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Phase 3 F-16 pusher conversion build thread

Old 01-28-2010, 03:19 AM
  #1  
Wrench66
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Default Phase 3 F-16 pusher conversion build thread

"What would the Phase 3 EF16 be like to fly using a pusher setup??"

The question had been nagging me for a bit.......would converting and EDF plane to pusher be worth the trouble?
Well, the answer has been a definite YES for me....

This particular build has been coming for some time now......I see a lot of super cool EDF planes that I would like to fly BUT I didn't want to hassle with the actual EDF system and it's tremendous inefficiency. My thought was to make use of the 175W flying wing powertrains I have been using to convert a popular EDF jet into a pusher configuration that would be efficient AND lightweight AND maybe in the mix there would be a "fun factor" somewhere...LOL.
Since the EF16 has been on sale recently for less than $40 it was the perfect time to convert it without too much invested IF it were to be a bomb.
I started by taking the entire plane's bare weight into account, even noting where the CG was to begin with (just mocked up, no gluing yet) because I had to be aware that with moving the powertrain back to the planes tail I would always be pushing ( pun) to keep as much weight forward.....if possible.
As luck would have it, the F16 design has a lot of fuse in front of the wing's CG....allowing the balancing question to be solved without much brain-wracking...LOL

Pics to follow.....dinner's ready!!

--Ray
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Old 01-28-2010, 03:56 AM
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Subscribed. I have a 3000Kv Wicked motor from Don looking for a home. Lately I have been feeling a need for speed .

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Old 01-28-2010, 04:35 AM
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Hi Smoke, I'm diggin the OK ANG F-16 you have there....

OK, pics are on.....
Using a piece of 9mm Depron scrap, I cut a circle out to "plug" the exhaust outlet to make a firewall. I originally (things changed quickly...) was happy with the depron/lite ply firewall set up as it made adjusting the thrust line (unknown entity at this point) very easy. The next mod was to section the intake housing so I could >>1. get to the esc and motor connectors easily...and 2. so I could make the lower housing removeable to service the electronics easier. The aft section of the lower intake housing was to be glued solid to the upper so as to make the rear firewall as stout as possible. The orig plan for mounting the lower housing to the fuse was to use leftover outrunner magnets (super strong) on cross braces much like I have done before with canopy mounting.
These are the pics of the solid firewall......before I cut four pinkie finger sized holes equally around the firewalls diameter.

...but even with the vents, it wasn't quite right
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Old 01-28-2010, 06:20 AM
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Alpea42
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get to the good part.
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Old 01-28-2010, 04:28 PM
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hehe..OK

Another mod was to make use of that lonnnngggggg nose by placing a few grams of adjustable ballast way forward inside the nose cone. I used a 20w soldering iron to cut 2 1/8in diameter holes in the bottom of the nose so I could house 1-2 5gr lead bullets as needed. I then made the nose cone removable by cutting to small trenches at the nose's mid line, using a couple of small wooden rectangles (cut from coffee stir sticks) glued in then making a couple of tiny holes into the sides of the plastic nose cone to run the servo mounting screws through. Done
The rest of the build was progressing well, the plane was able to balance either with a 4oz battery secured in the forward most part of the compartment OR a 6oz pushed as far aft as possible. This was exactly what I had been working towards by paying so much attention to the CG during the assembly.....paid off, and the AUW was still hovering around 16oz with the smaller battery.
I should mention here that the power system I was using was the combination of the smallest, lightest but fastest I had. The motor is a Suppo 2208/12 1800kv weighing a slim 39gr, can develop more than 200W when asked though. I have bigger motors and some that are faster, but the weight penalty was too great......if I add an ounce onto her tail, I would need nearly that in the nose to maintain CG and that's going backwards from the core idea I had here to begin with
So, this little motor has done very well for me in my flying wings using an APC 6x5.5 prop it has shown itself to be quite useful.

