The Art of RC Scale Model Boat design.

Many people believe that a radio controlled model boat has to be made of plastic or fiberglass in order to float and often they spend a lot of money buying a Ready-to-race model boat.

But nothing can be further from the truth! The age old art of ship building is a mere rib cage fitted with curved planks and that is then painted with pitch or bitumen to make it waterproof.

Nowawdays, we call this form of construction a plank-on-frame building process. And as most of the wooden model boats we sell, are made for this form of construction, it is the ideal model to covert into a radio controlled model.

Firstly, you get a kit with all the detail in the box, from the hull to the parrot on the pirate’s shoulder, the kits have everything the real ship had. All you need to do is build it.

However, the trick is to know when to stop and wait.

Some of the models we have are labeled as RC Ready. This simply means, it is possible to convert them into Radio Controlled models, based on the simplicity of the hull and the primary driving method. We would not recommend turning a three mast galleon into a RC model, although it has been done. Rather take the easier to build Work boats, Trawlers and sail boats and turn them into a RC model.

Firstly, you have one of three options; Sail, Steam or Electric driven models.

Sail is the cheapest, but it can be tricky in terms of rigging.

Next up is our electric powered models. The capital outlay for the drive train could be as high as R2500.

But the top of the range is the Steam models. A ready made steam boiler with shaft and propeller, will be around R10 000.

Then its a matter of details…

If you decide on electric, do you want to add “fake” smoke and engine sounds? Only a few modellers do that, and honestly, it does look pretty damn awesome. But it is an additional non-essential expense.

On the essentials…

Regardless of your choice of driving force, you will need a rudder and rudder servo and a battery with charger.

Needless to say, you would also need a transmitter (Radio) and receiver, which you can get from R500 upward.

If you decide on sails, you will need a sail winch, and here are two options as well. You can get a real sail winch, which rolls the rope on and off a reel or drum. Or you can have a long lever that pulls and release the rope. The former is the more effective way, but also more expensive as the sail winch is around R1 450. It all depends on the travel of the boom or jib you need.

If you decide on electric power, you would need a motor, a speed controller a propshaft and a propeller. In between you may also need to fit shaft inserts and couplings.

It does not matter which route you follow; one thing is for sure – You will have lots of fun.

There is one tip we must share with all prospective model builders:

Design and build your model to fit the available parts and components.

Don’t start building and then look for parts that will fit the model. You will most likely not find them and will have to get it custom made. In stead of the added cost, why not redesign the layout?

If you mounted the motor and need a 500mm shaft, know that it would be cheaper to move the motor backward so that you can use a standard 450mm shaft than to get a custom made 500mm shaft.

Also keep in mind that the thickness of the shaft and its length are related. You don’t get 3mm shafts in the same length as you do with 6mm shafts.

With propellers it can be just as complicated.

You get props with two blades and some with 7 blades like on submarines.

Then you get “L” and “R” props. In other words they rotate clockwise or counterclockwise. This is important to know when building a double engine boat. You want the two props to rotate outward. Left side goes counter-clockwise and the right side goes clockwise. There is no hydro-dynamic reasoning for this, and you can do it the other way around too. The purpose is to reduce steering torque caused when both props rotate in the same direction.

Lastly, you get dog drive fitted props and bullet fitted props. Most speed boats have dog drives which keeps the prop from rotating on the shaft and becoming dislodged as the prop has smooth hub. Some props do however have threaded hubs.

Other considerations are prop diameter and pitch. The diameter is important as you need a prop that won’t cut the hull open. It must fit and clear the hull and rudder. If you are building to scale, it is important that the prop fits the original design drawing and not be bigger than the real prop in relation to the ship itself. A larger prop does not necessarily make a boat faster or give it more “thrust”.

The last bit to consider is the pitch. This is important for speed or thrust and it is the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood. For example, a 21-pitch propeller would move forward 21 inches in one revolution. It is thus distance per rotation. The higher the pitch, the more thrust the prop produce. Thrust is a unit of power and speed is influenced by the hull design, drag and total weight of the boat.

It is particular important to keep a balance between the torque of a motor in relation to the hull. You don’t want your boat to capsize the moment you throttle up. Remember that both the prop and motor cause torque that will make the boat list to one side if both rotate in the same direction. Rather then select a lower torque motor with higher rpm. Most boat motors sold by the hobby industry are built according to hull length. Using drill or printer motors will have a negative impact on your model’s acceleration from stand-still. (Or as some folks do, fit a stabilizer fin on the side of the hull to keep it upright. And if you’re really fancy, you can add a servo to control it remotely. Just remember you are adding more drag due to over-powered design.)

 

Leave a Reply