I managed to get out and blast a bunch of batteries (12 in total) through my new Su35 (the yellow/tan/brown camo one on the left in the picture below) this morning before I got chased away by rain showers... :( It was FRC Foamies Su35 MK2 day today at the field... :)
I always seem to have to get a "gonk" on the nose every time I fly an FRC Su35/37 within the first few flights..., not the plane, pilot "dumb thumbs"... :/ Anyway, it is easily repairable and like a good prize fighter it has taken it's first hit and I'm sure will continue to fight and fly like a champ... :) So hopefully the "gonking" is out of the way for awhile!
Weather conditions when I first got to the field were dead calm (perfect for a maiden flight) and then as the rain approached, the wind did start to pick up a little, maybe 5-10 mph max, so I did get a chance to assess it's wind stability a little bit versus the V1 (the mostly white one on the right in the picture).
As a quick recap, here are the differences between the two planes
- V1 has the stock full flying elevon, the V2 has the horizontal stabilizer and then smaller moving elevon similar to the RCP Mig29 V4;
- V2 has a better overall sanding job, paint, but biggest difference is all leading and trailing edges are symmetrically shaped and sanded. V1 has symmetrical trailing edges, but leading edges are still "chisel shaped"; and
- slight difference in the nacelles/intakes, but that is mostly to give a little more space between the tip of the prop and the foam, not to impact any portion of the flight envelope.
Right away as soon as it left my hand I could feel the difference that the symmetrically shaped leading and trailing edges make in the smoothness and efficiency of how the plane slipped through the air. With this reduced drag it feels a bit lighter on the controls (something I am still getting used to), handled just a bit more crisply and it glides longer and more stably than the V1. Distance required to land now is increased by about 50% as the plane just glides so smoothly and deceleration after chopping the power is far more gradual, but it also has less tendency to slow down abruptly and stall... :). A very good thing when short final to touchdown in my books.
I think this is also good news for another reason as I think it is an indicator that the plane is far more efficient as it slips through the air, less drag and turbulence, therefore less power required to maintain speed.
Until I get some more time to fully evaluate the performance of the V1 and V2 in more windy conditions, it is tough for me to say if there is any difference in their stability in the wind. Both are actually very stable in the wind, in fact right up there in wind stability with the Mig29 V4 NAMCV2 in my experience.
What I did notice though was that with the fixed horizontal stabilizer and smaller elevons, the V2 flies a bit more scale and really "carves" its way through turns. Not that the V1 is sloppy in turns or anything, but I did notice the V2 was tighter and a bit more precise in turns.
Having said that, it takes a little getting used to as it does carve through the turns more directly and the more input you give it, the harder it carves, it is like it is on rails. So it actually seems that although the ailerons are the same size and the elevons are slightly smaller, the horizontal stabilizer helps the tail "dig in" through the turns and requires a bit less control input to get around the corner.
This now seems to be an interesting constant between two different airframes, this one and the Mig29 V4. When Stephan and I first started modifying the Mig29 V4, reducing the elevon size and the back plate size to reduced EPPE (elevon polar pitch effect or the tendency for the back end to "weather vane" in a cross wind turn), I noticed with the Mig29 V4 NAMCV1 that it really carved tighter through the turns than the stock Mig29 V4 with a "quieter" back end and equal or less control input required for the same turn rate even with smaller ailerons and elevons.
I know this is a very typical setup for most planes real and RC, but RC Powers I think really hit on another winner with the fixed horizontal stabilizer and smaller moving elevon surface on a park jet. I don't think I would ever build another plane without this setup, I just really like the stability and precision it seems to give my planes now that I have tried it on two different airframes.
One thing I will definitely borrow from the Su35 MK2 when I build other planes is how the intakes are designed with a very slight up turn on the bottom surface. It has been awhile since I flew my Su35 as I have been doing so much flying and testing with the Mig29 V4 and I like how when the plane touches down it has less tendency to "dig in" to the grass and slides a bit because of the curved bottom on the intakes/nacelles. Hopefully in the picture below you can see what I mean.
