Unequal Mast Rotation

[WaveyDavey]

Downwind my mast rotates fully (i.e. 90 degrees) on port gybe, but only about 70 degrees on starboard. This appears to coincide (though it could be my imagination) with a feeling that I have more downwind boat speed on port than starboard.

My first thought on this problem would be unequal shroud or bridal lengths, but I fitted an all-new set of standing rigging this season and I checked all the lengths matched. Both shrouds are in the same whole on the shroud adjusters too. I don’t wind up the rig tension very high either.

Next thing is to flip the boat in the park and see if the shackles are sitting nicely in the hound fitting. Whilst I’m doing that is there anything else I could check?

[Robert]

Is the plate in the mast heel which sits on the wear pin in the mast ball in good condition?

[WaveyDavey]

That's a good point Robert. I hadn't thought of the ball/mast foot being a problem but I can see how it could be.

I'll drop the mast and take a look.

Thanks for the tip.

[Steve Willis]

Look at the sides of the mast heel casting as well as the position of the wear on the plate not just the depth of wear. Is the mast straight?

I had to replace one of our castings last winter as it had worn away about 3mm on one side - the wear mark was about 8 mm off centre. I believe the boat had been left for several years before we bought it with the mast up and sideways onto the prevailing wind. Thus the base of the mast was sitting off centre.

Article with photos pending for the Newsletter.

Steve W

[Steve Willis]

Following poor old Kevin D coming ashore from his F7 capers last weekend he was complaining about the mast not rotating and even locking one way or the other. We dropped the mast and looked at his mast foot.

The stainless steel pin from the ball was missing and the mast foot plate was bearing on the alloy ball - with wear to both the ball and the sides of the foot casting. No grease on the ball either !

As his mast is up and down like a yoyo for events it appears that the pin has fallen out during his motorway careering - maybe aided by the bass from his car stereo not that many feet in front of the beam whilst towing !

However this can only have happened a short time ago and it is clear that he has lost about 3mm off the top of the ball already.

Got to get him sorted for the Nationals.

I have cut away the old mast ball that I had left over from Joan's boat when I replaced the ball. This has allowed me to remove the pin and see how it was fixed - basically FRICTION.

For future reference ( I know someone raised a query on this a while ago)

the pin from the ball on Joan's Spark was 14mm high
12.5mm in diameter for the first 7mm up from the bottom
then 12.6mm for the next 6mm
i.e. it has a shoulder just over half way up
then the top 1mm is chamfered to form a dome on top

The hole in the ball was 12.5mm in diameter and the pin was purely held in by the interference of the top shoulder on the pin. The hole was drilled not reamed as it has a shaped bottom.

I will check Kevin's much later mast ball and see how they compare - might be a lathe job to get it right though.

Steve

[Robin Newbold]

Check your shrouds are the same length, this could affect it.

[Steve Willis]

Sorry Robin, not with you.

The mast ball wear pin in the top of the ball is gone (hole only left).

This is nothing to do with shrouds ?

Steve

[Robin Newbold]

I was only guessing, thought it could be a possibility

[Bob Carter]

Sorry Robin, not with you.

The mast ball wear pin in the top of the ball is gone (hole only left).

This is nothing to do with shrouds ?

Steve

Hi Steve,
This was a problem with boats about Kevin's vintage (2000 Mellennium editions). I had the same problem with 1945 and I know of a few others that had the same problem. I suspect that the pin in the mast ball was not made with adequate interference. It only becomes apparent after the boat is trailed - particularly if it is upsidedown on top of another boat.
I suspect that Dave Halls problem is more subtle and due to the uneven mast foot/ball wear which you have reported on previously.
Cheers
Bob