Update Nov 16 2012:
nothing much to add other than I played a bit with the CG putting it a bit more back with an added penlight battery and my steel rod wing joiners taped to the rear edge in back of the motor. This put the CG just on the line or a bit back by 5mm from the rear cross spar. With this setting I feel I get a better unpowered glide with just a bit less stability seen when I do some radical full over stick rolls. I could try even more rear cg but I didn't have anthing more I could add to push it any farther back. maybe today I will add coins to the wingtips as it has a bigger falcrum it might have a bigger effect. It might also slow the roll rate a bit and maybe add some roll stability so I'll try it today.
Update Nov 14 2012:
some airborn video of the S3 in flight using an 808 keychain video cam #9 from Hobbyking.com That I got secound hand from Gorge. This video is my attempt at chasing a plane to video it in flight. The plane I'm chasing belongs to my buddy we call the mig man (real name Sergay?). Named from when he used to fly real rusian mig jets. I must say that the video isn't very good as I'm still learning what can be done with it.
Udate Nov 15 2012:
The now considered completed plans of the S3 have been released. The dxf drawings and a parts list can be seen at my google docs page at: https://docs.google.com/folder/d/0BwHgFeQZDBYLamNQak1MeVU3bXM/edit
Bellow are the archived Design logs and test results of the S3 started Nov 3 2012:
I've started design work on my new S3 version wing. The S3 will be almost the same as the S2 only it will have a new customized TL54 airfoil 15% thickened. I had originally planed to use a fauvel airfoil but I stumbled onto some cool software called XFLR5 that does polar plots of airfoils and wings that made me change my mind. I had to look at many different airfoils with XFLR5 to make a final decision. I'm sure I will later find or make better airfoils but I have to try something to learn anything. I made a video using XFLR5 of what it looks like as a preview including simulated wind tunnel smoke streaming shots in 3D. See for your self bellow. The goal of the S3 is a test bed of the TL54 airfoil that is planed for use in my FPV aircrafts. If it flys ok I may eather beef it up a bit to enable it to carry the video transmiter and camera or build another like it scaled up in size a bit if needed. At some point I will move successes of the SX (small scale wings) program into my MX (medium scale wings) programs to make the medium scale FPV that will allow bigger batteries for longer flights with added extra equipment including cammera pointing and autonomose flight capabilities. The thickend TL54 airfoil is a high lift wing to provide the ability to fly slower without stall for longer loitering and enable the aircraft to carry more load on the same sized air frame. The thick wing also provides more volume space to fit more equipment inside the wing. The thick wing also makes it stronger and stiffer with little or no spars needed at all in some cases. The first S3 will be built with no spars for testing but may be added in later test flghts with the standard carbon fiber 3mm and 6mm as seen in S2. On the negitive side the S3 I expect should be slower at a top speed of about 60mph at best with the same motor as the S2 that would obtain speeds of 80mph or better with the 2700kv moter and 3 cell lipo batteris. But for a first time FPV pilot like myself I want as slow as possible. I will plan to tune it slower with a 2200kv motor to start as that's what I have in my inventory anyway.
a compared polar plot that compares the TL54_14% with the original S2 airfoil zagi12 seen bellow.
As I'm building I've also collected some information and making small changes that I will add here. One big change is that I changed the airfoil from 14% to 15% thickness. This change was made for a number of reasons one being that the raw foam blocks I get are 2 inches thick so to use as much of the foam as posible 15% was closer. 15% also makes the plane a bit stronger in the Y axis and I noted little change in the polar plot for the 15% thickness in xfoil. Now after wing core cut the unsheeted foam core after all cuts on one wing is only 16.6 grams. This foam I got from friendship market is a bit softer and may be lighter than what I got from the shop on central klong, I'm not sure. Even after tape sheeting each wing is only 36 grams. now with added elivons we are up to 41 grams each with added bamboo spars and junction tape should be a total 110 grams without any electronics or servos. with added electronics 177g motor + speed controler mounts, 214g 3000mah bat. total about 533 grams. so that's just a bit lighter that the S2 with 400 square cm more airfoil surface aria compared to S2 for lifting even more. I've also created some dxf drawing files I made in qcad to try to align the wing tip cuts correctly. I posted present version bellow:
update: Nov 7, 2012
