View Full Version : Automotive clear-coat in lieu of varnish
I'm just completing ,for a customer, a reproduction of a 1926 "Baby Buzz" or "baby-step" racing runabout.Built with West System epoxy,the interior of this little boat is an intricate grid of frames,stringers etc. and sanding between coats of varnish is just not viable,nor is brush application,and the dry time of varnish,especially during this cool,wet summer we're having is slow,to say the least.This has led me to settle on a 2-part automotive acrylic urethane as the clear-coat alternative to varnish-the stuff is made to be sprayed,doesn't need sanding between coats,contains UV filters,remains flexible,and can be recoated every 10 min. or so.I especially like the fast-dry aspect as dust is a problem in my small shop(but where isn't dust a problem?)It looks good over sanded epoxy too,of course.Only downside is cost-about $160Can/gal.-and safety(flammability and toxicity),but the labour savings in this case are huge and the end result much better,and if one is set up for spraying the safety issues are manageable.I ran this idea by tech-types at both the paint manufacturer and Gougeon Brothers and they don't foresee any problems.So,another day of prep and I'm gonna be spraying-I may never use varnish again.
I'm sure I'm not the first to use this sort of finish method but thought I might as well mention it here, especially after reading the various posts on varnishing and it's many delights.This is my first post here by the way,any comments or suggestions are welcome.
08-18-2000, 10:06 AM
Any advice from the oakum-n-pine tar gang?
John R Smith
08-18-2000, 10:22 AM
Well, it's absolutely appalling of course. Chap's trying to take some sort of shortcut, make things easier for Heaven's sake. Wasn't like this in my young day, no wonder the world is going to the dogs. Now, where's my cauldron of boiling tar? http://media4.hypernet.com/~dick/ubb/smile.gif
08-18-2000, 04:23 PM
Thos, Iīve painted many a race boat the way you just described. We used to add the appropriate plasticizer to the stuff so it was pretty soft. The only way you can properly spray the boat inside is to do it before the deck is built. It is durable. You wonīt have to varnish that boat again.
Jorma-Thanks for your reply,it's good to hear from someone who has experience with this finishing system.The manufacturer did suggest an additive to increase flexibility so your comment in that regard is well-founded.I also added,on their advice,a red/gold toner to the mix and darned if it isn't as close to varnish in appearance as,well,varnish!(sprayed the boat inside this aft.,3 coats in as many hours,gotta love it.)
JohnR-I reckon boiling tar,thinned appropriately with turps(have to watch for unwanted explosions there)may just be sprayable.Perhaps on the next project... http://media4.hypernet.com/~dick/ubb/biggrin.gif
08-22-2000, 04:21 PM
Thos, good luck with the boat. Toning the clear urethane was an interesting idea. I never new it could be done. Iīve treated a couple of masts with Spies & Heckerīs Permacron acrylic polyurethane and felt a little sorry afterwards because even if they looked neat they lacked the "traditional look".
Yes,Jorma,I was concerned about the plastic look of a perfectly clear finish but this toner has produced a color I,at least,can't distinguish from spar varnish(except for the lack of crap in the finish thanks to the dry time http://media4.hypernet.com/~dick/ubb/biggrin.gif) This stuff can be rubbed out too about 24hrs. after applying which is good as various insects took great interest in the proceedings today while I was spraying the (removeable) molded cedar foredeck.Wish I had a dedicated finishing room...
04-22-2002, 09:38 PM
OK I know this is a really old post but....I just finished the repairs on Tucana (you can see pictures on a previous post).
I now have my entire cabin house striped down to fresh wood and I need advice on what to do. How did this sprayed finish work out? Did it hold up? Did the color hold up? Is this the same basic material as the new two part finishes tested in "Practical Sailor" i.e. Honey Teak, Bristol finish, etc?
04-22-2002, 09:57 PM
I just had my runabout sprayed with a two-part automotive, so I can't testify to durability yet, but it's so far very nice looking and seems to be extremely durable. Check out the pics at:
web page (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic;f=1;t=004445)
04-22-2002, 10:36 PM
The automotive 2-part finishes are designed to be relatively soft so that they can be buffed out as needed.
You may want to look into one of the marine 2-part poly finishes that are designed to be harder, yet can be sprayed.
04-23-2002, 07:19 AM
The sign outside my shop has a few coats of this stuff and it is holding up well. It is on a southern wall, just a few degrees off the equator, and has been there for three years. I would not have called the finish soft, even without the hardener, especially compared to varnish. I added the hardener, though. Good luck.
04-23-2002, 05:52 PM
Automotive paints and clear coats are intended for very smooth surfaces. They contain lots of(up to 30%) very volatile solvents in order to be sprayable. This means that they will shrink a lot as they cure. If the surface has small furrows the paint film will be stretched and thus thinned on top of each ridge. The same thing happens on anything with sharp edges like screw heads etc. This is not science, itīs my deduction on the basis of what has happened when I have used these paints. My experience tells me not to use these paints on old, less than perfectly smooth wood. If I for some reason would use them, I would put on many more coats than on an even surface.
