Gilo,

The way I look at it is this.

When you jank your tillers over by say 20 degrees when sailing at 10 knots then the sideways load on the rudder blades is easily in the order of 100 kg. The loads on the pintles will be heigher still as they will have to resist the resulting moment on the rudder while having a relative small leverage.

The T-foil winglets are only 1/3rd the area of the rudderblades and so the forces they generate will be about 1/3rd as well. I don't see how the sterns will fail under those loads when they won't under the much higher loads generated with abrupt steering.

The only situation where you increase the loads is when you steer very abruptly during a full on pitchpole as then both loadings will be on the stern simultaniously. But they will also be perpendicular to eachother making the resulting force only 104.4% higher then the load without T-foils. (remember the law of Pythagoras)

I really don't see this as any cause for worry.

But if anybody thinks it is then the sterns can be reinforced from the inside, relatively easily I imagine even. Just glue a extra plate to the stern and two "angles" securing the stern more forcefully to the keel line and deck. I think this can be done with 5 mm ply after being saturated with resin. There are enough solutions and I don't see any of them as particulary difficult to perform.

Darryl has been experimenting with them in AUS where he simply used to old kick-up system of his old rudders. He report that the kick-up mechanism work just as it would with conventional rudders and he has had no damage yet. Getting back to to beach even in heavy surf should not be a problem with these kick-up T-foils. Basically I sailing my boat in with rudders down but lock down arms disconnected in these conditions anyway. As soon as I reach depths of less the 60 cm the rudders kick-up against the friction of the rudder stocks. By that time the breakers are behind you as no large wave can come as 60 cm shallow water without breaking. Been doing this for 3 years as well, no problems here. Sure the T-foils will add drag when kicked-up but when I sail in 60 cm deep water I want to slow down before hitting the beach anyway.

The only remaining "issue" is getting out through a big surf, although as soon as you reach water deeper then 60 cm you can just rotate them them down fully and have the stock friction keep them in place. I sail out through big surf in the same way with my conventional rudders and it is the best approach anyway. Again the big breakers are encountered over deeper water then 60 cm.

So I feel that a kick-up mechanism as we have now can easily be used for T-foils rudders, There is not really a need to have them slide up and down. Sliding up and down may well be an advantage on its own but it is not needed. That is also what Darryl told me about his experience with kick-up T-foils

I've also an idea to have the T-foil rudderboards use all the same hardware as we are using now, this includes the locking down the rudderstock in the vertical direction and I'm not refering to the litte clip. I discovered that simple solution by accident when trying to dismount my my AHPC rudders. At one time I tried to take my rudders off when the rudderboards were in their down positions, but I couldn't. See the attached picture of why that was (and I don't have that black retaining clip fitted ! ) :




The part of the rudderboard that is in front of the pintle axis, in order to balance the rudders, achieves a full lock of the stock/rudder on the lower rudderpintle, preventing it from slide up or down. With my rudders there is hardly any spacing between the rudder and pintle at all and the stock was held into place very firmly. I don't have even the retaining little clips on my sterns and I've been sailing like this succesfully for 3 years now. I only have small split rings through the little hole at the top of the pintles to keep my rudders attached to the sterns when going in and out through the surf with the rudders trailing behind the boat. That is all that is needed. Others can continue using the little clips for this purpose.

We can make use of the same principle to have fully locked T-foil rudders using all the hardware that our current rudders use, we only need to add little foils to their tips or have new rudders with T-foils made.

My presonal problem with using my current AHPC rudders is that they are not easily modified to take T-foils because of their shark fin tips. I have to cut off too much board to get a large enough area to fit the T-foils too. So I will have to get new boards. I think your rudders with their tapered by square head tips are alot more easily modified.

It is a wild idea but do you want to give this a try ?

I will ask Frank and Martien the same thing, maybe we can work together and get one demo set made by Hans that we can all use for a while, gether some experience with it, before we all spend some money on it. With the 4 of use the costs could be low enough to just give it a shot.

I don't know, this may well be the trick that gets stuff rolling.

Wouter