It is interesting how I ended up with the same CG as with the V1 on this plane, it ended up about 1/8" ahead of stock, so very small difference. Since I moved some weight back, my battery is further forward on the V2 than on the V1, so that gives it a bit more scale feel in the pitch. It will still really snap the nose up if need be, but that might also be part of the reason it carves through the turns so well. With the V1, only about 1/4 of my battery weight weight is ahead of CG, with this V2, about half the battery weight is ahead of CG.
So lots of fun getting to fly this little beauty, the "gonk" is easily fixed and now lots of comparison flying to come between this V2 and the V1 Su35 as well as comparison flying between this plane and the Mig29 V4 NAMCV2.
I am always amazed at how such little changes like symmetrical leading edges or a small reduction in elevon size coupled with a horizontal stabilizer make such noticeable differences in how these planes fly and handle. Such a great way to learn and modify how a plane flies to better suit what you are looking for out of your scratch built park jet.
If the video quality is decent enough against the grey sky, I should have some flight video up on You Tube later today. The step by step build video will take a bit longer as I go through and process it.
Cheers,
Scott
REPAIR UPDATE
Nose repair is now complete, it was not anything structural, just cosmetic. And since it is a new plane, I figured a little touch up was in order since it flies great, it might as well look great... :)
For the repair, I just cleaned up the area to get rid of any grass and dirt that I could, I used some scrap 3mm depron I had laying around to kind of mold into the indentation that was left after the nose wrinkled a little bit. RC Foam http://www.rcfoam.com/ is great to deal with, they often throw in little odds and ends of stuff when I order foam, so I had some 3mm depron not doing anything that fit the bill for this job. I have also used paperless dollar store foam for this type of repair and it works well, just more to sand away. I guess it just depends how extensive the repair to decide what foam to use.
I glued the small pieces that I roughly cut to fill the dent with Foam Tac, let that set up for about 20 minutes, then gave it a very light sanding with 220 grit sandpaper. Then a quick coat of paint and it is ready to go, total repair time about 1 hr and 15 minutes, 20 minutes for the Foam Tac to dry and 45 for the paint to dry and it is good as new with almost no weight gain... :)
Can't wait to get her flying again!
Cheers,
Scott
Hi Scott-
ReplyDeleteWinner Winner Chicken Dinner for the newest SU35 ! It sure looks nice in the air and super scale carving its way through the sky. That signature shape and profile of the Sukoi certainly is unmistakable and separates it from all the rest. FRC did a great job capturing it’s essence but the upturned nacelles make me a little bit nervous as a novice park jet pilot and I’ll try to explain why…
When you combine them with the downward curve of that sexy nose it puts the ground clearance much closer to the danger zone on landings for me and I’ve been avoiding it mostly for that reason. It’s not like the Mig is an ocean liner in that department or anything, but when comparing the SU Mk2 against the typical RCP Mig design, it’s substantially less. “Not for Nothing” below is an illustration I made from the plainview drawings to help demonstrate.
“Not for nothing” is an expression I hear former Boston Bruins goon Lynden Byers use on the radio show I listen to here each morning. I think it means something like “What I’m about to say may not mean anything or be accurate but its important to me“ … lol
I hope the link to the drawing works
http://i61.tinypic.com/2wqu3yh.jpg
Talk to you soon,
RT
I just noticed when looking at that side by side comparison drawing from the previous post how different the rudder surface's are. Maybe the the staff here at NAMC finds the FRC design to be more suitable with its right ward angles in the current quest towards 'Knife Edge Nervana'...
ReplyDelete:-)
Hi RT -
DeleteThanks so much for your kind words on my new Su35, it really flies well, can't wait to get out and keep putting it through it's paces.
Interesting side by side comparison of the two planes, thanks for taking the time to do that picture. The bottom of the nose on the Su35 does get a bit dirty sometimes as it will scrape along the ground occasionally after landing. The curved nacelle does help it slide better, but it can rock forward and scrape the bottom of the nose a bit til it stops. When I compare how the two land, the Mig sometimes "digs in" a little hard putting more wear and tear on the nacelles.
I normally land with a fairly shallow flare, say about 10-15 degrees nose up so that part of the back of the lower fuse touches first and then the rest of the plane hopefully gently follows suit. With the curved nacelles, the Su then sort of rocks and slides and yes the nose will sometimes brush the ground. The Mig V4 seems to have deeper intakes than the Mig V3 did, so when that part of the plane touches down, it tends to dig into the ground a bit in my experience. Plane stops quickly, but then puts stress on the nacelles.
