azcat,

All nacra rudders and casting hardware were the same for that vintage and should allow you to adjust them so that the center of effort on the rudders gets right up to the pivot line of the gudgeon pins. It is entirely possible that the holes in your rudders for the pivoting points have been drilled in the wrong place. If your rudder head looks like other Nacras, I wouldn't go reshaping it. I would instead, find an opportunity to lay your rudder atop another known-to-be-good nacra rudder and compare the shape of the top and the pivot holes to figure out what difference is causing the problem.

Redrilling a pivot hole will be easy.

on second thought, looking at this photo:



your rudders appear to be raked too far forward. Are you sure you have weather helm or lee helm? If you have weather helm, when you let go of the tiller, the boat will want to turn to head to wind. With lee helm, the boat will want to turn away from the wind into a reach (and further). The way that looks, with them raked so far forward, you probably have pretty severe lee helm. The way we traditionally measure rudder rake is to use your level like you have shown, but hold it flush with the transom of the boat. Draw a line on the rudder straight down from the transom and measure the distance from the leading edge of the rudder to the line.

If you look in the bottom of your lower aluminum casting, there should be a threaded hole with a large plastic screw in it. This is to limit how far the rudder goes down when it's all the way down. I bet you don't have the screws in there.

The head shape on that rudder does look odd though - it's as if someone cut out the head so the rudder would rake further forward.

Notice in the pic that the front of the rudder is extended forward past the casting about 2", so it extends under the hull.
also, notice where the pivot bolt hole is in relation to the casting. If you look closely, you may be able to make out a line that I drew on the rudder while in it's full down position. i traced the hole in the side of the rudder casting. Also notice that the rudder is pulled downward about 4" to get it to rock forward enough so that the rudder is plumb along the front edge. you can see through the rudder casting above the rudder head.
There is still a bungee attached to the top (popup)so I can't pull it backward easily. I just held it down and held the rudder forward far enough to get it plumb. If these are stock rudders, they may have intended for the rudder to extend under the hull to minimise stalling. Just a thought.
Look very closely at the shape of the rudder behind the level, you can see where it jutts forward.

Karl, this is the full down position. I can only adjust them back more. There is no curvature in the rudder head to match the angle of the transom, allowing the rudder to come forward to the plumb position.

apparently the boardless 5.7 has the same rudders as the 5.0, and 570

have you had a good look at pics on the web of these boats?

left most pic here
http://www.inland-sailing.com/New_Boats/NACRA570.htm

http://www.sail4u.be/Nacra%205.0%20occ1.jpg

That top link is the 2nd generation nacra rudders - the butterknife that came out in 2004.

i dont know if this helps but on several rudders i have seen there is some play... you need to apply a little pressure backwards to simulate the pressure of water pushing it back to see the actual position it will be when in use

Hi Azcat,

I'm not sure if my knowledge /experience is helpful to you since my personal experience w/ NACRA/Performance products is limited to the P-19 ... but here is what I've learned

I suspect your rudder blades are the same as the blades retro fitted to the P-19 replacing the short square tipped (bottom) blades origonally used on the P-19. They do look identical in the pic's.

First, I have had (4) new blades split from the rudder head (top) down due to "sheer" loading generated internally from blade deflection. As the blade is loaded due to side-slip the blade deflects in a curve ... one side is in compression the other is in tension ... this results in internal "sheer" loading that splits the blade from the top down. I fixed the blades by using (20) 3/8" wooden dowels installed w/ epoxy from side to side ... sanded off the gelcoat .... using 2-layers of 4"wide Fiberglass tape I sealed the seam and then reskinned the rudderhead completely. I have had no more problems w/ the rudderblades. So you have a good idea w/ the dowels but I think it solves a different problem

Now I have fixed several centerboards and rudderblades that have "met the road" ... ie:having been dragged down the highway. The repair process basically startes w/ hollowing out the inside of blade so you can make and install a new inner core first. You can make a new core from wood (I like cedar)or foam. Shape appropriately and install into hollowed out section ... make sure the new core is "bedded" well using epoxy w/ thickners. Next taper the existing outside skin for 4-6" ... then reskin and fair as required.

Now it is counter-intuitive but the internal loading is least at the bottom of the blade vs's the top as the blade acts as a lever arm/cantilever and the internal loads are greatest at the head.

Now, w/ all that said I would suggest a different path to a solution ... do you have a "new" spare rudder blade? If you don't I would purchase one from NACRA as I believe they come w/ the holes located and drilled properly in it. Or contact them and ask if they could provide you w/ a template/tracing of a new blade properly locating the holes. I would compare the new to the old ... fix the old and save the new. It is always good to have a spare ...
just think about how much $$$$'s you have invested in a weekend just to have it wasted due to a broken boat on Saturday afternoon and no replacement parts. (I always carry an extra rudder blade w/ me for whatever boat I'm racing that weekend)

I'm wondering are you trying to fix something the wasn't broke??? I asked this as you are comparing (you friend's) daggerboard boat to (your) non-boarded boat ... how was the helm on your N5.7??? If it was neutral or had slight weather helm you are OK. It has been a long time since I "tuned" a Non-boarded boat ... but if I remember correctly it is a balance between mast rake and rudder blade rack to get the proper feel on the helm. The method Jake, Karl and others suggested for using a straight-edge to check the rudder rake is the method we all use. Unfortunately the measurement is unique to each model boat due to the angle of the transome and measuring point locations so none of us can give you an actual measurement.

Oh, I did have to "notch" my rudder blades slightly to get them to lock down properly as they were hitting the corner of the transome and bottom of the boat. But now after adjustment/fitting my P-19 has a neutral helm to weather and downwind under spin w/ proper sail trimming it is neutal also. So there is a sweet spot ...


