Cheapo Schilling rudder or stern thruster

I have heard that bolting some angle iron to the trailing edge of your rudder can give substantial close quarter control.

The tradeoff is some drag when the boat is at speed.


Does anyone know what ratio is used?* i:e - size of angle etc?

thx

On the trailing edge of*WESTERLY's*single foil-shaped rudder are fiberglass winglets about 2" in length angled about 30 degrees from the rudder plane.* These are common additions to conventional tug rudders where they are sometimes called "fish tails".*

There is no doubt that*they increase drag and improve close quarters maneuvering.* Coupled with a 45 degree rudder angle, the boat can turn in about 1.5 boat lengths.* Very handy.

Sorry about the pic size, this is the first one I've tried to insert.

http://www.mysticrudder.com/

Check this out. This guy and his boat are at my summer marina. He kicks butt in the handling department. Something to consider.

Thanks for the reply's so far.

My boat is a single diesel.

Attached pic shows the existing rudder.

I don't know if I really am trying to correct any problem, just always interested in better slow speed handling. The bit I know indicates the downside is probably minimal for this type of modification.

I am waaay to cheap to actually have a real Schilling or articulated rudder engineered and built.

I have a haul out coming up and thought I would try and experiment with the angle stock.

My rudder is fiberglass/composite. I plan to bolt the 90 degree angle to the uppper portion of the trailing edge of the rudder, this will be about 18" of material.

The angle stock is UHMW Polyethylene Angle, 3-1/2" X 3-1/2" Leg Lengths, 1/2" Thick. I was intending to trim the leg that will potrude (and deflect)*to 2" and router the newly cut edge to be a bit more fair. The bolts are nylon.


Mike makes a great point in that since this is an experiment, if the results are too erratic, I can just swim down and unbolt it, I do have a wetsuit.

-- Edited by bshanafelt on Thursday 27th of January 2011 06:11:24 PM

There is a LONG thread about the discussion or rudders corrections that I started almost a year ago called 'Boating Straight'. We have a single-screw that I added four inches to trailing edge and one inch to the leading edge (same ratio fore-to-aft as current rudder) to give it better low-speed control. It worked. However, I thought I had caused more problems than I solved because the boat wandered badly. Turns out that the entire steering system needed tightening. Bolts and mounts were all loose. She's still a little twitchy... BUT... I have no other frame of reference and no experience with any other boats of this size, SO, it could be I just don't know Jack.

I would consider a rudder length change as an option because it is a very cheap option. But don't rule out a stern thruster. You'll get a lot of flack from some people about stern thrusters, but I love mine. Would I like a bow thruster? You bet, but I feel better about my boat handling skills without having to rely on a bow thruster. I still have to think about the bow in order to dock smoothly.

Good luck.

I agree w Gonzo. When I was looking at boats I ran into one w a stern thruster and after a mental excursion about them decided I may prefer one to a bow thruster. Forget about prop walk and w a well submerged transom the stern thruster has no extra drag and works fine sitting still. They may even be easy to work on too.

When I rebuilt the rudder on Tidahapah I was at the time Superintendent Engineer for a small tanker Co here in Aus.
We had a Schilling rudder on a 36000 Tonne tanker at the time and happened to have the Schilling Eng visit us as the ship was in dock.
Whilst he was here he came and had a look at my rudder and we spoke of ideas to improve the lift and side thrust of my existing rudder.
His ideas I have since implemented.
Fins on the trailing edge at approx 135 deg. Full square aft rudder face and full under flow and over flow plates on the rudder to better direct the propeller water flow.
Increase the rudder port & Stbd angles to approx 40/45 deg.
I will post some photos when I am on abetter connection.
Works well without going to the full fishtale profile.
On a steel rudder it was a piece of piss.


*
Benn