Tar as bottom paint?

Discussion in 'Materials' started by BenMP, Mar 9, 2011.

  1. BenMP
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    BenMP Junior Member

    I have read that many of the older sailing ships and work boats (not to mention the Ark) used to have the bottoms tarred.
    Is tar a decent bottom sealer?
    Does it have any anti-foul characteristics?
    Does it deter ship-worms?
     
  2. PAR
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    PAR Yacht Designer/Builder

    Tar would likely raise the eye brows of the local USCG as they noticed there was a constant, oily slick around you boat. Tar wasn't used as an anti-foul as much as it was a bedding for copper plates. Tar was a moisture proofer and used above the LWL on everything (literally) to keep water out.

    Anti foul characteristics? Sure, but it not as good as you'd think, as it'll scum up and act like anything else pretty quickly.

    Ship Worms, probably, but again getting this treatment past the USCG will be a test, unless you have historical status and can "sell" the idea to them.
     
  3. Fanie
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    Fanie Fanie

    If I'm not mistaken then tar does dissolve in water to some extent. Many of our roads get new potholes during/after rain indicating there is a deterioration.

    Also similar to butyl tape when it gets cooled down enough it becomes brittle and break or shatter when flexed.

    I'm not sure what exactly the tar was they used on the arc, but it may have been a bit different product we know as tar. That or you may want your boat to stay afloat only for 40 days and 40 nights :rolleyes:

    Don't know what you have in mind, but you are aware that one can cover a wooden boat using epoxy ?
     
  4. BenMP
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    BenMP Junior Member

    Thanks,
    That is about what I thought.

    PAR, I hadn't thought about the "oil spill" (isn't it up to $1000 per incident?) effect.
     
  5. kroberts
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    kroberts Senior Member

    Not sure, but I think you should ask BP about that.
     
  6. PAR
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    PAR Yacht Designer/Builder

    If the local Harbor Patrol sees a slick, they'll ask you to fix the problem. If it's a continuous issue, they'll force you to haul the boat to fix the problem, at which point then the liability insurance of the marina, will kick in with OSHA and other requirements. I'm pretty sure the travel lift operator will catch hell for smearing tar all over his straps. Trust me, you're not going to do this or get anyone to lift your boat, so unless you can trailer the puppy, you're pretty much out of luck.
     
  7. Poida
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    Poida Senior Member

    Fanie. I think you may find that the "pot hole" in a road is due to the deterioration of the substructure of the road ie. sand being washed away from beneath the tar.
     
  8. PAR
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    PAR Yacht Designer/Builder

    Fanie was referring to his old hippie days, when pot and hole went together naturally.:rolleyes:
     
  9. CDK
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    CDK retired engineer

    Tar works great as an anti fouling on Mercruiser stern drives.
    I used to spray it on, diluted with gasoline, then in the autumn removed the tar layer with all marine growth using gasoline only. Not very environment friendly I must admit, but that wasn't the issue here.
     
  10. swabbie

    swabbie Previous Member

    I used tar to bed the timber keelstrom (10'' wide) into fabricated steel ballast keel (long keel) on several 25m tradional schooners I refitted. The tar is an excellent bedding compound and joint sealer but during lift out it gets soft on a warm day then goes brittle when reimmersed. Traditionally it was used to 'glue' felt as underlay for copper sheathing but as an anti foul, hopeless. Bugs eat it, grass likes it and for teredo worm - zero effectiveness.
     
  11. pistnbroke
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    pistnbroke I try

    only australia could build a tar road on sand .......in the rest of the world we put loads of aggrigate under it ....ha ha ....
     
  12. BenMP
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    BenMP Junior Member

    That is what I was a afraid of. I have seen tar balls on the beach with barnacles on them.
     
  13. rwatson
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    rwatson Senior Member

    But there are bitumnious compounds that do work, Over here, I have used Pabco Brushable Hydroseal, there is probably similar stuff 'over there'

    It looks for all the world like a fairly light tar, but it dries on the surface so that it doesnt rub off and stick to stuff (much). Its suitable for waterproofing say, the inside of tanks, and it makes a good emergency leak repairer on any type of hull (wood, fibreglass, steel, aluminium - sticks to anything even when the surface is wet) . It stays very flexible when 'dry'

    I have used it on fabric canoes - and its very effective, but quite black and uneven to look at.
     

  14. CDK
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    CDK retired engineer

    rwatson you are probably right. The stuff you use and I used for the Mercs is quite different from the black balls on the beach, although both may be called tar and originate from an oil refinery. I doubt if barnacles get a good grip on the flexible layer, they are certainly easy to remove.
     
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