RC sailboats can be divided up in three main categories:
Most kits and RTR (ready-to-run) model RC sail boats are best categorized as RC sport scale. This category is a happy medium between full-blown scale models and RC racing yachts.
Some have become so widely distributed that new racing classes has been formed around them. Good examples are Graupner's Micro Magic and Kyosho's Fairwind.
They are usually semi-scale of modern cruising yachts or made to resemble America’s cup sailboats.
The lower cost models come with ABS hulls, whereas the higher end models come with more durable fiberglass hulls. Drop keels, aluminum masts and Dacron sails are most common.
If you want to get into RC yacht racing there are a number of classes to choose from. Each country has a governing body (American Model Yachting Association (AMYA) in the USA, Model Yachting Association in the UK) under the International Model Yacht Racing Union.
As with full size regattas, RC model yacht racing face some of the same issues. Entry rules for competitions typically follow depending on if the class is Open or Closed Design.
What these classes have in common is that the boats are not identical - instead the rules are made up like a mathematical formula. The good thing that brings is that the challenge is three-fold – design, construction and sailing the course.
The disadvantage is in that the rules for some classes can be complicated. Some classes have gained in popularity precisely because the rules fro previously established classes were so hard to understand.
Examples of some popular open design model yacht classes:
All entries have to be the same design. Some are kits from a single manufacturer others are open to home built model boats.
We're talking about scale model sail boats that actually use its sails as the main means of propulsion. RC scale sail is called minisail in continental Europe. The vast majority of sailing scale model boats is scratch built. There are a few kits - Billings Collin Archer RS-1 comes to mind.
The prevailing problem with scaling a sailboat is that stability doesn’t scale linearly with size. The result is that model boats will always be significantly less stable than the boat or ship it was modeled after. Left as is, it may have detrimental effects on the model’s sea keeping abilities. There are ways to minimize the effect.
A smallish boat built to a large scale is more stable than a large ship to a small scale. For instance, say you can only transport a model 1m long. Building a model of an 8m cruising yacht at 1:8 scale will be more stable than a model of the USS Constitution at 1:48 scale. This is true even if they end up weighing the same and being the same length. I bet the yacht will be a much better sailer too.
Bigger is always better too, when it comes to scale RC sailboats. Try and build the biggest model you can get away with. A larger model will be more forgiving on construction techniques, materials and the weight of components. The finished model will also be faster, a better sailer and handle stronger winds than if it was built smaller.
Making considerable effort to build light is always a god habit. The higher up a part or component is located, the more important this becomes. For instance, rigging components need to be light weight.
Other factors are beam and draft (width and depth for landlubbers). A wider and deeper hull will naturally be more stable than thin and shallow.
There are two tricks to increase the stability of model boats artificially:
By adding a drop keel you can bring the center of gravity down while adding profile area. The greater under-water profile helps against drifting sideways. All sailboats drift downwind some, because the surface water moves with the wind. The lower boundary-layers of a body of water are influenced less by the wind than layers closer to the surface. Therefore, the deeper any extension of the hull is, the less drift.
Typically a boat with a drop-keel also needs a larger rudder. A good guideline is to make the rudder area 10-12% of the total submerged hull profile.
Some builders rather build the boat hull slightly out of scale than add a drop keel. The most bang-for-the-buck is to deepen the hull. Same rule apply about the rudder (rudder area = 10-12% of total submerged profile). You could technically make the hull wider, but the effect is not as great.
Any change in the submerged hull profile need to maintain the same geometric center to balance the center of effort on the sails. Naturally, if you know what you are doing, the sail and rig can be modified also.
Generally stay away from lateen rigs, multi-hull, centerboard designs and square riggers, at least until you have become an experienced RC sailboats captain and/or builder.
RC Sailboat Models