Official Freewing 90mm F-4 Phantom II Thread

[Aros]

I will be checking mine after work. I did send this issue to Alpha, Mark and Tom the other day. If this is found to be a definite issue rest assured it will be fixed.

[davecee]

Earlier posts about the elevator linkage had me concerned, so I opened it up for a look. Found everything to be normal. But, I did go ahead and slide some fuel tubing over the connector. There's no way to casually inspect this. This may be the first Airworthiness Directive for our F-4s.

Is that where you're leaving the tubing? It needs to be slid further toward the servo arm to keep the connector from deforming and coming loose of the "L" bend.

[crxmanpat]

I'm working on the chute mod on mine and will z-bend it at the servo arm just for the added security.

[themudduck]

Hey guys, if you are going to stay with the original white plastic keeper, the fuel tubing needs to go around the end of it, to prevent it from opening.

I have been repairing my plane and I reinstalled the elevator pushrod. (...by the way I tested the servo and there's nothing wrong with it.) I replaced the original setup with a DuBro 2-56 ball link. The 2-56 rod is slightly more beefy than the original rod that came with the model, and I installed a Z-bend at the servo arm, thus eliminating the plastic keeper completely. I also added a lock nut on the ball link. Its not going anywhere now. Here's a pic.

[themudduck]

I will be checking mine after work. I did send this issue to Alpha, Mark and Tom the other day. If this is found to be a definite issue rest assured it will be fixed.

Dear Aros, I still just can't imagine how this happened in flight. I feel that the MRC's hardware is really excellent and I trust it. The mounting plate and two bearings are amazing. I don't want to disparage this incredible model.

Like everyone else, I have a suspicion that the "sprung" plastic keeper may have been a result of the impact with the ground - but on the other hand I did apparently lose all elevator control beforehand and I have no idea why. So I installed the Z-bend simply as a precaution. I know that MRC tests these models to destruction before they're released, so I would think that this should have reared its head already. But maybe its because when we install the pushrod, we're working with the model inverted on our workbench and the bend in the rod is facing the wrong way? If the bend isn't exactly 90 degrees it would be under a lot of pressure to pop open.

[Woodcock]

I think a small correctly sized piece of heat shrink tubing would be a better fix. Be careful with the heat, and don't heat it too much, just enough to make it snug. They also offer heat shrink tubing with a sticky back internal lining. Better yet.

Woody

[DCORSAIR]

Guys, yrs ago I had a Yellow Aircraft A-4 that I lost back in the nitro days, it had a Z bend on one end an a clevis on the other. I was doing a high speed pass and pulled up to turn around and all of a sudden it went into a high AOA and stayed there, all I could do was watch it stall and it fell just like a leaf from the sky until it hit the ground. It was the Z bend that caused it, the Z bend was to large and it was able to jam up in the hole in the servo and locked the elevator in the up position, so be careful and make a nice tight Z bend and not a sloppy Z bend, just a heads up from experience. You guys are right about sliding the fuel line all the way up on the wire and clip near the servo horn, been doing that for 30 yrs and never had one come loose.

[barron06]

A Z bend can also open the hole up in the servo arm as it's inserted, introducing slop. This adds to the slop of the servo, but the biggest culprit is the consistently sloppy ball links. Maybe it was just luck of the batch but I have found that the ball links that come with the SU-35 TV system fit perfect. You only have to drill the rod hole out a bit. I could find no other difference in their construction.

I decided to use 2 layers of heat shrink because putting fuel tubing around the retention arm crashes into to servo output shaft (my L-bend is on the innermost servo arm). If cut correctly, the heat shrink is retained by the lip of the retention clip.

The carbon rod prevents any possible flexing.

These last 2 items are probably over-design and not needed, but still...

Also, concerning the tail hook attachment, see what I did facilitate gaining access to this area. Note: the servo plate is only to keep the servo from moving horizontally in the foam pocket.

