Thanks for that info on Douglas Fir (Oregon) very interesting stuff. Actually Hoop Pine
isn't a pine either but a Southern Hemisphere conifer although it landed that label "pine"
in this part of the world much as Douglas Fir was labeled Oregon Pine.
I was just guessing that Rob's boat is built from Oregon ply, it may be any number of
other timbers I guess, but it looked like Oregon to me - of course it may also be Radiata
--- In Michalak@yahoogroups.com, Chris Crandall <crandall@...> wrote:
> > It would be interesting to know what type of timber the ply that you
> > used is, I used Australian produced Hoop Pine but I can't pick from
> > your photos what yours are. "Pine" of some kind, no doubt. I know
> > that NZ is producing "Oregon" from plantations now so I'm wondering if
> > plywood is being produced from that source now across The Pond?
> Just a note: "Oregon" pine is not pine, it's Douglas Fir, which isn't a
> fir, either, alas. It's a Pseudotsuga (false hemlock) menziesii. It's a
> great tree, grows like a weed and straight, too, and a great wood, for
> dimensional lumber and plywood. Light and strong, and prone to moisture
> cycling (because of the difference is the earlywood and latewood). Many
> people do not like the look of the roto-cut grain (and I pretty much agree).
> Old growth doug-fir is an outstanding boatbuilding wood, works well,
> strong, relatively light, good rot and decay resistance. Newer growth,
> which is what is mostly available and/or affordable, isn't quite as
> good, but it's just fine for what most of us build.
> Because of the moisture cycling, DF plywood checks (small openings
> appear in the face of the plywod) which is ugly, invites more
> cycling/checking, and ultimately rot/decay. This is why DF plywood boats
> are often recommended to be covered with epoxy and glass (or other
> fabric), which inhibits checking. Paint and/or epoxy alone are not
> enough to stop checking.
- As you mentioned, Garth, the offset mast does make the downwind "lever
arm" slightly longer on starboard tack than on port tack. So if you
were to gradually increase other factors that would contribute to
broaching, such as lowering the leeboard, moving weight forward, or
using a smaller rudder blade, I'd expect the effect would exceed the
"broaching threshold" slightly earlier on starboard tack than on port.
I just don't think the "lever arm" on starboard would be extreme
enough to "cause" a broaching problem, if other larger factors weren't
already in play.
Completely raising the leeboard and shifting weight markedly aft would
be easy to test. Heeling the boat to windward would also bring the CE
more directly over the hull. If those things don't cure the problem,
then a larger rudder blade might do it.
--- In Michalak@yahoogroups.com, "GarthAB" <garth@...> wrote:
> I'll have to do some controlled experiments this summer and report
> back. You'd think that if weight forward were the problem, or rudder
> stall were the problem, it would manifest itself equally on port and
> starboard tack while running. But my impression was that this problem
> surfaced only with the sail full out on the port side. But my
> scientific sample may have been too small.