Teak cap rail sanding necessary?

I have bare teak caprails on my Selene and want to use Semco teak sealer on them so this has been decided. Quesion is whether i really need to sand them smooth before applying the Semco and sanding between coats. I like the rough feel of the teak and would like to apply the Semco without sanding or just make a quick sanding to begin with and nothing more.

Any issues with this? Does the sanding somehow make a better surface to keep teak in good shape as it weathers? I have owned a different Selene with nice lacqured cap rails but the upkeep is too much and I prefer to "feel" the wood.

Semco is great stuff. I use it on my decks. I am a big fan.

But, two things:

1) It works mostly by soaking in a bit vs building up at the surface. If it builds up on the surface it just flakes/dusts off (eventually)


2) It wears off every 2-3 months like clockwork, depending on pigment level and amount of sunlight, and requires an additional coat (or two for clear). I get 3 months out of Gold Tone. One of my neighbors seems to get less than 2 out of clear. I like it despite this because reapplication is super easy: I wash the decks with disk soap, water, and a deck brush one day....and apply a fresh coat of Semco the next. The semco takes an hour. The washing of the deck takes longer.

Since it needs to soak in, for the initial application, it needs to be able to do that. The surface needs to be prepared by sanding or with a teak brightener. For subsequent applications, it needs to be soap, water, and deck brush clean.

If this isn't done, surface contamination will prevent it from soaking in, so the very, very thin surface layer will have nothing to protect. The wood will remain a sponge and heating and cooling and humidity and condensation will drive moisture in and out.

So, yes, you need to use a bleach-type brightener or sand, at least for a predictable, consistent good result.

I guess I should be clear. The Semco won't care if the rails are smooth. It'll just care if it can penetrate. If you like the texture, just use a brightener vs sanding.

Having said that, water rolls off smooth surfaces better than coarse grainy surfaces. Semco slows, but does not prevent, water soaking into wood.

I'd suspect that the more texture you've got on that wood, the longer it will retain wetness at the surface vs rolling off, and, as a result, the shorter the lifetime of the Semco and the wood.

Semco,of which I know nothing,and Deks Olje, of which I know something, are different products. But,I think the latter advised against very smooth sanding as it impeded the oil soaking in.

The semco instructions don't actually recommend sanding at all. They recommend chemical brightening for old teak and a couple of weeks of weathering for new teak.

BruceK: The same concern you describe about super-fine sanding applies with Semco.

I think I did mine enough to mostly get off the old finishes and then very quickly and lightly to 150 grit or 180 grit (I forget).

When I did mine I sanded so little that, in the photos, you can still see the less lightened rectangular area from the door Matt that sat for years at the entrance.

The key is that the surface be clean so that the semco can penetrate. Sanding is just one way to achieve that and /very/ easily over done.

I've attached "Random Tuesday" pictures of mine from my camera roll. Don't know why they were taken. I think it actually looks better with more consistent color and shade these days with some of the prior variation from uneven aging having settled in. But, I can't grab a new picture at the moment.

This vacation I had a few days with a pair of boats that had both perfect varnish on the rails and Semco on the decks. Then another boat came along who changed the appearance of his decks by applying Semco, in front of us.
The first 2 boats had the decks sanded to new wood, then Semco. This was an annual routine (in SW BC, where things last a lot longer than in lower and hotter latitudes). The newcomer cleaned, but did not sand. There was no difference in appearance between the two approaches, except that the newly applied Semco seemed thicker.

I haven't seen Semco used on rails yet. Compared to Varnish, I wouldn't use Semco for rails. I doubt the amount of work to keep up the Semco differs by enough to justify the work boat look.
The advice above, to sand or to use a chemical brightener, will each erode the teak, so unless your application is the last before getting rid of the boat, I wouldn't do it. Both regular sanding and regular use of chemical brighteners will remove so much wood to get through the sun damaged wood, that you limit the lifetime of the teak unnecessarily. Varnish can be re-done for decades without sanding to bare wood.

