My chipstow mast has on several occaisions allowed the bolt rope to pull out of the track. I have a newish rowsell and a barelely used practice Batt in mylar.  The track seems to be even in width and I cant find any cracks.  sometimes its been around the top batten pocket and others justabove the tack.  advice please!

Thicker bolt rope!

The bodger is probably right, the usual spot a 'too small' luff tape pulls out is at the grove entry.the sail coming out at the top batten is likely to be caused by the batten luff protector (a nylon fitting on each side of the sail) as the sail turns about it's bolt rope the protector will certaily lever out a small luff rope.
Remedy-- Firstly if your sail was made for this specific mast the sailmaker should of known or at least asked for the groove dimentions. If hes got it wrong they will almost certainly rethread a larger bolt rope free of charge.(ABS)
 Secondly do it yourself, simply carefully unpick the siezings at head & tack, whip on a slightly rope to one end and simply pull through. Then resew the head seizing & leave50mm spare sticking out at the tack, you can sew this off once set up on the mast.Theres no rocket science in this the is there purely to hold sail to mast.
This will only work if the row of straight stitching behind the luff rope is far enough back to allow a bigger rope. If to tight resort to option one.  Simple enough? 
best of luck Barry (retired (early!) sailmaker)

best phone now 01268710111 Alan Jackson

I think the problem is that the tracks aren't necessarily all that stiff, and certainly the batten receiver can be stiffer than the surrounding track.  It appears to be less of a problem on the later masts however.  We do have a fat bolt rope now though...

I had odd occasion when my main use to pull out at the base and top battern when was really windy (force 5-6 kind of stuff.) Is really bad news if comes out at top battern as will stress rest of track when pull the sail down!

I had some extra carbon laid over a fillet by Linton, about 6 inches at both points. Not really going to change mast bend, but solved the problem. Sort of job you could do yourself.

Ross

Ross
Do you know the make of the carbon mast on 3538 as the new owner is looking to order new sails (Ken may already have phoned you).
Thanks
Brian

Yes, this was more of a problem with the earlier chipstow masts and on one occasion on the old boat, we had the bolt rope pull out at the bottom and "unzip" the whole way up the mast.  Not fast when you're in 2nd place....  It also leaves you with the problem of a flogging main that's only attached at the top and bottom.  However, it only seems to happen in breezier conditions when you're well raked back and have a fair bit of rig tension on.

We found the best remedies were:
a)  Thicker boltrope plus
b)  Tie a piece of string/velcro from the cunningham eye on the main around the mast to prevent the bottom of the sail pulling out of the track in the first place.

Alternatively you could try getting Jacko to stiffen up the track.  Hope this helps

Thanks Peeps, you're all very helpful, thicker bolt rope until end of season and then a Jacko re-furb. - Sorted!

Brian 3538 has a proctor mast. Due to the design I think it very unlikely that the sail could pull out though (track built into the mast on inside, not outside.)

Thanks Ross - I thought it was a Protor.