It seems I've hit a snag in the construction of the new S3. That being my source for 7mm carbon fiber tubes is no longer available. This means I will have to try another method for my spar junction on the prototype S3 wing. I just tested a simulated bamboo spar on a 12% thick wing using 12cm X 1.7cm 2mm strips of bamboo on the rear spar and 12 cm X 1.7cm X 1mm on the front spar section. The rear spar is near the CG so will have more of the total load at the spar joint. I tested it with a 6000 gram load for 10 seconds to verify it's functionality that is an estimated 10G load on the aircraft in a high G turn. I put the simulated wing load between two blocks with only .5cm overlap into each of the end tips of the 12cm spar box sections. The bamboo spar parts were 6.1grams and 8.6 grams that compares to about the same mass as the carbon fiber tube that was about 8.5 grams each for 7mm O.D X .5mm wall thickness carbon fiber tubing I was using. The bamboo spars were only held in place and aided with a cap of filament gaffers tape that was 6cm wide on each side of the bamboo spars. No glue was used in the test so hopefully on a temp basis I could assemble and disassemble the wing at the field for transport by adding and removing the gaffers tape on one side to remove or add spars when needed for operation. I continue to look for another source of ether aluminum tube or carbon fiber tube or boxes to make a more permanent fix. This method will at least see if the new airfoil is even worth any more effort and at a cost of almost nothing to try. The bamboo was just something I found at the beach after some rain and is always available if more is needed. Another option is to us the bamboo to make a box to surround a small steel box with carbon fiber tube slide joint. I have some of this steel and carbon material that I got from Tom at the field but I don't know where to get more of it when I run out of what I now have. The other problem with this material is that it's very heavy at .87grams per cm just for the thick carbon fiber tube that is 1.5mm thick by 8mm O.D.. The steel is also heavy at 1gram per cm so with both that is needed for the joint would be 1.8 grams per cm compared to 0.66 grams per cm for bamboo. I also prefer to design and build things that can continue to be built with available materials That also provides methods to know how much it would costs to produce another if desired. The bamboo should provide as much or more strength in the y axis (vertical) than carbon fiber but less in the x axis due to it's more rectangular shape instead of a cylinder shape of the carbon fiber tube. This means I will need the foam all the way across instead of the 3cm gap I had with carbon fiber tube spars that allowed me space to put the electronics and power into. So all the batteries and motor and electronics will have to ride on the top of the wing like I had on the M1 wing. This will add more drag and prevent the sharing of the Velcro mounted power, electronic pod assemblies that I had planed to experiment with different motors and props with quick changes of preambled pods. With the pods I could also experiment on building multiple wings without the need to build or buy more parts to mount motors, batteries and speed controllers. So for this test S3 total hardware material is: 42 baht block foam, 10 baht clear sheet tape, 20 baht balsa elivon stock, 40 baht push rod hardware. Total about 110 baht. The cheapest wing yet. I didn't count the 220 baht each metal geared MG90S servos that I will permanently install in the wing if it works OK.
Update Nov 8 2012:
I updated the drawings to reflect the use of bamboo spars instead of 7mm carbon fiber and added a few details to the drawing. all drawings are in the same picasa gallery location above. Ok the prototype S3 build is now completed at 6:00pm. Too late to test fly it unfortunatly. The total weight with a 2200mah battery is 500 grams. Thats at least 50 grams less than S2 and the S3 has about 20% more airfoil surface. I can't wait to see how much lift it has. I will test it later with about 300 grams extra load to see how that flies if the normal loaded flights go ok. I took a few pictures of the S3 before any flights to see it in it's unblemished state. The pics will be added to picasa as soon as posible.
Update Nov 9 2012 1:00pm:
The first test flight of the S3 prototype wing on Nov 9, 12:10pm went better than expected. I did 3 short flights at the Soi 5 beach lot to see if the S3 would fly at all. All that was needed after the first flight were I had to add up trim until I got a solid tone from my radio. On the ground I just saw that I had used up about 30% of the usable radio up trim so after power off and on the radio that sold tone turned off and I did a second test flight. On the second I got the vertical trim as close as possible at the slow speed that I was flying. The S3 seems to be very stable at the slow speed. The CG seems to be close but I might try a bit more forward as it was a bit touchy in elevator but this present setting might be good enuf. On my last landing I pulled back all the way on elevator at flair and didn't notice any stall problems. I think it has a very smooth stall as I had hoped that I will analyze more later. The lot is very small so I had to do all the tests at minimal speeds. I flew in tight circles around myself until I got dizzy and had to land. I only used 317watts of the 2200mah battery that when I returned took only 22 minuets at 2 amps to recharge. So now it's ready for the stadium field test. There I will be able to do the remaining flight tests of the high speed test , stall recovery, roll rate, long level flight at different speeds, load carrying tests, unpowered glide test and others. I've devised a possible method to carry the wing on my bike that is yet untested for the S3 that includes a foam case insert to prevent damage but leaves 60% of the wing exposed outside the case that might be a problem as the air moving across the wing while the bike is in motion will have as yet unknown effects. The other problem is todays weather. It looks like we have a high chance of rain within the next hour that could last 1 or more hours from what I see on the radar. The new method of transport also is not setup to be easy to keep the electronics in the wing dry so this could be a problem. Hopefully by 2:00pm the weather will be looking better. If not we may have to postpone the next tests.