So I guess it is a bit of a trade off, dirty nose or wear and tear on the nacelles.
I will give it a try on the next RCP plane I build, it isn't a huge upward curve, but enough to make a difference on landing I think.
Stephan and I have been big fans of the vertical rudder hinge and vertical trailing edge on our planes for awhile now. I wrote this post awhile ago about rudders http://migsrus.blogspot.ca/2014/08/rudders-rudders-and-more-rudders.html In that post is a link to an RC Powers thread that Stephan started on the very subject of vertically hinged rudders. Some interesting arguments there for and against. I did a lot of side by side testing that in my opinion disproves what some folks said in that thread against vertical rudders, but everyone is entitled to their own opinion.
The biggest thing I noticed is that the angled rudder hinges like on the stock Mig induce a lot of roll when doing "rudder centric" maneuvers like stall turns or wingovers. Thus you have to put in quite a bit of opposite aileron to keep the plane from rolling. With the vertical hinges, this tendency is almost completely removed. There will still be occasional rudder roll dependent on pilot skill or aircraft attitude when executing the maneuver, but they give crisp, clean yaw inputs the way that rudders should in our opinion anyway.
Rudders and their design can truly impact how the plane handles in significant ways. The way the rudders are on the Su35 (I used the same style rudders on my Mig29 V4 NAMCV2) are very effective for high alpha and pretty much all other rudder moves but knife edge.
If you look at the pictures of Stephan's beautiful Mig35V2 http://migsrus.blogspot.ca/2014/09/rcp-mig-35v2-namc-ready-for-maiden.html , you can see that his rudder surfaces are large and vertical, but inboard. There is a fixed part of the vertical stabilizer above the rudder that helps with knife edge stability. Through diligent testing, Stephan has determined that if he used the design like on the Su35, he would experience roll tendencies during knife edge, but with the fixed part of the stab at the top, his knife edges were more stable.
Stephan has much more knowledge on how to set up your plane and rudders if you want to chase the "knife edge holy grail"... :)
Thanks again for the kind words, I am about half way through the build video now reviewing it for content and any corrections I need to make. Then I just need to insert title slides and other cosmetic things to help with organization and flow of the video and it should be ready to go.
Cheers,
Scott
RT & Scott,
DeleteGreat summary Scott on design of the rudder. My goal with rudders on the park jets has been to design them so that function like the rudders on all of conventional planes. i.e. a rudder that induces yaw only as much as possible. There will always be some roll associated with rudder input, but I want that the absolute minimum, hence the vertical hinge and straight or taper so there is less surface area at the end.
Additionally, if I am going to learn to use the left stick, I want it to be predictable. These planes fly fine without rudders, but they add a whole new dimension to flight. Rudder stall turns and knife edge are two of the advanced maneuvers requiring rudder. For high alpha, the full length vertical or inboard are very similar. I found that the full length rudders require a more counter aileron input, thus not as desirable for knife edge.
I will continue searching for the "holy grail of (straight line) knife edge nirvana". I am getting closer.
Stephan
This comment has been removed by the author.
DeleteSounds good keep up the good work Stephan!
ReplyDeleteI learned to fly RC with the indoor version of the 32" EPP Leadfeather Yak that is so popular. The only park jet I've built has been the Mig29 V2 (elevons only). Scott has heard my complaints already and knows I hate elevon's only. I always found myself grabbing for the phantom rudder stick that did nothing, and the roll rate was terrible. I did build a Zagnutz 52" wing with elevons only using the components from the Mig but it was really just a test for my #808 key chain camera . I'm looking forward to building the Mig29 V3 with a V4 type horizontal stab modification (rudders activated). I want to try something different and use 3 servos only ie: one piece elevator; one servo centered for two ailerons; and one servo centered for both rudders (or possibly straight linkage aka typical Airflow design). Even though I'll be forfeiting the effects of thrust vectoring in the roll axis as well as the typical mixes everyone likes to use, I think it will be fully functional and nice and light so I'm anxious to see how it fly's.
