Does Dark paint affect foam core hulls

[Samana1982]

I have only found one article that says there is a risk that painting a hull a dark colour creates extra heat and can heat up the air in the foam expanding causing the hull to deform. I really like royal blue on the hull but if is likely to causing damage I would have to go to the default white.

[ronbo1]

It hasn’t affected a dark green Gozzard hull after 16 years.
Depends on the foam type, I guess.

[SailFastTri]

It can cause greater expansion and contraction from solar heating, which could lead to materials flexing more -- especially where you have dark and light together (e.g. stripes).

[rognvald]

Yes, it eventually causes core delamination which is why these boats are almost never seen in the Tropics and only in Northern climes. They are practically sale-proof in the South unless someone plans to repaint the hull. I kept my boat in Florida/Caribbean for 10 years and ruined(delamination) my black painted rudder when left on the hard one Summer in Florida. Also, in spite of the core, they are insufferably hot in the Tropics. Good luck and safe sailing. Rognvald

[KadeyKrogen38]

My Krogen 38 cutter with a foam core has been black since 1989 with no issues. Not much hotter down below because of foam core. Paint your boat color you love.

The boat is on Galveston Bay, in water year round and in hot sunny humid climate. Those that post negative comments are generally but passing on boat chatter.

[achil]

Dark colors will be hotter, light colors reflect the Sun better. I'm not sure if it would affect you foam core. I know that direct Sun on foam will break it down, but not from the heat.

[rognvald]

Originally Posted by KadeyKrogen38

My Krogen 38 cutter with a foam core has been black since 1989 with no issues. Not much hotter down below because of foam core. Paint your boat color you love.

The boat is on Galveston Bay, in water year round and in hot sunny humid climate. Those that post negative comments are generally but passing on boat chatter.

Hi, Kadey,
Your remarks reflect your personal opinion. It is important for readers to understand that it is contrary to accepted advice given by most boat brokers, surveyors and fiberglass repairmen in the Southern US and the Tropics. My friend in Naples just traded-in his 9-month-old 40-foot Searay with a black hull and took a huge beating on the value because of the color. The broker subsequently sent the boat to Tennessee since it would be too hard to sell in Florida. Besides potential delamination issues, dark-colored hulls oxidize very quickly in the sun-- even with the best wax regimen. However, on the upside, they are very beautiful boats when well-maintained and is, perhaps, why they are popular in the NE US(Hinckley, Morris, Cape Dory, etc.). Good luck and safe sailing. Rognvald

[Blue Stocking]

Originally Posted by rognvald

Yes, it eventually causes core delamination which is why these boats are almost never seen in the Tropics and only in Northern climes. They are practically sale-proof in the South unless someone plans to repaint the hull. I kept my boat in Florida/Caribbean for 10 years and ruined(delamination) my black painted rudder when left on the hard one Summer in Florida. Also, in spite of the core, they are insufferably hot in the Tropics. Good luck and safe sailing. Rognvald

Definitely does, with personal experience. In the 70s, very much involved in building 65 - 70 ft day cruisers in Bermuda. 6 lb/cu ft Airex cabin tops went soft under medium blue paint, and had retro-fitted supports.

[DerekKelsall]

Originally Posted by Blue Stocking

Definitely does, with personal experience. In the 70s, very much involved in building 65 - 70 ft day cruisers in Bermuda. 6 lb/cu ft Airex cabin tops went soft under medium blue paint, and had retro-fitted supports.

All depends on the foam. Airex is the most heat sensitive and is not recommended for decks of any color.

Where a dark color is planned during build, consult the foam supplier. Foaming is a curing process and some foams can have patches which are not fully cured. We have had Cross linked PVC post cured, just to be sure. "Outgassing" can cause a bubble between the outside skin and the foam. During the time I have been involved with foam boats since 1965 I have seen just two incidents of palm sized bubbles on maroon boats. One, GB 11, after sailing around the World. It would be misleading to call this delamination. The bubbles are not big enough to affect the strength. Deforming could also happen if left for some time under stress in hot sun. The foam density and thickness also comes into the equation. our results with foam have been exceptional. However, there are a number of incidents where the wrong foam choice has given foam a bad name. During the last few months I have been in touch with 7 owners of Kelsall boats which are 40+, the oldest being Trifle at 51, the second tri I designed and built. All are structurally sound.
Happy boating, Derek.

