Joli, why white?

[Alan Wheeler]

Hi Joli, I just looked at your boat photo in the gallery. Lovely boat. But whay did you paint it white. This is a seriouse question not an OH NO you've done what?
I was wondering if I should paint mine white as well, but it's a bit of a scary decision. I am afraid it will change her lines and make her look rather plain. So what have you found.

[44'cruisingcat]

Gee. I was going to paint mine white. So it's easier to find in the dark......

[delmarrey]

I've painted my hull a Flag Blue to avoid sun bleaching and it doesn't look so dirty when sitting in a dirty marina. Oil scum at the water line.

The deck is Seattle gray for the trim and the non skid a Medium Gray to prevent the sun from blinding us on the sunny days. Plus, it doesn't look so dirty after sitting a few days without a wash down.

I don't really like white myself. It tends to get chocky or blinding and it seems most boats out there are white. it's EZer to fix scraches and dings I recon........_/)

[GordMay]

I recall standing on the deck of a steel sailboat, with light grey anti-skid & bright white trim & house.
There was a clearly noticeable* temperature difference, with the grey burning-hot, and the white only quite warm (to my bare feet).
* It generally requires a delta T of about 10 deg. F to be discernable to the touch.

[Joli]

Gord, as always, hit the nail on the head. White is much cooler than navy blue and since fading is not as pronounced as a dark color it is easier to repair. In 4 years we'll move the boat to the East Coast, Caribbean, and the Med so we wanted a color that was cooler. We have seen a dramatic temperature difference from blue to white, the blue hull would be 140-160 degree F on a sunny summer day, now that it's white it is ambient temperature. Much cooler below. I've seen white boats painted a dark color and in a very short time the hull shows print through and does not look good. If you are going to paint a llight boat dark, be aware it may have problems. Many dark hulled boats will have special lay up schedules to handle the higher hull temperature.

And as Cruisingcat said a light boat is easier to find in the dark.

Aesthetically, well that’s a personal decision. I think it looks fine white but there really is nothing as pretty as a navy hull.

[Wahoo Sails]

My previous boat, "Eva Luna" was all white when I got it. When I got around to painting the decks, I chose a light grey for the no-skid areas. Using Interlux's "light grey", I mixed it 2 parts white to 1 part light grey, hoping to achieve a sort of concrete color ... I figured that this would be light enough that there wouldn't be a noticeable increase in temperature.
I was shocked and disappointed in just how much temperature change there was! I could no longer walk on the decks barefoot in Summer, and it raised the interior temperatures by about 10 degrees. Lesson learned ... never again!
Bob

[Alan Wheeler]

Yeah I kinda wondered if you could be planning on going somwhere hot, heat can be a big problem. I have a grey'ish blue anti-skid ont eh deck. I too kept it very light thinking it wouldn't heat up much. But I can't walk on it in the summer. The dark blue hull looks great on our boat. But the sun heats the concrete up and the heat radiates into the boat well into the evenings. Nice in winter, but not so good in 30 degree C evenings. Still, I think I will keep the colour and just ensure we have good air being pushed through with fans or maybe even AC if I ever go that far with luxury.
Must say though, I thought she looked lovely in the dark colour with the lines.

[delmarrey]

Originally Posted by Joli

Aesthetically, well that’s a personal decision. I think it looks fine white but there really is nothing as pretty as a navy hull.

Sun? what's that? Up here in the PNW you have to wait for months to get any sun. Then it only lasts about 6 weeks
I don't think the inside of the boat has even been more then 100 deg., maybe when I'm not there & when it's locked up. If there is sun the boat's usually out on the water in the wind and blowing thru the hatches.

[cat man do]

Everyone seems to be a bit upset with the pale grey as it gets to hot.
I used a colour called Bay Blue on the decks which always looked clean and fresh and most importantly was very cool , to walk and sit on and inside.

Don't know if this pic will do it justice. The stuff on the left, the new cabin I was fitting has nothing on it yet.

