[Public-list] Chainplate covers?

sousa, stephen (ENG) sousa_stephen at emc.com
Thu Dec 16 05:07:20 PST 2004 

Roger,

I am not sure if other members see it this way. If we have one good solution
out of ten ideas, it may be worth reading through some of your thoughts.
When I looked at your design, it is similar to what O'Day used on smaller
boats in the 70's. They also water intrusion issues under the chainplates. 

I am more concerned about the attachment points, if the current design bends
1/4 inch bolts, I wouldn't trust two attachment point in the area I sail
which is off shore. 

I plan on buying some chainplate covers to extend the life of the sealant,
it seems they reduce the UV damage and provide a finished look.

Have a nice holiday.

Stephen
 

-----Original Message-----
From: public-list-bounces at alberg30.org
[mailto:public-list-bounces at alberg30.org] On Behalf Of Roger L Kingsland
Sent: Thursday, December 16, 2004 7:54 AM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-list] Chainplate covers?

Mike,

I would be happy to comply, but I'm not sure I am the right guy to be asking
for forgiveness.  I throw this stuff out expecting constructive criticism,
understanding "the page" isn't exactly a bastion of new ideas.  Everyone's
feedback, even if negative, is greatly appreciated.  Your only comment I
take issue with is the reference to time and expense.  Hell, if saving  time
and expense were a priority, we wouldn't all be so content throwing money
(and time) into a hole in the water surrounded by fiberglass.

Roger

----- Original Message ----- 
From: "Mike Lehman" <sail_505 at hotmail.com>
To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
Sent: Wednesday, December 15, 2004 5:51 PM
Subject: Re: [Public-list] Chainplate covers?


