F-4 Phantom - Twin 70mm EDF Monster!!

[Sotm]

BEHIND the wing TE? Yeah, that is WAAAAY too aft. Something's amiss there...

But yes, I do have an answer: CG range should be 5.38" - 6.76" (15% MAC - 25% MAC) from the wing root LE.

The blue line is the 15% MAC location, and the red line is 25% MAC. I maidened the first one in Ohio and the second one at home both closer to the 15% mark, and they were quite nose heavy. I think it should go back closer to the 25% MAC location.
View attachment 101108

I use this "Flying Wing CG Calculator" to get quick CG and MAC calc's for the wing-alone: http://fwcg.3dzone.dk

Not sure a flying wing COG is correct. went back to my on-line and used the one panel wing instead of the two panel. Got very different result. 8.46 fro LE. The flying wing one of yours gave me 8.11 from LE. Pretty similar but different from your 5.38 to 6.76. I did lengthen the wing 1 1/2 inches on each side though for a total of 3 inches more span/and aft sweep. Could be the difference. Maybe I'll just try my friend's "Drop" test. Hold it level in flight ready condition and drop it. See how it drops, nose down or tail down. LOL Seriously I know a dude that CGs his scratch builds that way.

 

[Mid7night]

Are you calculating including the center panel as a triangle, or a rectangle? Your span difference will give you a different answer, yeah.

Regardless, the drop test is a good one too. Also, make sure the CG is in front of the main gear!

 

[Mid7night]

Here's another CG calculator with more flexibility and detail: https://www.ecalc.ch/cgcalc.php

 

[Sotm]

EDFs

Interesting my 70 mm FMS 12 blade 4S EDFs have a more pointed spinner than yours and no vents or holes on the sides like yours do. Mine are V2s.

 

[Mid7night]

Interesting my 70 mm FMS 12 blade 4S EDFs have a more pointed spinner than yours and no vents or holes on the sides like yours do. Mine are V2s.

Yeah, BG used to have V2 fans listed separately, but now it's gone. And if you order the regular FMS 12-blade 70mm 4s, you may or may not get V1 or V2. They claim to have changed the rotor and shroud stators, but the only difference I can discern is the spinner.

I have a V1 fan in my A-4, two V1's in my F-4, and 6 V2's in the Valkyrie ... I don't see a difference.

 

[Sotm]

EDFS

Yeah, BG used to have V2 fans listed separately, but now it's gone. And if you order the regular FMS 12-blade 70mm 4s, you may or may not get V1 or V2. They claim to have changed the rotor and shroud stators, but the only difference I can discern is the spinner.

I have a V1 fan in my A-4, two V1's in my F-4, and 6 V2's in the Valkyrie ... I don't see a difference.

I ordered mine from RC Castle (Hong Kong in 5 days had them) and theirs are all V2. Glad to see that ALL 6 of your Valkyrie are the same - just in case there was any performance difference.

 

[Mid7night]

Just a short clip of fun from Prado Airpark this weekend.

 

[Sotm]

Elevator throw ?

IT'S HERE!! THE F-4 IS FINALLY HERE!!

View attachment 97454 View attachment 97455



This is one project that I've actually been working on for quite a while, without posting ANYTHING about it here. I built #1 at Flite Fest Ohio, 2017, and it flew AWESOME. Flite Test even featured it a bit in their recap video. Ever since then, I've probably gotten more requests for plans for this jet than any other - which puzzles me because it's clearly NOT a trivial build!

But you all asked for it, and I promised I'd post plans when I finally flew my second build at home, so here you go! I'll put up as many build-pics as possible, but fair warning; they're not comprehensive. O_O So please ask questions as you go, I'll try to answer them as best I can, and hopefully others can learn along at once.


Details:

F-4 Phantom II
Power: 2 x 70mm 12-blade EDF
Battery: 6000mAh, 4S Graphene
Wingspan: 36 inches
Length: 54 inches
Weight: 85 ounces - (5lb, 5oz) - (2.4Kg)

DISCLAIMER: As of this post (11/2/2017), the plans are posted in "AS-IS" condition....meaning I still need to make some updates, but it flies, but be warned. Mostly, I need to move the motor-mounts BACK to make room to move the battery and ESC's back as well. If you build it per-plans, most likely it'll be nose heavy - which isn't bad, just not ideal. But I've kept this to myself long enough, I feel like it just needs to be out there for everyone to have fun with.

