Placing Screws in GRP: advice sought.

[exMaggieDrum]

Be careful here. You can create cracks just as easy with a tap (bottoming or not) if you use one that is not suited for the pilot hole. The times I have used the pilot hole size noted for metals for tapping, it has been too small and the tap cracks the gel coat.

I also concur about 5200 being overused. However, when used on small screws it really doesn't adhere like it does on thicker applications. It does more than 4200 or 4400 though, IME not so much as to prevent getting the screw out in the future. I do like the rubber sealant but I am not sure it is the best for the threads in this case. It will seal the head well. I could be wrong about that but it does not "flow" like the gooier stuff does. I love it for all other sealing jobs.

[PangurBan]

Originally Posted by PangurBan

Again thanks to all fo


Sent from my iPad using Cruisers Sailing Forum

Another slip of the thumb. Again thanks to all for your comments. The problem I have is this. I have to remove a screw that passes through the end stop, an opening in the track and then into the deck. It seems to me that when the screw is replaced it will not fit the previously drilled hole as well as before. Therefore, some kind of filler seems necessary. Maybe I'm wrong about this. I don't need to remove the entire track and so would not have to use a sealant between the track and deck.


Sent from my iPad using Cruisers Sailing Forum

[PangurBan]

Originally Posted by Alan Mighty

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 ).

I like the sound of the Simpson product. I am located on the East coast of Ireland so should not have any trouble sourcing it.
Although I turn 70 this year I am still optimistic enough to want the repair to last more than 10 years🤓🤓🤓


Sent from my iPad using Cruisers Sailing Forum

[Cheechako]

Originally Posted by PangurBan

Another slip of the thumb. Again thanks to all for your comments. The problem I have is this. I have to remove a screw that passes through the end stop, an opening in the track and then into the deck. It seems to me that when the screw is replaced it will not fit the previously drilled hole as well as before. Therefore, some kind of filler seems necessary. Maybe I'm wrong about this. I don't need to remove the entire track and so would not have to use a sealant between the track and deck.


Sent from my iPad using Cruisers Sailing Forum

Is this a screw with a nut or a screw that just is in the glass? A traveler should be bolted with a nut. But maybe just the end cap is screwed in. Don't overthink this, any of the mentioned sealants will work just fine. Just reuse the screw you take out if possible, otherwise get a similar one. Better yet, redrill and put a nut/washer on a machine screw if you can get at the backside.

[minaret]

Originally Posted by Jim Cate

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

Yes, bottoming tap for machine screws, which will have more holding strength than a self tapping wood screw. These don't self tap well in glass. Just drill and tap a hole and watch how much material comes out of the hole when you tap it. It's a lot. Using other methods, there is nowhere for this material to go in a blind hole. This is why it often results in little cracks in the glass radiating from fastener holes down the road. Tap carefully and back a lot, then vac and blow the holes out thoroughly so there's no material trapped in them, and your fasteners will screw in perfectly by hand with just enough room for sealer on the thread, better hold, and no stress on the surrounding material. Bottoming tap for machine screws, regular tap for regular screws. This method also makes it easier to tap your holes so that the screw heads all align perfectly. Parallel to the hardware edge for slotted, row of crosses for Phillips, etc.



To the OP, again, use 4000UV to bed on your end cap.

[reed1v]

I hope you meant nuts and bolts and not really screws. Fiberglass is not a good material to hold screws, even if you epoxy the hole. The screws will rip out over time. Any fitting into fiberglass should have a backing plate.

[Cadence]

Originally Posted by Privilege

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.

I agree on all accounts. JMHO

[TrentePieds]

Others have queried this but I see no explicit reply to the questions: The "screws" you are talking about - are they really "screws" or are they "bolts".

The two different types of fasteners require different handling. So let's know which kind you are taking about. It sounds to me like the application you are talking about calls for "through bolts", though that may not be what you have.

Bolts always take nuts. Screws sometimes take nuts and sometimes not. So are your fasteners pointy on the business end? Or are they the same diameter all the way from the head to the end?

You'll get better more succinct, less confusing advice if you tell us that :-)

TrentePieds

[PangurBan]

Originally Posted by reed1v

I hope you meant nuts and bolts and not really screws. Fiberglass is not a good material to hold screws, even if you epoxy the hole. The screws will rip out over time. Any fitting into fiberglass should have a backing plate.

