Question:
How feasable would it be for me to turn my pontoon boat into a sail boat?
After all, it is very much like a catamaran hull.
Any ideas or have I been sniffing too much epoxy.
Answer:
-The first question is whether it has the stability to take the heeling force
of the sail rig. If, at rest, the hulls are any more than 40% immersed or
if the beam is less than 60% of the length, then I'd say you should forget
it.
If those are OK, then the toughest engineering problems are in providing
strong crossbeams to bear the loads of the mast, forestay and mainsheet and
providing lateral resistance with daggerboards, centerboards, leeboards or
such.
-made some excellent points. Another modest suggestion is that you
should consider some sort of low-profile rig. A sprit or gaff rig
would reduce the rigging loads on your hull, which was certainly not
designed to handle a tall, high-aspect ratio Bermuda rig. If this
project is meant to be a fun, low-cost, low-stress try at sailing, you
could do worse than Home Depot spars and sails made from plastic paint
tarps.
-you have to figure out how much sail area is needed to move the boat. you
don't have to go to full size racing sails. in light winds the rule of
thumb is twice the area of the hull in contact with the water (wetted
surface) and in brisk winds the square root of the sail area divided by
the cubed root of the displacement ("Bruce number") should be greater than
1 and no more than say 1.2 (1.3 for a dingy). for lateral resistance you
could shove a daggerboard through a slot in the deck like they do on
sailing rafts. I'd locate the slots so the board is braced against the
windward pontoon.
you can always just run up a square sail and use it down wind while
using the motor upwind.
if the pontoon boat has a high profile the wind could blow the boat as much
as the sail reducing sail performance upwind. its called hull windage.
-David Beede did an experiment with a lug sail for going down-wind and I
think a yoluh for heading to weather.
http://www.simplicityboats.com/shantydocksails.html
You may also want to check out some sailing ferrys. There's a replica on
Lake Champlain
http://www.tricoastal.com/ferry/sailferry.html
