Painting my rudder

[RobH912]

GL - have gone through many posts on building a rudder, repairing a rudder, etc. and looks like your recommendation for paint to use is the WR-LPU from System Three.

https://www.systemthree.com/products/wr ... ne-topcoat

My rudder needs a little sanding, maybe light fairing on some spots, but wanted to then paint it.

Some of these posts are old and just wanted to check that this is still the current recommendation.

Thanks!

[GreenLake]

Rob, while I still strongly endorse the clear WR-LPU over epoxy on wood (e.g. thwarts, etc.), I've run into issues with stress cracking with their white on fiberglass (presumably from hull flexing). That said, the paint job on my rudder (white) has held up pretty well, and I have been able to apply that paint using roll & tip for a really smooth surface.

Another alternative is EasyPoxy from Pettit. If allowed to cure well, I found it amazingly durable. Be aware that it stays quite soft for a day or two, but that's deceptive. They sell a brushing thinner for it, and you may need that to get it to apply smoothly enough for a foil.

[RobH912]

Green Lake thanks for the reply and additional thoughts on EasyPoxy. If I do paint rudder I think I will use the WR-LPU white.

Have taken a closer look at the rudder and other than the forward edge of the foil, may not need to repaint. The leading edge still looks like epoxy over wood, looks sealed, it's just that paint has worn off leading edge. Sides of the rudder are not that smooth, and there has been some fairing done before.

I am going to first try a little scrubbing and then lightly 300+ grit wet sanding on the sides to see how rudder may clean up / smooth out.

Closer exception I have also found the Whale logo on one pintle, the entire rudder & tiller maybe original.

This rudder and tiller is heavy (20 lbs !), certainly much heavier than the SLI rudder and tiller.

[RobH912]

one more picture

[GreenLake]

That's an original rudder which would put doubts as to the presence of wood in the rudder blade. If it has been faired before, it might have been with epoxy with wood dust or a colored fairing compound.

That rudder has all the shortcomings that lead me tobuild a new one.

[RobH912]

Green Lake - thanks for the additional thoughts on the rudder and your thoughts that it looked original. Had a couple more questions and some pictures as I started to clean up and lightly sand the rudder before painting.

That's an original rudder which would put doubts as to the presence of wood in the rudder blade.

What were the original rudders made of if not made of glassed over wood / plywood?

As I look closely at the leading edge of the foil where the paint & gel coat have worn down, I can clearly see what looks to me as the layered cross section of plywood, with a clear epoxy over the edge. It is hard to get a good picture. Went through a lot of the previous owner's posts on restoring # 2444, but see no mention of work or building a rudder for this boat. However I do see other posts where he is providing comments on building rudder or heads to others and that he built rudders & heads. May have used original hardware?

Once I gave the rudder a good scrubbing I did a light sanding with 320 grit paper as the surface still felt pretty rough, and then saw that the rudder has previously been painted. I could see some hardened drips.

I had mentioned earlier that I thought that there had been some fairing / filling done to the rudder, because I could feel that the surface had some ridges, and on one side a small bulge. There are two parallel ridges running top to bottom on both sides. When I started to sand the ridges and valleys are now easier to see, and when I get through the paint it looks like gel coat. Not sure what is causing the ridges but it is under the gel coat. See pictures below.

Not looking for perfect, but don't know if I should keep sanding off the gel coat to make the surfaces straight edge flat before painting with WR-LPU white or not. WDYT?

There are a couple of small scratches that I want to fill. Is there a good, pre-mixed, in the can filler that would be good for this application? I've used Marine Tex before, but I always end up mixing it all up to get the right proportions, which is wasteful.

Also with the WR-LPU paint should I be also purchasing their "Crosslinking hardener" option for painting the foil?

Thanks!

[GreenLake]

The rudder (and CB) are the places where you really want a "perfect" surface. If necessary, you need to use epoxy fairing filler to smooth things out. You definitely do not want any grooves like the one on your picture.

