Control Line Stunt Twin Rudder

Olympic Mk.VI

By Robert C. Gialdini, Milwaukee, Wisc.
Originally published in 'American Modeler Annual', 1963.

Heading picture

Milwaukee's Bob Glaldini Is what the editors call a "dedieated modeler" . . . he approaches this hobby sport just as he did Table Tennis and Sailing In both of which he excelled. R.G. attended Marquette University, currently works as a sales representative In the truck equipment and road machInery field. Has flown free flight, now concentrates on U/C. Has almost won National Stunt honors several times; meanwhile has racked up numerous wins in regional combat and stunt events. Other specialties: skiing and ice hockey. Has acquired very charming wife (Joyce) and 6-year old offspring (Genell). Below, various "mark" Olympics.

Olympics & trophies

Take our word for it: this is absolutely the most provocative and illuminating report ever to appear in print on the subject of C/Line Aerobatics. Even if you don't built or compete with stunt planes . . . even if you've never constructed a Ukie in your life and may never expect to . . . read what Uncle Bob has to say about the aerodynamics of tethered flight. This guy has made a serious study (although his report is light-hearted, easily absorbed) of his subject which shows that stunting is a lot more than flying the proverbial brick on the end of a string!

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One of the remarks made by John Clemens in his cornmentary during my exhibition stunt flight at one of the Nats' week-end public shows still sticks in my mind. He contends that this is now 'Precision Aerobatics" rather than just plain. "Stunt". John won Nats Stunt awards when it was and knows whereof he speaks.

The pattern which we have been flying the last few years requires considerable effort - not only an experienced pilot, but also an aircraft that will perform these maneuIvers in a manner which the rules specify for competition.

Thus, the reason for the existence of our series of "Olympic" contenders. The design is an approach to the problem, but is it the final answer? I don't think any one of us has seen the ultimate in a stunt airplane or will for quite some time.

Meanwhile, we progress through various stages of design. This brings up the age-old question of originality. When control line is spoken we have to look back to the late Jim Walker, then we can break it down into changes and additions. To Bob Palmer for the moving flap innovation and to George Aldrich for the slow pattern. To these and others we doff our derby, for each had an original approach to the stunt challenge. Everyone's interpretation of the ultimate thus differs.

Olympic was worked out to my type of reflex action which I find is the rule rather than the exception. I have watched some of our better stunt flyers who have lightning reflexes combined with outstanding co-ordination . . . but they are few and we are many.

During the development of the design, I was seeking certain characteristics which I felt should be incorporated in a competitive. airplane. Primarily, I wanted smoothness, coupled with good turning ability and necessary amount of stability through all maneuvers to give it that turning-on-rails appearance. Trimmed to fly level, she would he forgiving of nervous errors in command.

I began the original Olympic in 1957 from a Nobler which had that primary characteristic of slow flying which tolerated slower reflexes. Her size was easy to handle and as for airfoils I used the stock Nobler 17% wing. I retained the basic fuselage shape without any special reason, but later proved to be a stroke of luck. The main change was an additional 1" nose length, which dictated a Veco shaft extension. Tail moment was retained as in the kit, but in place of the single rudder, the fuselage rear deck was extended straight and twin fins utilized. While not contributing to the straight ahead flight as a fin generally does, they have a channeling effect on the stab-elev airflow eliminating tip vortex and its resultant drag, therefore increasing efficiency. Why did they tilt? It looked good!

The landing gear was kept short to lower ground angle of attack and improve take-off and landing characteristics. Added advantage is lowered barbell action during inside squares. Okay . . . let's thrash that around.

After much discussion witli Chicago's Ed Kazmirski and Minneapolis' Bob Hansing, both of R/C fame, I was enlightened by some of the remarks, for their problems coincide with ours.

Look at it in this manner. We have a barbell with concentrated weight at one end, representing engine and tank, and the empennage at the other, the center of the barbell being at the CG (sketch B). Pivot the barbell and see what happens. When we turn a corner, the weighted ends of the barbell must be accelerated, but when exiting the corner this moving mass has to be halted.