OK, so at this point the plane was nearing completion and I'm ready to do some test pulls to see how close our power system was to being right.
I powered everything up and the with the mid sized 1750 3s battery I ran the very scientific "vertical pull in my hand" test that we all do....LOL. Seemed OK, but the thrust seems a touch weak......hmmmm, Wattmeter shows power is down just a touch from normal too but battery voltage shows perfect...... wonder why?
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Old 01-28-2010, 05:12 PM
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Default Interesting maiden

The weekend comes and the plane is ready, since it's quite a different EF-16 powerwise, there's a lot of excitement and hope that this will be a good flight.
I power everything up, make a quick check of the tailerons and their movements....yup, looks OK and moving in the right directions...LOL.
Goose the motor......seems OK, still that slightly off thrust question though.....hmm, but OK..it's ready I'M READY so let's go!
I ask Al (Alpea42) to do the launch honors, James has the video cam to record the maiden and I'm ready at the sticks.
I wind her up to approx 3/4 throttle and Al takes a couple steps and gives her an awesome throw!!
SHE'S UP!! and looking good while climbing out.....banking a bit to the left but otherwise flying stable as I start to feed in some right trim.
She's up approx 70ft as I start to turn back towards the flightline............Unfortunately that's where the story turns sour

Right when the plane had gathered a little speed and was making the left turn back down the flightline the lower intake cover ejected off the bottom of the plane!!!!! (remember the magnets?)
As this cover was sectioned, the firewall is now hanging down into the slipstream below the plane and doing it's best to imitate a barn door...LOL!
The drag from this immediately pitches the planes nose down at approx 91degrees () from where it was a nano second ago, I can't quite grasp what is happening but I do chop throttle and try to feed in some up elevator.
Well somehow I manage to level it off enough that it doesn't nose in......but because the bottom of the plane has no cover to slide on, the firewall/motor mount is the first part to touch down and the grass rips the entire rear of the plane off at the taileron pivots below the rudder!!! crap.....LOL.

Upon post maiden study, it seems that although I DID take into account that there would be air pressure in the intake tube at the firewall I obviously underestimated the AMOUNT of buildup there may be in that section of the plane...hehe. The exhaust ports I had made into the firewall were inadequate and the build up of air pressure was great enough in the intake to pull 4 rare earth magnets apart and let the intake depart company from the fuse......ugh.

Maiden video footage (pardon the outburst )

http://www.youtube.com/watch?v=aG8g6Mxpo0s
Glue, please :o
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Last edited by Wrench66; 01-29-2010 at 01:19 AM. Reason: added horrific video
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Old 01-29-2010, 12:08 AM
  #7  
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Ray , heres what i have done on my 16pusher , put servos flat used my home made servo covers , im not sure if it shows i raised the rear flat section up 1/4 inch , sanded and lined with .007 cf to make a cooling scoop ,i will be adding a keel to protect motor and to launch it by , not sure which motor to use ?.......pic not loading
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Old 01-29-2010, 12:21 AM
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@TbigD

http://www.wattflyer.com/forums/showthread.php?t=12385

The pics may be too big. I'd like to see them if you can get them to post.

@Ray

Lot's of good info Ray...keep it coming . If I have learned anything so far it's that I am going to want to take my time to get the balance right. The motor and battery I am going to use will weigh a considerable amount more than what you are using.
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Old 01-29-2010, 12:39 AM
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still cant post pics resized.....it , i get that standard web site not responding message , try this , this and this.....
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Old 01-29-2010, 12:49 AM
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What size are the pics?
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Old 01-29-2010, 12:57 AM
  #11  
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Originally Posted by TbigD View Post
Ray , heres what i have done on my 16pusher , put servos flat used my home made servo covers , im not sure if it shows i raised the rear flat section up 1/4 inch , sanded and lined with .007 cf to make a cooling scoop ,i will be adding a keel to protect motor and to launch it by , not sure which motor to use ?.......pic not loading
Hi Dennis,
That sounds like another good thought........gotta protect those servos and laying them down seems a good idea
I wanna see those pics!! hehe

Originally Posted by smokejohnson View Post
@TbigD

http://www.wattflyer.com/forums/showthread.php?t=12385

The pics may be too big. I'd like to see them if you can get them to post.

@Ray

Lot's of good info Ray...keep it coming . If I have learned anything so far it's that I am going to want to take my time to get the balance right. The motor and battery I am going to use will weigh a considerable amount more than what you are using.

Hi James,
Thanks. Yeah, the entire time I've thought about building a pusher jet has seen me wondering and fretting over the balance question all the while wanting the absolute lightest setup possible.....the plane is listed as 20oz AUW and I was sure I could come in at least 3-4oz under that.
As it sits now, I couldn't use a bigger motor AND keep my battery weight....one would def change the other since my lightest battery is as far forward as possible and the ballast recievers are full (approx 3/4oz aux weight in the nose). You COULD always use a larger heavier battery of course but then we get further away from the meat of my focus......lightness and low wing loading.

edit: AND of course, speed! hehe, what's a jet without some MPH, huh?!
Since my drive train is only 200W, I had to keep the weight in check....power to weight. As is, it's just about on par with a stock EF-16 speed wise but has much better climb when launching and overall flying.

