FTFMM Challenge - "Fat Albert" C-130 by DamoRC

[DamoRC]

Introduction
This is my entry for the Flite Test Community March Madness Challenge (FTCMM). The goal of the challenge is to encourage designers and builders to finish designs and builds that they dropped or abandoned.

Update 23rd April, 2018 - Plans Added.
The attached file (at the bottom of the post) contains the following:
Tiled and Full PDF plans
Sketchup, DoubleCAD, and exported .DXF files.
PDF with the Fat Albert decals.


Background
This project started when a guy at our field, who knew I like to design and build planes, showed up with the remnants of a 250 size quad. It was basically a frame with four motors, four props, and four ESCs, and he asked if I could build a C-130 using the electronics from the quad. Although I had never thought about this plane as a build project, we soon agreed on some basic specifications for the build. Because he keeps his planes in his truck he wanted to keep the wingspan as short as possible. He had some wheels that I could use and we decided on including a steerable nose. Most importantly, he requested that the plane be painted as Fat Albert. For those of you who don’t know (and I didn’t before this build), Fat Albert is the C-130 used by the Blue Angels flight team as a cargo hauler and it also performs at the shows, demonstrating its Jet Assisted Take Off (JATO) capabilities.


The real Fat Albert in flight

The original plane flew well enough on her maiden but she had some nasty tendencies that made her drop like a rock on high bank turns. You can enjoy my walk of shame in this vid.

It seemed to be either a tip stall or general wing stall issue. I made some adjustments to the wing, thought I had her sorted, and painted her up.


Ah, she was pretty in those days

Again, she flew pretty well, but the modified wing still wasn’t up to the job and we suffered more crashes and/or really rough landings.

The second wing version was a little better but still needed to bring her in hot for landings or she would cartwheel.

Third time was a charm and the current wing works great. Here she is playing in the wind with a friendly Guinea

By this time the rest of the plane had taken a battering. The nose (the second) was totally wrecked, the tailfeathers had taken a beating on some cartwheel landings, and the fuse was beginning to disintegrate.


Looking and feeling a bit tired

I had put a reasonable amount of work into the plane at this stage and I really didn’t want to rebuild her. I knew there was some design changes that needed to be made and it had become one of those builds where I didn’t have the motivation to finish. I just wanted to fly what was left until it was dead. Of course, this meant my friend didn’t have the plane I promised him, and he has been quite patient.
So time to get back into the saddle, as it were, and get this job done.

Goals for the build.
In addition to meeting the requirements for the challenge, I want to re-work or fix the following items and as I complete them I will update the text below.

Fuse
(1) Add strength to the joints between fuse sections. The simple butt joint with hot glue approach works but it doesn’t last. Update 06Mar18: Designed a simple 12 sided insert to create a lip between the center and tail fuse sections. This should provide enough additional strength
(2) Test the possibility of using a 10 or 12 sided fuse (current version is 8 sided) to make the fuse more round without giving up too much strength while keeping the hollow tube build approach. [Update 02Mar18: Oops, the current model is already 12 sided (just shows how long since I looked at it carefully), so consider this done!]
(3) Add a cargo bay door (which will require more fuse strengthening). This will be a simply one piece door and not the two piece found on the full scale plane (or on really, really good models like this one...)Update 06Mar18: Cut a cargo door out of the mule which is approx 6 inches long and 3 wide. Thankfully the rear fuse section is strong an there was no notable impact on the structural integrity (gotta love gorilla glue!).
(4) Strengthen the wing mounts
(5) Design in the wheels as opposed to hacking them in as I did on the originalUpdate 09Mar18: Done - originally I had set the ground clearance too low in comparison to scale. The newer version might be a little high, but will negate the need to hack into the fuse for clearance (I hope!)

Tail Feathers
(1) Strengthen both the vertical and horizontal stabilizers, possibly using a double layer of foamboard [Update 02Mar18: Having checked again, looks like the VStab is solid. The Hstab only has issues at the tips, beyond where the wooden spar reinforcement ends, so the solution is a longer spar - no need to double up on the foamboard
(2) Do a neater job on the servos Update 09Mar18: Decided to mount the servos for the tailfeather a little further forward so that they are serviceable when the cargo door is open

Wing
(1) Make the nacelles a little smaller or more streamlined in shape Update 03Mar18: Nacelle design updated to be a little smaller and narrower. Closer to scale but not quite due to the constraints of fitting the motor.
(2) Increase the aileron area significantly (they are tiny on the current wing version and roll authority is not great). Update 20Mar18: Done
(3) Do a cleaner wiring job for the servos and motors and make the two-part wing assembly and associated wiring neater.Update 02Apr18: Done - totally re-worked the wiring to pull the ESCs into the fuse as opposed to living in the nacelles (which are smaller now and would make removing the motor and ESC really difficult

