Home made Ida-sailor rudder suggestions?

[TimW]

Hi all -
      It's seems there's pretty solid consensus on performance improvements achievable with an ida-sailor rudder assembly.  Being new to sailing
(and never actually having seen one) I'm trying to understand where the improvement really comes from and whether I can simple fabricate my own
version that could slide over myy existing (after shorteniing) aluminum rudder.  I'm guessing it's description as a foil implies  a thicker blade but
with tapered ends?  Has anyone made one themselves  and be willing to share a basic drawing of what they made?   Having recently identified some large pieces of scrap 1/4" polypropylene sheet I'm thinking I'd like to give it a try....
        thanks in advance....TimW

[Salty19]

There is a ton of info from Doug142, Greene, Bob23 and others if you look back in the 16, 19 and boat modification sections.
I think Doug142 sells templates of the foil. You want to use NACA0012 or NACA0014 style.

Search around (the search box is up and to the right), all you need to know is in this forum, albeit scattered around a bit.

Here's a very nice writeup from Greene to get you started.

http://cpyoa.geekworkshosting.com/forum/index.php?topic=3106.0

The foil is well worth the effort for sure.

[Lafayette Bruce]

I haven't shared much how I made mine last Spring but my process worked great.  I purchased "Last a Foam"  from Fiberglass Supply in Washington state (stuff they make surf boards from) and I cut the foam into strips about 1" narrower than my sander.  I then made wooden ribs out of hardwood that were router cut to the foil shape.  I alternated ribs and foam as I epoxied them to the rudder, then sanded the foam down to the level with the formed ribs.  The foam sands very easily but as the sander came to the hardwood rib, the sanding slowed and the whole surface was flush.  The whole thing was then covered in 3 coats of fiberglass.  Make since?

[skip1930]

Wow! Aeroplane quality work. You realize that these rudders have to be in the water? So how come your trying to lift the stern out of the water by using a highly buoyant rudder?

No~really a super rudder. Ought to work fine. Says so in the book. Good job. I only with I could do work like that.

skip.

[Lafayette Bruce]

I was concerned about the buoyancy of the Last a Foam and to counteract that I made some chambers between the foam and rudder and filled them with lead shot and then epoxied it all together.  When I loosen the pivot screw on the rudder the blade does not float so I must have gotten it right.