Explosion-Proof bulkhead?

Discussion in 'Fiberglass and Composite Boat Building' started by massandspace, Oct 6, 2021.

  1. massandspace
    Joined: Sep 2017
    Posts: 45
    Likes: 0, Points: 6
    Location: Salt Chuck

    massandspace Junior Member

    Hello:

    I am building a custom power catamaran....foam/epoxy.

    I am considering putting a propane locker on the other side of a bulkhead that my sleeping head would be right next to. That bulkhead is currently 3/4" thick NidaCore skinned with 15 ounce biax cloth on each side.

    If the tank were ever to explode, I believe it might take my head off. Or at minimum severe injury.

    My idea is to add a sheet of carbon fiber or Kevlar (does that still exist?) on the locker side of the bulkhead. Is that a good idea? What weight?

    There is a 12" by 16" "light-duty" hatch to access the locker.....so I am sure that would blow out first, upwards. And I plan to add a propane sniffer/shutoff inside the locker itself, so I think the chance of an explosion would be minimal, but just trying to be safe.

    Ideas welcome.....

    .
     
  2. fallguy
    Joined: Dec 2016
    Posts: 5,874
    Likes: 1,160, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    The greatest danger is leaving a burner on. The sniffer belongs near the appliance; not in the locker. The locker requires a drain in the sole and down for propane. The likelihood of explosion while you are sleeping is ultra low. If your locker explodes; it will break the cam handles of the 12x16 way faster than toward you. If you want to add a layer of glass and tabbing to help you sleep better; go for it. Carbon won't be worth it.
     
  3. fallguy
    Joined: Dec 2016
    Posts: 5,874
    Likes: 1,160, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    In order to have a 2nd sniffer and solenoid; you'd need quite a bit of room to mount it all and the mounting itself can become a liability.

    what cat are you building btw?
     
  4. bajansailor
    Joined: Oct 2007
    Posts: 2,662
    Likes: 988, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Don't even think about trying to contain an explosion - whatever you do, it will not work.

    Instead, always ensure that you are religious about turning the gas off at the bottle every time that you have finished using the stove.
    It is even better if you turn it off at the bottle and then burn up the gas in the line before turning the knob on the stove off.
    And make sure that the regulator is properly attached to the bottle, the hose is in good condition, and all the connections are tight.

    I vividly remember seeing photos of a large sailing yacht (a Nicholson 55) in Poole Harbour in England after she had suffered a gas explosion - she looked as if somebody had taken a giant meat cleaver to the hull and sliced it open.
    Here is the MAIB report about this incident.
    Explosion on sail training vessel Lord Trenchard with 4 people injured https://www.gov.uk/maib-reports/explosion-on-sail-training-vessel-lord-trenchard-in-poole-harbour-england-with-4-people-injured

    And there are some impressive photos here showing the result of what happened after a team from Yachting Monthly carried out a 'controlled' gas explosion on a yacht.
    https://www.admiralyacht.com/wp-content/uploads/2016/07/crash-test-boat-gas-explosion.pdf

    Along with a video showing the boat blowing up - it was posted in this link :
    https://www.yachtingmonthly.com/sailing-skills/crash-test-boat-gas-explosion-29779

     
    Last edited: Oct 6, 2021
    hoytedow and DogCavalry like this.
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,401
    Likes: 1,033, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Wise words ! Even in the Acme Products catalogue they wouldn't have such a thing
     
    hoytedow likes this.
  6. bajansailor
    Joined: Oct 2007
    Posts: 2,662
    Likes: 988, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Wil E Coyote found that out the hard way! :)
     
    hoytedow likes this.
  7. Ad Hoc
    Joined: Oct 2008
    Posts: 7,276
    Likes: 1,165, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    hoytedow likes this.
  8. bajansailor
    Joined: Oct 2007
    Posts: 2,662
    Likes: 988, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    I just watched the video in this link, hoping to see them do a controlled explosion to prove how effective their product is - but no, all they did was take the blanket out of it's bag, drape it over the suspect bomb, and then pack the blanket away again afterwards.
    Surely if the blanket is just lying over the bomb, and the bomb goes off, it will just send the blanket flying?
     
  9. Ad Hoc
    Joined: Oct 2008
    Posts: 7,276
    Likes: 1,165, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    I wondered that too... and also sadly disappointed the video did show it. :(
     
    bajansailor likes this.
  10. kapnD
    Joined: Jan 2003
    Posts: 975
    Likes: 210, Points: 43, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    Make sure that the explosion will vent away from your sleeping head by using weak fasteners like friction catches on the door side.
    Maybe put a flak jacket on the tank?
     
  11. wet feet
    Joined: Nov 2004
    Posts: 867
    Likes: 175, Points: 43, Legacy Rep: 124
    Location: East Anglia,England

    wet feet Senior Member

    I wouldn't expect the gas bottle itself to explode without warning.Why would it?A fire beneath it might lead to a situation where the risk became real but the smell of that would be powerful and grab your attention.It would be normal good practice to have the locker drain overboard and thus the gas shouldn't encounter any source of ignition and thus the risk is almost eliminated.Normal safe procedures would see the gas tap turned off at the bottle after use and it would be prudent to have a gas detector in the bilge as well.

    If it makes you feel better then a laminate of Kevlar in the bulkhead might contain some fragments or it may mean the bulkhead tears itself loose and the panel moves.I doubt that either of these situations would ever arise as the locker lid would leave the scene first at high speed in the unlikely event of a catastrophe.I haven't researched the statistics but would be surprised if any of the few boats that do suffer gas related disaster are equipped with functioning gas detectors.I have witnessed the spectacle of a couple of fellows solemnly emptying buckets of what looked like air over the side of their boat when the gas detector told them it had sensed a problem.Opening all hatches and letting the breeze do the work might have been equally effective.
     
    bajansailor likes this.
  12. The Q
    Joined: Feb 2014
    Posts: 212
    Likes: 39, Points: 28, Legacy Rep: 21
    Location: Norfolk, UK

    The Q Senior Member

    I'll Add to That HMSTY Trenchard (Named after the effective founder of the Royal Air Force) was built like a brick out house, I sailed on a sister yacht (HMSTY Racer) a couple of years earlier than the accident, very heavily built for sailing round the world..

    Our local regs say New gas lockers have to be vented overboard, old boats pre this regulation that have a gas locker base below the waterline though don't have to be altered..

    If you can vent overboard then do so , My gas locker on the motor boat, was the seat for the helm, but vented through bottom of the gas locker, through the hull about a foot above the water line..
     
    bajansailor likes this.
  13. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,401
    Likes: 1,033, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I dare say a lot more people have died from gas leaks in confined spaces than explosion
     
  14. fallguy
    Joined: Dec 2016
    Posts: 5,874
    Likes: 1,160, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Another thing you can do is turn off the solenoid valve. It is one step less than turning off the bottle, but turning the valve off means any leak is confined to the locker and won't travel into the boat spaces.

    When wiring the boat make sure the solenoid is always on an unswitched supply as all safety monitoring.
     

  15. DCockey
    Joined: Oct 2009
    Posts: 5,071
    Likes: 550, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    The tank itself will not explode as it is filled with propane and no oxygen. A leak which results in a propane concentration between 2.1% and 10.1% by volume can result in an explosion if ignited.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.