Flying From Water

Photos by the author
As seen in the August 2022 issue of Model Aviation.

Building and flying model aircraft offers nearly boundless opportunities for fun, and I expect that quoting Rat’s well-known words has tipped you off to one my own favorite segments of the hobby. Yes, many of my favorite RC flying sessions involve a local lake or small pond, along with a favorite floating model or two. Flying off of water has an appeal all of its own, as well as a unique set of challenges. Balancing these factors makes every water-flying session different and keeps many coming back time and again. I hope that this article will encourage you to give float-flying a try or welcome you back to the fold if it has been a while since you last participated. Let’s start with some basic terminology. Any airplane that flies from water is considered a seaplane. Floatplanes and flying boats are the two primary classes. Many conventional, land-based models can be converted for flying from water by removing the wheels and replacing them with floats. This is typically the easiest way to try flying from water. Most experienced modelers will have an eligible model or two that is well-suited to the mission and perhaps hasn’t flown for a while. Trainers and sport models alike make great floatplanes, as do many Scale designs, such as the Piper Cub, various Cessnas, the de Havilland Beaver and Otter, and the Vans Aircraft RV series.
Rob Caso built this half-size version of Ken Willard’s original 48-inch Drake II. The popular plans remain an AMA Plans Service top seller, despite being published more than 40 years ago.

"Believe me, my young friend, there is nothing—absolutely nothing—half so much worth doing as simply messing about in boats."

—Rat, from The Wind in the Willows by Kenneth Grahame

Flying boats are purpose-built, with the entire fuselage providing flotation when at rest in the water. Small floats mounted near the wingtips provide lateral support. Modelers have flown countless nonscale flying boat sport models throughout the years, with many designs available as ARFs, kits, and building plans. For Scale enthusiasts, the Republic Sea Bee, Grumman Widgeon, Goose, Mallard, and Albatros, the Consolidated PBY Catalina, Short Sunderland, and the Boeing 314 are just a few of the many full-scale flying boats. I fly a variety of seaplanes, with both floatplanes and flying boats in my hangar. For the purposes of this article, though, most of the setup discussion will focus on fitting floats to a conventional model. Floatplanes are not inherently better than purpose-built flying boats, but they do require more care to ensure that the floats are properly installed. The setup and geometry of flying boats is fixed by the fuselage. It is easier to get started flying off the water today than ever before. Years ago, if you wanted to give it a try, you would have to build a pair of floats that were the proper size for your existing model, and then carefully mount them to ensure that the geometry was correct. If you preferred the look of a flying boat, well, that meant building an entirely new model. Today, there are many ARFs and kits on the market for both types of seaplanes. There are several flying boats available, and many conventional, land-based designs also have matched float sets available for them.
Fred Reese’s Electric Kitten is a lightweight model that seemingly flies in slow motion. The plans include float details and are available, along with a short kit, from the Flying Models Plan Store.
Still awaiting its final markings, Zeke Brubaker’s 92-inch, electric 314 Clipper touches down after its maiden flight at Joe Nall. A quick glance at the Horizon Hobby website shows 34 listings for 25 different airframes for which floats are available. These designs range from ultramicro electric flyers on up to 30cc gas-powered models. And, of course, other vendors, such as Balsa USA, Maxford USA, Sig Manufacturing, Extreme Flight, Clancy Aviation, and many more, offer floats for conventional models, seaplane kits, and ARFs. Model Aviation, Flying Models, and other plans sources also sell numerous aquatic designs for those who enjoy building. Suffice to say, there are plenty of options.

