Flying for Fun

DB Mathews WOOD information about balsa going refresher old hands basic information newcomers am doing kit review another magazine design uses great deal sheet balsa its structure plywood balsa above average wide variances grade weight still exist kit box individual sorting must done best utilize supplied material project reminds some long-known often-ignored realities about balsa optimum strength durability must select grade kit wood basis use An old adage states straight-flying models built straight add cant expect build straight wrong wood Have ever observed someone sorting through sheet balsa hobby shop yet buying builder has specific use mind type balsa suitable or may hoarding good stuff future use balsa created equal Wood selection governed three factors density weight grain trueness build kit well needs skills sorting wood prior using Density weight single sheets balsa vary much 100% variance still matter grams Therefore realistic expect worker very closely grade wood weight mass-produced kits reasonable prices difference weight adds up quickly great deal balsa used structure instance having heavy wood wing panel will result out-of-balance wing postal scale very helpful available least try develop two stacks contalning wood used wings shuffle until both stacks feel equal weight design tends tall-heavy dont use heavy sheet tail structureuse up front model has sidewinder engine mount try select balsa slightly heavier wing side opposite engine Also considered direct proportion between wood weight strength Choose heavier stronger strip hingelines elevator stabilizer softer strip leading edge etc Grain Balsa grain determination acquired visual digital skill A-grain sheet has long fibers appear long grain lines very flexible across sheet allowing bend around curves easily splitting Because properties warps distorts easily A-grain balsa well-suited sheet covering rounded fuselages wing leading edges forming tubes Hand-Launched Glider fuselages good choice flat fuselage sides allsheet wings ribs formers does die-cut cleanly C-grain wood also called quarter-grain has moffled speckled appearance Its best flat surfaces ribs formers its very stiff across sheet die-cuts cleanly its warp resistant Dont cross-use A- C-grain balsa can avoid B-grain could also called mixed-graln given sheet may light C end heavy other B-grain has some properties C bulk wood contained given balsa log therefore represents major portion wood kit required grade wood basis compromise application use most-flexible sheets stiffest C Use flexible sheet wings leading edge stiffer sheet trailing edge Construct fuselage sides C-grain sheeted turtledeck A-grain Blend heaviest lightest set sheets ribs strip wood side model Strip Light balsa much difficult heavier grades machine dimensional strip remains relatively straight kit Thats contemporary kits use bass spruce major spars Wide variances density strength present kit balsa strip select wisely serious builders balsa stripper can used create exacfly what wanted selected sheet balsa stripper indispensable builder messes up last remalning piece kit Trueness term intended reflect stralght across edges sheet strip does refer warps multidimensional defects Wood warped badly will lay level side should discarded Otherwise finished structure will contain internal forces will eventually result warped surface other hand sheets will usually have uneven edges sheets will distort later no matter precisely cut factory joining sheets wider-than-stock requirements edges must trued create neat glue seam avoid warping Thine Own Self True Several techniques available truing sheet edges before joining including running stack through table saw using lapped-edge sheeting works best has around years yet builders dont know about procedure requires steel straightedge available several sources including Sig dealers SH236 SH248 Dont attempt procedure good steel stralghtedge Pin sheet balsa top another outside edges closely matched possible Use steel straightedge sharp hobby blade #11 cut through both sheets being careful keep blade vertical held tightly against steel Butt two cut sheets together should match very closely minimal gap rejoin recut until have poor luck attempting block-sand out bad fits dont recommend Mark two edges pencil arrows repeat other edge needed Lay sheets flat surface tape edges together side masking tape running lengthwise Open hinge gently flowing medium cyanoacrylate along edges Place two sheets tape-side down flat surface wipe off excess adhesive spray accelerator Remove tape sand seams sanding block October 1997 83 Extremely lightweight structures such require careful wood selection provide adequate strength fine paper should look good next time need make five-inch sheet out three-inch balsa try simple technique Cheap Please interpret comments criticism kits manufacturers Everyone should appreciative effort development expenses manufacturers put new products pet peeves someone saying look cheap kits back Cost related purchasing power bought first engine 1945a Vivell 35 cost $1875 hardly cheap bought money saved making 35 hour bagging groceries Considering minimum wage now $450/hr engine cost equivalent $24256 contemporary box-boy dollars Reversing equation kit am reviewing sells roughly $24256$1875 1945 box boy dollars No model kit era could come close quality prefabrication hardware design Therefore actually cheap Vivell very expensive example says much about contemporary kits equipment doesnt 4Robart Gear features compact design tougher lighter weight retracts Pneumatic Mechanical Retrac mid-size models Retract Angles 700850900 Forward thrust Nosegear Supported full line RoboStrut straight and complete Robart F Air Control Systems Backed Over 25 y famous Robart Relial 84 Model Aviation s being trued joining Two balsa sheets stacked metal straightedge hobby knife sharp #11 blade Trued edges joined masking tape Should lay flat withEdge flexed open along tape hinge bead medium CyA used tight joint rejoin recut until doto join Laid flat excess adhesive rubbed off