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The HobbyFlite 747

Pat Mattes captains HobbyFlite's easy entry into airline flying.

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Specifications:
  • Functions: 2 or 3-channel (rudder, elevator, and/or motor)
  • Wingspan: 48"
  • Wing Area: 450 sq.in.
  • Kit Weight: 11 oz (no equipment)
  • Flying Weight: 17 oz (glider), 22-28 oz (electric)
  • Price: $65 (motor package additional $45)

 

If you find HobbyFlite’s Boeing 747 while rummaging through a magazine or web site and think it’s "just another foamie", think again! At first glance it shares a similar look and feel to the $5 foamies you find in a toy store, but this is nothing like those little toys. The HobbyFlite 747 is a beautifully engineered and executed kit that stands in a league of its own. I was immediately impressed with the quality of the components when I opened up the box. I took all the parts out and handled each and every one before I even bothered to look for the instructions! All parts were well formed, with no warps, no voids or partial-fills in the corners and difficult to mold areas.

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The parts were nicely packaged, with Styrofoam blocks glued to the box in strategic locations to protect the contents. Chris Hill from HobbyFlite had provided the electric conversion package as well, which included a pre-wired 400 motor, tail cone motor mount, mounting screws, and two Gunther push-on props, already oriented for pusher flight configuration on the friction hubs. The motor leads had thoughtfully already been wired for reverse rotation.

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Getting Started

I had full intentions of jumping right into the review of the 747 as an electric conversion, but as I started pulling the parts out I knew I just had to try it as an non-powered glider first! The 747 is marketed as a slope glider or electric conversion, and it certainly appeared as though this would be a very quick build. All the control wires are pre-installed, the clear plastic control surfaces installed, and control horns glued on. There really wasn’t much to do.

The first section of this review is dedicated to the assembly of the 747 in "Glider Mode". The last section details the installation of the battery pack, controller and motor pod for the Electric Mode.

 

Servo installation

First item to attend to was putting the servos in. It wasn’t immediately clear from the instructions how they intended to mount the servos. They laid flat of course, but the illustration wasn’t clear. I found a more descriptive picture in the electric conversion attachment, but I’m not sure buyers would get this if buying it in ‘glider only’ mode. As the picture in the electric attachment shows, the forward servo gets placed upright, the rearward servo is placed upside down. This method provides clear movement for the control wires going to the rudder and elevator halves. Both servos are placed on either side of a molded in location bump, and fit in a pre-formed well.

I studied this a little before I installed the servos, and took it upon myself to place the servos differently than asked. The rudder control wire came through the foam at an angle that favored mounting the rudder servo upside down, as well as the elevator, so I mounted them both upside down with the servo arms pointing further into the fuselage. (It only appears that the control wires touch, they don’t!)

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You need to dig a small channel to clear out the path for the control wires and servo arms. I mounted the servos with double-sided sticky tape, then placed single sided tape over the top to further secure them. I used FMA S-80’s and they were a nice fit in the pockets provided.

The next step was to plug the stabilizers in. The elevators were already hinged and had the control horns glued in place. Each half attached easily to the Z-bends protruding from the fuselage and then were placed in the stabilizer receptacles on the fuselage. Now, here’s one of the neat ideas HobbyFlite has incorporated. The control wires for each control surface are multi-piece, with two lengths of heat-shrink tubing installed at the overlap point. Once your servo arm is centered, and the control wires hooked up to the stab halves, you heat up the shrink tubing with a soldering iron and makes adjustment a snap! Also, the clamp force is sufficient to keep things aligned and in place, but if you need further adjustment you can grasp the wires with needle nose pliers and slide the wire halves closer together or further apart. A neat idea! This is repeated for the rudder hookup as well.

After the control surfaces are hooked up and secure, you use the spare packing foam to create stand-off blocks to support the control wires. I didn’t think the drag of the control wire through the foam support would be significant, but I opted to dig through my junk box and install some plastic tubing bearings on the wires for reduced operating drag.

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You can’t see it from the picture, but I cut slots in the foam and pushed these plastic bushings further into the stand-off support and glued them in place.

