Looked at he website, and the internal frames are covered with some
kind of skin. Any skin has to add at least 1kg /m2.If you have to have
an inner skin, it may as well be part of the sandwich. You are also
hiding the frames and can't check for corrosion easily. Stainless
steel into alloy can cause corrosion. The stainless steel screws into
the ply , unless as Rob pointed out, you drill and presaturate the
hole, are a means of getting rot. The chines still need to be rounded,
glassed and faired, though the glassing could be part of the final
exterior glasing This seems a a fair amount of work and risk to me.
--- In harryproa@yahoogrou
>
> Not sure how you do one and a half sheets of double bias. I am
> assuming the extra sandwich thickness and glass are to eliminate the
> internal framing
>
> Looking at the weights
> 20mm core 1.6kg/m2; glass 1.8kg/m2; resin-depending on type of core,
> effort in edge joining, holes, shaping cuts, scrim for polyprop
> honeycomb` .9-1.5kg/m2. This gives a total of 4.3-4.9kg/m2
> With internal frames, this could possibly reduce to 3.2kgm2. I was
> wondering how the internal frames are covered-That could add
> significantly more weight
> Epoxy saturated 6mm marine ply is in the order of 4.5kg/m2. The ply
> still needs almost .5 kg abrasion and surface cracking protection on
> the outside, and still needs the inner frame.
> Costs of the foam sandwich depends on type of core, type of resin,
> and very much source of materials: for 20mm core $35-70/m2; resin
> $10-20/m2; glass $10-15/m2 I think you would find the costs of going
> with the ply would be similar or slightly more with the cost of the
> frame. I must admit the simple meccano approach to the frames appeals,
> but for the shape of a Harry, I don't see an advantage. Simply make
> some big flat sheets,with judicious leaving out of glass where you
> want to bend, pull or push them into shape - possibly a little extra
> shaping on the ends- and the basic hulls are there, except for the
> main bulkheads where the crossbeam loads are concentrated. I reckon a
> Visionarry hull up to topsides could be done with less than 4m2 of
> external fairing and much of the internal work will be covered by
> internal furniture. Anyway, thats what I am aiming at. I hate adding
> good materials, only to sand it off again. Don't know how much fairing
> is required on the aluminium frame set up
> Robert
>
>
>
>
> --- In harryproa@yahoogrou
> >
> > G'day,
> >
> > Col is a very smart bloke, has been designing boats for yonks and has
> > always been full of ideas, most of them good. Experimentation is a
> > good thing and so is caution , so talk to Col and at least a couple
> > of people who have built with it. Maybe build his little canoe as a
> > test. Then do the numbers and decide which suits you best.
> >
> > I worry about corrosion of alloy and screw attachment of ply, which
> > often rots around fastenings unless they are individually over
> > drilled, filled with glue and redrilled. I also think
> > glass/ply/alloy will be heavier, maybe more expensive and require
> > more finishing. Could be wrong on all counts.
> >
> > If you talk to Col, say hi from me, tell him your boat will almost
> > certainly be 20mm foam or Polycore with one and a half layers of 600
> > double bias each side and some serious strength required around the
> > mast and the beams, but no other bulkheads. Surface area of
> > Visionarry lee hull is 57 sq m. I will be very interested to see
> > what he suggests, and how it competes with the panel build method.
> > Also ask him about the large flat)ish) cabin roof and floor areas
> >
> > regards,
> >
> > Rob
> >
> > On Wed, Apr 9, 2008 at 3:40 PM, Tim Barker <clairebarker5@
> > >
> > >
> > >
> > >
> > >
> > >
> > > Hi Rob/ all
> > > Visited Col Clifford today , as much to see his radial engine as
> have a
> > > yack about build methods, very interesting guy and very cluey.
> > >
> > > What are your thoughts about the alloy internal frame system , as a
> > > person who has done quite a bit of metal fabrication it makes
> sense to
> > > me and offers some build speed advantages as far as i can see .
> Coupled
> > > with the idea of glassed ply skins it should be very cost effective
> > > tough and simple to build.
> > >
> > > For those on the site who arent familiar the method involves
standard
> > > ally extrusions and cast ally fittings which allow the frame to be
> > > fabricated from ally without welding, it is then skinned in ply or
> > > composite however the skin basically only has to act as a
waterproof
> > > membrane not as a structural member and also to hold the
structure in
> > > tension, light strong simple . WWW.ccplans.
> > >
> > > What are the various opinions out there.I myself am very
> suspiscious of
> > > ply or timber however i know that this is a fairly basless
predjudice
> > > given modern methods and materials hence the ongoing
investigation of
> > > different methods and materials.
> > >
> > > Coupled with the relative costs of some of the composite cores
on the
> > > market and the slowly dawning realization that using these
composites
> > > may result in a craft not much lighter (if at all) but
substantially
> > > more expensive than a craft using ply skins has certainly eroded my
> > > predjudices.
> > >
> > > Cheers Tim
> > >
> > >
> > >
> >
>
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