View Full Version : Sealing a removeable wooden rudder and centre board for light use

01-16-2017, 08:03 PM
Hi All,

I've read that the best way to seal the components is with Epoxy following by a coat of varnish or paint for UV protection. I've done two coats of un-thickened epoxy which seems to have produced a reasonable finish and was wondering whether the varnish is really necessary considering that these parts will sit in my garage for the majority of the time.

If it makes a difference the Epoxy brand is Norsystems Boat Epoxy:


How sensitive is epoxy to UV? Would it deteriorate noticeably if the components were only out in direct sunlight for a sail once a month or so?


01-16-2017, 08:10 PM
The effect of UV on epoxy resin is apparently cumulative. Each time it is exposed, some degradation occurs. So eventually, even with weeks between use, the epoxy will fail. Eventually.

Is that answer helpful?


01-16-2017, 08:36 PM
UV passes through varnish but not through paint.

01-16-2017, 08:56 PM
I left a kayak out in the Texas sun for 6 months and had significant damage.
Something like you are talking about would not have damage showing up for a long time.
Just don't forget.

Varnish at least would be good insurance for all your work invested.
And not enough weight to matter.

When you notice damage, you will want to remove the epoxy back to wood and start again.
Apparently much of the damage is at the wood epoxy interface.

Unrepaired dings which allow water access to the wood is a much bigger problem.

IMHO (well not so humble)

Peter is right again, paint works much better than varnish for UV protection.

Edit: I got to thinking about your centerboard. Personally I would not just epoxy coat. Epoxy by itself is not very abrasion resistant.
Put a layer of 4 or 6oz cloth down first. The point where it bears on the Cbd case will last a lot longer.

Edit of the Edit: What are you working on? Just for fun.

01-17-2017, 11:04 AM
Bottom line answer, absolutely, you must always protect epoxy, unprotected you will be shocked on how fast it breaks down. A high quality SPAR varnish will protect it.

01-17-2017, 11:51 AM
Most spar varnish has UV filters which make it better at blocking the damaging light from the sun than interior varnish types, but not as much as paint of course. Keep an eye on your foils (rudder and daggerboard) for any darkening -- when you hit something (and you will) the epoxy coating can crack and allow water to reach the wood, causing rot. Keep the varnish coating nice and thick and re-coat when necessary. Even relatively inexpensive spar varnish has decent UV filters.

01-17-2017, 06:00 PM
Thanks Guys, much appreciated. Peter, the paint comment got me thinking much more practically, as you'll see (if I get the photos uploaded) white paint would be a good option. I assume oil based paints are cheaper and more durable than varnish?

I might just leave the tiller varnished and give everything else a white coat. Would have an added bonus of showing up cracks in the coating more readily (and you're right Thorne, my son and I will probably hit every damn thing in this tub).

Here's the story of the boat for anyone interested. My Dad and I built the hull 20 years ago but only went out fishing with a little outboard, thus we never completed the sailing components. After sitting in my cousins garage for the last 15 years, I'm really enjoying finishing the job with intent to teach my son how sail in it.

One problem though, the plans for this are nowhere to be found. Best I can figure it is somewhere between a sabot and a mirror, but with a harder chine than both. I sized the rudder and centreboard calculating under the water line surface area of a mirror and scaling it down to the 2.3m LWL of this dinghy. I found second hand mast and boom from a walker bay 10 sailing kit, and am cutting down a laser mainsail to rig it. Can't wait to see how my amateurish naval architecture skills convert to the sailing experience.

Having trouble posting some photos of it from work.. but can share them if people are interested.

01-17-2017, 06:13 PM
Photos are good.

01-17-2017, 10:08 PM
Here's some photos:


01-18-2017, 11:11 AM
I'd say leave the rudder varnished, but paint the centerboard. You'll want to coat with unthickened epoxy and then fiberglass both, as otherwise that marine ply will get bashed up and start to rot. A thickened bead of epoxy or even a piece of cotton cord covered with thickened epoxy works great along the leading edge and bottom edge of both.

