stripped out screw repair

Discussion in 'Boat Yard Basics' started by lemaymiami, Dec 1, 2012.

  1. lemaymiami

    lemaymiami Well-Known Member

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    It happens all the time... some critical anchor point has a screw fitting fail (particularly when that screw is into a sandwich of glass and structural foam).  Lots of halfway measures will help you re-attach that screw.  The problem is that "halfway" just doesn't last (and if you're on the water day after day...).

    Whenever I can I replace a failed screw with either a through bolted machine screw with fender washers for backing, or failing that a toggle bolt for blind installations (where you can't get to the underside of the fitting.  The only problem with toggle bolts is that you need some room underneath (the blind side) for the toggle to deploy.  Failing that, you've got to get creative.

    Here's something I've used in the past that really works to replace a stripped out screw and it worked great in this instance.  All that's needed is a short piece of wood dowel with a big enough diameter to allow you to drill a hole in the center to accomodate that screw.  In this instance the screw securing my rear pushpole clip was a #14 (pretty large...) so the minimum size for that dowel was 1/2" (I considered using 9/16" or better yet, 5/8" dowel - but the 1/2" should hold just fine...). 

    Here's the technique.... cut the dowel as long as your screw, then center drill it to accept your screw (you want it just a bit tight).  Next, carefully drill a 1/2" hole at right angles into the old screw hole.  You'll know you've done it right if the dowel is a very tight fit...  If there's much moisture in the drilled out screw hole you may want to let it dry for a day or so before the next step, but if it's dry you're in business... Using two ton epoxy or similar two part epoxy glue, coat the screw hole and the dowel (make sure to also coat the inside of the hole in the dowel) then carefully tap it into place, very slightly deeper than the deck surface.  When this step is completed you'll have the dowel in place and every portion of it is coated lightly with epoxy.  Allow to dry for 24 hours and cure out, then simply re-fasten your item with that screw and you're ready to get back on the water...  Here's two pics that show it all...
    [​IMG]

    [​IMG]

    By the way... this same technique can be used to plug an old screw hole as well. For a plug just use the smallest dowel that will fit - after you've drilled out that old screw hole.... Next epoxy it and tap into place, slightly below the surface of the glass.... When it's all cured properly, lightly sand the edges and lay in a just enough gel coat to bring things back to level (done properly you can eliminate a screw hole so effectively that you can't see it was ever there....).
     
  2. Brett

    Brett > PRO STAFF <

    Pretty good Cap'n, better than my counter sunk well nut.
     

  3. jms

    jms don't let common sense get in your way

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    composite cored fiberglass isn't suitable for screwing into - composites will not hold a screw - i've described the correct method a few times

    it's also not a good idea to use those "toggle style bolts" - seen quite a few fail,and fail miseribly

    when working with composites: if you have to fasten something to it - the correct method is to remove the coring in the area where the fastener is to be placed - remove that core,to the inner "skin",fill that area with a thickened epoxy - i like and use west system with the 403 adhesive additive - fill that hole,with this mix - this will hold a screw - example,if you're going to use a 1/4-20 fastener,drill the hole in the epoxy at 3/16,and put a drop of 3m 5200 on the bolt and run it in the hole - it will "thread" the epoxy...

    that's the method to use,when thru bolting and sleeving isn't possible

    common mistake people make is to use a larger screw,after the screw "strips" - this is a bad move,only makes a larger hole.

    the screws strip due to composites being brittle - vibration causes fractures - this creates a loose screw.certain composites "hold" screws - a dense foam,with interlockin fibers,like coosa/penske board,these "hold" much better than divinycell - the cheap crap nida core will hold nothing...

    "hold" meaning,it will stay,however,when pressure is applied,it will pull - this is the reason composites require different techniques...

    epoxy: using a gel coat over epoxy - some epoxies "blush" others do not - "two ton" epoxy is something i've never heard of,not sure if it blushes or not - but,epoxy should be washed with soap and water,before sanding - this removes the blush,acetone will not remove it - using a polyester product over an epoxy product,it dosn't really bond very well.most gel coats are polyester based - you can run into problems,attempting to put a polyester gel coat over epoxy,if certain steps are not taken...
     
  4. DuckNut

    DuckNut Brandon, FL

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    I do it the same as kreepa with one exception. I take a bad allen wrench and cut the short end off a little and put the long end in my drill. Then I insert the short end into the hole and hollow out a cavity between the two fiberglass skins and then fill the cavity.
     
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