Modifications By Ken Myers April 2018 I like the concept and goals behind Flite Test very much. The people behind Flite Test seem to be some of the nicest, most caring and sharing people that I've come across in years. In April 2018 I did a presentation at the Midwest RC Society. The presentation was called "Who and What is Flite Test?" The highlights of the presentation are here. The article describes who and what Flite Test is and what they aspire to be. Please take a few minutes to review this article and what I had to say about Flite Test. In April 2016 I built a version of their Old Fogey, but it was not exactly 'their' Old Fogey. I increased the size by a factor of 1.22 times. I ran into several problems, but they were not related to my size change. "FlightTest.com & The Old Fogey" was the first of two articles that I published about the Old Fogey. The article shares some issues I found with this plane's design. The second was "More on the Old Fogey's Old Fogies (Includes Power System Comparisons/EMAX & Cobra motors - EMAX ESC & CC Thunderbird)" and it discusses the specific modifications for my Mk II version and the differences in the system efficiency between the two power systems. In April 2018 I decided to give one of their designs another try, the FT Simple Cub. I used portions of the Flite Test videos of the Simple Cub and a printed sheet of their plans in my presentation to Midwest. I also still had four of the recommended 3S 1000mAh LiPo battery packs from when I did the series of articles called "Learning About LiPo Batteries" that started in the March 2016 Ampeer. My goal was to build the FT Simple Cub exactly as designed. Unfortunately, it didn't work out that way. I want to make it clear that I do not consider my way 'better', but it certainly is different, although the finished plane is their design by size and weight. I made no modifications to the actual airframe proportions or wing airfoil at all. Today's Flite Test plans, which can also be used as parts templates, are beautifully presented in Adobe Acrobat Reader format. They are created by Dan Sponholz for Flite Test. I downloaded both the full-size plans and the tiled plans. The plans can be downloaded from the links near the bottom of the DIY FT SIMPLE CUB | BUILD page. I spent a good deal of time and energy trying to print the plans using the Preview program on my Mac. Preview cannot be used because it won't print in the poster format that is used for the FT plans in the Adobe Acrobat Reader. Adobe Acrobat Reader DC must be used to print the Flite Test plans. It is available for the Mac as well as the Windows operating system. While trying to sort out MY printing problem, I ran across a fellow on YouTube who described a process to convert the pdf file plans back into a dxf file. A dxf can be imported into a CAD drawing program. Why on earth would you want to do that? There are actually two good reasons. 1. The parts can be rearranged to print on fewer pages with fewer seams and cut offs when printed on 8-1/5" by 11" printer paper. (I actually decreased the amount of printed pages from 60, with a lot of cuts and seaming, to 22 pages with 23 cuts and seams.) 2. Scaling can easily be accomplished, if a larger or smaller version is desired. I wrote an article on what I learned and how to do it. The article is titled "Flite Test Simple Cub Simplified Plans". The article also has the links to the pdf files that I actually used to create the Simple Cub. There is no tiling involved and even the Preview program on a Mac can print them. While preparing my presentation for Midwest, I watched various portions of the Simple Cub Build video. During these viewings I realized that at least two different versions of the Simple Cub were being built and then edited together into a single build video. I also watched the whole video to guide me through my actual build. The Build video starts with the construction of the basic 3-channel version, but it meanders back and forth between that build and the build of the 4-Channel version with the larger Power Pack C motor. At a few times this 'switching back and forth' could be confusing to someone just entering the hobby. It was to me. During my presentation to Midwest, I showed a 12 minute FT video of 5 Simple Cubs flying together. I used it to demonstrate the excellent video quality and humor involved in their videos. The video demonstrated what I feel is a short coming of Cub-like designs. To see the short coming, view about 20 seconds of the video I showed to Midwest. The Simple Cub is certainly not supposed to be scale-like, but it shares several design elements with other Cub model designs. Over the years, many of my student pilots have chosen various Cubs to learn on. All of them have had the axles of the landing gear aligned with the leading edge of the wing. Once my students started landing their Cubs, they always flipped over. It takes a lot of finesse to land a Cub-like plane, with the axles aligned with the leading edge of the wing, without flipping it. Low time pilots lack the finesse to do it consistently and the flip can sometimes put and end to flying for the day if the vertical stabilizer is damaged too much. On several of my students' 'Cubs', when possible, we moved the landing gear forward a bit. That helped as they were not as worried about flipping the plane on landing. My ultimate goal, for my version of this plane, is to use it as a trainer with my student pilots. Based on my previous experiences with this type of plane, I decided to move the landing gear forward an arbitrary 5/8". That change meant that I was no longer building a FT Simple Cub, but the landing placement change does not change the way it will fly, only how it will land. I moved the slot for the landing gear forward on the Fuselage doubler. I also eliminated the rear slot for the optional float set up, as this 'trainer' version of the plane will never have floats on it. 
