Rebuilding rudder

[johnmwalsh]

Hello everyone! Hope you had a great 4th of July! I have a fiberglass over mahogany rudder that I pulled the glass off of, glass was delaminated from the wood, I need to build up some thickness of wood before I reglass it, do you guys/gals think I can use strips of oak or should I stick with mahogany? I need to add thickness to areas some 3/8”. The rudder has some flat spots, low spots, thank you for your time and expertise! John

[Bill O]

Time for a new rudder? How about using Coosa? Here's how we made a new rudder core to get rid of all the wood.

[johnmwalsh]

That looks awesome!! Do you have any more pics of how you set up the router to form the rudder? Thank you

[Bill O]

If you look at the article you'll see the pics of the routering process.

For our boat I made the rudder w/a NACA 0010 shape and made a template out of frp which was attached to bottom of the Coosa laminate. Then it was easy to set the router bit depth to make the passes to remove much of the excess material. This created steps that were sanded out to the "contour lines" set in by the router. Relatively easy, but somewhat tedious and dusty.

Had seen some people make a jig to use on a table saw or a circular saw. Tried the circular saw first, but thought the router was more precise and less passes to remove material.

[Chotu]

That’s really nice, Bill. Interesting and new technique thanks to relatively new materials.


There is also the old tried and true methods of using foam to make a foam core in much the way you did with the NACA profile, then glassing over the foam.

If you go the foam route, you need to have some of the profiles with glass faces as well to glass the rudder post to inside the rudder.

This is how I built my rudders and can share if the OP is interested

[tkeithlu]

It sounds like you are headed to making a new rudder rather than strengthening your present one. If you do stick with your present rudder, I would not recommend oak in that application, because a little water ingress will turn it black. A new rudder does give you the advantage of reducing drag through shape as Bill O did.

[Bill O]

Originally Posted by Chotu

That’s really nice, Bill. Interesting and new technique thanks to relatively new materials.


There is also the old tried and true methods of using foam to make a foam core in much the way you did with the NACA profile, then glassing over the foam.

If you go the foam route, you need to have some of the profiles with glass faces as well to glass the rudder post to inside the rudder.

This is how I built my rudders and can share if the OP is interested

Thanks. We used the Coosa since I didn't ever want to rebuild the rudder again.

While it can take a while, a 2 part foam core could eventually get wet. There are some nice sheets of structural foam that could be easily laminated/infused w/resin then shaped and glassed.

The internal layers of glass and f/g strands along w/the higher density Coosa material gave me the characteristics I wanted for the rudder. Again probably over kill, but expect to keep the boat for a while (or until I can't sail any more whichever comes first).

Was hoping the OP would provide more info on the boat and type of rudder they wanted. Could follow the stock rudder design, but sometimes there are better profiles w/increased lift.

[Dave_S]

You could have the rudder profile drawn up in CAD then machined on a CNC router. If you provide the timber laminated the way you would like it, it would not be difficult to set up and 3d machine it to very accurate tolerances and with a good finish, requiring little sanding.