Thanks Clockwork Orange for giving us the benefit of a thorough and (I think) authoritative PoV.
I personally didn't take his statement about endgrain as being likely to apply to EVERY boat ever built, but I would expect reputable builders to comply, along with most disreputable ones. Frankly one's topmast halyards would have to be a few feet short of a full hoist to contemplate using balsa sideways for anything bigger than a scale model, (or a Kon Tiki raft, perhaps, but for a short trip only).
My first contact with balsa was a sickening discovery, when we took apart our first boat in order to put it back together properly*
To our horror, the balsa-cored deck continued under the base of the deck-stepped mast
. It had not been progressively substituted (ie by angled scarfs) with marine
ply, as the design specified. The reason we were suspicious enough to drill a core inspection
hole was that there was fine stress-cracking evident (although not worryingly so, under other circumstances) around the corners of the mast
This was a small boat, but with a tall masthead rig, intended for offshore
Furthermore we'd sailed extensively in very testing conditions, for ten wonderful years -- including one one occasion seas such as I have never encountered since, and never wish to.
When we cut out the offending outer skin, the balsa was still in textbook condition, and had not compressed relative to the unloaded core around it. (There was a mast support pillar, bearing against the underside, only about 2 1/2" square - worse than the mast base in terms of concentrated load - and that had only squashed the core less than 1/16".
We were mightily impressed. I'm not aware of any foam which would have lasted a year in this scenario (of course, we re-engineered the whole setup, nonetheless: It was a crazy omission)
* (lots of work, but well worth doing, because the hull and deck were very well designed and generally well moulded; it had then been put together in another yard, evidently by idiots)
I've since had the pleasure of doing several interesting trips on a racing maxi
which was accidentally overstrong, having been launched about seven tons heavier than the designer
intended (not the builder's fault: it was built exactly to drawings)
The basic structure was a 'boat within a boat'; the interior
was notable for longitudinal walls, effectively girders spanning all the way from turn of the bilge
to deckhead, of 2" thick kevlar over balsa (broken by regular round cornered rectangular openings for pipecots, stacked three high). These were curved only in one direction, and ran from the transom to the bow.
The hull proper was the same materials and scantlings. At the gunwhale, (and, as more usual, around the keel) the balsa feathered away to nothing, so for a considerable distance across the deck and down the topsides, the gunwhales were 2" solid kevlar.
This boat could fall off waves the size of small buildings all day every day, if required. It's the only boat I know which has no detectable reverberation from the hull under such conditions, but you couldn't help feeling a bit sorry for the ocean; at one point the crew nicknamed it the "Urban Wave Destroyer".
For comparison, the boat which beat it, in the round-the-world race
it was built for, wasn't suitable for further duties after the end of the race
, having developed a number of soft spots.
Under subsequent ownership
it was used as a delivery
vessel under charter
to the NZ government
to get scientists and significant amounts of deck cargo (eg building materials) to subantarctic islands, with the blessing of the insurance
companies of both the government
and the owner.
And thirty years on, the hull is still original, and as new.
So I fully concur with Clockwork Orange. It's not all about inherently good or bad materials, it's about inherently good or bad boats.
I would almost extend his claim and say that you could, given sufficient skill, ingenuity and time, build a strong durable boat out of almost any of the recognised boat materials
... and, (at the risk of losing anyone who has read this far without leaving the room) arguably not a few others (eg: papier mache would probably be feasible, given the right resins and some judicious fibre reinforcement. I seem to remember Bernard Moitessier making this claim, come to think of it - and he was a fan of steel)