Using marine fiberglass (bondo product) and thicken epoxy I took the rudder of my CP16 and shaped into a NACA 0014 airfoil design. The results are amazing. The boat points better but more importantly it tacks better. In really light wind I would have to jibe through the wind but with the new rudder boat turns throught the wind without hesitation or stalling. The tiller is also much lighter in its feel. The project was also very easy to perform (a little time consuming but not difficult and no special tools were requied).
AWA
Post us some pictures! And congrats on your project!
I second the "pictures please" - I'd love to modify my original plate rudder to a foil.
Mike
AWA:
Did you use foam to achieve the shape? I know somewhere on this site, there was a discussion about doing just what you've done. I had the same plan to modify my 23 plate rudder into a foil shape but, as usual, I over-compliacted the process and never got started.
My latest plan was to bond foam to the aluminum plate, shape it to the NACA 0014 shape, fair it with bondo, sheath it in fiberglass set in epoxy resin, and finally finish paint it. I also wanted to incorporate a downhaul line to keep the blade down during sailing.
Is this what you've done? And, yes- any pictures you can post or even email 'em to me would be greatly appreciated! Thanks!
Bob23...still with a flat blade.
Unfortuneately I did not take pictures but here is how I did it. first download the shape of the rudder. this can be obtained a www.ppart.de/aerodynamics/profiles/NACA4.html. This should get you to the NACA 4 digit series generator. I picked a 0014 shape. I downloaded this and printed it. I then expanded that shape to the width of the rudder. I make a template of plywwod that corresponded to the shape of the airfoil. Its symetrical so just take the upper half shape. I used marine bondo epoxy for most of the shape. You may be able to use styrofoam as a filler but I did not and the finished rudder weight was not excessive. After getting the general shape i finished it with a belt sander. Before applying the fiberglass I drilled holes in the rudder and sander it with 80 grit sandpaper to ensure good adhesion. After the shape was correct I sanded it smooth and painted it with epoxy bottom apint. Total cost $50-75. You can get the bondo fiberglass and epoxy and thickener from west marine.
After reading about the efforts to economically improve the stock rudder, I decided to try the foam fiberglass method mentioned above. I used some closed cell foam used for packing that I found at work and a NACA 0012 profile to extend the rudder 3" farther forward to increase leverage and speed up tacks. I cut a piece of 1/4" luann underlayment 3"x the depth of the rudder and epoxied the wood the foam and the old rudder together.
(http://i193.photobucket.com/albums/z119/dscobra/DSCN0016.jpg)
I used a belt sander to fair the foam into the NACA profile by laying out the points of the profile on a piece of the same wood and using it to guide my sanding. After the foam was sanded, I thickened epoxy with microballons to a peanut butter consistency and laid fiberglass cloth over the foam. After saturating the exposed cloth with the same mixture, I waited another day and sanded both sides to the profile guide. I chose to add another layer of glass cloth to increase the stiffness and strength of the new rudder. When this dried, I faired it all and covered with barrier coat and bottom paint. Total cost was $0 and the boat handling improved far beyond any thing I would have imagined.......
(http://i193.photobucket.com/albums/z119/dscobra/finrud1.jpg)
(http://i193.photobucket.com/albums/z119/dscobra/finrud2.jpg)
Gents, congrats to you on a job well done. Amazing what a decent rudder will do!!!
AWA,
Thanks for the information.
Looking at the NACA4 site, The data produced is essentially (X,Z) (2 dimensional.
I plan on using a 3D NC based bed and spindle to cut instead of a belt sander.
Have you found any site that you can determine 3D coordinates?
I will take this data and build in a taper to the bottom point.
====
I do know that many rudders are made with a center plate frame that is cut with pockets
to reduce the weight and then using epoxy and foam, the two outer shells are cut ad then glued onto
the steel frame.
Next, fiberglass cloth and epoxy are added with epoxy filling the weave.
Final sanding and then paint because UV and epoxy do not play nice together...
PLAY TIME!
Thanks!
Bob Condon
Bob - Excellent idea. I am a teacher on summer vacation so I have some free time right now. I teach high school students how to use ProEngineer Schools Edition in my engineering courses. Maybe I can create a model for us? ProE Schools Edition can export to a lot of formats. If I can find time to model the rudder halves, which format would you need to import into your NC software?
