Help analyze personal inspection findings (2 of 5) - rudder corrosion

[pillars]

Topic 2 - rudder trailing edge corrosion

See attached picture - does this require a full rudder replacement or can this be repaired?

Matching rudder (not installed) pic included for reference.


Apologies for the sideways pic, not sure how to fix the orientation in the post.

[a64pilot]

Steel rudder for a powerboat?
If so easily repaired. I’d remove it and have it galvanized I think

[pillars]

Leopard 40 catamaran rudder. I don't think it's steel, I think the outer shell is fiberglass(?).

[Suijin]

If it’s encapsulated in fiberglass then it would be the internal frame and maybe even the post that are rusting. Is there a crack along the trailing edge? Internal corrosion usually splits open the two halves at some point.

Personally if it’s fiberglass and you can confirm it’s rust, then I would open it up to see what’s going on. Then again there is no such thing as a dry rudder and being a cat there is a spare.

Investigation would entail cutting open one side and digging out the foam to inspect the frame.

It’s odd that it’s the trailing edge and so regular...like cavitation wore the coating away. It almost looks like it was the coating itself that rusted.

[a64pilot]

I’d swag that your buying a new rudder.
Yes it can be repaired, anything can, but if your asking us, that means you don’t likely know how and would be hiring it out.
If that is the case, maybe a new one is better, close you know how much it’s going to cost, and have a real good idea how long it will last, a repaired one? OK if done by a Pro, likely better than new, but how many real Pros are there out there?

[MikeFergie]

I have a leopard 40 and the drawings from R&C on the rudder design. I have made molds of mine and made 2 blades myself using the original stocks. The stocks are 40 mm solid stainless steel tapered at the bottom. There are 3 holes near the bottom through the tapered section. 10mm stainless bars are welded into these holes and provide the surface area to help the stock round bar in the blade. You have 2 molds sides which are filled with expo you structural foam and edged with bonding paste and then you put the 2 sides together.

If you need any more info PM me and I can send you pictures etc

[RaymondR]

It's not a structural problem, it's only fairing to give the rudder shape and can be easily repaired with epoxy and glass fibre.

[Elie]

Originally Posted by RaymondR

It's not a structural problem, it's only fairing to give the rudder shape and can be easily repaired with epoxy and glass fibre.

I share that opinion.
Further more, my sloop very substantial fiberglass rudder showed serious water intrusion and delamination. I had it remade around the original Stainless steel shaft. It is a nice welded all 316L stainless steel that may double as a reserve fuel storage(never used it for that function ... yet. 2 round anodes are bolted, but, seems to be unchanged since installed. No corrosion galvanic or otherwise since the last 10 years. My only problem was a surveyor that wrote that he found some humidity into the laminate...
By the way, The rudder is completly coverd with Interprotect(6 coats) .

[Singularity]

Originally Posted by Elie

I share that opinion.

I third it.

The aft edge of the rudder is a glass-to-glass bond. I don't know what all is going on with the rudder, but some fill is needed to smooth the transition from the middle of the rudder to the effectively pinched rear edge.

In the following page of a small aircraft rudder construction you can see a thin stripe of white fill material along the aft edge if the airplane's rudder:

https://cozyfish.weebly.com/ch-20-wi...ttachment.html