Does this part of the gudgeon do anything?

beldar boathead

Well-Known Member
Although long thought to be merely decorative, this is an important part of the original sunfish rudder system. The “thumbscrew” is actually a wingnut. Hopefully it is at the end of a long carriage bolt. Do you have the rudder that goes with this?
Thread starter #3
Yes, I meant wingnut. I have the original rudder and it fits fine. I am reading the Sunfish Bible and I think he said something about that letting the rudder kick up and to tighten the wingnut as hard as you can by hand, but I can't imagine how when it's a slab of steel bolted down on the other end. I don't know for sure if this thing is what he was talking about, there are no pictures.

beldar boathead

Well-Known Member
That is what he is talking about. It’s not steel or it would rust. Someone else will know what it is made of - I haven’t seen one in years. It’s likley brass. Anyway it’ll bend some when you tighten it to the max. If it’s loose the rudder will pop up too easily. Also, for it to work right, the carriage bolt must be in a plastic tube to keep it centered in the groove in the hull.
Thread starter #5
That sounds like it might be sacrificial? I haven't heard anything about a plastic tube. The groove is not much bigger than the bolt itself. I guess I'll find out eventually.

beldar boathead

Well-Known Member
If you don’t have the tube and your rudder starts unexpectedly popping up on windy days, you will be buying a tube ASAP. This rudder system is not the best, which is why it was replaced back in 1972.
Thread starter #7
I don't even see anything like that for sale from them.
And to make one, it would have to be the size of an ink pen tube...


Active Member
Don't worry about the plastic tube, it's long gone on most all of the boats and has
nothing to do with the rudder popping up. Tightening the wingnut pulls up on the
bottom strap and makes it harder for the rudder to pop out. The plate on top is
a spring plate that lets the bottom strap 'give' if the rudder hits something. The spring
plate is angled upward by sitting on top of mounting screws. If the spring plate is
sitting flat on the top grudgon it will not do its job. I made a plate from hardware
bar stock and it worked just fine. Personally it's much worth it if you can find
parts for the newer rudder.

beldar boathead

Well-Known Member
In fact the plastic tube has quite a bit to do with the rudder popping up. It keeps the piece on the bottom of the hull centered under load in high winds. Without the tube the carriage bolt shifts to leeward along with the bottom plate, and that small misalignment is enough to make it easier for the rudder to pop up.

However, getting the new style rudder is the best approach.


Active Member
There is lots of neoprene tubing listed on the web you can use.
I never had trouble with the strap shifting, it was mainly the pocket
in the lower strap lost the edge needed to keep vertical piece from
popping out. Anyway the whole unit only worked good when it was
new from the factory. I think I got lucky finding a aluminum rudder
cheek on Ebay for a decent price. It would be nice if someone could
turn out a plastic rudder cheek unit using their Home Deposition Machine.
If it was a commercial machine it would also have the resolution to
make DePersa drain plugs.
To add to what has already been said. this item is a 7 1/2" long by 1/4" dia. bronze carriage bolt with a wing nut on the deck plate end. Its function is to tension the rig to keep the rudder in the "down" position but not so tight as to prevent kick-up if the rudder blade hits a submerged object. The plastic tube that surrounds the bolt in the recessed fiberglass notch is important as it keeps the bolt in alignment. Any good hardware or plumbing supply store sells tube like this in bulk that will replace the factory issued tube.

This rig works like early downhill ski bindings. Too little tension and the rudder kicks up when you don't want it to; too much tension and the rig does not kick up when you hit an object and the rudder blade is damaged. The post 1972 rudder rig is a big improvement over this original rig, but the old rig works if you find the "sweet spot" for the wing nut tension.

Alan Glos
Cazenovia, NY
I have a 1971 Sunfish, and I am happy to report the rudder hardware works exactly as it should 45+ years later. I fully expect that I will give out long before the rudder hardware does. What did give out however was the backing block as it had begun to rot and was not installed correctly as the factory. I replaced that.

Looking at your photo, the top and bottom bronze pieces looks just fine, and you should have no trouble with them. One thing to check though is the screw that holds the bottom piece in place. Make sure it is tight and the backing block has not stripped. If it has, you can fill it with epoxy and wood flour (or very fine saw dust) and then re-drill it.

