Looking to get a 1983 5.0 back on the water, want to do it right the first time. Is there a better way to redo the rudder connections, so you can adjust them for 'toe in'?
Come on guys, I know we have a bunch of Nacra rudder system experts on here. Lets show @16newbie some of that knowledge!
Welcome to TheBeachcats 16newbie.
Welcome to the group. Do a search for related topics for Nacra rudders, there are several threads and pictures. I know I did one years back that will be helpful. I would find the link for you but I'm currently traveling with others.Looking to get a 1983 5.0 back on the water, want to do it right the first time. Is there a better way to redo the rudder connections, so you can adjust them for 'toe in'?
The Nacra rudder attachment changed in the early years. My 1984 vintage rudders were on a straight aluminum tube that attached to the tiller crossbar. A later model used a slight bend in the tube that attached to the rudder head, and that is what provides the toe-in. You kind of have to go with what you have since the rudders and rudder heads are unobtanium for this vintage. It might be possible for someone to add a small bend to the top tube and get the correct angles on both your existing rudders. I have not measured that angle, but I would guess it is about 8-10 degrees in front of the rudder head rivets. I used the straight version for decades, but recently bought a replacement rudder through Murray's that has the angle, so I am actually running one of each style. It has not significantly affected my helm, but I will probably talk to a plumber or pipe shop about matching the bend. The toe-in is not adjustable. You either have it fixed in that top rudder tube, or you don't. The weather/lee helm is significantly affected by mast rake and the vertical angle adjustment of the rudders. As the rudder moves closer to the boat, the helm becomes more neutral to downwind, and as they are adjusted out away from the boat, a stronger weather helm develops. More mast rake tends to cause the boat to turn into the wind more as well. I keep mine at a very neutral to slight weather helm.
The bend that Tom mentioned as toe-in is for the Ackerman principle (bent rudder arms), a more efficient turning radius that reduces drag. The distance between the rudder arms can be adjusted by adding the Prindle adjuster to the crossbar if you want to have something adjustable (not necessary if set up correctly). What is important is that when the rudders are straight (in line with the hulls), that both the leading and trailing rudder edges are parallel, or the trailing edges is "slightly" "toed-in".Â
I have several rudders, castings and arms if someone is looking for them. Two of them are tuned for modern sail cuts and raked mast. Â
The legacy rudder castings do allow to adjust rudder rake (small Delrin screw), but with the modern rig set up, it is best to move the rudders all the way against the casting.
I have pictures in my album of the raked rudders.
Here is a picture of the rudders raked for a modern tuned rig . . . mast raked back, square top higher aspect ratio main sail. This is a massive improvement to the legacy setup.
https://archive.thebeachcats.com/pictures/picture.php?/5269/category/320
A lot of helpful information in my album here:
https://archive.thebeachcats.com/pictures/index.php?/category/320/start-60
What is important is that when the rudders are straight (in line with the hulls), that both the leading and trailing rudder edges are parallel, or the trailing edges is "slightly" "toed-in".Â
Philip...for the record...you mean that, if not parallel, the leading edges of the blades should be slightly toed-in, no? In other words, the distance between leading edges is slightly less than that of the trailing edges.
(It wasn't uncommon for folks to inadvertently put the old H16 rudder system on backwards after it had been removed. With that Ackerman bend in the tiller arms, this caused the rudders to be toed-out...distance between leading edges greater than that of trailing. Turned the cat into a dog!)