|Apr 20, 2010, 04:29 PM|
CC35 + CC BEC @ 6v
TP 2100 pl
Very happy with this setup, unlimited performance. Setup lives on in my Eflite Extra 480.
|May 04, 2010, 04:05 PM|
Struggling to learn to land mine
I recently bought a receiver-ready MFX, stock, except for greatly enlarged rudder, totally home-built motor mount and rebuilt cowl due to a dead-stick nose-in, and it uses three 4-40 nylon bolts to hold on the landing gear.
4 landings so far on a nice grassy field. First one OK! Next 3 knocked off the landing gear. Last one also broke the prop and tore the underside of the wing covering where the wheel pants rotated up/back and hit the wing.
So far this plane just seems fast, and it does not want to slow down, nor to glide in for an easy landing with some power still on.
When I've flown it in upwind to land, it built up a lot of speed. Then when I tried to pull up elevator to flare (or to fly high-alpha) it immediately climbed.
I've read in this thread a little about flapperons, but not how much throw to use. Also about it landing itself, power-off. I've not dared try that so far.
So far in my limited power-off flying, it lost speed very fast, lost control authority very fast, and acted like it wanted to fall out of the sky unless I gave some down elevator to regain speed.
One thing I've thought of doing is yanking off the cute wheel pants and putting some some tundra tires or similar larger diameter, softer, possibly air-inflated tires to use till I learn how to land it. Removing the broken nylon screws remnants from the inside using forceps is getting old. Sometimes they stick out the bottom, but sometimes not. I've thought of notching them a tiny bit under the head to encourage them to break right there, instead of at the blind nut.
So far this plane strikes me as a go where you point it pattern plane, but not a 3D plane.
Thoughts? / Suggestions?
|May 04, 2010, 04:37 PM|
Jim, doesn't sound like my MFX. Below is my maiden. One thing I noted is how the plane likes slow flight, not a sport plane at all and how slow and floaty the landings are. It was rock solid in the air to.
Sounds to me like your COG is off with all the changes. I believe I set mine right inthe middle of specs for starters. I like a real neutral plane, flip it inverted and I need zero or just light elevator to keep it level. If it noses down when you flip it inverted, to nose heavy.
I lost mine due to a reversed servo(my fault). I almost replaced it but went with a 42" Slick.
|May 04, 2010, 05:33 PM|
Jim - can you tell us what equipment you're using, and what your AUW is? This doesn't sound like my experience either. I land on pavement which I think is a bit easier, and would definitely drop the pants and get bigger wheels for offroading. Slight power on and slight down elevator for approach, and a gentle flare just as it gets to the ground should put you down safely. I've never had that much drama with mine.
|May 04, 2010, 08:42 PM|
Park 480 motor
APC 12x6E prop
Spinner red backplate, but no spinner front piece or SHCS
Spectrum AR6100E Receiver
Grayson Hobby 30 Amp ESC (manual calls for 40 amp!)
Blue servos with no brand or label showing - I did not remove them to look further
Rhino 2250 mAH 3S 25C pack 6.8 oz including Deans Ultra connector
CG is 3 3/4 inches back from the LE, just as the manual says it should be
Empty weight 27.9 oz vs manual says 23-24 oz no battery
AUW 34.7 oz vs manual says 27-29 oz AUW
So mine is 6-8 ounces heavier than the manual says it should be AUW, with about 2 oz of that being the pack I'm using. I have 3 of them, so I would like to continue using them!
The cowling has been rebuilt and re-fibreglassed. A whole new motor mount was built up to replace the shattered original motor mount. The rudder was stretched about an inch with balsa. The fuselage bottom was rebuilt due to being ripped off with the landing gear twice. The wing has some packing tape on it over the two wheel pants-induced tears in the covering. There is some new self-adhesive covering over the bottom of the fuselage where it was rebuilt.
Ring any bells?
|May 04, 2010, 08:56 PM|
IIRC my AUW is around 32 oz, which would equate to a noticeable (although not substantial) difference in stall speed. It does tend to just drop abruptly out of the air when it reaches stall. I've bent the gear a few times from vertical force, but no airframe damage so far.
I think just going to larger wheels and losing the wheel pants will help substantially for grass landing. There's too much there that can get snagged and cause the issues you're having.
I understand where you're coming from on not wanting to replace the batteries, but every ounce you lose directly impacts your stall speed. Maybe you have a friend with a lighter battery that you can try out to see what kind of impact it would have for you.
By the way I have very similar equipment for everything else, so with the exception of battery we should be about the same AUW. I'm using Thunder Power 2100 Prolite V2's (normally I don't spring for the expensive batts, but it just kind of happened with this one).
Also, I tried using flaperons to slow the landing speed, but wasn't happy with the way the airframe handled with them enabled. It seemed like it would be a lot easier to tip stall & crash, so I gave up on it. One member mentioned something like 20-30 degrees of "flaps" that he was using on the MFX. I can't remember how much I was using when I tried it, except that it was less than that. 30 degrees of flaps will slow it down a bunch, but practice with it's behavior up high before using it on a landing run. Also, it will take a good deal of up elevator to compensate.
|May 04, 2010, 10:02 PM|
Thanks Habitforming, for your help!
I have programmed in flapperons and have tried them in flight a little bit without any up elevator cranked in. I had rather small angles, I think 0, 10, and 20 degrees set. I did not notice much in the air, but I'm still getting used to this plane.
Those ProLights are probably an ounce or 2 or even 3 lighter than comparable cheaper LiPos!
