gelcoat V's painted finish

Discussion in 'Hydrodynamics and Aerodynamics' started by mrmac, Dec 16, 2011.

  1. mrmac
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    mrmac Junior Member

    Hi all, I have tried searching the archives, but cound't find anything relating to my question so here goes:-

    Is there any performance advantage between paint or gelcoat finish on a high performance dinghy or catamaran?

    Assuming that both finishes are as new and both done by competent builders.

    Would appreciate any info, or references to papers done on the subject.

    Cheers

    Andrew
     
  2. HakimKlunker
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    HakimKlunker Andreas der Juengere

    There cannot be a difference (my opinion) because both materials are man made products with more or less identical properties. The difference is how -or when- they were applied; I think here of high-end products - emulsion wall-paint sure would make a difference; but you mentioned professional procedures...
    What really influences performance, is surface quality and/or treatment. But this is not related to the nature of coating material.
    For dinghies (and cats) I would not have heard about tests or literature. But the racers constantly run their own tests and experiments. I have seen painted (sprayed) boats outrunning the competitors and the other way round, too. I have seen waxed, polished, wet-sanded hulls and never saw a racing result clearly advocating a specific coating material.
    High performance also means: short life. Not even durability is an issue here and so my conclusion is - there is no advantage.
     
  3. mrmac
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    mrmac Junior Member

    Thanks,

    I was also searching the web for info and all I can find is research on commercial ship hulls and the comparative fouling levels effect on performance...

    not really relevant for small racing boats!
     
  4. PAR
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    PAR Yacht Designer/Builder

    Assuming two identical boats, one gel coated and the other painted, there wouldn't be any appreciable difference between the two, unless special steps were taken. Then to make things fair, the same steps need to be utilized on both, such as a high polish job. Both paint and gel coat can be made much smoother with buffing, but frankly, it's still not going to offer much (fractions of a knot) and certainly no distinct advantage.
     
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  5. HakimKlunker
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    HakimKlunker Andreas der Juengere

    Yo: I have seen so many guys discussing boat performance for hours:
    At the club bar; in the evening
    This normally goes together with numerous drinks.
    And next day they spoil each second tacking during the race because the have a terrible hang over.
    :D
     
  6. michael pierzga
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    michael pierzga Senior Member

    Gelcoat is soft , easy to polish and easy to repair. Since gelcoat absorbes water your boat may become heavier ?

    On a racing bottom water runs off...it does not bead. Avoid wax, as water will stick to it.
     
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  7. NorCal
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    NorCal Junior Member

    We never polished our racing sailboats but would wet sand with 1000 grit.
     
  8. michael pierzga
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    michael pierzga Senior Member

    As far as I know wet sanding gives the fastest surface. I dont know anything about these new McHarken coatings
     
  9. HakimKlunker
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    HakimKlunker Andreas der Juengere

    Here we go :D
    A real race boat (we talk dinghies (?)) will not remain in the water and will survive 2 race seasons at best. Don't worry about water absorbtion here.

    Water will always stick to the hull in the laminar layer. One theory here says that friction between two identical materials is minimal - and so the laminar layer is rather an advantage because otherwise water full flow in direct contact with the hull with higher drag resulting.
    As long as the smoothness of the surface matches the speed it is not important how 'hard' the material is - the surrounding water always will be 'softer'.
    Personally I support the wet-sanding theory: it smoothens out and removes unwanted particles. I also tried waxing before but found no performance advantage: My racing results were still the same. But the boat looked better :D
     
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  10. PAR
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    PAR Yacht Designer/Builder

    More important then smooth is "fair symmetricity" . If you're hull is the same on both sides and sees reasonable care in regard to the surface condition, then the best advice you can get is hone your sailing skills.
     
  11. HakimKlunker
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    HakimKlunker Andreas der Juengere

    In the beginning it was aid
    'Assuming that both finishes are as new and both done by competent builders.'

    I somehow assumed that this includes symmetry.
    Sailing skills - Very correct. Perhaps to mention tactical skills here as well?
     
  12. sabahcat
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    sabahcat Senior Member

    Paint is far lighter than gelcoat
    Light = Fast
     
  13. tunnels

    tunnels Previous Member

    Ok heres a thought for all to consider

    Clear Silicone and acetone on a rag and polish the surface then let dry . When dried wash with water !! the water just flies off the suface . I used this method on my outbard bottom end and it stayed 99.9 % clean all the time , theres not even any black from the exhaust around the propeller !!
    Careful with the acetone it could attack your paint work !!!!.

    I used to work making Spa pools !!,with Mosaic tiles and all the tiles were suck using clear silicone . The tiled pools always stayed clean and no body oils and fat stuck to the sides of the pools !.The ones with no tiles were scungy and dirty most times.

    Acetone did completely disolve the silicone but almost did!!:p .
     
  14. michael pierzga
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    michael pierzga Senior Member

    Many people spray McLube dry teflon on the fibergalass hull of rib tenders. Allows the rib to stay in the seawater for a few days too long . the gribble and slime wash off with a hose squirt.
     

  15. Perm Stress
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    Perm Stress Senior Member

    Gelcoat is heavier than paint. :)
    On small boat this weight is a noticeable percentage of total weight => detrimental to speed.
    All the rest is down to small and large scale smoothness, and waxing/not waxing/whatever.
     
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