If you do any "digging out" of the foam in the fuselage area for alternate servo mountings, please be careful to avoid taking too much material out. If you look on the OTHER side of where you might be digging, you’ll find the wing root cavities. You could reduce the structural strength.

 

Receiver Installation

This hardly requires a paragraph of its own, it's so simple. On the other fuselage half, a molded in pocket exists to put your receiver in and tape it in place. For my particular receiver, I had to widen and deepen the pocket. There is plenty of room provided, but the only spare receiver I had at the time required this modification. After a little foam routing with my Dremel, I taped the receiver into position.

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One item that’s a little out of sequence, but important, is antenna routing. For "glider mode" you can run the antenna forward and keep it concealed, but when converted to electric you’ve got long battery leads that play havoc with signal reception (at least in my case). For the electric conversion, I had to run the antenna outside the fuselage, up to the tail, and down to the stab. This kept it from being run parallel to the power cables, and eliminated the interference I was experiencing.

 

Balancing

The location of the CG is printed right on the bottom of the fuselage, which is a fantastic idea, especially since CG on a wing this highly swept can be difficult to determine. I went one step further and marked this same location on the inside of the fuselage, just in case the mark on the bottom got worn off after repeated landings. You are required to cut a pocket in the foam for the Rx battery pack, but I didn’t want to make it any larger than required (The instructions say to balance the plane by moving the Rx battery pack forward or aft) So, I turned the 747 upside down, fashioned a masking tape "handle" and placed the Rx pack where it needed to be in order to balance. This way it was "measure twice, cut once".

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When held upside down in this method, the bottom of the fuselage underneath the wing is absolutely flat, which makes it a nice "table" to place the Rx pack on to determine balance point. This really worked out well. The location of the Rx pack ended up being so close to the pre-formed FORWARD pocket, I decided to see if the 747 would balance if the pack was put there. It did. Plus, it saved me from having to cut any foam at all.

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Final Assembly

I don’t need to run through decal application, I’m sure you can handle that one just fine!

I connected the servos and receiver battery to the receiver and started to button things up for the test flight. I double checked to make sure I had smooth servo actuation. Then, I put the two halves of the fuselage together and taped the seam.

After the usual radio checks, and making sure the right parts moved with the right stick input, I did a final balance check and pronounced it ready for first flight. A step or two, a gentle toss, and away she went. The 747 certainly looked awesome as it went away from me. Very graceful, and very slow. I made a couple of trim adjustments and another toss. Very nice! Subsequent test flights were made with harder and harder throws. Even though I had a fairly noticeable headwind, from a standing toss I was able to get 200 feet of gliding distance out of it, into the wind. Because the flights were of decent duration, I was able to check out control responsiveness, and felt comfortable with the settings as recommended.

 

Back to the Shop

Now it was time for the really fun part of this project, the Electric Conversion! I found the supplemental instructions for the E-conversion much more detailed than the glider instructions. (No discredit intended towards the glider instructions, not much is really needed). The electric conversion instructions walk you through the modifications required to the fuselage, how to mount the motor, route the wires, where to put the speed control, and where to put the battery pack. The most difficult part was cutting the wire tunnel through the back of the fuselage into the servo compartment, and that wasn’t even all that bad. I twisted and pushed a 1/16" music wire through the foam while the wire was cold. This allowed me to do it slowly and accurately, and I had time to check and see if I was "aiming" it properly. The music wire came through about where expected. I heated up the part of the music wire that was still hanging out the rear of the fuselage. Then I grabbed the cold end of the wire in the servo compartment and pulled the hot end of the wire through the fuselage slowly. The end result was a wire channel about 1/8" to 3/16" in diameter. I performed a couple more heat and pull cycles and made the channel a little larger until the motor leads would fish through easily. This is a much simpler and more accurate method for creating channels than just plunging a heated wire through the foam.

