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JY14/Hunter140 crack under mainstay mount

Jul 7, 2015
3
JY 14 WIndigo Lake
I've read through the posts about crack repair on a Luran S hull, but I haven't seen anything like this. This is both my first post and my first attempt at this sort of repair, so any advice would be most welcome!

I was having a lovely sail in a stiff wind with a crew member when we heard a sharp crack. After a few minutes, we noticed that the area around the starboard side mainstay was bulging up in an alarming way. We limped back to the dock, being as gentle on that tack as we could. A crack had developed that is about 18inches on the bow side and 6 on the stern side. There is a kind of lip to the top of the boat to which the stay mounting is attached, and it seems to have broken away from the hull. I've attached pictures.

I understand that I should dremel out the crack and use Plexus (or equivalent). My question is whether this is the sort of crack that requires an additional reinforcement like fiberglass.
crack-bow-side.jpg

crack-stern-side.jpg
 
Apr 11, 2020
124
Hunter 170 Grapevine
Fiberglass will not bond well to Luran. I bought a 170 which a previous owner had overlaid with fiberglass. One of the first things I had to do was peel of a layer of delaminating fiberglass from the gunwales.
I think plexus alone is probably your best bet. Grinding out a good-sized "V" to provide maximum bonding surface would likely serve you well.
 
Jul 7, 2015
3
JY 14 WIndigo Lake
Thanks! I've read that the epoxy resins won't bond to the Luran, and your experience fits with that story.

I've use the dremel to clean up the surfaces. This is the joint where the hull is joined to the deck. However, the substrate of the hull does not make direct contact with the substrate of the deck. There seems to be about 1/4 inch or more that is just the Luran surface holding the two pieces together. This seems to me to need reinforcement, but I could be mistaken--I guess Luran is pretty tough!

The repair manual says to use bi-directional fiberglass cloth and wet it with Plexus. That ought to bond better than the epoxy resin. Anybody have experience with that process?
 
Apr 11, 2020
124
Hunter 170 Grapevine
That makes sense. I think I fell into the trap of equating fiberglass with the polyester resin that it is typically impregnated with.

I see two potential problems with the approach you describe. With the small tube product I have used, you get 5 minutes maximum working time. Also, the product I am familiar with is more a gel than a liquid, so working it into the fiberglass might prove more difficult. If there is a Plexus product that flows well and provides a long enough working time, that might work.
 
Sep 24, 2018
1,352
O'Day 25 Chicago
This was a common issue with the JY's. I knew someone who repaired his. I'll see if I have any emails that detail his repair
 
Jul 7, 2015
3
JY 14 WIndigo Lake
Thanks Project Mayhem! I’d love to have information from someone who has repaired this kind of thing. Looking at the engineering, it is not to surprising that this is a weak point that will eventually fail.