Re-Coating Tiller - What to Apply ?

[dennisail]

I have sanded the old clear coat off a tiller. The coating was chipped in some areas and the coating was pealing off around the chips as water intruded. So whatever it was, it didn't stick real well. Also the wood was a little water damaged in those areas but I think I have the prep work nailed. I finished with 150 grit on a electric sander.

What type of clear-coat should I apply for a nice hard waring finish? Any tips on the amount of coats and prep between coats will be handy too.

This is not the tiller but it is of this style with the multiple layers and curve. What do you call this construction method?



Thanks guys.

[matauwhi]

G'day, mate. If you are going to keep it covered when not in use, you can just use a polyurethane from the hardware store. If you want some good UV protection, get a marine varnish. Everybody will have their favorite. We have been keen to Interlux's Schooner. The first coat you can cut it 50% with turps, then use approximately 10% with the following coats to get it to flow well. We normally stop around 15 coats after stripping back to bear wood. Switch to 220 grit and sand lightly, especially on the edges (you can also use a green scrubbing pad). Good foam brushes work well. Give them a rinse in turps and put in the freezer between coats and use should be able to get the job done on one brush. Hope that helps. Cheers.

[PAR]

150 grit, especially if used with a palm sander or DA will leave swirl marks in the wood, under any clear top coat. Clear finishes require the most amount of prep and routine care after.

Continue sanding, by hand, with the wood grain, through progressively finer grits, up to 220 (at least or to 320 max). This will remove the swirl marks and smooth out the tiller.

Once satisfied with the sanding, you need to select a finish type and there are three choices; oil, varnish or polyurethane.

Oil is easy and quick, but it's messy, doesn't really shine, doesn't last very long and doesn't offer much protection. Even worse is if you use linseed oil, it'll darken the tiller to a grayish black in several years. Use tung oil if you must use oil.


Next on the list is varnish, which comes in several grades. The goods stuff (also happens to cost like it's the good stuff) works well, is quite shinny, moderately hard, offers good UV protection and a pretty amber hue. It's easily repaired if you "catch it" in time and it's the traditional way to go.

Modern chemistry has taken varnish to the next level, with polyurethanes. These are much harder, typically have higher gloss retention, better UV protection, better abrasion protection and longer life. They also can be applied much faster the varnish, some brands permit 4 or 5 coats per day, which is imposable with varnish. On the other side of the coin, they also are difficult to repair if damaged and can be difficult to apply if using a linear system.

In the end it doesn't matter what finish type you select if you don't protect the finish once it's dry. A cover is the simple way to handle this.

For honest clear topcoat protection, you should break the application coats into two distinct methods; bulking up and finishing. By this I mean all clear coats need to have a fair bit of film thickness as a base, over which the finish coats are applied. Clear coats protect the wood with UV inhibitors, which require film thickness to work. If you apply 3 coats and call it done, you'll be repairing damaged wood the following year, because the UV will literally burn through the clear coats and singe the wood below.

A good varnish or polyurethane job will have a base of 5 - 6 coats with 3 - 4 top coats as the finish. This way the top coats serve as the sacrificial layers, which get sanded off during touch ups and repairs, while new top coats are applied over the still intact base coats. A show winning mahogany runabout might have 15 base coats and several finish top coats. This is more anal then most are willing to do, but consider the base coats as the protection and the last few top coats the sacrificial layers that UV or sand paper will break down in time.

[dennisail]

Thanks the detailed replies guys. I don't want to go with oil. I think a good polyurethane is sounding the best at the moment. I don't want to have to apply 20 coats of varnish that take a day to dry each. I want to go out sailing. What about epoxy? I have some laminating resin. This seems to leave a thick and durable finish? I guess there would be some reason its not a good idea?

[matauwhi]

G'day, mate. Some people will use two part exposies as well. There are two part varnishes on the market also. The single part systems are a little easier to repair if you get a chip. Ya, go sailing, get a couple of coats down of what ever you choose and if you want a mirror like finish later, you can always add more coats in the off season. Cheers.

[PAR]

Epoxy will need to be top coated for UV protection. New formulations of epoxy offer some, quite limited UV inhibitors with the epoxy, but they still need to be top coated. I see no advantage to epoxy coating your tiller, unless it double duties as a hammer too.

Single part polyurethanes work well, though not as hard, nor as durable as the two part varieties. A minimum of several coats, which can be applied in a couple of days. Some brands also permit chemical bonds (no sanding between coats) which can be a great advantage.

[Eleven]

My wood minded marina mates have all settled on the varnish method of a third/ a third/ a third. One third thinners (for penetration into the base timber)/ one third wood preservative (to actually protect the timber)/ one third marine varnish.
Add as many cosmetic marine varnish finish coats over this as you like over. You've protected the timber already, sealed it, preserved it. Gloss is for you, that treatment is for the wood. Varnish only will last half a year, ten percent varnish in thinners, then an overcoat of neat varnish might do two years. Wood is actually the hardest material to keep nice in terms of effort and cost. But so worth it.

[BlueSeas]

Answer to the other question for the OP I believe is it is a laminated tiller made with multiple strips of two different types of wood which give the layered appearance. They are bonded together to create one piece of wood instead of using a single solid board of wood and shaping it.

[daddle]

A big negative of epoxies is that when they start to go bad they really go ugly, and are quite a chore to sand away.

[dennisail]

Thanks guys. Can I get the good polyurethane from the hardware store or do I have to go to a boat store?

[PAR]

I've never seen a "good" clear coat product at the hardware store. They sell home owner stuff like the MinWax junk.

Try Bristol Finish. It works well and is a two part product. Epifanes Polyurethane is also well regarded. Epifanes Rapid Coat is a single part product that will offer great performance and recoat times.

Several on line sellers can help you, like Jamestown, Noah's etc.

[dennisail]

I confess to buying from the hardware store. I was going to go to the boat store but I found a wattyl marine grade exterior varnish at bunnings.

I'm onto my 4th coat. I am still using the thinned varnish (30%) just to use up what I mixed for the initial wood penetration coats. Are there any downsides to using the thinned varnish other than coat thickness? It seems to smooth out brush strokes well and dries faster. It looks like I will have to put on like 5 more coats to use it up. I wonder if I should switch straight to the non thinned varnish? I have been bagging the brush and putting it into the freezer and not washing it between coats. I will throughly clean it before the last coat though to make sure I don't get any specks from semi dried varnish on it from the brush.

I sanded after my 3rd coat with 280grit, but this seemed a bit too harsh. However the small scratches seem to disappear totally upon the next coat of varnish. Its looking good so far

[David M]

Exterior boat varnish is all pretty much the same. What will make the most difference is having a cover for it.

[dennisail]

Its got a cover

[PAR]

You're just wasting time with the thinned varnish now, move on to full strength. You may want to add a little Penatrol (5% or less by volume) to help the varnish flow. The same is true with thinner (5% or less by volume), other wise it affects the gloss. Lightly sand with 280 (with the grain only) which will disappear with the next coat. Sand only by hand at this stage.

There's a fair bit of difference between different varnish brands. The first thing I look for is inhibitor content percentage, type of alkyd, drier content, etc. There can be huge differences between some brands. For example Dennisial is using a polyurethane, not an traditional alkyd. Unless you're working in a harsh temperature (too cold or hot), you should be able to use this stuff straight from the can. Don't use a brushing agent (Penatrol or similar) with this stuff and be very sparing with the thinner.