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Sep 28, 2008, 11:17 PM
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**CTH "Q" Plane Trainer**


The CTH "'Q" Planes

Have you ever felt like all the planes you build are the same and you would like to build something different? Here is a plane to try. It is simple easy to build and flies amazingly well. It comes apart to pass the "Corolla test" which means it can fit in a small car

We have been looking for a new trainer that is fun to fly. I have been flying the plane for years but have not offered it for sale. I flew it at a local fly-in and had several requests from beginners for kits. The kits will be available from our onliine store at www.crashtesthobby.com
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You will see two versions in the videos. Don't let them fool you they are the same plane. One is just dressed up to look like an Eagle. I was flying the Eagle version the other day and had several cars park to watch what they thought was the real thing. It was fun to watch it stop traffic. I don't even think it really looks like an Eagle. I would think the loops and rolls would give it away.

This is an RET (rudder, elevator, throttle) design and it is more aerobatic that the elevon version that I built in the testing. It barrel rolls both directions, flies inverted and will inside and outside loop. The plane is aerobatic but makes a good trainer due to the big square stable stick wing and RET design.

These planes are based on an old design that was brought to life again in the 80s by a plane marketed by QJet called the Q-Butterfly designed by Parker Leung. In honor of the plane I will stick with the "Q" name for the plane even though it is entirely redesigned.

I must also give some credit to the EPP Eagle thread for inspiring me to make an Eagle version. It is fun to have a plane that looks like a bird and where we get lots of hawks and Eagles here in Utah USA it is fun to watch their reaction to the plane.

I posted some videos on a club site and since I have had several requests to post more information. It will take me a few days to get the information together so please be patient.

I also like to save a few post slots for building information and to bring information forward to make it easy to find if the thread gets long. I encourage you to add your comments and questions and pictures and videos of your planes as you build them.

This video is a testing video where I was making trim adjustments to the outboard reflux tabs which I will discuss later.

(3 min 16 sec)


This video is the trainer version that will even thermal on a warm day. I also shot some video of power slope flying thousands of feet above the valley where I live.

(4 min 59 sec)


This video is is slope flying with my Eagle version on the same mountain slope.

(4 min 12 sec)


Last edited by Lee; Oct 02, 2011 at 08:23 PM.
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Sep 28, 2008, 11:18 PM
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Last edited by Lee; Oct 02, 2011 at 11:23 PM.
Sep 28, 2008, 11:18 PM
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Some looks at the Q-plane fuselage and wing.


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Last edited by Lee; Oct 02, 2011 at 11:25 PM.
Sep 28, 2008, 11:19 PM
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#4 Q-WING

The Q-Wing is a wide square wing that is usually a polyhedral flat bottom RET design with a large elevator cut in the back trailing edge of the wing. I like to make the elevator 1/2 of the wing span and 1/4th to 1/3 the wing cord in the center section of the wing. Tapered wings can be used but any radical taper greatly changes the flying characteristics and stability of the design.

The CG will be back at about 20% of total wing area including the elevator. Keep the nose mount motor and move everything forward because the CG will be farther forward than you think it should be.

How can you make most any plane into a Q-Plane? Leave the elevator off and cut the elevator into the trailing edge of the wing. Shorten the fuse and put the rudder just behind the wing. The center of gravity actually moves forward and is usually about 20% of the total wing area.

Most any basic wing will work with elevons and a Q-Tail but the flat bottom wing works best in a RET design. (rudder elevator, throttle)

Keep it light and it will fly better!!!!

One of my original planes was a gag plane. it was a Q-Plane design with elevons set up with a fake elevator behind on the tail. I made it so I could eject the normal tail elevator in flight and the plane would keep flying as a flying wing. I did this on a 60 sized "Stick" configuration that had landing gear. The entire plane weighed 6-8 lbs so it had a great effect. It really messed with everyone's heads when the tail came off but the plane had been trimmed with the tail off so it flew better after the tail was ejected. After the tail was ejected it was fun to fly as if the plane was about to wreck and you were trying to save it. After a couple of close calls it would become obvious something was up and the plane was under control and quite aerobatic.


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Last edited by Lee; Oct 02, 2011 at 11:27 PM.
Sep 28, 2008, 11:20 PM
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#5 Q-FUSLAGE

The traditional Q-Fuslage is short and stubby. It is cut to fit a straight square wing that traditionally does not taper. The wing may be flat with elevons or a polyhedral RET (rudder, elevator throttle) design like the Q-Eagle. It can be built with most any airfoil but flat bottom is the basic RET design. In other words the Q-Planes have a large signature rudder right behind the wing on a short stubby fuslage.

The motor is angled down with the RET design and may be straight forward with a low wing or symetrical airfoil flat wing designs.

The fuselage can be made out of balsa or foam and have most any shape.

