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I stepped on my door hatch while it was locked open and one of the hinges popped the off a pretty clean chunk of fiberglass.  The boat was built in 69 if that impacts how I should go about the repair.

This is my first fiberglass repair and it seems like there’s an epoxy for every job.  
 

Any advice?

 

image.jpg

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you need more than just epoxy, you need to glass in that gap. someone will be along shortly to recommend a glass, but regular west system 105/206 epoxy/hardener will do. the real issue is the prep here. lots of guides at westsystem.com to help you get acquainted with techniques and the prep necessary. 

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Just apply a backing pad of stiff cardboard covered with mylar brown packing to the outside lip. This gives you something to laminate against, and the resin won't stick to the packing tape.

Roughly sand the inside lip either side 2" from the break with 80 grit. 

Add layers of thin glass cloth (9 oz) to rebuild the area. I'm suggesting this because it will be strong and it wets out easily if you are a beginner.

Each layer is only 0.4mm (~1/64") thick so measure thickness of existing lip and at least duplicate it. 

Cut all your pieces of glass ahead of time. It will only take a few oz of epoxy. 

 

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Other option is to bond in a piece of prefabricated glass plate on the inside, at least 100mm wider than the missing area,  that should spread the load a bit better than the original laminate, finish it off with a couple of layers of cloth on the outside. You either need to use vinylester or epoxy, I wouldn’t use polyester on such an old laminate ever. 

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Both Ryley and Major Tom offered up good solutions.  Major Tom’s will get you there faster.  McMaster-Carr will have whatever size plate you need.  G10 is one of the most commonly used types of plate.  

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On 6/21/2020 at 5:05 AM, Major Tom said:

, finish it off with a couple of layers of cloth on the outside

Yeah, but by the time you build up the layers on the outside to get to the original thickness, you're basically doing what I suggested + have to go buy a piece of G10. 

It's a thin locker lid. Don't overthink it.

image.thumb.png.4c23c71a8bb758a632dba0f2309b0de9.png

 

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@Zonker, I like your picture. I was taught to put the biggest piece first, and go progressively smaller to get to the original thickness. is there a rationale for not doing it in that manner and going smaller to bigger instead?

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Actually boatbuilders often use smallest first because intuitively "it seems right."  

Aerospace people use biggest first. 

Reality on this repair is it doesn't matter, but you're totally correct - biggest first is best.  I was lazy in my sketch sorry.

Here is why - if you look at this taken from West System epoxyworks you'll see you don't have all the little discontinuities in the laminate like my 3 minute sketch where I drew littlest first. I should know better.

Fig1-e1494866991471.jpg

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22 hours ago, ryley said:

@Zonker, I like your picture. I was taught to put the biggest piece first, and go progressively smaller to get to the original thickness. is there a rationale for not doing it in that manner and going smaller to bigger instead?

West Systems says largest piece in first because it allows for the highest surface area contact and reduces air bubbles along the edges.

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On 6/22/2020 at 4:59 PM, Zonker said:

...like my 3 minute sketch... 

While on the subject what’d u make that sketch in?  Reminds me of playing CAR BUILDER in 1985 in a good way.

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