Rudder support

[Roger L]

On my Mainship 34T the rudder posts extend through a horizontal plywood platform and have a poly square that they also pass through that is fastened with 4 sheet metal screws . Is the poly for stability? Screws we’re loose and I am surprised they are not through bolted if in fact they are for support.

 

[Comodave]

I would through bolt them. Just make sure the poly plate is centered first.

 

[danderer]

We looked at a number of 34Ts and they all had this arrangement. We never had any problems with our and I never heard of anyone else with a problem.

Doesn't mean this setup couldn't be improved of course.

 

[Roger L]

I agree.

 

[Roger L]

That’s my plan

 

[jungpeter]

We looked at a number of 34Ts and they all had this arrangement. We never had any problems with our and I never heard of anyone else with a problem.

Doesn't mean this setup couldn't be improved of course.

Hi Roger L.

Forgive me if my assumptions are incorrect, as I have no first person experience with the steering system on a Mainship 34T. But from danderer's picture, it appears you hopefully have another rudder bearing at the bottom of your rudder. I.e. your's isn't a spade rudder.

If so, then the "poly square" you allude to in your original post must function as the upper rudder bearing, as the bronze packing gland located below the plywood rudder shelf does not. So, if my assumption is correct, Commodave's suggestion to through-bolt it is spot on. To a degree.

Yes, I second that the upper bearing must be centered on the rudder post. Very CLOSELY centered. And yes, it must be through-bolted. Hopefully, your post is straight enough so your non-floating upper bearing won't wear excessively. AND, this upper bearing, which appears quite thin, is hopefully made from something other than marine board! Excessive wear in this upper bearing can and will result in scoring and damage to the shaft in way of the bronze packing, which is spendy to repair, and make the packing leak like a sieve. I'm surprised the manufacturer didn't install something more akin to a true rudder bearing like this: https://www.tidesmarine.com/rudder/urbstd_overview

As danderer stated, doesn't mean the existing installation couldn't be improved.

And I guess I should venture the opinion that if yours is instead a spade rudder, then the manufacturer is relying on the packing gland assembly for the lower bearing, and that very thin unknown plastic material above as the upper bearing. That's a scary install in my opinion.

Regards,

Pete

 

[danderer]

There was no skeg below the rudder on mine.

 

[jungpeter]

Hi Danderer,

Yikes.

Pete

 

[BB-marine]

I just dropped both my rudders on my Mainship 34 Pilot. This was needed to remove the shafts because Mainship did not offset the rudders from the shaft line. I replaced both dripless seals and the cutlass bearings, 2002 Pilot. When I started the removal of the rudders I found exactly what you have. Exception the white polymer board ( thru Bolted to the rudder board 1/4-20 screws with washers and locking nuts holding each square polymer board 4" square. The bore size is slightly larger than the rudder shaft diameter. This board acts as a side to side bearing and as a thrust bearing. There is a locking collar located on the top of the polymer board that has a coating of grease under it. There is also a locking collar that rides lightly on the top of the packing nut. I believe this is a safety collar. The packing gland specs are to have (2) 1/4" packing sealing rings but there is easily room for (3) I installed (3). The Rudder port as a slightly larger ID to the rudder post and works as a bushing to support the rudder post. I applied a good anti corrosion grease in the bore and on the lower section of the post (shaft). I installed the assembly exactly the way I found it with the exception of an extra packing ring. This installation looks a bit crude. I did take it completely apart and inspect all components for wear. I measured the shafts with a Micrometer and found no measurable wear and polished the shafts with 320 crocus cloth and they looked new. The boat is 20 years old with 880 hours. If I found issues with the parts I would have changed the way it is assembled. I found no issues so I put it back together the way Mainship designed it.

The only change I would make to your rudder Assembly is Bolt the polymer board down.

 

[lwarden]

FWIW, I had a vibration at cruising speed of 18 knots that I had a hell of a time finding the cause of. Turned out I have similar polymer blocks on my boat to support the upper end of the rudder posts. These were only held in to the fiberglass support shelf with #12 sheet metal screws and they had backed out. I replaced them with a larger screw and plan to through-bolt them in the fall when I haul out and do the bottom and repack the glands. This took away the vibration so the rudders were fluttering back and forth with the prop wash. So these bearing blocks and their solid attachment are pretty important, especially for faster boats.