CP16 rudder modifications...

[mayrel]

We just purchased an 83' CP16 completely reconditioned, but stock.  I know the subject of rudders has been extensively explored on this forum.  Most have decided to purchase the upgraded rudder blade and report amazing results; specifically less weather helm.  I'm not an engineer so I can't speak to weather helm in terms of what causes it and how to eliminate/reduce this effect.  Looking at the upgraded rudder blade, it seems deeper and slightly wider.  Obviously it has to be to fit over the existing rudder blade.  The cost for this foiled rudder is $295 plus shipping, and it may well be a good investment?  However, I can't help but ask a simple question.  If you had a new rudder blade cut from aluminum which was slightly deeper and wider, wouldn't this improve the weather helm issue?  And if you filed the leading/trailing edges to make them somewhat rounded, wouldn't this also help?  I ask these questions based on my limited experience with a sailing kayak I put together.  I modified the stock rudder blade by simply making it slightly deeper and wider, it did make a huge difference in handling/performance.  This is why I wanted to ask the question, if a foiled rudder blade deeper and wider helps, then surely a deeper and wider simple aluminum blade can't hurt?  It might be a little less expensive too?  I did see one of these rudders for sale in the classified section.  I wonder why?  Early thanks for any input.

[Craig]

Welcome! The rudder in the discussions here is a foiled rudder by Ruddercraft, that has a hydrodynamic shape similar to lifting surfaces on aircraft. In short because of the foiled shape it is more efficient and will stall(lose lift) at a higher angle than a plain flat plate. Because of the efficiency, less helm is needed in any given situation. Less helm = less drag and less physical effort. The replacement blade does not fit over the existing blade but replaces it using the existing rudder stock. They also are available as a total replacement system which includes the rudder,a lifting/lowering system, rudder stock which uses existing mounting hardware and a new tiller. A larger flat plate will not make much difference except to add drag. Having had both, I can attest the foiled rudder(cost aside) is well worth adding! As to the one for sale, perhaps the seller upgraded to the complete system. I don't know of anyone who has gone back to the original flat plate.

[nies]

The Ida rudder is like getting power steering on a car, $295 plus shipping is cheap for what your getting, I would never go back..............time and money will be wasted trying to reinvent the wheel ..........just go for it and you will never be sorry.................nies

[NateD]

Most of the "power steering" effect comes from "balancing" the rudder, moving some of it's surface area forward of the turning point (http://www.glen-l.com/weblettr/webletters-4/wl38-rudders.html). If you just want a rudder that has less helm, you could weld a inch or two onto the leading edge of the rudder (or play with your sail configuration). The actual performance (pointing ability) improvement comes from the foil shape. You can use foam (or wood) and fiberglass to make your own foil over the existing rudder, which will cost about $40 to $150, depending on the materials you already have on hand. Or, as you know, you can purchase one for $300+ that will be ready to go out of the box.

[carry-on]

As I recall, the member who was selling the IDA blade had decided to buy the full assembly. I think the blade had never been used, but was unpacked and could not be traded.
Don't know of anyone who regrets getting the foiled rudder. One plus I've noticed is the improved response at very slow speed when docking or approaching the trailer to retrieve the boat.   

[Salty19]

Great advice here learned from years of experience.  

If you want a real foiled rudder that will help performance you have three options:

1. DIY.  That would be take your rudder and either glue foam or wood to it after making a leading edge of about 1 1/2" width that will bring the leading edge forward of the stock location. Shave material to exact Naca 0012 foil shape--if foam maybe a hot wire jig would be best (or shave/sand), if wood, then use plywood and a nada 0012 foil template with 1 1 /4" chord and carefully plane and sand down to shape, following the layer lines in the plywood as a guide to progress.  Then fiberglass and epoxy it all, fill, sand, prime and paint or whatever finish will last.  Check the DIY forum area for more info, if you are handy this could be a really fun and rewarding project for not a lot of money.

