An RC pilot’s information to flying off water
When most RC modelers determine to strive flying off water the query arises, “So which is better: a floatplane or a flying boat?” A floatplane, the place the fuselage is sitting up on two floats, might be simpler to regulate throughout takeoff, however a flying boat, the place the decrease part of the fuselage is formed like a ship’s hull, appears extra forgiving in relation to touchdown and taxiing in windy or uneven situations. A flying boat can also be much less liable to flipping over in tough water than a floatplane is. This applies significantly to turning round after touchdown into the wind. A flying boat is protected within the water in windy situations, however when a floatplane seems of the wind, it doesn’t take an excessive amount of wind beneath a wing or the tail to flip it on its again, particularly for gentle high-wing fashions. Because a flying boat has only a single hull, it wants floats hooked up beneath its wings out towards the wingtips. Also, some flying boats use sponsons hooked up to the edges of the fuselage, which appear like stubby decrease wings on the degree of the waterline. For RC flying, nonetheless, sponsons don’t give enough buoyancy to maintain the wingtips out of the water whereas taxiing crosswind.
For probably the most half, modelers simply need to get some floats and fasten them to their well-proven land aircraft, and that’s what I did after I first began with my gas-powered fashions. Today’s electrical fashions are even higher suited to water flying, and e-power methods make multiengine flying boats a breeze. Relatively talking, electrics are extra dependable than fuel fashions, which may usually have their engines die in the course of the lake after touchdown. But bear in mind, electrical fashions have pace management and most embody a low-voltage-cutoff operate, so you should definitely land with sufficient “gas in the tank” to taxi safely again to shore.
There’s actually nothing like a scale multiengine flying boat for enjoyable on the water. This is Wayne Powell’s Mars. (Photo by Beverly Hudson)
There are a number of fashions to select from, from ARF flying boats to land planes that include wheels and floats. Many are molded out of froth and these have the added benefit of getting good flotation qualities. If they flip over within the water, they received’t sink, they usually normally float excessive sufficient within the water that the radio and energy tools received’t get moist. Although most floatplanes appear to be high-wing designs, you must contemplate a low-wing design. When the wind comes up, high-wing floatplanes are the primary to tip over whereas taxiing; low-wing planes are much less affected by the wind.
Set up correctly, a floatplane ought to have a slight nose-up pitch angle when at relaxation.
Float Terminology When you determine to fly off water, you’ll have to be taught a number of aeronautical phrases. The reference level for measuring the incidence of the wing is the “datum line” of the fuselage. The datum line runs horizontally via (or is parallel to) the horizontal stabilizer. “Wing incidence” is the angle between the wing chord line and the datum line of the fuselage. With flat-bottom airfoils, the “chord line” is just not the decrease floor of the wing; it’s the straight line from the forwardmost level of the wing’s vanguard to probably the most rearward level of the trailing edge. In most flat-bottom airfoils, the decrease floor of the wing is flat solely from the primary spar to the trailing edge, however from the spar ahead, it sweeps up barely. The chord line is normally about 2 levels greater than the flat floor aft of the spar. This angle of incidence is ready and can’t be modified as soon as the wing has been fitted to the fuselage. It is to not be confused with the wing’s angle of assault, which varies enormously throughout flight and relies upon totally on flying pace. Add to the above phrases two extra that apply to floatplanes and flying boats: “beam” and “keel flat.” The “beam” for a single-hull flying boat is the width of the hull at its widest level, normally close to the step; with a floatplane, the beam shall be double the width of every float. The “keel flat” is taken into account to be the underside floor of the hull or floats immediately beneath the middle of gravity. It is the world from immediately beneath the wing’s vanguard again to the step. When the mannequin flies at excessive pace on the water simply previous to liftoff, it’s what we name “on the step,” and it rides on this small keel-flat part of the floats or hull. If the mannequin is blocked up on the workbench in order that the fuselage datum line is parallel to the bench floor, the one a part of the floats or hull touching the bench can be the underside tip of the step. The keel flat ought to angle upward barely, at about 2 levels. Sometimes, nonetheless, it can be set at 0 levels, with the whole keel flat touching the bench. Getting the keel-flat setting appropriate for the floats is akin to checking the incidence for the wings. Forward of the forefront of the wing, the keel gently sweeps up towards the nostril. |
FITTING FLOATS
If you determine to suit floats to your present land aircraft, a number of primary guidelines apply:
• The nostril of the floats ought to protrude in entrance of the nostril of the aircraft by virtually half the size of the propeller.
