[C320-list] Boom Vang Fitting

[Kenny Geist]

Thanks so much Scott.  Excellent commentary.  I have Kevin at Catalina
checking for the part and now I have a thorough undersanding.

Best Regards

Kenny Geist
Kennyge at Prodigy.net

WINDRIFTER 320

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of Scott Thompson
Sent: Thursday, May 14, 2015 7:20 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Boom Vang Fitting

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

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