"DSK" wrote in message
...
... The end grain isolates moisture instead of wicking it the full length
of the structure.


Maxprop wrote:
That was the theory behind end-grain balsa, but ultimately it didn't
work. Eventually the wood will tranfer water a great distance between
lamina.

Yes, but "eventually" Mt Everest will be reduced to beach sand, too. The
progression of rot is much much slower with end grain core than
encapsulated plywood. I would not call that failure, myself.

Your Mt. Everest analogy is not really appropriate in this case. End-grain
balsa core material will be wet during the reasonable lifespan of the boat,
whereas Mt. Everest may see the nova of our sun before becoming a beach. We
ran a moisture meter over a 22 year old C&C 36, whose topsides and deck are
cored with balsa, and there is considerable water in the deck, and some, if
not a lot, in the topsides near the hull/deck union. The moisture is
significant enough to repeatedly thwart the sale of the boat, as the owner
has discovered. Too bad--the boat is otherwise immaculate, and it's fast.



As for plywood "core" what's the point? Why not get plywood that's strong
enough in the first place, instead of adding a skin of something that is
heavier & not as resilient & will trap water in the wood? Actually, the
one exception is the upper face of a deck. Fiberglass is a lot more
abrasion resistant than wood, and makes a great deck surface.


It's probably not a lot more abrasion resistant than dry teak,

Guess it depends on how you define "a lot" and what kind of abrasion you
expose it to. Fiberglass will basically have almost no wear at all from
foot traffic. Teak will... I know this for a fact, having just removed a
20 year old teak deck.

I'm assuming that you didn't own that teak deck for the past 20 years,
therefore you may not know how it was cared for. Or perhaps you know it was
not cared for correctly. Most people are clueless as to how to care for
teak decking. Many scrub it along the rays with a stiff brush while wet
(disaster), and some sand it repeatedly to reestablish the nice brown teak
color (another disaster). I owned a ketch with a teak deck that had been
properly maintained--washed with TSP and a *string mop*, and rinsed with
brine. The boat was built in 1972, and the deck was perfect, save for a
couple of bungs that had popped and had to be replaced. The yacht
Dorade--the namesake of the famous dorade box and cowl vent--sold a few
years ago, and its original deck was completely replaced. The wood from the
removed deck was in such good shape that much of it was used to re-deck
another boat. Dorade was one of Olin Stephens' most famous designs, built
in 1929.

BTW this teak deck was screwed into balsa core, which had a dessert-plate
sized spots of rot. If it had been plywood, it would all have gone to
mush.

That may be a characteristic of balsa itself, which is generally more
impervious to rot than pine or fir. Being an exotic species, it has
genetically evolved to resist rot, which is ubiquitous in the climate where
it grows.

.... which makes the best non-skid of all IMO.

Disagree, but then that's based on personal experience rather than heeding
the opinions of others. Heresy!

Mine is based upon experience as well. Most people think teak is terrible
underfoot. If I listened to others, I'd probably dislike it too.

.... For those boats with ply decks, many manufacturers covered the decks
with canvas and later Dynel or fiberglass.


I've read the Dynel is supposed to be better, not used it myself.

When applied and painted, Dynel is really no different than cotton canvas.
Being a synthetic fabric, however, it lasts about 5 times longer than
canvas. It is harder to work with, however.


.... Look at an Ericson and you will see core with a flat taper or bevel
in the decks. Some eras of C&C did this as well, but they also put in
plywood or milled PVC blanks in place too for some models in some eras.
So did some other builders.

The older Pacific Seacrafts, sure. The last ones I looked at (2003 & 2004
models) they had deliberately built the boat with glued-in molding &
fabric liners so that you could not see or access any part of the
structure. Frustrating... and suspicious IMHO.

Sorry to hear that. I always thought they were excellent boats, if a bit
diminutive in beam and interior volume for their length. I haven't followed
them since the company was sold, but I suspect PS is facing the same
constraints other builders now face: with rising crude oil prices and
labor costs, builders must cut some corners to keep their boats in their
given price niches.

I should have asked first... you know Pacific Seacraft was bought up by a
conglomerate? Personally I think they're playing the sausage game. Nothing
stays good for long.

See above.


But many builders just toss the core in the mold and slap cloth
over it.

Some layup cloth/roving/matt on the outside and simply chopper the inside.
Did you know that several lamina in the layup schedule of Hallberg Rasseys
are choppered? Disappointed me to learn that.



Those same builders never anticipated being in business years later when
those cores were soaking wet, either.


They might not have thought it made that much difference, and couldn't
afford the labor to do it right anyway.

