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  1. #1
    Join Date
    Nov 2016
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    2,281

    Default Just slap on some paint

    Ploughing through a post in Practical Sailor mag - "Black dust is like an insulator around your alternator. Paint can have the same effect: Donít paint an unpainted alternator; it wasnít meant to look pretty." - I'm thinking of my Beta/Iskra alternator now sitting, bright red, on one side while I attempt to connect up some sense wires.

    Does the team think it would be a good idea to remove the red paint, and what with?

  2. #2
    Join Date
    May 2007
    Posts
    36,231

    Default Re: Just slap on some paint

    Red paint will radiate more heat than a shiny silver alternator.
    Bare metal will develop an insulating white furry oxide.
    As Mr Jagger said, Paint it Black.

    I think most of the cooling is due to an internal fan on most alternators.

  3. #3
    Join Date
    Dec 2010
    Location
    South Oxfordshire, Gosport and Wellington New Zealand.
    Posts
    7,775

    Default Re: Just slap on some paint

    No.

    Our boat is fitted as OE with a Balmar 110 AMP Alternator and smart charger, as was the previous boat.

    Balmar high output marine alternators are finished in shiny white paint.

    If its good enough for them............................

  4. #4
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    6,837

    Default Re: Just slap on some paint

    Quote Originally Posted by lw395 View Post
    Red paint will radiate more heat than a shiny silver alternator.
    Bare metal will develop an insulating white furry oxide.
    As Mr Jagger said, Paint it Black.

    I think most of the cooling is due to an internal fan on most alternators.
    Are you sure about that. I know black will absorb more radiant heat than any other colour better is matt black but I cannot remember the effect or the loss of heat by radiation by surface.

    As most heat will be dispersed by convection for are correct that the fan will have the main cooling effect and I wander what any insulation effect any paint will have in reducing the conduction effect from the metal heat sink to the air flow around the alternator.
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

  5. #5
    Join Date
    May 2001
    Location
    UK East Coast
    Posts
    35,507

    Default Re: Just slap on some paint

    Quote Originally Posted by zoidberg View Post

    Does the team think it would be a good idea to remove the red paint, and what with?
    Don't believe everything you read in sailing magazines! Leave it alone, you must have better things to do!

  6. #6
    Join Date
    Nov 2016
    Posts
    2,281

    Default Re: Just slap on some paint

    Quote Originally Posted by pvb View Post
    Don't believe everything you read in sailing magazines! Leave it alone, you must have better things to do!
    Indeed I do.... but going for a NVQ in Displacement Activities.


    As for
    Red paint will radiate more heat than a shiny silver alternator
    I seem to recall that radiation is a matter of 'emissivity' - and that's a whole different bag!
    Last edited by zoidberg; 14-04-19 at 14:48.

  7. #7
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    6,837

    Default Re: Just slap on some paint

    Quote Originally Posted by pvb View Post
    Don't believe everything you read in sailing magazines! Leave it alone, you must have better things to do!
    What about Sailing forum's. Do you believe everything you read ?
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

  8. #8
    Join Date
    Dec 2013
    Location
    Deale, MD, USA
    Posts
    1,648

    Default Re: Just slap on some paint

    Quote Originally Posted by Rogershaw View Post
    Are you sure about that. I know black will absorb more radiant heat than any other colour better is matt black but I cannot remember the effect or the loss of heat by radiation by surface.

    As most heat will be dispersed by convection for are correct that the fan will have the main cooling effect and I wander what any insulation effect any paint will have in reducing the conduction effect from the metal heat sink to the air flow around the alternator.
    Yes, black emits more. For proof, take an IR thermometer and read the temperature of a shiny stainless object, and then a dark spot on it nearby. On hot piping, the difference can be 20C or more. I often painted black dots on SS refinery equipment to improve trouble shooting readings. For example, polished aluminum has an emissivity 20x lower than black paint, but dirty aluminum is not much different.

    https://www.thermoworks.com/emissivity_table

    However, I doubt radiant cooling matters much compared to convection. What matters is air movement; keep the fan clean.
    Last edited by thinwater; 14-04-19 at 16:16.

  9. #9
    Join Date
    May 2001
    Location
    UK East Coast
    Posts
    35,507

    Default Re: Just slap on some paint

    Quote Originally Posted by Rogershaw View Post
    What about Sailing forum's. Do you believe everything you read ?
    Certainly not, there's more dodgy information and folklore presented here as facts.

  10. #10
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    6,837

    Default Re: Just slap on some paint

    Quote Originally Posted by pvb View Post
    Certainly not, there's more dodgy information and folklore presented here as facts.
    The issue then becomes what is dodgy information and folklore and what is real and true facts.

    What one person considers dodgy information another person will consider as true facts. and how does the inexperienced poster separate the two.
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

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