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> West Wight Potter Website at URL
> http://www.lesbois.com/wwpotter/
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>In a message dated 5/19/99 2:12:55 PM Pacific Daylight Time,
ttursine@gnt.net
>writes:
>
>> Have you done this w/ your boat, Judy? Has anyone else with P19s from
>> the era of ours?
>>
>> You are indisputably correct about the tuning (static and dynamic) of
>> a fractional rig, but I have always been hesitant to try dynamic mast
>> bending on Ursa Minor. Have you noticed the section on that mast? It's
>> positively _massive_ for the application, far larger and stiffer than
>> on comparable boats. I wonder if it wouldn't take entirely too much
>> stay tension to effect an appreciable bend. Or at least way too much
>> to be categorized as safe. Did your rigger take this into account?
>>
>> Regards,
>>
>> Bill Combs
>> WWP 19 #439 (Aug 1987)
>> "Ursa Minor"
>> Fort Walton Beach FL
>> ttursine@gnt.net
>>
>
>Hi Bill (and Dave Kautz too),
>
>The adjustable backstay was part of the original HMS18 design by Herb
>Stewart. As was the "massive" DM6 mast. As were the 1/4" shrouds and the
>shroud chainplates we all even on the newer P19s.
>
>The only thing that's different from his original rig design on my 1985 P19
>is the bow chain plate (which my rigger thought was strong enough but kind
of
>a weird way to do it). Dik Dickerson's HMS18 #11 (?) came with an
adjustable
>one identical to mine. They all came with the wooden compression post, the
>1/4" shouds/stays and the same shroud chainplates we all have on our P19's.
>
>I trust the competency of the designer of the HMS18/P19, Herb Stewart. I
>trust designed a rig/hull/mast/compression post that was strong enough for
>the adjustable backstay he put on it. Herb Stewart designed the adjustable
>backstay as part of the original rig design, so I feel safe using it. It's
>that simple to me. The original design by Herb Stewart was sound.
>
>If the boat was built according to Herb Stewart's specification, the
>adjustable backstay wouldn't worry me. The only question in my mind would
be
>"did the builder make hull and hull/chainplate strong enough to take it or
>did he skimp on the construction?" The rigger inspected my boat and
thought
>it was. Nothing but the mast flexes visibly when you tension the backstay
>and compress the mast column. Just as it should be.
>
>I change the tension on my backstay all the time. Bruce Little, the
previous
>owner, did too. With no apparent damage to the boat. In the almost 15
years
>of using an adjustable backstay on Redwing, no shrouds have ever ripped
loose
>from the boat and the mast has never come crashing down. The compression
>post hasn't been pushed through the hull and the cabin roof is just fine
>(it's solid fiberglass between the mast and the compression post. There's
no
>core to crush)
>
>And yes, the rigger was the one who showed me how to tune the shrouds/stays
>and showed me how much bend to put in the mast safely. The P19 carries so
>little sail area compared to the rigging that he wasn't worried about the
>wires, turnbuckles, etc failing. The stays/shrouds are manifestly strong
>enough, his only concern was the hull and chainplates attachments and he
was
>satisfied with them.
>
>Like I said, I only have to bend the mast a little to get an appreciable
>flattening of the mainsail draft. Bending it certainly increses the
>compressive load on the mast column/compression post and the tensile load
on
>the stays and shrouds, but my rigger didn't seem to be worried.
>
>BTW, since the newer P19's have a ligher DM5 mast, the compressive loads
on
>the stays/shrouds and the rest of the rig would be less then for our
heavier
>DM6 masts on the older P19s. The mast on the newer boats is identical to
the
>DM5 mast manufacturerd by Dwyer company. As for the strength of the mast,
Mr
>Dwyer personally told me that he thought the mast was plenty strong enough
to
>take it.
>
>I use the original equipment (adjustable backstay) that came on my boat all
>the time. If anybody has doubts in his own mind about the safety, don't do
>it.
>
>Best,
>Judy B