> Forgive me, Roger, but it seems like a lot of time [and expense] for
> something that only takes a few minutes each year [re-caulking the
> chainplates]. Hell, in the time we spent sending a replying to these
emails,
> we could have caulked our chainplates. This is not a weak point in the A30
> construction; it is a proven method for attaching shrouds; it has
withstood
> the test of time and severe stress and it only becomes vulnerable through
> owner neglect [because the owner let water saturate and damage the
bulkhead
> because they did not maintain the boat properly].
>
> Mike Lehman
>  ><((((º>¸.·´¯`·...¸><((((º>
>
>
> ----- Original Message ----- 
> From: "Roger L Kingsland" <rkingsland101 at ksba.com>
> To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
> Sent: Wednesday, December 15, 2004 5:11 PM
> Subject: Re: [Public-list] Chainplate covers?
>
>
> Mike,
>
> Thanks for your reply.  I understand all the flexibility stuff relative to
> building structural design where the connections are rigid but the
remainder
> of the structure is flexible.  Without springs, shock absorbers or other
> gizmos that I haven't seen on stay connections, I would argue it is not
> possible to make a "flexible" connection with a point load such as a stay.
> To me the flexibility issue is how the load is distributed through
flexible
> materials "downstream" of the rigid point load connection.  That's where
the
> flexibility of the diaphragms (hull, deck, bulkheads) comes into play.  I
> hope everyone agrees the factory connection must be rigid by the time it
> reaches the upper bulkhead bolt; otherwise the bolts would work causing
> eventual failure.  I am assuming (I hope, correctly) that my detail simply
> moves the point where everything is rigid up about 2".
>
> With my detail, once the rigid connection to the bulkhead is achieved,
there
> will be no load on the deck unless A), the bulkhead connection fails; or
B),
> there is flex in the 90 degree bend at the top of the chain plate.  The
> latter is prevented through a simple structural calculation to confirm
> sufficient thickness (that I hope to cajole one of our structural
> consultants into doing).  Basically, if the chain plate can't slide up the
> bulkhead and the bulkhead does not move vertically, the portion against
the
> bottom of the deck will not apply any upward force.
>
> To me the issue is weather adding a 3" length of the deck to the rigid
> portion of the connection will cause cracking or will the remaining 30+
feet
> be able to take up the flex lost under the new deck plate.  If the former
> were the case, other areas with rigid plates (mast step, stanchion bases,
> bow bracket, mainsheet traveler) would have similar problems.
>
> One other consideration is that the "free" portion of the plate (area
> between top bulkhead bolt and turnbuckle connection) on the factory detail
> might function as some form of shock absorber necessary to absorb the
slight
> (probably under 1,000 pounds) eccentric load caused by the inward angle of
> the stays which pulls the whole mess toward the mast.  If this is the
case,
> extending the vertical tab welded to the deck plate a few inches will have
> the same effect.
>
> Relative to Alberg/Whitby compromises (IE, design intent), I am sure
> economics of a production boat in competition with Pearson came into play.
> I am willing to invest the time to make improvements to those compromises
> but have been careful not to change anything made an effort not to change
> the basic structural flexibility.  For reasons stated above, I don't think
> the detail is a "significant structural modification;" however, Mike
> Lehman's comment that he has never seen it done this way certainly argues
> for additional research.
>
> Thanks everyone for the valued feedback.  Off I go to ponder further.
>
> Roger Kingsland
>
> ----- Original Message ----- 
> From: "Meinhold, Michael J" <MICHAEL.J.MEINHOLD at saic.com>
> To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
> Sent: Wednesday, December 15, 2004 2:56 PM
> Subject: RE: [Public-list] Chainplate covers?
>
>
> > Roger -
> >   I hope that before you make a significant structural modification you
> > understand why Alberg/Whitby chose the system and made the compromises
> > they
> > made (I can't say that I can identify all the reasons). I agree with
Mike
> > Lehman in that a good general principle in ship design is flexibility,
not
> > rigidity. What flexibility implies is distribution of load and both over
> > time and space.
> >
> > You need to carefully consider the path of the load is being carried .
In
> > your new joint, the load is carried by the threads of your acorn nuts.
It
> > then transfers to the vertical bolts and your L-Bracket. From there it's
> > partly transferred to the bulkhead and partly to the deck, depending on
> > how
> > the whole arrangement is tightened up.
> >
> > In the directly connected chainplates the chain plates transfer the load
> > to
> > the bulkhead partly through shear between themselves and the bulkhead,
and
> > partly to the bolts and then the bulkhead. No load is carried by the
deck.
> > I believe it would be a mistake to use the deck to carry any large
> > vertical
> > load.
> >
> > As Mike says, most of the time it wouldn't matter, but under trying
> > conditions the loads are going to approach the breaking strength of the
> > wire. I would say you want the wire to fail first!
> >
> >
> > Mike Meinhold
> > Rinn Duin #272
> >
> >
> > -----Original Message-----
> > From: public-list-bounces at alberg30.org
> > [mailto:public-list-bounces at alberg30.org]On Behalf Of Roger L Kingsland
> > Sent: Wednesday, December 15, 2004 10:50 AM
> > To: Alberg 30 Public List -- open to all
> > Subject: Re: [Public-list] Chainplate covers?
