Wet Rudder

[opwan2002]

Has anyone had any experience with drilling and filling a spade rudder with epoxy? I've done this on older Hobie Cat hulls where the foam fill basically disintegrated to fill the void. Can this be done to extend rudder life and postpone eventual reconstruction?

[UNCIVILIZED]

That's definitely like using Fix-A-Flat to repair a punctured tire. It's certainly not the recommended option.

[Suijin]

Originally Posted by UNCIVILIZED

That's definitely like using Fix-A-Flat to repair a punctured tire. It's certainly not the recommended option.

Great analogy lol.

[Tetepare]

I'll go a bit on here in case tyros read this.

Most rudders are a clamshell design with the main post and frame in the middle cored with foam and an external shell of fiberglass.

Water can intrude via several means, primarily via cracks in the shell along the seams, but also in some cases at the top of the strut (e.g., Catalina 30). Also, if the rudder was damaged at the bottom in a grounding. Most likely cause in northern climates is some water that freezes then makes the problem increasingly worse.

A waterlogged rudder has two problems:
1. Weight
2. Corrosion of the strut (particularly in salt water) possibly leading to rudder loss.

In most cases the latter is the serious concern.

Filling a rudder with epoxy will add weight, possibly more weight that the water alone. Note too that the only way to completely fill the rudder with epoxy is to remove all the foam. This could be done by splitting the rudder, but I don't ever suggest that.

Either way, epoxy is not likely to reduce the rate of corrosion of the rudder post/frame, since water is still in there and will be again.

Being up north, my boat comes out every six months for six months. There is saturation of the foam core in the rudder. I drill three 3/8" holes- one in the bottom as a drain, and one on either side (one high, one low) to prevent vacuum, thus allowing water to flow. It takes about a week to dry out. Then I fill the holes (surface only, not injecting anything), finish, and paint.

But I'm in fresh water. If you have a leaking rudder in salt water, depending upon the rate and location of leaking you could be right back where you were in days. There are a variety of "fixes" including replacing the rudder, splitting the clamshell and recoring, and slopifying fiberglass mat all over the rudder to seal it (sealing in the mosture and rust.) Others may have seen other solutions.

[olepedersen]

Lovely new word SLOPIFYING ,works great

[billknny]

Originally Posted by Tetepare

I'll go a bit on here in case tyros read this.

Most rudders are a clamshell design with the main post and frame in the middle cored with foam and an external shell of fiberglass.

Water can intrude via several means, primarily via cracks in the shell along the seams, but also in some cases at the top of the strut (e.g., Catalina 30). Also, if the rudder was damaged at the bottom in a grounding. Most likely cause in northern climates is some water that freezes then makes the problem increasingly worse.

A waterlogged rudder has two problems:
1. Weight
2. Corrosion of the strut (particularly in salt water) possibly leading to rudder loss.

In most cases the latter is the serious concern.

Filling a rudder with epoxy will add weight, possibly more weight that the water alone. Note too that the only way to completely fill the rudder with epoxy is to remove all the foam. This could be done by splitting the rudder, but I don't ever suggest that.

Either way, epoxy is not likely to reduce the rate of corrosion of the rudder post/frame, since water is still in there and will be again.

Being up north, my boat comes out every six months for six months. There is saturation of the foam core in the rudder. I drill three 3/8" holes- one in the bottom as a drain, and one on either side (one high, one low) to prevent vacuum, thus allowing water to flow. It takes about a week to dry out. Then I fill the holes (surface only, not injecting anything), finish, and paint.

But I'm in fresh water. If you have a leaking rudder in salt water, depending upon the rate and location of leaking you could be right back where you were in days. There are a variety of "fixes" including replacing the rudder, splitting the clamshell and recoring, and slopifying fiberglass mat all over the rudder to seal it (sealing in the mosture and rust.) Others may have seen other solutions.

If you have saltwater inside the rudder, as stated, the real concern is corrosion of the (usually) stainless steel structure that actually does the turning by transmitting torque to the shell. These usually corrode, and then fail, at the welds where the web attaches to the shaft. If you have water inside the rudder, the only way to make sure the internal shaft/web is OK is to open the rudder and look at it.

