Excellent Roy explanation

I would at least double the area of the rudder as an angled rudder is not as effective as vertical one.
I have a 40 inch long Americas cup model yacht and have done that, and going any further does not help.

The problem lies in the heel angle of the yacht as anything more than 20 degrees you have almost completely lost all directional control. The rudder is angled at about 40 degrees and if you go beyond 20 degrees heel the rudder is acting (as on an aircraft) more like the elevator giving up down control. Turning to the right will have the rudder forcing the bow down.

You will have to sail the model as upright as possible adjusting or removing sail area to accomodate this.

Best of luck.
Roy

You may need to enlarge your rudder.

Here is what Gary Webb said about RC model boat rudders versus their full-sized ones.
“ departure from "scale realism", is a compromise in the interest of the model's steering performance.
The deep rudder works in stronger winds and choppy water better…”

I have found a need to alter the rudder size too from the original.

11 months ago you posted this photo. Is this the same model you are asking about today? Come on fellow model builders let’s help Ross with this project.

Hi Ross, I want to answer you honestly, but I can't focus the image.
Can you take a better photo?
You mean the keel?
Take several photos, including one on-axis.

I know you've already written it but can you tell me how much just the ballast (fin and bulb) weighs please?

Re: ...while the hull and INCREASED number of winches were heavier than estimates. coming out almost even, loss for gain in weight. This will assist in lowering the center of gravity and rolling moment...

Depends.
It depends on the position of the winches.
If they are very low it is better that their overall weight has increased, otherwise not. It's a good thing that the sails are lighter logically.
However, to be safe I would consider them wet.
The sails could always get wet or damp (unless you use waterproof fabric; then you are safe).

Over weight 2.6% yes

The ADVANTAGE I did find in actually weighing the components is that the sails and mast and rigging were LIGHTER than estimates, while the hull and INCREASED number of winches were heavier than estimates. coming out almost even, loss for gain in weight. This will assist in lowering the centre of gravity and rolling moment. As you mentioned, Alessandro, I have changed to a lighter, simpler battery system and picked up some extra weight capacity to cover for the additional winch. Also, the sails measured are the first, test suit of sails, the final sails are a much lighter material.

Hi Ross, looking at your gorgeous model it doesn't seem like she's eaten too many calories, because she's really in great shape and has nice curves.

Congratulations for the accuracy of your calculations. I wrote you a PM about this.

That’s going to be a BEAUTY Ross!!!

Sorry Ross, I only replied to the private message now. I read it some time ago, with the intention of replying as soon as possible and then I forgot.
In my haste I may have made some mistakes, bear with me.

Hi Ross, sorry for the delay in replying to your PM, check your private messages folder now.

the last with mathematics was a beginner calculus in 1974. They gave me a PASS if I promised not to come back.

Ross, you must have the pattience of a saint to work all that out, plus a degree in mathematics and Excel🤓🤓🤓

CE:LCP schooner is truthfully a range 7-12% (I am aiming for 7 and hoping for 12)

Hi Ross agree entirely! The 4% I quoted is for the yacht illustrated it has also worked for a standard Bermuda rig.

I have a schooner on the back burner and thanks for your info advising 7 % I will take note of that and apply.

Always learning! I love it!
Best
Roy

Hi all, nice to do the maths but which is most important, the calculation and solution or constructing a practical model?

When scaling down from a prototype as we know, hulls and sails do not change in proportion to each other. I start from the size of the finished model, i.e. will it fit in my car and also have a place in the house.

So working out a suitable hull size comes first. Dividing the model length into the prototype length gives a scale. The cube of the scale gives a 'scale displacement', in some scales just not practical! All my models have to earn their living at the lakeside.

It is fortunate that to make a model sail, the invisible part under the water can be doctored in many ways.
The models by Glynn Guest have relatively crude hulls and what used to be called 'stand off scale' appearance. I have built several and they look good on the water. I also enjoyed the construction.

So we have to decide where your interest lies? Doing exact calculations for hull displacement is conditioned by sailing in water (and waves) that have obstinately remained at full size.

Hull displacement calculations could have a 10% error but it would not be noticeable when on the water. Bearing in mind that all the mentioned calculations have an end in practical sailing.
If only constructing a display model the numbers are irrelevant!

It reminds me of the radio control of the 1950s where the boat was the least important aspect of the model!
Just my two pennorth!
Roy