Painting an aluminium MH a dark colour

Pierre leGrim

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Hi peoples

I’m thinking of painting my currently white MH a dark colour(s). Its an aluminium-skinned 1990s vintage Elddis.

My concern is how much additional thermal expansion in the outer skin can I expect to see? Would it lead to warping of the panels or popping seams and causing leaks?

Anybody got experience of painting this type of MH and what the outcome was?

Many thanks
 
Good question;

Here is a calculator for thermal expansion you can use for Al but I've got to go out but I'm sure colour thermal absorption info must be out there on the web so you can probably reach an educated conclusion.

Thermal Expansion Calculator | Good Calculators

This thermal expansion calculator can be used for the calculation of the linear thermal expansion of any material for a specific initial length and variation in temperature
goodcalculators.com goodcalculators.com
 
Also looks like shiny or matt makes a big difference, which were you thinking?

If I've used that calculator correctly a 1m length of Ally at 100c only gains 2mm (doesn't state thickness though, maybe doesn't matter)

In this link the black paintwork got to 76c/168f

meguiarsonline.com

Working in the sun? How HOT does your car's paint get? - Car Care Forums: Meguiar's Online

meguiarsonline.com

So looks like the expansion forces could be quite minimal.

PLEASE do NOT trust my maths or sources!!!!!
 
Last edited:
Tookey said:
Good question;

Here is a calculator for thermal expansion you can use for Al but I've got to go out but I'm sure colour thermal absorption info must be out there on the web so you can probably reach an educated conclusion.

Thermal Expansion Calculator | Good Calculators

This thermal expansion calculator can be used for the calculation of the linear thermal expansion of any material for a specific initial length and variation in temperature
goodcalculators.com goodcalculators.com
Click to expand...
Thanks for that Tookey.
Ok. A 4.5 metre length of ally sheeting would expand 4.5mm over a temperature rise from 25C to 45C, according to the calculator.
I'd have to hope that as long as all the panels are the same colour including the roof, they should all expand at the same rate and not dislodge any seals.
Though there again, only half the van is in direct sun at any one time.
I'd be interested to know of any experience or advice.
Thanks again
 
I would also ask the same question on a metal workers forum (FB maybe?) considering how important it is not to balls it up!
 
Pierre leGrim said:
Thanks for that Tookey.
Ok. A 4.5 metre length of ally sheeting would expand 4.5mm over a temperature rise from 25C to 45C, according to the calculator.
I'd have to hope that as long as all the panels are the same colour including the roof, they should all expand at the same rate and not dislodge any seals.
Though there again, only half the van is in direct sun at any one time.
I'd be interested to know of any experience or advice.
Thanks again
Click to expand...
In the paintwork link the black paint got to 76c (might be Texas!) so nearly a 7mm expansion on your 4.5m which sounds alot but if expansion was equal on all four edges then you are looking at less than 2mm per edge i.e not a lot :unsure:

I can't help anymore but hope someone with some experience turns up
 
Airplane wings are ally and experience huge temp changes which might be a comforting thought (y)

Dubai airport at 40c to -40c and lower when cruising
 
Tookey said:
Airplane wings are ally and experience huge temp changes which might be a comforting thought (y)

Dubai airport at 40c to -40c and lower when cruising
Click to expand...
The Lockheed Blackbird leaked like a sieve until it go hot enough to expand the joints tight.
 
That's a good point, my -40c does account for friction warming of the ally. For the sake of the OP let's not start discussing that :LOL:
 
It seems a tricky subject because of the age of the panels and their old seals and fixings. Painted dark, the calculator showed they'd certainly expand/move a lot more than they do now and I think I'm talking myself out of the idea.
Many thanks for the thoughts on this - and the digression into aviation, lol.
 
I’ve had little movement with painting the last TWO Ali skinned Motorhomes from White to Black & Silver Grey, Only a millimetre or so of movement, I Painted on a mid range temperature day, knowing I’m going to be uk tied.
I put another coat on two years later & it was all good 👍
 
Nesting Zombie said:
I’ve had little movement with painting the last TWO Ali skinned Motorhomes from White to Black & Silver Grey, Only a millimetre or so of movement, I Painted on a mid range temperature day, knowing I’m going to be uk tied.
I put another coat on two years later & it was all good 👍
Click to expand...
Thanks Zombie. That's helpful.
What sort of paint did you use?
 
Actually
I did do a thread on here about 3 years ago when I done it 🤔
On ‘The Nest’I used a Poluathane Concrete floor paint, & Rollerd it on with a 4inch Roller in March I think it was (Beast from the East kinda time),
I then put the final coat on about August ish later that same year & all was ok for me...
On Boxey I’ve used a Water based Paint, & started it around July last year, Will put the last coat on it maybe September this year.
Again all is fine for me.
I always wipe everything down several times with White spirit first of all, Then I put a really thin wash coat on, Then a Second Wash coat, Then a 1st Top Coat, Then about a year later a 2nd Top coat. (obviously Sanding & Washing Down with White spirit between each coat.).
It’s not a showroom Finnish, I Liveaboard, Work from & Use my Vehicles so they do get scratched but easy to touch up !.
 
Nesting Zombie said:
Actually
I did do a thread on here about 3 years ago when I done it 🤔
On ‘The Nest’I used a Poluathane Concrete floor paint, & Rollerd it on with a 4inch Roller in March I think it was (Beast from the East kinda time),
I then put the final coat on about August ish later that same year & all was ok for me...
On Boxey I’ve used a Water based Paint, & started it around July last year, Will put the last coat on it maybe September this year.
Again all is fine for me.
I always wipe everything down several times with White spirit first of all, Then I put a really thin wash coat on, Then a Second Wash coat, Then a 1st Top Coat, Then about a year later a 2nd Top coat. (obviously Sanding & Washing Down with White spirit between each coat.).
It’s not a showroom Finnish, I Liveaboard, Work from & Use my Vehicles so they do get scratched but easy to touch up !.
Click to expand...
Nice one mate. Thanks for your advice - very much appreciated.
 
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