MAY '99 - VOL. 4., NO. 4
Bleriot XI Electric
Conversion Part1
Bleriot XI Observations
RC-04FR BLERIOT XI DATA SHEET
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Saturday, September 19, 1998, couldn't have been a better day for the
Bleriot Xl's first flight. The morning was slightly overcast, 75
degrees, with only a slight breeze blowing down the runway from right
to left. Assembly time on the Bleriot XI is less than 10 minutes. The
assembly time was minimized because I had put a drop of white glue on
each locknut for the bracing/control wire clevises, thus eliminating
any surprise changes in length.
What a prestigious venue the KRC provides for any model's first flight. KRC this year hosted almost 260 pilots and their approximately 800 aircraft. The spectators numbered over 1500. After topping off the charge on the motor pack and taking the obligatory static shots of the Bleriot XI and pilot, it was time to fly. Rhode Island's own Don Bousquet was "volunteered" to assist with the launch and my flying buddy, Ron Farkas, was my caller. As previously arranged, a number of photographers made ready for the flight, and out of some sense of reverence, the normally crowed sky was void of any models, and the Bleriot XI was the only craft on the runway. As Burf Tunnell had suggested, the Bleriot XI was set up to take of£ at full throttle, directly into the light breeze. Additionally, I mixed 50% rudder into the aileron channel to help with coordinated turns (one less thing to think about on a maiden flight). The moment arrived. I cycled the throttle from of£ to full, to of£ then went to full throttle and nodded for Don Bousquet to release the Bleriot XI. The plane leaped forward and yawed to the left. I was prepared for this and added right rudder to quickly straighten out the plane. It broke ground in less than 50 feet. In my mind the worst was over, the Bleriot Xl was airborne and climbing out at over 30 degrees. The first turn was smooth and appeared to be coordinated, with no adverse yaw apparent. The second turn was banked over at almost 45 degrees with no noticeable side slipping. Now I was flying back up the runway at approximately 150 feet of altitude and a tail-down attitude was quite noticeable. I added two clicks of down trim to raise the tail and then reduced the throttle slowly to 3/4 to maintain altitude. The second flyby was at 1/2 throttle to reduce altitude for a photo pass, and the plane remained very stable. The third and last scheduled flyby before landing was at 8 to 10 feet and very slow, less than 25 mph for a perfect photo pass. Then it happened. The motor stopped, the nose dropped and only immediate full-up elevator prevented disaster. However, the spring landing gear was severely tested, causing the left struts to bend and both tires to come off of their wire wheels. When the plane came to rest, a plume of white smoke could be seen rising from the nose. Realizing the throttle was still on, I moved it to the off position, but I knew this was not good. Whew... though only two minutes and twenty seconds, all in all it was a successful maiden flight. And then it hit me. The flight was in front of almost 1500 people, the camera shutters were making more noise than the Bleriot XI and no other planes were in the air. The post-mortem confirmed my worst fears; the motor could not accommodate the approximately 600+ watts of input power for 3 minutes, causing it to throw a rotor magnet. This was my fault, trying to push the motor at too many amps. To add insult to injury, I smoked the electronic speed controller because there was no fuse. Stung twice by an electric sailplaner's mentality. Fortunately, the Aveox people were at KRC and Matthew Orme saw the flight. After removing the motor and electronic speed controller, Matthew disassembled the motor and found the thrown magnet. This indicated severe overheating, probably caused by the excessive drag of the Bleriot XI, thus apparently making the 14064 Y / Planeta a marginal choice for this application. To correct the situation, Matthew suggested I substitute a 1412-2Y with a 3.7:1 Planeta gearbox because it delivers 1470 rpm/volt; almost identical to the 1406-4Y's 1500 rpm/volt. Therefore, the same propellers can be used with the 20-cell pack and, since the 1412-2Y has four times the amount of copper, it can handle the amp load with no problem. Matthew and Aveox provided a new motor and a new H160 electronic speed controller. (H160 SC will accommodate 4 to 32 cells.) They obviously took pity on this electric sailplaner and his ambitious project. |
