[Point] So you built a panel with peat moss for the filler and no surface prep or cleaning.
It took a whole summer. I've replace core from the inside twice. Two half days and back to sailing, if you know your glass work.
I praise your ingenuity, but [Point] I don't believe it's a great answer for any boat that has much value left in it. I wouldn't want to explain it to a buyer. ...
[Rebuttal] I would not say that it had no surface prep any more than an I would say that on an infused boat the glass was not "properly wetted out" because you cannot use a fin roller. The prep was done by removing all moister from the space between the skins, leaving a completely dry lattice. Any "mush" (your term not mine) is dust or a bone dry sponge framework which will be fully wetted out by the infusion resin as it is pulled into every void by the vacuum. "Mush" implies wet which I agree would be a very bad idea. vacuum drying that mush produces dust at the worst and a fully dry lattice framework at the best which is a completely different thing.
If I was to take some actual saturated peat moss and sandwich it between a couple of skins of fiberglass and put it under a 30"/hg vacuum until it has a moister reading of 0% moisture and then infused it with epoxy resin it would make a stronger (although heavier) sandwich laminate than one made with foam core.
[Rebuttal]
The reason that I chose to go this route was BECAUSE the boat has great value for its make, model and year. The open surgery method is sound but at best leaves a major scar in the form of a deck with painted non-skid rather than the factory molded non-skid which prompts any future buyer to ask why it needed to be painted and that is assuming that the open repair was done well.
On my boat there is no scar. The only mark on the boat anywhere is the one 2" long crack in the deck cause by the freezing water inside the sandwich that alerted me to the problem. That was repaired after infusion with color matched gelcoat and a pulled basket-weave rubber mold so it is invisible. The deck is absolutely solid and moister readings in the repaired area are all between 0%-12% on the comparative scale which is low in the green scale and are as low or lower than anywhere on the boat whether cored or solid laminate.
I personally do not like painted non-skid because the surface roughness make it hard to keep clean. I several friends with Kiwi decks and they are always dirty looking even after washing. On my molded basket weave, I buff it every 4-5 years with a light compound and protect it with Woody's Wax and it shines like the day it was pulled from the mold and is a breeze to wash and always looks clean.
As for cost, all-in, this repair cost me $100 for the vacuum pump, $10 for 1/4" tubing and fittings and $30 for the infusion resin. An open repair would have cost far more just in the non-skid paint and I cannot even guess how much the resin, glass and core would cost.
As for time, I had maybe 1 hour per sunny day for 2.5 months which was probably in the range of 30-40 hours in total. In my original post, I mentioned a friend who was doing a traditional "remove and replace" repair to his cabin top at the same time I did mine. I started after him and finished before. He was younger than me and given that he has a 9-5 job had far more time available than I do given that I am sole proprietor of my firm. Had I known about thermostatically control silicone heating matts at the time I probably could have dried out the boat in 1-2 weeks by drying 24-7 with the deck heated to the 80ºC-90ºC used by
Hot Vac.
Different strokes for different folks but I am more than happy with my results.