If you have been following this blog for a little while, you know that Stephan and I have been busy this summer building, modding, flying and testing the wings off our Mig29 V4s in stock and modified variants.
Here is a picture of my three Mig29 V4s... :)
Since I'm retired and a bit of a "park jet bum", I have managed to rack up 437 total flights between all three of these planes over the summer and early fall. I don't mention this number to brag or impress, but rather hope it will lend a little credibility to what I have discovered about the center of gravity (CG) of this plane in all the variants I have built and flown. I know the details of the CG of all my Mig29 V4s is scattered around the blog, but I wanted to consolidate my findings in one post to be of the most use for anyone considering this plane as a future build.
I guess you could say I am a bit anal/OCD when it comes to getting the CG dialed in just right with my planes, I just find the extra attention to detail and taking the time to get them dialed in makes a huge difference in the long run for how my planes fly and handle. I wrote this post on how I like to dial in my planes...it is a bit detailed, but this process has certainly helped me over several different planes http://migsrus.blogspot.ca/2014/07/some-thoughts-about-dialing-in-plane.html
Essentially, I try to get the plane balanced with zero trim in all axes if I can so that when I take my hands off the controls it will stay straight and level on it's own without climbing, descending, rolling or yawing.
On all three variants of this plane I have built, I have found that the CG has ended up forward of the stock CG (the one that is marked on the RC Powers plans, available for purchase at http://www.rcpowers.com/community/pages/home/ ) I have flown all three variants of this plane in pretty much every possible wind condition from dead calm to 15+ mph winds, so I'm very confident I have all three of them dialed in properly for all flight conditions.
Here is what I have found with each plane individually. I won't discuss the complete details of the mods I made on the NAMCV1 and NAMCV2 planes other than those that might impact where the CG ended up. If you have more questions on these, you can read through the blog or post a question anywhere on the blog and we will try to help out.
All the variants have the same power setup, same number of servos and control setup other than different size or shaped control surfaces. All have KF4 airfoils, although the modded variants have slighter different size KFs.
Stock Mig29 V4
The stock build Mig29 V4 is the tan/grey/green camo plane in the middle of the picture above. I now have 221 flights on this plane. It is the heaviest of the three, now weighing 21.8 oz/618 gr with a 2200 battery. It has gained a little "repair weight" after a few "gonks" here and there, but still flies amazing.
My CG on this plane where it flies the best in all flight envelopes is 5/8" ahead of the stock CG, this is with no trim in the pitch. It is the only plane of the three where to keep it level in the roll, I have my battery all the way to the right side of the electronics bay and still need two clicks of right trim. Because of how I built it with my servos spread along the airframe, my 2200 battery is about 1/2" from the bulkhead, so if I want to fly it with a lighter battery like a 1600, I have to put in some down trim to keep the nose down.
Mig29 V4 NAMCV1
The NAMCV1 is the mostly blue Mig on the right in the picture above. I now have 136 flights on this plane. This was the first modified variant I built of the Mig29 V4. It is a little lighter than the stock Mig29 at 21.5 oz/609 gr with a 2200 battery. For comparison purposes with the stock Mig29 V4, I put all the servos, the ESC and Rx in the same spot to have the same weight distribution to reduce the number of variables in evaluating the handling and performance differences.
As part of the modifications Stephan and I discussed and decided upon, I extended the KF airfoil back about 1/4" to make it approximately 40% of the wing chord. We have found this to work very well on Migs we have modified in the past, so kept it as part of the winning combination. I understand that this small increase in KF chord would probably impact the center of lift (CL) and CG, the CG on this plane is 1" ahead of stock now. This requires that I fly with my 2200 battery directly against the bulkhead to maintain proper balance with no trim in the pitch.
I cannot fly this plane with a 1600 battery without inputting down trim in the pitch to keep the nose down. It flies amazingly well, but I don't really have the flexibility to fly it with a lighter battery without inducing more drag by adding trim in the pitch.
Mig29 V4 NAMCV2
The NAMCV2 is the blue camo plane on the left in the picture above. I now have 80 flights on this plane. This is the lightest of my 3 builds as I really focused on trying to keep it light. It weighs 20.8 oz/590 grams with a 2200 battery. After having seen what was happening with the CG on the first two Migs I built, I purposely shifted some weight forward in my build, moving my elevon and aileron servos and my Rx 1 and 3/4" further forward than my other two Migs. This variant also has the extended KF like the NAMCV1.
On this plane, the CG is 5/8" ahead of stock to have it balance in the pitch with no trim. Thankfully because I planned for it in the build and moved weight forward, I do have the option of flying this one with a lighter 1600 battery, it goes all the way up against the bulkhead still, but no down trim is required to keep it balanced.
