Official Freewing 90mm F-4 Phantom II Thread

[Coconut]

Beginning of you guys descriptions, sound like I'm getting ready to read an erotic book .

[Hugh Wiedman]

Got out yesterday for a few flights with the F-4. I've been flying it on a 814 gr SMC 6200 with flight time just under 4 minutes but finally grew some cajones and put the 903 gr SMC 8100's in to see how it performs. With the 12 blade inrunner fan in it, I'm not really sure that I noticed much, if any, loss of performance. Maybe an extra 10 feet of take-off run to get off the grass and certainly no degradation of vertical or maneuverability. But definitely noticed aa nice increase in flight time to 5:20. Whoopi!! From now on, that's my set-up and both F-4's are going to be fighting with my F-16 for priority on those batteries. Only have 4 of them so may have to bite the bullet and get a couple more!




So this looks like a low strafing run over some rice paddies during the war! Maybe not, especially with the electric lines in back.

[Ks.jetflyer]

I put the 9 blade 1900kv inrunner in my F-4. Wasn't impressed with performance or sound so decided to experiment a little. I took the 9 blade off and put a 12 blade on. Charged up a 5000mah 65c batt, hooked up my watt meter. Initial amp draw was131.5, after about 5 second it was 126 amp. Didn't pay any attention to watts or volts, was mainly concerned about amp draw. Static thrust felt a lot better than the 9 blade, sound was awesome. Any thoughts or input about this setup would be appreciated.

[Hugh Wiedman]

I put the 9 blade 1900kv inrunner in my F-4. Wasn't impressed with performance or sound so decided to experiment a little. I took the 9 blade off and put a 12 blade on. Charged up a 5000mah 65c batt, hooked up my watt meter. Initial amp draw was131.5, after about 5 second it was 126 amp. Didn't pay any attention to watts or volts, was mainly concerned about amp draw. Static thrust felt a lot better than the 9 blade, sound was awesome. Any thoughts or input about this setup would be appreciated.

Interesting, wasn't sure you could do that, but don't know why not. I will say that the 12 blade 1835 Kv inrunner on a fully charged 6200 SMC draws 129 Ah and 3210 Watts initially. As the battery is drained down, the Ah draw will also be reduced, so you're in the same ballpark anyway. I've put the 12 blade in 6 of my jets so I don't really have a good assessment of the 9 blade 1900Kv fan but would love to hear from someone who has experience with both as well. Clearly the motor diameter (and weight and maybe windings) are different by a good 3-4 mm so what's the advantages of one vs the other (other than the obvious difference in cost). I will say all my jets with the 12 blade fan get off the grass in what I feel is a relatively short distance and they seem to handle vertical and any extra weight better than the 1900 kv 9 blade that I stuck in my Stinger 90 (which originally came with a crappy 1750 kv outrunner). Assume it is somewhat similar to a boat prop, where more blades give better start up thrust and power throughout but maybe not as much top end speed?

[rifleman_btx]

I concur on the boat prop theory. As my 9 blade didn't really have the initial push the 12 had, but definitely had more top end speed.

[Ks.jetflyer]

As soon as we get some decent weather, will give it a go. Was concerned I might let the smoke out.

[paulsnapp]

Has anyone used one of the Eagle A3 gyros from Motion RC in this F4 Phantom? If so, what did you find the max gain percents to be? Thanks!

[paulsnapp]

I was watching RC Informers F4 videos where he cautions that the book CG of 190 is wrong and that it should be balanced between 175 and 180. I am curious what you guys have found to be the best CG?

[themudduck]

I was watching RC Informers F4 videos where he cautions that the book CG of 190 is wrong and that it should be balanced between 175 and 180. I am curious what you guys have found to be the best CG?

That is incorrect. Perhaps that video may have been for the E-flite Phantom?? The Freewing Phantom's manual calls for 190 and that works fine, but it is a bit nose heavy. You can go back a little, I am at 200. The nose-heavy configuration is stable but its hard to flare and you'll break the nose-gear pin very easily. Its much easier to land if you move the CG back.

Make sure you replace the elevator pushrod with HD ball-links and make sure the elevator servo is securely mounted. The stock installation will fail.

