The F-16 has been a favorite of mine since the first time I saw it. My father was in the Air Force so I was surrounded by incredible military aircraft for most of my childhood. My infatuation with the F-16 reached its pinnacle after my father returned home from a flight in one. When I began my modeling career I figured I would have an F-16 as soon as I had enough experience to fly one, but even a small scale F-16 model had been out of my price range until now.
The wait is over! High End Technology is known in ducted fan circles for its affordable, great looking and flying electric ducted fan jets, and with the release of the HET F-16 they continue in that tradition.
|Weight:||44 oz. rtf|
|Receiver:||Hitec Electron 6|
|Battery:||2-2cell 3700 Polyquest 20c (4s)|
|Manufacturer:||High-End Technology RC|
|Additional components supplied by:||Warbirds-RC.com|
On first inspection, I felt that the kit quality was fairly good, but noted some areas of concern. The Fuselage, intake liner, exhaust liner, canopy frame, tail cone, and vertical fin are made from fiberglass, and overall the glass work was good, but there were a few blemishes and a surface crack coming from one of the spar slots. The fiberglass intake liner was also slightly separated from the inside of the intake.
My biggest concern was the main wood former; the glue joint between the main former and the fuselage was loose allowing the former to move inside. This former is responsible for holding the intake liner, the fan assembly, and also the spars for the wings.
The assembly manual (provided on CD-ROM) recommends adding the wings as one of the first steps, but I chose to skip the wings for the time being so I could focus on the power system and the reported intake collapse issues.
Assembly of the power system is straightforward. The motor is held in place in the fan with two small included screws. The rotor assembly is held in place on the motor by a colleted adapter and one bolt. The rotor and spinner are one piece and come pre-balanced, but checking the balance of the rotor assembly is still recommended. A circular aluminum ring is then added to the back of the fan shroud to help center the motor in the shroud and also help cool the motor (a few small drops of CA might be needed to hold the ring in place). It all makes for a very easy and tidy installation.
There are two schools of thought on controller placement in an electric ducted fan aircraft: One side says to put the controller directly behind the motor so it stays nice and cool in the air going down the exhaust tube, the other side says to get it out of the exhaust tube because it creates turbulence in the airflow thus slightly reducing speed and thrust (also placement of the esc in the exhaust duct can result in very long battery to controller wiring depending on the airframe). Who is right? Both? Neither? For me, the controller placement is determined by the receiver and ubec placement. My first choice was to put the ESC behind the motor in the exhaust stream but I will only do that if the receiver is not in the general location and the battery wires don’t get too long. If I decided that it would be easier to put the receiver in the rear of the airframe, then the controller goes up front. For the F-16 review I decided to put the ESC behind the motor.
The key to successful ESC installation is to get it mounted directly behind the motor with as little obstruction into the exhaust duct as possible. and to make sure that it is mounted securely. If it moves in the duct it could cause excessive turbulence. I used a sleeve of battery heat shrink to keep everything together, and to keep the ESC mounted securely, I taped the battery wires together (to reduce drag) and then taped this to the top of the fan housing to keep the ESC centered directly behind the motor.
The fiberglass thrust tube is glued to the back of the fan with a few drops of CA. (Don’t add too much glue in case you need to get to the controller or motor later for repair or replacement.) The thrust tube is a little flimsy, so I added carbon tow to make it stiffer. Normally this would not be too big of a deal, but on this model the fan assembly is pushed into place by the thrust tube into the intake in the main wood fuse former. NOTE: The mounting brackets on the fan are cut off.
When it was time to insert the fan assembly into the intake and wood fuse former, it did not fit! There was a bunch of excess glue inside the intake where the two halves of the intake join, and I had to sand the inside of the intake in order to get the fan to fit. After 22 minutes of sanding in this very tight space, I finally got the fan to fit. After the fan assembly is in place, the thrust tube can be cut to its proper length. The gray fiberglass tail cone eventually glues on to the end of the thrust tube. Be sure not to glue the fan into the intake and fuse former.
I had finished assembling my power system and temporarily installed it in the airframe. Now it was time to see if my duct would also collapse as had been previously reported. The 2w-18 motor provided for the review is a 4 cell LiPo battery motor. I decided to try a 3 cell battery first to see if it would collapse on less power before I upped the ante. I hooked everything up and advanced the throttle. I was one of the unlucky ones - my intake duct collapsed just before full throttle on only 3 cells. Talk about frustration! The Intake duct is glued inside the fuse at the factory, so it would take some fairly major surgery to get it out.
