HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 06, 2013, 10:26 PM
Registered User
United States, TN, Millington
Joined Jul 2012
71 Posts
Discussion
F-22 Profile EDF

All,

The story begins with a BlitzRCWorks F-4 Phantom 64mm that I was given by a friend. He had bought it for his son, who halfway assembled it and lost interest. Good thing, he would have had a chore flying it as his first RC airplane. So I put it together, tried to fly it, could not get it in the air, finally got it flying, and finally it went into the ground from a bad launch and that was that for my Phantom.

The power system and electronics were undamaged, but the airframe was a total loss. What to do???

I found these plans, and decided what the heck. Same fan size as my Phantom, I had everything else on hand, what's a couple of bucks in Dollar Tree foam gonna hurt if it doesn't work?

So, I downloaded the plans, bought some foam, started cutting and gluing, and two nights later came up with this. I didn't take too much care with it, so some of the lines aren't straight and the pieces could probably fit together a bit better. But, it's a prototype, and I was in a bit of a hurry.

So today, I took my new Raptor out to the field, gave her a toss, and up she went! This one is a real hoot to fly. Lots of control authority. Loops, rolls, and turns almost in place. High-alpha is possible, but you've got to be on it at all times.

Now, the minuses. She's tail heavy, and VERY pitchy. I almost lost her a couple of times. Got to add a bit of nose weight. Also, she's underpowered. I put that down to the lack of a thrust tube. I'm thinking a Styrofoam drinking cup cut in half long-ways and glued top and bottom of the wing would work perfectly for this.

But these are all very fixable issues. As a proof-of-concept, it's a complete win. I'm going to make another airframe, and take much more care with getting the fit right. Add a little paint and scale detail, hide the electronics inside the intakes, and this could be a real winner.

I do hate making new threads, but I couldn't find one for this particular project. I hope this is of interest, and if anyone has built one of these or one similar, any advice for future builds would be most appreciated!

I took a video, but it's not quite the best. If anyone wants to see it I'll post, but I'm hoping to get a better one this weekend.

GrayFlyer
GrayFlyer is offline Find More Posts by GrayFlyer
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 06, 2013, 10:53 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,876 Posts
Welcome to the Scratch build forum. What ever one decides to build, it really does'nt matter. As long as you build!! Looks like a fun little jet. Simple and basic. I have 3/4 of a case of MPF left after my Scorpion build, and I plan on making one or two "easy" flyers myself. The F-16 that sloperjoe has is on my list.
Good luck, will be watching.
CoolerByTheLake is offline Find More Posts by CoolerByTheLake
Reply With Quote
Old Aug 06, 2013, 11:30 PM
Registered User
United States, TN, Millington
Joined Jul 2012
71 Posts
CbtL,

Thanks! Do you think that adding a thrust tuube would help with performance? Or just not bother?

GrayFlyer
GrayFlyer is offline Find More Posts by GrayFlyer
Reply With Quote
Old Aug 06, 2013, 11:50 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
United States, MN, Hermantown
Joined Dec 2008
5,876 Posts
I would. Even the guys running the fan in a pod, use at least some sort of thrust tube. A lot of guys doing the A-10 have also done it.
CoolerByTheLake is offline Find More Posts by CoolerByTheLake
Reply With Quote
Old Aug 10, 2013, 12:41 AM
Registered User
SNice's Avatar
Philadelphia, PA
Joined Aug 2009
1,031 Posts
Congrats on a successful scratchbuild! Nothin' like getting something in the air that you built yourself!

I love the raptor - it was one of my first scratchbuilds - and I went the EDF route too! I'm not that familiar with the Mikey's raptor. Is the paper left on? I built the profile raptor by Tomhe - it is featured on www.6mmflyrc.com. Great, sturdy airframe. Mine is Dollar Tree Foam (DTF) with the paper removed. Actually, I only left the paper on the rudders. I also later added a carbon arrow shaft in the wing for strength. The only mods I did were to add some foam panels to the nose to create a 3D effect and to convert it to EDF. I've had a single 64mm, twin 55mm, and a single 70mm all in this airframe - and all flew great. The 64mm was the lightest, most versatile and maneuverable. The twin 55's hat the most thrust, and the 70mm had the speed.

Your thrust tube dilemma should be based on how you want the model to fly. Thrust tubes will give you more top end speed but they will reduce your acceleration and thrust. I put thrust tubes on my low drag, speedy EDF's. The F22 is pretty draggy and in my book is more of an aerobat than a speed demon. You want it to be able to fly slow in high alpha and have some decent speed. The thrust vectoring is the "funnest" part of this model. You also would not want to reduce the airflow over your thrust vectoring notches. For these reasons - on this particular airframe - I would leave the back end of the fan open.

Also - the cleanliness of the air that gets to your EDF has a lot to do with how it will perform. There should be as few obstructions as possible in front of the fan. That wedge on the nose could be creating a lot of turbulence for your fan which could lessen its performance.

