Rudder Tube Damage and Repair

General
1

I pulled my N30U rudder this week, and after completely removing the quadrant (properly the drive wheel) and the top of stock nut and washers, I had still to pull down on the rudder while wiggling it back and forth to get it to descend. The original reason for removing it was (a) to have a longer keyway milled into the stock to support my autopilot, and (b) to investigate why rotating the rudder was harder than it is on other Nonsuch 30s that happen to be on the hard nearby.

Some additional photos can be found in an earlier query about the quadrant / drive wheel itself, in Steering quadrant mounting height - #12 by NeilErskine .

After removal I noted damage to both the inside of the rudder tube and to the length of rudder stock that can bear on the rudder tube (properly separated by a thin layer of grease). I have had the boat for two years, and although I had used a grease gun on the stock grease cup’s fitting, I found when I set a simple zerk fitting to replace it, that the grease at the back of the cup was petrified. That no lubricant had been supplied for some time was apparent when I pulled the rudder.

I would be very interested in any Hinterhoeller drawings particular to the N30 / N30U models that show anything about the rudder tube at all. The INA site has a drawing for the N26 but I don’t believe that my N30U Amadeus is made exactly the same way. I’m also interested in any thoughts about the required clearances between tube and stock on a Nonsuch, and in ideas on how to repair the rudder tube itself.

All these pictures are after I polished any residues off with a rag and mineral spirits. First off lets view the damage to the rudder stock itself, starting with the section at the top of the rudder tube:

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The shiny section ends exactly where the tube ends. Note that the keyway for the drive wheel extends more than an inch into the tube. It was full of debris; old grease perhaps, mixed with shavings and erosions from the drive wheel which was bearing directly on the tube top. There are predominantly horizontal striations here, and although some could be marks from lathe turnings, they seem overall more numerous, irregular and marked, however, than on the dull section of the stock which presumably was characteristic of the whole surface at manufacture. There are some striations however that are not horizontal.

At the other end of the bearing surface the surface damage is more obvious; the next picture is left right reversed from the previous; the greenish blue on the right is the top of the rudder. I tried very hard to polish the greyish and black deposits off with my rag, but was unsuccessful.

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These scratches are deeper, more numerous and clearly diagonal. Some seem to reflect more than one point in time, as scratches intersect others.

Now the inside of the rudder tube seen from the outside with a light inside the hull. Again, this is after polishing the inside of the tube with rags soaked in mineral spirits wrapped thickly around a stick. The rags came out black, but by no means choked with particulates:

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The stock I think can be polished smooth without too much effort and cost. I am not sure at all what to do about the tube itself. It looks to my eye to be laid up fibreglass that is losing its surface layer of resin. I have an N26 drawing saying its tube is nylon. This does not look to me to be deteriorating as would solid nylon. Comments and ideas solicited and welcomed.

2

A before cleaning picture of the rudder tube. The lighting was different, so the white patch here corresponds to the dark patch on the preceding photo:

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3

The striations on the shaft would be caused by wear and not by lathe turning. A machinist wouldn’t leave such marks on a bearing shaft. I would try using fine 400 or 600 grit wet sanding paper or pad to remove the surface dirt..

In the spring of 2022, I dropped the rudder on my 26. It was becoming very hard to turn because the rudder tube ID had shrunk. The tube is epoxy resin, not Nylon The repair consisted of honing the rudder tube with an automotive cylinder hone to give about a 25 thou diametral clearance. I put a post on the forum describing the work.

It is critical not to have too large a clearance, as it will result in rudder vibration when travelling under power. Your excessive clearance might be able to be fixed as they do for the Catalinas, where developing excessive runner shaft clearances is common issue. The fix is to inject graphite filled epoxy into the gap. I did this with a friend who had the problem.

Here is the link to source for the epoxy.

https://www.catalinadirect.com/shop-by-boat/catalina-30/hull-deck/stern/copy-of-rudder-bearing-epoxy-repair-kit/

The repair steps are

1 : Remove the rudder

2: Clean up the tube ID and the rudder shaft They must be very clean

3: Drill three equidistant radial holes in the tube at about its midpoint.

4: Coat the rudder shaft with release agent and carefully reinstall the rudder.

5: Using a syringe, inject the epoxy/graphite mix through the holes. Plug the holes not in use. Some epoxy probably will come out the top and bottom. It will harden in about a day.

6: Lower the rudder and open up the greasing hole

7: Put everything back together

I could send you more details of the work.

John Barbour

Toronto

Nature 26U

4

I believe the tube is G10, a fiberglass epoxy tube. The Hinterhoeller drawing says nylon but that’s wrong. From the N26 drawing the shaft is 1.75" and the tube ID is 1.875 which makes 125 thou clearance.

25 Thou probably is great but measure your cleaned up shaft and tube and I’d like to know what that clearance is. It might still be ok. Johns tube was very tight on the shaft. Mine has enough clearance that twisting the grease cap squeezes some grease out of the ends of the tube eventually.

