motoring sideways to boost upwind VMG

If I had some form of propulsion that could apply a force anywhere on a heavy displacement sailboat to improve its upwind performance (track over ground to windward when beating) where should it go?

I'm assuming that the boat is making close to it's "hull speed" through the water along its heading. But that perhaps it can only achieve a course over ground 50 degrees off the wind because of inefficiencies in its rig or hull shape (ignore current).

Could I vector a small amount of thrust to enable the course over the ground to be better, say 35 degrees off the wind ? If I do a simple vector addition, one knot of sideways motion added to, say, 6 knots of forward motion can turn a lousy upwind performance into a stellar one.

If I simply fire up the engine pushing astern I will be increasing the forward speed of the hull along its heading but as it's already close to hull speed, adding a knot will take a lot of power I think

I have no Idea how much power it would take to thrust the boat sideways, but the videos I see of docking thrusters make me think that it is not too much, maybe a few kW to generate one knot (0.5m/s) sideways. However, I know boats get more stable when they are moving, and maybe the thrusters only work because there is little forward motion to factor in.

If it's feasible, should this force be applied amidships, or closer to one end or the other of the hull to generate lee or weather helm that might combine with the rudder position to improve the situation ? Or will simply pumping water from one side of the keel to the other change the pressures and generate additional lift ?

My reason for asking is that the kind of boats I prefer are notoriously bad at going up wind. As a gentleman and a cruiser I won't sail upwind when I can help it, but if it becomes necessary I'm not above boosting the upwind performance with a little cheating, especially if I can do it with a modest electric motor.

 

Basically, no. Even for a pretty crappy upwind boat, the side force that the sails are generating is at least double the driving force, and might be 3 times driving force. So when you run the motor sideways, you need two to three times as much thrust as you need to drive the boat forwards just to take the leeway off. So you would be much better off just lowering the sails and motoring - probably 1/3 to 1/4 as much fuel if you just motor dead into wind until you obtain a gentlemanly heading to your target.

 

I would suggest you could improve your upwind sailing performance with a deep reef in your sails, pull your boom to mid-ships with a barber hauler or push your traveler car upwind of mid-ships, and use the engine to drive closer into the wind.

Reducing sail and pulling them as flat as you can, reducing twist and camber, should allow you to point a lot higher. Less sail also means less weather helm and less air resistance to allow your engine to push into the wind.

Use the reefed sails more as a stabilizer than a driver.

BTW, I don't think 50° off the wind is that bad.