On Mon, 13 Jun 2005 14:43:30 -0400, Jeff wrote:

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.

The above statement can be said about anthing. But If you take your
own experience and that of others from their logs then come to your
own conclusion on its relative truth or meaningfulness.



First of all, the "average" wind varies a fair amount by location and
season, so any statistical claim such as that is just nonsense.

Yep. The reputation of the tasman sea is an example or the north
atlantic. But the trade winds are different and the pacific "milk
run"...


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.

Interesting link
http://web.usna.navy.mil/~phmiller/usna1.html


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.

Yep, although I have never seen a claim by any maker of tests to and
of their dodgers., why?



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.

Yep, but designed to force 5 huricanes, it that practical or common.



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.

Probably, but I doubt any standard commercial dodger would survive a
200lbs person in all situations without damage.



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 ...

Yep....

...


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 doubt that any of the initial prototype designs qualify the ones
used to cross oceans,
and even some of the current ones in an all bulletproof design.
How many boats have the ready provision for emerg. steering? I only
know of one production boat as such. Why dont they have that, is
almost common sense, (common sense isnt so common:{} )
Most are of a homebrew design. either as foresights or as required.




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?

That is an exception example. I figure the best construction tech. is
the one Glen Ashmore is using, and relative to quality control will be
better than just about any production boat. Homebrew maybe
worthless to some but an inspiration to others, like Hugh Piggots
brake disc wind generator, etc, etc......

Stitch and glue is a homebrew tech. and is accepted as a commonly
acceptable tech. etc.

Home many blue poly sails do
you see?

Well, not many. But they are mostly on 18footer or less. Ususally the
stitch and glue dingys.... but the knowledge and tech. could be
applied in certain situations... an those that have used them would
have spent more on sails than in the construction of their boat.



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?

Yep. This can be applied to production boats. Refer to Bob Pascoe
website.

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.


I have heard and seen many boaters using PVC and blue poly tarps for
their winter covers. Now the tarps may only last a season or two, but
no one, that I know of has had an issue with the PVC supports other
than the tech. they used to secure them to the boat. Some tent poles
are made of fiberglass and it is amazing how much they bend, I haven
seen or heard of one breaking but thats not to say they dont. Look at
the condition on Everest, and the material that are used, sort of like
a fixed sail on land.