Monday, December 23, 2013
M2 flying wing aircraft for medium scale FPV design and test history
I've already done some preliminary drawings of what is presently being called the M2 wing design as seen in these dxf drawings and jpg images bellow: https://docs.google.com/folder/d/0BwHgFeQZDBYLZTAzUEsyRENpVDg/edit
The M2 (was called Z54) will be used in my next phase of my long range FPV aircraft with up to 50 minuets airtime aloft due to it's larger batteries and increased distance flight range. As compared to the S3 wing the M2 has over 2 times as much wing area of 4562 sqr. cm as compared to 2073 sqr cm of the S3. It's wing span is 137 cm compared to the S3 with 89.2. It will carry up to 6600mah 4 cell bats and payloads of up to 1 lb to enable flights with a GoPro cam or other equipment as desired. You might note in the m2_partslist.xls file that I've included parts that can be used to extend the video and remote control range with the needed more powerful 1000mw 2.4ghz video transmiter and a 600mw 433mhz r/c remote transmitter to provide up to 7km and possibly more range if needed with improved antennas as compared to the S3 video gear and transmitter that will provide you maybe up to 1 - 1.5km range. The upgrade is optional. you can still move the video equipment and standard r/c gear from the S3 version of FPV to use this wing. This wing with it's longer wingspan should be more stable than the S3 and could also be used for training if desired. For filming it should also provide a good platform for a gopro cam or equivalent with the original S3 gear to take some cool stable shots. The Z54 is named after the zephyr 54 inch wing span wing, in fact it's really a clone of the top view of the 54 inch wing span zephyr as seen from Team Blacksheep web page. It is also classified as my M2 standing for medium scale version 2. I've made some ruff draft dxf file so I have an idea of the size of things and the material needed to build one. I also did a quick CG calculation to see were that is on my drawings and to see what the wing aria will be. From the preliminary drawing it looks like I will need 2 blocks of 2 inch foam that are 93cm x 39cm. I think I might be able to squeeze 2 wings out of one 2 X 4 X 2 standard block of foam if I'm careful but it seems to be cutting it very close. The drawings I presently have are just traces from photos as seen on the team blacksheep page. The accuracy is +-2 degrees and +- 1cm in some places. I also noted from the video that the wing they use is a 12% thick wing so I could ether us the zagi12 or maybe the TL54. As by luck I already have a zagi wing template that happens to be about the correct size needed at 43cm. Just a bit big but tolerable. The other problem with this size template is also that you have to print the template in two parts as it's bigger than a standard 11 inch printer and A4 paper that we have available and later needs to be glued together onto the template material that will be cute. The desired template size in this case is about 42.cm. So if you would like to try build one before me that's the size you would want to rescale your printed airfoil cord length to. The option to use a thicker airfoil in this case is not desirable as at 12% it's already 2 inches thick and uses 100% of our 2 inch thick foam at the thick points. If your making a template I would recommend the TL54 12%. I've included the TL54 airfoil in the m2 wing picasa image collection. I've also added a parts list that includes the parts to make the Z54 wing into a long range FPV system with ranges possibly up to 6km or more. It assumes you already have leftover parts from the build of the S3 wing that is an FPV trainer and should be flown before you ever build one of these. Also I failed to note on the parts list of the S3 and m2_partslist that you should have purchased the 9X remote control unit for the S3 if you plan on ever upgrading to the Z54 wing and others. If you plan to just fly it as plane without fpv then all the parts for S3 except swap the motor, speed control, servos and propeller as seen on the m2_partlist should be fine. Oh the batteries are also bigger with 3300 mah 4 cell and it needs two of them installed just to fly. I might end up modifying the scale a bit or just create another version M3 wing that will still use 2 of my original 2200mah 3 cell batteries as I've collected a number of them now ( 8 at last count) and I would hate to have to start another collection of another battery type that can't be swapped between my other planes. But to push the range I guess there might be no other way than another battery type. On another note I might have finally found a way to make a center wing junction that will come apart for transport. I found carbon fiber tubes at hobbyking.com of 10mm and 12mm outer diameter with wall thickness of about 1.5mm that I'm told slip into each other. With 2 36cm long tubes spanning cross wise at 30% into the wing junctions or maybe a third joint to have two on the bottom of the wing and one at the top of the wing. With this the 147cm wing will come apart into two 74cm sections. That size would make it possible to continue to transport in my bicycle side bags. Also it opens up the possibility of making a 3 section wing were the center becomes more of a composite wing shaped box to contain electronics and batteries. Until I have a sample of the tubes we won't know for sure but it sounds very promising. And two carbon fiber tubes are only $8.50 making it affordable to at least try. I've added the part numbers of the tubes to the M2_partslist.xls file and plan to give it a try. I also made an almost complete parts list of the Z54 that includes parts needed if you started from nothing including r/c radio and chargers. The total price now of a full system starting from nothing is now up to about $820 USD or 24420 baht. For me to upgrade to a full system looks to be more around $650 usd with the parts I already have in my inventory. I'll have to see what a minimal build price is on it with no FPV or radio equipment. for me will be around $20 or less as I have most the parts in inventory to at least make one fly.
