I have been involved in a project to develope non destructive testing equiptment for marine surveyors for the last several years. I also have surveyed over 200 hurricane damaged boats in the last 18 months. I have also been involved in construction of balsa cored boats in the past. I was on board a balsa cored sail boat which hit a container in 8 foot seas and 50 knots of wind off Baja during a race. Any normal laminated boat would have sunk. This perticular boat is made of 3" x 3" balsa planks, fiberglassed inside and out. It has made two circumnavigations and over 200,000 miles at sea in its 30 years. Even hitting the container, the hull was not breached--the balsa absorbed the shock.
With that background, I can say that balsa coring properly used, is an excellent product. As DrJohn said the balsa is end grain, and well sealed. Each cell is sealed. Balsa is actually classified as a hard wood because of its cell structure (even though it is one of the softest woods to mechanical compression). The balsa is there to give stiffness--which is essentail in a semi dory hull form. It does this with a very light hull. It is the sandwich which gives the strength. Also, the hull bottom is very thick--there are adequate layers of matt and roving outside of the balsa to make it resistant to impact.
We cut up 20 hurricane damaged boats about 6 months ago. Included in these were boats will all types of cores--including a number which used balsa. Even the balsa which had been exposed to the weather in the year after the damage from being impailed on a piling etc--did not have significant moisture migration. The destructive testing and macro photographs did not show any delamination of the balsa core--I could not say this with either foam or plywood cores.
As for a new vs used boat. I am buying a new Tom Cat 255, only because there aren't any used ones. I have absolutely no reservation buying a used C Dory...for significant savings. Worse case scenerio, you do a little gel coat repair and repaint the color--these boats are built like tanks....
The buyer of my 22 Cruiser E mailed today, saying that NADA shows only a mid 7K figure for the 1992 C Dory. In fact if you put in the "extras" like engines, trailer, custom covers etc, the "value" is closer to 16K---not including the Wallas stove and opening windows etc--which if factored in would bring the value up another few thousand. The bottom line, is look at some 20+ year old XXXX brand and compare the structural condition and what it looks like in comparison to what a new boat of the same manufacture looks like--there is no comparison with the C Dory winning hands down!
Yes, I am biased. I have been in love with the C Dory for almost 30 years, even though I owned a number of boats between the time I first saw one and now. The C Dory just didn't seem right for our travels in crossing the Atlantic and Pacific oceans etc...but I guess some day someone may take that trip! Why not--start at St John's New Foundland....
Regards,