And I STRONGLY recommend changing that rudder to kick-up style -- easy to do by cutting the blade off in a half-circle and adding cheekplates on one or both sides.

https://cvws.icloud-content.com/CAEQARoQBNBo1CnWleu3tyLj-zMgsA/011a85700afa0bac3e7fb055655e24ef34dc4346cc/IMG_0003.JPG?v=0&p=48&x=1&a=BYhRnwqN%2B8m7AyqYOA%3D%3D&e=1484842185000&r=abe68bad-af53-4606-a2d3-7ebc8b17d03f-7&u=1484759085135&c=Ct8ECrsECt4DCjZnY3MtYXNpYS0wMDAwMi5jb250ZW50LXN0 b3JhZ2UtZG93bmxvYWQuZ29vZ2xlYXBpcy5jb20QuwMaA0dFVC LlAS9JZlI1bTdVQldhOW5TWUVDRXdOMT94LWNsaWVudC1yZXF1 ZXN0LWlkPWFiZTY4YmFkLWFmNTMtNDYwNi1hMmQzLTdlYmM4Yj E3ZDAzZiZiaW49NjAzMDAwMDAyJlNpZ25hdHVyZT1OTjcwJTJC VkJheEVrOU5QSUVhVU5CZjhYNkl1TSUzRCZieXRlLXJhbmdlPT AtNjA5ODMyJkV4cGlyZXM9MTQ4NDc1OTA4NTEzNSZHb29nbGVB Y2Nlc3NJZD1HT09HTjJKRlBDRzNXVks1R0NGNyZyZWdpb249YW 1lcndlc3QqBEhUVFAyAzEuMToFaHR0cHNCDQoGQWNjZXB0EgMq LypCKQoRWC1BcHBsZS1PYmplY3QtSUQSFElmUjVtN1VCV2E5bl NZRUNFd04xQhcKBVJhbmdlEg5ieXRlcz0wLTYwOTgzMkIlCgRE YXRlEh1XZWQsIDE4IEphbiAyMDE3IDE2OjA5OjQ1IEdNVEoIZ2 NzX2FzaWFSF2N2d3MuaWNsb3VkLWNvbnRlbnQuY29tWM_gppSb KxIwChWBcxhqO-89_AyN_rkXOMWZp6ASRqcSEQF7bZk-XlSSS25eUtALKnNQGKmcJSAAGhRJZlI1bTdVQldhOW5TWUVDRX dOMSIQQTdTVjJ1bTFhSGFYQXBNNBIfChUBGoVwCvoLrD5_sFVl XiTvNNxDRswSBAgAEAAoACAC&s=ScJuaG7YnADCvS01aIzHiGzJthI

You can add the cheekplates to the rudder head (most common) or to the blade (my dory skiff) -

http://www.grapeviewpointboatworks.com/images/tirrik/tirrik_rudder.jpg http://www.luckhardt.com/kickup-full1.jpg

Here's how to post photos on this forum:

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John Meachen
01-18-2017, 06:39 PM
I like white paint as it makes it easier to spot fronds of weed or pieces of rope.

01-19-2017, 12:29 AM
Yeah I did think about adding a kick up rudder with cheeks. Couldn't figure out an easy way to handle mechanism to move it down and up such that it'd stay there. I'll see how hard pulling the pin on the top pintle and getting the whole thing onboard is before I complicate it.. As you say, it could be easily done later.

After buying the timber I read that marine ply is a bad idea for rudders and centre boards. I figure since this boat is pretty small the chance of 18mm ply succumbing to the stresses of a 8ft boat was unlikely... Anyone think otherwise?

01-19-2017, 01:41 AM
There is nothing wrong with marine ply in that application.
As you said, not much load for that small of a boat.

I second the suggestion for a folding rudder. Just think of how deep of water you would need just to get in the boat.