Update Nov 30, 2012 8:45am
I uploaded some cleaned up drawings to my docs.google site. I kept the original files that are called zephyr.dxf as a reference but the new updated drawings are now called m2_wing.dxf and m2_wing.pdf. see link for updates: https://docs.google.com/folder/d/0BwHgFeQZDBYLZTAzUEsyRENpVDg/edit
Update Dec 3, 2012 9:25am
Construction of the now called M2 wing has begun. Yestarday I went and got a few things I was short to begin construction including a block of foam, some clear tape and some coroplast, total checkout cost so far from Friendship market was 160 baht ( about $5.16 USD). Last night I did the hot wire foam cut and some sanding of the wing cores. I ended up using my zagib 12% 42cm core template rather than the planed TL54 airfoil to save some construction time on this first prototype as I already had this template made that was used and tested in the BW1 wing. This morning I edited the cad drawings to simplify how I was going to measure and do the finnal top cuts of the wing. With the added cad info I was able to finish the cuts with no problems or questions. So I went ahead and published the new updated dxf and pdf files as seen: https://docs.google.com/folder/d/0BwHgFeQZDBYLZTAzUEsyRENpVDg/edit the file name is now m2_wingc.pdf, stands for version C. I also striped 4 peaces of bamboo that will be used as the cross and wing core spars in this prototype instead of the planed carbon fiber tubes. The changes to use bamboo spars is not finalized as I had hoped to use carbon fiber tubes to make it break apart for easy transport. This just enable me to do preliminary testing without expensive carbon fiber. So it's all going together quickly maybe done in 2 more days? As I'm exited that the remaining parts from hobbyking are on the way so this will hopefully be ready and possibly test flown about the time the remaining electronics and video equipment arrive from hobbyking. Here's what she looks like so far as compared with the S2 wing behind it:
Update Dec 4, 2012 10:57am :
Today I sheeted the wing of the M2 and also cut and shaped the elivons. I'm now figuring out how I will mount the big motor. I'm more looking at a temp solution not a permanent one just to try it. I won't be putting the battery into the wing on the test flights ether as I'm not sure of CG and I don't have the batteries that I had planed to install in the plane yet anyway. I will try the 4.0mah 4 cell battery I have just attached on top the wing using bamboo under coroplast sheet to velcro the battery on to make it adjustable to try. I think it will be ready for a test flight by late today or early tomaro. How I will transport it is another question so the bike rack might slow a full test flight down by a day. If the Soi 5 beach lot is clear I might be able to do a preliminary test flight there today or tomaro. But they have been putting some shops on the Soi 5 lot that might prevent that from being possible. I also measured the weight of the wing with no elivons or electronics on board just the sheeted wing and the embedded bamboo spars is ony 270 grams. The balsa elevons together are 20 grams. The 4.0mah 4 cell battery is 425 grams. and the big motor with mount and 10 inch propeller is 147 grams. That's now adding up to 862 grams already. So it might be as much as 900 - 1000 grams when it's done. Almost 2X as heavy as the S3.