The 3D file types supported in Cut3D are
STL STL Mesh files - binary & ascii
3DS 3D Studio - binary & ascii
DXF AutoCAD 3D DXF
OBJ Wavefront
SBP ShopBot Digital Probe files
TXT MaxNC Digital Probe
WRL VRML
X DirectX
LWO LightWave
V3M Vector Art 3D files
The features indicate that they support ProEngineer as a design package.
What usually happens is that a design would be done in another design package,
and I would bring it into Cut3D or Aspire and build the cut file from there.
I would also be doing this for a CP19.
The rudder front to back is 12 "
The rudder from bottom to the beginning of the swing is 24" (exposed air foil area)
the distance from the swing to the top is 12" (the support above the air foil)
Could be lots of fun to play with. If you send me one for the CP16, I would be glad to cut
for you ... and maybe make available to others
BC
Bob,
Is the original rudder for a CP19 a blade like the CP16? How think is the blade? Can you send a picture of your rudder so I can be sure that I understand your measurements? Else, can you make a sketch and scan it? My email address is in my profile. It is supposed to be a stormy day here in the Minneapolis metro tomorrow. Looks like a good rainy day project.
Steve
Bob - I modeled the OEM C-16 rudder plate and designed port and starboard foils accordingly.
Here is a shot of the assembly...
(http://i556.photobucket.com/albums/ss5/sullrich/C-16%20Rudder%20Foils/C16FoilRudderAssembly-Right.jpg)
More images at: http://s556.photobucket.com/albums/ss5/sullrich/C-16%20Rudder%20Foils/
Total width fore to aft is 13" | Leading radius = .75" | Trailing radius - .25" | Widest profile = 1.5"
As I see it, the only difference between the C-16 and the C-19 will be the length of the extrusions. Total width can be modified for longer fore or aft trailing edges but I just didn't like the way it looked. Any part of the profile can be modified any way I like for that matter. Let me know what you think.
Steve
The 19 has the same style and profile but scaled up from the 16's rudder from the factory and it is a thick 5/16". What ever that is in mm.
I weighed just the blade for my 19 once at I think 16 pounds [I forget]. Which is [I think] was 3 pounds less then my IdaSalor blade but once in the water the IdaSailor blade gains an advantage as it has a tendency to float just a bit and puts a few pounds less on the transom's rudder casting. To be clear both blade will sink like rocks so don't let go.
skip.
Skip - Thanks for the update on the thickness of the C-19 blade. I'll tweak the foil profiles I'm designing for Bob.
Steve
I'm curious who will next do the modification and remove the central portion of the aluminum blade, for weight savings, leaving a skeleton to form the foam bond to.
I find it conceivable to reduce the weight by 6 or 7 lbs, fill the space with foam, and possibly have a floating blade once it's glassed over! That would make the rear heavy CP16 sail better, IMO.
Also to note, the factory IDA rudder assembly sold nowadays seems to have a longer rudder than what is being made by individuals. I can do some measuring if that will help someone make the best rudder possible.
Rudders that I have seen that are foamed/glassed have the structural
middle in steel and not aluminum. I think this is a strength issue and probably
a dissimilar metals issue - After my vacation, I hope to cut the foam on a N/C machine
with foam and try a foil....
My rudder knicked a rock last week and was tilted up a few degrees, I didn't notice it when it happened and we were having a heck of a time going to wind. I finally noticed the rudder was up a little, pushed it back down, and windward performance increased greatly. I'm a complete novice in terms of sailboat design, but could adding another inch or two onto the rudder when you build the foil improve the performance even further? Is the Ida rudder a few inches longer than the stock? Could that help explain the increased windward performance people report with the Ida?
I became tired of 'locking down the rudder bolt after a rudder kicked up from seaweed, the bottom, and what have you.
And for years I kept thinking of ways to keep the IdaSailor rudder down and a wee bit forward to take advantage of it's balanced rudder traits....I don't like to fight a hard tiller with ANY of the rudder kicked up.
So I drilled a hole clean through the rudder casting and the alum blade stabbing my plastic foiled rudder blade and bolted in a snowblower sheer bolt.
After all the rudder is behind and at about the same level as the keel on my 19. No big deal. I have hit rocks before and I have my 6mm armor alum plate 'Keel Boot' glued to the bottom to save my glass.
Reversing the hull with the engine makes chopped broccoli out of the stuff on the prop.
skip.