Hypothetical question: Double 6oz. top, Single 6oz. bottom.
Which is of the two would provide more structural strength (if any)?
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sanded gloss coat?
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polished gloss coat?
Gloss coat is known to be stronger.(It makes sense, more resin) However, no gloss coat would ever prevent snappage.
When you put paint on a wall… does it make the wall stronger? Resin has no strength. -Carl
resin without glass is not at all strong, and is in fact very prone to fracture. a gloss coat, being another layer of unreinforced resin, won’t make the board stronger…it will, however, make it much prettier…and every time you bang it into something, you’ll get those little spider cracks…gloss resin is WEAK.
A final gloss coat done corectly will add some strength to the skin.Machine polishing a gloss coat actually weakens it somewhat.That dull wax you see that rises to the surface on a gloss coat is one more layer of protection.Another way to get a strong light board is to just sand the rails of a hotcoated board and leave the deck and bottom alone. RB
Cleanlines has worded my intention better:- Gloss coat is a more durable skin… Anyway, you’ve all got valid points to make. I just think of the sanded- off tops of glass weave being re-sealed with that fine coat of resin. Some makers insist on gloss and wetrub even on superlight comp boards. We merely profinish the rails only, the place where the cloth is most likely to be exposed. Some believe unsealed weave absorbs water.
The single biggest factor in maximising strength of you glass, whatever weight, is avoiding oversanding !!!
Josh D
so i’ll get a stronger board (more resistant to those little spider cracks and whatnot) if i hand polish??
Howzit Mr. Clean, Boy That would sure make things a lot easier if people didn’t want that nice shiny finish. When you consider how much some people are charging for a gloss and polish( $ 55.00 - $75.00 ) I would think they would forget the rubout and polish part. Aloha,Kokua
oooh polished boards are beautifal though!
Regarding “Spider Cracks” in the gloss coat.Usually these cracks show up around the edges of knee dents and things like that.It has pretty much been determined that the cracks only go through the gloss and not into the lam job so they are not that big of a problem.More of a cosmetic thing versus actual structural breakdown.A gloss coat is just the final seal of a lam job and it gives more durability (probably not a whole lot…a valid point to argue).One of the best “gloss” coats I have seen is when a board is finished in clear automotive urethanes such as “Chromaclear” made by DuPont.You spray around three coats to get the thickness and machine polish it like you would polyester.The good thing is it stays flexible.weighs very little, and won’t crack…the bad thing is is costs around $145.00 for a 1 gallon kit.I figure that if you used a good HVLP spray sytem you could do around 4-6 longboards.These are the finishes used on cars and yachts.We surfboard types tend to be on the cheap when it comes to technology. (Hint…I had a board sprayed with urethane at a friend’s shop that paints vehicles.He did the board while clearcoating a car.We hung it from the ceiling using an old fin in the box with rope tied to it.That enabled him to shoot the whole board top and bottom without moving it.Charged me $20 plus a 6 of Bud Light.) RB
I sanded my last board then sprayed it with U Pol urethane clear coat I bought from an automotive paint store ( not an auto parts store). U Pol is the same stuff the manufacturer uses to clear coat your car finish. It comes in a spray can so application is easy (costs about 15.00 ), it contains UV protectant - so colors including white are stable, is as waterproof as anything, and a couple of layers weigh next to nothing. It won’t add strength but it is a great sealer and easy to apply.
Gloss will seal off any pinhole, sandthroughs, etc and reduce the chance of the board taking in water. Not sure that that will ever make a case for a glossed board being stronger.
A longboard without a gloss, somehow just deosn’t feel like a longboard. And a shortboard with a gloss somehow doesn’t feel like a shortboard.
Drew
Alex…the stuff I am talking about has to have hardener added.Is what you used comparable?I have never seen a 2 part mix in a spray can. RB
Guys
Check the Cooperfish thread over at longboard.net with a couple of interesting points about sanded vs polished finishes - worth a read.
John
Cleanlines - Comparable yes. The same no. Your 2 part product is catalyzed. I have heard of canned products with a membrane you pierce for mixing but have never seen one. A catylized paint will always be a superior product when it comes to durability. The can I use ( U Pol or Du Pont 1K ) is a one part product but beyond that the chemistry is similar. It even smells the same. You may achieve excellent results right from the can. If you get any orange peel you can sand w/ 1500 then polish to an automotive shine. The durability ( and flexibility) required for auto finishes - resistance to wind driven abrasives,sunshine, chemicals from road treatment, bird poop and smashed bugs - makes them appropriate for use on surfboards.
Wear your mask. The fumes are as strong as resin.
All of these modern auto finishes are toxic as hell.I think most of them are called Linear Urethanes or something like that.The car painter that sprayed my board was wearing the equivalent to a space suit suit…air supplied by a hose.I think one of the best clear board sprays I have ever used was one that Greg Loehr developed for Resin Research.It was water based and sort of milky in color.You had to shake it real good before spraying but it gave a nice flat finish that was tough as nails.I liked it a lot better than the other solvent acrylic speed sprays normally used in factories.It dried a bit slower but much more durable and non toxic.If Greg is out there maybe he can give us a heads up on it. RB
Here’s a link to the product that he is talking about http://www.levineautoparts.com/upclear1uvre.html I think that I’m going to give it a shot. How many cans would it take to finish an 8’ board (1 or 2?)
Our speed spray product is a water based styrenated acrylic sealer. We sell it in FL and would sell it in the West if anyone wanted it. Right now we don’t stock it out here.
As for which is stronger, strength to weight is what it’s all about and the sanded board is stronger per weight. If you look at the weight of a gloss it’s about the same as 2 oz. of glass per side. So which is stronger, 1. a 4 bottom and double 4 deck with a gloss or 2. a 6 bottom, 4 and 6 deck without? For strength I’d vote for #2
Yo Greg…when I was down at Specrum playing in the factory they agreed you had a better spray.However they used the solvent based stuff because it dried as fast as lacquer.Maybe that’s why the pros don’t use it…they don’t want to spend five more minutes on a quality finish. RB
My take on this discussion is that most boards are oversanded on the hotcoat and are weaker due to the inconsistency of the “skin” thickness. Cracks occur in the uneven areas when the board is stressed. So, a very lightly sanded glosscoat evens things out and makes a stronger skin. That said, I’ve repaired many well glassed boards that have taken severe impacts and the glass was just slightly cracked on the gloss/hotcoat. However, when I sanded these cracks out and the glass became thinner, you could poke right thru it because the foam was dented back from the impact. So it really didn’t matter how strong the glass was, the damage still had to be ground down to the foam just like a crappy glassed board. Glassing strength has a lot of meanings; overall tension/compression strength of the deck and bottom, torsional strength, etc. Glassing specifically for these factors using polyester is 95% dependent on the cloth and it’s bond to the foam. There’s no such thing as impact strength with poly, and that’s why there’s no glassing which will resist heel dents on the deck.
Acrylic topcoats are a good alternative to a traditional gloss. On shorter funboards I’ve been using two coats of “Ultra Clear” from Valspar in rattle cans. This stuff will polish out like a good gloss (using 320 finish under it) with no tape lines or sanding. Cures faster than gloss also. It’s been on a couple of boards for 18 months now without any signs of wearing off yet.