Sketches A, B & C The problem lies in the physical laws that first the mass resists change, then after it has been accelerated it refuses to stop due to the energy accumulated during its acceleration in the form of inertia. This is the gremlin that causes the slow entry and bouncy over-control you might have experienced at one time or another. To this we must bring into the picture the overall weight of the airplane. I have watched both heavy and light aircraft of the same design perform a stunt pattern and have been amazed to see a heavy plane fly very well, many times out-performing the lighter ones.

After kicking the problem around I wonder if we haven't placed the weight emphasis in the wrong place. I used a 34-oz Olympic in '58 that flew fairly well. Refinishing it in '59 brought the weight up to 51-oz. From that day, the airplane never did perform. But where was the weight concentrated or distributed? In order to retrim the ship I had to add 21/2-oz nose weight. Obviously, most of the 14.5-oz of finish was behind the CG. Thus, we added a few more bells to that bar and impaired its grooving characteristics, along with its turning ability. The results lead us to helieve that weight, if not excessive, concentrated as close to the CG as possible, shouldn't have a great deal of effect on turning and grooving. Our 18% wing is easily capable of lifting the load. Do we use all the control movement possible in a square corner? General feeling is that we don't, indicating more than ample lift.

A good rule to keep in mind is that when turning that tight corner, you have to multiply the weight of the airplane or any part thereof by the force acting upon it or the "G" loading exerted. Thus, if you add 1-oz of weight and you pull 20-G's that 1-oz suddenly weighs 20-oz. A very tangible weight that should be considered when adding up various odds and ends.

Up to this point we have been discussing location of mass that would affect the airplane on the pitch axis. Roll axis (sketch C) is affected much the same way. We must realize that the tips are light, but the moments are great . . . 27" each direction on a 54" wing. With such long moments, the moment of inertia is high, so concentrated weights must be kept small.

On the Olympic Mark V, I broke one of my own rules by locating the wheels in the wing rather than the fuselage, close to the CG. I tried to alleviate the effect of the wheels being outboard by sweeping the gear in toward the CG. Actually, the wheels and pants are in about the exact location as the previous Olympics so the only weight added outboard is the struts and the landing gear platform and these were kept to a bare minimum. By placing the wheels farther out we are, in effect, adding some bell to that bar again and in the corner, should you encounter a burble of rough air and roll does occur, it is noticeable because of the concentrated weight and the inertia stored up once it has moved.

This leads us to concentrated weight which affects our roll axis - that is, wing tip weight and control line weight. There has been much discussion regarding the merits of wing tip weight, but nothing ever has been pinned down as the answer, only theories. I have always believed in tip weight but at the barest minimum. Back to that problem of the amount of "G" force in the tight corners, since all weight is acted upon equally, that piece of lead has increased to a very tangible amount. One ounce with a 20-G force weighs 20-oz. Therefore, my rule is to add just enough tip weight to make the outboard tip fall slowly when the airplane is supported on the thrust line.

This, of course, will change with the addition of finish when the inboard wing is larger, but it is not necessary to have an exact amount of weight. Fairly close is good enough. By placing a small amount of tip weight outboard we have a tangible amount of mass which statically unbalances the airplane, but dynamically offsets the weight of the control lines in the tighter corner. They, too, have weight and represent mass combined with a considerable amount of drag. Thus, that 20-G acts upon the control line also, but diminishes as it moves away from the airplane toward the control handle.

I have proved this by flying one airplane trimmed for .015 lines, which are standard, then flying on .012 and on .018 lines. The effect was that both the .012 and .018 lines created a slight wobble in turns because the former were too light and the latter were too heavy. In the .018 test, the corners, when tightened up, became rather unnerving because the tip weight was insufficient to offset the lines causing roll-in and loss of line tension. In conjunction with this I have always tried to keep the lead-out wires and end connectors as light as possible.