Going in for a look and to properly dry it out is not a huge job for a good fiberglass guy--if nothing is wrong. If something is wrong with the internals, you have a bigger problem to fix, but won't you be glad you found it?

This is one of those jobs if you are daysailing locally, maybe you put off doing... maybe for ever. It's a balance of the cost, vs the risk of losing steering.

If you are taking a boat offshore, rudder failures are way more common then they should be. Ignore your wet rudder at your own risk.

[Tetepare]

Originally Posted by olepedersen

Lovely new word SLOPIFYING ,works great

I am relieved. I was trying to impart the vision in my head.

[Tetepare]

Here's some nice photos of how foam core rudders are made. This shows the parts, so it's easier to see what the problems could be

Rudder Construction | NewRudders.com

[UNCIVILIZED]

Really, the only proper option is to rebuild the thing. Preferably using materials which won't absorb water, nor allow it's intrustion. Such as a mixture of epoxy & fillers.
Foam can work for a core, but if you're rebuilding it (the only real choice for a serious boat), then there are better solutions.

Keep in mind that loss of steerage while offshore is in the top 3 or top 5 reasons why people abandon their vessels. SIC


Note too that there are companies which both build, & rebuild rudders. Such as www.philsfoils.com amongst others.

[billknny]

Originally Posted by UNCIVILIZED

Really, the only proper option is to rebuild the thing. Preferably using materials which won't absorb water, nor allow it's intrustion. Such as a mixture of epoxy & fillers.
Foam can work for a core, but if you're rebuilding it (the only real choice for a serious boat), then there are better solutions.

Keep in mind that loss of steerage while offshore is in the top 3 or top 5 reasons why people abandon their vessels. SIC


Note too that there are companies which both build, & rebuild rudders. Such as www.philsfoils.com amongst others.

It sounds almost like you are recommending a rudder with a solid epoxy/filler core.

That is NOT a good idea. Proper boat building foams do not "absorb" water. They are totally closed cell and are used to give stiffness and control weight. Trying to cast something the size of a boat rudder out of solid epoxy is REALLY hard. The heat generated during cure will destroy the material as it cures. Even if you COULD do it, you'd end up with something hard and brittle--and HEAVY.

The weight, or more precisely the buoyancy, of a rudder on a monohull sailboat is really a rather important design characteristic. A rudder that is negatively buoyant will tend to sink when the boat is heeled over, giving the boat excess lee helm, a too buoyant rudder will float, giving excess weather helm. There are ways around either problem when designing a boat, but they are not easy fixes to implement after the fact. Most boats have rudders that are near neutral in buoyancy so the steering balance does not change as a result of heeling or even just rolling.

The short story: Changing the weight of the rudder in a significant way (either way!) can have a dramatic, adverse, impact on the boat's balance and shouldn't be done without understanding those impacts for THAT boat.

[roverhi]

If you use micro balloons as a thickening agent you wouldn't be adding all that much weight to an infused rudder. The real question is whether you need to. The classic reason is corrosion of armature inside the rudder. Sure that that happens but I'd be willing to bet that most foam cored, clam shell rudders have water intrusion. Trying to get the shaft sealed off seems to be a near impossibility.

Does water intrusion into the rudder add weight to the rudder while it's in the water?? Unless it's displacing deteriorated foam would seem that it wouldn't. Can see it possibly having some effect on the pitching forces on the hull possibly contributing to hobby horsing but, if the foam is still in place, would be minor.

Biggest problem with a water logged rudder is for the Blue Nose types who live in inhospitable climates that freeze. Wouldn't take a lot of water turning to ice to force the two halves of the rudder apart. Might want to swiss cheese the rudder to be sure there is little, if any, trapped water in large enough quantities to cause the rudder to split.

As far as internal corrosion, seems about the only way to prove that's not an issue is to tear into the rudder and inspect the rudder stock/armature interface. That would be a boon to the boat yard business as almost every boat would qualify for such an inspection.

