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View Full Version : Glued lap-dark paint, any worries?



Falcon1
07-20-2017, 01:50 PM
I want to paint the topsides of my glued-lapstrake Ilur a very dark green. Pretty much black. She will have copper-riveted frames, but do I have to worry that the dark paint will cause the epoxied laps to come apart?

I live in RI, New England. We get runs of 90 degree days in summer.

Hoping I can stick with my color scheme.

Mike

jackster
07-20-2017, 07:04 PM
Mike, IMHO...Motorcycles are BLACK and... Boats are WHITE... Thus keeping the World in balance! :)
But if you INSIST in throwing us all for a loop, the heat of a dark hull will not affect the epoxy.

JimConlin
07-20-2017, 10:30 PM
I would not worry about it, but I would not use an off-brand epoxy.

MN Dave
07-20-2017, 11:37 PM
Those surfaces can easily hit 180F in the sun. The laps will probably not come apart, but they will be weaker until they cool off. In my opinion, a dark color is not the best idea. My old redwood stripper guideboat is dark blue, so do as I say,not as I do. It survived Florida when it was dark green. So I like the dark colors, but I'm sure it would have been better for the epoxy if it was lighter. The strength reduction is not a sudden drop like hitting a melting point, It starts at or near the glass transition temperature (tg) and is fairly gradual. Most epoxies that we use have a tg around 125-130F.

There are low solar absorption paints (LSA) that can get the temperatures down by 40 degrees or so. (that was for green 383) They were developed for the military, NASA and the vinyl siding industries.

You might be able to add glass bubbles to the green paint http://solutions.3m.com.tr/3MContentRetrievalAPI/BlobServlet?lmd=1370888546000&locale=en_WW&assetType=MMM_Image&assetId=1361623393356&blobAttribute=ImageFile

NASA: https://spinoff.nasa.gov/Spinoff2007/ch_4.html

If you can stand the hype: http://hytechsales.com/insulating_paint_additives.html The 3M link above said that the glass worked better than ceramic. Ceramic hollow spheres are cenospheres. They come from coal fly ash.

The vinyl siding colors seem mostly grayish
https://www.benjaminmoore.com/en-us/color-overview/find-your-color/color-collections/vinyl/revive-colors-for-vinyl-siding
https://www.sherwin-williams.com/homeowners/color/find-and-explore-colors/paint-colors-by-collection/vinylsafe-colors-for-vinyl-siding

Navy
http://protective.sherwin-williams.com/knowledge/news-and-events/2011/sherwin_williams_polysiloxane_coating_is_new_big_g un/
http://www.international-marine.com/Literature/Interlac%201%20PIC.pdf

jackster
07-21-2017, 05:06 AM
What Gougeon Brothers/ West system says...
http://epoxy-it.com/ss/if-you-can-t-take-the-heat/

Ian McColgin
07-21-2017, 05:36 AM
Green is an oddly cooler color than other darks. On my old schooner Goblin I mixed the darkest green Kirby's then produced with three parts of their flat black and got a "greenish off-black" that did not heat the hull anything like the previous year's flat black. In the three decades since then, Kirby has come out with a super dark green that I happily am using on Meg. It's a shade or so darker than British racing Green.

I had a friend who cooked up an exhibit for a children's museum. I made a bench and she looted the off-cuts pile from a friend who does Corian to make a mosaic seat - each color being at least 38 square inches (a quarter square foot). Folk were always surprised at how similar the dark green felt under the sun to light green and to yellow.

So, I'd not worry if your paint is as good as Kirby's, though I am told that not all green pigments quite manage the IR/UV reflectivity of traditional green.

Falcon1
07-21-2017, 05:48 AM
I'm using WEST epoxy, and thinking of Kirby's bronze green, with a lighter sheerstrake. Thanks for the replies, esp. the link to the Gougeon site. I'll forge ahead. Thinking of something not too different from this:

https://farm5.staticflickr.com/4293/35673023980_39410cf291.jpg (https://flic.kr/p/WmizcA)ilur2 (https://flic.kr/p/WmizcA) by Michael Owen (https://www.flickr.com/photos/107084128@N08/), on Flickr

and my current state of affairs:

https://farm5.staticflickr.com/4208/35806127035_c57cf32408_b.jpg (https://flic.kr/p/Wy4L6R)IMG_1018 (https://flic.kr/p/Wy4L6R) by Michael Owen (https://www.flickr.com/photos/107084128@N08/), on Flickr

Thanks again, all.

