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abrahamx 08-01-2013 10:13 AM

Do I have to predrill before running screws into fiberglass
 
I will be replacing the wood on my boat. The new wood is made up and the old wood is off. I am going to fill the old holes and then install the new wood. Do I have to drill a pilot hole into the fiberglass first? Also if anyone has done this job I will take any other advice before I start.

Tim R. 08-01-2013 10:19 AM

Re: Do I have to predrill before running screws into fiberglass
 
Yes, pre-drill and chamfer the top of the hole so you do not crack the gel-coat.

xort 08-01-2013 10:20 AM

Absolutely. Must predrill. And it has to be a relatively large hole compared to what you can do with wood pilot holes.
Also, after drilling pilot hole, put a small chamfer on the hole to prevent chipping of the glass

abrahamx 08-01-2013 10:31 AM

Re: Do I have to predrill before running screws into fiberglass
 
So I have to chamfer? That sucks. So now I have to line up my hole pattern? I was hoping to go through the wood and glass at the same time. I know from being a metal worker that lining up hole patterns is not easy.

abrahamx 08-01-2013 10:32 AM

Re: Do I have to predrill before running screws into fiberglass
 
what about bedding the wood? Any suggestions on what I should use?

BubbleheadMd 08-01-2013 10:39 AM

Re: Do I have to predrill before running screws into fiberglass
 
Dude, a chamfer (counter-sink) bit is cheap and takes only seconds for each hole.
For bedding deck hardware, butyl tape is the best thing for 99% of applications.

You can buy it from Maine Sail's website: Compass Marine "How To" Articles Photo Gallery by Compass Marine at pbase.com

He sells the best, white butyl tape. A roll will last forever. Proper application is described in text and photos on his website. If you really are in a hurry, you can buy black butyl tape at NAPA as "windshield tape" or windshield sealant.

This stuff is WAY cleaner, and easier to use than 3M 4200/5200, is more effective, and lasts longer.

abrahamx 08-01-2013 10:48 AM

Re: Do I have to predrill before running screws into fiberglass
 
I got free butyl tape at work. thought I read that it was kind of sloppy for doing wood rails. I figured I would just use a larger bit for a chamfer. My point was that I will have to pre drill the holes in the glass in able to chamfer. Meaning I can not just set the wood there and drill through both at the same time. Making it much harder to layout and line up the hole pattern on my wood to the holes in the glass. Unless I am missing something.

jimgo 08-01-2013 10:49 AM

Re: Do I have to predrill before running screws into fiberglass
 
Lining up the holes isn't THAT hard (and I'm lazy):

Drill the holes in the wood.
Put the wood over the fiberglass and tape it in place.
Put a bit in the drill that is the same size as the holes in the wood, so you're using the hole in the wood as a guide.
Slip the bit into the hole and just kiss the surface of the fiberglass.
Repeat for the other holes.
Remove the wood.
Put the proper sized bit in the drill.
Drill the pilot holes at the point where the drill kissed the fiberglass.
Chamfer the edges of the pilot holes.
Put the wood back over the newly drilled and chamfered holes, and add the screws.

abrahamx 08-01-2013 11:11 AM

Re: Do I have to predrill before running screws into fiberglass
 
Thanks. I'm glad I thought of that. Guess thats why they pay you the big bucks. And I'm a metal fabricator for 19 years. To used to measuring everything I guess.

BubbleheadMd 08-01-2013 11:19 AM

Re: Do I have to predrill before running screws into fiberglass
 
Quote:

Originally Posted by jimgo (Post 1067579)
Lining up the holes isn't THAT hard (and I'm lazy):

Drill the holes in the wood.
Put the wood over the fiberglass and tape it in place.
Put a bit in the drill that is the same size as the holes in the wood, so you're using the hole in the wood as a guide.
Slip the bit into the hole and just kiss the surface of the fiberglass.
Repeat for the other holes.
Remove the wood.
Put the proper sized bit in the drill.
Drill the pilot holes at the point where the drill kissed the fiberglass.
Chamfer the edges of the pilot holes.
Put the wood back over the newly drilled and chamfered holes, and add the screws.

Oops, sorry I didn't answer your original question. Yes, this procedure seems fine. Just chamfer the holes, and bed with butyl.

Um... I'm a real stickler about water intrusion and core rot. If this area isn't solid glass, I'd over-drill every one of these holes, fill them with epoxy to seal the wood core, then re-drill them to the proper size for the screws, and bed them with butyl tape.

If the area is solid fiberglass, then just carry on with your procedure.


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