Floating nightmare

Discussion in 'Stability' started by Callinectes, Jun 4, 2007.

  1. Callinectes
    Joined: May 2007
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    Location: South Florida, USA

    Callinectes Junior Member

    A friend of mine is completing a rather extensive refit of what he believes to be a 1980-82 21ft Cobia runabout (I haven't bothered to research the HIN because frankly I don't care, the boat is a real piece of you-know-what right now). He has gutted the hull and replaced all the stringers, rebuilt the seized V-8 Mercruiser and turned it into a hot rod. The distributor, alternator and starter are all high performance automotive(shudder). When he gutted the hull to replace the stringers, he removed the high density foam that filled every void between the stringers, now its all void. The exhaust, instead of exiting below the waterline as designed, is now going to go straight out the transom (About 2 feet above the waterline). So there you have it. Hot rod engine in a small boat, all auxilliary flotation removed, the weight of the exhaust system now shifted about 2 ft higher than designed, unapproved engine electrical components. My question is, assuming it does not turn into a fire bomb when he starts that engine, does anyone care to speculate as to the shift in the centers of buoyancy and gravity and the righting moment? Please do not assume that because I use those terms, I know how to calculate them. I was taught these things as a small boat operator in the Coast Guard. I am a very rank amateur designer(in other words, I draw pretty pictures of boats in my spare time and have been introducing myself as a "future Westlawn student" for the past 20 years!) I just can't help thinking that removing all that foam, which was actually fairly heavy, didn't have some adverse effect on the stability of this vessel. Thanks for any help you can provide.
     
  2. charmc
    Joined: Jan 2007
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    charmc Senior Member

    Not so uncommon, unfortunately. The foam is required by USCG regulations, but those apply to the mfr. I don't know if there is a penalty for owners who remove flotation. Perchance, did he replace the bilge blower? That is a special class motor, commonly called explosion proof, and built to a strict standard. Replacing it with a regular duty motor is a virtual guarantee that the boat will become a roman candle some fine day. Of course, it may not matter. If he thinks marine and auto electrical parts are interchangeable he might not ever run the bilge blower. I don't suppose he'd be interested in taking a Safe Boater course?

    The "rebuilt" boat will be more tender, not much fun to be in at rest, I think, but the designers here can address questions of stability.
     
  3. Frosty

    Frosty Previous Member

    Dont you think you Americans are getting a bit paranoid about this stuff.

    I have put car engines in many boats.

    There was NO such thing as a petrol marine engine for ski boats in the 60s.

    I never ever had a bilge blower, -- all standard car dynamos, distributor, cut out etc etc.---All sparking away under the hatch there.

    Ive never been blown up , seen one blow up ,or heard of one blowing up.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Actually, marine engines have had spark arresters (and other devices, like vapor seals on the throttle shafts, contained bowl vents, etc.) on them form a long time (including the 60's), which go beyond the carb air inlet. Gas powered boats have been blowing up well before the 1960's, lots of them.

    The CG shouldn't be affected much by the moved exhaust and removed foam, certainly not enough to get excited about or effect boat trim.

    If he leaves the engine cover off, he may be able to run it for quite a while before blowing himself to hell. Unfortunately, many times these types, also blow up loved ones and strangers, that happen to be in the wrong place at the wrong time too.

    I've seen it happen more then once, so talk to this bone head, get him a date, whatever it takes. Maybe the local harbor patrol will catch him on his first ride out and rack up enough tickets to get him to do it safely. Possibly, he'll get lucky and set the transom on fire first, (especially if he's removed the jacketed exhaust) and this should burn off some of the lingering vapors, hanging out in his bilge.

    See if you can get life insurance on the guy. You might as well get something out of the deal . . .
     
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  5. Frosty

    Frosty Previous Member


    Not in Uk

    Albatross, Moonfleet, Delta, just off the top of my head were straight car engines. No air filters, every thing standard car parts.

    The Albertross didnt even have agearbox --drove off the front pulley. Push it round in the direction you want to go ,push the button and away you went. Never ever seen one blow up.

