Using epoxy coating on teak rudder

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andyorr

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My Shrimper rudder is now stripped back to bare wood. There is some damage to one face (prop?) and some end grain damage in places. Is it appropriate to use West epoxy as a protective coating below the waterline and above instead of varnish?
 
I do not have experience of a teak rudder.My rudder is made of mahogany. It is fabricated from 6 by 2 inch planks over the blade, and is 4 inches thick at the stock. When I took over the boat from my wife's cousin Mike, she was in Westport Mass. and I was planning to sail her back to the Uk. I asked Mike if he thought she was fit for the trip. His only concern was that he had discovered a split in the rudder when he was down in the caribean. At that time he cut out the area with the split and scarfed in a new piece of mahogany. So to be on the safe side I removed the rudder and sanded it down to expose the repair. The repair was sound, the plug was bonded with no voids or signs of the crack. However to be absolutley sure I laminated over the entire rudder blade below the water line. After sanding back to bare wood, I sealed the surface with epoxy. The lay up was 1st layer CSM, 2nd layer woven rovings, 3rd layer CSM, all using WEST epoxy. I then coated the surface with 3 more coats of the epoxy for fill in some of the unevenes of the surface. Finished off with 2 coats of AF. The only problem I had was that when I put on the first coat the underside was ok, but the top surface developed bubbles in the coat. This was due to the sun heating up the top surface so the work had to continue inside. Seven years later I removed the rudder again and stripped off all of the AF. The majority was removed by scrapping, but the area at the bottom of the undulations was removed by caustic soda mixed with wall paper paste this was a suggested in PBO. The rudder looked ok. I then filled the surface by mixing epoxy resin with micro balloons to make up the filler much cheaper than buying it. The final filling was done using Venitziani fine filler. The whole rudder was then painted with epoxy primer followed by Venitziani 2 pack u/coat and 2 pack PU. results V good. So I can definitely recomend encapsulating a rudder in epoxy.
 
A good point about the wood though! Is my rudder teak or mahogany? Shrimper owners, do you know? I was worried that, as an oily wood, epoxy wouldn't adhere well enough to teak to last. If it is mahogany, no problems I think.
 
Ive done a fair bit of work with epoxy.... glueing, covering with mat and filling prior to painting. The epoxy will bond extremely well to both mahogany and teak for any of these uses. What you need to do is vigoursly clean down the timber with a rag and acetone prior to using the epoxy. This dries up the natural oils and helps with bonding.
Personally I would only use lightweight woven cloth as a covering. I would definately not use CSM.

Colin
 
Colin is right, CSM and epoxy should not be used together under any circumstances. If using epoxy use woven cloth or woven rovings.
 
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CSM and epoxy should not be used together under any circumstances.

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Are you saying this because of the bonding agent in CSM? If so, you can get powder bonded CSM which works very well with epoxy, such as the last item on this page from CFS.

If it is for some other reason, I'd be interested to know why.

(I don't think I'd use CSM for sheathing a rudder, anyway, but for laying up awkward shapes it's very handy.)

Andy
 
I was thinking of using the epoxy as a varnish substitute (with no fibreglass). This would protect and preserve below the waterline and make it look nice above.
Any thoughts?
 
Andy,

West epoxies AFAIK are not UV-resistant. You'll have to paint/varnish over the epoxy. That said, it can be applied as previously recommended, removing the oils with acetone first. Have the rudder and epoxy as warm as possible before applying the epoxy as it will encourage the epoxy to penetrate into the fibres of the wood.
 
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I was thinking of using the epoxy as a varnish substitute (with no fibreglass). This would protect and preserve below the waterline and make it look nice above.
Any thoughts?

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Erm.. I'm not really sure, but I thought that epoxy on it's own was prone to cracking as the wood 'moves', thus allowing water in behind it to the detriment of the wood and the coating.

I also believe that it's not UV stable, and needs to be varnished, or otherwise protected if exposed to sunlight.

Fine glass cloth / tissue will disappear in the resin, and leave a pretty much transparent coating. I understand that the wood needs to be very dry before you seal it this way, though.

Waiting for someone more knowledgeable to comment.....


Andy
 
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There is some damage to one face (prop?) and some end grain damage in places. Is it appropriate to use West epoxy as a protective coating below the waterline and above instead of varnish?

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G'day Andy,

Coating any timber without glass reinforcing is prone to failure, topping it with several coats of varnish will help, but it's high maintenance and cuts into your time on the water.

Epoxy bonds very well and cures much harder than standard resins, because its hard it is also more brittle and may crack.

If you must have a timber finish there are a few alternatives ranging from clear resin and all but transparent cloth that I have seen cracked, to painting a timber finish over the glassed item.

Some things you should do would include:

Make sure the timber is very dry, the epoxy will lock any moisture inside and this will cause a failure.

You can mix Methylated Spirits up to 40% by volume to thin the resin ensuring a deeper penetration, this not only helps the moisture out but will also add a little strength.

You can then fill any damaged areas with closed cell balloons, spheres or 'Q' cells, all are very easy to sand back to the required shape or profile. Then add a couple of coats of resin to protect the whole rudder before doing any more work.

You can avoid the need to sand between coats by applying wet on tacky. But, if you have to let the resin cure and start adding more later, do not sand it till you have washed it to remove the residue left by the curing process. A simple plastic kitchen scourer and a running hose is all you need it only takes minutes, with the hose running, start at the top and work down, rub the surface till the water no longer forms beads, then sand with a 200 grit, just enough to remove the high gloss and make sure you use a block when sanding or it will have ripples.

If you decide to encapsulate the timber (and I would) you can use 2 layers of 100 to 150 gram stitched Bi axial cloth and and one layer of very light roving's, then 3 coats of resin, wash as above before sanding or applying any epoxy primer.

The reason CSM (Chopped Strand Mat) is not recommended for use with epoxy resin is the large voids that will need to be filled, this means much more resin is used and the end product has less strength than cloth, so why pay more to get less?

I hope this helps.

Avagoodweekend......
 
The reason why I used The CSM in the layup was due to the fact that I could not get the woven rovings to go around the edges of the rudder without lifting up. As the rudder had split before, I wanted to increase the strength of the rudder as much as posible. The woven rovings were used on the basically flat faces of the rudder as closed to the edge as I could manage without them standing up. I discussed the problem with the staff at the boat yard, and they supplied the epoxy and CSM. The layup was applied using a brush and roller the CSM wetted out ok, and all three layers apeared to be consolidated without any voids. I would have thought that if it was all still in good condition 7 years later that proceedure was ok. However I was interested to hear that several people said that CSM and epoxy are not preferered, What is the reason?
 
Hi,
What's wrong with just oiling the rudder? It's tramsom hung (?) so there's not really even any need to anti foul it. Just give it a wipe every now and then to remove growth. I used to have a solid mahogany rudder on a previous boat and I only oiled it. That was 15 years ago and it still looks good. As to which oli, well anything really. I used boiled linseed oil, olive oil anything really. In the winter I just sat the rudder in a bit of oil. It looks and smells lovely and it is not rotting.
Nicki
 
Probably telling you something you all already know, but west have an online manual here: http://www.westsystem.com/webpages/userinfo/manual/
Very helpful.

I have two related questions: 1) After using the resin to embed a cleat I left the mixing pot outside. the mix set, and then it rained, and I found the water inside to be brown. What is that? The oxidised sheen on the surface dissolving off perhaps?
2) Adding the balloon filler to the mix makes it thicker and also stronger (I believe). But does it also make it more brittle? To what extent?
 
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