Articles:
Something Like a Foil - AKA the "Bill Board"
Geoff's Rudder
The Story Of The Rudder
The sequel to the rudder
The Joy Of Leading


Rudders
The rudder on your boat is a very important component, and seems to be the 2nd biggest problem new builders run into when building PDRacers. There are many types of rudders that can be made, everything from a simple board and stick, to a fancy kickup with tiller linkage & counter weights. The easiest thing of all to do is borrow a rudder from another boat, or buy a used rudder from ebay. You can have new custom rudders made (or unfinished kits) from Bill at TCBoats.com, he is a custom boat builder and can make anything you need.

Rudder Size
For the size of the rudder, I haven't seen very many references with calculations on exactly how big they should be made. The only rule of thumb I have heard, is that the submerged area of a leeboard needs to be 4-5% of the sail area, and the submerged area of the rudder is half the size of the leeboard. My rudder blade is a little bigger than that. The blades are best made from solid wood, about 3/4" thick. If making from plywood, the same 3/4" side is good, or you can laminate 3 of the 1/4" pieces together.

The rudder is composed of:
Stock - this is the main body of the rudder that is attached to the boat.
Blade - this is the part of the rudder that goes into the water.
Tiller- This is the stick that you wiggle to steer the boat.

The shapes of the rudders vary, some are deep and skinny (high aspect) blades, while others are shallow and fat barn door (low aspect) blades. Naturally you would think that a low aspect blade would have less resistance when going thru the water because it has a shorter leading edge. This is NOT true, strange as it may seem, a high aspect blade is more effecient in the water. A high aspect blade also has the advantage that when you are in choppy water, as the boat bounces up and down, a longer blade will still be in the water, where a short fat blade will come out and you will temporarily loose steerage.

And for shaping the blade, the leading edge should be rounded, and the trailing edge should be feathered out like a knife blade. If you find that your rudder hums while you are sailing, then shape the aft edge some more, and/or tighten your pivot bolt.

Gerard Mittelstaedt's sandwich rudder, excellent essay.

Jim Michalak's one sided kickup rudder, a very simple design with a pivoting blade.


"Sandwich" Kickup Rudder
Making a rudder with a blade that can pivot up is very desirable. It is difficult to judge how deep the water is, and when you are sailing, you are often paying attention to other things. The best type of kickup rudder is a sandwich type, it has a blade that is sandwiched between 2 other boards.

This rudder is from Ken Abrahams' boat, he won the first race series, and is an excellent boat builder.

If you run over the shallows, the blade can pivot up.

Notice the bungee cord. This is a simple method of holding the rudder blade down or up. Figuring out where to mount the bungee is simple, all you do is put the blade half way up, then find a place to attach the bungee to both the blade and the stock, so that the bungee crosses directly over top of the pivot bolt.


Gudeons and Pintles
These are the hinge parts that hold a rudder onto your boat. The part on the boat is called the gudgeon, and the part on the rudder is called the pintle. Most of the time the pintle has a pin on it, and the gudgeon has the hole, but some times it is the other way around, and sometimes a removable rod holds both together.
There are many types of homemade ones, but I strongly suggest you purchase them. A good source is DuckWorksMagazine.com, click on the store link. The founder / editor is Chuck Leinweber, he built hull #8 "ACME". It is important to be able to put the rudder on and take it off while in the boat. Rudders have a tendancy to bounce up and down, so a cotter pin or pivot stopper block to hold it down is also nice to have.

Angle Iron
This is a very strong and simple set to make, both the gudgeons and pintles are simple pieces of angle iron. Often made from aluminum angle instead of iron, so it won't rust. You put a piece of all thread rod thru the middle, or a long bolt or shaft.

Door Hinges
With these, you have a block that spaces the hinges off the transom of the boat, so the rudder can fully pivot from side to side. Like it is, the stock is permanently attached to the boat, so for transportation you would remove the blade, or pivot it up for trailering. You can remove the hinge pins and replace them with a smaller shaft that is removable (such as cotter pins) , so you can seperate the rudder stock.

Fence Post Hinges
Phil Keck mounted his rudder with fence post hinges, and at one point a wave lifted him in shallow water, then slammed him down on his rudder which is just about the worst trauma that you can do to the gudgeons & pintles. His rudder survived just fine, as if nothing happened.

Bend Your Own
Ken Salvage used a peice of 1/8" x 1" alum FB (hammer bent) and 1 length of alum 1/2" Dia tubing along with some scrap wood 2X2s and misc Hardware. It seems to be strong as the devil and he can get 180 degrees of travel as well. Also mounted Alum FB on the top of the rudder blocks as well.

Cary Hinge
This is a simple innovation with 2 key components. First is that instead of using metal hinge parts, the Cary Hinge uses nylon webbing or seat belt strapping has the hinge. The strap is epoxied inside the rudder lamination layers, and also between a wedge shape. Second is the tongue and groove, so you can slide the whole assembly in and out. You could adapt another hinge with the same tonge and groove. The photo is of Rob Rohde-Szudy's rudder from his Piccup Pram which he used for 4 years. You can see many great articles by Rob at DuckWorksMagazine.com This rudder design was originally published at Jim Michalak's site.

Eye Bolts
I have seen this method all over the net, seems like lots of people really like the idea of using eye bolts. I think it is so popular because it is such a simple concept, you screw a few eye screws into your rudder stock and a few eye bolts into your transom, then run a big rod thru them. This is also the design I have heard fails the most. The eye screws don't seem to be able to take the high force put on that area of the boat.

Tillers
A tiller can be as simple as a stick that you bolt on the side, or a Y shape that bolts over top of the stock. Since the PDRacer was designed for you to sit way in the stern, your tiller should be a short one around 18"-22" long. Before laminating up a really fancy one, you should experiment with a simple stick to find the proper length for the hull configuration you make.

Hiking Stick / Tiller Extension
There are many commercially made tiller extensions that have universal pivot joints, telescoping handles etc. Most of these sticks cost more than your entire boat will. The simplest of all hiking sticks is a simple slat, that is loosly thru bolted to the end of your tiller. The sunfish comes with this same type of hiking stick, as do a number of other small boats. You can add a bungee or velcro strap to the tiller, so that it can be held in place when not in use. Some people mount them on the top, some underneath - it is up to you.

Rudder Leash
Because rudders break so often, it is important to have a leash from the rudder to the boat. If the rudder breaks off, it can quickly seperate from the boat (either the rudder or the boat blows away), and you will have to make another rudder.

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Copyright © 2003 David Routh, All Rights Reserved

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