fuel tanks and batteries

Discussion in 'Boat Design' started by rasorinc, Jul 5, 2012.

  1. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    I'm working on a 20' trailer. I want to mount a 20' boat upside down on the roof of this trailer. I have the structural worked out and the roller system and winch capabilities. I am worried about the fuel tank(s) water tank and waste tank in the boat. I can put double shutoff valves on intake and outfow lines and the securty of the hold downs I can design. 2 batteries
    sealed type will be secured to the bottom fail safe. Does anyone see a problem with this idea. Will probably use 2 smaller fuel tanks rather then 1 large one. Outboard engine will be removed and put on the trailer. Thanks much, Stan
     
  2. MechaNik
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    MechaNik Senior Member

    Just because the battery is sealed doesn't mean it can be turned upside down, especially lead acid.
    Man holes and sender mounts are usually very ordinary on tanks and may leak.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Tank vents will leak too, though you might get by with check valves. What is the reasoning behind carrying this boat upside down on a trailer roof?
     
  4. CDK
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    CDK retired engineer

    Yes Stan, I see lots of problems.
    Getting the boat on and off the roof is one of them. When you arrive at your holiday (or even worse, weekend-) destination, heavy labor awaits you and instead of enjoying yourself you are sweating within a circle of spectators who all have already figured out what you did wrong and cannot resist the urge to tell you about it.

    On the road, the weight of the boat puts the trailer's center of gravity dangerously high, so it may start swaying and be difficult to control, so you need to drive slowly and arrive late at your destination.

    And most important of all: it is virtually impossible to completely seal tanks and batteries. Changes in temperature increases the internal pressure and forces liquids out. Fuel on your trailer roof doesn't always create a fire hazard, but if the battery acid burns a hole in your roof, things may escalate very quickly.

    I have some experience with weird vehicles. I once built an RV with a Glastron Bayflite in it, like a piston in a cylinder. Just the stern drive poked out, so to most people it looked like an amphibian. Pulling it in with the winch was easy, but after 2 days on the highway the rubber rollers flattened by the weight of the boat, so it refused to come out. Lots of spectators, all with brilliant ideas, tropical temperatures, finally two guys with crowbars, wooden wedges and a sledge hammer......
     
  5. hoytedow
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    hoytedow Bananas

    I'm glad I went for micro camping. I can carry the boat in the truck while I pull the teardrop trailer behind it. Nothing is upside down except the hull dolly. :)

    Of course it is only comfortably large enough for 2.
     
  6. rasorinc
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    rasorinc Senior Member

    Thanks for all the replies. I now see the problems that have to be cured. I want to carry the boat on the trailer as I need both for extended travel. It would sit down (upside down) over the side edges of the trailer supported by corbels with boat rollers at the top. Boat will have a garvey bow. Trailer is 7'wide and 7' tall plus frame and 14" tires, 4 of them. boat would recess down over the trailer about 6" as the beam is going to be 8'to 8'-6". It will be light but still weigh about 900 to 1,000 lbs. My thoughts now are easy removal of the batteries, no waste tank. Use porti-poddy and remove to trailer. Same with fuel-use removable fuel tanks and store on trailer. Trailer is really 17' long with a 3' open deck storage area in the front, so 20' overall plus tongue.
    Any further thoughts folks. Stan Trailer shape is a modified Tear drop.
     
  7. hoytedow
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    hoytedow Bananas

    Sounds good. Just make sure corners of boat don't strike tow vehicle during road turns.
     
  8. rasorinc
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    rasorinc Senior Member

    Thanks Hoyt, tongue and receiver will be about 8' forward. Trailer has 4" drop 3,500 lb axles. Boat will have 15" bow and transom wheels.
     
  9. gonzo
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    gonzo Senior Member

    I still don't understand the possible advantages of turning a boat upside down for transportation and then turning it upside up for launching every time.
     
  10. rasorinc
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    rasorinc Senior Member

    Gonzo, it just reduces height and lowers the weight because the keel on a 3/12 pitch is not holding the boat up high. Also the flat side rails hit on equal height rollers where bottom pitch would mean rollers must be held up high. take a look at this loader for small, light boats. http://boatloader.com/boatloader.html
     
  11. hoytedow
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    hoytedow Bananas

    It won't catch rainwater when its upside down. It also leaves less of a face to the wind from the front when trailer top is able to recess into boat.
     
  12. rasorinc
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    rasorinc Senior Member

    When boat is able to recess onto and over the top of trailer. Thanks Hoyt.
     
  13. viking north
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    viking north VINLAND

    Batteries--fuel tanks--water tanks--holding tanks --along with the motor will have to be removed. Not to do it and messing around with check valves would be more trouble than it's worth not to mention the results of a stuck open check valve on the holding tank. CDK brought up an important point C of G . I have a fair amount of experience building trailers/campers/motorhomes. A trailer 7 feet wide and 7 feet high sitting on wheels/springs and axils in itself will be none too stable. Adding your boats estimated weight and it's a recipe for a rollover. A 10 foot wide(outside to outside of tires) dual axil trailer would be my choice. ---
     
  14. hoytedow
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    hoytedow Bananas

    Watch out for cross-winds and semi's coming from the opposite direction.
     

  15. rasorinc
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    rasorinc Senior Member

    I've never made tubes but have a video on how to do it so maybe a RIB should be considered. With a wood hull, of course.
    Deflated tubes with an 18" high hull should remove a lot of weight topside and height. Just a thought. outside to outside of tires is 8'-5" It will have duel axles.
     
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