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martin.langhoff

CF Mast damage at through-fitting

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The catamaran mast is down while the hull is getting other work done, so I check it out for maintenance and found that one of the fittings for the diamond shrouds has dislodged itself, "cutting" through the side of the mast.

Ah, the joy of boating.

My head is full of questions.

  • This is a one-piece mast, how the F did they get the bolt in there?! 
  • Can this be repaired to something close to original strength? Simply sanding off and laying down carbon won't work, I'd expect a washer (delrin?) is needed to spread the load/support. How can this be done without losing the bolt inside the mast?
  • The failure mode is a mystery, I haven't messed with the diamonds in ages, other than checking tension. I assume some mishap after lowering the mast, boat is dry-stored at club, mast is in a spot where it should be safe but idiots abound...

Picture in a moment.

The boat is an 18 foot all-carbon-fiber lightweight catamaran, laminate sails, carbon rig, the works - Whisper, from WhiteFormula. 

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Poor design, doesn't appear to be a bearing structure in the way of the bolt, might consider glassing in a FG tube and throughbolt instead. Insulate and surface looks weathered. Of course wall zipper require repair.

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Tube seems the way to go.

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Enlarge the original hole on each side. Glue in a glass tube and trim the ends off when it's cured. Make up 2 patches to cover the hole and zipper + about 50mm extra top and bottom and maybe 30 each side. Shape them up in an oval or elliptical shape and smooth off the edges, clear finish them. Mark where they glue on, and sand or grind the clear coat off the mast, and glue them in place. Do the same at the other end. 

Better than new. 

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30 minutes ago, fucket said:

Tube seems the way to go.

How do you get the bolts in at the right place & depth? Or should I put bosses in instead?

How do you protect threads?

When I do this, clearly I'll recoat the mast with clear. It's due for it.

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1 hour ago, martin.langhoff said:

How do you get the bolts in at the right place & depth? Or should I put bosses in instead?

How do you protect threads?

When I do this, clearly I'll recoat the mast with clear. It's due for it.

I would probably through-bolt both fittings together.

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1 threaded rod through the tube with washers under the shrouds, gets the compression right.

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Agreed here. Looks like a design failure, is there even a thru tube in there? std 50:1 scarf ratio, but using Hall style isoplates as bandaids to cover up. Will want to fill the zipper with epoxy mix as well before applying patches.

On 6/13/2018 at 3:27 PM, Alcatraz5768 said:

Enlarge the original hole on each side. Glue in a glass tube and trim the ends off when it's cured. Make up 2 patches to cover the hole and zipper + about 50mm extra top and bottom and maybe 30 each side. Shape them up in an oval or elliptical shape and smooth off the edges, clear finish them. Mark where they glue on, and sand or grind the clear coat off the mast, and glue them in place. Do the same at the other end. 

Better than new. 

 

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