I have held off on starting a build log until I was sure that I could make this work. I have a tendency to allow my dreams to exceed my logistics. Given that this build will be opening some new doors for me in terms of modelling techniques, I decided to do a mock-up of the fuselage to make sure I could make this work before posting anything.

The plan for this build is to use enlarged card-model plans (thank heavens the original plans are vector and not raster drawings!) coupled with a pair of 90mm EDF units running on 8s packs. The outboard nacelles will carry dummy fans that will not be powered (big weight savings there!) I know that is kind of cheating, but it's the only way I can make it work. I have estimated the cost of the project at around $1,000, and weigh between 14 and 15 pounds AUW. I think I can have it ready to maiden within 60-90 days. (I know that sounds pretty ambitious, but I think this build will be pretty straightforward, and with my Dad working on it with me, it seems reasonable.) I plan to debut the model at SEFF 2013. (I always build something special for SEFF!) I have been using the past couple of weeks to do the planning and testing covering/reinforcing methods.

Here are the basic specs for the plane:
Span: 2.925 meters (115")
Length: 3.185 meters (125")
Estimated AUW: 6.35-6.80kg (14-15 pounds)
Powerplant: 2 turnigy 90mm alloy EDF units
Battery: (4) 4s1p 4500mah nano-tech LiPo packs connected in series, (1) 2s1p 3000mah LiFe pack for receiver and servos
Retracts: 1 set of e-flite 25-46 electric tricycle retracts plus one additional set of 25-46 electric main gear
Radio Gear: (2) 9 channel JR receivers, servos, wiring, etc. (I'm still working out which servos to put where)

I still have to build two more mock up pieces at the final size so that I can finalize the placement of the landing gear and flap actuators. As soon as those details are worked out, the rest should be a piece of cake. I will be posting as many pictures as I can as often as I can to prevent this build log from being another "what happened to that plane you were building?" deals. I am also interested in hearing opinions, suggestions, and any other constructive criticism from anybody who wants to share.

In the meantime, to prove that I am not just talking about this, I'm going to go ahead and post the pictures of the test fuselage that was sized for the 70mm fans.

Jeez,
Looking amazing to say the least
Subbed for sure x10

KFC. . .your 747 is AMAZING!. . .& I LOVE your Chicken too. . .. lol

Originally Posted by demondriver

KFC. . .your 747 is AMAZING!. . .& I LOVE your Chicken too. . .. lol

Thanks, DD!

Lol, the 'KFC' handle was hung on me by the HodgeHounds as part of my 'initiation'. Depending on the time of day and who is using it, it has different interpretations. During the day, it's Kentucky Flying Chris, in the evening when the jar is being passed around, it's Kentucky Fried Chris, if it's the SEFF staff, it means Kentucky Chris!

Definitely subbed

Amazing... I hope you keep updating!
Peter

Awesome project KFC!!! The card model construction is probably going to make this the lightest large scale RC 747 out there! I am looking forward to more

Ethan

These beautiful B747 builds popping up are making me to do my B747SP with these guys!.

KFC you also captured the fuselage's profile really well specially section 41 and how hump blends into rest of the middle fuselage, excellento mate......why not power it with all 4 edfs instead of two, with the wing area and low to medium wing loading you will have, adding 2 more edfs will fly it in scale manner and will weight accordingly....

Thanks for the input, fellas! I have decided to go ahead and strap the wings and tail feathers on the 70mm prototype model so I can use it to test my best guess CG. I'm going to install the horizontal and vertical stabs tomorrow, along with a pair of servos for elevator control and then get my dad to chuck it off the deck over the weekend. With a little luck, she'll tell me what I need to know.

I have found this construction to be surprisingly strong, despite being very light. I would estimate the current weight of the entire airframe as it is now at a little under 3 pounds. Hopefully we won't have to add much to that figure when we build the 90mm version. In the meantime, I have some additional pictures of tonight's progress to share before calling it a night.

Excellent excellent work.. did you hotwire the rings oversized to take account further sanding down of the contours? If you bent the rings from flat sheets of foam, I'll be damned thats really clean work..

Originally Posted by Concordefan

These beautiful B747 builds popping up are making me to do my B747SP with these guys!.

KFC you also captured the fuselage's profile really well specially section 41 and how hump blends into rest of the middle fuselage, excellento mate......why not power it with all 4 edfs instead of two, with the wing area and low to medium wing loading you will have, adding 2 more edfs will fly it in scale manner and will weight accordingly....

If the specs for the fans are anywhere near accurate, 2 fan units will give me more than enough thrust to power this plane. Using only the inboard nacelles for power reduces the amount of structural reinforcement needed in the outboard section of the wing. It makes the whole build lighter and less expensive without any real penalty. I will still have a pair of edf units in the outboard nacelles, they will just be unpowered.

Originally Posted by depronair

Excellent excellent work.. did you hotwire the rings oversized to take account further sanding down of the contours? If you bent the rings from flat sheets of foam, I'll be damned thats really clean work..

This was all bent from flat sheets of 1/4" fan fold by hand with a piece of 1/2" pvc pipe. You can't tell very easily because of the distance of the plane from the camera, but a number of the bends were less than perfect. I basically threw the whole thing together in a few days to see if I could build a plane this way. Now that I know the technique works, I will fabricate a dedicated foam bending rig that will let me match the curves of the different sections together better, so I won't have to do so much sanding afterward.

Becareful not to forget adding washout on the wing tips, I think 2-3 degrees will be perfect for your model. Rest it coming along nice and for the size of it, man less then 3lbs is pretty much weightless!.....

Originally Posted by Concordefan

Becareful not to forget adding washout on the wing tips, I think 2-3 degrees will be perfect for your model. Rest it coming along nice and for the size of it, man less then 3lbs is pretty much weightless!.....

I figured some washout would be necessary, but I wasn't sure how much. Thanks for the suggestion, ConcordeFan! Just for the record, though, when I weighed the plane as pictured in my previous post this morning, the total came to 1 pound 14.5 ounces, so it's actually lighter than I thought it was!

This build has surprised me in a number of ways, and I think it could be built even bigger than we are planning (not that I am going to do that, our current size is dictated by transportation considerations; at 10.5 feet long, this one will just barely fit in the trailer). I would have to say that based on what I am seeing from the prototype, it would not be impossible to scale this up to approximately 1:17 (That would be sized for 120mm fans)

Just got word that my fans and ESCs have shipped, so I should see those within the next 10 days or so. For reference, this is what I ordered:
90mm alloy fan unit
Turnigy 120Amp HV ESC

BADASS!!!! I'm totally subscribed. Looking forward to seeing this at SEFF.

I have decided to have a little fun with this one before I start building on the big one. Since I am waiting on parts at the moment, I don't think that this will cost me any time. One way or another, it will happen over the weekend.

I dug through my spares bin and found an extra motor, speed controller, some servos, and a receiver. I'm going to go ahead and install the vertical and horizontal stabs, install a few servos, bolt on the motor, and fly the prototype this weekend. No landing gear or anything, just the bare minimum to see what happens. One way or another, it should be interesting, and I promise some video afterward.