Official Freewing 90mm F-4 Phantom II Thread

[dahawk]

Bring throttle trim all the way down .

[RCjetdude]

Is your receiver getting power? Can you tell? Usually there is an LED in the receiver and any satellites that indicate power is present.

[Hooligan]

Yes, there is power to receiver. Could the ESC be belly up?

[RCjetdude]

Did everything work prior to replacing the faulty LED? If so, try unplugging the LED again and see what happens.

[Hooligan]

It ended up to be my receiver that was belly up.

[Hardway]

Glad you were on the bench and not in the air!!! Good job....

[BreakX101]

Can someone confirm the manual the elevator needs up mix with flaps deployed?

[fhhuber]

While its common to use down mix to flaps, that's mostly because people deploy flaps at excess speed and are combating the resulting "balloon"

Flaps can pitch the nose up or down or not at all if deployed as close to stall speed as possible..

Just take it high and experiment with the result, generally starting from the recommended mix (if there is a recommendation)
You should always take a model high and check out its stall characteristics in all configurations after ensuring the CG is correct. (aft CG and a stall can lead to an unrecoverable spin)

[RCjetdude]

Can someone confirm the manual the elevator needs up mix with flaps deployed?

Up is correct.

[Aros]

I don't recall the specific numbers off the top of my head but I did go by the manual's recommended flap/elevator mix (5mm up elevator for 45mm full flap deflection, 3.5mm up elevator for 25mm takeoff flap deflection) for the maiden. I found I needed a few more mm's of up for both flap settings...I think I ended up around 8mm of up for full and 5mm for takeoff...I can check to be sure. The manual recommended mix was okay but It's dead on now.

[dahawk]

Well ? I went ahead and took her to the field to retry with the FMS 90mm 12B outrunner. Fully charged RT 6000mah 60C lipo. Tested on the bench, I only saw about 2200 watts. But the thrust had seemed okay.


Watching the take off roll she seemed somewhat slow but low and behold she rotated scale like.

Gear up, flaps up and then started my left turn . At that point I could immediately tell she was struggling. Sure enough she went into an unrecoverable stall, dipped the left wing and went in.

Found her on her back. No wing or tail damage. although the h-stab appears to be disconnected. The forward fuse section took the brunt of the force and resulting damage. Looks like it's all repairable with some massaging and glue to get airworthy again. Ultimate fix would be to buy a new fuse. Won't be the prettiest but it adds to the patina. LOL

The FMS 90 did not produce enough power, plain and simple. Why though? It should have produced at least as much as the FW 9B stock 90. I believe I even read somewhere that it should produce around 3K watts and over 7#'s of thrust. That's what really sold me on it.

Is it installed correctly? I think so. The aft section is up on the face of the foam opening. Went ahead and ordered the 130 amp FW esc that comes with the stock 6S PNP. Not giving up. I know the power problem is not the 12B FMS 90 combo.

The only other thing I can think of is the esc. Again, it's a no-name 130 amp job I got a year ago from edfhobbies. I recalibrated. No way to check timing. Other than the esc, I'm out of clues as to why she doesn't have enough power.

Back to massaging and gluing.

[Hardway]

:(

[rifleman_btx]

Dang that's a bummer, hope you get her back into shape again

[dahawk]

Piecing her back to health slowly. New esc on the way from MRC. At least I should be able to program it if I have to. High timing I recon

[rifleman_btx]

That will be a good thing for sure

[themudduck]

:Crying: dahawk, that's a sad story, I hope that you can get it fixed up and try again.

That 12-blade EDF just didn't provide enough thrust. Since it seemed to be working correctly, it makes me wonder if different EDF units require different plumbing (as far as the air duct configuration). I mean, the stock duct seems to work fine with the stock fan (either 6S or 8S) - but if you use a different fan with the same diameter, will it necessarily work exactly the same? Or could it be that changes are needed. For example - we know that the outlet needs to be slightly smaller than 90mm to provide a certain amount of back pressure to the fan blades - its got to be just right or the front of the fan won't pull the air in efficiently. Maybe a higher-count fan blade requires a different diameter outlet or additional input area (cheater hole)? I really don't know, I am just proposing ideas. I don't have years of experience with EDFs (just enough to get into trouble) but I'm aware that the ducting has a huge affect on how EDFs perform. I'm sure there is some Squawker who can provide some expert advice.

[dahawk]

Wondering if anyone else had successfully tried a 6S 12b setup or am I the lone wolf?

I can see with the bifuricated ducting, there was a darn good reason Alpha/ FW chose the 9 blade 1750.

The FMS 90 12B is 1900kv so it’s spinning faster and the blades are at a slightly different pitch than FW. Produces about the same watts as the FW but not sure about thrust which is more important .

I have the FW/ Hobbywing 130 amp esc on order. At least I have a programming card. Will set timing to high. Will try that before moving on to Plan B- the stock FW 9B. 1750kv setup.

Meanwhile, back to gluing....

[EDFjetpilot]

Wondering if anyone else had successfully tried a 6S 12b setup or am I the lone wolf?

I can see with the bifuricated ducting, there was a darn good reason Alpha/ FW chose the 9 blade 1750.

The FMS 90 12B is 1900kv so it’s spinning faster and the blades are at a slightly different pitch than FW. Produces about the same watts as the FW but not sure about thrust which is more important .

I have the FW/ Hobbywing 130 amp esc on order. At least I have a programming card. Will set timing to high. Will try that before moving on to Plan B- the stock FW 9B. 1750kv setup.

Meanwhile, back to gluing....

Hawk,

Ensure you check the amp draw once in the plane. That FMS 1900kv has burned up the FW 130A ESC when installed in the FW F-16. It happened to me and several others if you read through the FW F-16 thread on RCG. Several folks solved the problem by installing 150A ESCs. Me, I moved up to the HSD F-16.

In the FW F-16, the FMS 1900kv was drawing 126A peak, nominal 118A. My ESC burned up after 30 flights. So if the amp draw in the F-4 is similar, I'd recommend a higher amp ESC.

And I've learned that watts don't mean a lot with EDF jets...it's all about the thrust.

Good luck,

Sean

[DrDeath]

Can someone confirm the manual the elevator needs up mix with flaps deployed?

It is correct. Most flat bottom wings with a large distance from elevator and straight edges will need to add down elevator as deploying flaps will produce added lift. With the wings leading edge and configuration with the elevator, flap deployment on this plane causes the nose to pitch down. Please do not omit this step. The manual is correct. Jeremy Sholtz has a great little tip for lining up the elevators on this bird. I will see if I can track it down and post. Hope this helps.

[DCORSAIR]

Wondering if anyone else had successfully tried a 6S 12b setup or am I the lone wolf?

I can see with the bifuricated ducting, there was a darn good reason Alpha/ FW chose the 9 blade 1750.

The FMS 90 12B is 1900kv so it’s spinning faster and the blades are at a slightly different pitch than FW. Produces about the same watts as the FW but not sure about thrust which is more important .

I have the FW/ Hobbywing 130 amp esc on order. At least I have a programming card. Will set timing to high. Will try that before moving on to Plan B- the stock FW 9B. 1750kv setup.

Meanwhile, back to gluing....

Nope, your not the lone wolf, mine flies fine with the FW 12 blade 4068-1680kv unit on 6S, flies even faster without the ordnance mounted, I tried that FMS unit in my F-15 and couldn't tell the difference from the stock FW 3748-1550kv, so I didn't even try it in the F-4, but I do know the FW 4068-1680kv has a better sound, to me that is.