|
|
|
The Plan Page
[ Home ] [ Previous Plan Pages ]
[ Special Things ] [ Earl Stahl Plans ]
gt-hunter1@home.com
|
|
|
A High
Performance Soaring Plane That A
Beginner May Construct Easily and Quickly
|
|
A GOOD guess would be that about ninety per cent of all models made in America are powered and another good guess would be that ninety per cent of models made in Europe are gliders. One possible reason may be that, in America, model building is first a hobby or sport and a powered model is preferred by the experimental groups because of its greater appeal to creative ability, due to its more numerous problems. However, Europe model building is a bit more serious, ultimate aim being to make an efficient air force. Model gliders are a short step to real gliding and soaring which is another short step to real plane flying.
The results of the Jugoslavian King Peters International Model Glider Competition in England was very interesting. Offhand, Germany, having the greatest experience in this branch of model work, had the best chance of winning a leg on the trophy but the English, centering around Mr. Bullock, were considered very dangerous. The way they cleaned up the first King Peter's meet was shocking: the other contestants, including the author, did not even get "crumbs to lick." Excuse ,me, we did get something. We were promised, or bribed if you will, by the English team if they won they would pay for all the cakes and ice cream we could eat. Naturally when we came to collect the reward, we put much painstaking research into the serious business of finding out the most expensive place in town and then ate until they got to worrying. But the laugh was on me, for that night the banquet was held and we just did not have the courage to order second helpings except, of course, the champagne and dessert. Next time our timing will be better. The King Trophy is given to the nation whose team will be able to win it three times. Unlike the Wakefield Competition, it cannot be won by an individual. An interesting sidelight or feature is that one year the contest is held for rubber-powered models and the next for glider models.
"Eva" was originally designed as a hill soarer but has proven to be a fair all-around performer. It has, or its loaned design, won every contest entered into. Its best flight has been eighteen minutes. We have tried different wing combinations but the present one seems most practical. Increasing the span will better the glide but there is danger of wing flutter and spins on the catapult launch.
One side purpose of this article is to introduce the European method of launching gliders, called the "hochstart." This was originated by Horst Winkler, Germany, and their contest rules for purpose of coming competitions. The "hochstart" may soon put the glider in an endurance class equal to the powered model for it launches them to high altitudes. Contest rules are now those of the F.A.I. and specify fuselage cross section of L squared/200, weight rule 15 grams per square decimeter, or about three ounces per 100 square inches wing area, and maximum of one third the wing area for the stabilizer area.
When we heard of the hochstart in Europe we decided to try it out on this glider. Results were very satisfactory one way, but not the other: Every flight was over 1500 feet in length. That became annoying after the third flight but some little boys soon came to the rescue and they did the chasing.
The hochstart is simple. The catapult consists of rubber and string. A post is fixed into the ground then a twenty foot length of rubber (we used two strands of one-quarter flat rubber) is tied to it. To the other end of rubber an eighty foot length of string is tied, a simple wire fitting being used to attach the string to the model. The flyer walks a few steps backward and releases the model which climbs in an arc. When it reaches its maximum height it goes into a level position, the string falls off and the model goes off on a thermal hunt. The altitude obtained is about the same as the length of rubber and string. The official length of catapult length is seventy‑five feet of rubber and two hundred twenty-five feet of string, so it is not so surprising that gliders may become real endurance models and powered models may have a surprise coming some day.
One mistake every beginner makes is using too much rubber tension and as a result the model will not be in a nice nose-down position when the string unhooks but instead will do some fancy stunt flying in the way of loops and rolls and also waste some material in the glue can.
Another point is to do your first flying when there is no wind, evening time is usually good, so that the flying faults may be more easily seen and ironed out. Later, when enough experience is obtained, increased rubber tension and wing and tail warping similar to hand-launched gliders can be done. We were able to get twice the altitude a hochstart is supposed to give doing this, but it is tricky and it will be to advantage to correctly "learn how." We think that the hochstart and the American way of trimming hand-launch glider models may turn into a good advantage. Flying in a wind has its problems especially if the model is adjusted to glide, for very little rubber tension is required as the model goes up like a kite. The Italian trick to slow up the climb is to tie a small stone to the string near the wire hook. Holding the outside wing low to the way the model circles; or instead of launching directly into the wind, taking about four steps to the right for a right circling model and left for a left turn model, may be of value in wind launching.
In constructing the glider, make cardboard templates of the wing tips, fuselage body, rudder and stabilizer. The wing is made from semi-finished Jasco glider stock. Mark out the tip shape and remove excess with razor. Carefully sand and finish to shape with various grades of sandpaper up to six and ten nought. Glue the wing together and when set rub in two coats of glider polish. Cut out and shape the fuselage body, boom, rudder, stabilizer and its rest. Do not round out the fuselage body top completely but leave it flat where it is joined to the boom. Drawing two lines the width of the boom will help construction. A jig-saw will help cut out the wing slot in the boom. Glue together the body, boom, stabilizer rest and rudder. The boom must be sanded after the gluing. The wing is glued to the boom and then the stabilizer which is slit to fit the rudder. The wire fitting should be securely glued on.
The entire model is now given the final finishing touches, joints like the wing and the body-boom fit should be reglued and everything is polished. Hand-launch the model and correct any turns, diving or stalling tendencies. For balancing the model a section is cut out of the fuselage body and pieces of lead are put in as required. Scotch tape is used to seal the opening.
We used a silver finish on the model and it may be the answer as to what color contest models should be. Red is the present favorite but here is the point for silver: Red powered models have been observed to be all right to a certain point but when it is out of the color range and becomes a diminishing dark spot the flyer looks for the flashing flicker of the polished propeller for guidance. In other words, on long distances it is the flash and not color that is superior, a sort of helio-graph effect. It has worked out that way for us anyway and equally well on light or dark background, for we would have lost the model dozens of times, especially in the evenings, if it was not for that flash effect.
And now coming back to the model, hook up the catapult, step back about five paces and release the model. It should climb about seventy-five feet, release and glide straight ahead or perhaps with a turn. Then experiment ahead as you please, but don't forget: In the beginning fly with no wind and little rubber tension. It must be remembered this "hochstart" glider procedure is new and this article serves as an introduction. The pleasure of improving the design, flight, stability and performance of this glider branch is left to you, for the author must keep up has reputation for being a lazy fellow.
[ Home ] [ Previous Plan Pages ] [ Special
Things ] [ Earl Stahl Plans ]