No doubt there was some builder ignorance involved, but I suspect many of
them knew exactly what would happen. A disgruntled ex-Sea Ray executive
told a SOUNDINGS editor that the company's policy, from the 70s on, is to
use ply in the transoms of their stern drive boats, knowing full well that
it would be soaked and soft in 20-30 years. Planned obsolescense.




Maxprop wrote:

Damned if I can recall what manufacturer did this, but I recall seeing a
boat on which all thru-bolts were first drilled oversize, then filled
with solid resin--epoxy, I presume--and then redrilled to the proper,
smaller diameter.

The problem with this method of repair is that you're cutting away the
strength memeber... the skin. But the epoxy filler is stronger in
compression than the core, so that's good.


You're cutting away such a small diameter of the skin that I think the
result is negligible, especially if the unit of hardware being installed
is quite a bit larger.

That's a good point. If the hardware is a lot larger, or has at least 3
mounting holes, it's probably just fine. I was thinking of single bolt
stuff.

I also drill out areas and fill with epoxy to mount small stuff with
self-tapping screws.


No, but freeze-thaw cycles will still cause progressive delamination if
any water gets into it. And Airex is also weak in compression, thru-bolts
will crush it and cause leaks.


It's surprisingly stiff and rigid. I installed a sheet stopper on the
cabin roof, and I was preparing to route out some of the Airex and
replace it with epoxy and West System's colloidal filler, but the local
glass man told me it wouldn't be necessary with Airex. I couldn't detect
any undue compression when I tightened the fasteners. Of course I bedded
them and the stopper in polysulfide caulk, tightened only slightly until
the caulk had a chance to set up slightly, then tightened it further.


Interesting to see what the results will be. Airex and Divinycell and
Klegecell and there some new German stuff that's supposed to be miraculous
but is tediously expensive are all less supject to compression failure,
and certainly less prone to rot but they are still not strong enough
to have rigging components thru-bolted to it. It may be that the caulk is
resilient enough to keep it watertight anyway, in your application.

Guess I should have explained in more detail: in the case of the sheet
stopper, I mounted a 3/4" teak backing plate and large diameter washers
underneath, and a slightly larger-than-the-stopper 1/2" teak mounting plate
on top.


If you're interested, I can recommend some fairly technical books on
composite aircraft construction, which is what I've been studying because
there aren't any books on fancy composite boat construction. Same stuff,
same issues, though.

Probably too esoteric for my needs, but thanks anyway. While on the
subject, though, I'm surprised that honeycomb aluminum hasn't been utilized
as a core material in boats. Virtually no weight, nothing to wick mositure,
and rigid and crush-proof like a cast iron beam when between laminates. But
I suppose the stuff is really costly. I know it was (is?) used in composite
aircraft construction. There were some skis with it as a core material some
years back, and they were successful, if expensive. It was never picked up
by other manufacturers, however.

..... The real killer of cored structure is lack of maintenance. How long
has it been since all deck fittiings were rebedded? Going on 2 1/2 years
for me, and I'm thinking about doing it again. But then I was raised in
the old school where you do this *every* year.


Then there's the school of thought that if you bed everything in
polyurethane (3M5200, for example) you'll never have to do it again.
That's true, because you'll never be *able* to do it again, and of course
it will leak with time. Terrible idea.


I used to use 5200 for everything, and then of course had to
peel/scrape/wirebrush it off, very tedious. Now I use 4200. And I own
stock in 3M.....

Our ketch had a deck prism through the teak deck right over the head of the
V-berth, and of course it leaked as all deck prisms eventually do. Trying
to remove it proved a bit much for my self control. I probably said a few
things that caused mothers to rush their kids out of the parking lot. But
eventually I found the former owner and asked with what he re-bedded the
damn thing. 5200, of course. 20 hours of hard labor, swearing, and bloody
fingers later it was re-bedded and leak-free. People who bed with
polyurethane should be glued to the mast approximately at the spreaders with
the stuff and left there for the cormorants to roost upon. It's great for
hull to deck bonding, however.


This turned out to be really long, sorry about that. But it's an
important issue. This should have come under the "projects" thread
earlier.


I think some of us enjoy projects of this nature. And some of us are
pedantic enough to want to do it in the best possible technological
manner. Most owners are clueless. ("You mean you have to rebed those
things? What the hell . . .?")


Maybe it is pedantry, but my belief is that it's less work to do things
the right way. Especially if you don't want it to fail at an inconvenient
time.

Another of my theories is that 'if it works, it must have been done
right.' I'd like to see some of Frank's work & learn.

Ditto.

Max