-You have longitudinal strength in triaxial where needed and extra
uni in concentrated areas. A bit of movement in the structure
shouldn't matter provided the material isn't brittle and the stress
and strain parameters coordinate and the bonding is good. Don't
really see haow a resin filled seam weakens the structure as it is
part of the web of the I beam structure.
regards
robert
g-- In harryproa@yahoogroups.com.au, Mike Crawford <jmichael@g...>
wrote:
>
> << I actually prefer the resilience of the polycore to the strength
of
> the Kiri as tests I have read indicate it is better under
collision>>
>
> I think that kiri or cedar would probably test differently than
balsa,
> but I'm still willing to buy the argument. For the sake of
discussion,
> let's say that polycore is stronger in collision. But what about
as a
> complete structure taking a pounding in a storm? That's a
different
> kind of strength. I'd have more faith in a strip-planked boat with
good
> longitudinal strength throughout the entire hull, than in a cored
boat
> that's going to have resin-filled seams that won't offer as much
structure.
>
> That's really the crux of the matter for me. What's more
important:
> collision or pounding? I'm personally more concerned about the
latter,
> but there's clearly no right answer.
>
> Of course, if tortured polycore could save me a few hundred kg,
and/or
> a thousand hours, I'd put the intellectual argument aside and jump
on board.
>
> - Mike
>
>
>
> Robert wrote:
>
> > By the time you buy good quality ply, resin impregnate with a
> > protective glass skin and glue and glass joints, I couldn't get
much
> > cheaper and certainly not lighter than polycore and glass.
Polycore
> > with two 400g skins and resin comes to about A$110 dollars a 1200x
> > 2400 sheet (including consumables) and abou 6kg (extrapolating
from
> > Rob's friend at 2.3Kg/m2) with 600 and 400 glass. This is about
the
> > weight of 6mm ply dry, which then needs stringers. I believe a
> > modification of the KSS system is possible for a Harry and this is
> > what I intend to aim at A certain amount of torturing should be
> > possible with a single skin and then fixed when the other skin is
> > added. I think it also posible to build in a certain amount of
> > compound curvature into the table before the bending. Derek
Kelsall
> > is playing with that idea.
> > I actually prefer the resilience of the polycore to the strength
of
> > the Kiri as tests I have read indicate it is better under
collision-
> > see Nidacore website- and my own experience with polyprop supports
> > the results. I have a fondness for tortured ply with many
> > experience in small catsand dinghies, but I relly think its time
has
> > passed for larger boats I would prefer to build in strip plank and
> > ply because I actually find it a meditation and greatly
satisfying.
> > Seems such a shame to paint it and smooth out the strips to make
it
> > look like a fibreglass structure. I intend to make my internal
> > furniture out of it for the looks.
> > regards,
> > robert
> >
> >
> > -- In harryproa@yahoogroups.com.au, Mike Crawford <jmichael@g...>
> > wrote:
> > >
> > >
> > > I believe there are a number of folks who would like to try
> > tortured
> > > ply, cylinder moulding, and KSS construction, but aren't sure
> > about how
> > > to replicate some of the compound curves found on the
harryproas.
> > >
> > > If money were no object, and I were paying a yard to build the
> > boat,
> > > I'd go with strip-planked kiri. Although it would have some
extra
> > > weight over corecell, I'd enjoy the peace of mind that comes
from
> > having
> > > a solid structure even before the glass and resin are added.
> > >
> > > On the other hand, if I had to build the hulls myself, I'd be
> > sorely
> > > tempted by the speed of the other construction techniques.
> > Provided I
> > > was aware of a way to get those nice compound curves found on
the
> > > topsides of harryrpoa hulls, of course.
> > >
> > > Any light you can shed on this issue would definitely be
> > appreciated.
> > >
> > > Congratulations on your proas, by the way. Is there a place
> > where we
> > > can learn more about them?
> > >
> > > - Mike
> > >
> > >
> > >
> > > jerry freedomev wrote:
> > >
> > > > Hi Robert and All,
> > > > I'd think a HarryProa wuld be easily built
> > in
> > > > tortured ply technic for much less money, labor, weight. Any
> > reason
> > > > why it wasn't used?
> > > > In it I've built a 28' proa with the room
of
> > a
> > > > much larger Harry for under $2,000 in materials. And a much
> > larger 36"
> > > > Proa in about $3,000.
> > > > Thanks,
> > > > Jerry Dycus
> > > >
> > > >
> > > > */Robert <cateran1949@y...>/* wrote:
> > > >
> > > > From my own minimal experience, it is more important to
get
> > > > reasonably accurate dimensions rather than finish as you
are
> > going to
> > > > sand a lot of it away. If you are cutting the planks
> > yourself you can
> > > > get three different widths according to curvature and make
> > the
> > > > chamfered edge at the same time. If you really want to be
> > fancy, you
> > > > can glue all the strips to full length and taper and
chamfer
> > them
> > > > before you start and almost completely avoid cheaters.
> > > > Techniques for using polyprop honeycomb are on the
nidacore
> > site. It
> > > > is worth while looking at the impact testing of polyprop
> > honeycomb
> > > > sandwic compared with balsa core. A great lump of RSJ was
> > hoisted up
> > > > to the heoght of the shed roof and dropped onto the
> > sandwiches. The
> > > > polycore caused the RSJ to bouce up into the air without
> > damage while
> > > > the balsa fore fractured. I believe, though I haven't
tried
> > it with
> > > > polycore that a hot iron can put creases into the face of
> > one side
> > > > to control bending and also to provide resin channels for
> > resin
> > > > infusion. I think it well worth using vacuum bagging to
> > reduce weight
> > > > and impove adhesion for high stress areas but at a price
of
> > extra
> > > > consumables and effort but I am in two minds about
infusion.
> > > > The difference in price is not worth hassling over. I'd be
> > tempted to
> > > > use poulonia in the high stress areas to save on glass and
> > polycore
> > > > in the flat, low stress areas to save on time and weight
> > > >
> > > > home.houston.rr.com/pieceofwork/index.htm is a good
website
> > to check
> > > > out
> > > >
> > > > congratulations about having suport from your boss for the
> > project.
> > > > Good luck wit the finances.
> > > > regards,
> > > > Robert
> > > > --- In harryproa@yahoogroups.com.au, David Howie <dana-
> > tenacity@u...>
> > > > wrote:
> > > > >
> > > > >
> > > > > Part of the problem is to know whether you are comparing
> > apples with
> > > > > orangutans. That price for paulonia is raw planks, need
to
> > be
> > > > dressed and cut.
> > > > > Don't know whether the planks are to be cambered on the
> > edges. Poly
> > > > sounds
> > > > > fascinating, lots of unanswered questions, how does
> > anything bond
> > > > to it? can
> > > > > an amateur work it successfully.
> > > > > Speaking of amateur I started off thinking I knew
> > something about
> > > > this boat
> > > > > stuff, but the deeper I dig the less I know.
> > > > > Pity there isn't somebody else nearby who was thinking
of
> > building
> > > > a Harry.
> > > > > Trying to talk my wife into a trip to Aus when Bain's
boat
> > hits the
> > > > water
> > > > > (presumptive of me isn't it?), she doesn't think much of
> > Aus, but
> > > > she has
> > > > > given the project the green light if the funding
happens.
> > > > >
> > > > >
> > > > > ------ Original Message ------
> > > > > Received: Wed, 01 Mar 2006 06:26:30 PM MST
> > > > > From: "Robert" <cateran1949@y...>
> > > > > To: harryproa@yahoogroups.com.au
> > > > > Subject: [harryproa] Re: Materials list
> > > > >
> > > > > I couldn't get near that price for Poulonia. Suspect rob
> > can get
> > > > much
> > > > > better prices on glass and carbon. Probably worth the
> > freight. May
> > > > have
> > > > > to wait on carbon till the shortage is overcome and
prices
> > > > approximate
> > > > > manufacturing costs rather than scarcity. Can you give
> > areas of
> > > > > materials to allow comparisons?
> > > > > My calculations for polycore are with no ply, larger
> > cockpit/saloon
> > > > and
> > > > > a cockpit cover like Bain's.
> > > > > Overall calculations are not that different. I get in
the
> > order of
> > > > $30k
> > > > > sailaway with schooner rig, including consumables. only
> > $10k for
> > > > basic
> > > > > boat materials.
> > > > > Regards,
> > > > > Robert
> > > > >
> > > > > --- In harryproa@yahoogroups.com.au, "oceanplodder2003"
> > <dana-
> > > > > tenacity@u...> wrote:
> > > > > >
> > > > > > OK it's in files now.
> > > > > > >
> > > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
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