I am using an AL-3 gyro, the gains are in the middle position and it works extremely well, the model is rock solid like a locomotive going on tracks. The object is to use the smallest amount of gain that you need for stabilization. Too much gain results in twitches and wiggles and flapping especially at high speed. Here's a belly-cam video of my bird. R/C Freewing F-4 Phantom Belly Cam view - YouTube

[Hugh Wiedman]

I second themudduck CG placement, 200 mm is my sweet spot, and for the exact same reasons on landing. I'm also using a gyro (on everything I have) with the Spektrum AR637T RX using gains of 50/55/60 flaps up and 80/85/90 (Ail/El/Rd) with flaps deployed. May sound a little high, but no oscillations. With that RX, you have the added flexibility to adjust gains in flight with just turning a knob. Also, with enough TX channels, you can adjust each surfaces gain individually in flight. Sweet.

BTW, great looking F4 Marc, and I've always liked your stability camera. 👍

[paulsnapp]

Thanks for the replies. I did check again and it is the Freewing Phantom on the video. The flight video that Motion RC put out shows Ryan explaining how he removed foam from under the canopy to allow the battery to move forward to move the CG more nose heavy than the manual suggests. I guess each plane is a bit different but it is interesting how nose heavy works for some and moving the CG back works for you guys. I am thinking I should stick with the manual of 190 and adjust from there, But, thanks for your replies!

[DCORSAIR]

Thanks for the replies. I did check again and it is the Freewing Phantom on the video. The flight video that Motion RC put out shows Ryan explaining how he removed foam from under the canopy to allow the battery to move forward to move the CG more nose heavy than the manual suggests. I guess each plane is a bit different but it is interesting how nose heavy works for some and moving the CG back works for you guys. I am thinking I should stick with the manual of 190 and adjust from there, But, thanks for your replies!

That's smart, I never go by what others post when it comes to CG, stick with the book CG and yes most of the recommended CG locations are off a bit but at least you won't have to deal with a tail heavy situation if your measurement is off a little bit, there was a guy who just a few days ago, he lost his A-10 from misunderstanding where others are placing their batteries or other recommended CG locations, I would rather break a pin than have one destroyed, I flew my F-4 at the recommended CG many flights and never broke the stock nose gear pin, but I was flying from ashalt so maybe that is why, its best if you measure your own plane at the book CG and decide from there.

[themudduck]

Hugh, Paul, Dcorsair, great comments from everyone! I agree and its absolutely true that your own preference is very important. With so many planes from Motion, I've come to the conclusion that their recommended CG in the manual is always further forward than where it "should" be. Why is that? Well, its very important to the manufacturer that the customer has a good experience the first time - so many pilots are inexperienced and a tail-heavy plane is much harder to fly. So setting up your model a bit nose-heavy is a great recommendation from the manufacturer for starting out. Even for experienced pilots, we need a safe starting point. Once you get used to a plane, you can do some testing and adjust to your own preference. Its very much a matter of your own preference! BTW I really think that a lot of the guys at Motion (and Pilot Ryan) really like nose-heavy planes. At least they are consistent.
Here are couple of thoughts & opinions if you like reading...

Nose-heavy jets tend to fly more stable, like an arrow... which is terrific if you like to go fast and smooth.
Aerobatic planes (scale aerobats and pattern ships) generally perform better when they are balanced neutral. When you fly inverted, they require practically no down elevator. In that condition the model reacts the same regardless of the attitude and they react instantly to the smallest input - they are very sensitive (light on the stick) and usually need some expo. If your plane is not neutral, it will be less sensitive to the controls and will need greater control inputs.
Gliders like a CG that's a little further back especially in dead air, it makes them fly slower and they're more sensitive to thermals. They penetrate better (and become more stable and easier to fly) if you move the CG forward.

A nose-heavy jet will fly great, fast easy and stable - but you'll find that when you are inverted (with no gyro) the model will tend to pitch towards the ground quite heavily, it takes a lot of down-elevator to stay level. However, as discussed here on hundreds of posts with many models, when set up like that they are harder to flare and tend to do the "pogo-stick" bounce when landing, which results in broken nose gears. That problem is worse the further forward the NG is. You can avoid that by landing faster (which is how nose-heavy jets like it) and that's great if you have a long runway but that doesn't work well with shorter runways!