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Old 01-29-2010, 01:37 AM
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I got to fly it. And I don't care to comment on the technicle B S . But I will tell ya Ray succeeded in coming up with a solid flying F-16.
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Old 01-29-2010, 03:00 AM
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Originally Posted by Alpea42 View Post
I got to fly it. And I don't care to comment on the technicle B S . But I will tell ya Ray succeeded in coming up with a solid flying F-16.
Thanks Al…..
OK so the intake tube is being pressurized by the firewall blocking the airflow, this also answers the question of why the thrust seemed a bit low during the initial check. Since the firewall is an approx 3in diameter it was seemingly masking the 6in prop at least a little. Using a Dremel tool the firewall was opened substantially more and with a change of motor mounting to stick, I now had enough free flowing air to keep the pressure from building AND supply the prop with all the air it could move.
I also added a couple of wood screws to ensure that the lower cover wouldn’t ever have another chance at coming off again! Hehe
The last thing I did was to add some orientation stripes to the planes upper surfaces……..initially it was bone white but for the field we would be at I wanted at least a shot at seeing top from bottom.
The second flight was very uneventful compared to the first…LOL…I had Al throw her again and at approx ¾ throttle she just flew away, I immediately felt comfortable with it as I dialed in some trim. I flew her around for approx 4min…..doing some WOT runs and a few super slow downs to check her reactions…..all very good. Top speed showed promise as it seemed about as fast as a stock EF-16 but with a little better climb. As I brought it in for landing she just floated in and touched down without any fuss. As the day progressed I flew her a total of five times using the lightest and the heaviest batteries I have……the plane flew great with them all, although the lightest was the most fun.
Run times were timed at approx 6min, the batteries coming down body temp and only taking approx 700mah on recharge…..hehe, fun and easy to own….hehe sounds like a commercial
Can't wait to see more pusher jets now!!
--Ray
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Old 01-29-2010, 10:54 AM
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How do you have the stick mounted to the plane?
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Old 01-30-2010, 01:32 AM
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Hi James,

Before I hacked away at the orig full firewall, I centered the motor mount and marked off where the stick would fit into the wooden firewall. Using a little Dremel tool, I drilled and ground a reciever hole for the square stick. Then I cut a simple 1.5in section of 10mm hardwood stick and epoxied it in, slide on the stick mount and you're done.

BTW....since I wanted a touch of downthrust I made sure the stick had the correct angle before the resin setup.

--Ray
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Old 02-01-2010, 03:10 AM
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Default new video

Here's a short video showing a little of it's speed capability.....the video was started after I had flown the plane for a couple of minutes but it still seems pretty quick for only pulling 215W...
Thanks again to Alpea42 for manning the camera...again..LOL

[media]http://www.youtube.com/watch?v=XG5acRKvMrc[/media]
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Old 02-02-2010, 12:59 AM
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Got more done on mine , i still cant post pics , i went down to 1 megapixel , from 6 , still wont download , i tried it on rc groups , wont there either.......
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Old 02-02-2010, 02:43 PM
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TbigD,

Try using www.photobucket.com . Then you can just insert it into the page.
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Old 02-02-2010, 08:28 PM
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Originally Posted by TbigD View Post
Got more done on mine , i still cant post pics , i went down to 1 megapixel , from 6 , still wont download , i tried it on rc groups , wont there either.......
If you are trying to upload straight from your camera it might not work. Download the photos to your desktop (or folder of your choice) first and then upload from there.
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Old 02-03-2010, 02:01 AM
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Thats the way i normally post pics (desktop) but somethings screwed up in my computer , it wont allow me to do it.....i tried photobucket , says i have a network error..
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Old 02-04-2010, 02:45 AM
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I give up , i got my laptop hooked up to the internet , tried to post pics , still wont work , tried some stuff Steve said to try , no go , called internet provider , of course they said connection was good............
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Old 02-04-2010, 03:12 AM
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Originally Posted by TbigD View Post
I give up , i got my laptop hooked up to the internet , tried to post pics , still wont work , tried some stuff Steve said to try , no go , called internet provider , of course they said connection was good............
Like Idealhobbies said, use photobucket.com its free and you can link to photos very easily.
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Old 02-04-2010, 06:21 AM
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LOL , that wont work either , says network error.............
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Old 02-04-2010, 07:11 AM
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Thats a real good lookin model Ray
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Old 02-04-2010, 08:01 AM
  #25  
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Hey thanks Mark

Hope to see ya sometime, man....been like furever...LOL
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