The top bearing, an aluminum plate under the nut if it’s still the factory bearing, is probably worn oval and far looser than 25 thou. Mine was about 250 thou in the largest dimension. I replaced it with a plastic bearing that won’t wear like stainless on aluminum. There was a UHMW plastic sheet under the nut from the factory- check that this is still there as well.

Tom

5

Sorry for the long silence. I finally got the rudder back from the machinist and I polished it up a fair bit. To do this I went over the rough patches with a scotch brite pad, scrubbing hard, then ran over the whole bearing surface with green polishing wax using a wool grinder pad. I didn’t lose much material at all; measuring at many locations I found the rudder stock dimension to be close enough to 2.375 (spec) to consider it spec (± a thou).

After cleaning any residual lubricants from inside the rudder tube, I used a cylinder bore gauge to take inside tube diameter pairs (fore/aft and port/starboard) at eight heights in the tube, recording how much each exceeded the diameter of the rudder shaft spec (see upper left of photo). The actual diametral clearances varied from 2 to 7 thousandths excepting in one spot where a chunck of material about the size of a dime is missing.

I tried a number of approaches to removing material from the bore using cylinder hones. The main thing that made a difference is the use of lubricant. Using no lubricant proceeded very slowly. After spraying some WD40 the hone cut about 10 times faster, though I had to remove gunk from the stones with a wire brush. My final measurements are in the bottom left of the photo, and were taken after I cleaned the bore of cutting residue using acetone soaked rags. As I had been following my progress without this cleaning, a few of the measurements show small overshoots.

I also attach a looking-down photo of the bore after cleaning. The black spot at the left hand side is where the greasing fixture enters. This photo shows that after honing the surface is still far from featureless. I’m not convinced that adding material to fill the voids would result in any performance improvement or lifetime extension. Any thoughts people have on this or other matters are solicited, and would be greatly appreciated.

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6

That is tight. Wow. No wonder it was so hard to turn.

Is there any way to test it, install the rudder and see how it moves now?

Im wondering what the machinist did to the rudder? Straightness of the shaft?

Tom

Tom Schoenhofer

7

Replying to Tom Schoenhofer, the machinist added a new keyway for my autopilot tiller arm. As the original keyway was not long enough for both tiller arm and drive wheel I asked to have the original keyway extended. Unfortunately there was no way for him to fit the rudder stock into any of the milling machines at the shop with the rudder pointing opposite to the keyway. The solution was a new short keyway just for the tiller arm, facing aft.

Unfortunately, until the yard lifts the boat there is no way to test everything. The boat is on stands rather than on a cradle, so I dare not dig a hole. The current plan is to put the boat in the TravelLift at the end of an afternoon, reinstall the steering system that evening, and launch in the morning. If that doesn’t work out they will put me back on the jack stands. Although the yard has been very helpful this winter, June is very busy with the yard launching at full capacity though much of the month, so if there is a little delay in getting ready it may be a long delay for the launch.

One more thing, I did some measurements of the upper bearing and it is slightly oval, wider side to side. However, I am leaving that for another winter. It would be nice to get the original spec for the bearing as It would be pretty trivial to manufacture one (or a handful of them) given a drawing.

8

I am impressed with how you did the repair work. Lubricating the hone is a method to remember. The diameter measurements, are very good to have and the more the better.

I assume the 0.020 and 0.028 readings are diametral clearances. They are close to what I got after similar work with the cylinder hone. This was in 2022 and since then, the rudder has been easy to turn and there is no rudder vibration when travelling under power. With your clearances, the rudder should easily turn, assuming it is straight. I expect the machinist would have put a straight edge on the rudder shaft to check its straightness.

With the boat on the travel lift, and the rudder in place (and the rudder tube lubricated), you should be able to easily push it around by hand. If this is successful, I would be confident that the rudder would turn freely in the water. If there will be vibration, which I doubt, it will appear when you are under power.

As the rudder shaft surface is in good condition, the wear on the ID of the tube doesn’t seem to be an issue needing immediate repair.

John Barbour

Nature 26 U

Toronto

9

Have you fully installed the rudder yet? I’m asking as I would like to know what the torque value is on the upper nut :slight_smile:

10

I’ll update the discourse item, but there really is no meaningful torquing value because we are not trying to impose a particular tension on the rudder stock. The desired end configuration is the rudder with one or two nylon washers below the hull, and the nut pressing down on two nylon washers above the top bearing plate to keep the rudder from falling. The rudder is raised to the “right” height and the nut is rotated until it touches the top washers. In my case I defined the right height as leaving about 1/16” clearance between the bottom of the hull and the bottom washers. The torque exerted on the nut is only whatever is needed to rotate the unloaded nut on the threads until it touches the top washer. Then, after whatever is holding up the rudder is released, the tension on the rudder stock will be equal to the weight of the rudder, and will not be related to the torque used to rotate the nut (finger tight in my case).

You could use torque on the nut to raise the rudder to its final height, but that torque would be constant until the rudder/washer touches the bottom of the hull (at which you have gone too far).

I wish I had taken pictures of me raising the rudder, but this was done after dark the night before the boat was to be launched and I was feeling rushed.

Feel free to ask any questions at all

Neil