• The rear of the floats must be about halfway between the trailing fringe of the wing and vanguard of the stab.
• The float’s step must be aft of the mannequin’s heart of gravity, at about 45% of the wing’s imply aerodynamic chord.
Another query usually requested is: “What’s higher: floats with flat bottoms or ones which can be V-shaped? Though flat-bottom floats are simpler to construct, the most effective mixture appears to be a pointy V on the nostril of the float, transitioning to a really shallow V on the step; aft of the step, it ought to stay a shallow V. Flat-bottom floats could fly higher on takeoff, however they have a tendency to skip if not landed easily. Actually, flat bottoms do have rather a lot going for them, however the V bottoms used with full-scale planes had been developed to cut back the danger of injury whereas touchdown in tough water. The V bottoms reduce via the waves, and the fabric used to construct the underside of V-shaped floats might be lighter than that used to construct flat-bottom floats. With a flying-boat mannequin, a flat-bottom hull has the benefit of being comparatively straightforward to take off and land on grass fields—a consideration for modelers who don’t have an acceptable water space close by and need to fly off the grass at their dwelling discipline all year-round.
When a mannequin floatplane is at relaxation within the water, the pitch angle at which it sits is set by the angle at which the floats have been hooked up to the fuselage. The mannequin ought to float in a barely nose-up angle. When floats are added to a aircraft, extra facet floor is added to the mannequin ahead of the middle of gravity than aft. This can result in some directional instability in flight, and a few further fin space might be added to appropriate this unbalance. This might be within the type of a subfin beneath the tail of the mannequin, as utilized in many floatplanes, or small fins (normally 4) hooked up to the higher and decrease surfaces of the horizontal stabilizer about halfway from the fuselage to the tip.
Some fashions fly higher with their facilities of gravity a bit of farther ahead when flying with floats. In this case, add weight beneath the nostril of the floats. It is the farthest-forward level, is out of view, and can routinely be eliminated when the floats are taken off to reinstall the wheels.
You can add floats to only about any kind of mannequin, together with this fun-scale Mustang. In this view, you possibly can see that the floats are correctly positioned, the information of the floats are a number of inches in entrance of the propeller, and the tails of the floats are halfway between the wing trailing edge and the horizontal stabilizer.
Flat-bottom floats, like these outdated Easy Cub floats, are easy to assemble and weigh little or no since they’re made out of froth.
These illustrations from Andy Lennon’s e-book Basics of R/C Model Aircraft Design are a terrific place to begin when studying how you can arrange a floatplane or flying boat.
V-bottom floats are well-liked as a result of they trip nicely in tough water, reducing via the waves with ease.
This kind of flying boat has a comparatively flat backside and will simply be flown off grass. It additionally handles water extraordinarily nicely because it’s outfitted with ailerons and a wing with a low dihedral angle.
FLYING WITH FLOATS
The very first thing to be taught in float flying is how you can taxi. Without a water rudder, it might be troublesome to show a mannequin on the water, particularly when the wind is blowing. It at all times helps to carry the management stick again in order that the elevator is totally up. Small blasts of throttle ought to blow sufficient air over the rudder to make the mannequin flip. If the mannequin won’t flip within the desired path, strive doing a 270-degree flip in the other way. Even with a water rudder, it helps to maintain the elevator up whereas taxiing. It lowers the tail and places the water rudder farther into the water. This applies particularly when the mannequin is fitted with an extension of the rudder beneath the underside of the fuselage that serves as a water rudder. The decrease portion might not be within the water until the elevator is up with the stick proper again.
