I guess it comes as no surprise when given the choice to start a new Mig versus getting my FRC F15 completed that I chose the Mig... :)
But there is a method to my madness... :/ I got a little crazy with the ruler, calculator and pencil over the weekend and modified the RCP Mig29 V4 plans considerably. I didn't take any pictures of the mods that I made in relation to the plans as I want to make sure this thing flies before I release my modification pictures to the world... :) But I did keep templates of the main modifications I made using 3mm depron, so if they work, it won't be hard to lay them on another set of plans and produce modified plans.
As mentioned in this post http://migsrus.blogspot.ca/2014/10/morphing-rcp-mig29-v4-into-mig35_18.html Stephan and I have been discussing ways to shorten the Mig29 V4 and I have been fascinated with modifying it to look more like a Mig35. To avoid confusion, I will call it the Mig29 V4 NAMCV3 just so I can keep track of the progression of modifications I have made with all the Mig29 V4s I have built. Here is a plan form top/front and side view of the Mig35 for reference.
This meant adding a tiny bit to the wings on the tips and at the root to fashion a more "Mig35ish" wing for starters and then shortening the back of the plane by an inch to give it the appearance of the tail section being much closer to the back of the wing.
In the picture above, this is how the tail plate will be in relation to the wing. I also moved the motor mount forward by 1" and shortened the fuselage at the back so that it meets up properly with the front of the prop slot.
I hand drew the round corners on the elevons and incorporated the little "dog tooth" right where the hinge line will be. I may actually trim a bit more off the elevons at the tips, but after sanding they will look and be a bit smaller, so maybe not. They are a tiny bit wider in chord than the NAMCV1/V2 elevons, but a little more has been cut out around the "nozzles", so a minimal gain in size.
Because I had to move so many things forward, I will probably have to put my main wing spar across the two slots where the inner part of the nacelle tabs in (where the red pencil is pointing to in the picture). But no worries, I will just cut a notch in the tab so that it will fit in the slot around the spar.
In order to keep as much room as possible in the electronics bay, I cut 1" off the back of the nose/canopy former and moved all slots forward accordingly
Although you wouldn't be able to tell without the original for reference, 1" has been removed from the back of this piece and the top nose/hatch piece to accommodate the motor being 1" further forward.
The length of the side fuselage/nacelle is significantly reduced. I moved the back edge of the intake forward 2", this accommodates moving the motor forward and the 1 inch reduction in the side fuselage piece between the back of the intake and the front of the vertical stabilizer. The vertical stabilizer/rudders are the same size and shape as they are on the Mig 29 V4 NAMCV2
Without a doubt this is the most ambitious round of modifications I have made on a park jet, so I am excited to see what happens. The whole risk/reward thing is playing a big part here as I'm not sure what is going to happen, but am willing to take the risk.
I will build it to be sturdy enough to handle the NTM 2700 motor, but I think for the maiden and the first few flights I might fly it with the Focal Price motor just so it will be a little lighter and a bit more docile til I get CG, etc figured out. I will maiden with the stock CG and go from there.
I still have to do a little measuring and figuring on the KF airfoils, I will go with KF4s as per usual. They will still be 1/4" longer at the tip to get roughly 40% of chord like on the NAMCV2, but with the slight extension (about 1/2") along the trailing edge of the wing to get that Mig35 look, I think that they might be more in the neighborhood of an additional 3/8" to 7/16" wider than stock at the wing root to keep 40% along the chord.
I was pleasantly surprised that will all the hacking and slashing, I reduced the weight in raw foam (not including KFs) over the stock Mig by 24 grams/0.85 oz... :), so that is a good start since I will be adding a few more pieces of carbon fibre over my previous builds and will be using metal gear servos on the elevons.
Weather forecast still looking bad for a few days, so I hope to get much of this build done in the next few days. I probably won't paint right away til I get a chance to maiden and dial it in a bit. I'm thinking of an interesting "camo" pattern of my own color selection...more to follow on that.
Cheers,
Scott
Scott,
ReplyDeleteI am truly suffering from lackofrcapenia and am living vicariously through you. Just got back from a wonderful meeting/vacation and am paying for it dearly at work.
I have following along and as always, very impressed with the comparisons and calculations. I am very excited about this new build for several reasons.
A favorite Moranism to my students is, "doesn't matter what you know, just how good you look doing it." I really like the top down profile of the Mig-35 with the more closely coupled tail and wing trailing edge shape.
I think you are going to solve one of the aerodynamic disadvantages of the horizontal stabilizer modification on the V4. While the stabilizer greatly improved the overall flight characteristics of the V4, the V4 was not as agile in acute violent pitch changes as the V3. The V3 with it the fully moveable elevon was very susceptible to TVAW Twerking (Thrust Vectoring Ass Wagging). But I'll never go back to fully moveable ailerons, the feel of the V4 is so much better.
However, as always, there is room for improvement. So, how can we improve the "pitchyness" or technically stated, pitch rotation about the center of gravity. I believe you have solved the problem! Chapeau bas to you! Moving the engine forward will decrease the polar moment and make it more sensitive to pitch movements. Centralized mass is always desirable. Secondly, shortening the tail plate and bringing the wing trailing edge and horizontal plate closer will also tighten the axis of rotation.
So many changes in one plane! I can't wait to read your flight reports examining the individual/combination change and how they affect the flight characteristics.
BTW, thanks for finding us new motors!
Fabulous documentation of NAMC Mig Skunkworks Projects!
Back to the grind,
Stephan
Hi Stephan -
DeleteWelcome home and thanks as always for your support and kind words... :)
I feel your pain about getting back to work, I remember the days, away on leave or TDY for a week or two, everyone just kept putting stuff on my desk..."oh he'll be back in a week, it can wait til then". Then you get home, brain is in screen saver mode and all of sudden you need to run 6 brain programs at once while hoping the boss doesn't rip your head off because all the projects people put off on you are due today! Amazing how quickly the relaxing aspects of leave were obliterated in the first morning back to work!
Yes, I am very excited about this project, the last couple have been minor improvements on a theme and although excellent modifications, I figured it was time to throw fear and common sense to the wind and really take it up a notch again.
I agree wholeheartedly with all your comments, I have also noticed that when I have a plane with most of the weight centred close to CG it performs better in all axes, roll and yaw as well as the concentration of weight is such a good rotation point no matter what. I am really interested to see how much more aggressive it becomes aerobatically compared to the other versions.
By moving the motor forward as well, it keeps the distance between the elevons and the motor about the same, I didn't want it to be too "short coupled" from a thrust vectoring standpoint. The FRC Su35 can be that way sometimes and can get a bit too aggressive in the pitch. I think with the right expos and throws it will still have great thrust vectoring from the great design you came up with for the elevons and with better weight concentration near CG, it will rotate better naturally rather than relying on thrust vectoring which can lead to thrust vectoring stalls, TVAW, etc.
I will also put my elevon and aileron servos up well forward as well like I did on my NAMCV2.
Not sure how these changes will affect slow flight and high alpha, but honestly I am not too worried about that, I have lots of other Migs to fly if I am in a high alpha mood. I think this NAMCV3 will have that real "muscle car" feel, especially with the NTM motor, kinda like the F22 V3, but without some of the crazy instability that plane could have.
The DX 2700 was a good find for sure, I was very happy to see how it performed at the field yesterday. I will probably order a couple more before they run out of stock too! Seems like this has become a very popular motor over the last 6 months or so... :)
I'll keep the updates coming as the NAMCV3 build moves along... :)
Be well my friend... :)
Cheers,
Scott