Update Nov 10 2012:
I had a chance to do some flight tests of the S3 wing today at the stadium field. The bike transport system seems to work perfectly so far with some added bamboo side supports that may not even be needed. I was able to fully trim the wing from the radio without ever having to make any mechanical changes. First test was to try to fly as slow and long as possible. I had a problem with slow due to the new speed controller I got from Tom seems to go from off to 70% throttle when I have a 3 cell battery installed. Most of the slow test I did had to be done in glide with no propeller forces. I was able to get it to altitude with vertical flight with the 2200kv motor and a 6 X 4 prop. I ended up moving the CG a bit back on the 3rd flight by about 1 cm that is just about where the rear spar is located. I see the CG point now by putting my fingers just in front of the rear spar. At this setting I get a very slow stable glide with no power. Before this flight on the second flight I flew the 3000mah 3 cell battery that made the wing a bit more nose heavy and it still flew stable but just didn't have as good a sink rate when I went to slow unpowered glide. I did stall tests that were very good with very easy predictable recovery in all 3 CG positions. When I started higher speed tests things went OK for some time. The difference from the S2 was I was able to do very tight loops even at full throttle with radius of like 5 meters. It reminded me of the tight loops I would do with the talen glider with a fully flouting rear stabilizer. This must be due to the light wing loading and very high lift airfoil. I did some arobatic moves with the role rate I found very good and did some crazy stuf due to the tight roll radius. I later started to see the wing bending at high speed loops and finally I did a very high speed dive and quick pull up that put the wing into a flapping motion much like what I saw with the old 400 powered zagi before we put spars in them. I didn't have enuf altitude to recover so ended up crashing with no damage to anything since most of the speed was lost as the wing flapped. So I tried adding tape to the bottom of the wing to stiffen the wing a bit so I could try one last flight and use the last of my 5 batteries. I was able to get it flying with the last battery but the trim was way off into a right turn and also needed up trim. I finally got the trim set up to fly OK at slow speeds but as I began to increase speed in a flat low tight circle it ended up flapping again. So I ended up landing again without any bad damage to any gear or wing surfaces. So from this it would appear I will need to add another wing spar in the same location as the S2. I had hoped that the 15% thick airfoil would make this unneeded but with this soft foam it seems that's not the case. I will try another bamboo 1.5cm wide by 2mm across each wing at 30% from wing tip. This should add the needed stiffness to provide stable flight up to at least medium speeds. This will add about 70 grams weight or a bit more to the total wings weight. I really need a slower motor or a better working speed controller to do more slow controlled speed test at low altitude so I can see how it acts at different attack angles. The 2 cell battery worked better with this motor prop combo with more control at slow speeds but I only have one 2 cell battery to test with. I think there is a good chance with a few small changes that the S3 wing will be fine for my first FPV aircraft. I think 2 more days of fine tuning and we will have it working to my specs. I still didn't get to do slow flying load testing yet eather as that would require a working ESC also. I think another option to make the wing slower with the present ESC and probly give better battery longevity would be to install a 1600kv - 1100kv or smaller motor with a slower prop. This would also prevent me from pushing the S3 wing to air speeds that this aircraft can't handle at present. This plane is not designed for speed so why push it.
Update Nov 11 2012:
This morning I added bamboo spars to the top of the S3 wing that are 9mm X 2mm embedded 6cm back from the leading edge. I am adding this change to the qcad drawings as a needed change and will publish the changes to picasa when completed. I hope to test the changes this afternoon at the stadium field. I will also bring my only other 40A ESC speed controler with me to try that as well. I had considered also extending the lower rear spar out to 22cm to each side but after the first spar was added it already feels stif enuf to at least try first. I weighed the wing now without the motor battery pod installed but including the servos and we are now at 187 grams. I'm not sure how that's possible as I thought the bamboo I added was about 200 grams alone. I measured a 19cm leftover spar part and it's 3.1 grams so they might be about .16 grams per centermeter. I added 96cm of the bamboo spar material to the wing and a bit more tape so it should be at least 16.36 grams heavier. If I had known the bamboo was this light I would have added more. Last I measured S3 with a 2200mah battery and I now get 521 grams total. Still 30 grams less than S2. Oh and I found the secreet to this new yellow 30A speed controler I got from Tom. It works fine if I power up the speed controler AFTER I power up the transmiter radio. That must be why I didn't have this problem on my first flights at Soi 5. I must have accedently powered it up correctly that day.
