Adventure hatch problem

[DennisG01]

THanks, Dennis. The hatch itself is fine. There’s no bad core. The only damage is what’s shown in the photos above, and it doesn't extend past where the gelcoat is chipped. I may just apply the epoxy to the back side for strength and Spectrum color get coat to the front side, and with a little heat that may be all I need. From what I recall, West System mixes up pretty thin by itself without adding any thickeners, so I may not need to do anything.

The existing gel coat on the outside edge is probably 10 or 11 mils thick, so I think my biggest concern is getting a good bond with the resin underneath so it doesn't flake off.

I was thinking more about the OP's hatch in my response.

But looking at your pictures, one thing I notice right away is how crisp the bottom edge is. Hard/crisp edges like that tend to make chipping like you have even more likely. That bottom edge should be slightly rounded.

You'll need to (best practice) grind away some of the gelcoat where the chipping stops. This is to ensure that there's nothing loose there and also for better adhesion in the repair.

 

[seasick]

Be careful with gelcoat - the thicker it is applied, the more brittle it becomes. However, you could tint the epoxy or poly resin.

Heat the hatch up in the oven or with a heat gun. When the resin is applied, it will thin out and be absorbed further into the core. But if you're digging out the bad core and filling with structural epoxy/poly resin, that will be more than sufficient as is.

Dennis, you were right on as usual. I did some research on thinning epoxies and found this statement ;
Thinning With Heat

Not as popular as thinning with solvent but still a very effective method of maintaining most of the strength characteristics in the epoxy. This process is accomplished by applying heat to the surface or the epoxy directly before applying the epoxy to your finished product. Heating the resin will drastically thin the epoxy down to a level that becomes more usable and main almost all of the physical traits of the epoxy.

I am going to keep that idea in my bag of tricks.

 

[DennisG01]

Thanks, Seasick!

One thing I would add to the info you found is in regard to heating the actual epoxy. While it can help to warm the epoxy by bringing it inside the house, heating it up too much can drastically affect the cure rate and it can start to "kick" too soon. Heating the material to be epoxied will have less affect on that.

 

[seasick]

Thanks, Seasick!

One thing I would add to the info you found is in regard to heating the actual epoxy. While it can help to warm the epoxy by bringing it inside the house, heating it up too much can drastically affect the cure rate and it can start to "kick" too soon. Heating the material to be epoxied will have less affect on that.

I was leaning towards about heating the composite not the epoxy mix.
Another fact I found is that adding 5% acetone to epoxy will reduce its strength by almost a third. That was a surprise to me.

 

[DennisG01]

Another fact I found is that adding 5% acetone to epoxy will reduce its strength by almost a third. That was a surprise to me.

I had always known it would decrease the strength (although in may applications, it's still plenty strong enough... especially given that it's stronger than the polyester or vinylester that our boats are made from). But I had no idea it was that much.