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Old 16-01-2016, 08:54   #1
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Placing Screws in GRP: advice sought.

I plan on replacing the end stops on the mainsheet traveller track which is attached to a bridgedeck aft of the companionway. What sealer or filler should be used to accept the new screws? Are there any pitfalls or nasty surprises that I should be aware of?
I would be very grateful for any advice.


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Old 16-01-2016, 09:22   #2
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Re: Placing Screws in GRP: advice sought.

Most any good sealant will work, 5200, 4200, life caulk etc.
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Old 16-01-2016, 11:24   #3
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Re: Placing Screws in GRP: advice sought.

+1 what Cheechako said. The most important thing that I learned the hard way is to not drill the holes too small for the screws - they will snap off easily if you do. I have done it many times and I really pay attention. You will need a bigger hole than you would use for softer, more forgiving, material like wood. You certainly don't want to match the size of the screw shaft as that would be way too small. Slightly smaller than the threads is all you want. It is a nasty job getting out broken screws.
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Old 16-01-2016, 11:24   #4
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Re: Placing Screws in GRP: advice sought.

The gel coat and fiberglass is very hard. If you don't drill a proper pilot hole, your stainless screw will shear and most of your time will be spent trying to get it back out. Make sure that the pilot hole is at least the width of the screw shank leaving just the threaded part to do their thing. If you can bolt it, espacially for a traveller, then do so. 5200 is always the sealant adhesive of choice. 4200 if no adhesion is needed.
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Old 16-01-2016, 12:00   #5
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Re: Placing Screws in GRP: advice sought.

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The gel coat and fiberglass is very hard. If you don't drill a proper pilot hole, your stainless screw will shear and most of your time will be spent trying to get it back out. Make sure that the pilot hole is at least the width of the screw shank leaving just the threaded part to do their thing. If you can bolt it, espacially for a traveller, then do so. 5200 is always the sealant adhesive of choice. 4200 if no adhesion is needed.

Thank you, Cheechako, exMaggieDrum and Privilege. Your advice and insights are much appreciated. I will not be drilling new holes but merely replacing the screws in the existing ones after fitting the stops. Before resetting the screws should I wait until the 5200 hardens or put the screws in and allow the sealant to cure around them?


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Old 16-01-2016, 14:10   #6
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Re: Placing Screws in GRP: advice sought.

Warning: contrarian point of view coming.

5200 is Satan's Glue.

You need a sealant, not an adhesive.

Find Maine Sail's Bed-It-with-Buytl.

Re-Bedding Deck Hardware With Bed-It Butyl Tape Photo Gallery by Compass Marine How To at pbase.com

***Buy Bed-It Butyl Tape*** Photo Gallery by Compass Marine How To at pbase.com
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Old 16-01-2016, 15:04   #7
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Re: Placing Screws in GRP: advice sought.

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5200 is Satan's Glue.
That is a tad too dramatic. But I agree, butyl rubber would be a better choice.
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Old 16-01-2016, 17:21   #8
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Re: Placing Screws in GRP: advice sought.

Quote:
Originally Posted by Stu Jackson View Post
Warning: contrarian point of view coming.

5200 is Satan's Glue.

You need a sealant, not an adhesive.

Find Maine Sail's Bed-It-with-Buytl.

Re-Bedding Deck Hardware With Bed-It Butyl Tape Photo Gallery by Compass Marine How To at pbase.com

***Buy Bed-It Butyl Tape*** Photo Gallery by Compass Marine How To at pbase.com
+100!

5200 is WAY over used and for the wrong purposes.

There, hows that for drama.
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Old 16-01-2016, 21:02   #9
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Re: Placing Screws in GRP: advice sought.

Bevel the edge of the screw puka with a countersink. That makes a little pool of caulk that will absorb any movement of the fastener and not break the sealant bond between the deck and fastener. As far as caulk like LifeCaulk or butyl.
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Old 16-01-2016, 21:12   #10
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Re: Placing Screws in GRP: advice sought.

I think you need an adhesive-sealant, one that adheres to both the fastener (your screw or bolt) and the matrix (the GRP and the fitting i.e. the traveller track, cleat, etc).