    Then there was this thing I had that took the Windermere speed trials in Oh 72 or something BMW 2001 with twin delorto's.

    Maybe you guys have got messy leaking fuel lines or something.
     
  6. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    Thats why I prefer diesel heat & propulsion, and burn fuel oil to heat my house. Enough inherent stress in life without complicating matters by living with a potential bomb!

    Done properly a gas powered vessel can be relatively safe, never as much as a diesel, engine wise though, IMHO.

    Tim
     
  7. Guillermo
    Joined: Mar 2005
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    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    Interesting statistics

    Recreational Accidents 2000
    Florida 1994 – 2000
    1194 total accidents involving 1738 vessels
    3/19/2001

    By Type of Accident
    Based on first harmful event as determined by the officer
    Rec Cruising .................................... 1060
    Rec Fishing ........................................117
    Commercial Purpose ..............................52
    Skiing .................................................24
    Making Repairs ....................................18
    Fueling ..............................................13
    Boat Pulling Tube ................................12
    Starting Engine ....................................12
    Racing ..............................................10
    Swimming/ Snorkeling ............................ 9
    Scuba Diving ....................................... 8
    Hunting ..............................................3
    Tournament ........................................2

    By Type of Accident
    Based on second harmful event as determined by the state reviewing authority
    Fall Overboard ..................................127
    Capsizing .......................................... 56
    Fall In Boat ...................................... 45
    Sinking ............................................ 43
    Struck By Boat (Person) ......................41
    Collision With Fixed Object ...................32
    Flooding (Swamping). ..........................29
    Fall on PWC .......................................24
    Collision With Vessel ............................14
    Struck by Skeg/ Prop ...........................12
    Vessel Wake Damage ...........................12
    Fire Explosion (Fuel) ............................10
    Collision With Floating Object/ Person ....10
    Grounding ..........................................9
    Struck Underwater Object .....................2
    Skier Hit Object ....................................1
    Other .................................................1


    By activity at the moment of Accident
    Cruising ......................................... .. 678
    Changing Direction .......................... ...342
    Docked (Moored) ............................. ...199
    At Anchor .........................................104
    Docking/ Undocking ..............................80
    Changing Speed ...................................79
    Drifting ............................................... 75
    Other ................................................. 60
    Wake/ Surf Jumping .............................. 26
    Sailing ................................................ 12
    Launching/ Loading ................................. 8
    Being Towed ......................................... 2
    Towing A Boat .......................................3
    Rowing/ Paddling .................................... 3


    May we asume a proportion of 10 in 1194 (0.84%) as explosions related with engine starting? (No fuel is discriminated, but I asume it is gasoline in almost all cases).

    This is not enough info, as we do not know how many of those 1738 vessels had an engine. Anyhow explosions related absolute numbers seem to be not very high. Now, asuming those accidents were related with inboards rather than with outboards, we should know the number of boats with an inboard gasoline engine registered in Florida those years. And from those, which ones do have 'car type installations' and/or not blowers, etc. That would be the most significative statistic we'd need to be able to give a based opinion on its dangerouness.

    (Please be aware I strongly defend all and every safety measures to be taken with gasoline installations)

    From the point of view of stability, I tend to agree with PAR on the small influence of the moved exhaust and removed foam.

    Cheers.
     
  8. StianM
    Joined: May 2006
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    StianM Senior Member

    I gues you all hear about the Napier Deltic.

    It was first designed to provide a high powered diesel to replace the dangarous petrol engines from the high speed Navy boats Like the MTB's

    1 tea cup off gasoline evaporated is equal to 1,5kg dynamite.

    You have to be unlucky to make it blow up, if the mix is too lean it won't ignite and if it's too fat it won't ignite and then you nead a source for ignition.

    A seal leaking oil on the naked ekhust manifoil would be sutch a source or a faulty ignition systen/dynamo.

    Your in the US tell him he can be sued by a famely only by parking he's boat next to theres, because they can claim he put them in danger(if they really can don't mather as long as he think they can) people sue McDonalds for making them fat so why not this.

    If sence can not make him do it right then tell him it can be exspensive.
     