[Samana1982]

Originally Posted by DerekKelsall

All depends on the foam. Airex is the most heat sensitive and is not recommended for decks of any color.

Where a dark color is planned during build, consult the foam supplier. Foaming is a curing process and some foams can have patches which are not fully cured. We have had Cross linked PVC post cured, just to be sure. "Outgassing" can cause a bubble between the outside skin and the foam. During the time I have been involved with foam boats since 1965 I have seen just two incidents of palm sized bubbles on maroon boats. One, GB 11, after sailing around the World. It would be misleading to call this delamination. The bubbles are not big enough to affect the strength. Deforming could also happen if left for some time under stress in hot sun. The foam density and thickness also comes into the equation. our results with foam have been exceptional. However, there are a number of incidents where the wrong foam choice has given foam a bad name. During the last few months I have been in touch with 7 owners of Kelsall boats which are 40+, the oldest being Trifle at 51, the second tri I designed and built. All are structurally sound.
Happy boating, Derek.

Thanks Derek. Our boat was built in 1982 so very hard to find out the type of foam they used. It has spent most of its live in Australia at lower latitudes and has always been an off white. I concerned that changing colour and plans of sailing in tropics could create problems.

[Samana1982]

Originally Posted by rognvald

Hi, Kadey,

Your remarks reflect your personal opinion. It is important for readers to understand that it is contrary to accepted advice given by most boat brokers, surveyors and fiberglass repairmen in the Southern US and the Tropics. My friend in Naples just traded-in his 9-month-old 40-foot Searay with a black hull and took a huge beating on the value because of the color. The broker subsequently sent the boat to Tennessee since it would be too hard to sell in Florida. Besides potential delamination issues, dark-colored hulls oxidize very quickly in the sun-- even with the best wax regimen. However, on the upside, they are very beautiful boats when well-maintained and is, perhaps, why they are popular in the NE US(Hinckley, Morris, Cape Dory, etc.). Good luck and safe sailing. Rognvald

I previously had a black boat that was hard to sell but that was more about the colour, I had to paint it white to sell it. Thanks for your input

[boatpoker]

I've only see two boats where the foam had gone soft under dark colours, both were Airex.

I don't see how an inch or two of foam core can make the boat hotter inside as this is what's called "insulation".

Having owned foam (not Airex) cored and solid glass boats I much prefer the insulation value that helps our furnace when we winter in Toronto and the insulation value that helps our a/c when south.

[Orion Jim]

Originally Posted by rognvald

Hi, Kadey,
Your remarks reflect your personal opinion. It is important for readers to understand that it is contrary to accepted advice given by most boat brokers, surveyors and fiberglass repairmen in the Southern US and the Tropics. My friend in Naples just traded-in his 9-month-old 40-foot Searay with a black hull and took a huge beating on the value because of the color. The broker subsequently sent the boat to Tennessee since it would be too hard to sell in Florida. Besides potential delamination issues, dark-colored hulls oxidize very quickly in the sun-- even with the best wax regimen. However, on the upside, they are very beautiful boats when well-maintained and is, perhaps, why they are popular in the NE US(Hinckley, Morris, Cape Dory, etc.). Good luck and safe sailing. Rognvald

Just to clarify, Cape Dory hulls are solid laminate, the cabin tops and side decks are balsa cored. White hulls are the norm, some have subsequently been painted or gel coated in other colors.

[Samana1982]

Originally Posted by KadeyKrogen38

My Krogen 38 cutter with a foam core has been black since 1989 with no issues. Not much hotter down below because of foam core. Paint your boat color you love.

The boat is on Galveston Bay, in water year round and in hot sunny humid climate. Those that post negative comments are generally but passing on boat chatter.

Good to know, personal experience always carry more weight when making these decisions. It seems it will be about the type of foam which was used, because the boat was built in 1982 will be difficult to find out.

[Redpcx]

I can't comment on delamination of core, as the hull of my boat is solid layup. BUT! Dark blue painted hull can cause print-through.
The pattern of the woven roving can be seen, but only as you run the buffer.
Apparently, the glass and resin have slightly different expansion, which can affect the paint. Dark color gets hotter, more differential expansion. Or maybe just more visible. Boat was painted around 1995, and the clearcoat over the Awlgrip is bad.