-Hi Gardner,
Modulus is how much give for how much it is pulled ot pushed. For me there is another aspect to consider: does it deform or bust if stressed? This -and the price - of polyprop honeycomb is one of the big reasons for my choice, especially with the new scrim that reduces the take up to 45g/m2. I think that it is possible to work out a way of weld sealing the ends without distortion or or bogging after a suitable primer.
Personally Iwould avoid pu foam , but I am probably prejudiced after soggy surfboards anf I have seen good multihulls built with it 35 years old. It may well be an improved product.
-- In harryproa@yahoogrou
>
> Hi,
> I have heard of surfboard.. I have seen windsurfers.
> they are built. I thought that they were often built with a styrofoam core.
>
> Tthe rated shear strength of Aircell is in the same ballpark as the
> honeycombs. Here are a few comparative numbers for shear strength:
>
> Nidacore (honeycomb, available in US) : 0.5
> Polycore (honeycomb, only in Australia): 0.8
> Aircell (6lb PU foam): 0.88
> Corecell A500 (6lb PVC foam) 0.85
>
> So it is not obvious that Aircell is bad from that. Where Aircell falls down
> is in compressive modulus and shear modulus.
>
> compressive modulus shear modulus
> Nidacore : 15 5
> Polycore: 92 19
> Aircell 37 16
> Corecell A500 91 30
>
> If someone could explain what shear modulus and compressive modulus are, I
> would be grateful.
>
> Anyway, I know there is alot of talk of using Polycore, whose specs look
> similar to Aircell, except for the compressive modulus (plus it is only
> available in Australia and I would rather not deal with honeycomb). There
> has been some talk of using Nidacore instead, but its specs look far worse
> than Aircell.
>
> Anyway, I am hoping that if I post enough, someone who understands this will
> actually explain it to me <grin>
>
> - Gardner
>
>
>
> On Fri, Jun 12, 2009 at 10:37 PM, Doug Haines <doha720@...
>
> >
> >
> > i'm guessing, but it could be P.U. foam that I have seen in surfboards,
> > which would probably have the cheaper stuff.
> > You know what a surfboard is I suppose?
> > Not being on the surf coast there.
> >
> > The thing the core has to do is have shear strength.
> > If that fails too soon then your core breaks and you are left with two
> > 400db glass layers as a hull.
> >
> > doug
> >
> > --- On *Sat, 13/6/09, Gardner Pomper <gardner@...
> >
> >
> > From: Gardner Pomper <gardner@...
> > Subject: Re: [harryproa] Re: AirCell tested and fails (I think)
> > To: harryproa@yahoogrou
> > Date: Saturday, 13 June, 2009, 11:01 AM
> >
> > The tower is a grain silo for the cows. Hasn't been used in 30 years or
> > so.
> >
> > Yes, the are completely different foams. Corecell is a PVC foam, as
> > espoused by derek kelsall, et al. Aircell is a polyurethane foam which is
> > waaay cheaper (about the price of polycore, I think). It is as easy to work
> > with as the PVC foams and has none of the edge problems of the honeycombs.
> > The problem is that it isn't as "good" as the PVC foams, but no one seems to
> > be able to articulate why. It seems to me that it might be "good enough" for
> > some things and I am hoping that my photos will bring enough comments that I
> > can tell.
> >
> > In term of price, 1" corecell runs $7-8 sq ft and 1" aircell is $2.75 sq ft
> >
> > - gardner
> >
> > On Fri, Jun 12, 2009 at 7:18 PM, Doug Haines <doha720@yahoo. co.uk<http://uk.mc264.
> > > wrote:
> >
> >>
> >>
> >> hi gardner,
> >>
> >> what's the round tower building attached to the barn?
> >>
> >> Are these foams just brand namesor are they actually totally different
> >> types of foam.
> >> And Rob, what is the foam I/we use called?
> >>
> >> Doug
> >>
> >> --- On *Sat, 13/6/09, gardnerpomper <gardner@networknow
> >> >* wrote:
> >>
> >>
> >> From: gardnerpomper <gardner@networknow
> >> >
> >> Subject: [harryproa] Re: AirCell tested and fails (I think)
> >> To: harryproa@yahoogrou ps.com.au<http://uk.mc264.
> >> Date: Saturday, 13 June, 2009, 8:26 AM
> >>
> >>
> >> Hi,
> >>
> >> I have posted some more photos into the Aircell Testing phot folder of
> >> this group.
> >>
> >> I redid the tests with 1" corecell. My results were:
> >>
> >> 1) hammer test - smashed foam, broke fiberglass, delaminated. I think this
> >> test was excessive
> >>
> >> 2) hand sledge against wood block hit 10 times hard - no effect. Slight
> >> indentation on top side, no delamination on either side. Much better than
> >> Aircell in this test
> >>
> >> I then added another test, which was to put the panel on the floor, climb
> >> up on the table and drop the hand sledge (about 5 lbs) from as high as I
> >> could reach. I figure this is a 10' drop.
> >>
> >> 1) Aircell - dented, no delamination
> >>
> >> 2) Corecell - dented, no delamination
> >>
> >> They both seem to be pretty equivalent on this test. I think this
> >> highlights that if you are going to toss sledgehammers onto your deck, you
> >> should probably have more than 1 layer of 18oz fiberglass on the topside.
> >> Not sure if it tells me anything else.
> >>
> >> I think the other test that I should run is to have a bigger panel,
> >> supported on either end and jump up and down on it over and over. The
> >> problem is that is a very expensive test. Shipping on all this material is
> >> running at 20% (or more) of the purchase price. I wish there was a place
> >> around where I could get it. So far, I am 400 miles from each of 3 sources.
> >>
> >> Comments are welcome, as always.
> >>
> >> - Gardner
> >>
> >>
> >>
> >
> >
> >
>
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