Setup and Rigging

Most floats for ARF and RTF models are designed for a specific model and should already be the appropriate size with properly configured struts. As with the original assembly of your ARF, mounting the matched floats should go smoothly, as long as you read and follow the instruction manual. I will discuss the basics so that you know what to look for as you preflight your model before your first flight. There are a few important considerations when it comes to float design and rigging. First, the floats should be approximately 75% of the fuselage length. This relationship has been found to offer sufficient buoyancy, as well as fore and aft stability, to reduce the chance of the airplane ending up on its back. The forward tip of the float should be 2 or 3 inches ahead of the propeller for most models in the 40- to 60-inch wingspan range. That dimensional rule of thumb doesn’t hold for smaller and larger models, but the important detail here is you need some float volume ahead of the propeller to keep it from tripping on an awkward landing. The next critical parameter is the step location. Traditional advice is to have the step at the center of gravity (CG) or slightly behind it. I like to locate the step relative to the CG so that the model will sit level on its floats on a flat surface (such as your workbench) and will remain "nose up" when you rock the aircraft back on the step until the back of the floats contact the bench. Getting this relationship correct will allow easy rotation for takeoff when you are at a lake. Finally, the top of the floats should be parallel with the fuselage. Sometimes the floats will be rigged slightly down at the nose with the fuselage level, but no more than a degree or two. Floats that are angled up at the nose relative to the fuselage will tend to "stick" to the water and require more elevator power to rotate for takeoff. This usually also necessitates more speed. If the model sits with the nose too low when it’s in the water, the wing might actually push the model down as you accelerate, making takeoff even more difficult. Typically, the track or left-to-right separation of a pair of floats is roughly 25% of the overall wingspan. It is critical that the floats are parallel when viewed from both the side and above. These factors are the key to proper float setup and should have been engineered into the installation by the manufacturer and its designers. I’ve detailed them here so that you can confirm that everything looks good before you venture to the lake. Two last details are also worth mentioning. Fullscale floats are mounted as rigidly as possible, with any suspension travel from the wheeled landing gear removed. Rigid float mounting is also important with our models. You might want to consider improvising some more bracing if the float mounting is less than rigid and you find the model to be slightly squirrely on the water. Water rudders are another popular point of discussion. Are they necessary, and how should they be set up? There is no question that a water rudder can be of great help when maneuvering on the water. Without one, you might find yourself at the mercy of even a light breeze while taxiing, and somehow the breeze always seems to know which drift direction is most awkward for you. I recommend installing a water rudder for most models beyond the smallest sizes, which are typically restricted to flat, calm conditions.
This Micro Radian-powered glider was spotted at the NEAT Fair. It features a creative center float modification to allow flying from small ponds.
Paul Kohlmann’s 1:12 Grumman Goose holds the record as the most popular plans ever published in Model Aviation, and for good reason. It is a classic flying boat design, and a great flier. Kits are available from Infield Engineering. The one class of larger models where I usually skip the water rudder is multiengine models. I recommend programming your transmitter for differential thrust for such designs. I have found that this offers the most effective control while on the water and is relatively easy to program with a modern transmitter. If your seaplane is glow or gas powered, ensure that its engine is running as reliably as possible. Having the engine quit when the model is out of reach from the shore is not fun. I’ll share more about retrieval options shortly. My personal preference for nearly all of my water flying is to use electric power. An electric-powered seaplane makes a great addition to a family outing at a local lake, as long as you can secure permission to fly from that site. Electric power eliminates the chance of releasing fuel or oil into the pond or lake, it’s relatively quiet, and motor reliability will greatly reduce the chance of upsetting neighbors or unexpectedly having to rescue the model.

Weather Considerations

I have briefly mentioned wind and weather conditions, and you will soon find that you want a light breeze when flying from water. A stiff breeze can disturb the surface enough that the waves preclude safe operation and can make retrieval challenging. Most of my float-flying takes place either first thing in the morning or just before sunset—typically the calmest parts of the day. This timing also supports choosing electric power so as to not disturb the calm.

Flying Sites

As when flying from land, you will want to choose your flying site carefully and make sure that it is suited to your choice of model. A large pond or lake might allow flying over the water throughout the flight. If that isn’t possible, it is important to visualize your intended flight pattern and ensure that you have enough clear area on the shore to allow a comfortable flight pattern. It is quite common to make a landing approach over the shore, and then settle onto the water after you cross the shoreline. Be wary of flying from a river. Only those with slower-moving water are suitable. Any apparent current will make retrieving a model more challenging. Please be mindful of others when selecting a flying site. You do not want to endanger any people or property in the area. As an example, we have an ideal flying site in my hometown that happens to be in a public park. Throughout the warmer months, there are typically a hundred or more people picnicking or swimming during the day, and I restrict my flying there until just before the park closes at sunset. There are usually 2 or 3 months before and after the swimming season when the weather cooperates and flying is still practical. Park-usage conflicts rarely occur during this off season, allowing more flying than during the summer months. And don’t worry. When you have received permission to fly from the private landowner or a municipal representative, your AMA coverage will not be affected.

Rescue, Retrieval, and Now What?

