Remove each servo from the servo the day, then treat your engine with CHUCK CUNNINGHAM tray and remove the servo arm from some after-run oil. When looking at Float Flying - Spring is about to the servo. Drape a piece of plastic your dunked aircraft, make sure that get started in many parts of the coun- wrap over the gear that protrudes the wings and stab did not take on try, and with spring comes daylight from the top of the servo, then replace any water. Chances are that some got saving time. giving us longer hours in the servo arm on the gear, forcing the into the covering. Poke a couple of the afternoon with flying time firmly thin plastic wrap over the gear. Wrap holes with a pin and drain out all of attached to the end of the day. Why the servo with the remainder of the the water. Nothing will mess up a not plan ahead this spring for some plastic wrap, again tying it with a good flying model more than having a flying from a water site. This is one twisty at the servo lead. Do this same wingtip full of water — almost a sure phase of R/C action that has gained a operation to all of the servos, re- thing to cause another dunking on the lot of new fans in the past four or five install in the servo tray, connect back next take-off. years. It is time to delve back The prop that you use on to some of my earlier col- your aircraft is also very umns and once again talk important. A wood prop is about taking the secrets out not good when it comes to of float flying. flying from water. Spray Getting your aircraft ready can eat up a wooden propel- to fly with floats attached is ler more rapidly than you not hard to do, but there are can realize; therefore, a several things that need to plastic prop is a necessity. be considered when flying What generally happens is from and landing on water. that the lake waters get a Just about any aircraft flown little choppy, you gun the from water will take a dunk- engine for take-off and the ing sooner or later. A high floats cause a lot of spray to wing cabin job is the most get kicked up into the prop, likely to be flipped over by and your aircraft is hur- the wind because the wing is located dling across the water trying to pick far above the water. Because the wing to the receiver, and you've done about up flying speed. Something seems is located high on the model, when it the best that you can do to protect the wrong to you. but you're not sure is flipped over by the wind it floats on radio equipment. what, so what the heck. haul back on the wing, keeping the fuselage, in- In case of a dunking, always re- the elevator stick and get that bird in cluding engine, radio, battery, and move the wing and dump out any wa- the air. So back you haul, the aircraft servos high and dry most of the lime. ter that may be trapped in the fuse- struggles into the air. then flops back A shoulder winged aircraft is harder lage. Look at the equipment to be sure like a dead fish. When you finally get for the wind to flip, but when it does, that no water is in the plastic the aircraft back to shore. you see that the radio and servos tend to stay dry. wrapped items. Your engine needs im- what once was a pretty, well balanced The engine usually gets wet. A low mediate attention when dunked to en- wooden prop is now just a splintered winged model is harder for the wind sure that the bearings do not have a stick. It's no wonder the aircraft to flip, but when it docs, the entire fu- chance to get rusty. Pour all of the would not get airborne. selage generally winds up in the wa- fuel out of the fuel tank. Chances are When you install floats on your ter, with everything getting wet. that in the dunking, some water got model for the first time, you may not The first thing that we need to do is mixed in with the fuel: do not put this realize that the weight distribution of to waterproof the equipment as much contaminated fuel back in your fuel the floats will change the balance of as possible. Start with the battery can, dump it out! Take the glow plug your aircraft. Generally, the weight pack. wrapping it in plastic wrap, out of the engine, turn it upside down will be added aft of the center of bal- then a layer of closed cell foam, then and drain all of the water out of the ance, thus causing your model to be- wrap it again in plastic wrap with engine and muffler. Then with the come tail heavy once the floats are only the lead sticking out. Use a plow plug still out, put a -starter to mounted. Prior to removing the land- 'twisty'' to cinch up the plastic around the engine and blow all of the rest of ing gear. and with the fuel tank dry, the lead. The same for the receiver the water out of the glow plug hole. locate the balance point of your model. wrap with plastic, then foam, then Just a thirty second application of the If you've been flying this particular plastic again, tying all of the servo ca- starter should clear it out. Blow the bird for some time, you are used to the ble with a twisty. Let the antenna exit water from the glow plug, re-install it way it flies at this balance point. Once from the other end of the receiver in the head. fill the lank with fresh you have completely attached the pack, and tic off this exit with a fuel. then fire up the