|
||||||
|
|
SCALE VIEWS VOL. 3
JERRY HOLCOMB’S DEWOITINE 338 For several years I have been following the progress of my friend Jerry Holcomb’s Dewoitine 338. This unusual model replicates a French trimotor airliner first flown in 1936. Only about 30 of them were ever built, and all were operated by Air France on European, Asian and South American routes, which explains why it is not an airplane with which many US modelers are familiar. Jerry recognized in it the promise of an ideal subject for a successful multi engined electric powered scale model, and drew his own plans. Jerry made the first flights back in September of ’99, while a few of the non-critical details such as landing gear doors still had not been installed. One of the flight photos you see here is a shot I took that day during the very first flight, while Jerry was busy checking out the new machine prior to making that all-important first landing. It turned out to be a real airliner-type arrival…smooth and gentle, with a little extra speed down final and a nice roll out on the local club field’s paved runway. Since then Jerry has gone on to finish the detail work, which paid off (so far) with a Fifth Place win at the 2000 Evergreen Scale Masters Qualifier and First Place in Designer Scale at the 2001 NW Model Expo at Puyallup. Here are some “tech specs” from Jerry, who constructed the airplane from his own plans that were based on three view drawings and photos of the full scale subject. The model is built to 1/12 scale, with a wingspan of 96”, and is based on “traditional” balsa bulkhead and stringer structural engineering. The outer skin is, as Jerry puts it, “a special epoxy impregnated paper, not commercially available, that I have been experimenting with.” The paint finish is Model Master “metalizer” enamel, a spray-on product developed for plastic scale modelers, that can be buffed to a high degree of metallic sheen. It is, as Jerry notes, not fuel proof, but this is of no concern to builders of electric powered models. Power for the D.338 is three Model Electronics Corp. (MEC) Turbo 10-Plus motors running through MEC SuperBox gearing at a 6:1 ratio. Each motor uses a separate MX-80 speed control and its own 10 cell MEC Power Tube using 3000 mAh NiMH cells. Jerry built his own custom retractable landing gear system including spring compression struts and also installed split flaps to replicate the full scale system. The outer wing panels are removable and each contains its own aileron servo. The rudder, elevator and tailwheel, which also has its own spring compression strut, are all controlled by closed loop cables. Jerry provides a flight report as follows: “Flight notes: Takeoff is best done with no flap. Significant left yaw occurs on power application during takeoff until tail is well up. Like most multi-engine models, takeoff can occur much sooner than you would expect. Gear retraction/extension cycle is slow and no significant trim change occurs. Ailerons are very effective initially, but sustained roll response is slow. Airplane is well damped in all axes, although directional stability is not as high as would be expected with the long tail moment arm. Model can be flown quite aggressively and it is difficult to restrain the pilot's urges to do so. Flaps should be used on landing. Flap action is also slow and no retrimming is required. Approach is stable with flaps down. Gear extension reduces directional stability slightly. Model is normally flown with APC 12-6E props to keep speed scale-like. These props only draw about 26 amps static, so flight times on the 3000 mAh cells is more than adequate for a scale flight routine. Model has actually been flown very little. Perhaps 15 flights total to date, including the 5 at the Evergreen Qualifier in 2000.” NICK HAS THE WRIGHT STUFF That one was too good to pass up. Nick Ziroli, perhaps better known as the designer of all those really big military scale jobs intended for gas and large glow engines, has been getting involved with electric power as well. In fact, Nick brought the little Speed 400 powered Aeronca Champ that he had recently published in Model Airplane News to the 2000 U.S. Scale Masters at Dayton and during a quiet time after we had both finished with static judging we flew his Champ and my little Astro 010 powered Ryan PT16 that I described in the last SCALEVIEWS in a little tail-chasing exercise that had quite a few of the other competitors coming over to find out why they couldn’t hear our engines. Nick sent along these two images of a Wright Flyer he has been working on in anticipation of the upcoming 100th Anniversary of Orville and Wilbur Wright’s successes in 1903. As he mentioned, “there has been a lot of interest in Wright Flyers…lately. Some people who know I am working on one have mentioned it. I would like to have some pictures available.” Nick went on to suggest that I might want to include these two in SCALEVIEWS . He included some info on the model you see… at 1/12 scale, wing span is 40". Weight without motors or batteries but including all R/C is 4 ½ oz. Wing area is about 460 sq. in. Covering is Buff Litespan. Power may be 2 Astro Fireflys with 16-1 reduction and 8" counter rotating props…if that isn't enough, maybe 2 Titanic 280's. Extension shafts are easy to do on them.” You can contact Nick about the Wright project via my FlightImages email…I will pass any correspondence on to him. ODD STUFF FROM JERRY Jerry Holcomb has a “thing” about unusual airplanes…I have seen him show up at the field with contraptions that had all of us piling out of cars to see what he had come up with “this time”, but the Vought XF5U he is working on now is in a class by itself. He has been working on this prototype scale model of a really unusual “X” fighter of the late WWII period, and as the pictures prove, it really flies. I saw the model myself when Jerry brought it up to the NW Model Expo at Puyallup. He is working on a larger version that we here in the Northwest hope to see during one of the first area electric fly-in’s early in May. Jerry is not ready to share more tech info yet…just enjoy the pictures. If the bigger one works OK we may collaborate to offer plans right here at FlightImages. IVAN’S NEW MOSQUITO You saw pictures of a couple of Ivan Pettigrew’s multi engine scale jobs in Doug Burt’s North o’ 49 column last time (check the link to that issue on the FlightImages Homepage if you missed them). This time around Ivan has sent along some info on his new DeHavilland Mosquito for me to share with you. The flight photo is actually of his old “Mossie”, which has since been sold to another modeler. Ivan is now flying the airplane, but has not yet been able to get good flight photos of it. (Ivan says…) Following are the specs for the new Mosquito.: DH Mosquito T III. 1/9 scale. Span 74ins. Wing area 825 sq ins, airfoil, Eppler 374 with NACA droop outboard. Length 55.4 ins. Weight with eighteen RC-1700 cells is 114 ozs for wing loading of 20.0 oz/sq.ft. Trinity Ruby 16T motors with 6.2:1 ratio Superboxes drive 14 x 12 APC electric props at 4,800 RPM. Current draw 31amps. Retracts (are of Ivan’s own design and construction - BB) I'll attach a picture of it during construction. It weighed 39 oz. as shown with retracts installed, but no servos or radio equipment. I took this photo myself, but should have mentioned that the earlier one I sent was taken by Hal Norrish. Sorry I don't have any in flight photos yet. See you later.......Ivan NEXT TIME I’ll try to have some photos and a flight report on my new ¼ scale Aeronca “K”, the one that is featured as a “work in progress” in the PLANS section. As this material is being written, the “K” is about ten days of work away from first flight, weather permitting. Remember, SCALEVIEWS wants info on YOUR electric powered scale airplane…let me know what you are working on.
|
|||||
