Hunter 35 pointing ability?

[islandwheels]

New to forum, but thought some might have some boat design insight!
Friend Steve has a mid 80's Hunter 35. A couple of times we've took it from Florida to the Bahamas. It had a great deal of weather helm and didn't point very well. When diving under her to check on something I noticed Steve replaced a hurricane damaged rudder with stainless tube and a large steel plate welded on to the back of the tube for a rudder. To me that explained the hard weather helm as the rudder wasn't balanced (no area forward of rudder shaft). I was hoping that this explained poor pointing as well. We replaced this steel behemoth with the home rebuilt original rudder. I noticed that the rebuilt rudder wasn't very fine on the leading edge at all maybe more like a 6" tube radius along it's leading edge.
This old boat is a honey, she is to me, very fast, on one stormy (blustery) night on a beam reach 7.5 kts (cog) was not uncommon, also on a broad reach over 8kts. but pointing abiltiy, I may be wrong but I'd be pressed to get her to point 75 degrees off wind. Granted my former Santana 20 may have spoiled me, (to me she's the benchmark to measure all others), but is 45 degrees off wind asking to much from this cruiser

[alan white]

Look to the rig too. Was any of the rig modified, such as converting to cutter from multiple headsails that included a genoa jib? Some changes are comprimises that work better at some points and not others.
Your friend ought to be able to tell you how well the boat originally pointed. He would know if the boat suddenly couldn't point. If it was after changing the rudder, then the solution would be to make a rudder like the original...?

[jehardiman]

Normally, a sailboat should have about 1-2 degrees of weather helm when on the wind. This is to ensure good behaviour overall. Weather helm is caused buy the moment couple between the Center of Effort (CE) of the rig and the Center of Lateral Resistance (CLR) of the hull.

While an unbalanced plate rudder will feel heavier than a balanced rudder, if it is of proper area, there shold be no additional weather helm, though it will feel like it is pulling more than you are used to. FWIW, data I have taken and seen shows very little difference between plate foils and NACA shapes when cord/thickness excedes 20 If the rudder was a NACA 0012 to NACA 0018 and was replaced with a plate of the same cord, then I would expect increasing performance loss as the C/T gets smaller.

If the plate area is too small, then there would be additional weather helm as well as the need to apply more force to hold it to weather. Additionaly, a plate rudder will stall sooner than a foil, which may be causing the CLR to shift forward, giving the poor ability to put her on the wind.

As I, and Alan pointed out, weather helm is also affected by the CE of the rig and the loading of the hull. Check to make sure the hull is sitting her lines, and the rig is not raked too far aft.