Subject: [harryproa] Re: Materials list, Price!!!!
From: Mike Crawford
Date: 3/3/2006, 8:05 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

<< 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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