As Beldar B. & Alan have stated, the tube is critical to restrict lateral movement. Don't go sailing without it. If you stop and think about it for a moment, it is obvious the tube is important as the stern was molded specifically for it.

The tube on my boat deteriorated to the point that it crumbled and so needed replacing. My hardware store didn't have the right tube, but I was able to find it online at McMaster Carr. I will measure and report back if different, but I believe the tube is white nylon 3/4 OD 1/4 OD.

On how tight the wing nut should be, I keep mine tight, but not anywhere near as hard as I could. Instead, and as I have mentioned in other posts, I work hard to keep the tiller load low by keeping the boat flat and adjusting the gooseneck for high wind. In really high winds I might tighten the wing nut more.
Thread starter #13
The smallest width of that groove is maybe 3/8", no way a 3/4" tube would fit in there. This is the closest thing McMaster Carr has that might fit.
Flexible High-Pressure Nylon Tubing, Semi-Clear, 0.225" ID, 3/8" OD $9.85/5 feet + shipping.
Not questioning the importance of this thing, but if it's so important, you'd think Sunfish would have it available in the 6" that I need for a buck...guess I'll have to start visiting hardware stores.

beldar boathead

Well-Known Member
The Sunfish manufacturer hasn’t stocked parts for those old rudders in 20 years I bet. Don’t feel bad as the company that currently makes Sunfish is pretty clueless and doesn’t stock parts for new boats either!
Thread starter #15
I had $150 worth of parts I need in my basket there, but they don't answer the phone and Intensity seems to sell the same stuff for a lot less, so I just went with them instead, saved about $50, assuming the mast caps and such are the same. The guy at Intensity says they will. We'll see.


Well-Known Member
My next-to-the-latest Sunfish (#4 of 5) came with this tube. That Sunfish is located a six-hour drive from where I am now, so I can't tell you what it's made of—but this is what it looks like:

Fullscreen capture 1062017 65404 AM.bmp.jpg

signal charlie

Well-Known Member
Staff member
The wing nut adjusts the tension on the vertical plate that attaches to the rudder blade. We leave the wing nut loose while we install the rudder pin, then tighten it so the vertical plate is snug into the notch on the keel plate. That top plate is called the spring plate, and there is a little hump under it on the deck plate that gives it room to flex down like a diving board, which in turn lets the bottom of the vertical plate pop out if you hit something.

Here's a picture of the carriage bolt tube.

Alcort Super Sailfish MKII rudder carriage bolt tube.jpeg
The smallest width of that groove is maybe 3/8", no way a 3/4" tube would fit in there. This is the closest thing McMaster Carr has that might fit.
Flexible High-Pressure Nylon Tubing, Semi-Clear, 0.225" ID, 3/8" OD $9.85/5 feet + shipping.
Not questioning the importance of this thing, but if it's so important, you'd think Sunfish would have it available in the 6" that I need for a buck...guess I'll have to start visiting hardware stores.
Hi JosefR, Yep, I guessed wrong. The tube is 1/2" OD x 1/4" ID x 5 1/4". The tube as i recall is not totally recessed in the groove as I recall and the 1/2" OD should fit. I just looked at the McMaster site and the stock number is 8628K27. The price is $11.09 for 5' When I bought mine they sold it by the foot.

signal charlie

Well-Known Member
Staff member
A little trivia, new skippers think that the number on the rudder hardware is a serial number. 2,675,775 is the Patent Number.

Alcort Rudder Releasing Mechanism Patent page 1.png

Alcort Rudder Releasing Mechanism Patent page 2.png Alcort Rudder Releasing Mechanism Patent page 3.png

And a tip, I would not attach the horizontal pivot pin (rudder pin) to the deck with the keeper chain, the pins tend to disappear during trailer trips or storage. I have started attaching the keeper chain to the side of the rudder blade. Other options are to remove them for storage and transport or tape them securely. Same thing if the mast has the eyebolt and block at the top, and watch for any deformation of that eyebolt, it could be chrome plated brass and if it is, it is better to change to the new style plastic fairlead cap.

Kent and Audrey