Specifications

Wingspan: 50 inches
Length: ~37 inches (depending on how battered the nose is)
Power: 4 x SunnySky x2204S-16 2300Kv motors wearing 5030 props and driven by 10A noname ESCs
All Up Weight: 34 ounces with a 2200mAh, 3S battery

DamoRC

 

[DamoRC]

Design Updates

Starting Point (or re-starting point)

This is a picture of the model in Sketchup as it was when I dropped the ball. The design / build approach is the same as that of the Reichenberg and Ohka, reflecting my current addiction to Gorilla Glue and hollow fuselages.



Nacelle Update

I updated the nacelles to make them leaner and a little more scale. Toyed with the idea of installing the motor inside the nacelle using a similar approach as the FT-mini motor mount but this would have made the motors unserviceable. I test built a couple of versions and mounted to the current wing. Settled on the smaller of the two as it is easier to build.


Cargo Door Update

I cut a cargo door from the mule. It is ~6 inches long and ~3 inches wide. The good news is that the rear fuse section integrity was not affected by cutting this chunk out. I will need to think about the hinge and drive for this door. As pictured, I installed a simple tape hinge. This seems to be fine except if I drive the opening and closing of this door with a single servo mounted on one side, I am pretty sure this hinge will twist and the door will not close flush. I may need to get a proper plastic hinge for this.



Fuse Section Connector The fuse mid and tail sections were originally joined with a simple butt joint and hot glue. This works well but after a number of crashes this joint began to suffer. I modeled a 12 sided insert to slide between the two parts which would provide some reinforcement to the joint. In the pics, this is quite a long insert which works for the center fuse, but not for the tail which is highly angled. In its final form it will really just be a lip of 1/4 - 1/2 inch foam protruding into the tail.



Tail Feathers Update

Made a couple of changes in the Sketchup model. These included a small extension of the rear of the fuse to provide better support for the tail and to allow the vertical stabilizer to insert through the horizontal stabilizer and into the fuse tail for support. Also worked in the various tabs and slots for alignment.




Wheels Update

So I hacked out a chunk of the wheel arches to start measuring up the wheels and space inside.



Then I modeled the wheels into Sketchup. This is how the model looked before...



...and this is how it looks after.

.

I removed a panel from the outside of the arch, and added a plate to the bottom of the fuse to support the wheel axles. The plate looks terrible in the model, but during the build it will be beveled and painted so I think it will be fine. Also, I can now rest the wheel arches on this plate for better fitment and strength, not only for the arches, but also for the bottom of the fuse in general.

Then I modeled in the nose wheel lines and mount. This will be a full paint stirrer running back from the wheel into the center section of the fuse (with a second layer of foam underneath). It will also serve as the battery mount.



Decals

So I am hoping to add detail to the plane using homemade decals. This is the v-stab insignia.




DamoRC

 

[DamoRC]

The Build

Printing and Part Making

Printed the tiled plans an assembled into the plans for individual parts. Not much detail here, just cut according to the plans, score where indicated, slightly widen the scores to allow the pieces to bend a little easier. Frames (squarish pieces with dodecagon holes cut out) were cut fresh for this build. They are needed to hold the shape of the fuse and nose parts while the gorilla glue dries.



Building the Nose

This is the same process as I have described for a few builds. Open up the score cuts and apply a thin "shmear" of gorilla glue. Then fold the piece over and hot glue the seam. Then install the piece into its frame so that it will hold its shape while the GG sets. In this case, I decided to assemble the pieces while the GG was setting and only used one frame (to make sure that it would eventually mate with the fuse properly).



Strengthening the Tail Feathers

The usual approach whereby you make a trench across the span of the piece and glue in a wooden spar. For this I used a strip cut from a cheapo wooden yardstick so I could span most of the width of the horzontal stabilizer. I also started mapping out how the control rod for the dual elevators would fit.



Building the Fuse

Before folding and gluing the parts, I pre-installed the rudder and elevator servos. The rudder servo is installed into a cavity removed from the part. The elevator servo is just glued to the foamboard without a cavity.



Now folding and assembling the fuse sections. The same process as before, a "shmear" of GG into the score cuts, fold, hot glue the seam and install the frames. I also assembled and installed the re-enforcers at either end of the main section of the fuse. These pieces were assembled in the same manner as the fuse piece and then used GG to fix them into position.



Assembled the tail cone and also attached the tail cone to the main fuse section.



When the GG was dry I test fit the nose (which will also double as a hatch, held in place with magnets).