> >
> >
> >
> > There seems to be an inherent problem with any detail where the
chainplate
> > passes through an "open" hole in the deck that must be filled with
> > sealant.
> > At best it is a critical maintenance issue; at worst, a means for water
to
> > degrade structural bulkheads.  The chain plate must be flexible to the
> > point
> > where it first fastens to the bulkhead which is the top bolt.  At that
> > point
> > it must be completely rigid or the chainplate will move and eventually
> > loosen.  Why not move that "point of rigidity" up so it is above the
deck
> > and a flexible connection through the deck is unnecessary?
> >
> > As part of the redo of the deck on #148, I have removed the chain plates
> > and
> > filled in the holes.  One solution I thought about for the reinstall was
> > to
> > make 1/4" SS deck plates (roughly 2" x 3") with the a short piece of
> > 1/4" welded vertically on the center to fasten the bottom of the
> > turnbuckle
> > (basically cutting off the top of the cahinplate and welding it onto the
> > deck plate).  Then make "L" shaped brackets to mount on either side of
the
> > bulkhead with the short leg of the "L" mounted against the underside of
> > the
> > hull to deck joint (one of the stronger areas of the boat).  Vertical
> > holes
> > in the short leg drilled near the 90 degree bend would align
> > with holes in the deck plate and two bolts through the deck would carry
> > the
> > load from the deck to the chainplates bolted to the bulkhead.  All
plates
> > would be set in a 1/16" resin bed  and bolts would be tightened
> > sufficiently
> > to get that good old friction connection (none of that squishy 5200
> > stuff).
> > It seems this solution would be strong, stiff, dry and fairly easy to
> > install.   I have posted a sketch on
> > http://home.att.net/~jinnii/roger/perfect/pi_designs.html
> > and would appreciate any feedback.
> >
> > Thanks,
> >
> > Roger Kingsland
> >
> >
> > ----- Original Message ----- 
> > From: "Alfredo" <alberg30sail497 at yahoo.com>
> > To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>;
> > <dk.campbell at sympatico.ca>
> > Sent: Monday, December 13, 2004 3:29 PM
> > Subject: RE: [Public-list] Chainplate covers?
> >
> >
> > > Since we're on the topic, this is how I intend to someday do the
> > > chainplates on Free Spirit.
> > >
> > > http://www.gizmology.com/V40/Upgrades/chainplateFix/index.html
> > >
> > >
> > > --- "sousa, stephen (ENG)" <sousa_stephen at emc.com> wrote:
> > >
> > > > Don,
> > > >
> > > > If you could share the method used for the pattern it would be
> > > > appreciated.
> > > > This may be one of those items that would fall into the group
> > > > purchase area.
> > > > It would benefit all Alberg owners and could be very inexpensive it
> > > > we
> > > > purchase a large quantity. I would expect that all boats have the
> > > > same
> > > > installation for chainplates, so one pattern could be used on all
> > > > boats?
> > > >
> > > > Thanks,
> > > > Stephen
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: public-list-bounces at alberg30.org
> > > > [mailto:public-list-bounces at alberg30.org] On Behalf Of Don Campbell
> > > > Sent: Sunday, December 12, 2004 7:48 PM
> > > > To: Alberg 30 Public List -- open to all
> > > > Subject: Re: [Public-list] Chainplate covers?
> > > >
> > > > Randy
> > > >     When I bought #528, I was taken to see a C & C deck which had a
> > > > raised
> > > > flat area around the chainplates with the SS plates of which you
> > > > speak. I
> > > > knew I needed to redo the deck on this boat so incorporated a raised
> > > > flat
> > > > area at the chainplates on my new deck. I then went to the scrap
yard
> > > > and
> > > > found some 1/8th stainless plate that was food grade so probably 316
> > > > (which
> > > > is probaly not what is best for a marine environement, 304 is
> > > > stronger and
> > > > more durable,  I gather, but strength is not that important here),
> > > > cut it to
> > > > size- about 1 1/2" x 2 1/2" and then took it to a machine shop to
> > > > have the
> > > > slot cut.  I needed to file the edges a bit to get the chainplate
> > > > angle
> > > > correct in the slot but SS is relatively soft, so not difficult once
> > > > in a
> > > > vise. I have drilled 2 holes in the plates and drilled and tapped
the
> > > > epoxy,
> > > > raised flat areas to match so I just tighten the 2 - 1/4 x 1/2 ss
> > > > machine
> > > > bolts to seal the caulking. Total cost about $25 Canadian when I did
> > > > it 8
> > > > years ago -$20 of that  for the machinist. I need to redo that
> > > > caulking job
> > > > this winter. The raised part of the deck decreased the torque and
> > > > twist on
> > > > the chainpates at the deck level too. If you want to know how I did
> > > > the
> > > > pattern for the raised flat area let me know.
> > > > Don
> > > >
> > > > Randy Katz wrote:
> > > >
> > > > > Speaking of chainplates (nice photos of the reinforcement straps,
> > > > BTW)
> > > > > has anyone found a source for chainplate covers? They are the oval
> > > > SS
> > > > > plates 2-2.5 inches long, slot in the middle, that fit over the
> > > > > chainplate straps where they stick out of the deck. They get
> > > > caulked and
> > > > > sit over the deck opening, with the chain plate strap coming up
> > > > through
> > > > > their middle, and serve to help seal that deck opening.
> > > > > I've checked West Marine and a few other stores-- they seem hard
to
> > > > find
> > > > > at all but ones the size we need I never did come across.
> > > > > Anyone know where to get them?
> > > > >
> > > > > Many Thanks,
> > > > > Randy Katz
> > > > > #249
> > > > > Seattle, WA.
> > > > >
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