I want to extend my fiberglass rudders about 8". What is the best way to do this?
Also, I dont think my rudders are stock. I have a N 5.7 and the rudders are straight so that when fully down, they angle back paralell to the transome. very hard to steer under load. I didnt realize there was a problem until a friend got a 5.8 and I noticed that his rudders curved forward below the hull.

Could I somehow take an impression of his rudder and extend it and add to my existing rudders? would I be able to make it strong enough?

http://www.murrays.com/mm5/merchant...amp;Category_Code=C-RC&Store_Code=MS

I wouldn;t try extending them yourself unless your really good at fiberglass

Best of luck

Are you sure you can't just rake them further forward to balance out the helm? Some pictures would go a long way.

I tried adding a pic and it didn't work.
They won't rake any further forward. I think maby the previous owner replaced them w/ hobie rudders. They rake back pretty far,3", way further than could be adjusted. I also would like to get them to run further down below the skeg. J Casto, if your out there, how long are your rudders? Do you have any pics?
I will try again later to add a pic of mine.

i think it would be easier to make new rudders out of plywood than it would be to extend glass ones

but probably cheaper to just buy some 2nd hand 5.2 rudders

seem to remember that performance catamarans list old boat stock

　　....seem to remember that performance catamarans list old boat parts somewhere and that the rudders for many of the nacras of that era were the same

maybe 5.2, 18sq, 5.5, 5.7 5.8 etc

perhaps with a bit of grinding you can remove whatever material limits your current rudders from coming forward, they don't have to come forward far

ps i also weep for the good old days where we could post pics directly to the forum and not just links to somewhere else where they were posted

you can still post pics... they just have to be 100k or less....

I wouldn't use plywood, unless you make the plywood. Laminating/layering up hardwood. Even the highest grade plywoods arent nearly rigid enough for rudders.

here's the link to the old parts pdf

http://nacra.us/nacra/Nacra%20Parts%20(older).pdf

and here are the lines for rudder blades

4528 Rudder Blade (Short) 5.2/5.5/5.8/6.0/18SQ
4517 Rudder Blade (Long) 5.0/5.7

so it looks like the designers of the boardless boats traded some the reduced drag, gained by not having daggers, for longer rudders, to reduce side slip when going upwind

just measured my 5.2 rudders to be 805mm at their longest point

anyone got/get a measurement for 5.0 or 5.7 rudders?

azcat, it looks as if your rudders not at least 805mm long that that may be why you've been struggling to get upwind with the boarded boats

I just made a daggerboard for a Sunfish using a solid piece of African tapele wood, which is similar to mahogany but about half the price. The cutting & shaping process took 4 hours, but I'm extremely pleased with the final product. I've already decided that when I break or lose one of my cat rudders, I'm gonna do 'em both in tapele. Although I do my own hack fiberglass work, I found wood much more enjoyable to work with. A couple of coats of epoxy paint later and it was all done.

I found an old pic from back when you were having problems with the crossbar assembly. http://www.catsailor.com/forums/ubb...er=8558&filename=125068-IMGA0997.JPG

Those look like stock rudders as far as I can tell. You sure the white plastic adjustment screw is not in too far?

If you are still considering extending what you have I would suggest adding a section mid rudder instead of adding to the tip. Taper the blades glass on both ends and build up the thickness to the outer side getting wider with each layer of cloth. Jake has a lot of pictures of glass work on his home page and might be able to give you more information on the process. There are a few repairs shown at www.epoxyworks.com if your not sure about how to go about always consult a boatyard for help.

OK, so i went out and spent some time with the "Wet Kitty" yesterday afternoon and took some measurements. After leveling the waterline of the boat(with the trailer jack), I put the level on the leading edge of the rudder. The leading edge of the rudder jutts forward of the rudder pin approx. 2". plumbing down from that point, the leading edge of the rudder rakes back approximately 5".
If I plumb down from the pin at the bottom gudgon, the rudder rakes back approx. 3" from that point. This measurement is to a point about 2" above the bottom of the rudder(so the bottom curve is not included in the measurement.
Just for fun, I pulled the bolt out of the rudder/ casting and moved the rudder forward to the point where it was plumb at the face(roughly, since the front is curved), and the rudeder had to be pulled about 1/3 of the way down and out of the casting.the curvature that , say, the 5.8 has at the top of the rudder is not there. Leading me to the possible conclusion that I shuld re-build the top of the rudder instead of the bottom, Thus adding the curvature that exists in the top of the 5.8 rudder.
Obviously I need to add pics. I will try again. Later.
I'm thinking of epoxying dowls into the top of the rudder. Possibly aluminum, removing material from the sides of the rudder where it goes into the casting, adding back FG to casting width, fill the center with epoxy or fg, cutting to new size sand paint and voiala, new plumb rudders(also approx3" longer)that can be adjusted back if needed.
It seems that the rudder extension will be less stressed up in the casting. Also thicker, and with dowels, should be very strong.
Any suggestions on the process?

That'll be a lot easier job because you wont have to spend so much time fairing. After a board dropped down while I was driving, I had to add 10 inches to a centreboard on my old Stingray which carried from memory 225ft of sail and I was able to stand on the tip for righting after repairs.
I used divinacell as my core because it was easy to shape, I ground back the edge I was joining a long way at an angle about half an inch then I put thick plastic on the workbench laid the board on it, pulled the plastic up to a bit bigger approximate shape. Filled it with wessystem and microfibles & cloth. Turn it over do the same on the other side. Then sand and fair it as you like bit of flowcoat jobs done.
regards

<a href="http://s426.photobucket.com/albums/pp349/azcat_photos/?action=view&current=rudder1.jpg" target="_blank"><img src="http://i426.photobucket.com/albums/pp349/azcat_photos/rudder1.jpg" border="0" alt="N5.7 plumb"></a><a href="http://s426.photobucket.com/albums/pp349/azcat_photos/?action=view&current=rudder2.jpg" target="_blank"><img src="http://i426.photobucket.com/albums/pp349/azcat_photos/rudder2.jpg" border="0" alt="wet kitty waterline - level"></a>
here are some pics...I hope [img]http://<a href="http://s426.photobucket.com/albums/pp349/azcat_photos/?action=view&current=rudder1.jpg" target="_blank"><img src="http://i426.photobucket.com/albums/pp349/azcat_photos/rudder1.jpg" border="0" alt="N5.7 plumb"></a>[/img]

[img]http://src="http://i426.photobucket.com/albums/pp349/azcat_photos/rudder1.jpg" border="0" alt="N5.7 plumb"></a>[/img][/img]

[img]http://[IMG]http://i426.photobucket.com/albums/pp349/azcat_photos/rudder2.jpg[/img][/img]

[img]http://[IMG]http://i426.photobucket.com/albums/pp349/azcat_photos/rudder3.jpg[/img][/img]

OK, I'M GETTING A LITTLE PISSED NOW. i THINK I BETTER QUIT. 1...2...3..4...