8. Super Knockabout Kit Build Log – DLE 30cc Gasoline Engine (Updated 7/15/2016 – Four Year Flight Report)

A note about this blog page. For this build I’m using the WordPress iPad app. So far it’s been really easy to use and a real time saver. The best feature is the ability to take a picture with the iPad and insert it right into the page. No more transferring then uploading then inserting.

11/22/2011 – Kit has been sent to the laser cutter and should be ready ~mid December.

12/23/2011 – Picked up the kit today! Just a “Big Box-O-Sticks”. Build starts soon.

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Here is the designers flying prototype for a little inspiration. Jim outfitted this one with an OS 1.60. I sure was inspired when I saw just how big and beautiful she is.

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12/29/2011 – And it begins.

The kit is full of laser cut pieces and lots of balsa sticks. A nicely detailed instruction manual is included on CD and in my estimation covers around 80% of the build process leaving around 20% to your own experience. A parts finder is included to help identify the cut parts, and keeping things organized is key to a smooth build.

Jim did a thorough QA check before delivery so everything was in good shape and ready to go. I gathered up my building supplies, made sure the building board was level and began the first step, the horizontal and vertical stabs.

First order of business is the horizontal stab.

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Horizontal stab laid out.

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1/1/2012 – Finished the rough stab build. Just need to shape and sand to final dimensions. Try to cut the angles as cleanly as you can to eliminate gaps at the joints.

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Started on the wings. First steps are building up sub-assemblies before laying out the wing panel.

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The spar caps and the leading and trailing edges have been marked for rib locations using the marking guide on the plans. The spar caps needed to be assembled with some tapering required for the doubler.

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Other wing sub-assemblies going together. Wing tube stops, servo mounts and rib doublers.

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Keep plenty of small light pressure, various length clamps on hand. They are inexpensive and having extra ones keep the build process moving.

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1/2/2012– Building the right wing panel. A Rafters Square helps align the ribs to the required 90 degree angle.

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1/3/2012 – Finished all the ribs and webbing. Smoothed out any rough spots and started to add the sheeting.

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1/4/2012 – Finished rough assembly of the right wing panel. Still need to trim the sheeting and attach the root cover.

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Moving ahead to the fuselage assembly. Like the wing, I’m starting with the sub-assemblies first.

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1/7/2012 – Spent the morning with the Knockabout’s designer, Jim Feldmann. I needed some help with the build and Jim offered to help me out. I couldn’t pass up the opportunity to see a true master at work, so I met Jim at his flying field and we fixed up my wing. There was an issue with the trailing edge being the wrong dimension and since it was already installed Jim came up with an idea and it solved the problem.

Jim had brought some planes to fly and offered me some stick time on one of his .40 sized Knockabouts and I enjoyed taking a few laps around the field.

I had hoped he might have had a Super Knockabout with him but his is still configured with floats. But, he did have a second Knockabout with him that was just as pleasing. A one-off twin! Jim took a crashed Knockabout and made the modifications and turned out real winner. Not only does it look stunning but if flies very well and the sound of a twin is hard to beat.

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1/14/2012 – Went float flying this morning with Jim. I had my little purple Knockabout and Jim brought the Super Knockabout. The SK flew just as I’d hoped. Jim rarely flew straight and level and put on an impressive display.

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Continuing on with fuse assembly. Each side of the fuse needs a doubler before the firewall and formers can be attached.

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I used 30 minute epoxy to give me plenty of set up time. Its a big fuse and required a bit of time to spread out a thin layer of the adhesive. One issue to deal with is being careful to not clog up the tab slots in the doubler with the epoxy. These slots need to be clean so the former’s tabs fit correctly. I applied clear box tape over the slots on the backside of the doubler, trimmed down as much as possible, which prevented the slots from filling up with the epoxy.

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2 1/2 and 5 pounds weight plates make great building aids to apply pressure while adhesives set for large areas. Clamps can be very cumbersome in some situations.

