NACA Rudder Mods

[omoore]

I am hoping that those who posted about undertaking to improve their rudders with NACA foil shapes have had a chance to finish their projects.  I have two questions:  did the foil shape noticeably  improve rudder performance?  Do you have any construction tips to pass on? 
Oliver
Com-Pac 19 MkII

[skip1930]

Well, aside from purchasing a IdaSalor foiled rudder, making your own ought to be based on a copy of that foil.

Try to actually touch an actual rudder on somebody's boat and trace the foil, ie, make a template by tracing on stiff paper the bottom and top shapes and transfer the shapes onto thin basswood, making end caps.

Now build up the foiled rudder.
Much like a model Radio Controlled airplane wing, epoxy glue together several sheets of foam for thickness and cut to correct vertical height.
Maybe a backbone to start with. Could use the old slab aluminum rudder after prep sanding it.
Glue the end caps to the top and bottom edges.
Hand sand away the foam between the two end caps transferring the shape to the foam.
Impregnate some fiberglass cloth and hand lay-up over the foam and end caps.
Sand, sand, sand, fill, and sand some more to make it perfect.
And when finished, paint with an ablative coating and figure out how to fasten this rudder onto the aluminum head.

Be mindful that the breaking and impact strength of the glass covered foam, with or without an internal backbone will never be as strong as that one piece of CNC machined plastic with an aluminum backbone already in place similar to the original Com Pac rudder. -->If the rudder kicks up, it could be chopped away with the O/B propeller. If Damaged and weakened this could result in a lose of rudder on a 2000 lb boat.<-- endangering the boat and the crew. Who's liable? You or Hutchinson's.

To the questions;
1~Does it help? Yes. Immensely. Why? Efficient Laminar Flow = less turbulence and less drag. [First tried successfully on Bell's P-39]
1a~Plus it's a 'balanced' rudder. Meaning the leading edge of the rudder is ahead of the centerline mounting on the transom. Less tiller effort.

2~Construction tips. Why reinvent the wheel? Purchase a CNC unit and be done with it. That's just my opinion. Build it if you like.

skip.

[Salty19]

Welcome to the forum.  There have been quite a few discussions on it. 

Might want to click on the home page, then use the search tool for the word "foiled" and "naca".
Tons of posts should pop up with construction tips. Most glue on thin layers foam to the stock rudder, make and epoxy on a leading edge of hardwood with a curved edge (think airplane wing shape), and sand it down to a precise NACA0012 or NACA0014 shape. Cover with fiberglass and epoxy, fill with wood filler or epoxy, sand, and paint.  One person covered it with wood veneer before fiberglassing, just for the wood look.
Pretty simple, the tough part is accurate sanding to form the right shape.

In my opinion, the foiled rudder along with new sails is THE MOST IMPORTANT modification you can make in terms of sailing performance (pointing, speed, reduced weather helm and much improved steering in tight, low speed manuevers.   Yes, it makes a big difference. 

[kickingbug1]

 amen mike