A word with regard to the longer inboard panel. Most stunt designs have utilized the longer panel to help balance the air craft laterally because the inboard wing does not travel as far or as fast as the outboard. After mulling over this difference in speed, I dug into the old high school algebra book for some brushing up on equations. At 60-mph on 60' lines, a wing span of 48" gives a 4-mph difference in speed between inboard and outboard tips.

We have discussed the pitch and roll axis so this brings us to the third and last part of the dynamics, the yaw axis. In a U-control model we do not have to deal with the problem of sideslip as we do in a free flying aircraft, so lateral area is not critical in this respect. There are several ways of stabilizing U/C aircraft on yaw axis and the ones that do are definite and must be accepted as such. First: the amount of lead-out sweepback. Second: the amount of rudder area. Third: the amount of lateral area.

It must be realized that if sudden yaw does occur it will manifest itself normally in the wing tip at the leadouts' location for this is the point of tether. The resultant yaw, if severe enough, can put a whip in the lines, compounding the movement of the aircraft. Deep aft fuselages have become the rule since they weathercock on the upwind side, also tend to aerodynamically damp yawing oscillation. Most lateral area should be concentrated behind the CG for this reason.

I use twin rudders on my Olympic, but it has operated minus the rudders without any appreciable change in flight characteristics. Thus, its depth has helped to keep the fuselage aimed in the desired direction. Unless the rudder is of considerable size, general contention is that in the tight corner it does not contribute much toward stability and even less on the inside maneuvers due to the blanketing effect on the wing. An air-foiled surface like the rudder must be considered a working surface, yet due to the blanketing of the flaps, it can become quite ineffective. Mention has been made that with the boxy look it is difficult to discern where to attach the control lines - to your airplane or your tool box! We agree that it is difficult to offer clean lines around this amount of lateral area, but with so much at stake in flying characteristics, this large amount of area should he retained.

If you are flying a design with little area aft of the CG you can experiment with this additional area by adding a large dorsel fin of " sheet balsa wood and masked to the fuselage between the cockpit and rudder. It is interesting to note the results, especially if your aircraft has been fish tailing in the corners.

The other part of yaw stability which we must deal with is line sweepback from be bellcrank to wing tip. While bellcrank location is important to stability, the airplane is flown from the wing tip and the location of the lines at the tip determines the attitude the aircraft will fly on its yaw axis. The amount of sweep back is determined by length and diameter-and can become quite confusing. (Ed. Note: few variables - flying weight, operational speed, line length See CL Capers in Nov. 1962 American Modeler.) Since most aircraft are flown on 58.5' lines of .015" diameter we have part of the equation solved. I have utilized a 5 degree sweepback in all the Olympics.

I have listed three things which will effect yaw of the aircraft and now a fourth must be considered. Accepted without question as to its merit, while the other three are highly controversial, it is wing sweepback. Without going into a great deal of aerodynamics, here is the basic reasons for wing sweepback. With a wing of this type as air flows over the surfaces during flight it has a tendency to slide toward the tips. Should yaw occur, the leading edge of one half of the wing swings closer to 90 degrees to airflow. This that causes that side of the wing to become more efficient with relationship to lift and thus produces more drag, because lift and drag go hand-in-hand. This increase in drag tends to damp the oscillation and stability. returns. For full-fledged competition, the extra work involved in building a tapered wing is well worth it, but for Sunday afternoon fun flying a straight wing will suffice.

When the second Olympic did not prove its salt, I decided that the third would have one thing subtracted from it - frontal area. My reasoning lies in the realm of R/C, for it was just about the time that radio flyers were in deep discussion about an aircraft's ability to penetrate.

While we in control line do not have as critical condition as the R/C crowd, this point should be considered When we perform any maneuver, we change directions in regard to the prevailing breeze. Looking at the loop we find one side, the climbing half, is usually performed slightly upwind and the second part, the diving half, is running slightly downwind. If drag is in excess, the model will slow down on the first half, but will accelerate through the second half, thereby eliminating some of the smoothness we are seeking. An engine performing properly should help alleviate this, for additional power should be available when the load is increased. But the windier the day, the bigger this problem of speed variation. This is the reason for the extremely narrow fuselage. These things help to achieve a good integrated pattern.