(fingers crossed)
RT
Hi RT -
DeleteAwhile back I wrote this article about my findings with the RCP V3s (this also applies to the V4s) and the FRC size of airplanes regarding what I have found to be the ideal weight for best overall performance regardless of wind conditions http://migsrus.blogspot.ca/2014/02/rc-powers-v3-size-planes-and-weight.html
As Stephan has mentioned, we normally like to fly with a 2200 battery in our planes which puts our weights between 20-22 oz (with 6 servos and the Focal Price power setup) depending on the plane, how we have built, etc.
After I saw the wing snap on my first F18 V3 because I built it way too heavy (26 oz), was when I first started to become very sensitive to the weights of my planes.
Last summer I did a lot of testing and flying with the F18, Mig29 and F22 V3s and at first I found that 6.4 oz/sq ft was the ideal wing loading between the three of them. This is fine if you know the wing area of the plane, the FRC planes don't publish this anywhere, so I looked for an easier number to keep consistent in building and flying and that was just the weight, no matter the wing loading.
Much of this weight number is not only for scale type flying and feel, but also to give the best all round performance and handling regardless of the wind as I have little control over how that affects my plane, nor do I have any control over how wind conditions change while I am at the field. So being prepared for whatever Mother Nature sends my way makes for a more enjoyable day at the field.
So for about the past year (unless I am building a speed demon with the NTM Prop Drive motor), I have ventured to build my planes so that when I put a 2200 3S battery in them, they will end up in the 20-22 oz category. As close to 20 oz as possible without sacrificing strength and I try not to get over 22 oz as then the nice pop and acceleration I get from the Focal Price motor starts to suffer due to reduced thrust to weight ratio, more on my thoughts on that in this article http://migsrus.blogspot.ca/2014/07/some-thoughts-about-thrust-to-weight.html
Then if I am "feeling my oats" on a dead calm day, I can drop a 1600 Mah battery in my plane, reduce my weight down to about 19 oz and really rip around the field. However, as a gram here and a gram there all add up to oz, it is amazing how much less stable all the planes are in the wind once I started dropping significantly below 20 oz.
So I am certainly not trying to sway you from what your build plan is to this point, just passing along my thoughts that considering what conditions you might fly in the most can have a big impact on where your overall weight, power and control setup end up in my experience.
When I flew my Mig29 V3 with the German flag inspired paint scheme, at about 18.5 oz it was super fast, nimble and aerobatic, but as soon as a bit of a breeze came up, even a plane as stable as the Mig29 V3 became a real handful at that weight. Drop in a 2200 battery, bring the weight up to about 20 oz and it smoothed out considerably, much more stable and much better wind penetration and I could keep flying without scaring myself half to death... :/
Anyway, just some food for thought depending on what sort of conditions you fly in the most. Mother Nature can be a tough flying partner, but there are ways to help yourself and your plane out if you might fly in windier conditions.
Good luck with the build, how is it coming along?
Cheers,
Scott
RT,
ReplyDeleteLess is not always better and neither is more. For Scott and I, we like the wing load of the 2200 battery over the 1600. Take in to consideration we both build pretty light. If you are going with 3 servos for weight, I think the benefit of 6 servos "out weighs" 3 servos. Scott and shown over 1000 plus flights that plastic gear servos are more than adequate. I use PG servos everywhere but the elevons. I have a stock pile of Hitec 82MGs so I use those on the elevons--overkill.
The only benefit of elevons over elevators is high alpha flight. You may have read my other posts. In summary, I turn ailerons off in high alpha to minimize wing tip stalls. Ailerons in high alpha create a lot on instability.
I also like spoilers and flaps so I go with a dual ailerons setup. As to the rudder, I've fooled around with rudder brakes. Scott and I like the outboard servo setup to keep the prop wash clean and create less turbulence over the rudders and elevons. Probably more academic and reality though.
Thanks for your comments. Look forward to your build and I hope you post the results of mods.
Scott and I are thinkers, builders, and testers. We welcome quantitative results!
