Discovery #1 - Rudder Shade Tree Engineering Project

[Pacman]

As you know from previous posts, I had planned to test a "balanced" rudder blade against a stock rudder blade to evaluate the effect of adding 2" to the leading edge.

Mark sent me his stock blade so I would have a standard for comparison.

However, I just noticed that his blade measures 26" from the pivot hole to the bottom while my blade measures 31.25" from the pivot hole to the bottom of the blade.

My boat is an early 1976 model, sail #217 so I think that ComPac must have shortened the rudder blades for newer boats.

It would be a big help if some other members could measure their rudder blades and post the following information:
1. distance between the pivot hole and the bottom of the rudder blade
2. year of manufacture
3. sail number

Right now I plan to sail the boat with both blades, long and short, back to back on the same day to see if there is any significant difference in their performance.

Thanks,  

Dave

[sailen69]

Packman,

I got out to my boat in storage today and took a look at my rudder blade.

1.  The distance from the bottom of my rudder to the bottom of the pivot hole is 25 15/16 in.  The pivot hole is 3/8 in.

2.  The year of manufacture is 1983

3.  The sail Number is 2046.

This sounds like an interesting project.  Good luck and take pictures for us.

Rich

[itsmark]

While deeper rudders might perform better than short ones, I don't want a rudder that extends below the shoal draft keel.  When I run aground, I don't want to break off the pintles and gudgeons.

[Billy]

While deeper rudders might perform better than short ones, I don't want a rudder that extends below the shoal draft keel.  When I run aground, I don't want to break off the pintles and gudgeons.

3 words.....

Kick Up Rudder

these are great b/c it will tell you when you are about to run your Keel aground, before you actually run your keel aground. Happens to me all the time. I can feel the tiller start to shake due to the rudder dragging and I know it is getting close. Then I can turn the boat and don't get stuck or cause any damage to the keel.

Check out Com-Pac's website. The Horizon cat video shows how they keep the rudder down. It's actually pretty sweet.
Here is the link, watch at 1:10 secs
http://www.com-pacyachts.com/com-pac-theater/#compachorizoncat

[brackish]

While deeper rudders might perform better than short ones, I don't want a rudder that extends below the shoal draft keel.  When I run aground, I don't want to break off the pintles and gudgeons.

3 words.....

Kick Up Rudder

these are great b/c it will tell you when you are about to run your Keel aground, before you actually run your keel aground. Happens to me all the time. I can feel the tiller start to shake due to the rudder dragging and I know it is getting close. Then I can turn the boat and don't get stuck or cause any damage to the keel.

Check out Com-Pac's website. The Horizon cat video shows how they keep the rudder down. It's actually pretty sweet.
Here is the link, watch at 1:10 secs
http://www.com-pacyachts.com/com-pac-theater/#compachorizoncat

Looks good in theory but doesn't work all that well in reality, at least on the new foiled rudders that have that same handle.  You have to add a very heavy shock cord to keep that handle tab from kicking out.  Depending on the point of sail, it will also slide out laterally in one direction or the other and the shock chord won't hold it in that direction.  I've been observing mine to see what I can do to modify it so it will stay put but still kick out safely when grounded or it hits a solid object.  Another concern, the rudder can't hit the outboard prop when locked fully down, but can if it kicks up partially.  Learned the hard way after a grounding.  A little marine tex, good as new.

[capras801]

Pacman,   The distance on my original rudder from bottom of pivot hole to bottom of rudder was 26 1/8". New IDA Sailor Rudder is 27". It is a 1981 with Sail No. 1642. Hope this helps.

[Pacman]

Good points.

To protect the longer rudder I have decided to install my rudder using a rod that is 9" longer than the the distance between the gudgeons instead of the OEM bolts so the if my boat falls following a swell and the rudder contacts the bottom, it will simply ride up on the rod. 

It is a cool idea but it is not mine.  I saw an old Beetle Cat with this arrangement and it was obvious that I could do the same thing on my C 16.

Regarding the longer rudder, I like grounding the rudder before the keel so I can bear off before grounding as Billy describes in his post above.

It is starting to look like my ideal rudder will be longer than the newer ones for two reasons:

It seems to perform a bit better than the shorter newer rudders and, with the Beetle Cat mounting system, it will act as an early warning system for shoal waters without the risk of damage.

My next effort will be to see what happens with 2" added to the leading edge of the old longer rudder.

This is turning out to be a very interesting experiment.