1/15/2012 – Built up the left side of the fuse with formers and servo and fuel tank tray. The trick now is to fit the right side fuse into the tabs and hope the fuse is straight.

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There was no trick. Jim engineered the fuse build design so that the two halves self align perfectly without the need for a jig.

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1/16/2012 – No problems with he fuse build. I got through with about 3/4 of the assembly to the point where I want to do a temporary install of the engine, throttle cable and fuel tank while I have plenty of visibility and access. I have to wait for a few parts to arrive so I’ll get back on the wing build.

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To recap the build so far, other than running into one dimensional difference with an installed part, each step has been pretty straightforward. Jim’s instructions have been spot on and as I had previously surmised, that 80% of the build process is documented, and 20% requires build experience, has so far been about right.

But, I have since discovered that I only posses 18% build experience and have required Jim’s help with the 2% deficit. Well, maybe more like 3% or 4% extra help, so far!

1/26/2012 – Just about finished with the left wing panel. Same build process as the right panel.

1/28/2012 – Wings are built. Still need to trim the excess sheeting and install the ailerons. Used a mix of thick and thin CA along with wood glue to make sure all joints are good and strong.

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1/31/2012 – Temporarily mounting the DLE-30. The front of the prop hub needs to be 6.25 inches from the firewall. I’m going to use the supplied standoffs which are 2.4 inches long for a total prop hub length of 6.32 inches. It’s just a bit long but I think I can make it work.

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I printed the mounting template from the Hobbico version of the engine manual, cut it out so it fits within the firewall and aligned it with the center lines laser cut into the firewall. Then taped it in place and marked my mounting bolt holes.

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2/5/2012 – Making progress on the wings and fuselage.

Trimmed up right wing panel removing the excess sheeting, leading and trailing edges and spars. Next step will be beveling the aileron and cutting the hinge slots. I’m going to try a tool called the Slot Machine from Great Planes. It’s on order and should arrive soon.

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The fuse is just about ready for the sheeting and shaping of the cabin roof, windshield, and front deck. This is going to be a challenge for me as it requires a lot of shaping and sanding to get the contours right.

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2/10/2012 – Continuing on with the fuse, I started to install the deck and windshield formers and stringers.

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The sheeting needs to be curved to form the fuse before it can be glued in place. As Jim suggested I used window cleaner on one side of the sheeting and taped it in place to dry for a few hours.

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Also worked on the wings and got them trimmed and ready for the shaping on the leading edge and cutting the hinge slots. I received the Great Planes Slot Machine and practiced making slots and boy what a time saver. Clean and straight slots every time. I’ll detail the process when I”m ready for the real thing.

A friend recommended a tip to help outline the root and wing tip ribs so you can get a nice clean and close cut when trimming off excess sheeting.

You use pins to mark the location of the rib and then pencil in a line. Remove the pins and start cutting. Worked great.

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Ailerons beveled and ready for hinging. I used the Great Planes Center Line Marking Tool to find the center of the aileron and the Great Planes Contour Sander which has a 30 degree “V” channel for beveling.

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2/13/2012 – Taking a break from sanding I assembled the fuel tank. I’m using a Du Bro 14oz tank. Instead of soldering on fuel line bards I thought I’d try the solder blob method this time. Pretty easy to do and should work just as well as the barbs.

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I’m told to expect the Knockabout to balance tail heavy with the DLE-30 so I need to get as much weight forward as I can. I’m going to cut a hatch in the front bottom fuse plate to access a nice little compartment that both the ignition and receiver batteries will fit in. I’ll wait to cut out the hatch until I verify the balance point.

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I laid out the electronics to better understand the Smart-Fly ignition cutoff and voltage regulator usage which I’ve not used before.

Two A123 6.6v 1,100 mAh batteries
Two Heavy duty switches
Specktrum AR9010 9-channel receiver (not pictured)
Smart-Fly Opto Ignition Cutoff
Smart-Fly 5.2v Ignition Regulator

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Here is some good information regarding the ignition cutoff from the TBM web site that I found very useful:

ATTENTION: The Smart-Fly Ignition Cutoff is designed to work with a separate ignition battery only, the ignition should not be powered off the same power as the receiver!