My own preference is for jets to be a little nose-heavy, but in practically all cases my Freewing jets have the CG further back than what the manual says.
I like my aerobatic planes to be neutral - they fly inverted with practically no down elevator required.
My club has a 300-foot runway. I like to try to slow my planes down for landing using flaps and keep the nose up with the jets. I see other pilots who slow down but can't flare, the nose wheel will touch first and bounce the plane into the air. Boing Boing Boing, crunch and I like to avoid that. If you come in hot with a long runway then you won't have that problem. Maybe.

Here is an easy flight test you can do with any plane. Lets say you've already trimmed your plane to fly level. If you pitch your plane up at a 45-degree up angle (wings horizontal) and then invert (fly upside down), you remove just about all of the aerodynamic forces that require whatever aerodynamic trim is in play. If you were in the cockpit you'd feel zero "G". So here's what happens when you fly your model at full power up at a 45-degree angle, then INVERT it and then let go of the stick:
a) it keeps going up at the same 45-degree angle. This means it has a close-to-neutral CG. Perfect for a pattern plane!
b) it noses over towards the ground - this means its slightly nose heavy. Slightly nose-heavy is completely normal - how fast it pitches down indicates how nose-heavy it is. The more nose-heavy your plane is, the more up-elevator trim it has and the more it will pitch down in this test. With my jets, when I do this test they will gently arc towards the ground and with a light touch of down elevator they will stay inverted. If I need a LOT of down elevator to hold it then it means the plane is nose-heavy. How much do you prefer?
c) it pitches further up towards the vertical - this means its tail-heavy. This is usually "not desirable" and can result in instant snap-rolls when you don't want them.

Again, this is a technique you can use to adjust your CG to your own preference so that your plane flies the way you like!

[Coconut]

Does Motion sell upgraded pushrods for the F4? If not where can I get them from? Also, how do you secure the servo? I would really like to get the F4. But, I haven't because everyone say that you have to upgrade the pushrods and secure the servo.

[paulsnapp]

Does Motion sell upgraded pushrods for the F4? If not where can I get them from? Also, how do you secure the servo? I would really like to get the F4. But, I haven't because everyone say that you have to upgrade the pushrods and secure the servo.

I purchased upgraded 4-40 pushrods and heavier ball joint clevis from Motion RC. I also slid a carbon fiber rod over the new pushrod. When I checked my elevator servo it was not even glued in, it was just pressed into the foam cavity. I replaced that servo with an upgraded servo. I also glued in some plywood mounts as well as glue around the cavity before I reinstalled the new servo. Maybe all overkill but several guys on here have suggested it. See PIC. You will also see a couple more servos added and a hinge on the tail cone. This is the drogue chute mod that I found here online.

[locharrow]

"I would really like to get the F4. But, I haven't because everyone say that you have to upgrade the pushrods and secure the servo."
Get one ............Put a close fitting carbon tube over the pushrod (I use a bit of old fishing rod tip ) to stiffen it and a wedge of Gorilla Glue round the servo. Survived several mishaps with this fix in mine and it is still good after three years.

[Coconut]

Where you guys get the carbon fiber from? Locharrow, you use old fishing rod as the carbon fiber tube? I'm actually waiting on the T45 to come back in stock, but I do want that F4.

[locharrow]

T45 is a Bea Hawk in disguise....had the 80mm FMS Hawk and it was great fun but does not compare to the F4.......very different animals...Any kind of hard close fitting hard tube will do the job. I only used an old fly rod tip because being a long time fly fisher I have loads of old rods......used another piece of rod to replace a fractured wing tube on the F4.

[GliderGuy]

Hi Coconut and Paulsnapp,

I highly suggest you search on the words ferrite, RF choke and read/learn about them. I lost an F-4 and an A-10 due to likely radio noise generated by the high-current ESCs on these birds. You can get the chokes on Amazon. It has been demonstrated with actual measurements that frame loss and holds are reduced (as recorded by a transmitter) with the RF chokes.

Flying high-current ESC birds without chokes is risky, in my opinion. The various posts will teach you where to install them...research these forums, read, and learn. Amazon has several sources...one example follows:

https://www.amazon.com/Taigoehua-Sup...NsaWNrPXRydWU=


-GG

[paulsnapp]

Where you guys get the carbon fiber from? Locharrow, you use old fishing rod as the carbon fiber tube? I'm actually waiting on the T45 to come back in stock, but I do want that F4.

I ordered my carbon fiber rods from Amazon.