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Thread: Spider cracks along rub rail

  1. #1
    Join Date
    Sep 2006
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    Default Spider cracks along rub rail

    Recently I wastold that if you took a router and ground a line above the screws on the rubrail that this will help reduce the spider cracks along the rub rail. But keep the line under the rub rail..

    Going thru the gel and into the glass!

    I understand that Cobalt does this on all their hulls.

    Has anyone tried this yet?
    AOTH IX/X ZX Peoples Choice award
    2000 28ZX Scorpion.. SOLD
    1986 Z29
    1973 X 18 #61 Project BBC
    1979 Criterion

  2. #2
    Join Date
    Oct 2009
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    NEW HARTFORD, CT
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    Default

    Kinda like drilling a hole at the end of a crack in sheet metal.

    I can see that making sense. If a crack should start at the screw, the crack runs out of material to continue on.

    Ken

  3. #3
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    Default

    I have no idea Mike but that sounds like a GREAT idea .

  4. #4
    Join Date
    Oct 2007
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    New Hampshire
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    643

    Cool

    Id just counter sink the gel away from the screw head with a dulled drill bit, 1- 2 sizes bigger than the screw on an assembled boat. Flexible caulk will fill in the voided gel so it can have a little give when flexed. Its the high degree of brocol hardness + poor flexable modulas of the gel around the screw that starts the cracking. I assume they use a jig on top of a cleaned up hull part, using a high speed router. Id use a Fein saw if I was trying to cut a straight line on something assembled.
    Last edited by MIKEO; 06-02-2012 at 12:23 PM.

  5. #5
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    Jul 2009
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    Huntingdon Valley PA
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    Default

    I would think that IF you want to do this ~~~all you would really need to do is make a very fine saw kerf cut , or small router bit slice, just through the gellcoat to the very top of the fiberglass layer,
    No real need to actually cut into the under layer of glass itself.

    I actually like the idea of grinding a small 1/4"-5/16 "circle, or countersink hole, around each drilled rubrail screw hole in the gell itself much better.

    As we all know gell is very brittle , and stress cracks very easily.

    I once had a 1970 23' foot Chris~Craft Lancer inboard boat with unusually thick 1/4"+ white gell & center blue gell race stripe on it's deck.
    This very thick gellcoat stress cracked all over the place for no apparent reason other than it being just too thick to flex with the hull .
    The thicker the gell~~~the more it will be prone to stress crack .

    I finally rough sanded the entire deck removing much of this gellcoat thickness ,with a small Skill sand-cat belt sander & filled the remaining deeper gell cracks with old Dupont Coralar epoxy primer surfacer; and top spray coated it with white Imron, and blue imron center stripe and quickly sold the boat~~~telling the new owner, a neighbor & friend, about this deck gell cracking issue & repair. He was happy with the "repaired" boat; & the deal.
    I knew this was Not a proper gell stress crack repair method.

    BUT~~~ I still lost my shirt on that Lancer sale !
    I also sprayed that Imrom with a Binks #7 gun with only a twin carbon filter painter's mask.
    I guess I took five years off my life on that imron spray job alone ?

    The boat is still in the water today still owner by my neighbor with this very same Imron job I did years ago~~ with few signs of any deck cracks some 20+ years later.
    That Lancer is now considered a "Classic" and the older owner loves this boat and would Never part with her.
    Last edited by silverghost; 06-02-2012 at 03:07 PM.
    BRAD HUNTER
    Huntingdon Valley Pa (Just outside Philly)
    215 947 4676 Home
    silverghost1926@msn.com

    Donzi 18 "Benchseat 18 Project "Owner

    Chevy 454 SS Tow/Sport Pick-Up

  6. #6
    Join Date
    Jul 2011
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    West Mich
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    Well ....first off........ if you router thru the jell into the glass you actually are taking away the structural intergrity of the layup .....which in reality means you have done nothing to properly repair those cracks listed above which will come back in the long run , and like anything else on a fiberglass boat you will need to properly prep the surface ( grind ) adding a little beef to the area's of concern .....................just my 2 cents which is three cents short of a nickle...........................

  7. #7
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    Default

    Quote Originally Posted by OFFSHORE GINGER View Post
    Well ....first off........ if you router thru the jell into the glass you actually are taking away the structural intergrity of the layup .....which in reality means you have done nothing to properly repair those cracks listed above which will come back in the long run , and like anything else on a fiberglass boat you will need to properly prep the surface ( grind ) adding a little beef to the area's of concern .....................just my 2 cents which is three cents short of a nickle...........................
    Let me toss another penny. this is pre crack.....
    AOTH IX/X ZX Peoples Choice award
    2000 28ZX Scorpion.. SOLD
    1986 Z29
    1973 X 18 #61 Project BBC
    1979 Criterion

  8. #8
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    Default

    Quote Originally Posted by OFFSHORE GINGER View Post
    Well ....first off........ if you router thru the jell into the glass you actually are taking away the structural intergrity of the layup .....
    The gell gives you nothing in the lay-up. Going through a layer of glass does tho, I will give you that.

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