Thank you for good hints. I will use wood for the core anyway.
Regards,
Arttu
> Bain's Harry used end grain balsa with carbon tow skin for about a
100mm wide strip in the centre and strip planked kiri for the rest.
There should not be any warping problems with this set up. I gave him a
hand in the bogging and fairing and it looked a very nice set up .
Theoretically, this comes out strong and stiff and reasonably priced
>
> --- In harryproa@yahoogroups.com.au, George Kuck <chesapeake410@...> wrote:
> >
> > Hello,
> >
> > You may consider using a combination of a plywood core with straight
timber laminated over (both sides) ,then shaped and glassed. That is
how my TT720 centerboard was built according to plans by Ian Farrier.
It was built in 1991 and has held up since then with no problems. I used
Douglas fir over marine grade mahogany. As I recall I think I probably
used 3/8" ply and 1/2" fir which was cut in strips and thickness planed
down from 3/4" stock. The plywood I think helps to keep board from
warping and gives you a base to laminate solid wood on.
> >
> > Happy sailing,
> > George Kuck
> >
> > --- On Mon, 6/21/10, Rob Denney <harryproa@...> wrote:
> >
> >
> > From: Rob Denney <harryproa@...>
> > Subject: Re: [harryproa] Visionarry and daggerboards
> > To: harryproa@yahoogroups.com.au
> > Date: Monday, June 21, 2010, 7:49 PM
> >
> >
> >
> >
> >
> >
> > Excellent news, apart from the breakages. May I suggest you use
straight timber rather than ply, which is notorious for breaking when
used for centreboards.
> >
> > Please keep the results coming.
> >
> > regards,
> >
> > rob
> >
> >
> > On Tue, Jun 22, 2010 at 2:14 AM, proabuilder <arttuheinonen@
heinoset. net> wrote:
> >
> >
> >
> >
> >
> >
> > Hi,
> >
> > Now the daggerboards are installed and we have some experience.
Daggerboards are 1.7m x 0.55m area below the hull. The case opening is
on the midline and upper opening close to the hatch. Daggerboard case is
supported by the ring frame between the mast and the hatch. The ring
frame is extended to the case at the lee side. the foil is 55mm thick
asymetric Speer section with carbon-plywood/ foam core.
> > I tried to finish them to a high standard. They are quiet and there
is no noticeable vibration.
> > We used one rudder only, so one way it is at the fwd end and the
other way at the rear end. We managed to shunt with both foils down,
then released the fwd one and pulled it up as needed. When we sailed
rudder forward we kept the rear foil full down , lifted fwd foil all up
and when going other way we managed too keep the fwd foil partially
down. We are aiming to learn to use as little foil area as needed, now
that we have already broke one daggerboard.
> >
> > We spent three days sailing with the new arrangement. The boat was
much more enjoyable to sail, less steering needed and easier shunts. Low
speeds are not so critical anymore.
> > We also had some stronger winds, stronger than expected. I sailed
too fast with too much sail area rear daggerboard almots full down, and
it snapped at 14 knots. It made a loud bang. First I thought it was
something on the rig but fortunately not.
> > Then handling the boat became difficult, not possible to gain speed
and the boat wanted to go sideways.
> > I had a look at the stub and it had failed at the compression side.
Great forces, must say. The daggerboard was made stronger than the
Hrryproa design rudders. Next one will be solid plywood with carbon and
glass.
> > The daggerboard case is ok.
> >
> > Now I must make another pair of daggerboards, one for use and
another for spare.
> >
> > Regards,
> >
> > Arttu
> >
>
>