Good Luck and Happy Holidays
Harry Murphey
H18MAG/P19MX w/spin

Good pic Erice.
My rudders will not come even close to that far forward as shown in the first pic of my boat.
In the second pic, the rudders are un bolted and pulled forward 5" and down 2". I think that rebuilding the rudder head is the best option. I dont think I want to mess with the bottoms It might be a problem keeping the sides equal. I would think that a little bit of difference in contour at the bottom of the rudder(side to side) could make a huge difference at 18mph, hydrodynamicaly speaking.

Now, as I said in an earlier post, the leading edge of the rudder jutts forward of the rudder pin approx. 2". How will that effect the center of effort on the rudder itself if I put that leading edge plumb? Will it make it squirley? I guess I should build them plumb and I can rake them back with the adjuster screw. It may just take some T&E and R&D to get it right.
I am thinking of oak dowels for the head. I will get some pics when I do it and post them.... on second thought...

I just found this shot of a 5.7 rudder. The head is shaped completely different than mine. Mine must have been replaced at some point.
I will need to re-shape the head of mine. I re drilled the pivot holes so that they will come foreward, and will try to get out this weekend to try them out. I had to pull them downward 2" and they dont contact the top of the casting, so I think it may put a lot of stress on the casting if I dont extend them.

I wouldnt cut my existing rudders and try to extend them, you are asking for trouble. I've done a fair amount of work with composites and unless you've got some experience, this is going to come out with a less than perfect blade. Plus using wood it asking for trouble, it will rot over time. You will probably get Red oak dowels and they wont last. I would start new, and keep your exising boards in one piece. If you can find some broken ones, or a second set, then experiement on those.

I have a set of daggerboards that I made out of foam/epoxy and carbon that I dont want. They would be perfect for your project. They need some fairing, and you will need to cut our your own profile, but they are plenty long enough. And if you dont like your new boards, you can always go back to the old ones.

Dont cut the existing ones up.

Send me an email if you are interested wjvining at yahoo

Bill

I sent you a PM with my email, did you get it?

azcat, in this thread I can't tell if you are experiencing lee helm or weather helm, or just concerned about being "different" in regards to how long your .... rudders ... are. (haha)

Any, pls send email and I can send you tracing of my 5.7 rudders shape & pivot hole location.

One thing I did when I first got the boat is to change rudder angle to be more under the boat, it balanced the helm quite a bit. Basically i shimmed out the upper gudgeon with two washers, left lower gudgeon in same place. Much easier than modifying rudder blade itself. but, my rudder blade itself is the style with a cutout/projection, so it kind of project forward under the rudder casting about 1-2".

I also have a spare rudder blade (mystery brand) that I was experimenting with how to modify to make a higher aspect ratio blade. never finished

Jim

The approx length of a nacra 5.7 and 5.0 rudder is 35 1/2 inches,
compared to approx 31 1/2 inches for the 5.2 5.8 and 6.0.
What is the length of the rudders that you have with the boat ? I am quite curious to know.
Hope that this may help.

I'll have to measure my 5.7 rudders when I get out to the boat this weekend.
But I have two spare rudder blades at home, for my 5.5 and I just measured them at 35" long.
From manuals, the 5.2/5.5/5.8 & 6.0 all have the same rudders.
So, I don't know about the 31" rudders, that seems real short.

My 5.7 rudders are longer than my 5.5 rudders, but mainly they are shaped different, as azcat mentions, they "jut" forward underneath the casting. This rudder shape allows it to feel more balanced, even when it is heavily loaded. i.e. even when heavily loaded from the side, it can feel more neutral since more of the area is closer, or even in front of the pivot line.

The main issue I have with 5.7 rudders is indeed the length. It would be great if the rudders were longer. Issue is that pointing a 5.7 involves putting nose down, to reduce transom turbulence at minimum, but more so to use long pointy hull to its advantage.
The long hull length (compared to 5.0 which supposedly has same rudder length) combined with the "height" of the rudder casting above the waterline(skeg + hull shape compared to 5.2/5.5) means that sometimes very little area of rudder is in the water. Sometimes this area is too small, and it can stall out.

I have seen 5.7 (and 5.0) with both kinds of rudders - plain "round" rudders, and I've seen 5.0 & 5.7 with rudders of kind with shape that juts forward. I have a 1987 model 5.7, it has style that juts underneath. Pretty sure they are original, I bought from original owner.

Jim Casto

I noticed Nacra lists the Nacra 20 style second generation rudder as standard on the 570. Why not upgrade the whole rudder system castings/arms/crossbar and rudders. They're clearly longer than the old style.

money? vs time?

Jim, If your rudders jutt up under the hull then they are probably the same as mine. I recently removed the pivot bolt and pushed them forward till they were about plumb, and re-drilled the pivot hole. I can hold onto the stick with one hand now when on a reach. Actually, I think I need to push them back a little bit because in some conditions I end up with lee helm. This power steering is great! They were raked back way too far before.

I also am working on some longer rudders. When finished they will be 48" long. I beleive the current rudders are 39". When the crew moves forward, it dosent take much to stall them. I hope they will be stiff enoug at that leingth, Epoxy foam core W/1 layer carbon in epoxy and one layer glass in epoxy. I dont think there will be any more stalling issues. I also am also hoping that they will take some side loading and act as a dagger. I wonder if tucking them up under the hull like the old rudders would be a good idea? That may help take some of that load.

Good to hear an update.
I also sent you a PM.
I'm looking forward to sailing this weekend, we have a "frostbite" race series, but I'll probably get drilled baby drilled for calling it "frost" since I'm in Austin TX & the forecast for saturday is 60s. Does it count if it was 28F last night?