I have also used some 2 part polyurethane varnishes that are intended for maritime use. They have less solvents and also cure more slowly, and they can be applied with a brush because the curing is slower. The manufacturers advise to use them only on "stable" wood, which in practical terms means plywood. That is probably because they become very hard when cured, at least the ones I know of. I have wondered why they donīt sell a plasticiser that could be added. I have added a plasticiser of an automotive brand to a base of a maritime brand with good results. You have to do a trial first, of course. This kind of mix seems to work well on e.g. cockpit seats which have seams filled with a soft seam compound. But you have to make the mix very soft. And in a few years the varnish or paint will become more brittle no matter how soft it is when you apply it.
In a wooden boat there are bound to be joints. After some time the paint film will crack at the joint, allowing moisture to enter. A soft and thick film will resist for a longer period, but in the end it will happen. The cracks are usually noted when the paint is already peeling off near the joint. They have to be repaired. A 2 part poly is very resistant to abrasion and makes a neat repair work hard to achieve. While trying to smooth the paint edge, youīre easily taking away more wood than you thought, and the intended small retouch work becomes a task wchich is not worth the time spent on it.
The only place where I would use a 2 part poly now is on a glued mast or on the cockpit seat I just mentioned. On the mast because an elastic surface is resistant to shackles and things flying around, and on the seats because of the soft seams and the abrasion resistance it gives.
I did use 2 part automotive poly on my racing tunnel hulls (plywood) mainly because they were painted by pros (who knew how to do the job) in order to look nice and please the sponsors. But the boats were seldom long-lived, so the inevitable seam cracks were never repaired.
This is about all I know about 2 part poly on wooden boats. I like a good oil based varnish and and a normal oil (house) paint much better because of the much easier maintenance.
I'll be putting 2 part poly on my fiberglassed bright work in a week or so. There was a recent WB Mag article about a European runnabout company spraying poly over epoxy on their (very expensive looking) woody's. The manufacturer I buy from has two different hardeners, one for spray, one for brush or roller. I'll be rolling and tipping, same as I've done on the hull with 2 part poly paint. Looks like the wave of the future, bye bye varnish (oh oh, now I'm in trouble).
04-23-2002, 07:54 PM
"This is about all I know about 2 part poly on wooden boats. I like a good oil based varnish and and a normal oil (house) paint much better because of the much easier maintenance."
You got it dude. I wouldn't spray a wooden boat
with an automotive paint or clear coat for anything.
Especially if its going to be in a salt water envirement. It may look nice but why take a chance and do something that is unproven? I come
from a part of the country where they use a
lot of salt on the roads in the winter and the
average life of an automobile body is about
[ 04-23-2002, 09:06 PM: Message edited by: Memphis Mike ]
mmike, interesting point, but see my earlier quote from Gougeon Bros. They favour LP on epoxy, and they have their well respected professional reputation at stake. Their repair manual goes on to say "...several of the large paint companies have now developed brushable LP systems which we hav applied with rollers and brushes on several recent projects..." Perhaps like with any relatively new technology, time will tell...
04-24-2002, 05:55 AM
Sterling makes an outstanding 2 part LPU that is designed for the marine environment. WB had an article a number of years back by someone who painted their carvel hull with it and had great results.
I use the stuff on stable areas--my transom and cabin sides, which are glued teak lumber. I first coat the wood with CPES, then the LPU primer, then the topcoat. I like it mostly because it lasts so damn long. You paint and then forget about it for years.
The stuff is practically bullet-proof and will last in the sun for years and years. I would not use it in an area where there are joints and seams that will move and work. I also would not use it unless I could CPES the surface first.
The film is extremely flexible, yet incredibly abrasion resistant. It's also used on jet airplanes. It's very glossy, but you can buy a flattening paste to cut the gloss.
04-24-2002, 08:59 AM
Don't use the LPU over bare wood. Varnish first, using a product with UV protection, then spray the LPU.
05-07-2003, 12:45 PM
Am I reading this correctly that Sterling LPU does not have UV?
05-07-2003, 01:14 PM
I use it all the time, over everything, with great results and durability. It can get expensive over bare wood because so much soaks into the surface, and the high solvent load takes a while to work its way out with high shrinkage rates a result. Best to seal with epoxy or CPES first, and spray it as thick as possible, then wet sand the top coat and buff or respay a final topcoat with the designed level of reduction/reducer. You'll be happiest if you add about half the suggested amount of plasticizer one would use if spraying plastic parts or bumper covers. This will help with the issue of sharp corners and plank/joint movement.
PPG's "Omni" brand here in the U.S. is a good value for a high solids clear, about $110 for 7 quarts of usable material. (I like about 15% 860 reducer, although not called for) My autobody business has sprayed hundreds of gallons of the stuff with results comparable to brands costing twice as much- not perfectly clear like crystal, but very, very good.
[ 05-07-2003, 02:15 PM: Message edited by: Conrad S. ]
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