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Old 09-07-2017, 09:21   #1
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G10 FR-4 Backing plates

Hi.....

Has anyone used G10 FR-4 sheets for backing plates for U bolts plates for standing rigging,

I was thinking of using the sheets (cut to size) of G10 as a backing plate for my standing rigging also on backing plates for winches and cleats fiberglassed into place

G10 has high strength and is the toughest of the glass fiber resin laminates so it should be able to take the loads plus it comes in various thickness.

Has anyone used G10 FR-4 for backing plates......?

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Old 09-07-2017, 16:16   #2
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Re: G10 FR-4 Backing plates

I've used it for cleats and a backstay chain plate. Haven't rezined them in but probably should have bedded them in thickened epoxy. Seemed to work fine with several thousand miles under the keel.
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Old 09-07-2017, 20:27   #3
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Re: G10 FR-4 Backing plates

Hi Roverhi, thanks for the reply

What thickness did you use ? Was it expensive and how did you cut the material as it's quiet tough on tools, drills, blades etc

Thanks
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Old 09-07-2017, 20:34   #4
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Re: G10 FR-4 Backing plates

I used it for backing some anchors for jack lines. Used thickened epoxy between the plates and the deck. Cut it with a hacksaw or jigsaw. Either way, wear dust mask and goggles.

I bought it precut into rectangles from Jamestown Distributors, but still had to cut it down a bit.
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Old 09-07-2017, 21:07   #5
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Re: G10 FR-4 Backing plates

MarkSF.....

So It would do the job to use G10 FR-4 I taught it would plus it's bounded to the structure with the thickened epoxy

You seen the pictures on my initial post, it's bit crude have you any tips ?
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Old 09-07-2017, 21:37   #6
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Re: G10 FR-4 Backing plates

If I understand you right, you're proposing to anchor your shrouds with ubolts through the deck. This sounds dodgy to me. I doubt if the deck is able to take such loads (or the u bolts....), no matter what the backing plate.

My shrouds are attached to substantial ss bars, that then are through bolted into the sides of the hull, with 4 substantial bolts.

What is the current arrangement, and why do you feel the need to get creative with the design?
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Old 09-07-2017, 22:08   #7
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Re: G10 FR-4 Backing plates

Hi MarkSF......

The boat is old design 1980 Endurance 35 Ketch.....the old insulation had a U bolt threw the deck which is 1/2" fiberglass threw a block of teak about 3" to 4" thick with a back plate of cast iron ( I think)
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Old 09-07-2017, 22:10   #8
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Re: G10 FR-4 Backing plates

Sorry... this set up was common on all Endurance 35 boats.....I've had a surveyor look at the set up and he said that it works, its old school build
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Old 10-07-2017, 03:45   #9
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Re: G10 FR-4 Backing plates

Talking about old school, whats wrong with the time tested use of a stainless steel backing plate?, these epoxy resin formulated sheets are no doubt great stuff to use but in the end they are still that Epoxy resin! -Hard yes! hard enough not to compress or wear under the load of a mast over time?

I have seen this used under winches and other deck fittings or where electrical isolation is required (great for that) but on a dark stormy night 900 miles from the coast !!

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Old 10-07-2017, 03:50   #10
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Re: G10 FR-4 Backing plates

Hi Captsteve53,

Well I was thinking of using both the G10 and also a steel plate as a backing plate !!! Nice and strong install and forget,

I just sent for a quote on a block, if it's a reasonable price I'll go for it.

Also for the windlass as well any area with high loads....modern material has its advantages
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Old 10-07-2017, 04:49   #11
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Re: G10 FR-4 Backing plates

FWIW, I've been on Maxi's where the mast step itself, or step shim plates were made out of G-10. And the downforce on the rigs on such boats well exceeds twice their weight, so...
But unlike metal, it tends to fail with less warning signs. Where metal might first bend, depending on the material type, alloy, & heat treatment. And wood might visibly compress, or show partial thickness cracking, etc. But these are far from absolutes.

In many instances, G-10 is actually stronger, thickness for thickness, than most grades of aluminum. As itís HEAVILY reinforced with glass (or other) cloth, with a fairly low resin content as compared to regular fiberglass & epoxy layups. Even vacuum bagged ones. However, itís not as good as are most metals when it comes to tapping threads into it, at least certain sizes of threads. Larger ones in particular. But there are other ways of securing fasteners to it, needs be.

You do need to know the spec's on the specific piece of G-10 that you're using, since it's physical properties, as with any other material, can vary widely from one brand, or sub-type to the next. For example, Nitronic 50 can be 3-5x stronger than 304/306, & yet they're both "stainless steel".

You can ask the manufacturer for the specís on what they produce. And you can also look it up on Online Materials Information Resource - MatWeb which will also give you POCís on lots of suppliers. Not just for G-10, but most materials.

So to the OPís question. Personally Iíd be averse to bolting chainplates directly to the deck. Though obviously this is a case where one should see the boat. But even then Iíd be leery of doing this. And Iíd think thrice about using just a sheet of ĹĒ G-10 to replace such a thick teak block & metal plate.
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Old 10-07-2017, 06:16   #12
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Re: G10 FR-4 Backing plates

Hi Uncivilized, thanks for the input

My boat is definitely not a Maxi and it probably never exceed 6 knots its Endurance 35 Ketch built in 1980 before the advancements in new materials the G10 will eventually be 2 inches thick with thickened epoxy to hold it in place with a few layers of fiberglass and 1/2 inch steel plate for good measure.

If anyone is interested the spec sheet is

http://www.par-group.co.uk/high-temp...lass-laminate/
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Old 10-07-2017, 06:55   #13
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Re: G10 FR-4 Backing plates

I use G-10 by preference instead of stainless backing plates. In fact I can't remember the last time I used a stainless (really metal) backing plate for any reason. While it does fail differently than metal I can't remember ever seeing a piece damaged from crushing, but I have pulled a lot of rusted stainless plates over the years with corrosion damage.

If you want to tap G-10 you need to use fine threads. And while it is suitable I generally prefer to just use bolts, because I am a little hesitant about how locktite works on g-10/stainless attachments. It may be fine, but I have never tested it or seen testing reports.
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Old 10-07-2017, 07:09   #14
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Re: G10 FR-4 Backing plates

You can find small pieces on EBay and Amazon. I use a carbide table saw blade. Bed with thickened epoxy to it is on a smooth surface. The stuff in a caulking gun cartridge works well.
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Old 10-07-2017, 07:15   #15
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Re: G10 FR-4 Backing plates

Hi Stumble,

What thickness did you use in the areas of standing rigging and how did you install,

With thickened epoxy and fiberglassing over the top of the G10 ?
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