Mike

Canoeyawl
07-21-2017, 11:16 AM
I wouldn't do it...

"Black is the ultimate heat absorber. It absorbs all light on the visual spectrum, creating a void of light. As a result of absorbing all light wavelengths, black is the hottest possible color. White is the opposite. White light is the sum of all wavelengths, so when some people view a white object, they are really viewing all visible light hitting the object's surface and reflecting back. Some heat is still absorbed based on the nature of the object's material, but minimal additional heat is absorbed, making white the coolest possible color". http://sciencing.com/colors-absorb-heat-8456008.html

Jay Greer
07-21-2017, 12:12 PM
Well NG Herreshoff is known to have said, "There are only two colors for a boat, black and white. Only a damn fool would paint a boat black." So, we painted our H28 white with a blue boot stripe. Maynard Bray likes that combination too. |:)
Jay
https://uniim1.shutterfly.com/ng/services/mediarender/THISLIFE/001079903521/media/23012422727/medium/1413651839/enhance

Andrew2
07-21-2017, 12:43 PM
Any flat dark colour is inviting problems. May not be to big a thing for narrow 'planks' on glued lap, but I would go lighter. 'Cors, they are at shallow angle to the sun, if at all, not like the deck.
A2

My Whilley Tern has survived ten years of epoxy coated hull with without recoating, just looks a bit dull, while the interior and rails, which catches much more U-V, have been coated several times. It does live under cover when out of the water and gets far less use than I would wish....

MN Dave
07-21-2017, 02:32 PM
Ian's dark green paint had an interesting pigment mix. It was apparently not so dark in the IR end of the spectrum. Some dark greens are not as cool as that Kirby's paint.


I wouldn't do it...

"Black is the ultimate heat absorber. It absorbs all light on the visual spectrum, creating a void of light. As a result of absorbing all light wavelengths, black is the hottest possible color. White is the opposite. White light is the sum of all wavelengths, so when some people view a white object, they are really viewing all visible light hitting the object's surface and reflecting back. Some heat is still absorbed based on the nature of the object's material, but minimal additional heat is absorbed, making white the coolest possible color". http://sciencing.com/colors-absorb-heat-8456008.html
That all depends on how well the paint absorbs and radiates infra red light. I have seen a silver paint that was noticeably hotter than a soot covered area of the same sheet of metal. (painful vs uncomfortable, whatever temperature that is) The soot was such a good IR radiator that it was able to dissipate so much more heat than the silvery surface that it was not as hot.

http://www.ips-innovations.com/exterior_coatings_2008.htm

http://www.ips-innovations.com/bilder/exterior_coatings_2008/reflectance.gif

A cure for insomnia: http://m120.emship.eu/Documents/MasterThesis/2014/VIVEK%20KUMAR.pdf

Canoeyawl
07-21-2017, 03:01 PM
But...
I wouldn't cover my boat with soot! Just sayin' ;)

Reynard38
07-21-2017, 04:14 PM
My Coquina was Kirby's bottle green. Glued lap. 3 years (we don't do "seasons" here) in the GA sun. No issues.
Use a good epoxy, paint her a color that makes you happy. Capt. Nat is long dead. He won't care.

Falcon1
07-21-2017, 04:29 PM
I also really like this combo. From Vivier's website, I think. I can't believe how many color schemes I fall in love with, but that's another thread.
Thanks, all.

https://farm5.staticflickr.com/4296/35263505083_f1f1bc56b9.jpg (https://flic.kr/p/VJ7FuX)DSC07432 (https://flic.kr/p/VJ7FuX) by Michael Owen (https://www.flickr.com/photos/107084128@N08/), on Flickr

Yeadon
07-21-2017, 05:15 PM
Paint color doesn't really matter for glued lap. Whatever makes you happy, do that. Do try to avoid any light colors on the interior that will blind you with glare on sunny days.