[Alpha]

Hi all,

Thanks to everyone and especially Mudduck for sharing this info --we feel your pain, brother!

We torture test these models to an extreme, both on paper and in the air. That being said, there are always outliers that can down our birds, and I know it's frustrating especially when the cause isn't 100% clear and repeatable. Accordingly, we take customer reports very seriously and we've looked into this over the past couple days:

We've delivered [literally] tons of models with this design without issues, so I can say the design itself is sound. In the context of the F-4's elevator layout, the components and their mounting plates are aligned with each other to eliminate biased torque that may introduce a twisting force sufficient to pry/deform the clevis to the point of snapping as seen in Mudduck's unfortunate example. Take a clevis and see how much deflection you need to achieve to snap it clean off... then consider the limited achievable angles of deflection possible in its installed position... It's nigh to replicate. I would encourage all of us to ensure the clevis hole allows free rotation around the control rod, and isn't hung up on any burrs or bent/weakened somehow during installation.

For anyone weary of somehow losing this clevis in flight, adding a sleeve of heatshrink is preferable in my opinion to a Z-bend unless you can execute a tight action with minimal slop. We tested a Z-bend on the prototype, along with a double ended ball link setup, but both didn't make the final version for distinct reasons.

If you do opt to add a sleeve of heatshrink, be sure to test the full range of the servo to ensure the heatshrink doesn't obstruct the servo's movement. Stalling the servo against a slipped wad of heatshrink could kill an aircraft, too.

Of course the curious case of the snapped clevis arm is equally puzzling. There's no real way for us or you to reinforce that arm at its elbow, except to replace it with a full metal clevis. For anyone curious, I can rule out a "bad batch" of clevises, since we looked into it and all the clevises of this type on all aircraft produced for the past seven months have been from the same batch. We'd have planes falling out of the sky left and right, but we don't. Just to be sure, we sampled 100 random clevises and they each passed our deflection/breakage tests identically.

Based on all these data and other statistical figured, I can't say any of this "clevis reinforcement" is officially required. But as a modeler, I can understand anyone's desire to add something if you think it's worth the minute to do (as long as it does less harm than good). I've asked Freewing to consider including a sliver of heat shrink on future production runs for users to install after connecting the control linkage, although again I'm weary of the one guy who shrinks it too close to or around the servo arm and potentially introduces more problems.

I hope this information is helpful!

[crxmanpat]

So I crashed my F-4 a couple weekends ago when it tip stalled on me on landing. Totally my fault for not carrying enough energy to touchdown. Replacement fuse will arrive today.

When it went in, it hit straight on the nose. Not very hard, but hard enough to require a new fuse. When I brought it back to the table, the elevator was free moving, indicating something came loose. At first I thought it might have been the same thing as reported here, that the clevis came apart. I finally opened it up last night in prep for the replacement fuse, and found that the ball link had actually popped off, and the control rod was bent.

So, I am going to stick with the current setup, but do what barron did above. CF rod on the control rod, and heat shrink on the clevis arm, making sure the heat shrink does not interfere with the servo movement (good tip Alpha!).

And since I'm in rebuild mode, I'm working on Steve's drag chute mod. Got the short kit from him a couple weeks ago, and boy is the quality top notch!

[dahawk]

Great info on the elevator. Noted.

Pat, good luck on the chute mod. Agree. Steve's short kit is absolutely superb I took a few liberties but.mine is done, works and I am now just waiting for a plane and saving up for Paul's ( Helmsman52) chute. The cheapie vinyl Estes rocket chute I tested for proof of concept is not a good option. Hopefully, I'll be able to nab an Arf+ soon.

[PlaneDoc]

I did the maiden on mine this morning flying off grass. 6s had know trouble getting airborne. 5500 mah battery gave me 3 minutes with the throttle pretty much high until ready to land. Should be able to set 3:30 on the timer with better throttle management. I also modified my elevator control rod. I went with a 4-40 rod since I had plenty in my parts supply.Very happy with the way it looks in the air.:)

[Grady.c]

If you have a 3D printer, here are some:
https://www.thingiverse.com/apmech1/designs

ok thanks

[crxmanpat]

Great info on the elevator. Noted.