Fuse do-over

Keen observers may have noticed that in the original fuse build I attached the tail cone to the wrong end (you can tell by where I have the wing cut-outs). This in itself is not a huge deal as I had not cut the wing slot. However, closer examination of the fuse confirmed that I had made an error in cutting the nose cone and, although I could probably work with it, I decided to scrap the fuse and tail cone and re-build them. To get the nose to fit on easily (this will be the hatch) I used an iron to bevel the re-enforcing ring .


And this is the final (really final) fuse with tail cone attached and nose sitting on.



To complete the nose I will need to "carve" some foam so I prepared a stack of foam board pieces, laminated with Gorilla Glue for later.



Nacelles

Time to fold and glue the nacelles using the now familiar approach of adding a "shmear" of GG to the score cuts and using hot glue to join the bases. Once these are dry I will use them to cut the templates for the firewalls (each is a tad different in shape).



When the nacelles were dry I used them to trace firewalls on 1/8th ply. The cut firewalls were glued to the nacelles. In the background are the 4 motors wearing new motor leads which will run through the wing to the fuse.



Wiring

I basically re-did the wiring from scratch. This time the ESCs will live in the fuse. The ESCs came with really annoyingly tiny bullet connectors (maybe 1mm) and a couple had broken through development of the protoype. So I removed all of the heat shrink and tested each one, re-soldered if necessary, and added new heat shrink. I then fixed all of the control lines, and re-made the power loom. The final loom looks reasonably well organized.



Wing

I didn't get many pics of the wing build but it is essentially an FT type wing. Here you can see the top and bottom surface and the slots that will align and hold the nacelles in place.



Then it was time to cut out the wing mounting. Unfortunately the folded wing profile and the plans for the cut out did not align as well as I had hoped (or as well as the first build) and there is a gap at the LE of the wing. I will fill this later.



Tail Feather Preparation

There is a lot going on at the tail end. I moved away from the idea of using a torsion bar approach to the elevator and went instead with a simple bent control rod that loops aroung the servo arm out to both elevator surfaces. To access the servo I cut out the cargo door. Thankfully the tail cone retains its strength and stiffness even with this large chunk cut out. Also got to dry fit the tailfeathers.



More Wing Work

As the wing sits into the fuse the rear portion of the cutout lifts up so that the wing can be screwed in. This "flap" was cut and sanded so that it fit snug on the wing. There will also be magnets installed in the flap and the wing to hold the flap down during flight.



A piece of 1/8th ply is glued in across the back of the wing cutout. Two additional pieces are glued onto the underside of the wing trailing edge. Two screws will fix the wing onto the ply mount on the fuse.



In this version I wanted to re-enforce the front of the wing mount. In the original mule version various "rough" landings (like nose-in type landings) led to this section of the fuse getting a beating.



Cut three pieces of foam that would fit inside the fuse and butt up against the leading edge of the wing to share the impact load. The three were hot glued together and installed up against the leading edge of the wing.



Wheels and Wheel Arches

In the original mule version the wheel axles were hacked into the fuse. In this version there is a mounting plate to which the axles are attached. It is re-enforced with some wood strips and then mounted to the bottom of the fuse. This is a stronger stiffer wheel mount than the original.



I then started prepping the wheel arches for install. The first one was a pain because I had to put it in and out of position repeatedly to try and get the bevels right as well as the fit to the wheel mounting plate. Ultimately there is a flaw in the design of the rear of the wheel arch as it simply would not fold over the fuse so I had to remove a piece. When it was ready for its final install I added gorilla glue to the score cuts and then hot glued it in place, folding it while it was installed. After installation I thought I would try spackle to fill the gaps - lets see how this goes as I have never used this approach before.



At this point I have too many attachments in this post so I will continue the build in post #4

DamoRC

 

[DamoRC]

Continuation of the build

More work on the nose

So my gorilla glue laminated stack was dry so I thought I would finish the nose. The stack was rough cut to get rid of a lot of excess. A small plate was added to the nose cone to provide more surface area for the stack to be mounted. Then the cutting and shaping started. At one point it looked more like a beak than a nose. At some point you have to tell yourself to stop sanding as any attempt to improve the shape will undoubtedly mean you will take off too much material. I am pretty happy with where I stopped.



On the final straight now so moving back and forth from one part to the next.

Finishing the Wing and Nacelles

Now that the ply mounts are fully dried I installed the front posts for holding the leading edge into the fuse. The posts are old plastic rods (that you get with some soldering irons). They were glued in place and taped for a little extra strength. Matching holes to receive the posts were added to the foam inserts. I also drilled two holes in the ply installed at the trailing edge. Now the wing fits in nice an snug and is well secured with the posts up front and the screws at the back.



