Originally Posted by Stumble
Measure the highest point the sail can hit on the boat, then install the radar above this point by a foot or so. It's gets trickier if you ever decide to install a 155 for light air venues since it has to go even further up.
Don't know type of boat you have but my 135 goes practically to the top of the mast. No way you can mount the dome above the theoretical point where the sail can hit the mast. The question is, though, where does sail hit the mast in reality. Normally, most of the sail flaps far forward of the mast when tacking with only the clew and about 2 - 3 yards above hitting the mast.
I have the same radar as the OP on a 38 footer, mounted below the second spreader at the front of the mast. We asked North Sails
for advice last year and they installed patches on the genoa. We have not yet seen any instances where the sail hit the radar dome, let alone hit it hard. I've stopped worrying about it.
In summary: make sure you don't mount it too high so it is not too close to the forestay (also very important if you use a solent stay!), and don't mount it too low to prevent a flapping sail hitting it. Patches on the genoa don't do much except give you a warm fuzzy feeling, IMHO. At least, on my goat, maybe YMMV.