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We also noticed the motor case had been chafing on the Aero Vee mount, indicating the tie-wraps were not capable of completely securing a motor of this power. Sam Stitzer, the motor mount designer, also had a booth at KRC. Sam suggested I change to his MB-l mount, which has a solid bottom with no cutouts for external brush housings. At the base of the V, where the motor case touches, he suggested I apply a coat of PLASTI-DIP (the rubber material used to coat tool handles), thus providing more grip at that location. Additionally, he suggested I use the supplied hard nylon tubes to secure the motor. They are wrapped around the motor, front and back, and secured by four socket-head sheet metal screws. My flying buddy, Ron Farkas, further recommended the nylon tubes be inserted into silicon fuel tubing, thus providing a good rubber grip over a half circle fore and aft on the motor. | |||||||||||||||
| Not being one to fix planes at a competition, I opted to do this work back home in Florida. The Bleriot XI stayed on display at KRC for the next day and a half. Its flight on Saturday morning obviously caught the attention of the KRC Contest Director, who awarded the Bleriot XI first place CD's Choice, on Sunday. A beautiful engraved desk clock was presented to me for winning this award for the two-day event, over almost 800 other models. This was a real tribute to the plane that Goran Kalderen manufactures in the Philippines, and Bob Brooke of 3 Sea Bees Models imports. | ||||||||||||||||
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Subsequent Motor The Aveox 1412-2Y/Planeta was installed using the AERO VEE MB-l mount, following both Sam Stitzer's and Ron Farkas' suggestions -a much more solid setup. Because the Aveox 1412-2Y /Planeta is 4 ounces heavier than the original Aveox 14064Y /Planeta, the battery had to be repositioned 0.510 inch rearward (behind the firewall) to maintain the 39% rearward center of gravity (CG). A 30 amp automotive mini-fuse was installed in the positive lead between the motor battery and the electronic speed controller using a Sermos@ Master Arming Switch with the side mounts (fuse holder). It was a hard lesson this electrical sailplaner learned. Except for competition duration or pylon models, where weight is especially critical, all electric powered models should contain a fuse. As with the smaller Aveox motor, I felt compelled to test the same propellers on the Aveox 1412-2Y /Planeta. The table above shows the results of this test. Observations : 1. The 13x8 Zinger is still inferior to the 13x7 Zinger. 2. The 13x7 Zinger appears to be the propeller of choice because it provides almost 80 ounces of thrust (79 oz) at just over 30 amps (31 amps), while the 13x8 Master Airscrew -electric only, provides slightly more thrust, 87 ounces, but at a cost of 7 amps more. 3. The 13x6 Zinger should be the ideal, and 69 ounces of takeoff thrust should be adequate. A 26 amp maximum draw would not penalize duration. Even with the above observations, my first flight using the 14122Y /Planeta was with the 13x8 Master Airscrew propeller (electric model), because it provided the comfort of excess takeoff thrust. This series of five test flights took place at the Palm Beach Bush Pilot's field in suburban West Palm Beach, Florida, hosted by their president, Andrew Levy. The temperature was in the high 80s, with winds down the runway at 5 to 10 mph and clear skies with puffy clouds. The Bleriot Xl was released into the wind with the motor at full throttle and it leapt into the air in less than 30 feet. The throttle was quickly reduced to 2/3 and the flight continued without incident. The tail down attitude was again apparent. The plane landed after a 3-minute flight and I was horrified to find the battery pack had less than 300 mAh remaining. The 13x8 Master Airscrew electric propeller was just consuming too many amps for this application.
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The second flight was with the 13x6 Zinger. This propeller held the
potential for low power consumption during cruise, but only if it had
enough thrust for takeoff. Again, the plane was released at full
throttle, directly into an 8 mph breeze. The plane accelerated slowly
and required a substantial amount of right rudder to stay on track,
then struggled into the air after more than ISO feet of takeoff roll.
The climb rate was quite shallow, with only the slightest reduction of
throttle necessary to level off. After one circuit of the field, the
Bleriot Xl landed without incident, except for my shaking knees. The
13x6 Zinger did not work well, probably because the propeller could
not provide the two separate and distinct tasks needed; that is, to
deliver ample takeoff thrust and then an efficient cruise thrust.