Dave

[swagman]

We also like navy blue as we think it simply looks nicer. No one can argue a darker colour will reflect less light / heat than a white hull - but IMHO the trade off is worth it.

Peeps need to remember the historic problems with darker coloured polyester gel coat / resins fading, or shinking due to heat gain, is long gone.

Most manufacturers use epoxy gel and resins which do not shrink in the heat. So lesser chance of any cloth ever showing through today than before.

Also with more builds now using foam or alternate cores as opposed to solid glass, the insulation properties are such any temperature differences down below can be minor.

Our newer yacht is blue hull with teak / white deck and all foam cored - and due to blinds, scoops and all the stuff one can add to keep cool in hotter climates - we often have white hulled owner pals commenting on how much more comfortable down below that our yacht is to theirs!

IMHO if you have a dark hulled yacht and like the look, then there are many more (and cheaper) ways to cool off down below than to paint the hull white. Adding a full length awning is step one.

If you like white, that fine, but still pay attention to the multiple other ways to keep the boat cool or you'll still bake down below when the sun really shines.

Cheers
JOHN

[cat man do]

Originally Posted by swagman

Most manufacturers use epoxy gel and resins which do not shrink in the heat. So lesser chance of any cloth ever showing through today than before.

Also with more builds now using foam or alternate cores as opposed to solid glass, the insulation properties are such any temperature differences down below can be minor.

JOHN

John, i'll certainly agree that cored boats have better insulation characteristic's than other materials, but you'll find that epoxys have a lower threshold for heat than other resins.

This would be why fiberglass exhaust systms are not made from epoxy.

Dave

[swagman]

Goodness I hate to see a thread go off subject, but woul dlike to clarify this so no-one else is misdirected.

First, I've no idea myself what they make fibreglass enhaust systems from. I'm not even sure if they shink or not - but that was the subject of the advantages of epoxy resins - they love heat to cure - and once cured are unlikely to be effected by further heat.

Is I'm sure a lot will know, epoxy resins ARE the resins of choice in nealry all high tech composites today - boats, planes, cars etc.

Perfect examples are AIC and Volvo 60's, 70's etc.

Even F1 racecar frames.

Even Osprey and Cirrus lightwieght aircraft.

All those bits are baked in ovens to get the required cure - at very high temperatures - and no shrinkage is assured once they come out.

And in addition the epoxy resin creates a much stronger bond with the carbon (as it also would with the glass) than vinyl or poly resins ever could.

So I'm always trying to keep my mind open, but can affirm epoxy resins are unlikely to shink under further heat and definately better than vinyl or polyester resins in the sun.

And if anyone else knows what they make glass fibre exhausts systems from, I'm sure we'd all love to know what resins might be used........

Cheers
JOHN

[Alan Wheeler]