The track is bolted on but at either end there is a screw which holds the fixes stoppers. The latter never experience any lateral thrust as there are also plunger type sliding stops on either side of the car to adjust its position


Sent from my iPad using Cruisers Sailing Forum

[reed1v]

Originally Posted by PangurBan

The track is bolted on but at either end there is a screw which holds the fixes stoppers. The latter never experience any lateral thrust as there are also plunger type sliding stops on either side of the car to adjust its position


Sent from my iPad using Cruisers Sailing Forum

Its the vertical pull that will do the fiberglass in. So guess your track never will experience any upward pull? No deck flex? We once jibed in a 12 meter in the bay area and tore out the entire setup. Of course we had to jib in about 40 knot gusts with full main hanging way out to starboard when we did our unplanned jib. For some unknown reason no one lost their heads.

[Idylles15.5]

This is getting way to complicated. The traveler track is thru bolted with machine thread screws unless you bought a snap together boat. Your decorative end caps are not made to stop the traveler car. That''s what the positive stops are for, which should have a spring loaded pin that sets in the traveler track. If your car ever blew these off and got past them your in trouble anyway. The end caps aren't meant to stop the traveler car. They are usually plastic end caps to block off the end of the T track, 1) so nothing slides off by accident if you do forget to set the lock pin, and 2 I would imagine so you don't rip the skin off your bare foot. Put some black 4200 on the screw and be done with it. Usually the caps have a machine thread screw which screws into the end of the aluminum T track itself. If your absolutely worried about the hole in your fiberglass, drill it out with a clean dry drill bit probably 1/8" then vacuum out the dust. Get some 2 oz mat fiberglass, cut it up fine with a pair of scissors and mix it with a little bit of west system then fill the hole with it. Pack it in with a toothpick or small punch. Once it sets, drill it out to the shaft size of the screw and put a little 100% silicone on the screw. You don't need 5200 or epoxy, you'll snap the screw next time you have to get it out.

[exMaggieDrum]

Originally Posted by roverhi

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.

+1 on the countersink. It really helps prevent cracking and does help seal. And butyl is great for this. Good info.

[exMaggieDrum]

Originally Posted by Idylles15.5

This is getting way to complicated. The traveler track is thru bolted with machine thread screws unless you bought a snap together boat. Your decorative end caps are not made to stop the traveler car. That''s what the positive stops are for, which should have a spring loaded pin that sets in the traveler track. If your car ever blew these off and got past them your in trouble anyway. The end caps aren't meant to stop the traveler car. They are usually plastic end caps to block off the end of the T track, 1) so nothing slides off by accident if you do forget to set the lock pin, and 2 I would imagine so you don't rip the skin off your bare foot. Put some black 4200 on the screw and be done with it. Usually the caps have a machine thread screw which screws into the end of the aluminum T track itself. If your absolutely worried about the hole in your fiberglass, drill it out with a clean dry drill bit probably 1/8" then vacuum out the dust. Get some 2 oz mat fiberglass, cut it up fine with a pair of scissors and mix it with a little bit of west system then fill the hole with it. Pack it in with a toothpick or small punch. Once it sets, drill it out to the shaft size of the screw and put a little 100% silicone on the screw. You don't need 5200 or epoxy, you'll snap the screw next time you have to get it out.

Good info here too I have been doing a lot of filling and got some of the West System fillers. The right ones can be used instead of the cutup fiberglass although that would work too.

[thruska]

Originally Posted by exMaggieDrum

Good info here too I have been doing a lot of filling and got some of the West System fillers. The right ones can be used instead of the cutup fiberglass although that would work too.

Agree with using West System. I've used it in most instances . It works. They make small 2 part packages at reasonable prices. Such pkgs make it possible to keep unused portions for future use. If you so desire you can add silica to thicken. It's not that complicated or intimidating. Countersink the holes.
If you don't like this idea use butyl. Be careful not to get the gooey black windshield caulk, it will rue the day.
After you use west system successfully you will sing the praises.

[Reefmagnet]

You can use a couple of matchsticks/toothpicks in an existing flogged out screw hole to allow the original screw to clamp down firmly. Sure. it's cheap and cheery, but it's only a little plastic end cap. Stick a dob of butyl or other sealer under the screw to seal it from water if inclined.