[C320-list] Boom Vang Fitting

[Scott Thompson]

The vang will "spring out" a bit if it is under compression, as it will 
be if it is supporting the weight of the boom. Lift the boom with a 
halyard or topping lift first to avoid that. The vang will not come 
entirely apart without some disassembly, so you don't have to worry 
about it falling apart once you disconnect things.

I don't know whether it is advisable to straighten the piece out. I'd 
consult Garhauer about that. However I would not bother to fix it 
without a better understanding of why it bent in the first place. I 
would be surprised if an accidental jibe was the cause. Regarding the 
possible cause, years ago there was a thread on this forum (but I can't 
find it in the archives) about a problem that Annie Bennett had on 
Topcat, where that piece had been carving a little groove into the 
aluminum casting on the mast that it is attached to. There is supposed 
to be a protective stainless washer separating the two pieces so that 
this could not happen, but on some boats the vang had not been assembled 
properly and so the stainless "triangle" was allowed to rest directly on 
the softer casting. Then rocking of the boat in the slip had caused 
enough regular movement of the boom to gradually cause the triangle to 
carve a little groove in the center of the casting. Eventually the 
triangle caught in this groove during a jibe, preventing the triangle 
from rotating properly on its pivot. In that case the resulting bending 
moment caused a catastrophic failure of the vang. A picture of the 
resulting damages is on the web site here:

http://www.catalina320.com/mediagallery/media.php?s=2008111610222652

If you look at the picture you can see the wear in the casting 
underneath the stainless "triangle" piece. That's where the washer needs 
to be. And there should be another one protecting the top part of the 
casting also. That is, a washer should be immediately above and below 
the "triangle" so that it will not wear on either the top or bottom part 
of the casting. the lower piece is most vulnerable when the vang is in 
compression, while the upper piece is most vulnerable when the vang is 
under tension. Unless you

After I read about Topcat's problem and saw those pictures I checked out 
the situation on my boat and found that indeed my vang was not properly 
assembled either, and that the wear in the casting had started. I took 
apart the vang fitting and move the washers to the proper location and 
all has been fine since then.

Scott Thompson
Surprise, #653




On 5/14/2015 6:43 PM, Kenny Geist wrote:
> While putting the main sail back on today, I noticed that the triangular
> fitting at the bottom of the boom vang where it attaches to the bottom of
> the mast has bent about 30 degrees to starboard.  Guess there was an
> accidental jibe somewhere in her past.
>
> My question is, should I take it off and have it straightened at a machine
> shop or replace it as it might have been weakened.  Also, will the solid
> vang spring out when I loosen it from the fitting?
>
> Thanks,
>
> Kenny Geist
> Kennyge at Prodigy.net
>
> WINDRIFTER # 317