Ignition Cutoff for Single-Receiver Setups

The Ignition Cutoff provides safety and convenience for your gas powered plane. The unit has two modules that are connected by a fiber-optic cable. There is no electrical connection between your ignition and your radio system. The LED on the ignition side is removable and extendable with standard extensions. The LED is not required for the unit to operate properly.

Ignition Cutoffs:

How are they connected?
They are an electronic switch between the battery and ignition. The switch is only on when the receiver has power and the switch on the transmitter is engaged.

What good is it?
1)Your ignition is always off if the transmitter is off or if the receiver has no power so you can’t start the engine thinking that your transmitter or receiver is switched on and it isn’t causing the engine to start at high throttle and causing an accident.
2) If your engine rips loose from the firewall and the throttle and choke servos no longer work, you can kill the engine when you want as long as you remember which knob to turn when you are panicking.
3) If your throttle servo breaks in flight, and you don’t have a choke servo to kill the engine, you can use the kill switch to stop the engine at the right time to land safely.
4) If you lose all power to the receiver, which is virtually impossible on a two battery set up, the engine will be killed so that you don’t have to walk so far to the crash site.

Who needs one?
1) People who only have one battery powering their receiver.
2) People who like the security of having an extra switch in line to prevent accidentally starting the engine with either the receiver or transmitter off.
3) People with a little extra cash who like bling bling stuff.
4) People who want the safety feature of having the plane crash with the engine shut off instead of running should the receiver lose all power. The plane will crash further away from spectators and will do less damage to the airplane.

2/18/2012 – Working on the tail feathers now. Rough sanded the stabs to shape and they are now ready for hinging.

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I decided to go with Robart 1/8″ Steel Pin Hinge Points for the rudder and elevator. After practicing with the Dubro Heavy Duty Hinges, I preferred the simplicity of the Robart hinges.

Robart makes a Drill Jig that really makes it simple to find the center of the control surface and to drill a straight hole.

I’ll use Titebond wood glue as it has been proven to be very effective for hinges. It’s water soluble for easy clean up and doesn’t cause a major problem if some of it gets into the hinge joint. I won’t be gluing in the hinges until after covering.

I’ve been using the Ryobi 1/4 in. 4-Volt Cordless Screwdriver for sometime now and it’s the perfect “drill” for these small projects. It’s light weight and slow speed so you have very good control.

I may have gone overboard on the number of hinges I used. The mfr rates the 1/8″ hinge for up to .90 size models, but the recommended 3/8″ hinges were just to big for the material. So with the added vibrations from the 30cc gasoline engine I figured its better to be safe.

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A little cap piece is needed when the hinge is longer than the material. You want all the adhesion area you can get.

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A countersink bit cuts out a nice pocket for the hing joint to sit flush with the face of the control surface.

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The hinges have not been fully set in place yet as the less you enlarge the holes the better fit you’ll get when gluing.

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Same process for the vertical stab as with the horizontal stab.

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The tail section is done and ready for final sanding and covering.

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Now she’s really starting to look like an airplane.

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2/25/2012 – Moving along with the wing hinging. Same process as before except I’m using the larger 3/16″ hinge points.

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The trailing edge material is also thinner than the hinge points are long so I needed to add balsa caps.

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One wing panel done, ready for final sanding and covering.

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2/25/2012 – Needed to figure out a way to securely mount the fuel tank and still be able to easily remove it for maintenance. I went with a tray and channel system.

I mounted the tank on a 1/8″ piece of ply using Velcro straps and made up channels using 3/4″ balsa.

The mounted tank slips into the channels for a secure fit and at the rear of the tank I’ll add a strip of ply held in by screws to keep the tank from sliding out the back.

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2/27/2012 – Getting close to covering. Finished sheeting the deck and windshield. Now I just need to shape the corners of the roof then final sand the fuse, wings and tail section.

