Can you do the rudder with Cheap Diver?
Typically, no.  Cheap Diver may clean some tapered rudders, but you would have to work
from behind the rudder, probably backed into a slip.

Will Cheap Diver harm my racing bottom?
We spent 3 years trying various mesh materials in order to find one that is not too coarse,
yet is durable, and does not break down with normal use in the sun and water.  Many racing
J/24s have smooth (sanded to 1500), hard bottoms and Cheap Diver has not damaged
them despite regular use.  Brand new, the mesh is stiff so it should not be pulled too hard
against the bottom; the mesh will soften as it gets used.

What size would work on my boat?
The shorter version (24 foot) is ideal for boats up to 24 feet with a fin keel.  Boats that are
wider than 8 feet and longer than 24 feet can use the 24 foot version by tying a sheet onto
one end, but it is not recommended.  The longer version (36 foot) is ideal for boats 24 to 36
feet long with a fin keel.  

How much of a J-109 can you clean with the Cheap Diver?
One must be fairly creative to use the longer version (36 foot) on a J-109.  The front of the
hull down to the keel can be cleaned with a side to side flossing motion.  Due to the vertical
keel plan, only the top 2/3 of the leading edge of the keel can be cleaned.  The hull adjacent
to the keel can be cleaned by standing at the bow and walking back on each side while
working front to back.  The hull in front of the rudder can be cleaned by letting the Cheap
Diver sink beneath the rudder, then working forward from the stern to the primary winches
from side to side--this will clean the hull from the motor back to the rudder.  Cheap Diver will
effectively clean 2/3 of the J-109 if done on a regular basis.