2.) Buy and $299 IDA rudder.  This will replace your rudder entirely, it will not slide over it. It does have a metal backbone covered in HPDE plastic, cut to Naca 0012 shape. You still have to tighten the lug down when the blade is all the way forward and use a line to pull it up when needed.  If your tiller is in poor shape and needs replaced, I can vouch for the excellent quality of their tillers.

3.) Buy the IDA Full rudder assembly.  It's pricy but it's pretty nice, replaces your rudder assembly.   Like Craig mentioned it lifts all the way up and goes all the way down with a pull of a line. It has a piston-cylinder assembly that keeps the rudder forward, so if it hits something, it will kick up, then push back down.  It releases pressure enough to pull it up, then when it's up, the assembly helps to keep it up.  No locking it down like the stock or option #2, but I do tie it off when trailering.  A kicked-up rudder is an unhappy rudder.

This is a CP19, but we had the same one on our old CP16, just a smaller version of it...really like this setup.

[capt_nemo]

mayrel,

With regard to "weather helm", recommend you try this simple check first before doing anything to the stock metal blade rudder.

If you normally just release the lever and let the rudder rotate down into the water before retightening the rudder lever, do so either in the water or while on the trailer BUT DO NOT RETIGHTEN THE LEVER!

Now, push against the trailing edge of the rudder below the pivot bolt. Did the rudder move further forward to a STOP?

If it did move forward, even slightly, it was not in its fully forward position and the resultant increased force on the surface area aft of the rotating pins translates to INCREASED WEATHER HELM especially when wind and/or boat speed increases.

Just remember, after releasing the tightening lever to drop the rudder, lean over the transom, reach down, and with one hand push the rudder "Home" to its fully forward STOP while tightening the lever with the other hand. You'll be glad you did.

Although photos are of a foiled replacement for a metal blade rudder on my Sun Cat, focus on the lower tip and leading edge of the rudder. First photo is "gravity" position of the rudder and second is with rudder pushed fully forward to the STOP before tightening lever. Toggle back and forth between photos to appreciate the difference.

capt_nemo

[mayrel]

Thanks to all that responded.   Ruddercraft offers two options, complete rudder system and blade only.  The blade only option that was listed for sale may have been worded differently, but I understood it to say the foil slipped over the stock blade and was bolted in place.  I do see Ruddercraft shows a complete rudder blade; remove existing plate rudder and install the Ruddercraft blade.  I realize $300 may seem worth the improvement to performance, but I still wonder.
I spoke with an experienced CP16 sailor who claims the existing stock rudder works fine.  His explanation goes to the additional wetted surface of the foiled blade, which creates more drag, therefore the overall improvement to performance is insignificant.  it may "feel" better and in fact steering reaction may be improved, but sailing performance is not significantly improved. He's used the Ruddercraft rudder.
I also asked about the difference between the CP16 MKI and MKII, specifically on the MKII/III moving the jib forward 11 inches, making it slightly larger and reducing the size of the main.  Again he explained there is no significant difference in performance; it's primarily in the hands of the experienced skipper that makes the difference.  He emphasized mastering light air sailing of the CP16; he gave me some pointers/techniques to follow.  Sailing in heavier conditions again, depends on the experience of the skipper.  He pointed out, the CP16 was not designed nor intended to be a fast sailboat.  It was designed to be a very safe, forgiving and simple sailboat.  I think the design is in fact a winner for these reasons.  I have several years experience sailing small boats; Montgomery 17 and 15, Crawford Melonseed Skiff,  CL14 and SeaPearl 21.  I found all these boats to be well designed and very enjoyable to sail.  Obviously every boat is a compromise, each may have individual modifications to suit the owner, but they all sail well.  We're not so interested in speed, but if there are any design flaws which can be modified(example, the Ruddercraft rudder)which will make a significant difference, I'm ready to do what has been proven to be worth the effort/expense.  Please understand, I haven't sailed our CP16 yet, so I don't know what to expect, hence the reason for asking the question to other experienced CP16 owners.  I haven't read anything stating there are design flaws with this boat resulting in failure.  The only thing I see reported as an overall improvement to performance/handling is the rudder upgrade.  And there are those who use different head sails depending on their sailing grounds.  Again thanks for all the responses...John