Sea Sled madness. It’s in my brain.

Discussion in 'Fiberglass and Composite Boat Building' started by DogCavalry, Nov 11, 2019.

  1. DogCavalry
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    DogCavalry Senior Member

    Yup
     
  2. baeckmo
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    baeckmo Hydrodynamics

    You must understand the engineering basics of screws and nuts and what keeps things together. A correct designed bolt connection is held together by the elastic tension in the bolt shaft, combined with the compression of the held material. It can only work loose if there is a rubbing movement, say under the head of the bolt, that causes a loss of tension/compression. That situation always happens when the compressed/tensioned length is small, fi when two thin plates are bolted together; then a thread locking compound will prevent a loose screw to slip away totally. A better way is to use a longer screw and an additional compression collar between screw head and material.

    In the case of this rig extension, you have comparably long tension and compression distances; this combo is completely self-locking. The locking compound is only there to prevent the stud threads in the base material to rotate during fitting and later dismounting, nothing else. As John said; he regards this a permanent setup, then he would be fine with either goo. BUT NO LOCKTITE ON THE NUTS, mind you! And I don't want unhardened locktite to spread between the connection surfaces; that's why I recommended studs to be fitted so that the compound could harden before the extension piece is attached.

    The normal torque setting specified for the standard rig is based on thread size, which remains the same, so: use standard setting, simple as that!
     
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  3. DogCavalry
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    DogCavalry Senior Member

    Screenshot_20230227-163509.png I thought the Evinrude manual would be less ambiguous. But it's unclear here if it's 35-38Nm or 61-68Nm
     
  4. baeckmo
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    baeckmo Hydrodynamics

    I think it's completely clear; at the rear there are two screws in the centerline. The inner one is 61-68 Nm. Also note that for the standard assembly, there is no locking compound specified, but a corrosion stopping grease as explained in my previous note.

    Edit: could it be that there are two versions of the Insex screw (the drawing says Etec_200)? It seems that the one supplied in the kit is the same thread as the others; if so, I would use the lower torque value on that one. And observe that this must be unscrewed when servicing the water pump, so I'd not use loctite on it.
     
    Last edited: Feb 28, 2023
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  5. DogCavalry
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    DogCavalry Senior Member

    Of course.
     
  6. DogCavalry
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    DogCavalry Senior Member

    The stud torques are as @baeckmo observed. Also as he observed, this assembly is self locking, due to the length of the studs and the tension they can maintain. Bay does not recommend loctite.
     
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  7. DogCavalry
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    DogCavalry Senior Member

    Following recommendations from several members, I replaced the plugs in the 250 with cold engine plugs. They aren't fouling so that's good. I'll switch back once we are regularly running hotter. Apparently the new plugs can overheat to the point of causing pre-ignition, so they aren't appropriate for hot running engines. I'm wondering what the cylinders look like inside though. Rings, pistons etc must also be fouled. How problematic is that?
     
  8. baeckmo
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    baeckmo Hydrodynamics

    It's not a problem in general for the rest of the components. The plug's ceramic insulator is the sensitive element; if too cold there will be "tar condensation"; if too hot it will crack. Reason is the fuel/air conditions at flame initiation that are difficult to control. Once the flame is established it is propagating through the gas volume at "designed" speed and temperature as long as the fuel/air ratio is ok.

    At extended operation with severely fuel rich mixture and low load , there may be coke fouling in the exhaust ports. Again, if you "open up" the engine occationally, that won't be any problem.
     
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  9. DogCavalry
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    DogCavalry Senior Member

    That is good news. Thanks @baeckmo .
     
  10. DogCavalry
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    DogCavalry Senior Member

    Another go at the grid IMG_20230312_172145752.jpg
     
  11. bajansailor
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    bajansailor Marine Surveyor

    John, can you explain what you still have to do in the photo above please?
    It is not obvious (to me at least) as to what we are looking at.
     
  12. DogCavalry
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    DogCavalry Senior Member

    Right. The two pilings are completely hollowed out by worms. The large encrusted beam that exits the lower edge of the image was let into the sides of the pilings and held in place with bolts about 75cm long. The smaller beam with the white top surface is one of a pair of transverse beams. When the big longitudinal broke loose it wrenched both crossbeams loose, over a dozen or so tide cycles.

    The cross timber cribs you can see by the pilings will bear the weight of the assembly and boats, since the pilings can't do it anymore. So the massive longitudinal will get lifted back into their notches on the sides of the pilings, while resting on the cribs. I'll lash the longitudinal to the pilings using square lashings. Then we'll lift the cross beams back into place and lash them on as well.

    Then I can get Serenity on the grid, clean a forest of growth off, and extend the leg.
     
  13. DogCavalry
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    DogCavalry Senior Member

    IMG_20230324_180231370.jpg IMG_20230324_180220961.jpg IMG_20230324_171715090_HDR.jpg IMG_20230324_171707183.jpg IMG_20230324_162421997.jpg Like this.
     
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  14. DogCavalry
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    DogCavalry Senior Member

    IMG_20230325_174324292.jpg IMG_20230325_165609788_HDR.jpg
    Should be good for a couple more years.
     
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  15. bajansailor
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    bajansailor Marine Surveyor

    Impressive tidal range that you have there! Especially compared to here, where we have about a metre at the most at spring tides.
    Serenity looks tiny in the background, similarly the wee ally boat.
    Are you confident that the packing pieces / chocks under the poles that are lashed to the piles will stay in place? Do you have significant flow rates of water at spring tides?
    We shall look forward to seeing a photo soon of Serenity sitting proudly on her new grid....... :)
     
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