Crack next to rudder post, general advice needed....

[Lee Jerry]

Generally good advice, and you'll be hiring a pro do to the work, but I'll add a few comments anyway.

Since the crack is on the outside, then you will at least need to attack it (grind out) from that side first. It's unclear with the inside, but I think it can be left intact. (I can't tell with the info given.)

It sounds like the issue is more than just fixing "a crack" since you talk about delamination too. You will need to grind or cut out the outer layers all around the crack until you find solid laminate in all directions. Then taper all sides and fill with glass (presumably larger pieces) as described above.

Originally Posted by catsketcher

You may like to add some gussets onto the rudder stock at the bottom and then glass these with more +-45 fabric (400 or 600gm) to better help with distributing the load from the bottom of the rudder to the hull skin. (I would think triangles about 250mm up the rudder post and along the hull, coved and glassed with 3 layers of 600gm would be nice and help stop any more cracks developing)

Don't do this, at least not without adding more details. As described, it creates a hard spot (i.e. stress riser) at the end of each gusset that will put forces into the skin that will cause more cracking. Proper gussets need to terminate into other cross structure.

[sinnerman]

My rudder post leaks (actually seeps)

I rebed the packing gland but it persists.

My "analysis" is that over time the rudder rotations wears away the fiberglass rudder tube especially with high side loading when the the boat is on a heel.

Original the rudder post load is being distributed along the entire length of the tube (like a roller bearing). As the wear progresses, the contact become less and less until the load is essentially only being carried at the base and top of the tube.

The tube now becomes overstressed at the top where it has the least support and fatigue cracks form.

The correction (for me, yet to perform) is to re-establish the correct tube-to-post clearance using an epoxy repair. There is a repair in the West System manual for this using epoxy and a carbon additive.

The West repair injects rein at three locations each bottom /top to form wear "pads". The original repair is to fill the whole darn tube with the stuff (better I think).

After that, repair the cracks and possibly reinforce the top of the tube.

As the others already stated, you need to get the resin repair all the way through the crack. Also, it is the fiberglass cloth that provides the tensile strength. Resin is just the "glue" .

My three cents.

Cheers

[MEC]

If I understand the photos correctly, the defect is oriented vertically on the outer diameter of the lower rudder bearing's cylindrical housing. The lowest point of defect is above the intersection of the cylindrical housing and the hull.


Normal hydraulic loads applied from the rudder into the bearing housing create bending moments at the intersection of housing and hull. A defect produced by these bending moments would be located at the intersection of housing and hull and oriented circumferentially. The defect location and geometry doesn't fit this pattern.


Also, I am not persuaded by the remark that oscillating rudder post motion in the bore of the lower bearing housing "wore" thru the housing wall in only one location. My experience is that rudder lower bearings wear in a "bell-mouth" shape, larger bore diameter at the bottom compared to top.


Sudden impact loads absorbed by composite structures produce complex fracture or delamination patterns that have a common feature that the damage is "widely" distributed in a surface. Your defect doesn't appear to fit this characteristic. Also, a large impact load to a rudder system sufficient to damage the lower bearing structure typically also damages the rudder skins and/or metallic rudder post.


Before a repair plan can be produced, someone with expertise in sailing yacht rudders with fiberglass hulls needs to determine the root cause of the defects you have. My experience is that this will require skilled structure dissection.


IMO, before a repair can be engineered, it is necessary to assess:

• the alignment quality of upper and lower rudder bearing bores to the keel centerline,
• clearance between rudder post and bearing bore,
• alignment quality of steering wire rope to the quadrant and wire rope tightness,
• design of rudder bearings for the application,
• Whether the defect is most likely caused by a construction defect.

I hope this information is useful.
Marcus

[Olly75]

Thank you all for the further posts and info.
The issue I face in diagnosing the root cause of the problem, assuming it's not a collision impact is finding someone with enough experience to diagnose.

I'm currently on the west coast of Malaysia heading for Pangkor to haul out early next week, does anyone know recommend a professional there or alternatively langkawi?

[boatpoker]

Originally Posted by Olly75

Thank you all for the further posts and info.
The issue I face in diagnosing the root cause of the problem, assuming it's not a collision impact is finding someone with enough experience to diagnose.

I'm currently on the west coast of Malaysia heading for Pangkor to haul out early next week, does anyone know recommend a professional there or alternatively langkawi?

In the photos, immediately to the left of the measuring tape tip at what I suppose is the rudder tube I see what appears to be hardened resin. It looks like someone just poured resin there (an old shoddy repair ?). I suspect once you start grinding you will find the rudder tube has also been affected by whatever happened here.