filling a hollow rudder

[simon_sluggett]

my cobra 750 has a hollow rudder which has filled up with water. I have drilled some holes and drained it all out. Could I fill the void to stop this happening again, with either resin or builders foam (the cheaper option) or should I just try to seal up any leaks on the outside. Cheers Simon

 

[Swagman]

You may wish to leave well alone.

Suspect you'll have difficulties using builders foam to try and plug it - all you'd do is ensure water which makes it isnside will stay trapped in future.

Hard to keep water at rudder depths out of anything partially hollow - so filling with resin may be one solution.

I'd suggest an epoxy resin - mixed to cure slowly - and poured in the top is best bet.

Wait until you see it begin to exit the base before plugging that exit with tape, and ensure you have a third hole to act as a vent on top alongside your pouring hole.

Give it all a couple of weeks to go off and suspect thats as good as you will get - but remember it will then be heavier than it's ever been - and could therefore could effect sailing trim.

Cheers
JOHN

 

[halcyon]

Both the Hurley 27 and the Halcyon 27 had water in there rudder when we bought them.
The Hurley had a galvernised rudder stock moulded in, this has started to to rust causing the rudder to split. We had that one rebuild with stainless stock and filled with resisn. Found the tiller heavy after due to the weight of resin.
The Haclyon we drained and left over the winter in a warm dry place to dry out. It was the filled with a two part foam, and the filling and vent ports glassed over. This gave a lighter rudder, and the helm seems lighter, or should I say the same as before.


Brian

 

[JasB]

Before I start, I know nothing about rudders, but are they designed to be hollow, or is it just poor workmanship that has left the rudders with voids?

 

[boatbuilder]

If you fill the rudder with resin, poly or epoxy do it in batches, as the mass of the mix to fill the whole job in one go may cause exotherm and damage the rudder. It maybe better to leave it as is, the only rudder that is water proof is steel plate!

 

[mikejames]

I second that : having made pots of resin smoke , I would fill the rudder slowly or you might not have a rudder left.

A pity the rudder is totally submerged. If it had been transom hung you could have left it hollow and inserted a tube to the bottom (and a vent) then pumped it out from time to time . It would not have had the weak point where the stock enters the blade at the top and the bottom.

As an alternative you might be able to seal the stock to the blade using something like a ring of Sikaflex in a small trough around the stock. You could protect that with a layer of fibreglass.

 

[boatmike]

You need first to drill some quite large holes in the top of the rudder. You need at least two. One to pour the foam in and one to let the air out. More is better to see what is going on. It's best to take the rudder off the boat first and dry it out indoors thoroughly. Then mix up a good quality syntactic foam and pour in to the hole. Builders foam is not really good enough. Visit your local GRP supplier for the right stuff. DONT POUR TOO MUCH AT ONCE or you will blow the rudder apart. Fill in stages until the last fill spills out of the top. Then seal up the holes with a GRP patch. This treatment will add strength to the rudder and stop it leaking if done properly. Good quality syntactic foam is closed cell so won't absorb water and will adhere well to the rudder halves. Don't fill it up with resin as the weight alone will be considerable and it will be too rigid and crack. As others have said the exotherm will also be awful and cause distortion by overheating.

 

[starboard]

Dont fill with resin, you will add too much weight to the rudder. If possible I would try and address the reason for the water entering in the first place.Dont know the make up of your rudder but probably coming in through shaft if fitted or fixings for pintles. The problem with water getting inside some French manufacteres rudder is the fact that the tangs that are metal and hold the rudder to the shaft tend to rust away at the welds and cause failure.


the best option is every time you come out of the water for winter, drill a couple of 10mm holes in the bottom of the rudder to drain out any water accumulated, plugging these with epoxy prior to relaunch.

Pau.

 

[Poignard]

I`ve had this problem with a Twister rudder which is made in two halves which were simply butted together and glued with polyester resin. This joint had started to crack open, especially near the pintles, allowing water to seep in.
I drilled tempoary drain holes and allowed it to dry out, then ground a shallow Vee all along the join and then built it back up to the original shape with many layers of glass tape and epoxy. I did that 3 or 4 years ago and it doesn`t leak anymore and is presumably much stronger than originally.
The only minor snag is that I had to paint the rudder post to hide the epoxy joint.
I debated whether or not to fill the rudder with foam but decided not to because I want to know if my repair fails. If it has water in it you can hear it sloshing around if you swing the rudder [when the boat is out of the water, that is]

 

[oldsaltoz]

G'day Magwitch/Simon,

I would never use builders, or other expanding foam below the waterline as they are doomed to fail, this stuff is not meant for this and should not be used, you will end up with a rudder full of mush and so contaminated that other repair options may not be possible.

Many rudder manufacturers (most commercial builders don't make their own) produce hollow rudders to provide added buoyancy to counteract the weight of the rudder stock; others make them hollow to save on costs.

I Hope this helps......



Filling a rudder with resin would make it heavy; however, filling one with resin and closed call balloons will add very little weight and provide a long term cure, as well as protect the internals.

Common leak points are the rudder stock entry point and seams in half moulded rudders. I have very good results by adding two '0' rings to the rudder stock and glassing them in, you need to put a smear of wax on to prevent resin getting in between them. Moulded rudders can be ground and re glassed.

To fill a rudder with a mixture of resin and closed cell balloons you need to first make sure the internal area is dry, flushing it with methylated spirits then a final flush with acetone will speed things up as both take up moisture readily, the Acetone will also remove most contaminants.

The method I use is as follows: drill a hole about 20 mm at the base, and then 10mm holes every 50mm up the rudder. Using a plastic syringe available from most chemist shops (cheap) inject the mix from the bottom and close the hole with tape when you see your mixture. Use only epoxy resin and only closed cell balloons.