Carbon Fiber on hulls

Greetings,
I am refurbishing my Hobie “83” 16 footer. There are a few spots on the bottom of the hulls that need some work. I am thinking about doing something that Jeff MacInnis said that he did with his18 footer that he used to sail the Northwest Passage. http://www.helmdesign.com/polar-01.html

Because the boat was going to be dragged over miles and miles of pack ice and floes he had a strip of Carbon Fiber added to the bottoms of the hulls. I had a an opportunity to sail on that boat with Jeff in January in Georgian Bay after he finished his Passage trip. We dragged the boat a loooong way across the ice that the wind pushes into shore. The ice had a lot of sand and small bits of gravel imbedded into it from the wind blowing debris off the beach. It sure looked like a fast way to wear off the bottom of the boat.

Unfortunately I never really looked at the bottoms to see what the effect of the carbon fiber was, nor did I ever ask Jeff how the had put the carbon fiber on. My experience working with fiberglass is quite limited and I have never laid up anything other than glass.

My questions are these:
In order to keep the keel shape after adding the new material, how much of the keel can be ground off before you get into trouble? How thick is the keel?

Is there any problem mixing glass and carbon fiber in the same structure?

Should I use regular glass lay-up technique or should I vacuum bag it?

I am also considering adding some of West System’s 420 aluminum powder to the last one or two layers of their epoxy. I also thinking about using their 422 Barrier coat additive. Both of these products are know to increase abrasion resistance. The Aluminum is also used to increase hardness and improve its water resistance. It also provides some limited UV protection. The 422 Barrier coat is designed to improve moisture exclusion.

I am looking at the moisture resistance because of an undetectable leak that is allowing water to enter the hull.

This boat had been swept off the beach during a violent Lake Michigan storm (It was anchored by chain to an eight foot long 4X4 post buried in the beach. The storm took the boat, post and about 12 foot of beach)

The boat was found upside down against a steel sea wall. One of the hulls was damaged. The damage included a 2 foot section of the hull wall being depressed to the point that it separated from the deck. The boat was repaired by a marina. They did have to install a small port in the deck to be able to get the hull wall back in place. The inspection port is about 27 inches in front of the front pylon.

When I took the boat out for the first time after repairs it leaked slowly in that hull and the boat capsized. The marina repaired the hull again and it still took on water. I took it to another marina who also fixed it and yet it still took on water.

I have conducted extensive pressurization testing with soapy water. I have repaired a couple of spots where small bubbles formed on the repaired deck/hull joint. I have also patched some gouges in the bottoms of that hull. Non of those appeared to be deep into the keel. No bubbles ever formed on the keels. There was 1 micro leak on one pylon. No leaks detected anywhere else. Drain plug and gudgeon screws are tight, there is no leaks observable in any of the other hardware attachment points.

The hulls are strong and I can detect no soft spots anywhere. Other than some oxidation the hulls look good. The boat is never left in the water. Its either stored on the beach or on the trailer. I’m beginning to wonder if possibly some of the fiberglass or its repairs are porous. Something that might allow water to slowly penetrate but wouldn’t necessarily show bubbles when the hull was pressurized.

Any thoughts on that?
Thanks so much for any input.
Elliott Nelson