Merit 22 Deck Core Replacement: Advice Needed

Thanks in advance for any advice.

I'm attempting to repair the deck core on my Merit 22. The core is very rotten around the bottom side of the port side-stay and inward toward the mast support. Most of the ceiling (cabin top/Deck bottom) has dark colored spider cracks which leads me to believe there may be moisture throughout the core.

The topside looks pretty good, but I anticipate repairing the few spider cracks and fixing hardware fitting sealing/leaks that might have lead to this problem. I don't really want to cut out or repair from the top as it looks pretty good.

I hope/plan to repair from the bottom of the deck by cutting the skin off and scraping/grinding out the old core. I believe the core is probably about 12mm thickness of ply (maybe marine ply maybe not). I measured 15mm with calipers through the bolt hole from some hardware I removed. From looking at a picture of another Merit 22 that was deconstructed I think the core is about 12mm.

I'm inclined to replace the core in as much area as I can in the top with 2 layers of 6mm (1/4") instead of trying to torture 12mm (1/2") to fit. The deck has a slight compound curve. Almost conical, but I think its slightly compound.

Does is make sense for me to use 2 layers of 6mm (1/4") vs 1 layer of 12mm (1/2")?

Is vacuum bagging feasible in this case? I'm toying of the idea of flipping the boat one I remove the retractable keel and all deck hardware. ...hoping that gravity might be more of a friend with the hull flipped. Is this reasonable? The whole boat weighs 2,000lbs. Keel 600. Guessing mast and hardware 200lbs. So I figure I'd have to build a cradle supporting 1,200 lbs.

I'm anticipating using 6oz E Glass and West Systems Epoxy. I have some of the WS manuals and am reading up.

Attached is a pic of a deconstructed Merit22. One Pic shows the core of part of the deck. This part is closer to the toerail than where I'm replacing but I think it's probably a close example of core thickness and construction. It has some voids. My neighbor and I guestimate that just over 2/3 of the thickness is core from the picture. So if I'm measuring 15mm I think replacing with 12mm or 2x6mm with the rest in glass/epoxy it should be OK.

The next pick shows the same Merit 22 with the transom cut off.

Thanks for any advice.

-Derek

 

You might try contacting Mike George at MG Marine (currently building the Martin 242 out in California). Mike worked at Merit and probably knows what was used during the production. Google "MG Marine Martin 242" and you will find him.

 

Paul, Thanks for your advice. Mike responded and was very helpful. He recommended 3/8 ply. Derek

 

Mike is a good guy. We're lucky to have guys like him in the industry.