Note: This is a first draft drawing. It is NOT the same as the final version. The final version has the landing gear slot moved further forward & the angle on the top of the doubler changed. The FT Simple Cub video shown at Midwest also demonstrated an issue with battery security. View a little over 30 seconds of the video to where it crashes. The version of the Simple Cub shown in the video was 'hit' mid-air dislodging the battery, but it is still not good if battery can come out at any time. It needs to be secured with a strap as well as a strip of Velcro. I made slots for a hook 'n loop strap in the piece known as the Swappable Power Pod. There were other changes to MY modified Swappable Power Pod. The slots can be seen on MY final version of what was the Swappable Power Pod. During the Simple Cub video, Josh notes that the battery will be placed on top of the Swappable Power Pod through a hatch, but that hatch never appeared on FliteTest's final version. Watch about 10 seconds where he notes the battery sliding in from the top. I PREFER a top hatch. I just don't like turning a plane over to 'load' the power battery through the prop area. I created a top hatch using the front part of the Fuselage top and modifying the the front of the Fuselage. 
Fuselage Mods & New Top Hatch Note that in the diagram, the inside of the plane is shown. It looks like the hook 'n loop slot, under the hatch, is on the left side, but it is on the right side. The new hatch is hinged on the left side of the Fuselage with strapping tape. The hatch closure is two pieces of hook 'n loop fastener. One piece of hook 'n loop is placed on a slot in the Fuselage side on the right side and the other piece is on the hatch over the other piece of Velcro.  Back in the 'olden' days of RC we had 'swappable' onboard radio system components boxes built into our models. The expensive onboard radio systems could then be swapped between models. Later manufacturers built 'bricks' that included the electronics for the receiver and, usually, the electronics for 3 servos. The 'bricks' could be moved from plane to plane. Flite Test decided to 'run' with this idea and make the 'expensive' power system components swappable with a Swappable Power Pod. They created a whole series of airframes around this concept. In theory, that's a pretty clever idea. In practice it does complicate things a little, especially in the build of the Simple Cub. Flite Test has a build video for the Swappable Power Pod. Watch about 10 seconds of the video and note the alignment of the firewall on the Power Pod. Watch about 5 seconds of this Power Pod build for the Simple Cub Unfortunately, the whole process of fitting the Firewall and Power Pod became a conundrum for ME. The Simple Cub has no decalage, or difference in the datum line angle between the wing and horizontal stabilizer. Both the wing and horizontal stabilizer are horizontal to the datum line. When the Doublers are glued to the Fuselage sides, the tops of the Doublers are at a 2.30 down angle from the datum line. That could provide the down thrust angle.  The Fuselage sides and the Fuselage Doublers have alignment marks on them that indicate where the holes go to put the BBQ skewers through to hold in the Power Pod.  This diagram shows the side view of the Power Pod, shown in red, sitting on top of the Doublers. The alignment of the holes at the front and rear of the Power Pod line up very well. The middle alignment mark is not used.  When the 3/32" Firewall is added and aligned so that the DTFB thickness is protruding above the top, as noted in the video, the holes in the Fuselage side and Doublers no longer align. The thrust angle is changed to 20 and the front part of the Power Pod 'floor' is sitting above the Doubler 'rails'. 