Also, you do NOT have to build the all-flying "Stabilator", you can get away with traditional elevators on a fixed horizontal stab. However, you will need two servos; one for each elevator.

PLANS:
- DOWNLOAD PDF ZIP -
- DOWNLOAD DXF ZIP -


Build pics below:

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Sorry there aren't more details on the build. If I find more, I'll post them. If you DO attempt this plane, PLEASE ask questions here so everyone can benefit from the answers!

Ben, I need your help. I built the flying stab version like here. I don't think I have enough throw, especially in the up elevator direction. Could you measure, at the leading edge, how far down your LE goes with full up on the transmitter for me please? mm or inches either one is fine. I don't think down elevator will be an issue, being nose heavy still. I'm asking here so everyone else can see it also.

Thanks

Duane

 

[Mid7night]

Ben, I need your help. I built the flying stab version like here. I don't think I have enough throw, especially in the up elevator direction. Could you measure, at the leading edge, how far down your LE goes with full up on the transmitter for me please? mm or inches either one is fine. I don't think down elevator will be an issue, being nose heavy still. I'm asking here so everyone else can see it also.

Thanks

Duane

Yes, I'll measure that when I get home from work.

I know that I had to cut in and put on a longer servo arm after the maiden flight to increase the elevator throw, so you might need to do the same depending on your servo arm geometry. This is especially important if you plan on deflecting the flaps more than a few degrees ... they're quite powerful!

 

[Sotm]

Are you calculating including the center panel as a triangle, or a rectangle? Your span difference will give you a different answer, yeah.

Regardless, the drop test is a good one too. Also, make sure the CG is in front of the main gear!

I do not include the center part that is under the fuselage and ducts as that is not producing lift. I use 1/2 span measured from the duct edges out.
I never use center area that doesn't produce lift.

 

[Sotm]

Yes, I'll measure that when I get home from work.

I know that I had to cut in and put on a longer servo arm after the maiden flight to increase the elevator throw, so you might need to do the same depending on your servo arm geometry. This is especially important if you plan on deflecting the flaps more than a few degrees ... they're quite powerful!

Did you get a chance to get that elevator deflection for me yet?

 

[Mid7night]

No, sorry. Got distracted building Zephyr's F-86, then ran out of glue sticks and had to do family stuff. I'll set a reminder to do it when I get home.

 

[Sotm]

No, sorry. Got distracted building Zephyr's F-86, then ran out of glue sticks and had to do family stuff. I'll set a reminder to do it when I get home.

Thanks Ben - I really appreciate the help here. I'm hoping for some good weather up here soon.

 

[Chuppster]

No, sorry. Got distracted building Zephyr's F-86, then ran out of glue sticks and had to do family stuff. I'll set a reminder to do it when I get home.

I'm hoping for some pictures/comments of your build process so that I can have more ease when I tackle the F-86.

 

[Mid7night]

Measured as shown: 1.15" at the leading edge.

 

[Sotm]

Measured as shown: 1.15" at the leading edge.

View attachment 101796

Thanks Ben!

 

[Sotm]

Flight Time

What kind of flight time were you getting with on 4S 6000mah battery?

Also is your tail hook foam or 3D printed plastic?

 

[Mid7night]

What kind of flight time were you getting with on 4S 6000mah battery?

Also is your tail hook foam or 3D printed plastic?

I think I get about 4 minutes mixed flying. It's 3D printed.

 

[copout162]

Unable to get your plans to download for the F4 would love to give it a try if anyone could help me to get the plans for the F4 I would appreciate it. I was able to download the plans for the A4 Skyhawk and I am looking forward to starting on it this weekend. I would like to have the F4 twin in the batters box and ready to go up next after the A4. Great designs keep up the good work.

 

[Sotm]

Unable to get your plans to download for the F4 would love to give it a try if anyone could help me to get the plans for the F4 I would appreciate it. I was able to download the plans for the A4 Skyhawk and I am looking forward to starting on it this weekend. I would like to have the F4 twin in the batters box and ready to go up next after the A4. Great designs keep up the good work.

If you can PM me your e-mail I will e-mail them to you.