Help to raise my boat from the bottom of a lake

Discussion in 'All Things Boats & Boating' started by sean-nós, Nov 7, 2015.

  1. sean-nós
    Joined: May 2010
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    sean-nós Senior Member

    So my boat sank back in May and it's been a bit of a job trying to find her the full details of what happened and the search so far can be seen here at the bottom of page 33 http://www.boards.ie/vbulletin/showthread.php?t=2055963665&page=33

    She is a home built Glen-L crackerbox with a 5lt V8.

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    Last week she may have been spotted 11 meters down but I will have to get the divers in to make sure, the shadow of the bow may mean that it has not been down long enough to sink into the silt also it seems to have a light area mid section that could be the engine block so I'm hopeful it's her.

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    Long story short I don't have the funds to get a salvage team out to raise her but I do have some divers that can help me out so if anyone can tell me whats involved in raising her it would be a great help e.g what type and size of lift bags, I have been told that truck tyre tubes would do the job but I feel as she comes to the surface the tubes will expand and could burst.

    Thanks in advance for any tips or advice.:confused:







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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    How cold is that water this time of year ? I'd leave it there, but obviously you might have a different perspective on it !
     
  3. sean-nós
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    sean-nós Senior Member

    It's about 6 deg's C 42.8 F not a big problem to divers in dry suits, I put a lot of time and effort into building her and getting all the parts together so even if I just get the hardware back I can rebuild the rest with not much cost to myself except time, if I had to pay someone else to do the work I probably would leave her there.
     
  4. gonzo
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    gonzo Senior Member

    A small boat like that is not too difficult to refloat. Inner tubes can work, as long as you attach them properly. I don't see cleats on the deck, so they will have to run straps under the boat. 55gal drums also work well. You fill them with water and then get air to float them. It largely depends on the skill and experience of the divers. Boats will rise and turn unpredictably and very fast. It can be a dangerous job.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Beautiful boat, sorry about the problem.

    Water weighs about 62#/ cubic foot (is this salt water or fresh?).
    How much does the boat weight?
    Boat weight/ 62 = number of cubic feet of air required to start to lift the boat, ignoring the possibility of it being stuck in the silt/ bottom.
    At that depth the air will expand a little more than double when it hits the surface.
    But an air tube not in a tire will expand a lot.
    You would have to figure out the size of tube (truck tube?) to get the lift per tube.
    Another thing is how would you tie the tubes to the boat. A single rope tied thru the tube might pinch the tube and cause it to burst when comming up.
    The other thing is attaching to the boat.
    That's a nice slick boat with only one attach point I can see.
    Of course if you have lifting rings on the engine, that might automatically work, since that it the heaviest part of the boat (I assume).

    All of this is arm chair thinking, and knowledge of trying to work out lifting a car about 40 years ago. We never actually tried it.
    Hopefully someone who has real experience will chime in.

    Boy I would really want that back also.

    What kind of an image was that? Sonar?

    Do you have any kind of boats to work from?
     
  6. gonzo
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    gonzo Senior Member

    You don't need to lift the whole weight of the boat. It only need to come to the surface and then the water can be pumped out. You can make a rough estimate of 60% of the dry weight.
     
  7. sean-nós
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    sean-nós Senior Member

    Thanks for your help gonzo I was thinking of putting the straps onto the exhaust manifolds as the main lifting point and one on the bow and stern for balance once she is near the surface I plan to slowly tow her to shallow water onto a submerged trailer then pull her out till she is at water level and pump her out.




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  8. sean-nós
    Joined: May 2010
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    sean-nós Senior Member

    Thanks upchurchmr.
    I'd say the boat engine and gearbox is about 600- 700 KG and she is in fresh water.
    I could put the tubes in a skip bag or some netting that might take the pressure off them I did look at lift bags but they are silly money here :confused:
    I did buy an old Glastron ssv 178 to go and look for her but it turned out I had to replace the floor and transom as they were rotten.

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    She is up and running now ;) I can also get a few other boats involved and maybe a barge if needed.

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  9. PAR
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    PAR Yacht Designer/Builder

    The boat only needs to be just above neutrally buoyant, at which point she'll very slowly rise to the surface, where as mentioned, she can be pumped out. Considering the time she's been down, I'd agree and let her have her fate. Repairing and restoring something down that long is exceedingly difficult.
     
  10. sean-nós
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    sean-nós Senior Member


    I would say exceeding challenging :D all the wood is encapsulated in epoxy resin inside and out, the engine is basic distributor type so not much electrics to worry about also there are no tides or currents in the lake so she won't get too damaged sitting there,if worst comes worst a least I will have all the parts to build another one so for me she is worth the effort of raising her.



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  11. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    I would use the skips bags but instead of inner tubes, I would use plastic garbage can liners in the inverted skips bags and fill them from the expelled air from the divers SCUBA.

    Good luck and get her on the hard before winter envelops Hibernia.
     
    Last edited: Nov 10, 2015
  12. sean-nós
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    sean-nós Senior Member

    Good thinking cheep and cheerful I like it :) or I could even paint them on the inside with a latex paint.

    Another mad idea I had was to make a frame with wings on it that would fit over the bow with the wings at the bottom "a bit like a sub" and then just tow it by the bow eye even at slow speed she should come up if there is enough lift on the wings :D




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  13. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Why waste the latex paint? The trash bin liners, being plastic, would hold the air as it expanded to fill or overflow without risk of bursting when reinforced by the skip bags. A 42 gallon trash can liner full of air will lift about 330 pounds in water, but it must be in a strong container like a skip bag.
     
  14. Poida
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    Poida Senior Member

    As Gonzo said, this can be quite a risky job as when lifting from the bottom unless you have some control over air pressure what you are lifting will increase in speed as it nears the surface. Divers have to release pressure in their buoyancy jackets to control their ascent. So to bring something to the surface slowly as Par suggested air pressure control is required.

    Also sunken objects don't always surface straight up. Just like a leaf falling to the ground floats sideways, when an object comes to the surface it can suddenly go sideways and can hit the boat that is providing assistance.

    Also any drums used to raise the craft will need a pressure relief valve as the air inside the drums will expand nearly 4 times the pressure pumped in at 11 metres. You of course have a hole at the bottom of the drum if you know which way it is going to float.

    May I make a suggestion. Rather than try and float it up, make a barge of 205 litre drums. Every drum (semi submerged) will lift 100kgs. Lash the drums to beams wood beams are OK with truck tie down ratchet straps. Attach a winch at the centre of the barge, a boat winch would do (check the load capacity). A diver attaches the wire rope to the boat to a sling and I would suggest, wrap it around the engine as the boat does not need to be raised horizontally and around the engine gives a positive hold rather than around the bottom of a boat that may slip.

    Tow the boat to shallow water, and then you can attach ropes to the boat to get horizontal and tow it to a boat ramp.

    Disassemble the raft by unclipping the ratchets and keep them for next time.:D

    Poida
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like a job for experienced people, if it isn't worth enough to justify professional salvage, it is not worth recovery. Even if restored to use, you'll have some residual fear it can happen again. You were lucky the first time. I wouldn't give it a chance to repeat the dose !
     
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