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Author Topic: GRP HULL DRILLING  (Read 1004 times)

Dave Cook

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GRP HULL DRILLING
« on: June 04, 2014, 02:38:41 pm »

Hi All , As anyone got tips on drilling rudder holes and cutting prop shaft slots in a GRP hull without chipping the gell coat .
Cookie  :-) :-) :-)
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Neil

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Re: GRP HULL DRILLING
« Reply #1 on: June 04, 2014, 02:45:26 pm »

depends upon the size of hole you want to drill, dave..........if it's an 8mm hole for a prop shaft.........mask off the area with a masking tape including over the point where you want to drill and drill with a 6mm bit, enlarging the hole to the required size with needle files, or garnet paper( the yellow green or brown hard stuff) rolled into a tight pencil shaped roll...leaving the masking tape on the hull whilst you sand the hole to the right size.............this will elliminate any shattering of the gell coat.

neil.
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deadbeat

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Re: GRP HULL DRILLING
« Reply #2 on: June 04, 2014, 03:08:17 pm »

.....and drill from outside in!
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Neil

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Re: GRP HULL DRILLING
« Reply #3 on: June 04, 2014, 03:24:08 pm »

oh, yeh............forgot to say that, sorry.........goodun deadbeat......just to cover all bases.

neil.
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Dave Cook

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Re: GRP HULL DRILLING
« Reply #4 on: June 06, 2014, 07:23:57 am »

Thanks Lads i, I will give it a go  :-)) :-)) :-)) :-)) :-)) :-))
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CyberBOB

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Re: GRP HULL DRILLING
« Reply #5 on: June 15, 2014, 07:01:25 pm »

I have good success starting from the outside, hss bit, slowly in reverse.  Once you have ground through the gelcoat, stop, put the drill in forward, and finish the hole.  It doesn't work with forstenor, spade or brad point bits though.
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Time Bandit

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Re: GRP HULL DRILLING
« Reply #6 on: June 15, 2014, 08:05:39 pm »

I always use those conic grinding stones for drilling machines to enlarge the hole.
That works pretty perfect.




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regards

Tobias
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