So I am not sure if things just happened this way for me, but to have the same trend with the CG on three planes, I tend to think it is not a coincidence.
My power system is not that much heavier than what RC Powers recommends on their master parts list http://www.rcpowers.com/community/threads/master-parts-list-official.8300/ ., so I don't think that is making it more tail heavy than a plane that might be built with stock recommended setup. From my own data collection, the motor I use, the Focal Price 2700 with a 6x3 EMP prop is actually 2 grams lighter than the Turnigy D2826/6 motor with a 6x4 APC prop. The only real difference is that I use a 40A ESC instead of a 30A ESC which is 7 grams heavier, so when the dust settles, there is only a 5 gram increase in weight in the power system.
Perhaps even with my stock Mig using the full KF4 affects the CG somewhat, when I look at the promotional pictures from RC Powers of the plane they built http://www.rcpowers.com/community/threads/mig-29-v4-%E2%80%9Cspeedmaster%E2%80%9D.16826/, it does not show the top KF extended all the way along the LERX, so I'm not sure if that makes a difference, if the CG was determined without the extended KF along the LERX. When the plans were released, it had the top KF extending forward, I'm not sure if the CG needed to be adjusted, but it could have made a slight difference in why I have found the CG to be ahead of the stock CG. Perhaps that is why, I'm not sure.
Again, perhaps this is just an anomaly, but as I mentioned, to find that happen on all three planes including the stock built Mig29 V4, I tend to think it is a solid trend. After accumulating as many flights as I have and evaluating these planes over such a large body of flying, I am fairly confident in my findings/observations.
So why is it important to mention these findings? Well, I'm not sure what others have been finding or reporting as I don't follow the RC Powers forum any longer, but it might impact how you build your Mig29 V4 depending on what flexibility you want regarding batteries, power system, etc.
As I mentioned in the posts I wrote during the build and post flight of the NAMCV2, I purposely put weight forward as I knew I wanted the flexibility to use lighter batteries without having to add trim or extra weight to get the plane to balance. Perhaps this might not be an issue if you are building simple, no KFs, elevons only or a less complex setup than mine, I'm not sure, but it might be something to keep in mind if you decide to build this plane in any configuration.
Hopefully this is helpful if you are thinking of building an RC Powers Mig29 V4, it is an amazing plane in any configuration, it is without doubt the best stock built plane I have ever flown. The mods discussed throughout our blog were to improve on some things Stephan and I saw to tweak the plane to fly to better suit our flying styles.
Cheers,
Scott
Nice review of the 3 different setups. Isn't the parts list a 1800mah? I'm thinking the weight from 2200mah maybe that is the difference from there stock setup up. I'm looking or was looking at 2200mah batteries to fly on them windy days I seem to crash easier on the windy days with my 1800mah batteries. Either way tried to start building and I just can't do it with a knife in my back cause after 15 minutes that's what it feels like. So I think I'm not going to be building anymore the pain is agonizing. I just made it worse on Friday when I took my boy's swimming. The pool was so slippery with the slick ceramic tile they installed. Fortunately I was able to grab the handrail in time so I didn't fall on my back but the slip and twist on my back did a number on me bed in bed pretty much whole weekend. All the pills I'm told to take don't help even my back brace isn't helping now. So I'm done flying for now and building till I can recover from this back injury. It is depressing not being able to do anything I read about. See what people don't realize is the other 3 fractures are bad enough that I should have had them cemented back together like the two they did in june. But the risk is to great due to my heart is on other side lungs lots more blood vessels etc and death or paralysis. So 6 months to a year I'll be back at it but I'm just going to have to step away til then I feel it's to frustrating I'm looking at maybe buying a 150 dollars pre built BNF planes maybe I just can't endurance the pain to build a plane anymore. I'll Check in on you guys still cause I believe in you two. Great work on mods can't wait to get one built but it's going to have to wait. Maybe after a cortisone shot next month in my spine thinks might get better. Time will tell. Maybe I will get something to fly 9th went Wednesday which will be my 41st birthday lol would be nice. Anyway take care.
ReplyDeleteRob
Hi Rob -
DeleteSo very sorry to hear of your back issues getting worse, will keep a good thought for you and hope that you get back on the mend soon. I can only imagine how frustrating it is, but time and patience I guess will be key on the road to recovery. RC planes will always be here, so focus on getting your body well and it will be that much more enjoyable when you get a chance to come back, I'm sure. That might be a good idea to get an ARF or BNF that you can toss in the air once in awhile just to have some fun. I know flying can be very therapeutic for me, hard to feel stressed out when having that much fun.