Bushed horns Flap mods
Click on these two pictures for a larger image.

General arrangement

On the Mark VI Olympic I have used an 18% thick airfoil with max thickness at 30% of root chord. At the tips, 19% with maximum thickness at 25%. Looking at the shape of a non-symmetrical section of a light plane, when viewed from the trailing edges, both tips are washed out (bent up). This is done so that when the aircraft is at its rated stalling speed, the tips have not reached stall angle and stability with relation to the roll axis remains. To achieve this same effect with a syrnnietncal airfoil, the thickness percentage at the tips is greater than inboard with the maximum section closer to the leading edge. Therefore the tips stall last or at a higher angle of attack assuring some tip lift to resist engine torque. To prove this point, while flying one of my older Mark II Olympic I let the engine quit while the plane was quite high. During the landing approach I gave excessive up control to stall the airplane. I experienced a very severe roll, first toward me and then away. With the improved airfoil, my Mark V can be stalled with the only effect being an extremely mushy approach . . . no rolling. This indicates the tips are effective while the center section is stalled. Try it yourself. A great deal can be learned from a gliding stunt job, so observe its characteristics closely when you are making your landing approach.

Speaking of airfoils, let's not forget the stabilizer and elevator. They are working surfaces, too, and in order to achieve their purpose, must be of sufficient thickness.

On the plans I have offered axi alternate type of landing gear. The first design series used the fuselage gear incorporating a torsion principle which does a fine job of absorbing landing shocks. Its drawback was that when the gear was loaded as in a bump, it returned with authority driving the plane back into the air. This occurs on hard surfaces, not on a grass field. If the majority of your flying is off the grass, the torsion gear is then best for you.

On the Mark VI I switched to the swept-in wing mounted gear in my search for better landing ability on hard surfaces. When flexing to absorb the shock of landing, the gear has to be in a position which will not transfer the shock into the plane. If you trace this shock line, you will find that the straight-ahead gear has to spring forward to absorb this shock and has to flex farther for a given amount of load. With the swept-in gear, the motion of the gear is 90 degrees to the shock line and its movement is not as great for the same amount of load. The secret is that the shock line is not straight up but somewhere around 45 degrees. Most straight-ahead gears are at an angle of 45 degrees and in direct alignment with the bump load.

A slightly stiffer gear has to be used in the wing for good ground stability. It also tolerates a much faster landing speed. A proto landing on two wheels should be the resut of a good approach and this means that once you are committed, you should not whip it around another lap to aIign yourself with the wind. When the motor quits, set up a last, deliberate approach immediately and with ample flying speed you can set your model down on the downwind side and just hold neutral control until the plane loses momentum. Also, with the lift of the wing remaining effective at the faster landing speed, it's not as likely to bounce.

Good judges look for a one-approach landing and when a pull-up is detected to take advantage of the wind, most. subtract landing points. Don't forget, dead stick landing of a real aircraft is completed with just one approach and this is what we are trying to duplicate.

With regard to tanks and other hardware, I would like to point out just a few gimmicks that quickly prove their worth.

I have utilized both the single-vent pressure tank (not crankcase pressure but velocity ram) and the two-vent. pressure tank with success. More important is tank location and above all cleanliness. Dirt can be a real problem, so keep your tank vents plugged during building and while the airplane is in storage. The best quarter investment one can make is a line filter between engine and tank because regardless of how clean you keep your fuel dirt can be picked up while flying . . . especially if you operate off a grass field. Nothing can be more disgusting than to get halfway through a stunt pattern and experience engine failure and especially so during a contest.

Another item that can be a big help to performance is wheels. Most rubber wheels we utilize have turned aluminum hubs and the bearing surface for the wheels is a mating of aluminum with piano wire or steel. Unless well lubricated, the aluminum will eventually gall and the bearing fit becomes very sloppy - but even more, it causes a great deal of excessive drag. By bushing the aluminum with brass tubing or some other material, the wheel will perform its task more efficiently. A fast proto landing creates quite high wheel velocities and, therefore, a good bearing is important.