Pat, good luck on the chute mod. Agree. Steve's short kit is absolutely superb I took a few liberties but.mine is done, works and I am now just waiting for a plane and saving up for Paul's ( Helmsman52) chute. The cheapie vinyl Estes rocket chute I tested for proof of concept is not a good option. Hopefully, I'll be able to nab an Arf+ soon.

I'm starting with a chute from my LX Mig-29 (it's the one that was supposed go with the pilot ejection system; why in the world would anyone want to do that anyway?), but I am in line to get one from Paul when the yellow ones are available. I will also be installing the emergency release system that Steve came up with, "just in case."

[dahawk]

I didn't do the emergency release but as I was building, became fully aware of its value. Might go back and add it. If for one reason or another , the trigger fires unintentionally, all I can say is : "Katy bar the door ! "

[RCjetdude]

At speed if the chute deployed accidentally I think the shock cord would snap almost immediately but that is just my speculation... and if not it is easy to let go of.

[Mike_Then]

Hi all,

Thanks to everyone and especially Mudduck for sharing this info --we feel your pain, brother!

We torture test these models to an extreme, both on paper and in the air. That being said, there are always outliers that can down our birds, and I know it's frustrating especially when the cause isn't 100% clear and repeatable. Accordingly, we take customer reports very seriously and we've looked into this over the past couple days:

We've delivered [literally] tons of models with this design without issues, so I can say the design itself is sound. In the context of the F-4's elevator layout, the components and their mounting plates are aligned with each other to eliminate biased torque that may introduce a twisting force sufficient to pry/deform the clevis to the point of snapping as seen in Mudduck's unfortunate example. Take a clevis and see how much deflection you need to achieve to snap it clean off... then consider the limited achievable angles of deflection possible in its installed position... It's nigh to replicate. I would encourage all of us to ensure the clevis hole allows free rotation around the control rod, and isn't hung up on any burrs or bent/weakened somehow during installation.

For anyone weary of somehow losing this clevis in flight, adding a sleeve of heatshrink is preferable in my opinion to a Z-bend unless you can execute a tight action with minimal slop. We tested a Z-bend on the prototype, along with a double ended ball link setup, but both didn't make the final version for distinct reasons.

If you do opt to add a sleeve of heatshrink, be sure to test the full range of the servo to ensure the heatshrink doesn't obstruct the servo's movement. Stalling the servo against a slipped wad of heatshrink could kill an aircraft, too.

Of course the curious case of the snapped clevis arm is equally puzzling. There's no real way for us or you to reinforce that arm at its elbow, except to replace it with a full metal clevis. For anyone curious, I can rule out a "bad batch" of clevises, since we looked into it and all the clevises of this type on all aircraft produced for the past seven months have been from the same batch. We'd have planes falling out of the sky left and right, but we don't. Just to be sure, we sampled 100 random clevises and they each passed our deflection/breakage tests identically.

Based on all these data and other statistical figured, I can't say any of this "clevis reinforcement" is officially required. But as a modeler, I can understand anyone's desire to add something if you think it's worth the minute to do (as long as it does less harm than good). I've asked Freewing to consider including a sliver of heat shrink on future production runs for users to install after connecting the control linkage, although again I'm weary of the one guy who shrinks it too close to or around the servo arm and potentially introduces more problems.

I hope this information is helpful!

Thanks Alpha, this is exactly why I keep coming back to you guys over and over and why I recommend MotionRC every chance I get. You guys are awesome.

[barron06]

Hi all,

**OTHER TEXT REMOVED FOR BREVITY**
Based on all these data and other statistical figured, I can't say any of this "clevis reinforcement" is officially required. But as a modeler, I can understand anyone's desire to add something if you think it's worth the minute to do (as long as it does less harm than good). I've asked Freewing to consider including a sliver of heat shrink on future production runs for users to install after connecting the control linkage, although again I'm weary of the one guy who shrinks it too close to or around the servo arm and potentially introduces more problems.