From casual observation, most steering failures seem to be loss of rudder from corrosion of the rudder stock in the hull bearing interface, bending of the rudder from contact with a foreign object or failure of the boats steering gear. Can't remember hearing of any that have lost steering because the rudder shaft is turning inside the rudder blade. That's not to say it couldn't or hasn't happened, just that it doesn't seem to be a big cause of steering failure.

If you can identify voids in the rudder, filling with microballoon thickened epoxy is a possibility. Would definitely glass over cracks in the joint of rudder halves after allowing it to dry out for awhile.

[UNCIVILIZED]

Originally Posted by billknny

It sounds almost like you are recommending a rudder with a solid epoxy/filler core.
To a degree, yes I am.

That is NOT a good idea. Proper boat building foams do not "absorb" water.
Funny, I've seen & worked on quite a number of soggy/sodden foam cored boat hulls & rudders. Some amount of the water therein could be attributed to kerfs not being fully filled. And or, water getting between the skins & the core. But by no means was the foam dry, & in some areas it was in fact soggy all, or most of the way through.
Besides which, there are plenty of foam cored rudders out there which weren't built out of top notch structural foam at the factory. And some of that stuff Definitely absorbs water.

They are totally closed cell and are used to give stiffness and control weight. Trying to cast something the size of a boat rudder out of solid epoxy is REALLY hard.
I mentioned naught about casting anything using solid epoxy.

The heat generated during cure will destroy the material as it cures.
If one attempts to use neat resin (resin sans fillers) in any quantity, then yes, it'll go exothermic on you. But by using the correct resin, blended with the proper fillers, this won't happen. And one needn't attempt to build it up to the full thickness in one shot anyway. Needs be it can be done in stages, so long as one adds new material on top of what's already been "poured" while the former layer is still green.

Even if you COULD do it, you'd end up with something hard and brittle--and HEAVY.
Not really. There are all kinds of low density blends of epoxy & fillers. For example some of the ones used in fairing hulls. Both structural fairing, and cosmetic ones used prior to priming & painting. Some of that stuff is about as dense as marshmellows.

The blended filler is the rudder's core in lieu of foam. But by virtue of being epoxy based, so long as you use filling agents which are hydrophobic, then it can't absorb water. Nor, given the proper filler materials, will it be particularly brittle. But the thing is, the rudder will have substantial fiberglass skins, so that the core will see little in terms of impact energy. These will be borne by the rudder's shaft, armature, & the glass that's bonded to the rudder's shaft. And or fiberglass foil sections which are bonded to the shaft.

Also, such a rudder will be a monocoque structure. So that there won't be any bond internal bond lines, as there are between foam & glass, which might allow water to enter & reside within the rudder. Such a core will also have smaller differentials of expansion & contraction between the skin & cores than will a foam glass rudder. And it can be made fully watertight (not that it isn't already) by virtue of the fact that the core, composite framework, & skins, are structurally bonded to the rudder shaft.

And as to brittleness, at the moment I'm not 10' from some composite structures build using epoxy & fillers as core, in conjunction with structural glass skins. And you could pound on them all day with little effect. At least until you smack them hard enough to damage the integrity of the skins.

Also, if you do the math on core densities, the diffence, if any, in weight between a rudder cored with high density foam, & one cored with a blended epoxy filler is pretty small.

For example, a good number of rudders are built using 20lb/cuft density foam. And, for the sake of argument, let's say that you used an epoxy blended filler with a density of 40lb/cuft.
If the rudder displaces 1cuft of water (realistically it'll be less than this), then there's a difference in mass of 20lbs between the two. Nothing huge by any standard. And this is pretty much what the difference would be if you were to core the rudder with marine plywood instead. And many solid wooden cores would be even denser than this. Resulting in an even bigger difference in overall rudder weight.

But then you need to take into consideration that all of these materials "weigh" less when immersed, as water weights 64lb/cuft. So just like foam, or (most) wood, a properly blended epoxy/filler core will float.