Before getting into the construction, I would like to review the various Olympics I have built and the results.

The original Olympic-Nobler mod job (detailed earlier) never quite felt under control due to opening corners in high wind although it flew well enough to place 4th at the Nats in '58. Upon retirement, the ship showed excessive strain cracking at wing and cockpit, indicating areas for beef-up. Engine vibration is inherent so must be carried out in shear as widely distributed as possible. Engine bearers on subsequent Olympics are tied directly to wing leading edge and polyester resin is used to fix. Doublers in other areas proved effective in eliminating strain cracks.

Olympic Mark I, same shape, but 1/2" longer nose and tail moment arm, Fox 35 power and leadouts over and under. More paint to 48-oz weight. Frankly, this ship was a dud. It flew. with the grace of a drunken elephant and turned with all the snap of a soft marshmallow just off the toasting stick. This bloop took a good deal of valuable time in measurement and flight (maybe fright) analysis. Couldn't even make thrust line adjustment take and later tries at this fix did little good.

Flying a proved Mark IV a year and a half later we changed thrust line angles as much as 5 degrees with little effect on flying characteristics. Could be that long nose moment or something, since others feel it quite important. So - Mark II, III and IV were similar with slight changes in construction; engine, and weight reductions (42, 44-oz) by Silkspan covering. The D tube wing resisted any originality recognition since the Nobler wing is a D, too. Performance of man and machine at the '60 Nate have been chronicled, where the Mark IV performed superbly, but the man couldn't. Besides, no one lets me forget. Maybe this was what prompted the big switch in wing construction for Mark V.

In eliminating the D tube I went with a 1/16" full depth web capped by 1/8" square, doubling the number of ribs and capping all with 1/16 x 1/8. It was strong and it was light, but it didn't work. Flexure at the root kept popping silk and I wasn't satisfied with its squaring due to an inherent softness caused by dihedral during high load turns.

This ship which caused "Wild Bill" to wax enthusiastic netted me a third at the '61 Nats. Mark V used Fox 35 power and continued to prove out the 3/8 square long engine mounts. We used teflon bushings in the control system and felt that the Olympic was approaching our goal of the ultimate model.

However, rewarding chats with Ed Kazmirski shifted our thinking toward fully planked wings, since proper wood didn't weigh any more than fabric covering. So Mark VI went into production. Airfoil shape was retained,area increase to 600 sq. in. and 1" added to nose and tail.

This beauty turned into a beast . . . hunting in level flight! Since we didn't solve it before the '62 Nate we flew the old one, losing a prop and a wheel pant, our composure and generally placing fifth before the best judges we've seen.

Came a period like unto Mark I only this time we whipped it, coming up with a very radical, but sound solution to stunt ship hunting. Many conversations turned up an oft-stated fact "Old stunt ships don't hunt, while the new ones do." We won't hold you in suspense: when I reamed out the elevator horn hole for the pushrod the hunting QUIT. With leadouts locked, flaps solidly centered, the elevator trailing edge moves about 3/16" up and 3/16" down. This forces some up control to maintain neutral elevator in flight which droops the flap slightly. Evidently, the slight aft center of pressure shift on the wing plus the stabilizing effect knocks the hunting phenomenon right on its little pointy head. Backup data includes Jim Silhavy's Nobler experience and fact that after Bill Werwage rebuilt the controls in his 5-year-old "Ares" she started to hunt. "Wild Bill" concurred via his AM test Stuka which settled down with elevator slop. OK, gang, we fell into it, but it's logical, so try it.

The Mark VI? She's presented here in plan form so build her.

Plan 1
Plan 2

Through the years of contest flying some facts of practice and procedure have been gleaned and learned the hard way. Since a good model is not enough let's quietly examine procedures that work well. Mixing sport and contest flying is difficult, if you expect to maintain a Nats-like trim. So make your choice and stay with it.

