IMHO:
The use of a boom vang on a loose footed mainsail is very limited... When you
apply tension to boom vang you really are pulling only sail clew down and
deforming sail... You need to also haul aft clew back in order to affect sail
correctly... Something difficult if not impossible to do when wind is
exceeding 15mph and that line to adjust block/clew is way outboard on end of
boom... That is one of reasons why I went to a 9' boom on my P19. I added
sail track and an adjustable block to aft end of boom, the line goes to a
cleat exactly above fwd end of cabin hatch so I can reach it easily. By
pulling on aft clew line I stretch sail aft (flattening it) and by pulling on
boom vang I pull it down affecting position wind spills off mainsail. This
effectively modifies sail shape, to an extent, while bending the hell out of
boom. The effect is nowhere close to effect of boom vang on my ole Columbia
22's boom footed main... Or even close to impact of boom vang on my ole Cal
30's mainsail...
I fear P19 boom handling a loose footed main may not handle stress of an 8:1
boom vang pulling it down without taking a permanent curve. I would think a
boom vang is most effective on a vessel with foot of main attached all through
boom, that way you can pull down the whole sail and not just the aft clew...
My observation of Potter's under sail leads me to belief that an aft stay will
improve performance markedly and way more than a high tension boom vang with
or without clew adjusting ability. Perhaps (heresy!) a solid non adjustable
boom positioner (vang?) that kept boom at correct altitude and location would
be as effective as an adjustable one. An aft stay will keep that saggy
forestay straight and add pulling power to jib/lapper/genny where reaching
power is really gained. In my case, an aft stay is just one more thing to rig
when daysailing and reduces ability to knock down that mast at will...
The boom vang on my Sovereign 13 (also loose footed main) is used primarily to
keep boom horizontal and from forcing a flying jibe, goosewing jibe or
knockdown when running. It is extremely limited in usefulness when reaching
into heavy winds. In effect adjusting clew of main while keeping light tension
on boom is way more effective in flattening the sail...
Sometimes we try too hard to turn a Volkswagen into a Corvette, expending
amazing amounts of cash in a futile attempt... Perhaps it would be cheaper to
buy the Corvette... Or an F27 in our case...
{;^)
Best
Solar Fry
"Trying to keep some cash in my pocket at same time as open mind in my head"
{:^)
In a message dated 99-01-14 19:15:00 EST, David Kautz writes:
<< Subj: Attaching boom vang tackle
Date: 99-01-14 19:15:00 EST
From: david_kautz@hp.com (David Kautz)
To: wwpotter@tscnet.com
- - - - - - - - - - - - - - - - - - - - - - - - - - -
I think Judy's description of vang installation was excellent. Her
method uses only one additional part, the ring, which, in my opinion is
a worthwhile cost to pay in order to have all fasteners loaded in shear
rather than tension.
As far as the amount of mechanical advantage is concerned, I think it is
somewhat a matter of personal preference. My old boat, a 14 ft racing
dinghy called a Sesame, had a 3:1 vang which took a lot of strength to
operate in a breeze.
I have a different consideration as regards vangs on the P-15: I've
experimented a little with off-center vang tackle to pull the boom down
when sailing off the wind. This type of gear, if you are not familiar
with it, attachs to the deck or cabin top (on the Potter) and pulls
straight down, rather than at the 45 to 60 degree angle that a mast
anchored vang pulls at. The obvious disadvantage is that the vang must
be disconnected in order to jibe or tack (though it also acts as a
preventer against unwanted jibes).
My observation is that the P-15 boom is very light and flexible and may
not be up to the task of handling a 4:1 or higher purchase unless it is
used very delicately. In addition, conventional vangs pull the boom into
the mast with as much or more force as they pull down. This places a lot
of compression force on the gooseneck, another not-very-robust part on
the P-15. Indeed, some competition sailors will use the compression
force of the vang to windward to intentionally bend the mast, thereby
changing the shape of the sail.
The standard mainsheet arrangement on the P-15, with the mid-boom
purchase does a fair job of keeping the boom down in my experience, so I
guess I'd like to question whether one should install a vang at all on a
P-15 with the standard mainsheet. I know some of the folks who have
switched to end-boom sheeting have subsequently added a vang with good
results, but I'm curious as to how that compares with the original
set-up. Can anybody help me with this?
Dave Kautz
P-15 #1632 "Tilly Lucy"
>>