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Bruce in Bangkok[_16_]

On Sun, 18 Jul 2010 09:38:54 -0400, wrote:

On Sun, 18 Jul 2010 09:42:27 +0700, Bruce in Bangkok
wrote:

On Sat, 17 Jul 2010 19:15:11 -0400, "Wilbur Hubbard"
wrote:

"WaIIy" wrote in message
...
On Sat, 17 Jul 2010 13:43:44 -0400, "Wilbur Hubbard"
wrote:

Now, with the GIP inside as a sleeve and with the boom bales machine
screwed
into the GIP (drilled and tapped into the GIP through the aluminum) the
system is much stronger than it originally was. Replacing the boom with
the
same extrusion would have been just another accident waiting to happen.
This
way the boom is stronger than ever and no hardware hassles such as
locating
another gooseneck and end fitting for a larger extrusion, etc. were
experienced.

You're such a freakin' hammer mechanic.

Simply not so! Like, for example, the aluminum boom extrusion in cross
section is egg shaped. Now how does one fill, strengthen and support an
egg-shaped cross section with a round pipe? Answer: One cannot. So what does
one do? One uses three galvanized pipes. One large one to fit the round end
of the egg shape and two smaller pipes to fit the pointed spaces that
remain. One chooses sizes that fit snugly but don't have to be hammered
home. That's not hammer mechanicing; that's engineering. The three pipes
where coated with slippery silicone rubber sealant before being slid home.

You are correct - it is not "hammer mechanicing" (whatever that is) it
is called, in the trade, "Shade Tree Engineering" and is carried out
by people without a clue as to what they are doing.

You seem to be saying that in order to attach a fitting to an aluminum
boom that, somehow, the boom must be reinforced with internal tubes -
three in your case. Strange that the millions of sail boats presently
on the water all don't have three joints of water pipe stuffed in the
boom. In fact the vast majority have no reinforcement in the boom,
just properly designed fittings bolted to the boom.

If you want some added evidence that aluminum beams do not require
reinforcement with water pipe you might look at the aviation industry.
In the twenty-some years I worked on aircraft I never saw a single
spar or beam with a galvanized pipe reinforcement, and I worked on
some of the more advanced aircraft of that period.

It should be pointed out that Wilbur BROKE his boom by attemting to
install mid-boom sheeting on a rig not strong enough to allow it.

The Coronado has the minimum of everything. It was a price-point boat
aimed at entry level sailors of limited means. Sort of like the Yugo.

Yes, My last sail boat originally had end boom sheeting to a track far
back in the cockpit. Someone, prior to my owning the boat, converted
that to mid-boom sheeting, sheeted to a tack fixed to the cabin top.
All very successfully.

The secret is to (1) have a boom that is adequate to support mid-boom
loads and (2) to adequately space several attaching points along the
mid section of the boom to spread the load over a substantial portion
of the boom rather then concentrating it at one point.

The calculations are relatively simple and specifications for aluminum
tube is easy to acquire so an unsuccessful attempt to change boom
rigging is simply an example of a profound lack of knowledge.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)