Before we get into takeoffs, let’s focus on two flight phrases: “attitude” and “angle of attack.” When the nostril is pitched up, as in a climb, the mannequin mentioned to be in a “nose-up attitude”; when the nostril is down, as in a dive, it’s in a “nose-down attitude”; and degree flight is “cruise attitude.” The “angle of attack” is the small angle between the chord line of the wing and the path of airflow, which is a line parallel to the bottom. The angle of assault may be 2 levels in regular cruise at half throttle. At excessive pace, the angle of assault is decrease in order to not produce an excessive amount of elevate, and will even be damaging for a flat-bottom wing. If energy is decreased a bit of in order to fly extra slowly than regular cruise pace, there shall be a lack of elevate if the wing stays on the similar angle of assault. To keep on the similar altitude, elevate is maintained by elevating the nostril barely to extend the angle of assault to about 5 levels; that is referred to as “slow cruise.” If we decelerate much more, you enter what is called “slow flight”; to take care of altitude, the nostril must be raised extra to extend the angle of assault to perhaps 8 levels.
As an apart, sluggish flight with a wing that’s at too excessive of an angle of assault is sometimes called being “behind the curve.” Drag will increase, and extra energy is required to maintain the mannequin from dropping altitude. If the nostril is raised extra, the aircraft will possible enter a stall, the place elevate is misplaced and the mannequin turns into uncontrollable. The stall doesn’t come from lack of airspeed however due to an excessive amount of angle of assault.
You must stroll earlier than you possibly can run, so begin off by taxiing your floatplane to get used to the way it performs on the water.
While taxiing, the float will plow via the water. So as you add extra energy, start so as to add in some up-elevator.
As liftoff pace is achieved, a bit of extra up-elevator could
be wanted.
WATER TAKEOFFS
At the beginning of the takeoff run, apply and maintain full up-elevator and slowly advance the throttle. With most electrical fashions, full energy isn’t mandatory and will make for difficulties in management. The mannequin will plow a bit of with the nostril very excessive after which it can regularly rise within the water; that is referred to as getting “on the step.” Now, cut back the again strain on the elevator stick by about half. If some up-elevator is just not maintained, the mannequin could swerve violently and carry out a water loop. If it does, pull again on the elevator. Learn to look at how the waves transfer again from the nostril of the floats towards the keel-flat part. If the floats are arrange on the correct angle, the wings shall be at a medium angle of assault because the mannequin will get up on step, and the mannequin will gracefully elevate off when enough flying pace has been reached.
Take notice of the mannequin’s angle whereas working on step. The nostril must be pitched up very barely, often known as “the sweet spot.” If it doesn’t elevate off simply, it might require some again strain on the elevator stick or an additional little bit of energy. If the nostril is just not pitched up barely when the mannequin is on the step, there received’t be sufficient angle of assault for the wings to generate sufficient elevate for takeoff. If extra up-elevator is utilized than mandatory, the nostril could pitch up, placing the rear of the floats again into the water, creating extra drag and slowing the mannequin.
Without a slight nose-up angle, the mannequin will obtain a really excessive pace whereas on step and ultimately grow to be airborne solely when it hits a wave large enough to throw it within the air. The pace shall be so excessive that the mannequin will begin climbing abruptly. A well-designed floatplane or flying boat would require little or no further energy to take off from water than from a paved runway. Actually, it has been my expertise {that a} good float or hull design takes much less energy to get off the water than off the typical grass runway.
To correctly arrange the mannequin’s angle (nose-up or nose-down), it might be mandatory to regulate the size of the entrance or rear float struts hooked up to the fuselage. Flying boats are fairly completely different on this regard. There is not any method that we are able to modify the size of the float struts to get the right angle of assault on the wings whereas the mannequin is on the step. It is finished on the drafting board by getting the incidence of the wing appropriate in relation to the keel flat.
A floatplane is kind of steady throughout takeoff as a result of the 2 floats hold the wings degree. With a flying boat, nonetheless, there’s a single hull and floats beneath every wing, and it is going to be mandatory to make use of ailerons to maintain the wings degree throughout takeoff. This helps forestall snagging a wave with a low wing float, which may then flip the mannequin out of the wind. The key to preserving the flying boat’s wings degree throughout takeoff is sweet aileron design and having little or no wing dihedral. A mannequin with vital dihedral, whether or not floatplane or flying boat, is extraordinarily troublesome to maintain straight throughout takeoff. Any crosswind or facet gust will elevate the upwind wing and put extra weight on the downwind float, which, once more, leads to drag that turns the mannequin out of the wind. It’s finest to stick with fashions which have little or no dihedral however have ailerons, with a bit of differential combined in.
