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IntroductionThe Asa Branca is a small R/C glider that is very simple - the wing is constant chord and the fuselage is a basic box. Eleven year old Leonardo says he built the model just for this contest and it's his favorite model. I find simple models like this one to be very attractive in their basic functionality with no frills. This model has "light" written all over it. I would think given a field with some decent thermal activity you could hand launch this model and get reasonably long flights without using a hi-start or winch. But then I don't know much about gliders so that idea may just be fantasy. Text, photos and linked photos that follow are Copyright Leonardo Caio de Ladalardo Martins
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About the Asa Branca(Asa Branca translated to English is "White Wing") I am from Brazil and have been a modeler since I was 5 years old (I am now age 11). This is my first model using radio control equipment. I love to make my own design models built in balsa only. Asa Branca the name is from a Brazilian bird that represents peace. This model presented a big challenge to me. I had a little help from my dad on the design, of the wings but, the details, sequence and build method come from me. The biggest problem with small gliders is the weight, so Asa Branca has a target weight of no more than 8 oz ready-to-fly.
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WingsFor the wings I chose the AG 45 airfoil in a constant chord planform. This helps to maintain the Reynolds equally across the span of the wing. In this case the number is approximately 70k. I decided to use 1/32 sheet balsa over the upper surface and space the ribs 1-1/2" to avoid the covering sag between ribs. I cut 40 identical ribs using a template. I don't like the balsa burn so I cut the ribs from 3/32" medium balsa using an X-Acto knife. I used the Profili2 program to plot the airfoil. I printed the pattern and glued it to plywood which I cut and sanded to make the template. A big problem was shape the leading and trailing edge but nothing that a good X-Acto knife cannot take care of.
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FuselageI chose to build the fuselage from 3/32" hard balsa with internal doublers of 1/64 plywood. I don't like pod and boom fuselages. There are too many design problems - choose a light tube for the boom, carbon fiber is expensive, etc. To build the fuselage my way I must pay the penalty in weight. This is too bad because I had to put many grams of ballast on the nose but still the Asa Branca is a very light model.
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Tail GroupThe tail group was built using 1/8" hard balsa strips. A standard tail design was the best solution to avoid tail heaviness from a long tail moment. The controls are not pull-pull. They are pull in one direction only. A spring pulls the elevator up and a single Spectra line pulls the elevator down. The same system is used for the rudder with a spring pulling one way and Spectra line from the servo pulling the other direction.
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FinishI use Polyspan covering. It is light and very tough, despite the dope and others aromatic solvents. The final weigh of the empty model is 5 oz without equipment. The receiver, servos, batteries and ballast are the rest of the weight.
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Flying the Asa BrancaWith the help from my father, we used a Hi-Start for the first flight. The model climbs vertically. The spring on the tail works nicely. The model is a good thermal sniffer and very docile to all commands. This project was born to take part of Airfield Models contest. It is a good model and at this moment is my favorite. You know, small people With small model. I did not make photos of building method because of little time between school and my work bench. My design and flight abilities depend on my schooling. Maybe one day I will be an engineer and I could design something better than Asa Branca. Leonardo Caio de Ladalardo Martins Brazil
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JudgingI was working on these pages at my work one night and all the ladies there fell in love with Leonardo to the point where I had to politely ask them to shut up about how cute he is. I'm not judging cute builders. I'm judging model airplanes! It was so bad that I had to put it away and finish at home. Ok, onto the judging model airplanes part... This is another design I really like. It's a simple glider having a box fuselage and a constant chord, polyhedral wing. Two things kept Leonardo from placing higher (and neither of them were jealousy that he's cuter than me). The first was that he had help designing this model. Apparently it wasn't a lot of help but team designs are not allowed and I had to decide whether or not to disqualify this entry. I chose not to because he said that the only help he received was with drawing the plan but the design is his. Also, I doubt too many eleven year olds would know how to draft a plan they could build from even if they are fully capable of cutting out the parts and assembling them. So I gave him a break. And it's the only break I'll ever give in that regard. The second thing was lack of construction photos. Leonardo said that he had to balance his time between school and this contest. If he were really motivated he would have dropped out of school just to build this model because what's more important anyway? In all seriousness, the only way I can judge a model for a contest like this is to have people ship it to me or I have to go by the photos they submit. Leonardo went back and built mock-ups to show a cross-section of the wing and one of the fuselage. Leonardo states he used spring-loaded control surfaces. The spring pulls them one way and a string from the servo pulls them the other. That is an uncommon method of moving control surfaces and one I've never seen in practice. I would have liked to see how he did it and would like to see how it works in flight. Leonardo sent me a video but I couldn't get it to play unfortunately. The aircraft looks very efficient and has a very low wing loading. If Leonardo knows how to find a thermal I think he could keep this model in the air as long as he wants after a modest altitude launch. Leonard's dad, Antonio, is an excellent builder which means Leonardo has the advantage of an in-house mentor who is not only enthusiastic, but extremely experienced and skilled. As long as Antonio can keep girls from distracting Leonardo in upcoming years, Leonardo will be a builder to watch. Congratulations on your beautiful Asa Branca, Leonardo. You and your father just need to remind each other to document your builds. We all want to see them!
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Back to 2006-2007
Design and Build Contest
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Copyright © 2007 Paul K. Johnson
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