https://youtu.be/Uw0_9Zmcewc?t=79 The frame grab, from the Simple Cub build video, shows that the top of the Firewall should be 'under' the front, top Fuselage piece, which has a thickness of the DTFB.  The diagram shows the thickness of a piece of DTFB using a blue line. Placing the front, top piece on top of the firewall would cause the front top piece to 'rise'. That rise is not shown in the photo. MY problem is that I am way to analytical when building someone else's design! It is not a problem for a low time builder of the FT Simple Cub design. Why? Watch about 10 seconds of the video. The BBQ skewers are used to make the actual hole through the Fuselage sides and Power Pod. The low time builder might figure that the reason the front Fuselage top piece is not flush is because they made a building mistake. Whether it fits 'correctly' or not will not affect the way the plane flies! A reader might ask, "If it makes no practical difference, why did you explain the Power Pod issue?" 1. To point out that the way the Power Pod is used in this plane is NOT the way the Power Pod was originally designed, and that it might not be all that 'swappable' with other swappable designs. 2. I was not planning on making the Power Pod swappable. I wanted to know the angle for the the Firewall. Unfortunately, I had not fully analyzed the Power Pod and its effect on the down thurst, and chose to set MY firewall perpendicular to the line created by the top of the Doublers. MY version has 2.30 of down thrust. That is another change from the FT design, albeit unintended. I did change the height on MY firewall so that it fits 'just' under the hatch. Flite Test suggests using screws to keep the motor attached to the firewall. Sixty plus years ago, I built control line, and later RC models, that used the Cox 0.49 engine screwed onto a plywood firewall. Experience over the years showed that it was not be the best solution for keeping the engine on the firewall. I found bolts with blind nuts to be a better solution. Blind nuts, even for small bolts, require a greater firewall thickness than 3/32" to seat. I changed the firewall to 3/16" thick plywood and modified MY final Power Pod accordingly. A 1/8" thick firewall was used on the final version. Using bolts and blind nuts also goes against Flite Test's philosophy of keeping things as cheap as possible. A set of four small bolts and blind nuts definitely costs more than four little wood screws and they are also harder to come by. The FT plans don't show a hole on the bottom of the Swappable Power Pod to access the power leads from the electronic speed control (ESC). The battery on the FT Simple Cub is positioned on the bottom side of the Power Pod floor and the ESC on the top side of the Power Pod floor. That really isn't a big deal, as the floor is DTFB and it is to cut a hole through it. For MY version, the ESC is mounted on the bottom of the DTFB 'Pod' and the battery on the top of the DTFB. The battery area is accessible by the hatch I added.  Because of these changes, the Swappable Power Pod can no longer be used as swappable. Safety Note: Josh inserted the Swappable Power Pod with the prop on the motor. The prop should be off until the plane is ready to be balanced to check the center of gravity (CG) and the battery NOT hooked up.
Flite Test keeps the power selection simple by recommending an inexpensive motor/battery/ESC/prop combination. That makes it really nice for a beginner.  The Power Pack B (Fixed Wing Small) is recommended for the Simple Cub. The motor in Power Pack B is the Emax MT2213-935KV 53g 935Kv outrunner. The ESC is a BL-Heli 20 amp (with XT60 connector). The Power Pack contains two propellers of the slow fly type; a 9x4.5 and 10x4.5. The recommended battery for the Simple Cub is the Lumenier 1000mAh 3s 35c Lipo Battery. The recommended propeller for the Simple Cub is the HQ Prop 8x4.5 CCW Propeller Slow Flyer, which is not included in Power Pack B.
At the beginning of the video, Josh Bixler states, "Now in this video we are going to be showing you how to build the basic 3-channel."
That makes the power system selection extremely easy. Or does it? Watch for 20 seconds. In the video, Josh said, "The motor we are going to be puttin' on is the 2215/09 and that's our C Pack. That's for our Warbirds and bigger aircraft and our ah more experienced fliers. If you are flying something smaller, that takes a full-size swappable, you're probably going to be referred to a B Pack. In all of our airplanes, that we design, we refer to the best power pack that we recommend on every single one. So there won't be any confusion." Power Pack C (Fixed Wing Large) This power pack is not longer available with the Emax motor. It now contains a FliteTest branded motor.
