Question about hull coating

[Bill G]

Thanks for all of the input - here is the current state of affairs:

I am looking for a contractor in the Solomons (MD) area to strip off the blue coating (probably an epoxy coating) with a plane to leave the bottom as fair as possible.

The rudder is at my house. I have ground off the blue coating down to bare fiberglass (a really dirty job!). I have found several spots where the rudder coating had failed and allowed water penetration. Also, the aft edge has numerous gaps. The fiberglass shell is 1/4" on the in-water portion of the rudder and 3/8 inch above the water where the hull connectors are and the tiller connects. The top 1mm of the fiberglass below the waterline has numerous wet spots that I ground down to solid glass. After drilling several holes through the rudder, I have found that the foam core is really wet and about 15% of the interior of the rudder below the waterline is a void - no foam core at all - just hollow. I am planning on taking a large portion of one side of the rudder skin off so that I can remove the wet foam. After inspecting the interior, I hope to be able to replace the foam (any recommendations on weight of foam?) and then replace the removed skin and add a layer of glass to the area below the waterline and add additional glass on the leading edge and the aft edge. I will then barrier coat the rudder below the waterline.

[delmarrey]

Bill,
Sounds like a good plan. If you have voids for sure then re-coring would be best.

As an FYI, inside attached to the rudder post there should be some gussets that keep the post from rotating in the rudder. The gussets should extend aft in the rudder almost to the following edge.

These gussets should also be trapped between solid surfaces like wood or solid glass, so they don't crush the foam and start moving. Once the rudder starts moving on the shaft it can tear up the foam inside, up/down and port/stbd. Plus the water can leak down around the shaft.
Let us know what you find after opening it up.

[Cheechako]

I would fill the rudder with resin and a lightweight filler. Yeah, it'll be a bit heavier, but the weight in the water wont be too bad.

[delmarrey]

I've always been under the impression that the lower sections of sailboat rudders should float.
1) because it takes the weight off of the pivot flange bearing.
2) it makes it retrievable if it happens to break off.
3) lighter weight (racers) adds to buoyancy.

[Bill G]

I opened up the rudder today and remove the soaked foam. Some pictures are here
https://plus.google.com/photos/11427...47106102162161

There is a wooden block that provides support for the bearing at the bottom of the rudder. I will sort out whether this needs to be replaced once everything dries up.

I am going to let the fiberglass dry for awhile and then sort out how to refill the rudder with foam and seal it up. I will probably add one layer of biaxial cloth to the entire surface below the waterline.

[Cheechako]

Originally Posted by delmarrey

I've always been under the impression that the lower sections of sailboat rudders should float.
1) because it takes the weight off of the pivot flange bearing.
2) it makes it retrievable if it happens to break off.
3) lighter weight (racers) adds to buoyancy.

Good points. I did mine in solid "ruddercast" epoxy. A product designed to cast rudders without a fiberglass shell. I bought it surplus. pretty much a blue colored epoxy with some sort of lightweight filler. Not sure which bearing you mean, but on a boat with a lower bearing I doubt the little extra weight would be an issue. A spade rudder on a racer , yeah... maybe better lighter. Were probably talking the weight of one jerry can in the lazzerette. Actually less as it weighs less in water right?

[delmarrey]

Originally Posted by Cheechako

Not sure which bearing you mean, but on a boat with a lower bearing I doubt the little extra weight would be an issue.

My rudder weighs around 250# with the shaft in, but would float if the shaft were to break off at the rudder. You did cover the "Ruddercast" with a layer or two of glass?

[Nicholson58]

Originally Posted by Bill G

Thanks for all of the input - here is the current state of affairs:

I am looking for a contractor in the Solomons (MD) area to strip off the blue coating (probably an epoxy coating) with a plane to leave the bottom as fair as possible.

The rudder is at my house. I have ground off the blue coating down to bare fiberglass (a really dirty job!). I have found several spots where the rudder coating had failed and allowed water penetration. Also, the aft edge has numerous gaps. The fiberglass shell is 1/4" on the in-water portion of the rudder and 3/8 inch above the water where the hull connectors are and the tiller connects. The top 1mm of the fiberglass below the waterline has numerous wet spots that I ground down to solid glass. After drilling several holes through the rudder, I have found that the foam core is really wet and about 15% of the interior of the rudder below the waterline is a void - no foam core at all - just hollow. I am planning on taking a large portion of one side of the rudder skin off so that I can remove the wet foam. After inspecting the interior, I hope to be able to replace the foam (any recommendations on weight of foam?) and then replace the removed skin and add a layer of glass to the area below the waterline and add additional glass on the leading edge and the aft edge. I will then barrier coat the rudder below the waterline.

Please refer to my posts and photos. I strongly suggest - Use syntactic foam as filler. Mix epoxy and 3M microballoons to make a pourable mass. I mix 3 gallons US Composite 635 THIN resin with about 8 gallons of balloons using a drill motor and drywall paddle. The mix is totally waterproof and structurally strong (3000psi compressive). I too have dug out rotted foam & black mold from my rudder. I will never use urethane foam or balsa or any other disintegrating material below water again. This foam mix floats. It is low density.

[Bill G]

Thanks for all of the input about the coating. I now believe that the blue coating that was on my Vancouver 32 (made by Northshore Yachts) hull was probably "Nordshield" - Northshore's patented copper filled anti-osmosis gel coat. I got some input from a couple of sources in England and this seems to fit with what I saw.

I am just about to put on the barrier coat now that the hull is ready to go!