I sculpted the fuselages you see in the pictures out of a solid block of 1.9 lb H3.5" x W2.5" x L24" EPP foam. Weight is a concern but the short fuslage didn't add that much weight over the built up fuslage and it defiinitely is alot stronger. I use a band saw for the original shape and then using a sawing motion sculpt the fuselage with a sharp box knife to get the shape I want.

I used a straight blade box knife and a soldering iron to cut out servo and radio slots to fit my rudder servo, spektrum receiver, ESC, battery and motor mount. The rudder servo is in the fuslage. The elevator servo is mounted in the wing. You may see that I have 2 elevator servos in the wing. This helps to split the elevator to clear the fuselage in the middle of the wing and also allows me to play with elevons and flaps if I want. I use a "Y" connector to connect the two servos to the receiver.

I don't like the look of the rubber bands to hold the wing on, but the simplicity and durability is hard to beat. I have used wing bolts and in some cases actually glued the fuselage to the wing then installed the radio from one side.

When you use rubber bands you need to put some form of reinforcement on the wing to keep the rubber bands from from tearing through the foam. On the Q-Eagle I put several carbon rods inset into the foam to keep the rubber bands from tearing the wing and on the Q-Trainer I glued some colored craft "Popsicle Sticks" on the wing. The Popsicle sticks work the best if this is the method you choose.

The Rubber bands loop over a 4mm Carbon tube that goes through the fuselage. On each end of the carbon tube I have glued a 1" square piece of Formica with the carbon tube through a hole in it to keep the carbon tube from tearing through the fuselage. AS of yet I have not had any tearing of either the wing or the fuse with these reinforcement ideas.

The hardest part of the plane is to figure out the motor angle. The motor is significantly tipped down in both the trainer and the Q-Eagle. At the same time the elevator is trimmed up which seems a odd way to do things but this design seems to give the best flight charactistics.

I have taken kits you can buy and left the traditinal horizontal tail surface off and cut the fuslage down and made Q-Planes out of them. It annoys people which is a good enough reason for me. I hear people betting if some of the modifications will fly.

One of the designers who has expermented with the flying wings is Bill Evans. He wrote many articles for the RCM magazine over the years and contributed to my love of the odd planes. He even had his own airfoil that he used on a wide variety of tailless planes.


Last edited by Lee; Oct 08, 2008 at 04:53 AM.
Sep 28, 2008, 11:20 PM
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#6 Q-RADIO INSTALLATION

This is how I set up the radio in a solid fuselage. It is a challenge to hide as much of the radio as possible.

I get all of the electronics I want to use including motor, battery , ESC, receiver and servos and in this case "Y" connector. I lay the radio out and check the length of the cords. Lately it seems that some of my ESCs and servos have too short of cords for the set up I wanted.

I know the battery has to be at the front of the plane in order to get CG to that magic 20% of the wing area. I also know the motor has to be on the front of the plane so I start with these two pieces. I like to have easy access to the battery so I can change it quickly without having to take the wng off. I really don't even try to hide the battery any more in order to spend more time flying and less time changing batteries. I can change the battery in less than 10 seconds when flying.

I mount the motor and then look at the length of the cords that connect it to the ESC and then draw on the foam the location where I can mount the ESC taking into consideration getting around the battery. I use a longer box knife and a soldering iron to cut the holes. In the Eagle the ESC is under the battery and In the Q-Trainer the ESC is under the wing.

Look at the pictures in post #3.

I feel like I'm making a sales pitch but I want to say I really really like my Spektrum 6100e receivers. They lay flat with the cords coming out the end and the tiny antennas out the side. I have always hated routing antennas and I no longer have much to worry about with the new Spektrum design. I have never had a range problem with the 6100e receivers and I have really put them through some intense flying and distance testing. In the pictures you can see I have drawn red lines on the fuselage where I route the antennas and push them into slits in the foam. The red lines help me find the slits in the foam.

I have tried mounting the servo in the fuselage under the wing in the Q-Eagle to the side of the fuselage on the Q-Trainer. Both installations work well.

Some things to notice.

Look at the deans plug I use to plug my motor into the ESC. I have been taking the deans micro 4 prong plug and cutting off the one separated plug and soldering the male plug to the three wires on the motor and the female plug is soldered to the three wires to the ESC. This makes it simple to trade motors and or motor direction. If I want the motor to turn the other direction all I have to do is turn half of the plug over to reverse the motor direction.

If you have servo or ESC cords to hide you can cut a slit with an exact knife and using a finger nail or phillips screwdriver push the cord under the surface of the foam and out of site. This is best seen on the wings with the two servos and the hidden cords. I cut out places to put the excess cords that are too long when needed.