Yes, surprisingly the recommended battery is now a 2200, for a long time it was a 1600 which would make it easier for most beginners to have a lighter setup, I'm not sure why they changed it. I prefer to fly my Migs and most of my planes with a 2200 battery because I find that when the weight is around 20-22 oz for these V3 and V4 size planes I get the best overall stability and handling, so I try to build light to allow for that and when I really want to rip around on a calm day, I'll drop a 1600 in my plane for some good speed.
Thanks as always for your kind words and support and as always I'll keep a good thought for you on your way to recovery with your back. Keep your chin up and take care, Rob... :) Happy Birthday!
Cheers,
Scott
Scott,
ReplyDeleteGreat review of the CG differences between the 3 planes. I have found my CG to be in front as well and my planes come in around 22 oz with the 2200 mAh battery.
The 1600 vs 2200 battery is interesting. Rarely do I have a perfectly calm day, so over 90% of my flight time is on the 2200. Honestly, I prefer the feel of the 2200 battery, the extra weight and wing loading makes the plane a lot less twitchy.
My Mig-35v2 is nearing completion and will hopefully maiden by the end of the week. I plan on copying your NAMCv2 camo scheme. No NTM for this one! Just the FP 2700.
Stephan
Hey thanks so much, Stephan... :)
DeleteI am very happy to hear you have the same findings. Again repeatable results solidify our evaluations and assessments... :) Like you, I prefer to fly with the heavier battery and have found the Mig flies very well in the 21-22 oz area.
I played around with weight distribution on the NAMCV2 to see what it would take to have the option of a lighter battery as often in the late fall and winter we get some dead still days which make for some fun to really rip around.
Another upside of having more weight in closer proximity to the CG on the NAMCV2 is aerobatics and turns seem to be just that little bit crisper. I was worried this would possibly effect the balance of the plane for high alpha, but I think with the extra weight concentrated forward it makes the high alpha better in my experience.
I look forward to seeing your Mig35V2, that is a cool paint scheme, I look forward to seeing your excellent interpretation of it. As it starts to get cloudy here in the coming weeks of fall where I am, it will show up even better against the grey sky.
My next "Mig oriented" project will be to modify the NAMCV1 to be able to handle the NTM motor and some 4s fun... :)
Thanks as always for the kind words and if I don't speak to you before, good luck with the maiden of the Mig35V2... :)
Cheers,
Scott
I will tried to post this again for some reason I tried posting a question and I didn't even post it on my f18 version 4 at half throttle and level but when I go full throttle it just wants to climb and I have to push down to make it level out do you think that is because my battery was too far back and not far enough forward or do you think it could have just been the picture of my motor possibly any thoughts would be great.
ReplyDeleteon a positive note I had a note on my door where they had tried to deliver my hobbyking order from the 26th of June finally I can go pick it up tomorrow at the post office. Happy birthday to me finally get my order on my birthday.I hope this will light a fire under me bum. I think I will call my doctor and explain to him how I hurt my back again and its hurting way more and the medicine is not helping maybe he can up my dose so I can do something with my hobby that I love so much. Any thoughts on the battery location would be great whether its the battery location or it's possibly the angle of my motor.
Thanks
Rob
Hi Rob -
DeleteHappy Birthday and glad to hear your goodies from HK finally arrived, I'm sure that is a big relief after such a long, frustrating wait.
In my experience, there can be a few things that cause a plane to "zoom" when full throttle is applied, so while some of things might seem simple, they are worth checking.
First, I would double check the elevons to make sure that when you have zero trim that they are dead centre and not angled that they may be causing the plane to want to climb. I would also do the same with the ailerons to make sure you aren't getting any kind of unwanted spoiler or flap input as you apply more power.
Then I would check the motor to make sure it is not angled up or down at all and is as close to dead center as possible. I have found it doesn't take much, a couple mm off and the plane can climb or descend depending on how the motor is tilted.
With the F18 V4, those leading edge slats might even cause some of the problem, I don't know. The more I flew mine in all honesty, the less I liked it, I am certainly not a fan of those big fixed leading edge slats/fronterons, but just my two cents worth. I am going to be building another F18 after I finish my FRC Su35 and it won't have the fronterons, I am looking at having a morphed plane with stuff from the V3 and V4, just have to sit down with the plans for both planes and work out a plan.
So once you have checked out all the mechanical possibilities, then you could try adjusting your battery forward and see what happens. Normally these planes are a bit flexible with the CG meaning you can move the battery somewhat before you have to adjust your trim. I would just move it in small increments, say about 1/4" at a time, you can test it, land, move it again, and so on all in one flight so that you try to get it dialed in without burning through a whole bunch of batteries.
