I wondered once, “What would we do if we lost the field?” How would you like to fly in a HUGE field, with no obstacles, and nobody complains? Float flying is the answer. Many local lakes are over a mile wide in places, and jet-skis and bass boats make so much noise that nobody even hears the airplanes. Usually, boaters stop and gape at the airshow. I’ve never had a complaint.
Here are some tips for float flying:
I. You need a boat.
2. Really.
3. I’m not kidding.
If you fly from water, you WILL have to go get your airplane sooner or later. Chuck Cunningham mentions flying from small ponds, and retrieving by casting a tennis ball with a fishing rod. Many lakes are MUCH too big for this. The wind will always make a model drift toward the most God-Forsaken inaccessible part of the lake. I’ve flown from a 12’ rowboat and an 18’ ski boat. The rowboat is actually a little more comfortable, because it’s easier to reach the plane in the water. I feel like a pontoon boat would be ideal, with the big flat deck for handling the plane. Donations cheerfully accepted. Don’t fly from salt water unless your budget allows for a new receiver, switch, and servos after each flying session.
Types of planes:
1. High-wings/shoulder wings - Plus: Float on the wing if cartwheeled. Minus: Easier for a crosswind to lift the upwind wing when taxiing.
2. Low wings - Plus: More stable in a crosswind. More aerobatic. Minus:The fuselage fills up with water if you screw up and cartwheel it. This gets your radio wet.
Floats:
If using manufactured floats, select appropriate floats. They’re labeled by length and probable motor size. Rule of thumb: for dual floats, the float length should be 75-80% of the length of the fuselage, from the prop to the trailing edge of the rudder. Be sure the floats are rated for the weight of your plane. There are lots of floats on the market. I use BJ foam floats. They are hotwire-cut foam with a shallow v-bottom. They are light, sturdy, easy to mount, and can’t leak. Mine are sheeted with balsa, and covered with monokote. If you use hollow floats (balsa, fiberglass, blow molded), make provision to get the water Out, because it WILL get in. Attach the floats to your plane. Generally, a supplemental landing gear is needed. For taildraggers, if you use a secondary gear the same as the primary gear, it’ll be easiest to get it all together. If your plane has a tricycle gear, solder up a new nose gear from music wire. It should be T--shaped, with the cross piece going between the floats, and a vertical up through the nose gear mount. Disable the nose wheel steering, but leave the rudder functional.
Float Rigging:
The step of the float should be located directly under the 40% mean aerodynamic chord point. Translation: about a half-inch behind the CG for most .40-.60 size models. This is not critical, and other sources tell you to put the step at the balance point.
The nose of the floats should be a little low. The wing should be mounted about 3 degrees positive to the top of the float (usually about 1/2” higher at the front than the rear).
Be sure to get the floats parallel to the direction of travel, and to each other. (no toe-in).
Check the CG with the floats installed, and correct the CG by altering the weight of the FLOATS. This way, when you install or remove the floats, your plane will still be balanced.
Water rudder: nice to have- helps crosswind taxiing. It Is Not Mandatory. Steer with the air rudder by giving it full travel in the desired direction, and blipping the throttle to get adequate prop blast over the rudder.
If you want to design your own floats, the parameters are available. Chuck Cunningham writes in RCM frequently about float flying. Ed Westwood wrote a detailed technical paper in MA several years ago about float design. Contact the magazines if you wish to get copies of the articles. The definitive Chuck Cunningham article is on Randy Linderman’s website. I have provided a link from the main page of this website.
Launch site:
It’s OK to launch from the bank, if you have a site with a good view of a clear section of water. ( Marinas, Parks, or piers ) Or, you can launch from a boat. The biggest danger in boat-launching is losing your glo-lighter if you start the motor with the plane in the water. If the Ni-Cad jumps off the glo-plug, it’s history. It won’t float. I have caught mine twice, but nearly fell out of the boat doing it. Note: potential safety hazard--lunging to catch a glo-lighter, and getting prop-bit).
Takeoff:
If you’re set up properly, takeoffs should be a procedure of: aim the plane into the wind, advance the throttle, watch the plane first nose up, then plane over onto the step (Technical term: humping). On-plane, the water rudder should be completely out of the water. Then the plane can be flown off with gentle up elevator. If you rigged the floats correctly, they will be level, with the wing getting a good bite of the air. Horsing the plane off with lots of up elevator is not necessary or recommended. A little bit of surface ripple helps-glassy smooth water makes it hard for the floats to break suction and to get up on step.
Flying:
Floats add some lift, and some side area ahead of the CG. Be ready for some trim changes. If your plane is properly balanced, it should still fly controllably, but it will feel different. Some airplanes need more vertical stabilizer--ref.: the subfins seen on Beavers and Cubs. Most any non-scale kit designed for R/C should be fine without additional modification.
Landing:
It’s not tough. Floats are very forgiving. Full-stall landings are not ideal. Land as if you were going to land a taildragger on its mains, on the longest runway you could ever want Line up into the wind, which SHOULD be perpendicular to any waves on the surface. The speed should be just below where the plane will maintain altitude with the fuselage level. If you do it right, you’ll be flying along, and then you will notice a wake coming off the floats. Don’t do anything at this point but close the throttle, and the plane will slow as the water drags on the floats, until it gets slow enough to lose lift and settles into the water. Pat yourself on the back when you do this. If you drop it in a little hard, it may skip or bounce. No big deal. Taxi back to the boat, refuel, and have some more fun. Avoid landing with significant crosswind.. You may catch the downwind float and cartwheel. Have Fun. Fly Floatplanes.