I decided to give Markos at Warbirds-RC.com a call to see what his experience was with this problem. Markos was apologetic and said he had heard from other people who were experiencing the same problem. Markos is a distributor and not a manufacturer, so there wasn’t a whole lot he could do except to refund money back to those that had bought kits from him, which he was in the process of doing. He also stated that a fix was in the works and would get back to me when it was finalized.
According to an RCGroups.com thread, there were a few individuals that were completely removing the intake duct to fix the problem. I really didn’t want to do this, so I ran a carbon tube down the center of the intake duct (on the outside - top). After the rod was secured, I ran carbon fiber strips across the duct and secured them with CA. I then cut 4 strips of 6mm Depron and stuffed them between the duct and the bottom of the fuse (not seen in the pictures). I used thick, odorless CA to secure the Depron strips in place to both the bottom of the fuse and the bottom of the intake duct. Finally, I lifted up the front of the intake duct and ran a bead of epoxy under it and secured it to the front of the fuse intake.
After the completed repairs, the duct seemed strong enough to handle the power system. I reinstalled the power system and tested it on a 3 cell battery, and it held up perfectly. But since it was designed to run with a 4 cell battery, it needed to be able to handle that. Perfect! The duct withstood 834 watts nicely. I was really impressed with the power level I was seeing, but I was very concerned that I had a reading of 64 amps to go along with those 834 watts. The 2w-18 motor is not very big, and I knew this motor was pushing it at 64 amps but decide to give it a go in the F-16.
NOTE: Initially, Markos at Warbirds-RC.com gave me the option to choose the 2w-18 motor or the 2w-20 motor. I chose the 2w-18 motor because I wanted the extra power that it promised. We were both unaware of exactly how high the current levels would be in the HET fan. This motor would be better suited to the Wemotec Minifan which exerts less of a load on the motor.
After the duct, I was happy to move onto the wings. The wings are simply glued to the side of the fuselage with epoxy after the spars are attached. I decided to test fit the wings first before I permanently installed them, and to my disappointment, they did not exactly fit well. The front of the wings were flat against the fuselage but the rear of the wings had a gap. Although the manual does not mention it, I recommend that the wing saddle be sanded before attaching the wing to ensure a stronger glue joint. The sanding will flatten the wing saddle and help to eliminate the wing gap.
There are no ailerons on the HET F-16. The full-flying stabs provide the pitch and roll control (tailerons). The stab assembly is rather unique, but easily built. The stab blocks glue into the rear of the fuselage. A hole is goes through the fuse into the stab blocks, and the pivot rods glue into them. The stabs slide onto the pivot rods and are held in place with wheel collars. The manual recommends using the supplied plywood control horns on the stabs, but I decided to use Dubro 1/2A control horns instead. The supplied control horns seemed rather flimsy, especially for an aircraft that would be exceeding 100 mph.
Since the F-16 is controlled by tailerons, only two servos are required to fly the plane. (Hitec HS-65 servos were used for this review.) Before the servos are installed, a small access hatch must be cut out at the rear of the fuselage. The servos mount to a small mounting bracket that is built from three pieces of laser cut plywood. A trial fit of the mounting bracket into the fuselage revealed that there was some excess epoxy inside the fuselage keeping the bracket from mounting flush, so I notched the front of the mounting bracket to allow it to sit flush in the fuselage. The servo assembly lines up with the access hatch and glues to the inside of the fuselage.
Before the pushrods can be installed, a small opening must be cut into the bottom of the fuselage to allow the pushrods to exit. The instruction manual recommends using control rods that have z-bends at both ends to link the servos and tailerons. I tried that method, but found it difficult to get everything to line up without having adjustment built in. I decided to use a z-bend at the servo end and an EZ connector at the taileron end. This proved to be a quick, slop free setup. As previously noted, I also decided not to use the supplied plywood control horns.
NOTE: The servos need to be removed in order to get the fan assembly mounted in the fuselage.
The vertical fin is made from fiberglass. It seems to be a bit heavier than it needs to be but is formed well. The bottom of my the fin was not straight and did not fit perfectly on the fuse. It bowed up slightly in the middle providing little gluing area. Sanding both ends of the fin with a sanding block solved the problem.
The fin base itself was a small issue. It was so short that it was hard to get a solid glue joint between the fin and the fin base. Before the fin is glued, a hole is cut into the top of the fin base. (I am guessing the cut is to provide an air exit through the back of the fin.) The receiver antennae can also be run through the fuse and out the back of the fin after passing through the opening. The fin is simply glued onto the fin base with epoxy. After the fin was installed, I covered the glue joint with automotive pinstripe.
At this point I decided to permanently mount the fiberglass tail cone. The tail cone is glued onto the end of the thrust tube. The instruction manual recommends attaching the power system to the back of the fuselage with screws placed through the tail cone. I used 3M tape instead. It was much simpler and holds the power system in place very well. I also decided to cover the servo holes with Monokote trim sheet pieces since assembly of the major fuselage components were complete.
The canopy assembly consists of cutting out the clear plastic canopy and gluing it into the fiberglass canopy frame. The manual recommends a retention pin at the front of the canopy and a magnet at the back, and I chose to use a screw assembly at the back instead. I wasn't too confident that the canopy would stay on at full throttle with just a magnet.
The receiver mounts in the front under the canopy with Velcro. I ran the antennae through the fuse, out of the hole that I had previously cut in the fin base, and out the back of the fin. The external BEC was also mounted with Velcro under the canopy but as far away from the receiver as possible. I then installed a strip of Velcro along the cockpit floor for the battery. The bungee hook is installed with epoxy in a hole that must be drilled 25mm behind the bottom fuselage intake separation joint.
With everything mounted it was time to balance the model. The balance point is listed as 75mm from the leading edge of the wing (where it joins the fuselage). In order to achieve the desired center of gravity, I had to mount the 4 cell 3700 battery at the rear of the cockpit.
There was a break in the weather so I rushed out to the field with all of my support gear to get the F-16 in the air. Upon arrival I immediately began the task of setting up the bungee system, pointing it directly into the wind. The wind was blowing a little briskly, but not too much so. I range tested and everything checked out fine. I placed the F-16 on the end of my bungee and checked with my camera operator to make sure we were rolling. Just then the wind shifted and began blowing across our launch area. I pulled the F-16 off of the bungee and relocated it heading into the wind. In the meantime, a few other fliers were looking for some airtime, so I let them go ahead of me since I wanted to do this maiden flight by myself. After they landed, I set the bungee back up heading into the wind and got ready for takeoff.
The camera was rolling. I hooked the F-16 onto the bungee and placed it onto my launch carpet. I stood back with my foot on the pedal, took a big breath and stepped on the release button. The F-16 shot off the carpet like a rocket. It immediately began to roll left uncontrollably. I could hear the motor pulsing but there was nothing I could do... it was all over in less than four seconds.
I was in complete shock. This was only the second time in my modeling career that I had lost a plane on the first flight. At this point, I was kicking myself for not doing another range check after I moved from my initial bungee location. The damage was pretty bad: the fuse was split, the fin was cracked, the servo mounts were loose and the main former and wing spars were cracked. I picked up the pieces of the F-16 and headed home. It seemed like radio interference to me since I was able to control the radio system after the crash. But the cause of the radio interference is undetermined.
I made a quick call to Markos at Warbirds-RC.com (again!) and told him about my not so stellar first flight. He did not seemed fazed at all. If I remember correctly, he said "well... it does happen.” I offered to buy another kit from Markos so I could continue with my review. He refused, and instead he insisted that he send another one free of charge! He didn't want the review to take away from my own personal finances. Although I did insist that the third kit would be on me if the second one crashed, and he agreed. He was also interested to see what I though about the new kit that would be offered soon with upgraded intake duct. It was about a month before he received his new F-16 kits, and my new F-16 kit was on my doorstep three days after Markos received it. Now, that’s some customer service.
Between the time of the crash and my new F-16 arriving, I had the opportunity to attend the JR Indoor Electric Festival. While at the festival, I had the chance to meet Jason Cole from Hobby Lobby. I thanked him for providing the battery for the review and for Hobby Lobby's support of RCGroups, and soon the F-16 crash became part of the discussion. As we talked we discussed the additional items I would need to complete the second F-16 kit that was on its way. Before I knew it, Jason said to expect a box with those items shortly after he returned back to work. He was a man of his word - not much over a week later, a box from Hobby Lobby showed up at my door.
I won’t go into details of the assembly of the second aircraft since it is almost exactly like the first, but I will give some of the highs and lows of the new kit.
The new intake duct was much more rigid than the previous intake duct. The intake duct was installed rigidly but it was a little sloppy around the fuselage intake as noted in the picture. The following pictures also show other issues with the kit.
Note: The shipping box showed no indication of being mishandled.
It was apparent that the RPM per volt of the HET 2w-18 motor was a little too high for the HET fan on 4 cells. The full throttle current pull was 64 amps and 834 watts. I wanted to get the current back down to a more reasonable 50 amps. Even during my short initial power tests with the 2w-18 motor, it was getting warmer than I expected. I was happy with my previous experience with the HET 2w-20 in a minifan on 4 cells so I decided to go with that combo in my F-16 as well. I must admit I prefer the HET shroud to the minifan shroud. It holds the motor more securely and seems to center it better. I decided to use all of the minifan parts except for the shroud. My initial run up with the new motor and fan proved to be more realistic for a motor of this size, or lack thereof. 768 watts at 50.8 amps.
Many months in central Ohio had passed since the burial of the first F-16, so I had a bit of time to think about what might have happened on that memorable day. I hauled all of my flight gear out to the field and set up the bungee. In the back of my mind I kept telling myself to do a complete range check right before the flight. After the range check was complete, I set the aircraft on the end of the bungee and set the hook on the launch pedal.
I gathered my thoughts and stepped on the launch pedal. The F-16 shot off of the end of the bungee and slowly began to turn to the left. This time the turn was controllable. The F-16 accelerated rapidly so I eased off the throttle to trim it out. The F-16 needed a bunch of up elevator and a couple clicks of right taileron to fly straight and level. It needed so much up elevator that I was wondering if the balance point in the manual was wrong, but once the F-16 was trimmed out it flew exceptionally well.
Since the F-16 is a jet, and jets should be fast, I decided to do some high speed passes while the batteries were at their peak. I climbed out to the end of the airfield, did a split S, and came right down the runway at full throttle. Wow! This is the fastest EDF aircraft that I have flown to date and I have about 8 EDFs under my belt (including a HET sniper with a Kontronik Fun 480-33). After the full throttle pass, I pulled up at the other end of the field and climbed straight up until I could hardly see the F-16. I would say that the F-16 is close to having unlimited vertical, but not quite, although it gets so high so fast that it becomes hard to see. My cameraman was having a hard time keeping up with a mostly white plane on an overcast day so I decided to slow it down a bit to get some better video and try some other maneuvers.
The rolls on the F-16 are a bit more axial than I would expect from a taileron only plane but the taileron are on the thrust line so it makes sense. The loops can be almost as large as you want them to be. The F-16 has no tendency to fall out of the top of the loop as long as power is supplied throughout the maneuver. Inverted flight is very easy, although it does take a bit of down elevator to stay level. Some of the jets that I have flown in the past have had a tendency to wobble or high speed stall when entering maneuvers abruptly. The HET F-16 does not show any of those tendencies. The F-16 tracks very well although a slight tail waggle is noticeable at times.
After about 6 minutes in the air, I wanted to get a good feel for how the F-16 would handle on final approach. I took the it up to about three mistakes high, pulled back the throttle, and began to slow the model down. The F-16 slowed down very nicely. Just before it stalled, the wings started to rock slightly back and forth - a good indication to add more power or set it down during landing. The stall was very mild and only fell off slightly to the right. A quick burst of power and some up elevator had it flying straight and level again in no time. I brought the F-16 around and lined it up into the wind. I slowly began to reduce the throttle and let the F-16 settle in. It has a tendency to float a little on landing, so I slowly added in more elevator until I saw the familiar wing rock from moments ago. I knew I was fairly close to stall so I gently set the F-16 down on the grass runway. It bounced off of the grass a couple of times and came to and abrupt stop. It was a completely enjoyable maiden flight and I was thrilled to have this one down in one piece.
Although the HET F-16 flies very well it is not for beginners. It is a very quick and extremely nimble model. I would recommend that a modeler have multiple sport plane and beginner EDF aircraft experience.
I went into this project hoping for the great looking and great flying F-16 that I had always wanted. Although I eventually ended up where I had hoped, the ride along the way was a little... interesting. The HET F-16 could be so much more if only a bit more attention to detail was paid in manufacturing. The problems are easily fixed (except for the collapsing duct on the first run of kits) but should not have to be dealt with in this day and age of superb ARF aircraft. Given the HET F-16's great looks and great flying qualities, I would definitely build number 3 if this one goes in.
More flights and video coming in the near future!
|Jun 29, 2007, 06:16 PM|
Very thorough review Kevin. It is quite an enjoyable read IMHO. Honest but not critically or unfairly. And in spite of your problems, your persistence proves this to be a high performance EDF worthy of consideration. Kudos to Markos as well as Jason. First class red carpet treatment for sure!
|Jun 29, 2007, 07:40 PM|
Due to the unfortunate demise of the first F-16, your review is a bit late. The new kits with the stronger intakes were on the market for months now. For those interested in the F-16, you don't need to reinforce the intake, I would suggest not using the stock exhaust tube and using mylar, and not suggest this plane for a first edf. Biggest thing to watch out for is not having any slop in the tailerons. As Kevin mentioned the rocking of the wings, I have that problem but none of the others here (4 of them) and the only thing different is that my tailerons have some free movement.
Sorry Kevin, your review was good but I think it would have been a better representation if the build portion was for your second (newer) kit.
|Jun 29, 2007, 09:09 PM|
Thanks for the compliments guys. Even with the initial problems it was an enjoyable experience.... And the f-16 is a definite thrill ride.
Markos at warbirds and Jason at Hobby-lobby are top notch but you guys already know that.
point taken. I struggled with how to approach the two kit review. But I eventually ended up doing it the way I did because:
-There are still f-16's out there that are the old version… So I wanted to give it some press. There was no way to avoid it…. it did happen…And as you can tell I believe in putting it all there. Kudos to all involved for letting this get published. I have had reviews cancelled by vendors because they were not perfect.
-The duct was an unfortunate oversight but I wanted to show in a little bit of detail the process that happened and how it was handled from a manufacturer (HET) and distributor (Warbirds-rc.com) perspective.
-I had already set up the pics and most of the script for the first review before the crash so I didn’t want to drag this out any longer by starting from complete scratch. (I had taken 178 pics for the first review)The new kit is almost identical except for the duct.
The script below is highlighted in the review so there should be no confusion on the fact that the new kits are fixed.
NOTE: A new fuse and complete kit were released with a stronger duct that does not collapse. If you buy a new kit from Warbirds-RC.com now it will be the new version.
|Jun 29, 2007, 09:37 PM|
Well, if I took that many pics and spent that much time writing up the first kit I wouldn't change it either.
Check your tailerons and make sure there's no free movement. I'll either have to redo the z bends or I'll try clevises. The guys here slow it down a lot on landing, even inducing a stall all it does is drop the nose.
|Jun 29, 2007, 09:54 PM|
No slop at all in my linkage system. Note that i only have one flight on this airframe so i plan on playing with cg and higher alpha landings but i didnt want to get it too slow on the first landing. After seeing the first flight on the first F-16 i am sure you can understand
hoping for a couple more flights (and video) this weekend.
|Jun 30, 2007, 12:33 AM|
Good review and thanks for being honest. I have the new kit and am very dissapointed in the quailty, so much so that I just put it back in the box after getting it about 50% complete. Too much fixing that needs to be done. The quality is terrible. I am surprised that they let these things leave the factory like this.
|Jun 30, 2007, 01:34 AM|
Joined Apr 2006
Kevin check the cg, you might want to move the cg forward a little if you have that much up elevator.
On a windy day i can actually slow that thing to a stop at about 500 ft (Cliff get Joe to make a video), thats how slow that thing will go without rocking the wings. As Cliff said any slop can be really annoying in flight especially at the speeds we fly them over here...we saw one disintigrate inflight the other day.
Good luck and have lots of fun with it!!!!It is an AWESOME PLANE... I have flown all the planes het makes except the f4 and IMO this is by far the fastest with the 2w+het 6904 setup that is... ALL HET PLANES ARE FRICKIN AWSOME!!!.
|Jun 30, 2007, 10:41 PM|
I've been wanting a 2nd DF plane ever since buying my Kyosho Illusion. I see HET all over these forums and have been on their website many times. I thank you for your fair and honest (but not brutal) review. I don't think it could have been reviewed any better. And I'm impressed with the level of customer service from Warbirds-rc.com and Hobby Lobby.
However, I will not be buying one of these F-16s. It's one thing to have problems on your first runs of kits, but it's another to have more and different problems on the 2nd run. The QC is obviously lax - who the heck put a broken CD into the box? It was known this was the 2nd kit for your review, yet the CD was broken and it had ill-fitting parts.
I'm an ARF guy through and through - my idea of the perfect ARF is to throw a bottle of CA into an ARF airplane box, shake vigorously for 10 minues, and out comes an airplane. I have no interest for a plane that needs modification during assembly, and barely have patience to assemble a well-designed ARF, let alone one that doesn't work right out of the box.
Thanks for the honest review; I'll be taking my money elsewhere when looking for an F-16.
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