[Alberg30] Genoa Travler
Dave Terrell
DTERRELL at message.nmc.edu
Wed Nov 26 10:59:02 PST 2003
What I do may be comparable to "sissy bars" but it really works. I
constructed a bridle in my slip. this is a rope devise that helps catch
the boat as you dock. since I singlehand a lot, this is really helpful.
Other people at the marina must like the idea because bridles are
appearing in a lot of slips now. At the same time I have learned enough
about going slow, etc that I can dock with credibility when out crusing
without the bridle. IMHO ( now that know the phrase), "sissy bars"
strike me as a pretty sane idea in some boats - especially bigger ones.
>>> rkingsland101 at ksba.com 11/25/03 04:59PM >>>
Larry;
Thanks for your "if it ain't broke don't fix it" vote. I will do the
count
when the polls close.
The fact that I have gotten other inquiries like yours below regarding
my
docking technique leads me to wonder if I could better occupy
everyone's
time discussing docking, not toe rails. I have always thought that
one
should hit the dock at an angle of about 30 degrees and only hard
enough to
have the forward end of the boat bounce out enough so the boat drifts
parallel to the dock. If you go too fast the bow will bounce too far
away
from the dock (which is only a problem if you can' get a bow line over
the
piling) and the impact will not be enough to stop the forward momentum
of
the boat (which is only a problem if there is another boat, dingy,
Manatee
and/or a lousy, rotten dock that can't even take the impact of a
little
sailboat without collapsing right in front of your eyes... in the
way).
Perhaps there is a better way I am missing.
Roger
Old, beat up, toe rail-less #148
----- Original Message -----
From: "Larry Morris" <larmor at myexcel.com>
To: "'Alberg 30 public list'" <public-list at alberg30.org>
Sent: Monday, November 24, 2003 1:06 PM
Subject: RE: [Alberg30] Genoa Traveler
> I vote for the ain't broke don't fix it solution. By the way, how
hard
> do you hit your dock anyway? I think if you hit a piling hard enough
to
> dislodge the genoa track or egg shape the bolt holes, you will have
> bigger problems to deal with.
>
>
> Larry Morris
> Solstice #501
>
>
> -----Original Message-----
> From: public-list-bounces at alberg30.org
> [mailto:public-list-bounces at alberg30.org] On Behalf Of Roger L.
> Kingsland
> Sent: Sunday, November 23, 2003 3:42 PM
> To: dk.campbell at sympatico.ca; Alberg 30 public list
> Subject: Re: [Alberg30] Genoa Travler
>
> Don;
>
> To answer your question ("Why would you want to try to weaken the
> attachment point for wind and genoa forces on an AL 30?"), first the
> short
> answer followed by the long answer (for the insomniac Albergers) that
I
> composed some time ago to sort out the issues for myself. Any
feedback
> would be appreciated.
>
> Short Answer:
> I am sure the "if it ain't broke, don't fix it" crowd will point out
the
> thousands of Albergs and other boats of the era having a similar toe
> rail
> detail that haven't sunk yet. But, this detail simply does not stand
up
> to
> the logic test and, in my humble, newbie opinion, it is definitely
> broke.
> The problem is the fastening system requiring great strength and
> rigidity
> (the structural connection between hull and deck) is the wrong type
> (shear
> vs. friction) and is constantly subjected to forces that weaken it
> (bumps
> into the dock and genoa sheet loads).
>
> To me, the solution is to create a good, bonded friction connection
> between
> hull and deck and to separate connections for the loads on the toe
rail
> and
> genoa track. Thus the question about moving the traveler inboard.
> Also,
> the wind load on a 400 square foot sail at 30 knots is under 2,000
> pounds
> (assuming the sail is still intact in such wind), half of which goes
to
> the
> sheet. If the sheet enters the block at 45 degrees, the upward force
on
> the
> track is less than 800 pounds (500 pounds at 30 degrees). It is
> relatively
> easy to distribute with the proper backer plate.
>
> Long Answer:
> I am in the process of replacing my toe rail on #148 and I have the
> impression the rivets were meant primarily to hold the deck and hull
> together during chemical bonding. The rivets, which I drilled out
and
> filled with Marine Tex were too small and too deteriorated to have
any
> appreciable tensile or shear strength and were located near the
outside
> edge
> of the joint overlap where they would not be effective in creating a
> friction connection (but would do a good job of holding the hull and
> deck
> together
> while the joint cured). I replaced them with 3/16" SS rivets 4" OC
> about
> 1-1/2" inboard (my hand still hurts).