Update Dec 5, 2012 7:35pm:
I have the M2 almost completed with the motor, ESC, receiver mounted and servo's with elevons working. The only thing not completed is the verticle wing tip stabalizers that should only take 10 minuets to complete since I have the coroplast material in stock. The other problem I found is that the elevator seems to be reversed when I radio tested it. I forget how to reverse this with the elivon mix setting, but I'm sure it will be corrected in about 15 minuets with some research. So it should be ready to fly by tomaro morning. As the bicycle rack is now also ready we might try take it to the stadium field tomaro if all goes as planed.
Update Dec 6, 2012 4:42am:
It's done! all ground tests and trims are completed, big 4.0Ah battery is charged and CG checked with big battery installed. Elevons are now setup correctly with transmiter with new program in transmiter named wing M2. I have exponetial elevon set at 80% and it looks like it has too much throw in the control surfaces that we can later program down if needed. Oh one last thing I will do when it gets light is paint the left wing with my day glow orange strip that I use to distingush the top and bottom of my plane in flight. It is also my trademark as anyone see's a plane painted like that they know it's a 99% chance that it's a scotty proto type plane. I woke up at 2:30am with a desire to work on it and now it's time to take another nap. When I wake up maybe I'll think of more things I forgot.
Update Dec 6, 2012 9:52am:
I got it painted with my day glow and made some safety flags for the rack mount. here's the completed photo before it has ever flown. It will never look this good again. It will soon get banged up and never be so prity as this (here it's pictured next to the S3 wing for size referenc):
As it's completed it's wingspan is now measured at 140cm or 55 inches. That's 1 inch longer than a zephyer wing that we attempted to clone. Close enuf?
Update Dec 7, 2012 6:14am:
Todays M2 flight was not without drama but it had more success than failures. To start the bike wing rack seems to work. If I had glued all the joints it would have been a 100% success but to test it as I thought it would require a few more adjustments , I just used inertube strips to hold the joints together. This worked for about 2km before it's first failure. I added some gaffers tape to continue for the next 10km. The total bike trip distance tested on this rack is now 24km. With the added tape the trip continued and went OK. So I'll finalize the glue joints tomaro. When I got to the stadium field I found a group of a few new people that ended up being very helpful in providing me with the intellectual and moral support I needed. The first flight launch was OK with unpowered throw launch but seconds after take off I felt like I had no power. As I lowered throttle it seemed I would get a little more thrust but later not even that was enuf to continue the flight and had to land dead stick. Landing was OK with no damage. On the ground the problem was detected that the spacer washer I had used in the spinner didn't hold up so the prop was not being spun. But thanks to the ingenuity of my peers they figured out we could use 2 plastic tops off a water bottles that we found as trash on the ground to replace it. With the new spacers in place I did a ground test at full power and with quick changes in throttle to verify that it would work and all seemed OK so we were ready for a second flight. Surprisingly the second flight of the M2 went almost perfect. The take off went OK with a unpowered throw launch as it felt OK I powered it up after the launch and got it trimmed up OK at slow speed. It had a lot of control throw so was a bit squirrelly to start but after it was trimmed it felt very stable. I was mostly flying the flight slow to start but later ran it up to full speed in level flight OK with no problems and still very stable with no oscillation or elivon fluter detected. Top speed doesn't seem very fast I think maybe 55mph in level flight. I'll later take a measurement with my GPS to verify speeds. I did some roles that felt very stable and quicker than I expected but with no problem. Upside down flight went OK. I did some test stalls that were very quick and easy to recover at the present CG settings of 25cm from nose. The unpowered glide test looked good with a very slow sink rate. I then was going to start some higher speed dive tests with the first I attempted to do a loop. But at the pull-up stage of when the nose got to about 45 degrees up from the hard pull up with full throttle I heard a griding noise that was later to be seen was the prop hitting the wing. So it seems I didn't provide the needed clearance for the prop bending that seems to happen more in quick full powered fast vector changes. So the rest of the tests in this flight had to be back to lower power maneuvers. But note before high power tests were stopped I did attempt total vertical climb that I don't think it can do even at it's present wing loading without the video gear installed. I'm not sure what angle it can do yet but maybe around 50 - 60 degrees continuous climb or a bit more maybe is best we can do with this motor prop 4 cell bat combo. At landing It stalled a bit earlier than I expected on an unintentional flare but with no damage. On the next launch it seemed the wind had died down to nothing. With no wind to throw it into it seemed I didn't get enuf speed to setup a good launch and it ended up being a failed attempt. I was able to power down quick enuf to prevent any damage to the wing or prop on this attempt. The battery was ejected on impact but was not damaged as it found some nice soft grass to hit on impact. After this scare and with some input from my consulting crew it was decided to try have someone