There is a difference in the motor weights in the two Packs. The difference in weight will affect the battery placement to obtain the correct center of gravity (CG). This does seem a bit confusing, especially for a beginner in the hobby. I chose to use a Cobra C2213/26 as it had the closest specifications to the motor in the Power Pack B; 61g and a Kv of 950. While more expensive than the Emax, Cobra motors are MY motor of choice. There is only an 8g difference in weight, so the effect on the CG is minimal. I also chose a Cobra 22A ESC with 2A Linear BEC. The final version uses the Cobra 33A ESC with a switching BEC. My power system selection, including the 3S 1000mAh LiPo battery, IS equivalent to what is recommended by Flite Test. While watching the pushrod installation on the build video for the Simple Cub I noticed the extremely small diameter wire used for the pushrod. I also noticed how flexible it was and wondered if that might be a problem. Watch about 15 second of the video and note how easily the pushrod bends. I wondered if this was going to be a problem. I searched the Flite Test Forum and other sources for comments about the pushrods. 1. Shakeyjake, "After I crashed my Simple Cub several times I finally figured out that the rudder and elevator control rods were flexing so bad that in the right conditions the rudder would go slightly left even when I was full rudder right..."
2. Brett_N , "I second the better control rods. I'm only using the small gauge on the mini's and even then I zip tie them. They're OK for aeilerons on the bigger planes, but no good for anything requiring more than about 6 inches of length."
3. NATHANAEL 13th Aug 2017, "They bend
The final version uses Hitec HS-53 servos mounted in the rear, outside of the fuselage, NOT the pushrods shown in this diagram I chose to use a very, very old pushrod method for MY Simple Cub. It uses commercial pushrods with threads on the end for nylon clevises, a length of 1/4" square balsa wood, and 1/16" wire on the other end to go through the small holes in the small servo arms. Sewing thread is wrapped around the rods at each end of the balsa wood and then the thread and rod are glued. (The threads are not shown in the illustration.) I noticed that on the Flite Test Store page for the FT Simple Cub and on the downloadable plans, the recommended throw on the movable control surfaces is 120. There is a throw gauge provided on the plans and in the laser cut kit for this plane. Watch about 10 seconds of the video The part of the build video linked to above shows Josh using the Throw Gauge. By the angle on the Throw Gauge they way that he is using it, it looks like he is setting the high rate. The problem is that both of the angles on the Throw Gauge are too steep to provide a gauge for settung the deflection angle to 120.  For MY Simple Cub I made a 120 throw gauge to check my throws. The plywood control horns, drawn on the plans and provided in the kit, are too short to provide only 120 of throw with other end of the pushrod connected to the inner most hole of the servo arm. Of course the throw can be adjusted with a computer radio, but I chose to use the commercially available Great Planes Nylon Control Horns Large.
Watch about 1 minute & 20 seconds of this video I installed the servos using the method described in the video. I used the Flite Test recommended hot melt glue gun and hot melt glue that I had purchased directly from Flite Test. While MY Simple Cub was being passed around at the April 2018 EFO meeting, the rudder servo fell off the side of the fuselage. Before doing the servo installation, I had my suspicions about the integrity of this type of installation, but I thought I just had to give it a try to be fair to Flite Test. I searched the Flite Test Forum and found a comment where a servo let go during the maiden flight. SPONZ, "About a minute or two into the flight, the elevator servo let loose inside the fuselage and I had no pitch control. Down she went."
There is a little irony in who it happened to. SPONZ is Dan Sponholz, the guy that creates the beautiful plans for Flite Test.  I made some 3/16" plywood servo rails that crossed through the fuselage sides and secured the Hitec HS-53 servos to them with screws. The video shows how to check the center of gravity. Watch about 20 seconds of the video. Once the plane was completed, I placed a GensAce 3S 1000mAh in the battery compartment as far forward as possible, as shown in the video, to check the center of gravity (CG). With the battery at that point, the plane was extremely nose heavy. I moved the battery as far to the rear as I could to still be able to get it in and out of the hatch. It was still much more nose heavy than shown in the video. To add some tail weight, I used some plywood and a piece of 1/8" music wire. Gluing it on the rear of the fuselage was easy, as I'd forgotten to add the skewer tail skid to the bottom of the rudder. That add 0.4 oz. to the tail. The balance was getting closer to the suggested CG, so I decided to fly it that way. I have no idea why MY version ended up so nose heavy. Hindsight: I should have made my Doubler with both slots for the landing gear since the gear tab is just a friction fit in and it could then be flown with the gear in both positions.
Finished (almost) Specs for my plane Plan Form Wing Area: 293 sq.in. FT said 302 sq.in.
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