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3/17/2012 – Have some work to do on the cowl. The kit provided an off-the-shelf Great Planes Skybolt cowl. It’s a bit short which requires some reshaping to fit.

I used a heat gun to apply some heat to each corner of the cowl, one at a time, and reshaped it a bit.

Before the reshaping.

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After reshaping. The bottom fuse corners need some shaping and I still need to cut out the bottom of the cowl for engine clearance before I can finalize the fit.

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Getting the wing ready for mounting. Two dowels position and hold the front of the wing and two bolts hold the rear. I needed to ensure that the wing sat properly in the wing saddle by enlarging the dowel holes a bit, then aligned the wing tips with the back end of the fuse and drilled the rear bolt holes.

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Almost ready for covering. I have my colors; white, purple and orange. I just need to work out the scheme.

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3/18/2012 – Working out a color scheme.

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3/29/2012 – After fitting the cowl, the stock muffler requires cutting out a large portion of the cowl side. To keep it a clean install I decided to order a JTEC Raidowave in-cowl muffler.

The stock muffler is 1 1/2″. The thickness of the muffler needed to be no more than 1 1/8″ including the flange and the JTEC muffler is 1″.

The exhaust tubes can be cut to any length needed.

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4/2/2012 – It’s cover time!

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4/6/2012 – Spent some time with a friend who is a covering expert and watched as he effortlessly covered the horizontal stab. I’ll start with the vertical stab and hope I do a good job.

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4/8/2012 – Moving slowly and simplifying the color scheme. I was a bit over ambitious with the curves in the original, nice straight lines are all I can handle! Still planning on adding the orange stripe with silver pin-striping, I hope!

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4/9/2012 – Figured out the color scheme. The orange is just printer paper, not even close to the actual orange Monokote, and the silver is silver Sharpie, but it works as a mock up.

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4/13/2012 -Made a slight change to the scheme pin striping. Also, removed some of the white covering from the horizontal stab and added the purple caps.

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The silver pinstripe is from AutoZone.

The orange stripes are MonoKote applied over the white MonoKote using Original Windex. Apparently this is an old method and works great for MonoKote over MonoKote applications.

Spray a liberal amount of Windex on the surface, lay down and adjust the stripe, then squeegee using a credit card and let dry. Use an iron to lay down the ends and its done.

This technique does not work with Ultracote. The adhesive on the MonoKote is activated by the Windex (by the ammonia maybe?) but the Ultracote adhesive is not affected by the Windex.

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4/14/2012 – One and a half hours and the left bottom wing panel is done.

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Another hour and a half and the left top wing panel is done. Next is the purple tip and an orange stripe with silver pinstripe to match the tail feathers.

Working slowly (very slowly in my case) eliminated wrinkles. Be patient and let the iron work them out.

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4/15/2012 -Finished one wing panel.

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On to the fuse!

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4/18/2012 – Fuse is nearly done. Just need to add the windows, a stripe and pin striping.

I was going to use two colors, but for a beginner the added complexity and the fact the I learned that purple is a lot different to work with than white (much less forgiving) made me change my mind. I need to figure out how to work in the purple on the fuse so that it compliments the rest of the plane.

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4/20/2012 – Mocked up the fuse stripes. Tried various combinations of colors and decided on this. To bring in some purple I’m going with purple windows. The cowl will be painted white with an orange stripe.

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Taking care of some of the little stuff while I mull over the fuse scheme.

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Windex is a stripe’s best friend!

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One stripe done.

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4/21/2012 – Glued in the tail feather hinges.

Soaked the Robart hinges in Denatured Alcohol to remove the mold release.

Heated up Vaseline and dipped the hinge joints in to get a nice thin protective coating.

Ran Titebond into the hinge holes using cut down Q-tips.

Applied a good layer of glue onto the hinges with an epoxy brush.

Had to work fairly quickly as the Titebond sets pretty fast, but it was nice not to have the epoxy mess.