Stephan
I suppose I'm still in that indoor foamy state of mind where lighter will always be better. I've only smashed one park jet thus far (Mig29 V2) on 3 separate occasions, so I still have much to learn outside in the elements. Even though I'm leaning towards the lighter set up, its not etched in stone at this point. My limitation's for mixing and saving weight lie’s mainly with my transmitter (DX6i). I've found some useful set up information on the internet, as well as the RCPowers forum. Although below is a great solution for the DX6i from Scott I wouldn't be considering this "Full Boat" type of set up, complete with flap's, vtails, and spoileron's.
ReplyDelete( I converted your photo to this black and white copy, I hope it shows up )
http://i59.tinypic.com/2upg2s3.jpg
I did however order enough goodies so I can still do the standard 4x4 set up he mentions in this thread (post#6) which would work very well with the DX6i, giving the user standard elevons and independent ailerons in case I change my mind before the parts arrive. http://www.rcpowers.com/community/threads/servo-chatter-or-twitching.15449/#post-180860
I'll have to consider what your suggesting regarding the benefit of momentum and better penetration vs AUW in the form of added sevo's, linkage, y-harness's, and on board mixer's... hmmm what a conundrum.
I received the confirmation email from DX today that my happy little Focal Price replacement has begun its long transcontinental voyage to Massachusetts.
talk to you soon,
RT
Hi RT -
DeleteFor the Mig29, you definitely don't need v-tails so that saves you a mixer right there and if high alpha is not that important to you either, then you can save another mixer. The Heads Up RC mixer that I found was the most reliable http://www.headsuphobby.com/V-Tail-Mixers_c116.htm weighs 6 grams/0.2 oz as do the Y harnesses that I use all weigh the same 6 gr/0.2 oz. So if you wanted a 4x4 setup with two Y harnesses and a mixer, you are adding 18 gr/0.6 oz to your plane. Add another Y harness if you decided to go with 2 rudder servos and you are up to 24 gr/0.8 oz of added weight.
Most 9 gram plastic gear (PG) servos actually weigh 11 gr/0.4 oz by the time you put the arm on them and put them in your plane. Most 9 gram metal gear (MG) servos actually weigh 14 gr/0.5 oz. Again, I weighed all of these myself so that I would know exactly what is going in my plane.
The easiest way to adjust your weight in your plane is simply by swapping batteries dependent on the conditions if extra light weight is still of a concern to you. With the Focal Price motor, I use these 1600 Mah batteries which weigh 147gr/5.2 oz https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9456 These are a 30C discharge battery, I wouldn't go much lower than that for C rating. The FP motor (which I assume is the same as the DX motor you are waiting on) can pull up to 36A from recent testing I have been doing at the field, so you don't want to go much lower on the C rating.
The heaviest 2200 battery I use right now is this one https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9942 it weighs 198 gr/6.95 oz. So just by dropping a bigger battery in your plane you can buy yourself a whole bunch more stability. Stephan and I have also found that extending the trailing edge on the KF4 airfoil by 1/4" to make it about a 40% airfoil also helps with wind stability as well as extending the top KF out along the LERX.
This adds stability without much weight, but you still need the weight to help with momentum and wind penetration. Again, I weighed all these batteries myself to know exactly what is going in my plane since I have come to realize the manufacturer's weights are often not correct.
The Turnigy Plush 40A ESC that I use with my FP motor weighs 41 gr/1.45 oz and that is with all connectors soldered on. The FP motor with prop and X mount installed (ie ready to be mounted in the plane) weighs 65 gr/2.3 oz.
So to have the flexibility to be really light on calm days, you might have to have some lighter batteries. I get about a 5 minute flight from a 1600 battery with the FP motor. And for windier conditions, a 2200 battery instantly increases your weight by 1.75 oz but you gain much needed stability in the wind. I get about 6:30 minute flights with a 2200 battery with the FP motor.
Without sounding flippant, it is just basic physics really, the Mig29 V3 is a very stable plane, but in the wind, the lighter it is, the more it is going to get bounced around and the less fun it is to fly. Increase the weight by about 1.75 oz and it immediately gets more stable. Again, staying close to the 20-22 oz range that I mentioned earlier. At least that is what I have found through hundreds and hundreds of flights.
Look forward to hearing about the DX motor, I hope mine should arrive within a week or two and I should also get the one I ordered from ebay as a trial within about a month http://www.ebay.com/itm/321227178111
Hope some of this data helps you in your decisions.
Cheers,
Scott