engine and let it floats, complete with whatever water twisty. Servos are a bit more difficult run for several minutes until the oil in rudder system you are using, install to waterproof. Futaba makes servos the fuel has a chance to be distributed the wing and see where the aircraft that are waterproof, but we can do a around the engine. If you're going to now balances. Bet you dollars to bit of waterproofing on a standard make another flight, the engine will donuts that it is now tail heavy. Bring type servo. be fine. If that was the last flight of the balance to its former location with PAGE 2 the addition of lead weights added to the floats, not to the aircraft. Once you have added the correct amount of weight to the floats, be sure that the weight is permanently attached. Now you will be able to switch back and forth from land gear to water gear without worrying about the balance of the model. Again, I've seen too many fliers overlook this balance pre- caution and wonder why their aircraft either flew very poorly or crashed. Most blamed the poor flying on the floats, never realizing that it was a simple matter of C.G. location. Engine power is another considera- tion, most of our aircraft today are pretty much overpowered. If your model is overpowered as a land plane, it should have no trouble when con- verted to a water plane. But. if your model just barely staggers into the air from a grass or paved runway, then it's going to have a tough time trying to take off from water. If in doubt, go to a larger size engine. The main rule when taking off from water is to never force the take-off. If your aircraft isn't up to flying speed when it is running on the water, then a forced take-off can be deadly. Re- member that the addition of floats to your model has increased the weight, and of course the wing loading and the drag a considerable amount. If you added that much weight and drag to an aircraft taking off from a paved runway, you would realize very quickly that take-off speed needs to be much higher to prevent a stall. One last thought on making a take-off. Flying from a glass smooth pond seems like an ideal situation; how- ever, it's almost impossible to lift off of that glass smooth surface. A take-off is much easier when there is a slight ripple to the water. The ripple breaks up the suction between the water and the floats. If you're flying from a glass like surface, taxi out. then make a big circle in the water, letting the turbu- lence of your taxi maneuver break up the water. Then turn into the wind, shove the throttle stick full forward, and bounce off over the ripples that your aircraft created. Designing And Building Floats There are several types of floats for use on aircraft. All full size airplanes use V-bottom hulls on their floats. Some early aircraft such as the Sop- PAGE 3 with Bipe used flat bottom type floats, not be correct is if the aircraft for sions. Using our 36" long float, we find which act more like water skis, while which you are designing floats has an that the overall depth of the float will the V bottom acts more like the hull of unusually long nose (the distance be 8% of the length or 2.88" (let's say a boat. In model type aircraft either from the leading edge of the wing to 3"). The width is actually a factor of float design works well. The flat bot- the back of the prop). Some of the the overall weight that the floats have tom float is much easier to construct. smaller trainer type aircraft do have to support, so use the table in Figure and will let your model fly from, and an extra long nose, so the next thing 1. For our example we will use a land on, water very easily. The V- that we need to consider is the loca- width of 4". The nose and tail up- bottom looks more scale, but is a bit tion of the balance point of the air- sweep angles are as low as you should harder to build. However. the basic craft. This should always be shown on go. Increasing the aft sweep from 3° to layout of the float styles is still the the plans, but. you should also check 5° will allow the aircraft to break the same. The overall length, location of the balance point on your aircraft to water suction easier but also the aft the step etc.. will be the same for both see if your model (with no fuel in the end of the aircraft may ride lower in the flat and bottom type floats. Gener- tank) balances at the same point. It's the water. I have used both angles ally speaking, floats constructed from possible that you have been flying and think that in the future I'm going Styrofoam are easier to build, and with the balance point different from to stick with about 4°. more damage proof to use than the the designer's location. Mark the bal- Now that we have arrived at our floats that are built up from balsa. It ance point on your model for use now. basic float design we need to decide on all depends upon the type of aircraft and in the future when we are going constructing the floats from balsa or you are going to be flying from water. to rebalance after the floats have been foam. Of course, you can use either If it's a real scale machine then you installed. The step of the float should material but since I'm very partial to should build floats that duplicate