nacra masts 5.7 and 5.8
Hello,
How do the mast on the nacra 5.7 and 5.8 differ?
I have a 5.8 mast on my 5.7 boat. Don't want it to fall off the ball.
I noticed a lot of shedding of the white ball and the ball seems to spin when rotating the mast.
I hope I can use the 5.7 sail on the 5.8 mast.
Anyone with experience know?

How old is the ball?
Old ones, left in a high UV environment degrade. Buy a new one.
Secondly, look at the cup on the mast base.
Is there a sharp edge, or burr, that is cutting into the mast ball?
Don’t worry about the ball turning. Both my 5.0 & 5.7 do that. As the mast rotates left, it unscrews the ball 1/4 turn, when it rotates the other way, it turns the ball back down.
There may be other issues, but if your rigging is tight, the mast cannot fall off the ball
E C Hilliard
Nacra 5.7
Bombardier Invitation

The ball just screws on by hand. I was experiencing ball spin on my Nacra 5.2. Last week I polished the mast base. I took 120grit paper and taped it over a phillips screwdriver handle and chucked it up in a drill. I followed that with 220 grit. Now it is smooth and doesn't spin the ball.
Rob
"If at first you do not suceed, well, so much for sky diving"
Not sure if it's a good idea to let the ball rotate. A lot of focused pressure on those threads and it certainly wasn't designed for that. Mine started doing it when the ball started to flatten out at the top after a lot of use. I got a new one and hand tightened it as much as possible and then used a channel lock pliers and gave it an extra 1/8th inch, no more!
found this at below link for Nacra measurement guide
5.8 mast length = 9156mm
5.7/5.5 mast length = 8858mm
https://ausna.com.au/wp-content/uploads/2019/03/2015-NACRA-Measurement-Guide.pdf

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