I'll dig around in my LiPos and see if I can find something 3S that's lighter. I'm getting something over 10 minute flights now, so I could probably get by with many fewer mAH if I can move it far enough forward to keep the CG where it needs to be.
My MFX flying just now tends towards slower, more tentative, etc., rather than wide open and straight up! But hopefully that will come in not too long. Then I may be better able to cope with the heavier batteries.
The previous owner T3chDad built a foam bomb-drop box with another servo for the release. He filled it with golf balls. Said he did not notice any effect of the extra weight or the extra aero drag at all. Only thing he noticed was the additional drag on the grass during takeoff and landing.
|May 25, 2010, 11:43 PM|
Joined Feb 2009
I've flown my MFX with everything from Rhino/Zippy 2200/2250's all the way down to a Turnigy 1500 and the heavier battery definitely does cause a noticeable increase in stall speed/landing speed. I also fly off of a pretty rough grass runway and I chucked the wheel pants and stock wheels for some larger Dubro foam wheels. Doesn't look as cool, but it definitely rolls a lot better. I also skipped the tail wheel and went for a skid.
Overall I'm quite surprised at how slow the MFX will fly, and landings are usually nice and tame. My other planes are foamy parkflyers and sport glow, so I've seen faster and slower landing speeds. It definitely helps to put in a bit of power on landing to give you a little bit of elevator authority to increase AoA for a bit of a slower landing. Also, make sure you land into the wind if possible, because with as light as the MFX is, a tailwind will really increase landing distance.
Don't give up on it! The MFX really is a fantastic plane, one of the best in it's size IMHO. My dad has a GP SU-31 of about the same size, and it's not nearly as manageable in the air or in landing as the MFX. If you can get the landings figured out it really is a great plane.
|May 26, 2010, 08:17 AM|
I feel it is a good flying plane with no bad habits and landings are easy(take off/land on concrete). Mine is approx. 3 years old and has a Mega 16/15/3 geared 6 to 1 with a 13X6.5 APCE prop on 4S1P 2100 packs. I did lower the landing gear and used larger wheels to give me ground clearance. I also enlarged the rudder about 3/8" along the back after 25 flights and it helped with hovering, also made up smaller wing lets for faster spins.
Flew 6 packs through it last weekend. Just love the straight up acceleration
If I was to fly off grass, I would use larger than stock wheels, with taller landing gear...
|Jul 08, 2010, 09:25 PM|
I am about to recieve a MFX for my birthday
I have skimmed through the thread and it seems that the landing gear is this planes weak spot.
Since landing gear issues are the reason I am looking for a new plane I am hoping to reinforce the gear on this one before disaster strikes.
Does anyone have any ideas on what I should do?
|Jul 08, 2010, 10:32 PM|
Rock Hill, SC
Joined Feb 2009
My observations only - I've only been doing this for a little over a year. The MFX was me and my 11 year olds first "real plane".
We didn't use the stock wheels because our field is grass and it's not a golf course. So we went to bigger wheel. The benefit here in the context of the landing gear is that we couldn't sport the wheel pants. Which means that when we ripped the gear off (pictures) we did not poke holes in the underside of the wing.
When I built this back I used a plywood plate to reconstruct the entire bottom. It was as a recall a 1/16th in model grade plate that went from the firewall oh about 5 inchs down the fuse (probably to about where the covering was ripped off.)
This had the unintended impact of making the circumference of the cowl larger than the cowl was molded to fit. We have to cut the cowl on the underside and add 2 extra screws to make the cowl spread apart to accept the new plate I had installed.
I used a belt sander to put a nice taper in the plate to blend it in to the body of the plane towards the back.
Then I added 2 x 1/16th inch plywood struts that i epoxied from the plate to the main wing tube - these were at about a 45 degree angle to the side of the plane and I notched the end of the strut that mated with the tube. I did this because I figured we would continue to have hard landings so I wanted to transfer that compressive force at impact to the wing tube. I'm no engineer, but the stick structure on the underside especially after we ripped it out looks real light to me. I'm a big boy (they dont call me heavyj for nuthin) so I like 'em beefy.
Now the landing gear bends and after a year of hard flying the wheel are crooked and the motor mount has ripped clear of the firewall a couple times from dumb moves (landing in a tail wind and cartwheeling nose over) - but the landing gear has stayed fast.
Sure... It's over built. But we're flying with the wingtips on, and we've changed to metal gear servers, and we're flying 450 watts on a 10x5 wooden prop. We beat this thing up. The crazy stuff the 11yo is doing now in the air i'm expecting that one day it will just come down in small little pieces.
Which is why we upgraded to an aeroworks .90-1.2 yak..
For me, if you know you're getting the MFX and you are thinking about somehow strengthening it - frankly I won't fool with it until you broke it. One thing you could try to do it go to nylon bolts to mount the landing gear with the theory being that the nylon bolts would snap before the gear was ripped clean. Heck I think it's so weak under there you might need to score the bolts to make sure they fail like you want on a rought landing. I might do that - maybe. But I wouldn't unnecessarily hack on a perfectly functional MFX until after I torn it up.
But thats just me... Because I'm lazy like that...
My rational is that knowing this weakness in the gear forces you to think and fly carefully at landing. It needs to be flown in not plopped down. Well - your MFX needs to be flow in. Mine i can plop in now... *grin*
|Jul 08, 2010, 10:49 PM|
I think I'll just try extra smooth landings.
Another question though,
Do you notice a difference in flight characteristics with the side-force generators on?
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