Before painting, there's a limit to how high a grit number you should use. The paint will fill any sanding grooves of a certain size and if you sand too finely, you may make it harder for the paint to adhere. Some of the paints will tell you on the package, but I'd say that 320 is probably not bad for prep sanding. Once the paint is applied, you may sand lightly with a 1000 or 2000 grit, sometimes that works better than leaving the paint as is. (You definitely don't want any brush marks).

The better the surface, the better the rudder will work; there are limits due to the fact that yours doesn't look like it has a very good profile, but you still want to do everything you can to not disturb the flow.

My original rudder has rust stains. So I know there is metal in it. I think the core is some sort of fiberglass or foam. The thing is really heavy compared to my rebuild (wood) and sinks (my new one floats).

However, it's impossible to say for sure because someone may have replaced the blade while matching the shape so well that you can't tell it apart from an original in a photo. Mine definitely does not have any detectable/visible wood anywhere, and I can tell it's original in ways that I couldn't from a photo.

[GreenLake]

I like SystemThree's "Quick Fair". It's two part, but unlike some other systems, you don't have to guess on the consistency. The mixing isn't hard, the measuring a bit tricky because it doesn't "level" like a liquid in a measuring cup, so you might need to mix an amount that corresponds to a full measuring cup: you mark the 2/3 level, fill it with the one part, tamp that down so it's level at the mark and then fill with the other part to get your 2:1 ratio. (I have gotten away with eyeballing the ratio, but with epoxy it's always better to measure).

For the WR-LPU you add the cross-linker to the last coat.

(because the rudder profile doesn't look all that good, you could try to use filler to give it a more rounded entry and to move the point of max width to about 1/3 from the front. In that case, I would use 3M High Strength Marine Filler, a Polyester based product that is fiberglass reinforced and will stand up better in places where you want to to stand proud of the surface.)

Here's a trick if you need to add "thickness" to a surface: you use a notched spreader for the first pass. That leaves raised ridges. You then fill the valleys in the second pass (after the ridges have cured).

[RobH912]

Green Lake - great information.

I'll look at the SystemThree's "Quick Fair"... and as you have said in other posts, stick with one brand as their products should all work together.

I have read about laminar flow, and do understand what you are saying about getting rid of the set of ridges / valleys on the rudder... so my question is should I be using filler, and adding weight and size to smooth out the foil, or just putting heavier grit sandpaper on the orbital and take the higher gel coat down / off?

The ridges look pretty high in the pictures since the paint color is slightly darker than the gel coat, but they are not and it would not be that much effort to sand it all down.

Thanks!

[GreenLake]

Rob,

obviously, if you had a solid piece of material, then grinding it into shape is fine. I'm worried about that whatever you have is skin/core, such as, perhaps, a fiberglass skin on wood. You don't want to sand through such a skin layer, if it's the one that gives the panel its strength. Gelcoat does not add strength; you can sand through that all day long.

If your core is wood everywhere, you can sand it into shape and then add a layer of glass before fairing and painting. You still may want to make the forward third a bit thicker by adding some filler, and make the entry rounder (should be like a 1/2" diameter circle right at the entry).

The standard rudder looks like a < = >: short diagonal ramp, flat, short diagonal ramp. Qualitatively, what you want is round entry, medium fair curve to max camber at 1/3. And fair curve to 1/8" flat exit, not at 90 degrees but angled a bit. The actual profile should match one of the airfoil curves, but I'm not sure that's feasible. (You could sand down to wood, lay down a couple strips of glass around that max camber location, topped by a bit of plywood) and then sand those down. FG strips going down the spine would strengthen the blade.

(You may need to read the above more than once, because different paragraphs are maybe making different assumptions of what state your rudder is after you've sanded it).

[RobH912]

I'm worried about that whatever you have is skin/core, such as, perhaps, a fiberglass skin on wood. You don't want to sand through such a skin layer, if it's the one that gives the panel its strength

GL Yes, after my last post I too was thinking about not knowing what I would be sanding off and I think your original suggestion to add some fairing compound is a better idea.

I'll now order some of the SystemThree "Quick Fair", WR-LPU paint, and "Crosslinking hardener"

It will take awhile to get delivery, and will post an update when I make some progress.

Thanks!