Depending on your context - meaning your geography and where the fitting is located - I think you have to consider environmental exposure (UV, temperature). Bedding compounds, whether butyl rubber or 3M's 5200, all age. UV and heat accelerate the speed they age.


Depending on temperature (decks and deck fittings get hot), 5200 has an age limit - based on my need to rebed deck cleats, my experience points to an average somewhere between 5 and 10 years.


Technology keeps doing a better job. In the 18th century, Stockholm tar was cutting edge. In the 1950s, Dolfinite was cutting edge. Both work, but there are better products available.


I would suggest you spurn both 5200 and butyl rubber as obsolete. Both work, but there are better products available. And of course not everyone has caught up with the latest.


I think the current best technology has surpassed them in the form of silyl-modified polymers (SMP). No doubt SMP bedding compounds will be surpassed soon. But not yet.


For brand names, look at Simson ISR 70-03 or Simson MSR (ISR = industrial special range; MSR = marine special range; a chief difference is that MSR has International Maritime Organization rating for being non-flammable).


Simson is a brand name belonging to Bostik.


Try your preferred search engine or see:


* For MSR: Products -> Transportation -> Marine -> Simson MSR Deck Caulk


* For ISR 70-03:
Bostik Australia :Industry - Catalogue - Simson ISR 70-03


Depending on the economy in which you're located, you likely will not find these products at your corner store.


Bostik Simson targets 'the trade', not retail consumers. Internet retailers (eBay etc) may provide. For ISR 70-03, look for auto windscreen repairers/replacers, because Simson ISR 70-03 is the adhesive-sealant of choice (remember the point about temperature? Windscreens get even hotter than deck fittings left in the sun).


Simson MSR was patented as a bedding compound for teak decks (which should also tell you something about its properties as a sealant and adhesive coping with UV and a wide temperature range while staying elastic) - see attached patent US 7581505 (about 500 KB ).
Attached Files
File Type: pdf US7581505o.pdf (505.0 KB, 32 views)
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Old 16-01-2016, 22:04   #11
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Re: Placing Screws in GRP: advice sought.

Butyl is my weapon of choice. 5200 in a great adhesive sometimes too good. If you had to take them off this time, you may have to take them off again. Trick to Butyl is to tighten three times letting a day pass between each tightening. It sounds like more work, but worth the extra effort. A plastic credit type card or plastic putty knife works good for cleaning off the overflow.
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Old 16-01-2016, 22:42   #12
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Re: Placing Screws in GRP: advice sought.

Good advice above. - HOWEVER: (if a cored structure)
I prefer to drill oversize through the outer skin, use a keyhole cutter on a router to remove a bit more of the core between the outer skin and inner skin. Fill with Marine Tex or other structural epoxy. This lets the screw be installed with or without sealant and the core is protected.
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Old 16-01-2016, 22:49   #13
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Re: Placing Screws in GRP: advice sought.

Ancient materials on order here. Use 4000UV instead of 4200 or LifeCaulk. It's newer and better.


For fastening in glass, I always use a bottoming tap first. This allows you to use a smaller pilot for better grab, and also prevents the cracks you can get radiating from a fastener even if you use an oversize pilot, a year or two down the road.
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Old 17-01-2016, 03:17   #14
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Re: Placing Screws in GRP: advice sought.

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Ancient materials on order here. Use 4000UV instead of 4200 or LifeCaulk. It's newer and better.


For fastening in glass, I always use a bottoming tap first. This allows you to use a smaller pilot for better grab, and also prevents the cracks you can get radiating from a fastener even if you use an oversize pilot, a year or two down the road.
Minaret, what sort of screws are you talking about here? Sounds like normal machine screws, and I thought that the OP was talking about self tappers.

Perhaps I am confused... wouldn't be the first time!

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Old 17-01-2016, 03:29   #15
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Re: Placing Screws in GRP: advice sought.

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Minaret, what sort of screws are you talking about here? Sounds like normal machine screws, and I thought that the OP was talking about self tappers.



Perhaps I am confused... wouldn't be the first time!



Jim

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