My pre-contest pattern includes several days of concentrated flying to bring myself up to a peak. for those two big flights. The amount varies with individuals from 50 flights, to one flight just before you make an official. If possible, have someone watch your flights and elicit honest reporting since you can't see your own pattern as a judge does. Fly smoothly through the entire pattern including level laps since it is an integrated whole, not a series of disconnected squiggles. Practice individual maneuvers ONLY when rusty. Go-for-broke officially, but have the good sense to fly conservatively in practice.

A good night's rest before a meet is important, for good stunt flying demands a great deal of your reflexes and co-ordination abilities. -

On contest day I always have tried to put in one practice flight in the morning to check out needle valve setting and wind conditions. Check with the weather folk for possible change in conditions. If at a strange field, ask some of the local talent for their normal wind conditions and note the location of the flying circle with relationship to ohatructions that might cause extreme turbulence. These things can make or break a good flight.

After a practice flight, keep an eye on happenings and procedures as competition begins. Try to pace yourself with regard to competitions for timing can be extremely important. When you feel mentally ready, turn your name into the officials and check immediately' the nuniber of flights ahead of you.

If I am flying other events such as combat and ratracmg (which I do at most of the meets with the exception of the Nationals), I do not put my name in for combat until my first stunt flight is complete and my score posted. Stunt remains my favorite event and the others are fillers for the day. This might cost you a chance to compete in the other events, but that is a chance you have to take. Few people can fly a red-hot combat job such as the Equalizer which we fly for competition around here, then pick up and handle a stunt flight accurately. Reflexes are not built that way. I refuse to fly anything but my own stunt model for three days before I put in my first official flight for this reason.

After I have submitted my name, I wait until the previous flight has reached the three-quarter mark, then I begin loosening up my motor for if your engine does not prop freely it is not going to start immediately. Prime through the stack until it runs the entire prime out and you know that the front bearing is completely free of cold castor-oil.

After appearance judging and you have been notified to proceed, don't waste time, but rushing can be disastrous. Lines and connections are important, so treat them accordingly.

I would prefer to maintain one needle valve setting al all times so that an improper setting would be unlikely, even during starting. However, with the change from the Forster, which could be handled in that manner, I have found the Fox will not pull the fuel on a prime only; therefore, I open the needle valve a full turn. This is important and a mark should be filed on you'r needle valve; once a setting has been established during practice, do not deviate from that setting. If it changes for any reason, stop right there and find the cause. Many contests and airplanes have been lost due to the pilot not believing his needle valve setting and, therefore, playing it by ear. If up for an official flight take an attempt and then retire to your pit or practice circle to locate the cause. Too many fellows forget that 3 attempts are allowed and rush to re-tighten a loose prop that should have been tightened beforehand, anyway, and lose their starting points. They take a chance: on running over the allotted eight minutes flight time.

While the rules do not list what many flyers term "impression points," nevertheless, they are always present. These points are the ones accumulated through your conduct around the stunt circle and after your flight. One of the subjects that Mr. Wooley and I have debated is the method employed in starting an engine. I have yet to find it necessary to turn my airplane upside down so the engine is in an upright position to start it. I feel this is one of those things that affects your impression points unfavorably. After all, if you keep a Piper at the local airport and find it necessary to prop it by hand, you don't turn it upside down, now do you, Mr. W.? Coining a phrase from Caper Cooker Netzeband: "Boy, am I ever going to get stomped by the upside-downers!"

Be prepared for a contest both mentally and equipment wise and know your engine. This applies to any event you fly. Above all, accept the good with the bad and help good sportsmanship prevail. I have been fortunate in meeting many, many stunt fliers and, as in many other hobbies we all have something in common. They are all gentlemen. Begin flying competition and find out for yourself.

I have not listed all the trophies which have been won by Olympics. This, of course, is the primary purpose for building the airplane, but I find that the impression you leave behind, the friends you make and the reception you receive the following year at the same meet, are even more important. Nothing is more gratifying than the respect of your fellow competitor.

Construction. Everyone has his pet method of beginning construction after the wood has been selected. Remember that the one outlined is just one person's approach and not necessarily the proper method for everybody. I dislike certain building tasks and leave them to the very last if I can.

