Mic wrote:
I am aware of "the forces that (can) act on boats at sea". I readily
can not give you the ref. for the following, but am willing to accept
them as reasonable:

It would seem that you aren't really aware ...


It was stated that about 93% of the time the winds are between 13-17
knots and for the remaining 7% of the time - 97% of that time they are
between 17-21 knots.


It may have been "stated" but that doesn't make it true or meaningful.

First of all, the "average" wind varies a fair amount by location and
season, so any statistical claim such as that is just nonsense. In
Boston, for example, these numbers hold for July, the calmest month.
But in May and September there are numerous "average wind"
observations over 25 knots. Boston is somewhat windier than most
cities, but it is fairly representative of the New England coast. The
trades can be even windier.

And the "average wind" is meaningless when evaluating stresses on a
dodger or other accessories; it is the gusts that are significant.
Here the "93% point" in May and Sept is up around 23 knots, and 2% of
the gusts are over 30 knots.

In fact, if you just look at the record gusts, you'll find that most
cities in the US have had high gusts (over 40 knots) in almost every
month of the year. Thus, any permanently rigged dodger has to be able
handle that. My standard is 50 knots - that is, when I leave the boat
unattended, I assume that it can withstand gusts up to about 50 knots.
Above that point, I might consider adding docklines or removing
canvas. Designing something to "average winds" is silly.



Its not the wind (for the most part) that does damage it the waves, as
you suggest.

Actually, for the case of a dodger, its probably your brother-in-law
falling into it that you have to worry about. The frame should be at
least strong enough to hold a person; ideally it should be able to
withstand a person falling heavily against it.



I can not reasonably recall the force of a breaking wave on the deck
of a boat but I do recall I was amazed at figure of that force.

If you are on the wrong side of a "plunging breaker" your dodger is
the least of your worries ...

....


The copper tube support that "Walt" designed is interesting, but when
compared to the commercial vanes it is rather "light". I do believe
he said it survived 20 knot situations.

20 knots? What's the point? Self steering should be bulletproof,
not good enough for a daysail.



I have researched virtually all the sailing homebrew material
available:

....

The common aspect of of most of the "home brew" techniques is that
they have been proven worthless. For example, how many home built
ferro-cement boats are still sailing? Home many blue poly sails do
you see?

There are a few notable exceptions, but most of the home brew building
materials are junk. Why don't you see blue poly dodgers? Because
most people understand that the materials are only about 20% of the
value of the project. Most of the value is in the craft of assembly
and finish. Why would anyone use third rate materials for something
that takes a lot of manual labor?

My oldest sailing friends have cruised aboard for many years on a low
budget. Their current boat has probably tripled in value under their
careful restoration. They've done all their own canvas (and much of
mine), much of their rigging, replaced the engine and most
mechanicals, added wind and solar power, many, many, coats of varnish.
And one thing that stands out is that most of their work looks like
it was done by a professional shipyard, or better. All of the
materials are exactly what they should be, whether its stainless,
teak, or Sunbrella. I think they did use pvc for one project -
supports for solar panels that are only deployed at anchor - but I'm
guessing that was just a prototype that will soon be replaced by
stainless.