Update Nov 12 2012:
The S3 tests flights today were beyond my imagination. I flew a total of 6 batteries all but one flight was perfect. On my third flight I was about to land when suddenly I totally lost control and no mater what I did the wing took a dive of about 45 degrees. The lucky thing is it wasn't far from the field and that it ended up on the edge of some 4 foot soft grass with no damage at all. The problem was that the right control push rod broke loose on the elivon side of the push rod. This was due to I just had it press fit with no glue as it had no threads it finally came apart after about 10 or more flights. Thanks to Gorge who provided me some CA glue to fix the problem I was soon back in the air to continue my test flights. I did some very high flights where I just let go the controls and let the wing fly itself. I was able to not touch it for about 30 seconds with no problem. The wing would just go into a wide slow tern. I did this test with no power on the prop. The only reason I couldn't go longer than 30 seconds is that after each circle the wing made it would drift more down wind until it was getting so far that I couldn't see it well so I would finely touch the controls to at least get it to start to return. I also did very tight high speed turns and some high speed dives to test if the wing flapping was corrected. No mater what I did I couldn't get the flap or any other oscillation to happen. Full throttle loops with full up elevator to make 40 foot radius loops about 6 or more in a row no problem. So lucky I didn't put the heavier bamboo spars I had made into it. It seems it didn't need it. So the only test that I wish I would have tried is a heavy load test with 200 grams or a bit more additional mass. I plan to test with two 2200mah batteries on board to see how it will fly with that. As a 2200mah battery is about 180 grams so that's a good test. If that goes well I might try another 100 grams on top of that for a total of 280 grams. As that would mean I could carry 4400 mah battery power plus a video transmitter and cam with added pointing control for the camera. I was already able to crews at very low speed for at least 15 minuets without one of my 2200mah batteries going dead. So with 4400mah ( two 2200mah bats) I should have no problem with a 30 minuet or longer loiter flight. Should we push for 60 minuets? Seems 10 minuets is all I should need as 10 minuets is the maximum time you can publish a video on youtube.com and the video transmitter and my r/c remote will only fly out 1.5km max so until I get more powerful transmitters on both r/c and video there isn't much need to get a longer loiter flight now is there? Oh maybe to video a parade or something you might want a long flight even in a small area who knows? I had never expected this size wing to be able to do all of these things but I will push it as far as it will go. I also got offered a new key chain video cam from Gorge today for 500 baht. So with that I will be able to publish some of the flights of the S3 before I'm able to get some of the other video equipment (FPV video transmitter and goggles) I have ordered from hobbyking.com . With the video key chain I will also measure the top level flight air speed that I think is around 50 mph max. But I think the high speed dive tests I put it in were around 60mph or a bit more. With the key chain cam we might find out for sure. I could also try putting my 120 gram android cell phone into the S3 that also has a gps and accelerometers to measure some stuff like top speed and max G forces. But I'm not sure I want to risk that quite yet. Ok tomarro the load tests and hopefully a new video so just wait and see.
Update Nov 13 2012:
good news is I got the new video recorder from Gorge today. Bad news is the videos I took suck mostly due to the angle I pointed the cam at 45 degress down so I didn't publish any of them yet. On the good side all my flights went ok and I was able to get a speed measurment with my android phone and new video cam onboard. The max speed I got was 58 mph and this was all tested at level flight with no dives from altitude. That was using a 2200mah battery and the added drag and weight of 120 grams of my android phone plus another 15 grams for the new video camera. Tomaro I'll take some video with different angles of view including looking at the elivons in a high speed dive to see if I see any elivon fluter. I also hope to capture some videos of me chasing other planes in flight. It will be difficult to see other planes in flight as this new camera only has a 22 degree field of view. Another problem with the cam is that it's droping frames so the audio will be out of sync. So max load test today was 665 grams with no noticeable instability detected.
Update Nov 14 2012:
I added one of the two video's I published today at the top of this article so as people might see it long before they read all the entries I made in the S3 logs. I actualy took 5 videos from 4 different camera positions. I took pointing back, sideways from the wing tip and side ways from the center, and two pointing forward from ontop the battery. The front pointing shots looked best to me so that's why I posted them. With the added cam on cirtain locations added a bit of instability but was able to fly with just some added care. the cam on the wing tip wss probly the worst making it scarry to try to fly very slow as the left wing with the cam would stall and drop first. so when the vid tranmiter is added I should add a counter weight or maybe mount the battery that powers it on the oposite side of the wing. From looking at the video's looking at the elivons I can't see any fluter seen at even the fastest powered dive. So I guess that's not a problem with this version of my planes. I also met Nick today with his quad FPV. he tells me he has some fatshark googgles on order that should arive in about 7 more days. So I plan to postpone my purchase of the fatshark gear that was planed for this aircraft until I see how his works first. I'll add the other video I published here today. it's not that good but it displays the S3 doing some arobatics and also slow flight. Also seen in this video is Nick behind me as I fly the S3 when I did a fly by.
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