Long-grain balsa core?

[Figment]

I cut the topskin from the delaminated area of the lower coachroof today. I was surprised to find that the balsa core in this area is not end-grain blocks, but 2" wide planks laid longitudinally. Perhaps it was thought at the time that compressive strength was secondary to shear due to the thickness of the top skin.

Is this a common thing for early tritons?

Should I be concerned that the "replaced" area will be of significantly greater stiffness, and create a stress riser within the deck? It's the middle third that is being replaced, the outer areas are dry.

Should I expect that the rest of the decks will be long-grain cored as well?

[JetStream]

There is an interesting item on page 122 in "Heart of Glass" by Dan Spurr, that talks about Pearson being the first to use end grain balsa to stop water migration in the Triton. Everett Pearson says they were using balsa planks 3' long x 2" wide x 1/2" thick and they were getting water migration from leaks at the fittings. When they changed to the end grain, the water stopped migrating. Pearson could probably have had a very strong patent on the use but never filed. 1963-4 was the first use of the end grain. So, it has nothing to do with strength.

[Tim]

Yes, those balsa planks are common to early Tritons, and you'll find them in the sidedecks and foredeck as well. I'm not sure when they switched to the end grain blocks (no one is) but I wouldn't put much stock in any published dates as far as Tritons are concerned, as we've seen how inaccurate those tend to be in so many ways--for every firm date or supposed change, we usually find at least one exception that negates the whole theory. That said, #381 (1963, as far as it's possible to tell) had end grain blocks. Since I didn't open the tops of the decks on #100 before I removed them, I didn't see which type of core was in the old deck; whatever it was, it was mush and completely debonded.

Obviously, end grain balsa alone has never completely stopped the migration of water in any boat. If it had, most of us wouldn't be talking about these recores. The concept of the end grain was that it would stop migration, but the reality is that water is much more insipid, and still manages to get around. Modern end-grain balsa should be a bit stiffer than the planks, but not enough to make any practical difference in your boat, so don't worry about mixing the two, at least in your application.

If you were building an Open 60 using the highest technology possible and under controlled conditions, and relying on the engineering of the ultimate hull material strength so that the bare minimum of material could be used, then such a change of core material properties between sections could possibly make a difference. But in your overbuilt Triton deck, with a thick top skin and plenty of molded form strength, there's no basis for concern.

[Rachel]

Just thought I'd mention that the Triton I almost bought, hull #295 I'm reasonably sure, had end-grain balsa coring.

A previous owner had drilled ~3/4" holes up through the inside skin near the stanchion bases in the anchor locker, V-berth, head, and hanging locker. The core was basically dry, although I was able to pull a bit out with my fingernail. It was end-grain, not laid plank-wise.

The owner said it was a 1961, but I'm thinking more like 1962 or 1963 (he wasn't all that sure - he thought it was a 1969 in the ad). There was a plaque given to the owner by friends on the wall that was dated '63, so it was at least that old.

FWIW --- Rachel

[Figment]

Everett Pearson says they were using balsa planks 3' long x 2" wide x 1/2" thick and they were getting water migration from leaks at the fittings.

Boy, I'll say! From what I could tell, the water entered the core via some poorly installed thru-deck wiring sockets near the base of the mast. The rot extended fore and aft for the full distance of the core, but hadn't made its way very far at all laterally from plank to plank.