Guys,

How many of you guys have rudder systems on your F16 which allow easy rake adjustments? If you do have an adjustable rake system, how does it work?

Geoff

I can chock out the top and bottom pintles, but this has very little affect on rudder balance or boat balance. Its only influence is on ventilation (not cavitation which isn't a concern on most sailing yachts). The blade rotates with the stock and pintle so its leading edge is always about 5mm in front of the rotation axis (centre of pintle).

Some of the flip-up rudders have screw adjustments at the bottom of the stock which bears against the leading edge of the blade. Screwing one way rotates the blade aft of vertical, screwing the other way rotates the blade fwd of vertical. ie. the blade rotates either aft or fwd relative to the pintle from a few millimetres fwd to a few millimetres aft of the pintle axis. This again doesn't have too much influence on theoretical performance, however it has a huge affect on the tiller force to steer the boat. Rotating the blade forward makes it more balanced hence less force on the tiller, and moving after makes it less balanced which leads to more force on the tiller. Please note that the force on the rudder only changes minutely (negligible actually), but it is the lever lengths that are changing the force the skipper feels on the tiller.

Which of these "rakes" are you interested in?

Ncik,

I am interested in the tiller forces.

My I17 had a system that you could adjust on the water: the top gudgeon was simply an eye threaded into the casting that you could turn in and out to change rudder rake. It was convenient to be able to fine tune the rake on the water to minimize helm.

I was wondering if anybody was using a similarly easily adjustable system on their F16. Our current system is not adjustable and we have not achieved the almost perfectly neutral helm we are used to.

How do you find the helm on your F16?

Geoff

Generally speaking, any boat should have a slight tendency to round up into the wind, which will require a bit of correction with the rudder (weather helm).

This is different to rudder balance.

Unfortunately, it is a bit more complicated to diagnose general "heavy steering" on catamarans because of the second rudder.

My weather helm is fine in a straight line, but during turns (tacks and gybes) it gets very heavy. This is probably because we are hurtling along before turns and applying the brake (rudder) will require some force. Doesn't seem to be a problem while racing. Having one hull out of the water reduces the force considerably.

I don't know of any other system for adjusting rudder rake.

There are several ways and tricks to balance the rudders. It depends on your specific rudder setup what will wotk for you. can you give us some pics of your setup.

To give you an example. I can adjust rake using my lockdown rods. But when I run out of adjustment with those I had to fill and redrill the axis holes in the rudderboard itself.

Another option is to screw a bolt into the leading edge of the board so its head will rest against the inside of the rudderstock; this works for rudder setup that use lines and pivoting cleats for lock down.

But basically the mods are easily done and once it is set right you won't have to change ever again.

Wouter

Wouter,

We have a rod-based system. The stocks are aluminum. It looks kind of like the AHPC setup did on my old Mk4. I believe it was sourced from somewhere in Europe. I don't have any pictures.

The rods do have a length adjustment, but I thought this adjustment was mainly for controlling the amount of compression on the rod when it is locked down. Shortening the rod to sweep the rudders back (away from the boat) would cause sloppiness because the rudders would not be snugged-up to the stops. Let me know if you think differently.

Also, changing the rod length doesn't buy you any ability to sweep the rudders forward (under the boat) because you can't move forward past the casting.

I understand your point about finding a setting that works and never changing it, but if you can't easily adjust your rudder rake, how do you ever find the perfect setting?

Geoff

Okay,

These rudderstocks (and rudders) are made by www.catamaranparts.nl You cna contact Hans there and put the questions to him.

With the rod setup one alternative is too put a spacer on either the rudder or inside the stock near the bottom pintle. Indeed this rakes back the rudder. However, this is all relative to the hole in the rudderboard. If you can't get the rudder enough forward then filling an redrilling the holes will allow the board to be raked further forward where the spacer can be used to really fine tune the setting.

Of course I assume that the rod itself can be adjusted in length.

This is actually part of the solution I had to apply to my own AHPC rudders as they had misalligned the board before drilling the holes at the factory. I actually had Hans from www.catamaranparts.nl sort this one out for me and now my rudders are very well balanced.

The spacer itself can take on many forms. One of the more simple ones is a a bolt(screw) screwed into the leading edge of the rudderboard itself. There is not much force on such an element as all forces try to rake the board furter backwards or move it sideways while sailing. The bolt only needs to take the pretension of the rod when the boat is motionless and that is not a very high load when felt at the bottom pintle. It is my understanding that drilling out a tunnel with a large diameter drill first and filling it out with epoxy is enough to reinforce the board locally. Then the correct tunnel can be drilled in the epoxy making the epoxy holding the screw rather then the foam.

Other spacers can be a piece of plastic breadboard fitted somehow to the inside of the stock, use you own imagination here.

But again I would advice you to discuss you issue with Hans himself and see what he says.

Wouter