  9. marshmat
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    marshmat Senior Member

    I agree that the stability changes will probably be small.
    I also agree that a hopped-up car engine, with unshielded exhaust, car alternator/starter, no flame arrestor, etc. in a boat is flat out stupid. Car engines can run in boats just fine, in many cases. But the environment is far more volatile and appropriate safety precautions must be taken in the design, construction and installation of all that equipment. Gas vapours in a car drift down to the road and dissipate. Gas vapours in a boat collect in the bilge until they drift up high enough to reach something electrical. It's not any harder to do it right, nor is it that much more expensive, but it saves you from blowing yourself up.
    One interesting side effect of removing all the foam may be that if he does something dumb out on the water, the boat will probably go straight to the bottom before it has a chance to explode.
     
  10. Callinectes
    Joined: May 2007
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    Callinectes Junior Member

    Thanks!

    Thanks for all the replies, folks. I am going to print them out and show him. See if he will come around.
     
  11. alan white
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    alan white Senior Member

    Throughout the eighties and nineties, a lot of gas engined sailboats just wouldn't sell. A lot of conversions, replacing Atomic fours especially, a particularly well loved and popular gas engine.
    Owners would scoff at the wisdom of gas engines in sailboats. The thing was to remove the offending machinary and spend thousands on a Yanmar or a Volvo.
    I had a two stroke single 7 hp Vire, a smooth and reliable engine with few moving parts, very reliable.
    I'd get into a conversation with guys who'd converted to diesels from time to time, and I'd ask them, "So, what are you using for a stove?"
    the answer, invariably was "Propane----- that alcohol stove you use doesn't get hot enough!"
    "Propane in the cabin," I'd say, "You keep a fan blowing when the valve is open?"
    "Of course not," they'd say, "Why?"

    A.
     
  12. StianM
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    StianM Senior Member

    I have gas at home and I hate it. I would prefere electric even if it take longer time to heat up. I hate having to test the coupling with soapwater everytime I change bootle and I keep the whole instalation out on a overbuildt balcony. No way I bring it into the house. Maybe I go and buy myself a alcohol burner. I forgot that those even exsisted even I used them for years when I was enjoying the woods and montains in Norway.
     
  13. alan white
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    alan white Senior Member

    Prices here for propane in BBQ tanks have risen so that I've analyzed the cost and now people could use electricity for their cook-outs and spend the same or a bit less. We pay 15 1/2 cents per kwh here in Maine. I have a gas stove, but I don't keep ot hooked up. Electric is all I use for hot water and cooking.
    I have wood heat.
     
  14. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    A friend in Alaska had his boat tied up in Wrangel, SE, AK.

    Him and his tomcat Greasy woke one morning and Joe went to light the propane cooker for coffee.

    Blew sky high. Boat destroyed. They both survived but Joe had serious burns to 80% of his body & lost an eye. Greasy had all his hair burnt off. Joe still has numerous problems.

    Tim
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Gas powered craft that experience catastrophic difficulties, are not that common any more, though here in Florida, It happens regularly enough to keep it in the forefront as we make repairs and upgrades to our craft. This is a direct result, of the engineering around containing and controlling the vapors, getting them into the engine or out of the boat.

    This wasn't the case. As a young lad, I saw many burning boats. I grew up in an area of working sail and home built power fishing vessels. These burned at a regular rate, during my childhood. I lost a family friend to an explosion, as he started his boat one morning. We all had boats, usually more then one and gas power was always considered playing with a loaded gun. This belief still lingers today, likely from folks my age who remember what happens, when you remove flame arresters or install equipment that will generate sparks.

    Regulations, (as much as they often suck) have really clamped down on the likelihood, a production craft will kiss it's own *** goodbye. Young folks of today, don't have the life experiences to make them wonder if gas is for them, so their fear of the type, is much more muted, justifiably so.

    It's only responsible, to suggest the proper way of getting at an issue like this correct. It's quite irresponsible to recommend anything other wise, in spite of one's personal experiences. You may have gotten lucky in your boating life, but hoping for the best with ill advise, for someone else, is flatly wrong and a disservice to the people asking for direction.
     
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