I mounted the motor to the tail nacelle, pushed on one of the props, and proceeded to mount the nacelle to the fuselage. (Picture shows a different prop configuration than provided for the review, more on that later)

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I soldered my speed control outputs to the motor leads, which had come already soldered to the motor in reverse polarity so the motor would spin the right direction. I placed the speed controller in the fuselage, then found a place for my battery.

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I found it necessary to place the pack all the way at the front of the formed cavity, and later discovered I needed nose weight to boot. Keep this in mind when you are assembling.

You’ll note from the picture that I did not make the battery cutout through the bottom of the fuselage as HobbyFlite recommends. I was willing to let things get hot for the first couple of flights, as I wasn’t quite eager to destroy the beauty of this airplane just yet! I left it untouched and just put the battery pack inside.

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I made the final hookups, and taped the fuselage halves together. Taping the fuselage together is much more important for the electric powered model, as the weights are higher and there is more force on the wings trying to pry the bottom of the fuselage apart. Don’t skimp on the tape for this step!

HobbyFlite recommends that you apply clear packaging tape to 75% of the entire airframe for strength. Because I’m doing a review of their airplane, I would have to recommend you do the same. But, it’s fair to point out I didn’t use ANY reinforcing tape and didn’t have any problems. Yes, at full speed the wings will flex a little when you pull hard on the elevator, but I felt comfortable without the tape. It seemed a shame to ruin such a pretty airplane! But to be on the safe side (and to keep myself out of trouble!) it certainly wouldn’t hurt to tape things up as they recommend. The 747 certainly wouldn’t look very pretty all scattered into tiny Styrofoam beads…

 

Ready for Takeoff

Off to my backyard yet again, the 747 loaded a little heavier this time. All up weight, including 1.75 oz nose balance weight, was 26 ounces. It launched easily, as the diameter of the fuselage makes a very comfortable hand grip. I intentionally launched without power, and it glided rather nicely. Satisfied with the glide, I gave full power. Whoa! Things got a little tricky for a second. The handling changed a little upon application of power, and it was traced down to having the motor nacelle a little out of line. I backed off power a little but kept climbing on out. It’s a very sleek airplane, and was flying well even at reduced power. I had to adjust trims somewhat to compensate for my crooked tail cone nacelle, but it was flying nicely. I set up for landing and brought it in for a very smooth landing. Big smile on my face. This was neat! I did notice I was getting servo glitches in flight and I remembered I had run the antenna the length of the fuselage back towards the nose. I was picking up interference from the long battery leads, so I opted to feed the antenna out the side, up to the rudder, and down to the stabilizer (to keep it out of the prop) and that solved all my problems.

On the second flight, I lost the push-on prop! It was a very bad time to lose power, as I was on the other side of a fence. I pulled up over the fence, but stalled it in from 6-8 feet. Right on it’s nose. Rather ticked at myself, I walked over to the 747 with its wings knocked out of their sockets. No damage! I was impressed. I could barely even detect any deformation in the nose. HobbyFlite markets the foam they use in the 747 as "rubberized" and it indeed helped out in this crash. (More on the foam material later, see notes from a conversation with Chris Hill at the end of the column). This was the first time I had ever used one of these push-on props, and I’m not sure I had it seated fully. I put an adapter and regular prop on it for further flights.

Throughout the next couple of days, I made more and more flights. It’s a fun plane to fly, and turns extremely well for a rudder-elevator airplane. I was putting it through the paces at my house, and was seeing just how tight a turn I could make and was pleasantly surprised. I didn’t attempt any loops, but did some stall turns and some high speed passes. It really looks cool in the air, as you’d expect, but it does whine a little from having the prop so close to the control surfaces. The 747 can really get up and scoot for a plane of its size, yet it doesn’t take full throttle to keep it aloft.

 

Suggested Improvements

I give HobbyFlite a lot of credit on the 747, they did a really well thought-out job with it. And there is nothing wrong with building it in glider or electric mode exactly as they spell out in the instructions. The suggestions I make here are only intended to improve on the great job they’ve already done.

