Dinghy development: Mast Failure

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Mast Failure

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=1160
Printed Date: 14 Aug 25 at 10:14pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com

Topic: Mast Failure

Posted By: Sam Tozer
Subject: Mast Failure
Date Posted: 04 Nov 05 at 12:17am

Hi there

has anyone had a mast fail with a vertical crack going from the mast foot and going up? If not does anyone have any ideas how this mast failed. There are no stress concentrations on the line of the crack.

Cheers for any help

Sam

Replies:

Posted By: Black no sugar
Date Posted: 04 Nov 05 at 7:06am

What type of mast is it? Aluminium, carbon? For which boat?

Posted By: Ian29937
Date Posted: 04 Nov 05 at 9:14am

Deck or keel stepped, rig configuration, mast controls, age and condition, wind conditions......

More info please!

Posted By: JimC
Date Posted: 04 Nov 05 at 10:10am

I'm seen carbon bowsprits fail like that. My *theory* is that when the load comes on the spar its flattened and forced very slightly oval, which then has a tendency to cause cracks between adjacent fibres as the matrix fails. Then of course its a weak point and propogates. The one's where I've seen it happen seem not to have an outer and inner 45/45 oriented layer of fibres which keeps the matrix together. So if this happened on a carbon spar I'd wonder if it were a similar machanismn going on - spar forced oval by side loads etc.

So the repair would I've done with the sprits - I've done a couple of them. Glue the longitudonal fibres back together and then reinforce outside and inside with fibres at 90 degrees to keep it together. If you can't get inside then more outside would be better than nothing.

Posted By: Sam Tozer
Date Posted: 04 Nov 05 at 3:41pm

Well it's a 29er lower section that has been sailed in various winds, the mast was taken out of action before total failure. I believe that it is an extruded aluminium tube. The mast was 18 months old and is stepped on to the mast bridge.

Posted By: redback
Date Posted: 04 Nov 05 at 10:36pm

I believe this is a common mode of failure for tubes in bending. I've seen a Laser 4000 rack begin to go the same way.

Posted By: gonzo
Date Posted: 07 Nov 05 at 7:13pm

Not exactly on the same topic but after having a 49er shipped to Dubai a spinnaker pole went and put them out for a week any ideas on what could of caused this???

Posted By: Lucy Lee
Date Posted: 07 Nov 05 at 10:08pm

Possibly overheating in the container causing degradation of the epoxy in the 49er pole (I'm assuming they have composite poles not alu!)

I think the temps in containers can get unbelievably high, esp when you are going somwhere nice and warm like Dubai! Did the container stand on the dock for days after unloading?

-------------
Fly Cherub!

Posted By: gonzo
Date Posted: 08 Nov 05 at 7:08am

ye there composite and thats the only half decent assumption we could come up with.

Only other alternative is that the pole didnt fully extend putting undue stree on an area that wasnt ment to have it.