After the decision has been made as to the type of wing you will make - sheeted or fabric covered - and you have selected the wood accordingly, lay out the basic wing structure and pin together.

Our hobby shop stocks a complete line of Sig balsa wood from contest grade to R/C in all lengths. Five of my Olympics have been built from Sig wood and finished with Aero-Gloss dope. Proper wood selection helps make the building job a great deal easier.

I have shown what I term an anti-warp spar. Actually, this spar keeps the wing from picking up dihedral during assembly. After the ribs have been slipped into the slots in the spar the ribs are notched for the 1/8" ilquare spar on the top half of the rib - the unslotted half. If the square spar is glued to the full depth spar first and allowed to dry, then when the ribs are glued to the spar the action of the glue contracting will not pull the wing into a gull

If you are using the sheeted wing, the one most important task is covering. Yours truly ruined two fraineworks before the following method was employed. Sheeting must begin at the spar. After gluihg a piece of 3/32 x 3" stock to the sper and it has dried, wet with water and pull down to the leading edge. If you try sheeting the forward portion of the wing by beginning at the leading edge, it is impossible to achieve perfect rib contact at the sharp curve and, therfore, the proper airfoil shape is not maintained. After the forward portion is covered, work in the other direction with your sheets paralleling the leading edge. This will necessitate joining the sheeting at the center of the wing, but a narrow cap will strengthen the center section after the sheeting is complete.

After sheeting has been completed on top and bottom, rough-cut the tip blocks and tack-glue them to the tip ribs. The inboard tip has to be drilled to accept the leadout wires for the control system is in by now . . . if it isn't suggest you think seriously of converting this wing for free flight or R/C!

If the fabric-covered wing is decided upon, sheet the leading edge with 3/32" as In previous step, but then 1/4 x 3/32" cap strips are used. The center 4 ribs are sheeted top and bottom with. 3/32" as a standard D tube wing. Should you prefer built-up tips, you're on your own.

Also, if using the wing gear, leave the piano wire extra long and do not make the last bend. That is where the wheel rides and it will be bent later. Two cork bottle stoppers jammed onto the end of the gear wire will protect your work surface . . . likewise for the wing leadouts unless you use them for stabbing spiders, etc.

Just about this time, control horns will be necessary, for flap time has arrived and the horn must be mounted.

We did it the hard way, with split tubing, but you can buy Veco. flap horns with spring bearings. Simply center the horn on trailing edge radius and wrap linen or nylon tape over spring and double cement. Elevator horn should have similar bearings.

After the flaps have been mounted and the tips removed and hollowed, the wing should be complete. All those, nicks, scratches and gouges that have been acquired during handling should be left to a later time. If you fill them now you will only have to do the job again, or else move the basement ceiling up another two feet.

The enjoyable task of constructing a box on which to mount this wing has arrived. If possible select for it 1/8 x 3 x 48" wood. This will eliminate the problem of splicing a piece at the tail. These two fuselage sides must be straight because their top edges will be the origin for all measurements to make or mar the entire airplane.

Fuselage construction

Due to the fact that engine bearers are 3/8" square, preglue all front members for maximum strength.

After the wing slot has been located by measuring down first to the center of the leading edge, then the trailing edge, think seriously about the fuel tank you plan using because this is the time for its installation. By leaving its vents long, the tank can be installed after the fuselage halves have been joined - that is, if you are using a home-made petrol carrier.

Double glue all bulkheads to fuselage sides and, after thoroughly dry, the wing can be mounted.

My method. is to locate the wing in the fuselage first by measurement, then sighting to see if it looks good, make a correction here or there to insure good fit, then tack glue in place. I use fiberglass cloth strips and polyester resin inside the fuselage to do the final cementing job. This assures a good bond and since you have no standard glues under it, it bonds well.

Since the stabilizer must be readied about this time, finish the entire assembly with the elevator horn modified as mentioned. As you mount the stabilize.measure the top of the fuselage for alignment . . . if you add negative or positive incidence, you are on your way to just another humdrum stunt job.