Modelers who fly off of water for any length of time will need to rescue a stranded model at some point. Whether an internal-combustion engine quits, or you lose track of your battery usage, the result is the same. Murphy’s Law inevitably will send your model drifting across the lake or pond toward the least accessible section of shoreline, regardless of what the wind was doing at the start of the flight. Modelers have developed an ingenious variety of rescue techniques throughout the years. If the aircraft is reasonably close to shore, you might be able to reach it by hand or with a stick. Many will carry a fishing pole in the car, with some sort of weight on the line to allow casting past the model and hopefully snagging it while gently retracting the line.
Another flying boat, albeit slightly unconventional, is Harry Stewart’s Splash E. It is a great flier and its semisymmetrical wing offers unexpected aerobatic capabilities. BMJR Models offers this kit.
The author’s Sport Scale Albatros B1 accelerates on step and is pitched slightly up while waiting for liftoff. Plans and short kits are available from the Flying Models Plan Store. Other fliers use simple model boats that can pull a line out and around a stranded model if their casting skills are not up to par. Making a turn or two around the model then heading for shore can often drag the model home. The best option for longer retrievals is some sort of boat. An aluminum skiff with a small outboard is perfect for float-flying events, but you need not go that grand. A simple rowboat, canoe or kayak, inflatable craft, or even a paddle board will easily do the job. Regardless of your choice, make sure that you comply with all local laws concerning life preservers and vessel registration. Under no circumstances should you attempt to swim after a model, regardless of how easy that might seem. Wading into the water a bit is one thing, but actually swimming is fraught with hazards. If there is any unfavorable wind, it can blow the model away faster than you are likely to swim. It is too easy to get tired or struggle to push the model back if you do reach it. My local lake has a gently sloping, sandy bottom and, in such cases, wading in after a model is quite practical. My personal limit varies depending on the season and my clothing choice for the day. I have waded in slightly past my waist while wearing a bathing suit in warm weather. After the leaves change color though, if I have to go in much deeper than my knees, I start to look for a retrieval boat. Dunking your model is a concern, and I strongly recommend that you only fly from fresh water. Saltwater and electronics simply do not get along. If your model does end up on its nose or upside down in the water, you will likely find that letting everything dry out for a few hours or overnight will restore it to operation. An engine that has been submerged needs a bit of special care. Remove the plug and drain any water that you find inside. A hair dryer makes quick work of any remaining water, and when it is dry, you should immediately lubricate the engine with a light oil.

Flying Technique

Anyone who is comfortable with taking off and landing at the field should be fine when flying from water. Indeed, there are a couple of unique factors that should make flying from water easier. Most obviously, the surface is more forgiving than the ground. I’ve seen many dramatic "splashes" that would have rendered a wheeled model unflyable. If the model is upright, you might find that you can still taxi back to the shore to inspect it before your next attempt. Slightly less obvious, a water runway is always perfectly level. It could have some surface texture because of the breeze, but at least it won’t be sloping. Taking off directly into the wind is not a problem if the site is large enough for a clear flight pattern. To determine the wind direction, taxi out into the water a little, and then go to a low idle on the engine or shut down your electric motor. Your model will soon weathervane directly into the wind, indicating the ideal takeoff and landing direction. If there isn’t enough of a breeze to align your model, and take off and land in any desired direction. The takeoff run consists of three phases: the initial acceleration with the floats in the water, transition to planing, then accelerate to takeoff speed. Lightweight or overpowered models can often get off the water so quickly that there is little concern for technique. I’ve flown some models that will jump off of the water in just a couple of feet. Making an extended takeoff run will require a bit more finesse. I typically start my takeoff run by holding full up-elevator and slowly advancing the throttle. A count of three or four from idle to full power is a comfortable rate for most setups. As the model accelerates, you will see it lift until the floats are skimming along the surface like a water-skier. Relax most, if not all, up-elevator as the float lifts to the surface, and then use a light touch on the sticks to keep the model balanced on the step as it accelerates.
Not every flight goes according to plan, but the Joe Nall Week organizers provided this rescue boat. A bit of drying out restored this glow-powered model to service.
Seen in the sunrise calm at Joe Nall, a 12-foot, gas-powered Telemaster taxis on the lake at Triple Tree Aerodrome in Woodruff SC. The floats are riding deep in the water before the pilot accelerates for takeoff. Keeping the fuselage and floats level will minimize aerodynamic and hydrodynamic drag during this stage. After the aircraft gains a little speed, raising the nose slightly more should lift the model into the air for the start of the flight. My favorite part of float-flying is perfecting my landings as the water bears witness to each arrival. The ideal landing is a gentle kiss and faint pitter-patter of the floats as you flare at just the right rate and altitude to effect that elusive perfect touchdown. Any bounces are betrayed by the resulting patterns on the surface. It is hard to convince your friends that they missed a perfect landing when they see large rings growing in line with your wake. When you get it just right though … oh, the satisfaction!

Join the Fun

There is still plenty of time to set up a floatplane of your own for this flying season, so don’t procrastinate. You might find that you are kicking yourself for not joining the fun sooner. Many clubs and some of the larger events offer float-flying opportunities throughout the year, so check the AMA Sanctioned EventCalendar and ask around for local options. To get you started, I know that the Southeast Electric Flight Festival, Joe Nall, and the Northeast Electric Aircraft Technology Fair have suitable water runways available. There are also numerous float-flying videos on YouTube that will give you a great look at this fascinating aspect of the hobby. And no, float-flying is not just for the RC crowd. Although less common, both Control Line and Free Flight models can be flown from the water, but I will leave those discussions for another day. In the meantime, come join us at the pond! SOURCES: