[C38] boom failure

[Glenn Terry]

Tom,

Very interesting.  A repair would save a lot of time not having to 
remount all the hardware on a new boom. 

What kind of preparation did you do at the break?  Did you remove any 
metal, square off the break, paint removal, etc.?

The diamond shaped reenforcement tabs would solve several issues.

How was the splint constructed.  If it laid directly on the mast it 
would interfere with weld area.  Did you block it out from the mast or 
was it temporary so the initial welds could be made and then removed to 
complete the project.

The metal fabrication shop I have used in the past has the ability to 
make the jig and align it spot on. 

Any more information you can give me would be appreciated.

Regards,

G!enn


Tom T. wrote:
> Hi Glenn,
>
> I can't name a good replacement for your boom but before you do that, let
> me tell you of another experience I once had that may help you.
>
> We had a highly modified South Coast 22 once that I used for design
> experiments.  It had a very efficient hollow steel keel that was bottom
> weighted with lead.  The keel weighed 550 lbs, same as the original iron
> keel but my center of gravity was much lower because of the bottom weight
> of the new keel.
>
> We were sailing in a stiff breeze and really flying when my mast pumped
> forward in a puff making the mast fail at the spreaders.  The whole mast
> and sails came crashing down and we slowly retrieved the sails, shrouds,
> boom and mast halves and motored back to port.
>
> I salvaged that broken mast.  We made a splint of wood and clamped the two
> pieces of the mast together and welded them back together.  Then we took a
> piece of another mast, slightly larger than ours, and cut diamond shaped
> pieces to overlay the welded area to permanently splint the damaged area.
>
> After we repaired the mast, it looked like the factory had made the mast
> with the reinforced section welded at the weak spreader area.  Not only did
> we salvage the mast, it was now much stronger than originally and not prone
> to future failure.
>
> The key to this repair is the diamond shaped plates made from another mast
> to overlay the repair area.  The reason for diamond shape is to not
> concentrate the weld area of the plates.
>
> In my opinion, all masts and booms should come from the factory with these
> diamond shaped reinforcements.  The failure point of any mast or boom is
> usually where either the shrouds meet on the mast or the vang meets on the
> boom.  Those points are the highest strain points weakened by holes drilled
> through them and the diamond plate weld procedure makes those points  
> stronger than the rest, as they should be.
>
> You don't personally have to own a MIG, TIG, or any other type of welder to
> do this, the preparation is the key element of a good repair.  Anyone can
> make the wood splint, find a piece of old mast or have some aluminum plates
> rolled and fabricated from a metal shop if not successful in finding a mast
> stub for the metal overlay splint, and grinding a good fillets on the weld
> edges of all pieces.
>
> Once this preparation is done, any good weld shop equipped to weld aluminum
> can weld the mast together at a minimum of expense.  Like an auto collision
> repair, it's the preparation that cost the most, not the final painting of
> the car.  Same here, prep the mast properly and make a good splint from
> some straight wood and the repair price should be very small compared to
> the price of a new boom, let alone the fact that your repaired boom would
> be actually much stronger than a new boom.
>
> Email me if you want more details.
>
> Tom Troncalli
> Renata #95  
>
>   
>> [Original Message]
>> From: Glenn Terry <Glenn.Terry at Sun.COM>
>> To: Catalina 38 Listserve <listserve at catalina38.org>
>> Date: 7/18/2009 11:42:52 PM
>> Subject: [C38] boom failure
>>
>> I had a rookie at the helm and he executed a perfect uncontrolled jibe.  
>> The boom broke at boom vang mount.
>>
>> Can anyone give advice in the replacement of the boom?
>>
>> Regards,
>>
>> G!enn
>>
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>
>
>
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>   

-- 
Glenn Terry
OEM Software Licensing
Sun Microsystems, Inc.
4180 Network Circle
USCA18-312
Santa Clara, CA 95054
w-408-404-8966  x4-0966
f-408-404-8966
glenn.terry at sun.com 


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