[Rhodes22-list] ...on spray foam and other musings....

Hank hnw555 at gmail.com
Tue Feb 14 08:43:26 EST 2012


If you want to see a really good chronicle of someone building a large
steel sailboat go to http://www.thebigsailboatproject.com/.  Two ladies up
in Canada built it pretty much by their selves and did a great job of
documenting it.  They include some sections on insulating the hull and some
issues they ran into.



On Tue, Feb 14, 2012 at 8:32 AM, Goodness <spreadgoodnews at gmail.com> wrote:

> Thanks Rob.  I am building out a 43' steel sailboat hull.  I am finishing
> the final interior epoxy coats now then i will spray closed cell
> polyurethane foam all over the interior hull over the stringers and ribs.
>  Then i have read i should spray a fire retardant elastomeric paint over
> the foam to resist ignition in case of an interior fire. This foam will
> insulate as well as contribute to the oxygen barrier of the epoxy.
> what kind of foam did boston whaler use in their hull construction?  My
> friend has a bw dinghy hull that weighs about 300 pounds! Thats like 20
> gallons of absorbed water!  My understanding of closed cell foam is that if
> it is cut after spraying it will absorb some, but i am not sure how much.
>  I think the Rhodes has the good stuff in there like the foam that floats
> docks.(closed cell polyurethane?)
> Also is a pool noodle polyethelene foam? You can get that stuff in sheets
> and it would be nice to insulate the rhodes interior hull with.  It wont
> absorb water either.
> Thanks,
> Bob
> On Feb 13, 2012, at 9:58 PM, Rob Granger <rgranger at sbc.edu> wrote:
> > Okay I didn't want to seem heavy handed when I stated before that I was
> > "almost certain" that Great Stuff is closed cell because there is a lot
> of
> > controversy on this topic and to be fair, not all spray foams are the
> > same... but I'm a chemist and I felt it was necessary that we get this
> > straitened out since many of us are DIY boaters...  so on the topic of
> > spray foam
> >
> > Some spray foams are latex and therefore open celled (DO NOT USE LATEX
> > SPRAY FOAM ON YOUR BOAT) but Great Stuff expanding spray foam is a
> > polyurethane-based foam and not a latex foam.  So unlike the latex spray
> > foams it is *closed cell*.   And you should not be afraid of it absorbing
> > water.  It will (however) stick to the hull like ... well a polyurethane
> > glue (think Gorilla glue).  So the bag idea is the way to go if you ever
> > want to get it out again... or line the area with visqueen before you
> > spray.  I've used both approaches and they both work fine...  I can post
> > pictures if anyone wants to see the results of the bag or visqueen
> > approach.
> >
> > So to clarify, polyurethane foam (Great Stuff)  is *closed cell*... so it
> > is fine to use on your boat, even in low spots.
> >
> > The pink and blue foam boards at Lowes and HomeDepo are also great to use
> > for floatation foam.  They are *extruded* polystyrene and so they will
> not
> > fall apart into tiny little balls that make a mess everywhere... (Iike
> > cheap styrofoam will).  I have about six 3" boards cut up and crammed
> into
> > my MacGregor 22'.  And all of the little left over pieces are in a bag,
> > crammed into a tight spot and filled with spray foam (along with some
> > packing peanuts I got in Christmas boxes this year).
> >
> > A note on packing peanuts.  They're now two kinds.  The old-school kind
> are
> > made of styrofoam.  Those are fine to use on a boat.  The other type are
> "*
> > green*" and made of cellulose.  The cellulose peanuts will dissolve in
> > water.  Obviously you do not want to use those.  It is easy to tell which
> > type you have.  Drop one in a glass of water and wait a bit.  Or you can
> > bite one  :-)
> >
> > If you are skeptical about the closed cell nature of Great Stuff
> expanding
> > foam...(and it is not a bad thing to be skeptical) you can read about it
> on
> > the Dow Chemical site... you wont hurt my feelings if you do... I promise
> > :-)
> >
> > Here is the link to the Dow Chemical site
> >
> > http://building.dow.com/na/en/products/sealants/windowdoor.htm
> >
> >
> > my 2 cents.
> >
> > ... the other Rob
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