  • They provide a nice pocket for the receiver to go into, but I’d put the receiver on the same side as the servos, which go on the main fuselage side rather than the shorter mating side. It makes joining of the two sides a lot easier for final assembly.
  • Don’t run the antenna next to or parallel with motor or battery leads, even if it is several inches away. It’s tempting to do this because it keeps everything concealed, but it can create some interference problems.
  • Make sure you glue the prop on. I didn’t expect it to come off, especially since it should have been pushing itself even farther onto the motor shaft since it was a pusher configuration!

 

Things I Really Liked

  • It bounces well (as I found out!)
  • Turns very well for a rudder-elevator airplane
  • Nicely engineered with R/C in mind as a top priority
  • The heat shrink control wire joining method
  • The pre-assembled and taped control surfaces and horns
  • When the 747 is set on a smooth surface, the prop doesn’t touch the ground, it’s well protected

 

Overall, a fun plane to put together, and a fun plane to fly!

Here’s my pictures of the completed model

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But here’s what you can do with the kit if you have the time and talent! (Copyright and Courtesy of Chris Hill)

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For a neat story on the design and development of the Boeing 747, read the following excerpts from an e-mail conversation I had with Chris Hill of HobbyFlite.

 

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From: Patrick J Mattes <pat-ingrid-mattes(at)juno.com>
Subject: Chris Hill's comments
Date: Fri, 3 Sep 1999

Steve, here's what I want linked to my article (but not necessarily a text continuation of mine)

Chris Hill's response to some questions I had posed to him regarding the Boeing 747...

Hey Pat,

You say you want a little more background on the foam process... Well an engineer friend told me right from the beginning to design the plane prototype out of the material it will end up being, foam. He said some guys make them out of wood or hard plastic or clay but you never quite know what the balance will be on the final. And after you have spent close to $20,000 on tooling you don't want to go back to reshape. What usually happens is a lead weight gets added to the nose or tail to balance it. You also pray your wing attitude is correct. So I bought a big block of foam 8'x4'x3' and started carving and hot wiring and carving and hot wiring.....When I had my first prototype done, it flew like a pig (and we know how pigs fly!) But I didn't care, I was only selling the idea of making it to Boeing. After all I needed their permission because the hump on top is a trademarked item and a 747 without a hump is just a plane. They were a tough nut to crack. The lawyers went back and forth, basically on the liability issue. They had only issued a license agreement to one other 747 flying product, which was a Styrofoam glider about 15 years ago. Of course it never hurts to have a brother who has Boeing connections!

After I got the Boeing blessing and signed 3 million copies of who knows what, I was under way. Oh, and don't forget the 1 million dollar insurance policy they made me take out naming them as co-insured. Ouch! The nice part of the deal was the plans I received from Boeing. They
were the layout of the plane for scaling and came on 2 sheets of paper 4 feet wide by 17 feet long. (I didn't know they made paper that big!) So I spent the next 8 months on the final prototype. After a few tweaks at the end, the bird flew great! Next I took it to the moldmaker who casted it out of plastic. He then took that to the foundry where it was cast in aluminum and finished. The molds are extremely large and take a forklift to move them. They were taken to the molder where the planes are shot. We used a different type of Expanded PolyStyrene called R-mer. What they do is put a rubberized coating on the bead before it goes into the pre-expander and when it is blown into the mold with steam the beads expand and bond stronger than normal brittle EPS. The benefit is you can have a tighter bead (hence a better looking surface) and a stiffer plane. EPP (expanded polypropylene) is a fat bead and very rubbery (which is great for combat!). I own a Zagi - doesn't everybody?

I think I answered all your questions... Yes, I do own the molds. Boeing has been a good watchdog as well. They told me last month they sent out 6 cease and desist orders on people trying to copy without their permission.

To date I've sold a little over 1200 planes and people love to send me pictures of their planes. Some people don't even fly them, they say they just like to hang them in their office or wherever. Here are a couple of pictures that were e-mailed to me I thought you would enjoy. (Included in my review - Pat)

Chris

 

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Old Feb 13, 2008, 10:22 PM
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CANADA,CALGARY
Joined Feb 2008
14 Posts
that is so hot plane
haresh747 is offline Find More Posts by haresh747
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