From our friend roadrunner!
Sooner or later most of us will likely strike something with our Drives and bend a mast. It's pretty easy to straighten but, depending on which of 3 sprocket styles is in use, there are different methods available.
The current ('09) sprockets
(top sprocket below) have brass inserts and are stronger than the earlier plastic versions.
Straightening a threaded mast
by hammer or vise would risk damaging the threads, so I prefer to bend it in place (without removing it from the Drive). Although it can be bent freehand with the hands, you get better results using the smallest pipe that will sleeve over the mast. This keeps the shaft straight while it is being restored. Since our masts are 5/16", I was lucky enough to find a 3/8" pipe at a local salvage yard and combine it with a 5/16 brass sleeve to take up most of the remaining gap.
Fortunately, most masts bend backwards (the direction in which the boat does not yield), and that's the easiest direction to correct. After removing your fins, measure the distance between masts at the base. Planting the nose of the Drive on a solid surface, bend the tip until the distance is comparable at the tips.
Bending sideways is riskier and rarely needs to be done. Small variances can be adjusted out by re-centering the cable/chain. If you have to bend this way, split the fins to their maximum, then apply pressure to the side. Understand that you may pop a cable swedge loose -- be careful.
For those who have '08 and earlier plastic sprocket
with Allenhead lock screw (top picture, lower sprocket), I recommend removing the mast and straightening it with a hammer or vice. There is a risk of splitting or weakening the sprocket if attempting to straighten without removing. When reinserting the mast, pre mark the flat spot (see below) so you'll know when it is facing the Allenhead screw.
Tap it to make sure it is fully seated. If it is wobbling in the sprocket, you should either replace the sprocket or apply epoxy to stabilize the mast (or risk having the mast fall out when you least expect it). Locktite your Allenhead lock screw in and make sure it is fully seated -- check the other one while you're at it. Screws that are not fully seated (left, below) or that back out are the primary problem areas with this style of mast. You can tell by the final depth of the Allenhead screw. The above picture shows the screw properly seated.
Anyone with a stainless sprocket
(below) can straighten their mast by with any method -- in place, vice or hammer. In any event, it is a good idea to change the cotter pin mast retainer at this time, as it takes a lot of stress.
If your ST or Turbofin tears through the side (and are the newer tougher material that has been used for the past year), it will generally stretch first so the tear is at least 1/2" away from the mast tip.
If so, you should be able to slide the fin back on without any problems or further action. Just be careful slipping the mast past the hole.
PS: All sprocket styles are still available from Hobie and may be adapted to any Drive. The Brass insert sprockets however, must use threaded masts. Any mast used with a stainless sprocket must have a hole in one end for the cotter pin.