daggerboard rudder

[rberrey]

I am about to start a build on a tristar 31, I would like to have a daggerboard rudder on it but there are only kick up and spade rudders designed for it. What are the chances I can just adapt a F-33 rudder onto it? rick

[PAR]

. . . Why?

[rberrey]

If I use a spade rudder I end up with a 30" draft and cant beach , with a kickup rudder I can beach and have a 19" draft. I want an inboard diesel, I've been told it will be less efficiant with the kickup. I thought a daggerboard rudder might be a good compromise. rick

[cavalier mk2]

Nice boat! You'll have to increase the transom thickness for a outboard rudder. Why don't you call Ed to see if he has anything?

[rberrey]

I wrote Ed about it a month or so ago, sometimes Ed is out of town and it takes some time for him to answer. I know all he has is the spade and kickup rudder designed for the 31. There is a picture of a daggerboard rudder on a 27'9" ( Quility Time ) on a web site, but I could,nt get in touch with the owner. I will use renicell E240 for the transom and increase the thickness, Ed told me I had to do that with the kickup rudder. rick

[cavalier mk2]

An F-boat rudder would work. You could also adapt a Newick rudder. They swing aft through a trunk and can be either spade or skeg depending on the design. Plans for many of Newick's designs are in the Mariners Museum and for a nominal fee they will print out what you request but you have to have an idea of what you are after because the collection isn't completely sorted through yet. Follow the directions on the museum website to contact the photography department and archives. A Tricia rudder for a skeg rudder or Echo 1 for a spade are a place to start. Those designs are 36 feet, Val 1 at 31 feet had a skeg unit as well.

[rberrey]

Thanks cavalier

[tspeer]

Originally Posted by rberrey

If I use a spade rudder I end up with a 30" draft and cant beach , with a kickup rudder I can beach and have a 19" draft. I want an inboard diesel, I've been told it will be less efficiant with the kickup. I thought a daggerboard rudder might be a good compromise. rick

The daggerboard rudder has the disadvantage that it doesn't kick back if you hit something inadvertently.

Does your boat already have a kickup rudder in a cassette? If so, does it have a fixed portion above the movable rudder blade like this?

The fixed portion allows the rudder to still be steerable when kicked back.

The efficiency of the rudder really has to do with how deep it is. I don't see any reason why a kickup rudder would have to be any less efficient than a daggerboard or spade rudder. You just have to make sure the structure and kickup mechanism is up to handling the higher moments of a deeper rudder.

The one drawback I've experienced with the kickup rudder and inboard diesel above is the rudder has a tapered planform with all the taper in the leading edge. Which I believe is the most hydrodynamically efficient way to do it. But it also means there is more area ahead of the pivot at the root, which is blown by the prop. The result is a severely over-balanced rudder when under power. You really have to stay on top of it, and can't let the tiller go for an instant when powering at speed. But it's just something to get used to and it's fine with the autopilot on.

[rberrey]

I,ll be building the boat soon so no rudder at all right now. The rudder you show would work really well but as a home builder it might be a bit complecated. My options are a kick up skeg rudder or a fixed spade rudder. The F boat daggerboard rudders now have a kickup version. I am told where the rudder is located distance wise to the prop will affect the efficiency. What I am looking at is which rudder is best with an inboard, and also allow for shallow draft. rick

[pogo]

Originally Posted by tspeer

The daggerboard rudder has the disadvantage that it doesn't kick back if you hit something inadvertently.

.

There is a solution, please look at pix and read posting 53.

Planing Catamaran!

http://img638.imageshack.us/img638/5861/02825g.jpg

pogo

[rberrey]

That is a nice looking rudder system pogo, how would I come up with the right size rudder for my boat, would I be able to use my daggerboard size to come up with the rudder size? thanks rick

[sandy daugherty]

Uwe Jaspersen, the South African builder of the first Gunboat, and designer of several serious go-fasts, came up with a unique rudder design. It is a daggerboard that slides up or down in a cylinder that fits a barrel in the back of the boat. It was featured in the Gun Boat 60 at the Annapolis boat show. He used the same concept in his Moxie 34 from two years ago. Elegant engineering.

This offers the advantage of placing the rudder exactly where it works best relative to a propeller, is fully balanced hydrodynamically, and uses no complicated rigging.

[jamez]

Crowther barrel rudder c. mid 1990s.

[sandy daugherty]

Wow! I am surprised. I guess it's true, "there is nothing new under the sun."

[cavalier mk2]

What did they use for bearings?