In all honesty, I have even had to fly some planes just a tiny bit nose heavy to keep them from zooming every time I want to go full throttle. I don't mean nose heavy to the point that if I let go of the stick it is going to nose dive straight into the ground, but just enough to keep the nose level at full throttle.
Another option if moving the battery forward doesn't stop the zooming is to angle the motor down a little bit. This can be a fussy process sometimes, so one I normally only do as a last resort. I have only really had two planes that had zooming problems to where I had to play with motor tilt, the FRC F15 MK1 and one of my RCP F22 V3s. It can be a very tricky process because as I found with my F22, if I got the motor off center in the yaw, when I hit full power it would sometimes not only still zoom, but then it would go left or right depending which way I had the motor pointed, and it doesn't take much... :/
One way to make this adjustable is to loosen the top two motor screws that hold it to the motor mount a little bit and push a toothpick (the old angled kind that is thin on one end and thicker on the other) between the motor and the wooden motor mount. Then if you need more tilt, you can keep pushing it down a little bit more to angle the motor down further. I have used washers also between the motor and the motor mount, but this is less adjustable. If you do get to the point of playing with tilting the motor, make sure you do your full throttle tests up high since it can be very sensitive to change and you don't want your plane suddenly diving at the ground when you hit full throttle and not be able to recover.... :/
Anyway, hope some of these ideas might help you out in figuring out the problem. I hope the doctor can help you out also and you can get back to doing at least even a small amount of this great hobby.
Good luck with your back and your F18... :)
Cheers,
Scott
as you can tell I had done all that voice to text cause I didn't want to sit there and type everything again after it deleted everything so I do apologize picture was supposed to been pitch and a few other words I'm sure you can make sense out of it I hope as you can tell by the run on sentences laugh out loud
ReplyDeleteThanks for the input toothpicks is nice idea just shim it up. I'll also look at slop in controls.
ReplyDeleteWas able to buy eflite umx Pitts BNF but by the time I went to fly was just after sunset and lost orientation and now the motor doesn't act right. Just my luck to end this day on a bad note. And my sister and brother didn't even tell me happy birthday on top of that. So I'm off to bed just want the day to end. Have a good night. Thanks for the input.
Look forward to how your F18 turns out.
Rob
Sure Rob, no problem, if it gets to that point, it is a bit easier to shim the motor a little bit at a time using a toothpick or some other method. That way you also don't have to keep taking the motor off to use washers or things like that.
DeleteSorry to hear about the Pitts situation. Is the motor still turning? Could be maybe just something to check in the connections if it had a bit of a "gonk"? Hopefully the shaft didn't get bent, maybe there is just something rubbing on the nose cone or something? Hope you can get it figured out without too much trouble.
Sorry your birthday didn't turn out how you hoped... :/
Thanks for the wishes on the F18. It will be a bit before I get started on it, I have been doing some measuring and thinking, but I need to get my FRC Su35 finished up first, then on to the F18.
Cheers,
Scott
actually good news apparently when I thought the battery was fully charged at 7.6 volts well not really It should have been at 8.4v so apparently after I lost orientation and nose dived it and I tried checking to see if it worked right it was because the battery was low it was stuttering. I've had about five successful flights on windy days as well and boy does it fly great with the wind it's almost like there's no wind bothering it that stabilisation is sweet and the plane weighs almost as light as a couple pieces of tissue paper it's amazing that the wind doesn't push it around hardly at all. So all is great I can fly this plane while I wait for my back to heal I've got a new lease on my hobby now laugh out loud.
ReplyDeleteThanks
Rob
Hi Rob -
DeleteGlad to hear you got the battery situation sorted out and got some flying done, sounds like a fun little plane to fly.
The whole battery thing can be confusing, batteries are often referred to by the voltage at 85-90% capacity. For example you hear or read people talk about 2S batteries as 7.4V (3.7V per cell) or 3S batteries as 11.1V (again 3.7V per cell). This is the point down to where I run my batteries when I fly, but fully charged, most batteries should be around 4.2V per cell. As the batteries get older, they will not go quite to this, most of my well used batteries charge to 4.18V per cell, but are still fully charged.
Depending on where the voltage cutoff is set on the ESC (I'm not sure if you could adjust it on your new plane), if any of the cells get down close to that voltage cutoff level, you will get that sudden sag in power where you might have 15-20 seconds to get back to the field with just enough power to turn the motor. You should still have enough juice to allow the servos to operate, just not enough to get full power to the motor.
Continued good luck and fun with your plane!
Cheers,
Scott