Finding the CLR

This might be a simplistic question, but thought I’d ask anyway. Using the push thru the water sideways method of locating the CLR should I rely on using the hull empty or should I have my equipment in it? How about the rudder?

Basic and quick answer - The boat should be sitting on it’s “designed” waterline - you should include the rudder. Get fancy and do a series of tests as the boat heels since CLR will move forward and backward depending on heel angle of hull - especially if long overhangs which increase waterline length when heeled.

Dick’s point is well taken. I don’t like to risk my electronics to the test tank (that highly sophisticated research tool in my laundry room) so I weigh the servos, reciever, battery, etc. and put lead weights in the hull to get her on waterline. They can easily be moved around for heeling tests.

Bill H


I found that establishing my Razor CLR very tedious. I think its all down to scale again. The tolerances that we work to are fixed by our patience and skill level, so if the serious sailors try to measure the CLR of a 1 metre hull to the nearest 1mm then for the same accuracy we have to be closer to .3mm with our Footy - in English thats only 12 thou :rolleyes: This is not a trivial task with something the size of a Footy.

I am guessing that, like me, you are trying to match CLR and sail CoF. In my experience, although I am not very accurate at all, the pushing in the bath method seems to work. I suspect there are many other factor conspiring to confuse us when actually sailing the beast, like the CLR changing as the boat heels and the fact that when heeling the effective position of forward thrust is no longer on the hull centreline but several inches of to one side. Both of these will tend to turn the boat, the offset thrust will always turn you into the wind - I guess the CLR shift could go either way.

In the end I am trying not to worry too much about it. If the boat keeps turning into wind to an unacceptable degree then just change the shape of the sails and move the CoF to compensate. Although this may mean loosing sail area its a lot better than stalling or continually having to use masses of rudder. I would think you could even move the CLR back by fitting a larger rudder blade.

My experiences at the Footy Grand Prix last Saturday tell me that however competitive my boat was when it was sailing properly ( after the Bourneville crew sorted the sail setting for me ) I lost most of my distance in a race by not moving in the right direction or hitting markers. If you hit a marker the rest of the fleet can be approaching the next one by the time you are underway again :irked: In other words, at least at a novice level, the sailor is probably more important than the boat.



Bob, the hull should have all the gear in and most certainly the rudder fixed in a straight ahead position.
I would say just get it roughly correct with the pushing sideways method and don`t be too concerned for total accuracy.
Rig the boat with the sail plan you prefer and then begin your intensive fine tuning on the water in racing trim.:scared:
Because there are so many factors as explained by others here, it is my contention that sailing is the best way to tune any yacht regardless of size.
Many do not yet understand that the launching of a model yacht is just the first step of a process the can take from three hours to three months to get the best performance from your craft and I often tell newbies that they should not be afraid to make changes after every outing for the first nine or ten times. That is perfectly normal in my opinion.
Having a standard “kit” boat helps somewhat as others have done some of the mods, but even then every build is slightly different and can modify responses.
Your own sailing style can be a factor which will make a difference in the set up. I personally prefer a little bit of “wheather helm” whilst others may want more neutral helm.
“You pays yer money and makes yer choice” as they say. :lol:
Moving the centre of effort of the sail plan is the simplist method of getting the balance right IMHO. :graduate: