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HELP
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THE HELP TOPICS
The help topics consist of links and Help Topics
accumulated over the years.
Many of them were from RCM Model magazine that is now defunct.
Please review these help topics.
If we have a topic or LINK listed and you are the author and do not want this
published in this E-book,
Just notify us and it will be promptly removed.
gwhite4432@aol.com
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TOPIC LISTINGS :
Decals
Don't sell the manufacturers of Decals for Plastic models short.
They have a lot of products that are suitable for Gliders, Peanut Scale etc. that are applicable on models other than those for static display.
Many youngsters start with resin type kits and it eventually evolves into other types of modeling. -
If you make your own Decals be sure and to fuel proof them. Making you decals from Monocoat is easy to do and eliminated a lot of problems concerning them peeling off or being ruined by fuel.
Save Deflectors
If you use an exhaust deflector to protect your plane from oil residue, many times you end up losing the deflector no matter how you attach it, whether it's with ties or twisted wire. A very simple method to save your deflector in flight is to simply tie a thin copper wire to one of the tie wraps and then over to the pressure tap. Very simple, but it has saved me 5 deflectors already!
Waylon Ford
Film Covering Degreaser Have you ever wanted to add more film covering (Monokote, Ultracote) to a plane you've already flown? It's difficult to get all the oil exhaust off the plane so the film will stick. Try using Cyanoacrylate (CA or superglue) kicker (catalyst). Just spray it on and wipe it off. I've been told it's a very good degreaser. (Courtesy Vince R.)
- How Much is Enough? -by Clay Ramskill
Like most things in the aerodynamic world, the answer to the above question is- "it depends". It depends on what you want from your plane; how manuverable or how stable you wish it to be in the rolling axis, whether or not you desire the plane to roll when you deflect the rudder, whether or not you wish the plane to tend to self right when its upset from wings level.
In general, the more dihedral an aircraft has, the more it will tend to self-right to wings level when upset from straight and level flight. This little bit of roll stability makes the plane easier to fly because the pilot doesn't have to be constantly fighting to maintain wings level. Note the top two drawings in the figure - once we are no longer level, the lower wing is effectively a bit longer, and the lift forces forces on the lower wing are pointed more straight up. Also, since the figure shows a high wing plane, the CG of the plane is offset toward the high wing. All these situations tend to force the plane back to a wings level condition initially, before the plane begins turning or skidding sideways.
But the conditions described above won't last long. Also note that we now have the lift forces on the higher wing pushing sideways; this will cause the plane to skid sideways, turn, or both. Assuming no corrections from the pilot, what now happens is largely dependent upon the size of the rudder/fin combination! If the fin/rudder area is just right, the skid continues just enough for the dihedral effect of the wing to return us to wings level. Too much area in the fin/rudder, and we turn without skidding. Centripetal force from the turn negates all the self-righting effects, and we fly in balanced flight, but in an ever increasing wing and nose-down spiral - this is called spiral instability. Too little fin/rudder area, and the skid continues even as we pass wings level, resulting in over correction, and the plane rolls and skids, oscillating like a drunken sailor - this is called dutch roll.
Although the above discussion is more important to glider and free-flight pilots, it brings us to look at how dihedral affects a plane in skidding flight - and the good and bad sides of the dihedral effect. Note in the figure what happens to a plane with dihedral when in a skid, or unbalanced flight. This condition can occur with the pilots deflection of the rudder, or when a wind gust hits the plane from the side. The large discrepancy in angle of attack between the two wings causes the plane to roll away from the direction of the skid.
The dihedral effect is beneficial in self righting, gives us roll coupling with rudder application, and unfortunately, also gives us roll away from a side wind gust. Incidentally, sweeping a wing back also gives us dihedral effect - with about 5 degrees of sweep being equivalent to 1 degree of dihedral.
While roll coupling is essential to a trainer with no ailerons, its not good for aerobatic and combat aircraft. Most acrobatic and pattern models will have no dihedral. Military planes, with swept wings for speed, often use negative dihedral to counter the dihedral effects from the wing sweep - the Harrier, A7 Corsair, and C5 transport come to mind.
And while trainers usually have quite a bit of dihedral, and are wonderfully stable in normal flight, we've all seen them turn vicious in a gusty crosswind, during take off and landing, and even while taxiing on the field.
How much dihedral is enough?? For most of us, then, the answer is - Only enough to give us the roll stability
we need, commensurate with our flying skills! -
Drilling for Dowel Pins When drilling holes in the plywood of your plane to accommodate wing hold down dowel pins, it is sometimes difficult to get them just the right size without some
slop in the hole. For example, if you were using 1/4 inch dowel pins you would need to use the next size larger drill bit which is normally 17/64. Not bad but a bet er way is to drill the 1/4 inch hole, harden the hole with CA and then enlarge it with a 1/4 inch prop reamer available from Tower Hobbies. This makes the hole just the right size and a snug fit ing dowel pin. This prop reamer works with other sizes also.
Gene Davis
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If we all had wind tunnels.. and know how to use them this would be simple. The More lift that is generated equals more drag.
Simply because the shape of the airfoil shape for the greatest lift induces drag.
The more lift we need, the higher the angle of attack our wing must operate at, the more lift drag we have. And once our wing area, shape, and airfoil are established, there's really only one control we have, and that is the weight of the plane.
The heavier the aircraft, the more this form of drag will degrade performance, throughout the speed range!
Other forms of drag are :
The more air you have to push aside as you go through it, the more drag.
So we need to keep fuselages reasonably slender, airfoils reasonably thin. But the size is not nearly as important as shape.
Form drag :
S
Every component of the plane should have smooth shapes ( like a good symetrical airfoil --for instance ) . What is desirable is a nice smooth curvature.
will tend to increase turbulence and produce more drag.
A rounded fuselage is less draggy than square , and the same goes for wingtips.
Interference drag
Easily the worst contributor to drag is the landing gear. Fixed gear drag can be reduced by wheel pants
and cuffs on struts -- but a retracting gear is the obvious solution. There are, however, weight, complexity a
nd expense penalties.
The interference caused by projecting objects (like wings, landing gear, gear struts, stabs, etc.) can be reduced, usually by the use of fillets. These were quite pronounced on WWII fighter wings, as on the Spitfire and P-40, and just rounded off the interior square corners, carrying the rounding well aft of the wing. You'll see these on pattern and racing planes.
Retract the landing gear, hide the control horns, enclose the radio antenna, countersink the bolt heads, etc. Cowl in the engine, use an enclosed muffler. Look at a competitive pattern plane -- you'll see all of these features.
Skin friction :
Rounding corners not only cuts form drag, it cuts the skin area. Round forms enclose the most interior volume with the least skin area. A smooth skin cuts drag -- dirt, rough covering overlaps, and covering wrinkles all increase drag. You won't do much better than good sanding and Monocote!
Like most things aerodynamic, drag reduction involves many details, all of which add up in achieving your goal. "If you want to go fast, get out the sandpaper" and remember, we need both a smooth skin AND a smooth form!
DRILLS Small drills from #50 (about 1.75-1.8 mm in diametttttter) down to #80 (.33mm diametttttter) as well as mettttttric drill increments of 1/10 mm are very handy for a number of uses on exterior areas of aircraft - putting in locating holes for pylons, ettttttc. Small mettttttric and Imperial drills can be obtained from engineering supplies. - Dual Rates - The Good, Bad, and U
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Dust collector Next time your wife yells about the balsa dust from sanding steal one of her large fluffy bath towels and use it to sand on. It not only protects the airplane from dings, but it will trap a huge amount of dust.