Kick up Rudder - downhull?

I have understood 'cassette' to be a vertically-adjustable blade held by a cheek. Instead of pivoting, the blade can pop out the back if grounded.
Interesting collection of ideas here, also shows the third gen Sunfish rudder cheek/spring system that the above video is trying to replace:
Kick-up Rudder Strategies https://smallcraftadvisor.substack.com/p/kick-up-rudder-strategies

 

You can build the rudder cheeks from plywood shapes glued together much easier than with solid wood, with long screws / bolts holding the sandwiches together once glued, or even metal fabrication can be used. Aluminium cheeks seen below.

This is the rudder of a 16' dinghy for the bungee / shock cord explanation.

Yellow shock cord (strong) with whipped eyes both ends, anchored on the blade directly, nesting in a perimeter groove around the blade top, through a pulley secured at the tiller pivot, pulled and held down with a 2:1 pulley setup, and cordage secured in a V cleat on the tiller, out of the picture. It can kick up easily upon grounding, but holds itself down well in most cases. See also the blue 2:1 uphaul with no bungee, held in a V cleat on the other side of tiller; hole in top gudgeon pivot pin; and R clip on a cord, to prevent the rudder being lifted off the pins, which is a bad thing to happen; small stopper bolted on rudder (bottom) to stop it at the right down angle; pivoting white plastic block under the tiller to lift it up a bit if needed, when elbow gets sore after hours use at same angle. It all works well.
Your rudder doesn't need to be that complicated, but it makes it easy to use in a panic situation.

 

Yeah i won't make my tiller like the one shown. I followed the plans and mine is alot stronger and solid wood

im going to take the original design and alter it as suggested above by having a cassette style and have 1/2" solid sandwich between the 1/4" profile panels. That will leave enough to anchor an eye bolt at the bottom for a bungee cord for the downhaul. I'll have to play around with it to figure out the optimal location for tension on both up and down lift.

 

Thanks for the added info, yeah i dont want to overly complicated things...this is my first sailboat and im loving learning all aspects of the construction boat theory and the vast different ways to rig a boat.

 

It would be better if you could keep the downhaul line out of the flow of water.the drag of a circular body in water is quite considerable.The simplest attachment scheme is to drill a hole through the upper part of the rudder blade-say 1 1/4" and to drill from the periphery of the rudder to intersect the hole.The the line can be threaded through and a stopper knot tied in the end.I can't see if there is enough thickness in the rudder to permit such an arrangement,but the line can be very thin and you can use a length of shock cord from a short distance away if you don't want to chase up a CL257 cleat.

 

Run the bungee along the top of the rudder blade, over the circumference between the cheeks. Anchor one end at the upper forward edge of the blade, anchor the other end at the aft end of the cheek assembly. That should give a torqing force to rotate the rudder downward without putting the bungee in the water at all. The assembly cheeks will hold the bungee across the rounded top of the rudder blade as a guide. You could even put a cam cleat at the aft end of the assembly to adjust the tension on the fly.

What's nice about the setup I am describing is that your leverage doesn't change as the blade rotates. Because it is always pulling against the outside circumstance, the bungee has maximum leverage along that circumference.

‐Will

 

@Will Gilmore , is this the idea with the bungee (red scribble)?


I am starting to like the original plan of using lead...
Here is my Michalak rudder (the Catbox/PDR version) as-was (no up-haul or down-haul) with 2#(.9kg) lead for reference. It seems like perhaps it would not need all of that lead to sink it.

 

Yes.

-Will

 

A rudder that size shouldn't need any lead to sink it; a big flat washer both sides, made of wood or metal, and a bolt and wing nut to give it just enough friction to stay down when going fast, but can be pushed up without dramas. Keep it simple and light weight, forget the lead.

 

@seasquirt How am I going to justify drilling a hole and melting lead into this spare rudder if you keep providing perfectly logical arguments to the contrary?
Original plan calls for 3# (1.4kg) lead, according to CAD it only needs 1.25#(.57kg) to get the immersed blade equal in weight to the water displaced.

 

That will work as long as you never actually sail.Once the boat is moving,the force of water impinging on the rudder blade will cause it to rotate to some extent and the faster you go-the more the rudder will lift.I don't really understand the widespread enthusiasm for weighted rudders when a line or shock cord weighs less and does the job,without the risks of playing with molten metal and a material that always contains moisture.

 

And forever after, you have to carry that lead about, in the car, or in the boat, on the trailer, extra fuel and brakes used, dragging in the mud getting stuck, putting extra wear on the pivot pin, and momentum when rudder is slapped by waves at the beach, so many cons, not many pro's. In 60 years of dinghy sailing I've never heard of a need for lead in a rudder. I think someone was over thinking when they came up with the idea. The lead seen stuck to the side of the ply rudder will act as a flow disrupting brake, always on, and losing you speed and control. Spend time on cordage controls instead, with or without shock cord to assist. That's my 2 lead pellet's worth.

 

I think it comes down to a lack of exposure to dinghy practice.The same pertains to centreboards,some have advocated lead encapsulation for a long time and some of us use a rubber friction brake.There are all manner of people displaying their individual ways of adding lead to foils in various places online and they don't seem inclined to seek other solutions.Maybe its just total reverence for "the plans",which may have been drawn decades ago and the designer wasn't aware of less complicated arrangements at the time.Working in an isolated community can have that kind of effect.Some of us have hundreds of dinghies within a 20 mile radius and some have to drive for 20 miles or more to find their most adjacent boat.Which of the two examples is likely to see the widest range of solutions to select from?

 

I consciously did not want to learn sailboats, because I wanted to "invent" sailboats myself.

My religion is engines and machines. After inventing a few strange machines, the need for sails appeared. Trying to invent some sails, I look with one eye at existing solutions. Sometimes it's funny that I don't know basic sailing things.

But I don't know which way is better.

 

If you good know existing things , it directs thinking in certain directions. But this can be a limitation sometimes.