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Re: Rigidity and Buoyancy
« Reply #5 on: June 26, 2018, 06:51:59 PM »

Roll up some bubble wrap...


Much safer and cheaper.
I have seen secondary expansion
of builders foam in a very expensive
model sat in the sun at the lakeside
resulting in the deck lifting off


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unbuiltnautilus

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Re: Rigidity and Buoyancy
« Reply #6 on: June 26, 2018, 07:44:29 PM »

Also, it weighs next to nothing, while 'expandyfoam' (TM pending,,) surely has a weight distribution issue associated with it. Although on SS Ohio I used buiders pink foam sheets cut and inserted between the frames of the bow and stern sections, then clad with the outer skins. Then again, that is REALLY heavy anyway!!

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grasshopper

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Re: Rigidity and Buoyancy
« Reply #7 on: June 26, 2018, 08:29:40 PM »

Iíve heard some people use those pool 'noodles' cut up and stuffed into any voids..
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unbuiltnautilus

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Re: Rigidity and Buoyancy
« Reply #8 on: June 26, 2018, 09:55:31 PM »

Iíve heard some people use those pool 'noodles' cut up and stuffed into any voids..


Yup, some of the local OMRA boys use it.
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