Hi John. when epoxy is heat cured, it is taken to a temp of 50C. (sorry I don't know what that would be in F) This does two things which are both closely related. Epoxy cures by the cross linking of molecular chains. The initial curing stage while the epoxy is still liquid, is relatively fast. But as the epoxy hardens, the ability of chains findng one another becomes more difficult of course. The unlocked chains become "traped" by the locked chains around them. As time goes on, many of those chains are able to lock, but there will always be some that never make it. So unlinked chains will alwasy be present in normaly cured epoxy. Now if you have done any epoxying yourself, you may have noted that if the epoxy is heated, the mix will become very much less viscouse. Infact, if you heat epoxy as it is startign to harden, you can actually turn it briefly back to a liquid. This is only becuase you are allowing the unlinked chains of molicules to move about more freely and they will not support the already linked chains, so the harden material collapses. But this is very short lived and the now heated material will harden extremely rapidly.
To take this to a usable level, you have your layup for say. You need it to cure to a point that when you apply heat, it does not melt and imediately lose it's shape. So you allow a certain time fro the layup to harden to a point where it will maintain it's shape. Then you apply heat. But the amoutn of heat you apply is critical and usaully around 50C is used. If you go too far above this temperature, the molicules that are to realeased to continue their endevours of cross linking, behave to vigourisly and the cross linking does not work correctly, resulting in poor bonds. I am not sure what actually happens in greater details, but I think certain atoms are actually ripped free from the moliceular chain.
So at temps approaching the correct 50C, the unlinked chains once again move more freely and they can come together and bond creating a much faster total cure and making the overall cure much stronger. The strength obtained with epoxy can only ever be as strong as it can with every possible link being so. Once every last link has bonded, the layup will never get any stronger, even will heat apllied in the future.
Now lets look at cured epoxy. Just like any plastic, as you heat it, it becomes softer. An epoxy boat maynot turn in to a molten blob under foot, but it does deminish in it's overall strength as heat rises. There are many different types of epoxy. each with their own characteristics. Some for chemical resistance, some for strength, some for heat. But even the ones designed specificly for heat are still not able to withstand high levels of heat without it being severly affected. I am sorry, I can not give an accurate temp off the top of my head. Perhaps someone can jump in with that. But If my brain ain't too fogged up, I believe it is no more than a 150C type range. (100C is the boiling piont of water).
The epoxies in boat use, is much much lower in the temp range of still being strong. And if it is allowed to heat too much, it can buckle if a very high load is placed on it. Typicaly the stress of rigging for instance.
Three colours are extremely bad for heat absorbtion. Black of course is the obviuose one. Dark blue is another. But one that is often overlloked is Red. Red absorbs infra-red heat like crazy. Many years back, NZ built a boat called Stienlager. She was a very very fast multi-hull. Epiglass supplied the epoxies and paints. Originaly, the boat was to be painted all red in the Stienlager colours. Butt he technicians in Epiglass said no. They calculated that int he tropics, the heat would go way beyound the safe operating levels of the product and the boat would most likely crumple due to the huge loads placed on it by the rig.
I hope that has helped.

[cat man do]

This is from Dudley Dix Yacht Design website on dark colours and epoxy resins.

http://dixdesign.com/FAQwood.htm

I want to paint my hull a dark colour. Have you any comments or recommendations on this please?

I recommend that you stay away from dark colours as long as you are working with epoxies that cure at ambient temperatures.

Epoxy resins can benefit by increasing in strength from the post-curing process that occurs under increased heat, up to a point. That point is the Heat Deflection Temperature (HDT) and varies for different resins. For resins that cure at ambient temperatures the HDT is likely to be around 70C. Temperatures in excess of the HDT will soften the resin and seriously weaken it, allowing it to stretch under whatever load is being applied at the time. That means that the structure will deform if the epoxy is working as an adhesive or is in a laminate. If the epoxy is in a coating then it will sag or run. Any paint that overcoats the epoxy will craze.

We have all experienced pain from touching dark surfaces in strong sunlight, such as walking onto a dark coloured road or roof surface with bare feet. You will very quickly burn the skin off your feet or can fry an egg on the heated surface. The temperature on the surface can be well in excess of 100 degrees Celcius.

Some boats with dark paint on their decks have wrinkled those decks from rigging loads when sailing in the tropics. The problem is not only with decks though, hulls can suffer similar problems. Glassy seas reflect the sun's rays so a hull will be attacked by the sun from above and below at the same time.

The solution is to stay away from dark colours. The darker the colour, the bigger the problem.

I built my Waterlift exhaust for thr new boat from Vinylester resin as most exhaust systems are built using it and my resin supplier's said the same.

They all thought epoxy would not stand up to the heat.

Dave.

[tdw]

Originally Posted by GordMay

I recall standing on the deck of a steel sailboat, with light grey anti-skid & bright white trim & house.
There was a clearly noticeable* temperature difference, with the grey burning-hot, and the white only quite warm (to my bare feet).
* It generally requires a delta T of about 10 deg. F to be discernable to the touch.

I can second that GM. The 'old girl' is steel, white, with grey treadmaster and in summer that stuff could melt even my first wifes heart. Great fun really, you have a choice of falling flat on your arse while trying to dodge the treadmaster or burn the soles off you feet. Pardon ? Oh well if you want to get picky, yes I could wear shoes but don't wanna !!