I hope this information is helpful!

Alpha, I figured you guys wring these models out and you mentioning this helps a bunch! For my part, the pic of the heat shrink is now moved back against the clip lip, retained by a dab of kit glue so it doesn't slide forward. The pic shows the heatshrink further up, before I tested it. Thanks for mentioning this.

To everyone, including mudduck, what I do wonder is if a flat stall would render the elevator ineffective, making it look like a link had popped off. Without seeing the conditions, it's hard to say but, in 10-15mph winds, if your setting up to land, your slowing down on downwind leg (tailwind), then the elevator gets "stops working". This or a maybe a high speed stall, induced by a quick jab of E while at take-off speed. Or, maybe even just a sudden change in wind speed.

Just thoughts

[Elbee]

Sirs, Blanketing of the elevator was/is a concern in the 1:1 based on the wing shape, hence the 'anhedral flying stabilator' and therefore would be a concern in the model. How that is accomplished is irrelevant. It can and will happen. Slow speed/high AOA will do this pretty much each time it is attempted. Carry speed in turns and on finals and fly expecting this will happen and chances are it won't. Best, LB

[themudduck]

To everyone, including mudduck, what I do wonder is if a flat stall would render the elevator ineffective, making it look like a link had popped off. Without seeing the conditions, it's hard to say but, in 10-15mph winds, if your setting up to land, your slowing down on downwind leg (tailwind), then the elevator gets "stops working". This or a maybe a high speed stall, induced by a quick jab of E while at take-off speed. Or, maybe even just a sudden change in wind speed.

Just thoughts

I've been playing what happened (with my crash) over and over in my head and it still doesn't make much sense, but it happened very quickly. I had completed a normal turnaround and was flying upwind, straight and level, and the model starting rising by itself.... and I realized that I didn't have elevator control. It wasn't responding to my inputs. I had time to tell my spotter "something is wrong..." - then I throttled back a little and tried to turn towards the field, but before I could even think about what was going on the model just did a "falling leaf" maneuver. Like a snap/stall... but I wasn't flying slowly like I would be doing on final, so it made no sense and caught me off guard.

It went straight down into trees and then pulled out, without hitting anything... so there was a microsecond when I thought I saved it, then it stalled again and went down into high brush (weeds about 6 feet high) all I could see was the bottom side of the model as it went in vertical (not a pleasant sight) - but someone else said that it had flopped again and was mostly level when it went in. The nose cone was crunched and it had some very minor damage to the front part of the fuse which crinkled up the canopy. The only other damage was a bunch of gouges all over the bottom of the plane and the fuel tanks got pulled off. And while it was doing these "maneuvers" I was trying to control it, trying to save it. (You know how you are moving the sticks thinking that you're doing something to save the plane, then you realize later that the model wasn't actually responding at all... that's what it feels like.)

All that happened in about 5 seconds. When I retrieved the plane the elevators were just loose and floppy, which was very surprising. I found out later that the keeper had come off the servo as I showed in my picture. But I really don't know if it was off because of the crash, or because of the flight loads. The pushrod was installed with the bend facing up, with just the plastic keeper. So I just don't know for sure. I mean it could have been because of the crash. But then that doesn't explain why I lost control right before the crash. If I had been coming in slow on final, going downwind, experiencing a downwind stall would make sense but I was cruising straight and level going upwind
when this happened. It was so strange to have the plane "depart controlled flight" by itself that I don't know what to think. Maybe it did slow down and simply stalled, its not impossible, but it didn't feel like that.

I'm just really grateful that my bird is repairable. When I went to retrieve it I expected a pile of foam and I was amazed that it was in one piece with no airframe damage. I'm replacing the cockpit and nose cone but everything else is cosmetic.