Let’s face it, we all can benefit from listening to experienced modelers, and often we get emails and letters asking for advice on subjects such as flying, building and adjusting engines. So MAN asked some of our regular contributors for their professional RC tips and hints to solve basic issues that come up while we try to enjoy the hobby. Enjoy!
Q: WHAT’S THE BEST WAY TO RANGE-CHECK A 2.4GHZ RADIO?
Mike Greenshields, Global Hobby Distributors
To start, you have to understand that antenna placement on 2.4GHz equipment is simply more critical. A sure-fire range test for 2.4GHz involves a little more work and two people. First complete the standard range test. Make sure the plane is one foot off the ground, as tests where the antennas are less than one foot off the ground will cause difficulty. If the test works, then have your helper rotate the plane 360 degrees (like it was in a flat spin). Do not let him get between you and the plane. Make sure that at all angles the range test is still successful. Next, run the same test with the nose straight up and “roll” the plane (like it is completing a vertical climbing roll). Again, the range test should work at all angles. If the range test does not work for some angles, it means the receiver and/or receiver antennas must be moved away from whatever is obstructing the radio signal. Once the radio range is tested from all angles, run a standard range test with the engine running (obviously much care must be taken to ensure safety). The plane should still pass the standard range test. You only have to do this once per new receiver install. This is free and easy insurance!
Q: DOES A 2-STROKE OR 4-STROKE ENGINE OFFER MORE TORQUE?
Dave Gierke, engine expert & book author
Torque is an interesting performance measurement. In an internal combustion engine, torque is simply a twisting force as measured at the crankshaft. Since torque is measured as a force (combustion pressure multiplied by cylinder-bore area) multiplied by the crankshaft throw (its radius), it really doesn’t matter which type of engine we are dealing with: 2-stroke, or 4-stroke. The real difference is the brake mean effective pressure (bmep) that the cylinder can deliver during its operating cycle. Both engine types can benefit from the many types of forced induction, such as supercharging or turbocharging to boost their bmep. The 2-stroke’s tuned pipe takes advantage of the so-called supercharging from the exhaust side. The amount of power-boosting nitromethane an engine can use (chemical supercharging) is another factor because of the oxygen released during the combustion process (allowing a richer air/fuel ratio). Another consideration is the engine’s compression ratio; the harder you squeeze the mixture, the greater the thermal energy release from the fuel-within the boundaries of combustion defects such as detonation and pre-ignition, of course.
So, the question of which engine type will produce the most torque is complicated and ultimately boils down to who is the best tuner. I, too, have seen 2-stroke engines turn more rpm than comparably sized 4-stroke designs turning the same propeller. Just remember that power is the product of torque and rpm.
Q: HOW DO YOU WIRE PARALLEL BATTERY PACKS FOR MULTI-MOTOR SYSTEMS?
Greg Gimlick, electrics expert
If you’ve decided to use two packs wired in parallel to achieve the capacity required for your multiple motor setup, you’ll need to physically wire them together. Most suppliers of electric flight gear offer various “parallel cords” already made up, and you only need to specify your connector choice. It’s also easy to make them yourself. The key is to be sure that the positive lead of each pack connects with the positive lead of the other pack and likewise with the negative leads. It is essentially a Y-harness, where the two packs plug into one end, and the other end’s connector plugs into the ESC. If you use this setup, make sure to color-code all connectors. All the positive (red) leads go together, and all the negative (black) ones go together. If you see a red connected to a black anywhere, stop and remove it. Red and black connections plugged together means you’ve begun to connect them in series.
Q: HOW IMPORTANT IS LEARNING TO USE RUDDER?
David Scott, flight instructor, 1st U.S. R/C Flight School
Actually, pilots should begin their flying careers by using rudder from the very beginning. One of the ways we used to help beginner pilots is by programming in an aileron/rudder mix from the very start. This improves the plane’s performance by eliminating adverse yaw, which is the opposite yaw or skid inherent with aileron deflections on flat-bottom-wing planes, the very ones many new pilots start with. What is important is that adverse yaw grows worse at slower speeds and/or with larger inputs. This is why some pilots, who seem to fly around OK, struggle with controlling their planes during landing.
By coordinating rudder deflection with the aileron (rudder moving in the same direction), you prevent the nose from skidding to the left. Adverse yaw is thus prevented; banks and corrections, even rolls, will be smooth and axial, and you will feel more connected to the plane.
