How Much Air Pressure For Leak Test

Discussion in 'Sunfish Talk' started by ref0716, Oct 18, 2010.

  1. ref0716

    ref0716 New Member

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    I plan on doing a leak test on a newly acquired '85 Fish. The procedure here in the Knowledge Base seems straight forward enough, except that I do not understand the reference to using compressed air of the 3 ounce variety. I will use a compressor, and can regulate the output pressure from almost nothing to 130 psi. What would a reasonable pressure be? I surely do not want to make any new leaks. Thanks for your help.
    Richard
     
  2. Wavedancer

    Wavedancer Upside down? Staff Member

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    3 oz probably translates to 0.2 psi.

    You don't really want to test the adhesive limits of the expanding foam that holds the styrofoam supports in place. All you need is some inside pressure to get the soap film to bubble. A bicycle or air-mattress pump will work just fine.
     
  3. PBA

    PBA Member

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    Surprisingly, it only takes about 3-4 pumps of a bicycle pump to do the job.

    Also, while some leaks may pop up right away, I had one situation around the coaming where it took nearly 8-10 minutes for the leak(s) to pop up. Good luck.
     
  4. odegaard

    odegaard cAPTN oDIE

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    try a leaf blower, or blow side of a vacuum, works good, tape up the inspection port but leave some open so not too much pressure inside
     
  5. Alan Glos

    Alan Glos Active Member

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    I think a leaf blower or a shop vac on blower mode is overkill and risks making holes/cracks in addition to finding them. As noted above, it does not take much air flow to produce the telltale bubbles in the soapy water you apply to the hull. If you have one of those air in a can devices that Office Max sells, a few squirts of air from such a can into the small hole on the forward side of the cockpit tub or thru a taped up deck drain is about all you need. I once saw a Laser damaged by too much air inside for a leak test. Easy does it.

    Alan Glos
    Cazenovia, NY
     
  6. ForestLake

    ForestLake New Member

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    I've had good luck using a hair dryer, with the heat set to off, placed around the drain hole on the deck. It provides a limited, but constant air flow which is what you need to find the leaks.
     
  7. Geophizz

    Geophizz Member

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    Somewhere I saw someonre recommend an aquarium air pump. I have an old one kicking around, and I'll try it once I patch my daggerboard trunk.
     
  8. Light and Variable Winds

    Light and Variable Winds Well-Known Member

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    Checking today's email , a vendor sent a collection of items, including an "oxygenator".

    This is a $22, low pressure, solar-powered air pump with cords for charging when there's no sun, and different lengths of hoses for inserting into the Sunfish vent or drain.

    For drying an internally-drenched Sunfish over-winter, it would probably be too slow. But since it does produce 0.3 liters/minute, it would be perfect for maintaining a gentle pressure internally for Sunfish leak-tests. Alternatively, it could be used for keeping bait fish "fresh".

    [​IMG]
     
  9. Webfoot1

    Webfoot1 Active Member

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    I would not exceed 2.5 psi. This is what is used for testing fuel tanks. We put
    a air pressure gauge on the tank, pressurize and let sit for 24 hours to see if it will hold
    pressure. There is a vent hole in the front of the cockpit wall you will have
    to tape over.
     
  10. signal charlie

    signal charlie Active Member Staff Member

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    I'd turn the compressor down as low as possible and just put a squirt of air in the hull. You can blow it in through the drain plug or the vent hole. A spray bottle with soapy liquid works great.

    Seems like someone put a valve stem in the drain plug hole and hooked their tire pump to that. We use a lot of air but there are so many holes in this boat it didn't matter :)





    Cheers
    Kent and Audrey
     

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