the be located right on the balance point, foam. that's what we will talk about full size aircraft's floats. If you are go- or not more than a 1/2" aft of the bal- this time. There are two reasons why ing to be flying from water for the fun ance point. If your model is one of the I like to use foam. The first is that it of it, and you're going to put floats on long nose type then our 75% float is much easier and faster to use. while your normal fun machine, then the length may not be long enough. the second is that you cannot poke a flat bottom foam material floats will Normally, I use a figure of 53% of hole in a foam float allowing it to Fill be easier and faster to build, and will the float length forward of the step lo- with water and sink the aircraft. I've give you excellent service. cation, while the length aft of the step seen this happen several times. The The starting point in designing the is 47% of the total float length. It is aircraft was not lost, but it sure got floats that we are going to use is to de- very important to have the nose of the wet, and it sure ended a day's flying termine the length of the fuselage of floats at least several inches forward early. You may think that the only your aircraft. I always measure the of the prop on your aircraft. If the way to work with Styrofoam is with a fuselage length as that distance from floats are not extended beyond the hot wire and templates. You can go the back of the prop to (he hinge line prop. then the model lends to rotate this route but then you need to build of the tail feathers. Some aircraft down under power, first swamping templates for each size set of floats have a different hinge line for the rud- the floats and then the aircraft. Draw that you wish to build. der and elevator, so in that case, use a line on the plans for your model par- Rather than do this, use a saw to the hinge line farthest to the rear as allel to the "normal" fuselage line; not cut out the floats. If you have a band the measuring point for the fuselage the thrust line nor the chord line, but saw this is very easy to do. 1 use a length. the fuselage "line." On this line locate metal cutting blade on my band saw The float length should be at about the balance point. Then measure for- for just about everything, balsa, pine, 75% of the fuselage length. This meas- ward along this line to a point that is metal and foam. It always gives a very urement isn't cast in stone. The 53% of the float length. In our exam- smooth cut in any material. If you length can vary from 70% to 80% with ple we are using an overall float don't have a band saw, or a friend no problem. If you're trying to deter- length of 36", 53% of this yields about with one, then you can use a regular mine what length floats, then work in 19". Locating the step 1/2" aft of the hand held saw, or coping saw to cut the 70-80% range. If you're going to balance point yields a float length line out the float. With a hand saw you build your own floats, then use the that ends about 21/2" ahead of the will have to do a bit more sanding. but 75% figure. It doesn't make any differ- prop. Just about perfect. If your long- it's still pretty quick to do. It is also a ence to the overall float length if your nosed model has the float nose just very good idea to wear a dust mask aircraft has one wing, two wings, or even with the prop. or a bit aft of the when sanding Styrofoam, or whenever ten wings, the float/fuselage relation prop, extend the float line until its for- you are doing any type of sanding. stays the same. For example, if the fu- ward point (or the nose of the float) is After the pair of floats are cut in- selage length is 47", 75% of this is 35”. at least 5% of the fuselage length stall the plywood stiff back to the top So, what the heck, round it off to 36". ahead of the prop. Leave the tail of the foam. Use a strip of 1/4" ply- Some commercial floats are available length of the floats alone at 47% of the wood about 5/8" wide, running the full in this length, so don't pick at nits. original float length. length of the float for .60 and .90 pow- buy whatever is close. Same for mak- Once you have determined the over- ered aircraft. 1/8" ply will do nicely ing your own. standardize a little bit. all float length, then use the diagram for .40 size and smaller aircraft. If you The only time that this length might to lay out the rest of the float dimen- don't have any long pieces of plywood, PAGE 4 then use 1/4" x 1/2" spruce or pine. If aft of the wing. The final item we need to discuss is you want to build a pretty set of floats A 1/8" or 1/4" piece of plywood glued a water rudder. There are two ways to then you will need to cut a slot in the to the structure is all that needs to be construct a water rudder. One is to at- top of each float large enough to accept added. tach a rudder to the aft end of either the stiff back piece. This slot can be Extra braces are generally not one, or both floats (best for windy con- cut with a knife, or a table saw. You needed as the float load at this point is ditions), while another simple method can also make a heavy copper wire fit- pushing against the brace, rather than is to attach a small water rudder di- ting just the