Champ, it's your decision and coring foams are the current trend. Your grade will reflect your effort. All three options are viable. Here's a thought - use a section of each material and get back to us in 15 years
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Terry, you're right - composites may prove better long term. Certainly no apology necessary. But at this time I haven't seen any 40 year old foam coring other than in a couple of very heavy Boston Whalers
. Strick mentioned Corecell and indeed that's the coring shizzle as it's even being used as hull coring. Plascore seems to be an exciting product but I don't know much about it. I know honeycombs (hex-cells) have worked for bees for aeons. My contrarian point of view was more aimed at preserving end grain balsa as a very acceptable coring.
I think fg1's point is important. Even the greatest composite advocates will insist on sleeving virtually all modern coring materials, especially foams. This effectively "seals" the deal, even with end grain balsa. Now we can't keep every knucklehead from drilling random holes in their boat, but ...
My 40 year old Seafari balsa is in great shape. My 47 year old 21 balsa has a couple of broad soft spots on the fore deck where the horns were mounted. Island Trader's 21 and mine both came from the frozen tundra of the Great Lakes region so you know freezing expansion of wet wood exacerbated the problem of laminate separation, as did fresh water to the rotting process. The former will likely happen with polyester and many coring foams too. Less likely with epoxy.
In Champ's case its a one-off hardtop with a camber that sheds water and is in the sun and wind all day. He's working for a top grade so you can bet he'll do a top notch job.
Pelican, I get where your coming from but, I think your point is more relevant to a cored hull than a hard top. I know you advocate sleeving for composites, and I'm sure the instructor does, too.
Weight of 12 mm balsa compared to similar thickness foam will be nominal and some foam composites may actually add weight due to greater absorption of resins. I ain't smart enough to do the math.
Anyway, Champ, good luck with the cool project. I look forward to seeing the results.