Here, you see Mars easily lifting off from the water.
Here, the Solent flying boat is cleanly on step and able to elevate off. (Photo by Beverly Hudson)
With a flying boat, like this Great Planes PBY Catalina, you could use aileron management to maintain the wing degree in order that you don’t snag the water with one of many wing floats.
Since they sit on two floats, floatplanes are steady throughout taxiing and takeoffs.
Once within the air and in your method, proceed easily gaining altitude and attempt to hold the wings degree, which could be a problem if there’s a crosswind.
This form of takeoff is typical when
flying off clean water and never having sufficient place angle. When the mannequin does break freed from the water,
it climbs out abruptly.
WATER LANDINGS
If finished accurately, landings might be straightforward; it isn’t essential to line up with a slim runway and land in a brief distance. But don’t grow to be undisciplined; don’t let your mannequin land simply wherever on the lake. You’re the pilot in management, so you should definitely land into wind, or if there is no such thing as a wind, take off and land parallel to the shoreline. Pick your touchdown path and stick with it. Landing near shore is way simpler for retrieval
if one thing goes incorrect. And don’t fly and not using a rescue boat and somebody to help.
A great touchdown begins with method. A reasonably flat method with a small quantity of energy left on proper via the touchdown is the way in which to go. The method pace must be significantly lower than the cruise pace, extra akin a sluggish cruise. Start by closing the throttle, then making use of only a click on or two of energy. Do not let the nostril drop in order that the mannequin descends at a excessive pace, however apply some again strain on the elevator stick in order that the nostril is simply barely down. This is the place the elevator trim will get exercise in full-scale flying, however with fashions, it’s simpler simply to carry some again strain on the elevator stick.
Learn to guage your airspeed on the method by the angle of the mannequin. The flight path is now downhill, so when the few further levels of angle assault are dialed in to compensate for the slower flight pace, the angle of the mannequin is simply very barely nose-down and even degree. If the nostril is just too low, the pace shall be too excessive; if the nostril is just too excessive, the pace shall be too sluggish. Start the touchdown flare a number of toes above the water, and hold the mannequin simply above the floor, leaving the facility on. Gradually elevate the nostril to maintain it within the air whereas the mannequin slows till it’s barely nose-up within the sweet-spot angle. Then cease transferring the stick again farther and maintain your breath; the mannequin will land superbly each time. Be affected person within the flare; we aren’t in a rush to the touch down. It is important to land at a reasonably sluggish pace with the mannequin in that barely nose-up angle in order that the underside of the step is the primary half to the touch the water.
As the mannequin slows up after landing, it is very important hold the elevator stick again. Failure to maintain the elevator up totally may end up in a water loop. In mannequin flying, it appears that evidently I see extra water loops than I do floor loops. They’re extra liable to occur when the water is clean as a result of there is no such thing as a wind, and in these situations, the pace on the water throughout takeoff and touchdown is greater than when flying right into a wind. Tail-dragger pilots, please notice that we don’t land on water at minimal pace in a full stall as finished in three-point landings. Landings like these are akin to a stomach flop. The sudden splash and slowing up are exhausting on the aircraft and never fairly to observe.
This flying boat has simply touched down, with the water rudder barely touching the water. Smooth and regular is the important thing to drift flying and making good landings.
Reduce energy to your cruise setting and arrange a sluggish gradual method. To keep away from selecting up further pace, don’t drop the nostril excessively.
 About the Author Although he would modestly disagree, Ivan Pettigrew is a legendary electric-model designer who has been concerned with mannequin and full-size airplanes his complete life. Now dwelling in Chilliwack, British Columbia, he particularly enjoys the serenity of flying electrics on close by lakes. Of his many designs, Ivan notes, “I don’t aim to design scale models that will win static awards. My preference is to see them flying in a slow, scalelike manner, so that, in the air, they look like they could be the real thing.” You can discover his plans at ivansplans.com. |