right slot size and fit this trying to pull it from the structure of rectly to the rudder on the aircraft. into your soldering gun. if you have the fuselage. Don't overlook a water rudder. You are the type that has multiple heads, and I like to set my floats up so that the going to need some other steering melt a slot into the foam. If you really wing chord line is positive to the top method than just an air rudder. don't care about a perfect look, and line of the floats. About 2o positive is The rudder attached to the air rud- just want to go flying, then glue the good for most aircraft. Measure this on der is the type that I like to use. A stiff back to the top of the foam float the plans for your model to see just small piece of tin can material or a and forget the slot. Use epoxy glue or how much positive this will amount to. piece of brass soldered to a piece of Elmer’s Probond polyurethane glue. Mount the main gear to the floats, 1/16" diameter wire is all that is The next step is very important, then shim the fuselage or block it up, needed. A piece I" wide x 2" long is and should not be overlooked. Set the so that you can measure the amount of large enough for the normal .60 size floats on your workbench and position positive that you have for a correct aircraft. Be sure to set the water rud- your aircraft on the floats so that the setting. Then make the aft strut, or der so that it is immersed in the water step is located where you determined forward strut for a trike gear job, to at taxi speed, but is clear of the water on the line you drew on the plans. the correct length. If you mess up and when the model is up and running on Mark the location for the existing get these struts just a bit too long or the step at takeoff speed. When the as- landing gear, and whatever aft or for- too short you can compensate for this sembled aircraft with floats attached ward brace gear will contact the stiff by adding blocks on top of the floats is sitting on your workbench with the back. Remove the fuselage and drill a between the gear and the stiff back. float tops level, make the length of the 1/4" hole through the stiff back and The idea for using positive in the wing water rudder wire so that the bottom into the foam float a total of 2" deep is because you want the wing to lift of the water rudder does not stick for each hole. A minimum of four holes the aircraft from the water when on a in each float. Be sure not to drill takeoff run. Nothing is to be gained by through the float, but if you do, simply an aircraft that motorboats all over fill the hole from the bottom side with the pond because the wing is not lift- scrap foam and epoxy. Fill each hole ing the airplane from the water. Re- with epoxy and insert a 1/4" x 2" dowel member the friction or adhesion of the in each hole. float to water is mega times higher You may need to tap these dowels than is the adhesion between a wheel into place with a hammer. These dow- and a paved surface. Look at the area els lock the stiff back to the foam. If of the wheel in contact with the you neglect to do this then do not be ground compared to the total area of surprised when the stiff back rips the float in the water. away from the foam in a hard landing. Covering foam floats can be done in If you're building long floats for a lar- several ways. You can cover the entire ger aircraft, then add one more dowel float with 1/16" balsa wood, then put at the forward and aft ends of the on light glass cloth and epoxy resin float. and paint. Or. you can cover the Take a look at the drawings show- sheeted float with plastic film. Or you down more than 1/2" below the bottom ing float attachment for both two can leave the foam bare and cover of the end of the float. You want to wheel and trike gear aircraft. The nor- with low heat film. Or. you can cover make sure that at takeoff speed only mal landing gear will work just fine on the floats with clear or brown package the air rudder is used to steer. The floats, you just have to do a little tape. When I first suggested this type water rudder is so effective that if it is modification on the nose gear for a of covering about 7 or 8 years ago, lots in the water on a high speed run. any trike type, while adding an extra rear of guys laughed, but after trying it, movement will result in a violent brace for a tail dragger type. It's easier most came to realize that this type of change of direction of the aircraft. to replace the nose gear wire with an covering is quick, easy, cheap and du- We mentioned about adding "L" bend wire of similar diameter, rable. The final method is to leave the weights to the floats to arrive at rebal- then when you change from wheels to floats uncovered and go fly. Whatever ancing the aircraft at its balance point floats, a couple of wheel collars are all method that you use will work, just re- after the addition of floats. This is that need to be removed to make the member that the more finish you add very important and should not be changeover. On a tail dragger type to the floats the heavier they become overlooked. landing gear, a mounting plate will and that the overall wing loading will need to be added to the fuselage just increase. COPYRIGHT RCM MAGAZINE