>
> The thru bolted toe rail fasteners (3/16" SS bolts, 6" OC) seem to
be
> the
> primary hull/deck mechanical fastener. The problem with these is,
> because
> they also hold the toe rail, they can not be tightened sufficiently
(the
> teak doesn't have sufficient compressive strength) to create a
friction
> connection (like that created by a clamp or Chinese handcuffs) at
the
> intersection of hull and deck. If the chemical bond fails, the only
> remaining bond is the aluminum rivets (which are marginal) and the
shear
> connection created where the SS bolts that pass thru the hull/deck
> material.
>
> A shear connection is only as strong as the surface area that
"pushes"
> against the sides of the connector; in this case, the sides of the
holes
> in
> the hull and deck (each less than 1/2" thick) forced against the
bolt
> shaft.
> Also, unless there are no gaps between the fastener and the
> material being fastened, the shear connection comes into play only
after
> the
> chemical bond fails. So instead of the mechanical fastener adding
to
> the
> strength of the chemical bond, its strength is only realized after
the
> chemical bond
> fails. I suspect the chemical bond is stronger so, if a force
> sufficient
> to break that bond is applied, a second application of the same
force
> would
> also cause failure of the mechanical fasteners. Glug, glug.
>
> Ensuring bolt holes are filled with epoxy (often a messy,
hit-or-miss
> process) or using fully threaded screws would allow both connections
to
> work
> in
> concert but, the limited strength of a mechanical fastener in shear
> would
> still be a problem. A screw with a smooth shaft at the upper of the
two
> layers being fastened will create a friction connection but its
strength
> will be limited the thread grip on the relatively thin lower
material.
>
> The dual function of the fasteners creates another problem. That is
the
> fasteners that hold the hull and deck together also hold the toe
rail
> (AKA,
> bumper) onto the deck. Just a minor bump against a piling can
> cause movement of the bolts which will enlarge the hole through
which
> the
> bolt
> passes (I removed bolts forward that had a lazy "S" shape). In
> addition,
> any eccentric load on the genoa traveler attached to the top of the
rail
> will "work' the thru deck bolts. Close hauled, where loads are
higher
> and
> more longitudinal, the depth of the toe rail will create shear
> resistance.
> When loads are transverse, as in when the sail is out (especially
when
> held
> out by a whisker pole), the thin toe rail does little to prevent
bending
> in
> the bolts which are essentially cantilevered from the deck. I
suspect
> this
> is why we read postings such as this one from George Dinwiddie, "Most
of
> my
> leaks in the lockers under the salon windows have come from leaking
> genoa
> track bolts." The result is water tight integrity becomes entirely
> dependant on the bedding compound (which can also be effected by
> movement in
> the toe rail) and the sheer connection no longer works in concert
with
> the
> chemical bond (per above).
>
>
>
>
> Roger Kingsland
> Chief Financial Officer (AKA, check writer)
> Mahina Manu, A30 #148
> N40° 29.288'
> W79° 54.228'
>
> Author's Disclaimer; This email was produced exclusively by the
sender
> and,
> in the interest of expediency, without the benefit of editing by
others.
> The sender, thank goodness, is a much better architect/sailor than
> speller/editor and, frankly, constantly laments an obvious flaw in
> "spell
> check," it does not know what the author is thinking. Please accept
the
> sender's sincere apologies for any "typos" that may appear in this
> document.
> If present, they are certainly unintended and hopefully do not cloud
the
> message, or spawn any unnecessary lawsuits.
>
> ----- Original Message -----
> From: "Don Campbell" <dk.campbell at sympatico.ca>
> To: "Alberg 30 public list" <public-list at alberg30.org>
> Sent: Sunday, November 23, 2003 11:44 AM
> Subject: Re: [Alberg30] Genoa Travler
>
>
> > The WTC fell when it went out of column and the support was too
weak
> to
> hold the weight due to gravititational forces of the mass. Why would
you
> want to try to weaken the attachment
> > point for wind and genoa forces on an AL 30?
> >
> > "Roger L. Kingsland" wrote:
> >
> > > I have considered moving my genoa traveler inboard about 2" so I
> could
> attach it directly to the deck instead of the toe rail. Would this
be
> permitted under the class racing rules?
> > >
> > > Roger L. Kingsland, AIA
> > > Managing Partner
> > > Kingsland Scott Bauer Associates (KSBA)
> > > N40° 27' 49" W79° 57' 59"
> > > 3441 Butler Street
> > > Pittsburgh, PA 15201
> > > www.ksba.com
> > >
> > > 1(412) 252-1500 X101 - Office & Voice Mail
> > > 1(412) 779-5101 - Mobile (no voice mail)
> > > 1(412) 252-1510 - Fax
> > >
> > >
+---------------------------------------------------------------+
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|
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|
> > >
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