When a loop-or any maneuver related to one-is performed in a crosswind, the airplane will drift sideways with the wind during the slower portion of the loop. This drift will generally happen as the plane rounds over the top of the loop. Consequently, a loop that was entered on a parallel flight path with the runway will exit downwind-no longer tracking parallel. If you don’t use the rudder, you will have to do a number of corrections afterwards to reestablish the preferred parallel track taken at the start of the loop.
To correct cross-wing drift, apply rudder in the opposite direction the wind is blowing. For example, if the crosswind will blow the plane to the left, a right-rudder wind correction would prevent it. Ailerons are for keeping the wings level before and during a loop. Don’t try to correct wind drift by creating a new [wing] deviation using aileron; sideways wind drift is a function of yaw, not roll.
Q: HOW DO YOU MAKE LIGHTWEIGHT TAIL FAIRING BLOCKS?
Pat Tritle, expert model designer, builder
It’s easy when you use a simple sanding jig to ensure the blocks fit perfectly when your built-up tail surfaces are installed. And as an added bonus, when the blocks fit perfectly, they can also be used in aiding with the tail section alignment. For my stick-and-tissue designs, I often use foam for the fairing blocks to make forming them easy and keeping the weight in the tail to a minimum.
Begin by making up the jig to fit the outline of the fairing blocks. The wood used to build the jig should be the same thickness as the tail surfaces. Essentially, the jig fills in the space taken up by the vertical and horizontal stabilizers, but it is cut to the profile of the blocks to make sanding them to shape easy and accurate. With the jig cut to shape and glued together, trace the outline onto the blocks using the jig as a guide. Then place the jig on the fuselage frame, and tack-glue it in place. And, last, cut the balsa or foam blocks to rough shape, and tack-glue them in place on the jig.
Carve and sand the blocks to final shape directly on the fuselage frame. By carving the blocks in place, it ensures that they will fit perfectly when the jig is replaced by the tailplanes. When done, carefully remove the jig assembly from the fuselage and the blocks from the jig.
Q: HOW DO YOU MAKE WING-TO-FUSELAGE FILLETS?
Nick Ziroli, expert scale designer & builder
Instead of adding the fillet after the wing and fuselage are built, I make the shape of the fillet areas as part of the fuselage formers themselves. This requires having at least the wing center section built and attached to the fuselage, but to make sure the wing is properly aligned with the fuselage, I build the entire wing and measure from the wingtips to the tail.
The fillets start with a 1/32-inch plywood saddle that forms the top-view outline of the fillets. This is placed between the formers and the wing, and then it is glued to the formers, making a perfect fit. Then I epoxy some carbon fiber roving just inside the outer edges and laminate it between the plywood and the first strip of balsa planking. This produces a very strong and ding-resistant outline that can be sanded to a very fine edge. Once the epoxy cures, I start planking the fairing section with 1/2-inch-wide strips of 1/32-inch-thick balsa, alternating the strips as I go-one along the wing and then along the fuselage. Fit each strip into place to make the seams and joints tight. Use a rounded sanding block to smooth the planking, and then fill any gaps or seams with a hobby filler. Once they are sanded smooth, cover the fillet area with fiberglass cloth and resin while you are finishing the fuselage.
Q: WHAT’S THE EASIEST WAY TO START A GAS ENGINE?
Aaron Ham, model reviewer
If your engine has an electronic ignition system, make sure that it is installed properly and that the ignition battery is fully charged. If you have a magneto-equipped engine, always install a kill switch to stop the engine.
For the very first engine run, close both the high- and low-end needles fully, and then open the high-end needle 1 1/8 turns and open the low-end (idle) needle 1 1/4 turns. These settings are a good starting point for a reliable idle and a rich high end. Check the manual for the recommended oil to-gas mix ratio, and fill the tank with fresh, filtered fuel.
Be sure that the ignition, or kill switch, is turned off. Set the throttle full open, and close the choke. Flip the prop several times until the fuel starts to flow through the fuel line and into the carb. Flip the prop again several times until the engine “coughs.” Open the choke, set the throttle to just above idle and flip the prop again to start the engine. If it doesn’t fire, begin again from the start. Let the engine warm up a few minutes before you advance the throttle.