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4/24/2012 -All control surfaces are hinged and connected to servos. I used Du-Bro Heavy Duty Adjustable Control Horns all around.

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Rudder is Pull-Pull using Du-Bro Heavy Duty System.

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Changed the switches to JR, the smaller size fits and looks better. Ignition light will be mounted under the switches. Cowl needs to be prepped for paint then mounted.

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Fuel tank has been fully plumbed with the fuel dot added to the right side of the fuse (opposite of the switches). Just need to add the windows and windshield to complete the fuse.

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4/25/2012 – Needed to figure out where on the firewall I would be able to mount the ignition. Turns out that there is not a lot of options, so I came up with a mount that would make the job a bit easier.

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My friend Jason was able to get the windshield on which was giving me all kinds of problems.

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4/27/2012 – All the windows are in place, the fuse is now complete. Just need to work on the cowl and get it painted.

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4/28/2012 – Jim had warned me that with the gas engine and elevator servo in the rear of the fuse that I could expect the Super Knockabout to be tail heavy, and sure enough it is. As I was progressing with the build, and with that information in mind, I had found a location to mount the batteries in the front of the fuse if needed. It required cutting out a hatch in the bottom fuse plate.

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I simply covered over the cutout until I was sure it was needed. Now that it is I”ll remove the covering and complete the hatch with a Du-Bro hatch latch.

A preliminary balance has the CG between the recommend 4 – 4 1/2 inches, right at 4 3/8″. When I add the cowl and spinner it should come in at 4 or 4 1/8 inches.

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4/30/2012 -Finished the receiver and ignition battery installation and hatch.

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Electronics installed.

Throttle & Nose Wheel Servos – Hobby People HP-A50M
Rudder, Elevator & Ailerons Servos – Hitec HS-645 MG
Receiver – Spektrum AR9020
Ignition Cutoff – Smart Fly
5.8 Volt Ignition Regulator – Smart Fly
Receiver & Ignition Switch – JR
Receiver & Ignition Battery – A123 6.6V 1,100mAh

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5/13/2012 – Received the 2 1/2″ aluminum spinner from Tru-Turn. Needed to have the slots customized to accommodate the large 18 X 8 Xoar prop.

Applied the first cotes of paint to the cowl and mocked up the stripe.

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6/3/2012 -The stripes are now painted on the cowl and the Super Knockabout is ready for its maiden.  I’m waiting for my friend George who also built a Super Knockabout and should be ready for his maiden in a few weeks.

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7/22/2012 – Maiden scheduled for this Saturday!

7/28/2012 – Successful maiden! The Super Knockabout flew great. Video after the pictures.

 

7/15/2016 – The Super Knockabout has been flying for four years now and it’s just as fun today as it was back then.  After many dozens of flights I’m glad to report not a single issue.  Everything has held up well and she is a great giant scale sport plane.

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I had forgotten that I still had an original .46 size Knockabout ARF in a box.  Decided to go electric with an E-flite 52 with a 13×8 prop and 6s 5000 mAh lipo.  Great combination for a six pound sport plane.  Really rips and flies nearly full throttle for 8 minuets.

 

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Comments
  1. Jim Feldmann says:

    Danny:

    If you are very experienced with MonoKote, I’m sure you will do a good job. But if not, I would strongly suggest that you use UltraCote instead. I know it is more expensive, but it is MUCH easier to put on and seems to stay on longer without wrinkles or separating seems.

    • electricdan says:

      Thanks for the advice Jim. I happen to have a friend that used the similar colors I wanted as well as matching paint so I went with the MonoKote. That friend is a covering expert so I’m in good hands to get me through this.

      We’ll see how it turns out!

  2. Jim Feldmann says:

    Lots of airplanes over lots of years have been beautifully covered with MonoKote. I’m sure that the help of your friend will make your learning curve much shorter.

    Jim

    • electricdan says:

      So far so good. I’m glad I “practiced” with the somewhat easirer parts to cover. Now on to the wings and fuse.

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