else throw the wing at launch so I could focus on just the controls. This ended up being a bad idea. I'm not sure why since it seemed to be a good throw but is seems I didn't provide enuf power soon enuf or not enuf up elevator too late. And as just before impact I had the motor up to full speed in an attempt to get it up when the prop hit the ground and broke my only propeller. The only damage to the wing was a bit more foam chunks removed from the prop cutout but only cosmetic damages. On my return home I dropped into my hobby shop and picked up one of the only props the size I could use that was 10 inch 5.5 pitch that was only 70 baht ( about $2.30 USD). I would have liked a bit bigger prop but that's the longest biggest pitch they had in stock. The prop that I broke was an 11 inch 5.5 pitch. We also did some current measurements on the 1155 prop that peak at full throttle was measured to about 30 amps with the 4 cell battery I was using. That was good as I only presently have a 40 amp ESC. So at best maybe we could spin an 1165 or 1250 prop with this ESC if I was careful not to push it unless really needed. So not too expensive of a day with more positive results than negative ones. And with no real damage to the wing so far. On the bicycle trip home with the rack we had a few more failures of the pipe pulling out but that will be corrected when I get them glued together. Another thing I should note as suggested by my consulting crew is that the motor mount needs some screws or other method to fix into the bamboo base to keep it better held in place. The movement of the motor mount is partly at fault of the prop hitting the wing prop cut out section. So I hope to have some needed changes ready by tomaro afternoon to give it another try. Wish me luck! oh I just got the readings from the charger for todays usage of the 4.0Amp battery recharge miliwatts total 1129 in 57:51 minuets. That was used in a total of about 8 minuets of flight and not counting ground testing. So I guess maybe it will fly up to 30 minuets at slow speed if pushed with this battery? But for now I'll keep it to around 12 minuets to see how that goes.
Update Dec 7 12:47pm:
I installed the new 1055 propeller and made some changes in the motor mount with some added plastic straps and two pinning screews to hold it in place to the bamboo mounting plate. Some gaffers tape was also added to prevent the bamboo base mounting plate from possibly changing position. I also added some slots in the bottom of the wing directly behind the rear cross spar to be used as a handle to help get a better throw to get it airborn as I was instructed by my consulting crew yestarday. It's now ready for another test flight that I hope to do later this afternoon depending on if I can complete the needed changes to the bike wing rack to allow me to carry two planes instead of just one. Then if I crash one plane I will have a backup wing to play with. Also with only one battery for the M2 it will provide me more airtime with my present battery inventory with the S3 or S1 wings as a backup plane. Oh since the S1 comes apart it might even be possible to transport 3 wings on my bicycle? I'll look into that possibility later. A thanks goes out to my consulting crew seen in the picture bellow:
Update Dec 9, 2012 9:18am:
Test flight of the M2 yesterday was far from perfect. It seems the new 1055 propeller I installed seemed to be out of balance. At full throttle the motor mount would vibrate. It was still spinning OK at slow speeds so I decided it was worth a try at slow, but I was wrong. The launch went well using the new finger holes to provide a handle gives me the needed airspeed at launch to get it airborne with less of a problem than before. With the limited prop speed I was able to do some low altitude maneuvers for about 4 minuets of the flight with no problem but when I attempted to gain altitude I got it up to about 50 meters before it felt like I lost thrust power. The throttle stick had no effect and I could hear that the motor wasn't making the normal noise that I had heard in the past. I thought I must have another spinner problem and was forced to land dead stick again with no damage and on the tar mat. When I got a chance to look at it closer I noted that the motor seemed hot and also the speed controller was hot. I could smell something had burned in the speed controller. It had that chared silicon smell I have smelled many times in a burned power supply. I let it cool for about 10 minuets before I attempted to try to power it up again for a test. When I provided power the motor would click and rotate to a fixed position and freeze like one of the coils was being powered up on the motor. I quickly discontented the power to prevent the motor from being damaged any more but I think it's probably toasted also. This motor I noted already seemed to have a bent drive shaft since I got it and may have gotten more bent from the last landing that broke the 11 inch propeller. So maybe that's why they put folding props on these flying wings? So I will have to put this project on hold until I obtain a new motor, prop and ESC set. At least we now know that the airframe is flight worthy and stable and worth investing in a new power set. Unconnected to this event my backup S3 wing that I also brought to the field this day also burned an ESC from having put a larger pitch prop on it with a new lower amp 30A ESC I had installed on it. So two for two bad luck today. As I didn't have an amp meter in my inventory yet I had no way of knowing that this could happen. The good news is that my present order from hobbyking.com has an amp meter in the package that I will from now on use to test any prop changes and new ESC with motor installs on the ground before flight. As long as we learn from our mistakes all is good.
