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Sailing season is done and you’ve taken the mast down and decided to really take a good look at your mast joint. And to your dismay you find the whole thing loose and hanging by a thread. On this one, sometime ago, someone had noticed that the 1/4 threads were stripped and decided to go up one size to 5/16. This seemed to work for a while but now they are stripped also. To make matters worse the cap nuts on the through bolts are sloppy in the holes. Now what?

The thing to remember is that, on this type of mast joint, the diamond pad eyes and through bolts form an integral part of the mast joint. They both work in unison.





We like to use 3 horses for this job. Getting the mast level and neutralizing the shearing forces from the joint fastenings.



After you’re happy that it’s level and not going to roll anywhere, remove the hardware.





Since 5/16 screws were used already, and going up another size was not an option, we decided to use a product called Heli Coil. This product allows you to reinstall new threads into a stripped hole.

The procedure is simple. The kit provides you with a correct size drill bit to open up the hole and a special tap to retap the hole to accommodate the thread insert.



Loctite makes a primer that also acts as a catalyst for the #262 threadlocker. This sets up really quick and is permanent. Both are recommended for this job. The inserts are about 5/8 inch long, just enough to go through the outer and inner sleeve. I install them about one thread below the surface.


New 5/16 threads






Cleaned up hardware reinstalled with new 5/16 flat head screws and more Loctite #262. This customer opted for his new hanger lines to be installed with D shackles.




The through bolt holes are elongated, ovalized and generally sloppy from wear. And since the diamond pad eyes works in conjunction with the through bolts, it only makes sense to tighten this area up as well.





We like to use a stainless sleeve. The O.D is 3/4 and the I.D. is 5/8 (the same as the O.D. of the cap nut)



The procedure is to drill out the through bolt holes to 3/4 and after measuring the mast diameter with a set of calipers, cut the sleeve to length minus a bit so it sits just below the surface on both sides. Remember to deburr the inside and outside of the sleeve.



We coated the sleeve, where it’s in contact with the mast, with an anti-seizing compound. Also we coated the cap nut inside and out with the same. This will enable the customer to periodically check for tightness and will delay galvanic corrosion.



Since the sleeve is almost as large as the cap nut top, we used a 5/8 flat washer to spread the load when tightening, which is what you want.







This job is best done with the mast down. If done this way, and the Loctite allowed to cure for a day, I believe this joint will be trouble free for quite awhile.



Mast Joint Repair

MQYR 2017