After the stabilizer is dry, using a long sanding block, shape the top part of the rear fuselage formers. As noted on the plan, they are installed oversize and the final contour is obtained after they are installed. This assures smooth curves for the planking. Plank top deck per pIan. Tack glue top front block on body sides. Cockpit detail should be added and the canopy installed.

One quick note about molding a canopy. I consider myself the world's worst canopy molder. I mold 20 to get one. Ask anyone else for methods of molding, but not me. All I can suggest is .040 acetate for material at an oven temperature of 350 degrees. This works just fine for absolutely everyone . . . except yours truly.

After cockpit is complete, mask off and cover completely so paint and dope do not get to it.

Work on the business end must commence, uness we have decided on hand launch, tow line or rubber power. (You can see how Netzeband's influence is rubbing off on us younger control line fans!)

Mount your engine on the bearers and watch that thrust line. Your cowl blocks should have been assembled by this time and you can now hollow to just clear thogine. Tack glue the cowl in place and tack glue the bottom fuselage block in position. Shape exterior of bottom block, remove and hollow. Cooling exhaust vent must be cut in forward portion of this block and if a screen is used, install it now. Re-glue the bottom block on permanently and shape the cowl. Sculpturing of the cowl is a mattter preference, use the style you dig the most (oops, connotations of a crash there?).

Before the cockpit was installed, the top fuselage block was tack glued, now shape, remove and hollow it. replace it and use lots of glue around the engine mounts

The spinner should be in place and the 1/16" plywood back-up ring installed so you have something to sand to.

Install a 10 x 6 prop on your engine and we'll get that gear bent to tlie proper length.

Decide on the prop clearance you prefer. place two tables of identical height on a flat floor, leaving a gap between them. Let the gear hang in the gap with the gear on one table and the prop (vertical) on the other. Block up the prop tip with the clearance desired and mark the gear wire at the table top. From that mark subtract half the diameter of the wheels and that's where the bend is made (There must be an easier way than this!).

Install the wheel pants via any method you prefer. With addition of the rudders, shaped but not installed, final sanding can be started.

I buy Plastic Balsa by the carton and use it generously. Wing fillets are made with this material in 4 or 5 layers, ! with free use of thinner on your finger while shaping to prevent pulling the Plastic Balsa. After a final sanding of the fillets with sand paper wrapped around a dowel, add 5 coats of glue to the fillet.

Except where otherwise noted, I use Aero Gloss products,.from glue to thinner. This way I have no worry about noncompatible materials. C-77 glue has good penetrating qualities and soaks into the wood, so pre-glue all joints

Use any combination of filler and clear dope you prefer for the finish. I avoid white hecause Aero Gloss' White is a perfectly chalk flat color and to achieve a high luster takes a great deal of finish time and rubbing. The maddening part is that a judge hardly ever takes this into vonsideration when giving finish points. An average ref finish will pull as many points - or more - than white. Should you use white, add a good slug of blue to it to prevent yellowing.

After trim has been added, if you have access to a spray gun, lay a coat of clear dope over the entire airplane. Do this after you have heated the opened paint can on a hot plate to about 120 to 130". Be careful! This wilt help the Aero Gloss flow better. Rub with auto rubbing cornpound and wax accordingly.

Undoubtedly, you as I, have experienced the problern of handling a stunt job while working on it. This problem was solved when, on our way to Philadelphia for the 1961 Nationals, we stopped to see Jim Silhavy and Abe Cipra. "Old Walrus" Cipra showed me a couple pieces of 30" long, 1" x 2" wood, half wrapped with soft rags. When these are C-clamped to a table about 20" apart the covered ends hold a stunt job in any one of a dozen handy positions.

Dad-gum! Forgot the control system and . . . oh, yes . . . she weighs in at 59-oz. Guess that tonnage will just about kill me in Nordic.

Bob with Olympic V
Designer Gialdini fires up his Fox .35-equipped Olympic Mark V design
at the 1962 Nationals in Glenview, Ill. Bob had his usual run of Nats luck . . . lou-say.

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