Gardner:
There are a lot of website with simple to make boards. lately I have been looking at the Bernd Kohler yahoo group from his K=design catamarans http://groups.
and in the files section he has a good document showing how to make the rudders - it is called dragudmaking.
--- In harryproa@yahoogrou
>
> Hi,
>
> Thanks for the reply, but I am, as always, a bit dense on understanding it.
> I looked up the NACA foils on wikipedia, and I think I now understand what a
> NACA 0012 16" chord looks like, and I have a formula from which I can derive
> the position of maximum thickness, which is (I assume) where I would place
> the shaft. I do have construction questions, though.
>
> Are you saying that you are making your rudder out of 1 piece and bending
> it, or 2 pieces and joining it?
>
> Are you carving foam and glassing over it, or making a flat panel?
>
> You say you are getting the right radius from 1 layer of double bias. That
> sounds like you are making it flat, without a core, but you then mention
> that you are using 10mm foam. So are you using 10mm foam, glassed on just 1
> side and slitting the foam before bending? Or are you using 10mm foam for
> the sides and just 1 layer of glass for the leading edge that gets bent?
>
> I tried googling "sheer web" but I don't get any results that seem to have
> to do with boat construction. Is that a method of attaching the shaft to the
> rudder?
>
> I can wait for pictures to build, but I may need to order some materials. I
> was going to order some 3/8" (10mm) corecell for beams and a kayak, so I was
> planning on using the same for the rudder. Since my plywood proa is only 20'
> long, and your 16" chord is for your 50', I am assuming I should use
> something like a 10" chord??
>
> I keep trying to tell myself that there may be lurkers here as ignorant as
> myself, for which my dumb questions can do some good and that they are not
> exclusively annoying. If not, just say so and I will send private emails.
>
> - Gardner
> York, PA
>
> On Sun, Mar 28, 2010 at 12:23 AM, Rob Denney <harryproa@.
>
> >
> >
> > I am getting the right radius for a NACA 0012 16" chord from one layer of
> > 400 double bias. You should manage with 200 plain weave. Suggest you don't
> > glass the interior until you are ready to close it up, then add a couple of
> > extra layers to the nopse section and an inner skin to the core. I use 10mm
> > foam glassed on the outside and it conforms to the aft sectionof said foil.
> > Unless the ply is very thin, I would cut slits in it pre bending. A
> > sheer web at max thickness (I have a shaft) gives the sheet something to
> > bend around. Glass only ahead of the web. I totally screwed up my first
> > one, should have the second attempt ready this week, will post some pics.
> > If you really want to get stuck into it, let me know what is unclear in the
> > above.
> >
> > rob
> >
> >
> > On Sun, Mar 28, 2010 at 1:00 AM, Gardner Pomper <gardner@...
> >
> >>
> >>
> >> Hi,
> >>
> >> I was wondering what the current "best practice" idea is for building a
> >> simple rudder (I need to build 2 for my plywood proa, from last year). I was
> >> considering trying to make it as one panel, with no core material at the
> >> leading edge and bending the fiberglass 180 degrees, but the practice piece
> >> I made seemed like that was too much of a bend for the fiberglass. It seemed
> >> like it wanted to delaminate, because the outer layers had to be longer than
> >> the inner layers to make the curve.
> >>
> >> My next idea was to build the rudder in two halves, using Derek Kelsall's
> >> deck edge radius type scheme and glue the 2 halves together, but I wasn't
> >> sure of being able to make a good bond on the inside of the curve.
> >>
> >> Finally, I guess I could just carve foam, and layup the fiberglass over it
> >> and then vacuum bag it.
> >>
> >> What is the current thinking? I would like something pretty simple, and it
> >> doesn't need to last long, but I would like to get it done soon so that I
> >> can try out the proa sailing this summer.
> >>
> >> Thanks,
> >> - Gardner
> >>
> >>
> >
> >
>