The weight, or more precisely the buoyancy, of a rudder on a monohull sailboat is really a rather important design characteristic. A rudder that is negatively buoyant will tend to sink when the boat is heeled over, giving the boat excess lee helm, a too buoyant rudder will float, giving excess weather helm. There are ways around either problem when designing a boat, but they are not easy fixes to implement after the fact. Most boats have rudders that are near neutral in buoyancy so the steering balance does not change as a result of heeling or even just rolling.

This one perhaps makes sense in theory (maybe), but... If both the husband & wife on a boat are standing by the helm, directly overtop of the rudder, don't you think that this might affect the hydrodynamic balance of the boat just a wee bit more than a "heavy" rudder?

Heck, just a pair of full LPG tanks in their lockers at the aft end of the cockpit will have more effect on how deeply a boat's aft sections are immersed than will differences in the buoyancy of the rudder.

The short story: Changing the weight of the rudder in a significant way (either way!) can have a dramatic, adverse, impact on the boat's balance and shouldn't be done without understanding those impacts for THAT boat.

I've built more than a couple of rudders, including one was for a 25' O'Day. The replacement rudder was plywood cored, vs. foam in the original one, & it was much larger, overall, than the original, & was sheathed in fiberglass. So that it probably weighed 30lbs more than the original one. And I can tell you that without queston, the boat performed light years better with it than was the case with the original one despite being "heavier". Something to which no less than 3 America's Cup sailors attested to when sailing & helming the boat after the mod'.

FWIW, the new rudder could have been built out of solid glass, & a cooler full of beer at the aft end of the cockpit would have had more of an effect on the boat's balance/floating on her lines than such an overly porky rudder.

[Cheechako]

I did a rudder on my 44 footer. I cut a big window on one side of the rudder, scraped out all the wet foam, dried it out well and inspected the stainless steel. I then fiberglassed the window back on the rudder. (tapered edges and layed up) I cored two holes 3/4" in the top of the rudder and filled it with a lightweight blue product called "ruddercast". Not sure if it was poly or epoxy. Supposedly it was developed to make cast/unsheathed rudders for powerboats... maybe for the vietnam war riverboats.(rumor) Anyway, I just filled the rudder from the top until it came out the second hole. Worked great.
If you dont open up the rudder it may never really dry out, just condensate inside.
Things to remember:
-Hardened lightweight epoxy slurry in water will not weigh much more and maybe less than water.
-All foams absorb some water, even mil spec. They also shrink back allowing water intrusion in the gap. Then they soften and just continue softening.
-"Changing the weight of a rudder..." uhh... when it's got water intrusion it has already changed some.

[a64pilot]

The whole deck of an Island Packet is cored with something akin to resin and micro balloons. I have heard it described as being like shaving cream.
It is supposedly impervious to water, and I have never heard of an IP with a wet deck, I don’t think they can get wet.
Maybe use whatever IP uses in their decks? It is several inches thick, my deck if you look at where the mast comes through the hull is three or four inches or so thick.
However I know my rudder is foam filled, cause I think IP bought their rudders and didn’t build their own.

[Cheechako]

Originally Posted by a64pilot

The whole deck of an Island Packet is cored with something akin to resin and micro balloons. I have heard it described as being like shaving cream.
It is supposedly impervious to water, and I have never heard of an IP with a wet deck, I don’t think they can get wet.
Maybe use whatever IP uses in their decks? It is several inches thick, my deck if you look at where the mast comes through the hull is three or four inches or so thick.
However I know my rudder is foam filled, cause I think IP bought their rudders and didn’t build their own.

I had not heard that about IP. Kudos to them for trying to solve a long standing problem.
I remember in the late 90's thinking of buying a Wauquiez boat new. At that time they had developed a cored hull with a similar sounding foam. They had hull cutout samples at the sales office. The foam was thick, 1" to 1.25" IIRC. Hard as a rock. I dont know if they ever continued forward with that or not as I havent heard a word about it since.