Ditinho

Ditinho is an electric glider I designed and built specifically for the duration competition IX Vale-Tudo held on 2005.05.15 at the beautiful field of AIA in Itú-SP.
The competition rules called for 3 duration flights limited to 20, 20 and 40 minutes respectively, where points where awarded as seconds of flight divided by battery weight. Competitors where only allowed into the the 40 min flight if they had maxed out the first two rounds. So... my plan was for the smallest possible plane that could fly for 20 min, just to make it to the last round; if it couldn't make the 40 min flight that was not a problem since a plane that landed after 40 min with battery to spare carried too much battery on that round... one that landed with an empty smaller battery has used it's energy more efficiently towards earning points.
The plane was a success, it flew the first round with a 25g 450mAh 2S LiPo battery pack and the second with a 250mAh 2S battery that weighed just 14g! I started the last round with a comfortable lead but at about 8 min into this flight the Berg*4 rx failed me while overflying the field where there were at least other 15 txs on... the plane went into a dive and hit the ground! Andre Yamin made a 36 min flight with his similarly built VTzinho using a slightly heavier 450mAh battery and made it to the 1st place leaving me in 2nd.

Specs

Wingspan: 1.08m
Wing-area: 14.85 dm2
Weight: 165g (with 250mAh battery)
Wing loading: 11.1 g/dm2
Servos: 2 Waypoint 3.7g
RX: Berg*4 microstamp
ESC: CC Phoenix 10
Motor: Aircraft-World's DIY CD-ROM motor, stock winding
Prop: Graupner 4.7*2.4 folding prop
Battery: 250mAh ou 450mAh 2S LiPoly
Current consumption: 1.8A WOT

Quick link to pictures in this page:

Wing

Fazendo os cortes na longarina para receber as nervuras Cutting the rib slots in the spar

Nervuras cortadas, perfil AG03 de 6.25% Ribs cut, AG03 6.25% airfoil

Todas as nervuras, ainda faltava acabamento e cortes pra encaixar na longarina All the ribs. Still needed finishing and the slots to fit to the spar

Inicialmente eu pensei em usar no bordo de ataque, por baixo do chapeamento, uma vareta de fibra de vidro de 1.8mm de diametro, entao fiz esse corte redondo na ponta de todas as nervuras pra receber a vareta. Depois percebi que a vareta é muito pesada, seriam 6g só de varetas, o que dį mais de 10% dos 50g que eu espero como peso final pra essa asa pronta e entelada, entao mudei de ideia e usei uma vareta de balsa de 1/16 por 1/8. De 6g caiu pra 1.65g e elas ainda vao ser lixadas... Pra prender as varetas eu apenas fiz os cantos nessas mesmas cavidades. At first I was going to use a 1/16 round FG rod for LE, under the sheeting, and that“s why I did this round cut on the front of all the ribs. Later I realized these FG rods weighted 6g which is more then 10% of the 50g weight target for the completed wing, so I replaced these by much lighter 1/16 by 1/8 balsa sticks... only 1.65g before sanding.

Plainando a vareta de balsa que vai ser o bordo de fuga. Note os arames de aço em volta da vareta que servem de guia pra limitar até onde a lamina vai. Depois de plainar passei uma lixa usando as mesmas guias de arame, fica perfeito e homogeneo em todo o comprimento da vareta. Preparing the TE. Notice the piano wire jig for cutting and sanding

Prendendo as nervuras na longarina Ribs getting positioned on the spar

Estrutura pronta Basic structure is ready

Prendendo a parte de baixo do chapeado Lower sheeting

Chapeado de cima preso apenas com fita fazendo uma dobradiça onde o chapeado encontra a longarina. Nesse ponto eu abri a dobradiça, passei CA medio (mais tempo de cura) nas linhas onde o chapeado encontra as nervuras e o bordo de ataque e fechei. Depois vou passar CA fino nessa aresta dao chapeado que encontra a longarina Top sheeting, hinged with tape. At this point I spread thick CA glue on the sheeting, on the area of contact with the ribs and LE. Afterwords I“ll spread thin CA on the line where the sheeting meets the spar (under the temporary tape hinge).

Colando o chapeado de cima Top sheeting

Perfil do bordo de ataque logo apos o chapeado (em cima) e depois de lixar (em baixo) Wing leading edge just after sheeting (top) and after sanding (bottom)

Colando as semi-asas com o diedro de 12 graus de cada lado Glueing the two semi-wings with a 12 degrees dihedral angle on each side

Entelando Covering

Entelagem da parte inferior pronta e filetada. Note o peso de chumbo para contrabalançar uma pequena diferença de peso entre as duas asas Bottom covering ready and trimmed. Notice the lead used to counterbalance the small weight difference between the two wings

V-tail and boom

As duas partes da cauda em V, inicialmente apenas balsa lixada num perfil proximo do HT-05 The two tailfeathers of the V tail, at this point just balsa sanded to a profile that resembles HT-05

Preparando para laminar com fibra de vidro Preparing to glass the tailfeathers

Sanduiche de (de baixo para cima): madeira, depron, uma tecido sintetico bem macio, papel nao aderente ao epoxi, tecido de fibra de vidro 0.75oz/yd2 impregnado com um minimo de resina epoxi, superficies da cauda em V, tecido de fibra de vidro com epoxi, papel nao aderente ao epoxi e em seguida viria o fechamento do sanduiche Sandwich with: MDF wood plate, depron, soft sinthetic cloth, wax-paper, 0.75oz/yd2 FG cloth with as little laminating epoxi as possible, balsa tailfeathers, FG cloth, wax-paper and on top of that would came the same layers as in the bottom.

Prensado com bastante peso por 24hs Firmly pressed for 24hs

Resultado depois de pronto. O tecido de fibra de vidro foi aparado com estilete, e a parte de balsa que ficou aparecendo foi reforçada com CA fino e lixada. End result. The FG cloth was trimmed and the balsa edges were reinforced with thin CA and sanded

V-tail pronta V-tail ready

Peça de balsa ajudando a manter o angulo de 106 graus e reforço de fibra de vidro. Tem outro reforço como esse em baixo do angulo. Balsa stick helping to maintain the 106 degrees angle and a FG reinforcement patch. There is a similar patch on the bottom side

16g incluindo o boom de fibra de carbono de vara de pesca de 48cm 16g including the 48cm long fishing rod CF boom

Pronto e lincado. Ready and linked

Fuselage pod

Planta do pod. Inicialmente eu tinha imaginado um pod diferente, maior e mais complicado, mas graças à uma sugestão do Andre Yamin eu mudei para esse desenho atual, que é muito melhor. Pod sketch. At first I had came up with a different, more complicated and larger pod but thanks to Andre Yamin´s advice I changed it to the current configuration, which is much better

Esse foi o resultado final (não tenho fotos da montagem) This was the final result (I don't have pictures of the build)

Dois servos Hyperion 3.7g, ESC CC Phoenix-10, rx Berg*4, motor de CD-ROM DYI da Aircraft-World, helice Graupner 4.7*2.4 Two Hyperion 3.7g servos, CC Phoenix-10 ESC, Berg*4 rx, CD-ROM DYI motor from Aircraft-World, Graupner 4.7*2.4 folding prop

Flying