[Public-list] Chainplate knees and mast pad

[Don Campbell]

Mike:
    If you want to see what really happens with movable and flexible rigs,
then go to the Moth or I - 14 fleets and see what they do to balance the rig
and CLR. You will have to factor out the carbon bends, but at least appreciate
that they help incredibly on attaining rig balance over a wide range of wind
pressures!  It also may be that one would like to re-read Stuart Walker's
books, Small Boat Racing and   Performance Advances in Small Boat Racing,
which detail the changes made to the I - 14 boats over a time period. While
these books are not new, the physics of the sail rigs described is comparable
when the comparison is an Alberg. Other dinghys, like the Y-Flyer,   do have a
range of allowable legal mast placements (8 inches on an 18' 3" boat length)
which would allow one to sail under differing rig  balances, but those
skippers who win races have set the boat up to one step  location only (as far
aft as allowed by the one design rules),  because the boat is  fastest at that
one  location. It is always cheaper to try it  on a boat that has a design
that allows for movement of the mast step rather than making repeated
permanent changes and trying  to measuere the performance differences. The
application of the physics involved is the same,  whether a dinghy or keelboat
is what is under the skipper's feet.
Don

Mike Lehman wrote:

> I agree with George. Moving the chain plates and mast forward could cause
> excessive lee helm. I would not mess with the rig either.
>
> Mike Lehman
> ><((((º>¸.·´¯`·...¸><((((º>
>
> ----- Original Message -----
> From: "George Dinwiddie" <gdinwiddie at alberg30.org>
> To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
> Sent: Friday, July 30, 2004 12:14 AM
> Subject: Re: [Public-list] Chainplate knees and mast pad
>
> > Thickening the hull, even on the inside, is not going to add much
> > strength or rigidity.
> >
> > If you have gaps between the knees and the hull, filling that gap will
> > help a lot, whether you do so above the existing knees or glass in new
> > ones.
> >
> > I would *not* move the chainplates and mast plate forward.  Carl Alberg
> > designed the boat for a 7/8ths rig, but Whitby decided to build a
> > masthead rig.  Carl adjusted things as best he could, under the
> > circumstances.  Unless you are a good naval architect, or hire a good
> > naval architect, and recalculate the entire design, I wouldn't mess with
> > it.  The boat works quite well as is, and changing the geometry is more
> > likely to cause problems than to fix them.
> >
> >   - George
> >
> > Peter Amos wrote:
> > > I didnt explain myself very clearly.The extra layers of mat would be
> > > on the inside of the hull,also the plywood and chainplates. Only the
> > > bolt heads and washers would appear on the outside of the hull. I
> > > have no criticism of the engineering design of the original knees but
> > > the quality of their construction leaves a lot to be desired.All of
> > > them on Tait Tait have gaps between the top of the knee and the deck
> > > and a poor finish to to the glasswork.George makes a good point about
> > > the bulkhead,I overlooked that ,but I could reinforce the hull either
> > > side of it and strengthen the tabbing.The other options suggested are
> > > also worth considering.I may remove the old knees and make new
> > > sturdier ones set so that the chainplates are moved forward an
> > > inch.This would let me move the mast plate forward an inch so that
> > > ithe mast sits more squarely on the beam.Any opinions on that idea?
> > > Peter Amos Tait Tait #478
> > --
> >   ----------------------------------------------------------------------
> >    When I remember bygone days                         George Dinwiddie
> >    I think how evening follows morn;            gdinwiddie at alberg30.org
> >    So many I loved were not yet dead,           http://www.Alberg30.org
> >    So many I love were not yet born.
> >                                              'The Middle' by Ogden Nash
> >   ----------------------------------------------------------------------
> >
> >
> >
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> >
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