A beginners' guide to RC Sailboats

Radio Control Boat Modeler, Feb 2001 by Houle, Tom

SAILING AND RACING

In the June 2000 issue, I discussed choosing the right sailboat, boat size, whether you should build or buy, radio installation, sailing terminology, rigging, and sails. Now we'll move on to sailing and even racing. If you're just joining our discussion, I suggest you review the June issue's article.

GETTING TO THE POND

A sailboat that's 40 inches or less long will fit into a mid-size four-door sedan in which the rear seats can be folded. Without the mast and sails, it will fit into a two-door hatchback. After removing these, I was able to fit a 72-inch America's Cup-class hull and its 96-inch mast into my Taurus sedan. It can be done. Don't let hull length dissuade you from going with a larger boat.

At the pond, I always walk around the boat while it is still in its cradle. Even if I've done nothing to it since its last outing, I do a pre-sail check. A stiff breeze can wreak havoc on weakened stays, shrouds and sails. I begin by checking the deck, mast and spar fittings. Is everything still tight? Are there any loose screws? Are the shrouds snug-neither loose nor guitar-string taut-and is the mast perpendicular to the deck? I check the lower ends of the shrouds to make sure that the devises are securely clipped to the deck-mounted chain plates and that the shroud ends are tightly crimped. I have had shroud crimps be pulled out in a good blow; a shroud failure while on the water means your entire sail rig will go over the side. Check the shroud ends carefully.

Check the jib swivel, too-another high-stress area. Is the masthead crane secure? Are the jib stays and backstays secure? Adjust the boom-vang tension to ensure there is no vertical play in the main boom. The main boom should swing inward and outward as freely and as effortlessly as if the goose neck were on ball bearings.

Take a good look inside the hull. Is the radio board in place? Are the battery and receiver where they are supposed to be? Are the sheets clear and free? Are the knotted ends of the main and jib sheets still tight? I use woven fly line for my sheets; that tries to "unknot" itself, and it will, if you let it!

Turn on the receiver and do a range check from 40 to 50 feet away with your transmitter antenna collapsed. There shouldn't be any servo jitter. I check to make sure that, with the rudder stick in neutral, the rudder is perfectly in line with the keel. If it isn't, use the rudder trim to align the rudder with the keel fin. Any misalignment will hurt your boat's performance on the racecourse. If all is well, close the hatch securely, and make sure the hatch seal is in place; a loose hatch will admit water and will even fly off the hull. (It has happened to me!)

TUNING UP

Sailboat performance is the combined product of several distinct sail settings that will be dictated by the weather. Your first day at the pond will be a tuning session during which you'll set the boat's critical adjustments approximately.

* Start by sheeting the sails hard in over the deck.

* Adjust the main sheet bowsie so that the aft end of the main boom points directly toward the corresponding aft comer of the hull. As shown in Figure 1, adjust the jib boom bowsie so that its aft end points directly toward the shroud and chain plate on the same side of the hull. These settings place the jib boom slightly farther out than the mainsail to create the required slot between the jib and the main. The jib boom should never be sheeted farther inward than the main. To do so would back-wind the main and spoil performance. A second rule for jib-to-main setting is that the jib boom should be set approximately 5 degrees farther out than the main boom, and both booms should be sheeted in hard.

Backstay tension is a must for maximum performance; it controls the shape of the mainsail and the jib sail. Loosen the jib stay at the mast crane. Then adjust the backstay bowsie, tightening the backstay until the mast is bent backward just enough to match the luff curve in the mainsail. This tension adds "belly" or convexity to the mainsail, and that dramatically improves windward performance.

* In Figure 2, the jib and clew outhauls are shown adjusted to a depth of 10 to 15 percent at the foot of the sail. If the mainsail foot is 12 inches long, the arc, or draft, at the foot of the sail should be 1 to 1.5 inches deep. Higher winds require a flatter sail; lighter air requires the fullest setting.

* Having a flattened clew outhaul setting is like having an airplane with a super-thin jet wing designed to fly at supersonic speeds. A fat clew outhaul setting is comparable to a thick ultralight wing designed to fly at very slow speeds. Rather than take up any more space on reviewing the fluid and aerodynamic forces associated with the sails and the fin keel, I refer you to the American Model Yachting Association (AMYA) website at www.amya.org. There, you will find lots of information on sails and how they work, and you'll also be able to find out whether there's a model-boat club in your area.