New Stringers ...Ideas on engine mounting?

Discussion in 'Boat Design' started by phishown, Aug 17, 2013.

  1. phishown
    Joined: Nov 2004
    Posts: 13
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    Location: Mobile ,AL

    phishown Junior Member

    I have recently removed all old stringers and installed new foam stringers with a 1/2" of fiberglass over them. I have considered using 1/2" Lag bolts but is 1/2" thick fiberglass enough to hold down the 1400lb diesel engine? I have enough height out of stringer to cut 4" holes with a hole saw and put backing plates with nuts and bolts holding the engine mounts in. Which would be ideal. My concern is being able to dig out the foam to get to the underside of the stringer for the backing plates to lay flush and pull up tight. I have recently notched a portion of the stringer and I dont see how you can separate the foam from the fiberglass easily. I used polyester resin and divinycell foam. Any ideas would be appreciated.

  2. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    A long " L" angle of steel or a hat section of steel can be used. Bed them in epoxy and mechanically fasten

    Spread the load from the engine mounts over a large surface area .

    If this is a high speed craft consult an engineer.
  3. WestVanHan
    Joined: Aug 2009
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    Location: Vancouver

    WestVanHan Not a Senior Member

    My way of doing things-if I'm not sure,pay someone to either do it or guide me.

    Imagine the torque from the engine ripping the mounts out,punching a whole in the bottom and sinking-I know someone this happened to,luckily no one drowned,but it was a close call.
  4. keysdisease
    Joined: Mar 2006
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    Location: South Florida USA

    keysdisease Senior Member

    What Michael said. I like an upside down U channel. Simple, easy, clean, correct. ;)
  5. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    If a long heavy gear like a BW is used I think putting the aft mounts on the gearbox makes the mount loading much more equal.

    You are in a position to provide for that most easily now.

    There is (as I recall) a machined face and drilled/tapped holes on the side on the BW gear for the engine mounts.

    I did this on my boat.

  6. phishown
    Joined: Nov 2004
    Posts: 13
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    Location: Mobile ,AL

    phishown Junior Member

    I think I will go with 4" angle iron laid directly on the stringers and side bolted throughthe stringers with 1/2" bolts and backing plates made of 1/2" kevlar.

    I will post pics in the next couple of weeks when install is complete. Thanks for your replys.

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