Before test flying with the last "best" choice, the 13x 7 Zinger, another flying buddy, Nick Spagnuolo, suggested I try a 13x 7 Rev-Up four-stroke propeller that he has been using very successfully with the same Aveox 1412-2Y/Planeta combination. I accepted this suggestion from a knowledgeable source and tried it. The 13x7 Rev-Up four-stroke has a wide blade and fairly thin airfoil section, especially when compared to the 13x 7 Zinger. The only reservation I had in testing this propeller was that RevUp, the company, is no longer in business and it is unclear if these propellers are still available. |
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The first test flight with the 13x 7 Rev-Up four-stroke propeller was
terrific. The plane, at full throttle, took off into a 10 mph breeze
in less than 50 feet, and climbed out very well. The tail-down
attitude persisted, but this time I decided to live with it and even
added up-elevator trim as I reduced the throttle to 2/3. This trimming
allowed for very scale-like slow, level flight, and after 3 minutes, a
controlled landing descent was achieved at 1/2 throttle. The Bleriot
XI flared into a two-point landing at nearly walking speed. The plane
was very stable during the entire flight.
Two subsequent flights, using the 13x7 Rev-Up four-stroke, were made, trying various throttle/elevator trim settings. The last flight was 4 minutes long, with 400 mAh remaining in the motor pack. That is right on target -4 to 5 minutes of flight time. Not bad for a plane that is extremely "drogue." It should also be noted the last takeoff was directly into a 15 mph wind. No problems were encountered, and the Bleriot XI was airborne in 15 feet, using a full throttle setting. The tail-down flying attitude of the Bleriot XI was communicated to Bob Brooke at 3 Sea Bees Models, along with my suggestion that a 2-degree increase in wing incidence relative to the fuselage should raise the tail to level in flight. Additionally, the resulting increase in the angle between the wing and stabilizer (decalage) would aid in achieving level flight characteristics at reduced cruise throttle settings. Bob said he would forward this suggestion to his Philippine manufacturer for testing and possible inclusion as a specification change in future Bleriot XIs. Though not flight-tested at the time this article, indications are that the flight/duration characteristics of the 13x7 Rev-Up four-stroke propeller and 13x 7 Zinger propeller are virtually identical. Therefore, if the 13x7 RevUp four-stroke propeller is no longer available, the 13x7 Zinger is a reasonable alternative. Conclusions As one of 3 Sea Bees Models' brochures states.. ."the Bleriot XI also displays magnetic properties. That is, it draws crowds and lots of admirers out of the woodwork." Fellow modelers can't believe that this plane, with its looks and "charming" flight characteristics, is an almost-ready-to-fly (ARF). What a compliment to the Bleriot XI. As for project success, the weight goal of flying at the same weight as the wet-powered Bleriot XI was missed by 7 ounces. However, simulation on ElectriCalc (the superb electric model design analysis software from SLK Electronics) indicates the motor pack could be reduced to 16 cells. This calculation was done using the Aveox 1412-2Y /Planeta motor and the 13x8 Master Airscrew-electric. It provides equivalent flight/duration characteristics and a weight savings of 8 ounces, but the set-up provides less flight duration. This configuration still allows for a 39% rearward CG when the battery is moved forward against the firewall. I may test this in the future. However, is an 8-ounce weight savings important when the "friendly weight" of four additional cells provides increased flight duration? Probably not. Achieving a 4-minute flight with an adequate safety margin of I-minute is very satisfying. Subsequent propeller flight tests and flight refinements, including throttle/elevator mixing, could add to the duration figures. The Aveox power system worked flawlessly, and the RC2000 Zapped Nicad Cells from Diversity Model Aircraft created a motor pack with additional power and additional duration. This combination truly brought "peace of mind" to this project. The Bleriot XI proved very stable in all flight modes when set up as described, and its scale-like appearance in the air is truly breathtaking. The Bleriot XI ARF kit provides an outstanding value. It offers multipurpose flexibility to allow for successful electric conversion. Be the first at your field to fly this unique, historic, stable electric powered aeroplane. It's a different kind of thrill.
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Suppliers worth contacting:
1. Aveox, Inc., 31324 Via Colinas
#103, 2. Diversity Model Aircraft 3. Sermos R/C Snap Connectors, Inc., 4. SLK Electronics, Greensboro, NC 5. Stitzer Model Design,
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Bleriot XI Electric
Conversion Part1>> |
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