I use a little hot glue to secure each of the pieces that have any possibility of moving. Make sure you don't damage your radio or get so much glue on the receiver that you break the antenna getting it out. (ask me how I know this)


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Last edited by Lee; Oct 08, 2008 at 03:55 AM.
Sep 28, 2008, 11:21 PM
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#7 Q-MOTOR AND THRUST

Q-Planes can be any size but I usually like to use the same power system for most of the planes I design. Why???? First of all I build quite a few planes and standardizing the batteries ESCs and motors helps to keep the cost down.

I like the BP21 or the FC28-12 with a 7x6 prop and a 1300 mA 3s lip-o and a 20A-25A speed control. This motor combination puts out about 21 oz of thrust and will take a small plane in vertical climb. If you watch some of the power bursts in the videos you can see they fly strong. They still fly well at 1/3 throttle

The Q planes do have down thrust due to the flat bottom wing and thrust angles from where the motor is placed.. Most trainers have to have some thrust angle adjustments. On the other thread that I have been working on the "Capricorn Tutorial" the plane has to have upthrust and so does the Snowball that I designed. Finding the right angle is one of the most challenging parts of designing planes. When everything is said and done and you built a plane just like the plans say to .... trial and error is often the way the motor gets fine tuned to the right angle. When you look at the Q-Eagle testing video I was fine tuning the trims and angle to get it to fly the way I wanted it too. To me it is one of the most important parts of building a plane that is fun to fly.

In the first Q-Eagle video I am setting the thrust angles of the motor and setting the reflux of the elevons. it didn't occur to me at the time that an explaination of the logic of the process would be benificial but you can see the results in the videos of how well the plane flies and how controllable the plane is. Initially the plane had some strange behavior with different throttle settings and power off gliding but a little trial and error testing helped me trim the plane to where a beginner would love it. I think that this skill of learning to trim in a plane is one of the most important skills a designer or new flyer has to learn.


Last edited by Lee; Oct 08, 2008 at 04:00 AM.
Sep 28, 2008, 11:21 PM
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#8 Q-PLANE FLYING

The Q-Trainer was built first. I went out to a local track at a school to test it and on the first day trimed it in for maximum glide and was amazed how stable it was. I obnoxiously set the transmitter down to show how stable it was. The plane was quite high and was slowly circling over our heads. I was waiting for it to come down when I realized it was thermalling up and getting higher and higher with the motor off. I had to dive the plane to get it back down. It almost floated up out of site.

The plane has an interesting spin as you give it full up and full rudder to bring the plane quickly back down.

In the video of the Q-Trainer notice the rate of climb. The Q-Trainer weighs less than the Q-Eagle and it will go straight up but it is gentle in a glide and is easy to fly. My goal on the next Q-Eagle is to keep the weight down and get the same performance. The Q-Eagle is still my favorite Q-Plane to fly and I fly it frequently. My eye likes the look of a bird like plane.

Another charactistic of most flat bottom or semi-semetrical flying wings is that as they gain speed they start to pull up all by themselves. This is caused by increased airflow over the refluxed airfoil. I am so used to it I don't even notice but if you haven't experienced it before you will realize the plane is doing some things on it's own. The polyhedral wing also tries to level the plane side to side so there are a lot of aerodynamics at work here.

The roll rate is unexpectedly crisp and controllable. When you see a RET plane doing barrel rolls take notice. I agree part of it is the pilot but if a plane can't do it the plane is going to turn into a lawn dart. My confidence in the plane is obvious with the low altitude rolls and loops and vertical climbs.

I think the videos say more than I can say in any text. I hope you like the Q-Planes.




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Last edited by Lee; Oct 08, 2008 at 04:27 AM.
Sep 28, 2008, 11:22 PM
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Reserved for building log #9
Sep 28, 2008, 11:23 PM
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Reserved for building log #10
Sep 29, 2008, 01:04 AM
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They looks good fun... I look forward to some close up pics of the Q-trainer's workings.

Eagles seem very popular! Several eagle threads already running..
Sep 29, 2008, 07:37 AM
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hows about some plain ol'pic's for us on dial up? thanks, rc
Sep 29, 2008, 07:47 AM
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Some pics here post #1704 https://www.rcgroups.com/forums/show...page=171&pp=10
Sep 29, 2008, 08:21 AM
Lee
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I posted some picture in post #1. Sorry about the dial up. The videos show the character of the plane. The coverings add so much weight that for years I have painted these planes. This Q-trainer with a 48" wingspan is less than 17 oz. The Q Eagle has more paint and EPP wingtips and so it weighs a little more.

The motor system is the BP21 or the FC28-12 with a 7x6 prop and a 1300 mA 3s lip-o and a 20A speed control. This motor combination puts out about 21 oz of thrust and will take the plane in vertical climb. If you watch some of the power bursts in the videos you can see they fly strong. They still fly well at 1/3 throttle.



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Last edited by Lee; Sep 29, 2008 at 08:36 AM.
Sep 29, 2008, 11:30 AM
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Lee, Whats the chord of the wing and how wide are the elevators...

Lots of downthrust....How much?


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