Here's my 64mm version in action:
F-22 Parkjet 64mm EDF (4 min 57 sec)

F-22 Parkjet R/C 64mm EDF: Low & Slow High Alpha (6 min 29 sec)


These are the stats for that model:
AR500 RX
5250KV 64mm EDF
3S 2200mah 30C lipo
40A ESC
2x 9g servo (tailerons)
2x 5g servo (rudders)
AUW: 19.8oz
28" Wingspan

Here's the thread for tomhe's F-22:
http://www.rcgroups.com/forums/showt...8#post15355599

One of the best parts about scratchbuilding is experimentation! So have at it! Give all of your options a try - test 'em all out - It will only strengthen your skills for future builds! Best of luck & keep us posted!
SNice is offline Find More Posts by SNice
Reply With Quote
Old Aug 10, 2013, 08:01 AM
Registered User
United States, TN, Millington
Joined Jul 2012
71 Posts
Snice,

Thanks for the kind words! I did leave the paper on for this build, and it seems to be working just fine. I didn't have to bend any pieces, so there was no need to take the paper off. The wedge is there (I guess) to improve aerodynamics over the battery. This just can be built as either a single or twin 64mm, and with the twin to use dual batteries, so a fairing like that would be needed.

I tried the thrust tube, and took it right back off after the first flight. It lost speed from top to bottom. It gained "focus" for the air thrust, but also a lot of restriction. So, back to the way it was.

I was actually looking at the 6mmfly F-22 for the next one, either the profile or "full fuse" version. When you did yours with twin 55's, would they completely fit inside? I'm looking for a way to make it as scale as possible without the fan poking through. The profile F-16 he has is also a nice looking plane. Any info you could provide would be most appreciated!

10 flights so far on this F-22, so I think we can call the "flying foam board" experiment a success. Next one I plan to paint and make look more realistic, like yours.

Back to the field today for some more fun. Thanks again!

GrayFlyer
GrayFlyer is offline Find More Posts by GrayFlyer
Reply With Quote
Old Aug 10, 2013, 11:41 AM
Registered User
SNice's Avatar
Philadelphia, PA
Joined Aug 2009
1,031 Posts
The paper can be good for strengthening but it comes at a significant weight penalty. The paper accounts for about 40% of the weight of a sheet of DTF. For foamy EDF's, lighter is generally better .

Thrust tubes can be tricky because the exit area has to be calculated according to the size of the fan. I usually put my exit areas at about 85% of the FSA (Fan Swept Area). That gives a good mix of thrust and acceleration.

As for the twin setup - the twin 55mm fans are exposed - Its actually the same airframe - I made switchable motor mounting plates for my different power configurations. The motors are a bit out of sync so it has an annoying whine sound.

F-22 Parkjet Twin 55mm EDF (3 min 36 sec)


If you want to go the full fuse route - Steve shumate's F22 (also on 6mmflyrc.com) is an excellent candidate. You would have to modify it a bit - maybe even scale it up a bit to get the fan(s) to fit, but it would work. Others have done it so you might want to do a quick search. For the full fuse model, you would definitely need a thrust tube and clean inlets and air intakes are a must.

You can always tell a good fan inlet setup by how the EDF sounds. Struggling fans tend to whine - while fans with good inlets and unobstructed airflows are much quieter and have more of a "whoosh" sound. Yes, in all three videos above, my fans are "whining" - they are getting a lot of dirty air from the forward part of the fuse. Luckily the airframes are light enough that the fans still provide more than enough power.

Good luck! I had plans to do a shumate F22 conversion but ended up doing the conversion on his F-18 superhornet design.
SNice is offline Find More Posts by SNice
Last edited by SNice; Aug 10, 2013 at 11:50 AM.
Reply With Quote
Old Aug 12, 2013, 01:33 PM
Registered User
United States, TN, Millington
Joined Jul 2012
71 Posts
Snice,

Looks like a plan! I'm starting to draw up a materials list. I'll either do the Shumate F-22 or the profile F-16 from 6mmfly.com. Both would be fun, I'm thinking. Whichever I do will be an EDF conversion.

One question, though. I used a spray bottle of isopropyl alcohol to remove the paper from a piece of DTF I had left from the last project. Came off clean as you please, but the foam now seems very flimsy and flexible. Would that truly be good for these planes? For something like the F-22's fuselage I can see it, with all the pieces glues and laminated together. But the vertical and horizontal stabs, I'm thinking they'd just flutter around. Would you suggest leaving the paper on these pieces?

Thanks again!

GrayFlyer
GrayFlyer is offline Find More Posts by GrayFlyer
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale F-22 $ 60.00 64mm Shumate design converted to edf VIDEOPRO Aircraft - Electric - Jets (FS/W) 1 Aug 11, 2014 11:48 PM
For Sale F-22 Raptor EDF Jet ChuckieD1 Aircraft - Electric - Airplanes (FS/W) 1 Feb 18, 2013 10:14 AM
Build Log Ultra Micro F-22 Profile Raptor with 22mm EDF Razors edge 29 Micro EDF Jets and Power Systems 30 May 16, 2011 10:44 AM