Because I had made up as set of four motor mounting plates for the original build, I decided not to spend the time to cut new ones for this build. Using the old mounts meant that a little sanding of the corners was needed. With all four motors mounted on the nacelles and the wiring passed through the wing, the nacelles were mounted onto the wing. Once the nacelles were on, the wiring was tidied up (a little) by mounting the ESC's onto the underside of the wing (FETs out).



Tail Feather Install

Pretty straightforward FT style.



Nose Wheel

A paint stir stick was glued in place with an overhang at the front to mount the wheel. The stir stick serves double duty as the battery tray. The nose wheel was re-build from scratch from the original. Using the barrel of a pen, a couple of washers, some modified linkage stoppers, the nose wheel and axle was fabricated and installed with not too much drama (there was a little drama when I discovered that the original placement of the nose wheel servo did not work as intended, the wheel turned in the opposite direction to the rudder - this happened because I moved the rudder servo to the other side of the plane and now the two were not "in sync" with respect to turning direction. Mounting the servo on the other side of the fuse sorted this out. Finally a hole was cut in the base of the nose cone for the nose wheel.



At this point the plane was ready to maiden and it went pretty well.

Cargo Door

The cargo door ended up being a simple setup. I did try mounting the servo on the side wall, but could not get the throws I wanted and was creating a twist in the door as it closed because I was only using a tape hinge. Eventually a simple floor mounted servo with a plastic hinge did the trick. The hinge was a scrap piece of plastic that I folded back and forth repeatedly (the way you do when you are trying to break a piece off). When the fold was sufficiently pliable, I mounted it onto the plane. Now the door works pretty well and there is no twisting when it is closing.



Paint Job

The following pics show the various stages in the paint job. Only difference between this and the original build is that I included the thin blue line that runs along the top of the yellow band.



I'm pretty happy with the final results.





DamoRC

 

[foamtest]

I can't wait to see how this turns out!

 

[DamoRC]

I can't wait to see how this turns out!

Thanks.

First post completed with background etc.

DamoRC

 

[PsyBorg]

Wow that's a nice progression. The final version when all painted up will look incredible in the air. Seemed like it flew nicely through most of the videos. Good job on this one. Post a link to the actual angels once you have the final version built. I think that would get some serious likes and maybe some attention for ya. :applause:

 

[Jaxx]

I love this plane! Great work.

 

[RMDC]

The first one looked so nice in the air in that last video; I can't wait to see what comes out of the new approach.

 

[DamoRC]

Thanks Guys! Updated the design post with the new nacelle. Still not scale but smaller and sleeker than my original attempt. I test build and fitted two versions and will be going with the one on the right. The original nacelle is the one on the left.



DamoRC

 

[thenated0g]

looks amazing man, keep it going.

 

[DamoRC]

Thanks Nate!

Quick update to the design post covering the cargo door and tailfeather upgrades / mods. Should be ready to finalize design changes this week and also start the re-build on parts that will not be changing.

DamoRC

 

[FoamyDM]

Great update.

How about reinforcing the upper section only in the tail feather section. I suppose it won't help a hard tail landing, but it it would help a hard-down landing from having weight inertia of the tails breaking the butt-joint.

 

[JimCR120]

Looking very good. Keep up the great work!

 

[DamoRC]

Thanks Guys!

Great update.

How about reinforcing the upper section only in the tail feather section. I suppose it won't help a hard tail landing, but it it would help a hard-down landing from having weight inertia of the tails breaking the butt-joint.

Yep - I was thinking about that - like a b-folded spar that runs across the roof between the sections? This would definitely help on the hard landings.

What I like about the insert approach is that I can also use it to strengthen the center fuse shape, like a double foamboard layer. One thing I have noticed is that this center fuse section has taken a beating because it holds the wing at the top and the landing gear at the bottom.

DamoRC

 

[DamoRC]

Quick update. Finished updates on the wheels and started playing with some decal options for decoration.

Almost there on the design side...



Anyone ever used a decal making service for their planes? I can make up my own but using regular clear tape to attach them (even when carefully cut along the outline) always leaves a cheapish finish.

DamoRC

 

[Crazy Goats]

Nice work! The C130 is so beautiful IMHO.

 

[DamoRC]

Nice work! The C130 is so beautiful IMHO.

Thanks! I agree. If I was building this for me, I would go with the plain gray scheme - I think that best represents the model. Have been thinking of building a bigger version in gray.

DamoRC

 

[DamoRC]

Finally got back to this.

Updated build post.

Printed plans, assembled the parts drawings and cut most of the parts (just the wings to do). Will start assembly of this pile tomorrow night.



DamoRC

 

[FoamyDM]

What is it about a pile of Plane parts that's so appealing?

Nice Progress DamoRC.