Skeg/Rudder Repair

[minaret]

Hello everyone, very busy summer, been gone awhile. Got in over a month of cruising in the islands this summer, fabulous time had by all.


So I note a number of threads on skeg repair, and I happen to be doing one now, so I thought I'd do a thread on it.


The boat is a Grand Soleil; she hit a log off the Oregon Coast this summer. Damage to the skeg was severe. As usual, on inspection of the rudder, it was immediately clear that it had a long history and had seen more than one incident and set of repairs. It was extremely waterlogged and cracked on the seam. As I often do, I suggested to the owner that he send it in to Foss Foams so they could pull a mold and make him a new one. Even with shipping added, no one can compete with their costs for rudder rebuild. Most of the yards I've worked in sub this work out to them and then mark it up. Going direct can be a $ saver, they are very accommodating and easy to work with. New rudder is nearing completion and should arrive soon. But, to the skeg!

[minaret]

Tent up and initial inspection. Doesn't look good! There was a lot of speculation as to whether we were seeing a failed repair, or failed factory secondary bonding. Check out the volume of weepage on that rudder! When you see weepage that has a rainbow sheen like this, looks like an oil slick, smells strongly of vinegar and chems, it's been in there a long long time and the rudder laminate is likely to be hydrolyzed from the inside out. Not to mention crevice corrosion in the armature!

[minaret]

Exploratory grind is complete. All coatings are removed so we can see what the hell is going on here. And, of course, that's not what you wanna see!



At this stage, it is clear that this is a failed factory bond in the original skeg construction. Note the vertical center seam that is split, it's a dead giveaway. This skeg was constructed at the factory in a split mold. Two skeg halves were molded and then applied into a molded recess in the bottom of the boat. The cavity thus formed on the inside of the hull was then poured with what looks like chockfast, after insertion of gudgeon plates. No glass was applied to the center seam from the interior before pouring. The molded recess to accept the skeg laminate got zero extra prep, and the skeg was bonded on over gelcoat at the factory. They did not tape off the molded recess. Bruno strikes again (inside joke for those who follow these threads)!


Some of the construction details here include a piece of glass tube with an ID same as the rudder shaft, split and then bonded to the aft end of the skeg to provide the recess for the leading edge of the rudder. This too was simply bonded in place with no laminate over it. If you look carefully, you can see that this boat has had a long history of leaky rudder post/skeg interior area, and has had a number of small spot repairs done in an effort to fix this water intrusion. This included dropping the rudder and glassing aft edge of the skeg, glassing the skeg at turn of the bilge, etc etc. You can see the repairs, as they are in poly iso and stand out clearly on the factory ortho layup due to color difference of the resin. I wonder how much $$ was spent in yards trying to chase this leak, and no one ever bothered to do a full exploratory grind and determine the full extent of the problem? The owner is lucky this didn't end in emergency! The rudder also had a number of obvious repairs, and I would guess each set of them at a yard cost about 1/2 the cost of a new rudder from Foss.


I believe they bonded this skeg in place by spraying wet laminate with a chopper gun into the recess and then clamping the molded skeg pieces in place. This provided an extremely porous layup. Note also the large amount of moisture weeping out of the laminate. When the skeg halves were removed, a great deal of water was seen to be trapped in the delam interstice between skeg laminate and hull laminate. This resulted is a very wet and partially hydrolyzed skeg layup. Another thing exposed by a proper exploratory.


It may be hard to see here, but it's also quite evident at this stage that rudder alignment to the skeg is not stellar. The gap between skeg and rudder is huge, and off center a bit.

[minaret]

I decided to save myself a crap load of heavy grinding by removing the failed skeg laminate by brute force. It should not be possible to do this! But it sure saved me a ton of work. Skeg laminate is about 3/8" thick, it would have taken a couple of days of the most brutal heavy overhead grinding to remove this layup.

[minaret]

All skeg laminate removed. What is left here is the original hull layup, and the pour they did to fill the skeg cavity. We were careful to preserve this during demo; it would have been easy to break off entirely, it was not at all strong with all laminate removed. But we wanted a form to reproduce the original shape and structure as closely as possible, but without the flaws.

[minaret]

At this stage, the source of the long term water ingress is evident. When they poured the skeg cavity at the factory, they could only pour so high due to the shape of the hull. This left a long thin cavity in the top of the skeg. This cavity had exposure at the top end of the split tube they bonded to the trailing edge of the skeg, right at the center rudder bearing. The black rotten laminate is a sure sign of long term water exposure. This boat had a number of small glass repairs a few feet forward of this ingress point on the inside of the hull, where it had been coming in!

[minaret]

Here you can really see the end of the original hull laminate, and the gell underneath the bonded on skeg laminate. You can clearly see the overspray at the edge of the layup.

[Cheechako]

Great post, nice to see this stuff.

[minaret]

Preparatory grind complete. CSM mold skin was quite thick, very porous and wet, so I removed it over the entire area of the repair. Wanted to ensure tying structural fiber to structural fiber in any case. Now that glass fiber is removed and area is cleaned up, you can really see whats going on here. I took edges of the original mold recess back a little further in preparation for new laminate, as well. Wanted a really large faying surface for excellent structural tie in. Next step was a good long period of drying under IR radiant heat, to ensure a dry substrate for bonding. It was really wet after having water trapped in there since construction. Note also that the gudgeon plates aren't properly aligned, they really threw those in there as an afterthought! And the center bearing had a section of glass tube bonded to the hull around it, once again no laminate onto the bearing or the section of tube, only bonded in place. I removed the section of tube around the bearing to provide space to laminate directly to the bearing.

[minaret]

First layup goes on, 4 plies alternating 1200 0/90 and 1700 +/- 45. No patterning yet, freehand layup with each ply warapping around the leading edge 3" or so. This means that for each ply added to the skeg, the leading edge gets two plies due to overlap. This makes it strong as hell. It's also the only practical way to make this layup. Hand laminating 1700 upside down over a radius that tight is not easy. I was pleased to pull it off, briefly considered 1200 only for this reason. No, no bag was needed.

[minaret]

Second layup. Four more plies.

[minaret]

Third layup. All in Silvertip.

[Sailmonkey]

That Bruno guy gets around!!

[minaret]

Fourth layup. This skeg is not going anywhere!

[minaret]

Major structural laminate complete. Only a few things like shaping and taping the trailing edge, adding some extra glass uni to the bottom of the skeg, etc left.This layup came out super fair. For filling in a 3/8" deep molded recess, I was really proud of how fair we got it in solid glass. Proper patterning pays off!