Update Dec 25, 2012 3:13am:
Today we finally got some good flights out of the new M2 wing (4 total). The first flight I had a good launch with the finger holes to give it a good throw. I'm able to power up and get it to fly vertical with the new 40A turnigy plush ESC that I got from Nick when a 4 cell lipo battery is used. I'm not sure why the motor spins a bit smoother now. I thought it had a bent drive shaft but I guess it was partly to do with the prop not being balanced properly. After reinstalling it seems to be more centered and balanced for a slightly smoother high speed spin. The winds at the first flight at 1:30pm were a bit above normal and caused me some problems to get the wing trimmed. It was gusty like 15mph with pockets of 5mph to make for unpredictable flight events. Also the first flight I found that the wing felt a bit tail heavy with difficulty to get elevator trim to a stable point as it would purpose. On the second flight I moved the 4Ah 4 cell battery about 2.25cm forward just outside the rear Velcro strap. I had to temp setup a strap in front with some nylon tie raps since the rear strap no longer reaches the battery. With this setting the second flight felt much more stable. One of the bad points is that the M2 wing had a very bad unpowered glide but this is mostly due to not having a folding prop. The big 10” prop spins up even at slow speeds and adds a lot of drag. I might try set the brake on the motor ESC to get a better unpowered glide with a non folding prop that might provide a small improvement. I got a 3rd flight from the 4ah 4cell battery before I got what sounded like the motor wasn't spinning up with quick changes. So I thought that must be it on this battery for the day. When I landed I took a voltage check on the bat without load at 15.1Vcd. I later took a forth flight late in the afternoon about 5:00pm when the winds got smoother. But this time I added one of my 2200mah 3cell batteries that I tied to the 4Ah battery. I kept the 4ah battery installed but not hooked up just to provide the needed mass to keep the CG position. In fact with the added 2.2ah battery the CG was moved just a bit more forward on the last flight at about 1.5 cm forward the present marked estimated CG line. It still flies OK with 3 cells and this CG point. It just no longer can fly vertical but can still climb at about 45 degrees. On this flight I did some rolls that I was surprised at the roll speed faster than expected for a big wing and also tried one loop even with the limited power. On the other flights I was able to open up the throttle full and put it into a 45 degree dive for about 20 meters to get more speed without seeing any problems. I don't think top speed with this prop is very fast at maybe about 60 mph top speed in flat and level flight. I will take a real speed reading tomaro with my android phones gps. With the winds today I couldn't really judge the stability. But it didn't even feel as stable as the S3 wing. I should build one more of this size using the TL54 airfoil to see if that makes it more stable. This still has the zagib 12% airfoil. I also failed to test the planed gyro and accelerometer stabalizer on the M2 as I failed to program the passthru switch into my last software modification. We should have at least the gyro stabalizer mode ready to test tomaro on the M2. The acc or level flight mode might be a problem since I don't have a computer in the field to do the acc calibration after I install the board on the plane. With level flight mode working It might be ready to try the FPV mode on it with the fatshark goggles and video transmitter equipment that is planed for this aircraft. As I hope to have the gps with return to home working before FPV but that might be some time before we have that working.