Rudder renovation - to foam or not to foam?

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InvictaSeb

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Hi there,

I've taken the transom hung rudder off my Invicta 26.

https://photos.app.goo.gl/CBzvPQCaVL1XRT7j8

After taking the the all the paint off right back down to the gelcoat I found a couple of holes had been drilled at the bottom of the rudder to drain water out. I thought I'd best cut out a larger hole to have a look at what was going on inside and was surprised to find no core material at all - the rudder was made hollow.

Should I fill it with polyurethane foam or is that not necessary on transom hung rudder? Should I just patch up the holes and leave it as it was? Filling with foam would involve cutting out a large section of one side, cleaning up the GRP (it's coated in some kind of greasy substance), pouring the foam, fairing it and then re-glassing with epoxy. So Quite a bit of work, but work I'm happy to do if that's what's needed.

You can also see in the photos that I've drilled out the bolt holes that go through to the pintles. I was amazed to find no core in there either, just 10mm thick GRP. For this my plan is just to pour in thickened epoxy to fill the void around the pintle bolts and then glass over them.

Any thoughts would be greatly appreciated!

Seb.
 
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The rudder on my Seawolf 26 was hollow and leaked water. I found that although water did not 'weigh' anything when the rudder was submerged it did have mass and therefore momentum. I had slight vertical play in the bushes and the rudder would clunk up and down with quite considerable force in rough seas. Despite advice to contrary, I filled it with some builder's foam from a can (be careful not to split the rudder as it expands) which solved that problem.

Eventually the welds on the tangs failed and I had to rebuild it. The foam inside (although wet) had maintained its integrity. I managed to make the rudder completely watertight during the rebuild so it's no longer a problem.
 
Thanks for the reply.

It would certainly be easier for me drill a few holes in the rudder and pour foam into it that way. The foam wouldn't bond to the glass though because of the greasy coating, perhaps that's not an issue though?
 
Even if you fill the void with foam, some water will still get in. I think that's what caused my welds to fail along with an over friendly dolphin who thought it was fun to bash his body on my rudder every time I left my mooring.

Ideally, you need to seal your rudder against water ingress which is a much bigger job and may prove difficult.
 
How did you go about sealing your rudder?

I was going to put a layer of glassed epoxy over the whole thing as well, but getting in around the steel parts will be tricky.

Thanks again for the help!
 
having lasted this long there could not have been a lot wrong with what you had, I would certainly be reluctant to split it just to get rigid foam in there, injecting builders foam is unlikely to do any harm and even if it does not bond with the grp a core will add strength. You will get warnings of the enormous pressures that will burst your rudder apart, a cavity wall is a lot weaker than a grp rudder casing and they withstand it no problem. Possible concern though that the metal tangs or their welds may prefer to be in air or water than bedded in foam.
In my experience as an owner of a variety of grp boats, nearly all rudders take water sooner or later, when I first discovered this I used to drill and drain every time the boat came out and it took a few years to learn what a futile exercise I was engaged in. Since I stopped no visible harm has resulted.
 
InvictaSeb said:
How did you go about sealing your rudder?

I was going to put a layer of glassed epoxy over the whole thing as well, but getting in around the steel parts will be tricky.

Thanks again for the help!
Click to expand...

My rudder repair is documented here. http://www.randpsystems.co.uk/seawolf/rudders.htm Scroll down a bit on that page. The dialogue is a mix of my comments and those of the owner of the site.

I used a modified version of Oldsaltoz's (of this parish) O-ring technique to seal my stock. Basically he enlarged an area around the stock and inserted a lubricated O-ring which was then epoxied in. This works on a round stock. You also seem to have rectangular tabs so I don't know how you would seal those. Stainless steel against GRP is never going to stay waterproof.

I also found my rudder was leaking all round the edge so I added a layer of cloth and resin to that.
 
The only thing i would worry about is the area where the middle gudgeon and the lower pintle are anchored in the rudder. Provided these are not exposed to the open void they will not corrode. Seems no sign of corrosion so far. If you seal it all round where the two mouldings are joined with epoxy and tape, no water will get in, but belt and braces suggest a drain plug at the bottom which you can open to check when it is out of the water.
 
I split and rebuilt a rudder for a friend, it was a simple spade (Westerly Longbow) and the metal work was intact so a relatively simple job involving layering and carving rigid foam and extending webs to the tangs and encasing in glass reinforced epoxy. Not difficult but required a considerable amount of time and patience because there were so many stages in the build up. Budget for materials was not much over £100 but time was free.
 
Quandary said:
I split and rebuilt a rudder for a friend, it was a simple spade (Westerly Longbow) and the metal work was intact so a relatively simple job involving layering and carving rigid foam and extending webs to the tangs and encasing in glass reinforced epoxy. Not difficult but required a considerable amount of time and patience because there were so many stages in the build up. Budget for materials was not much over £100 but time was free.
Click to expand...

That's the usual way of doing it but I couldn't do that with my rudder. Like you I found it was not technically difficult nor expensive but it was time consuming. Time didn't matter to me too much as I carried out the repair when my boat was laid up for winter.
 
Thanks for the advice!

The boat is new to me and is a restoration project. My assumption was that when the hollow rudder fill with water, as it definitely would in it's current state, it's mass would be problematic in any kind of seas. I hope that foam filling will at least reduce the volume of water it takes in when water does eventually get in.
 
Hi

I had exactly the same with the rudder on my Invicta (great sea boats and often forgotten about) and it wasn’t until she was onshore for the winter and I tried to lift the rudder off that I discovered it was full of water, for reference didn’t notice any extra weight on the helm so it didn’t seem to affect the helming.
I cut a couple of 3” holes with a hole cutter, let it dry out for 4 months over the Winter, filled it full of two pot expanding foam, any excess comes out of the holes during expansion so unlikely to split the casing, cleaned off the excess foam and then repaired the holes and the one that had allowed the water in with epoxy resin and woven rovings, that was 15 years ago and repair was certainly OK last time I looked, about 5 years ago.
Still miss the sailing qualities of the Invicta, won a lot of races in her even when up against things like Fulmars and S/Seals.
 
I had my rudder rebuilt by a firm in Southampton a few years ago. They made a new stock of stainless tubing welded halfway down to stainless bar. They filled it with foam.
Unfortunately the weld corroded and failed, meaning the rudder broke off. I had to call Riga Rescue. The Latvian navy were very helpful.
 
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