We used Semco on our decks for years and liked it. It kept the teak decks from loosing their natural oils and helped seal the teak to a point but we still lost soft grains. For that reason we didn’t use it on the caprails. That’s where varnish and other hard finishes shine.

In Michigan we put Semco on once a year on the teak decks. The handrail and toerail got painted white with Brightside. Loved both.

koliver said:

The advice above, to sand or to use a chemical brightener, will each erode the teak, so unless your application is the last before getting rid of the boat, I wouldn't do it. Both regular sanding and regular use of chemical brighteners will remove so much wood to get through the sun damaged wood, that you limit the lifetime of the teak unnecessarily. Varnish can be re-done for decades without sanding to bare wood.

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Just to be clear, my advice was a /light/ sanding or chemical brightener /exactly once/ before the /initial/ application.

I absolutely would recommend /against/ doing it more often than that for exactly the reasons you describe.

I keep telling neighbors that like to sand or chemically brighten their decks, "You know that teak is long dead, that won't grow back."

My opinion

No. But it would result in better adhesion.
But if I was going to recoat w/o sanding I’d preform a complete appropriate solvent wash.

Unless it is already really worn one light sanding won’t hurt it. Continually sanding it will.

Thank you for your input. I am cruising in the Med - Italy, Greece and Spain mostly so you have an idea of the weather. I bought Anna in Norway 3 years ago and have noticed more wear on the caprails since I brought her down to Italy 2 years ago. So that's why the idea to protect came to mind.

There are a few other Selene owners here (Varazzze, Italy) that use Semco on their caprails and other teak with success. Yes, there is a bit more maintenance, but it is simple. I am moving slips to Barcelona and this fall when it is a bit cooler, I will have the teak cleaned and then will apply Semco. Will send pics then.

Here's a couple pics of the current state of the caprails.

Slightly off topic but I will ask. My older teak decks are hot hot hot in the Florida summers. Is Semco any cooler? I have entertained putting on my flybridge but only if it has some cooling effect.

firstbase said:

Slightly off topic but I will ask. My older teak decks are hot hot hot in the Florida summers. Is Semco any cooler? I have entertained putting on my flybridge but only if it has some cooling effect.

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I doubt that it will be cooler. It is the dark color of the teak that is absorbing the heat.

dmbraaten said:

Here's a couple pics of the current state of the caprails.

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The roughened surface you like results from weathered teak losing soft material between harder material. If it continues the grooving will deepen and deepen. I suggest sanding it flat, and hoping the Semco application arrests the process.

Semco to me is like Thompson water seal for teak. I think it works best on bare teak.

Comodave said:

I doubt that it will be cooler. It is the dark color of the teak that is absorbing the heat.

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that's what I was thinking. I just remember reading in here somewhere that someone had cooler decks with Semco. that may have been true in his/her case as there are other variables involved.

BruceK said:

The roughened surface you like results from weathered teak losing soft material between harder material. If it continues the grooving will deepen and deepen. I suggest sanding it flat, and hoping the Semco application arrests the process.

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Good point. I assume sanding means something in the 220 grit with hand sanding using a sanding block.

Personal preference dictates what to do. Mine tends toward a high gloss...

Maerin said:

Personal preference dictates what to do. Mine tends toward a high gloss...

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Mine tends towards painted white…

Picture of our rails taken a few minutes ago.
5 years of full time use in a sub tropical climate

Machine sanded old flaking varnish off with 60 grit
2 coats of self priming acrylic pant rolled on.
Done

I lightly sanded my cap rail withe 220 by hand, then applied Semco natural

4fun1 said:

I lightly sanded my cap rail withe 220 by hand, then applied Semco natural View attachment 131038

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This looks pretty dang good..

4fun1 said:

I lightly sanded my cap rail withe 220 by hand, then applied Semco natural View attachment 131038

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That's what I am after! You have great looking natural rails.

Maerin said:

Personal preference dictates what to do. Mine tends toward a high gloss...

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Show off! But you earned the right

Maerin said:

Personal preference dictates what to do. Mine tends toward a high gloss...

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Those are beautiful!

What product did you use?