The Snoopy Plane or Curse you Red Baron!

Introduction

I have always been a Charlie Brown and Snoopy fan.  When I took up flying radio control model planes one of the first things I wanted to do was to try to find a snoopy figure that I could use as a pilot. Alas my search was in vain. Fast forward 5 or 6 years to when I started playing with 3D printers. I had a go at designing my own Snoopy pilot figure. It wasn't that accurate but I got a laugh out of sticking him on top of a tiny trainer and watching him zoom past.  Recently I found a 3D model of Snoopy on Thingiverse which looked a lot more like Snoopy than mine. I downloaded it and modified it by chopping his body in half ( to give me a bust) and adding a flying helment and goggles. I started thinking about Snoopy sitting on his kennel flying around searching for the Red Baron.  A kennel without wings just didn't seem right. In my mind's eye an SE5 like nose popped out of the front and a tail out the back of his kennel. Wings appeared out each side.  That image kept coming back to me until I decided I had to try to design my own flying kennel. One that would have wings, fuselage and a tailplane. Not authentically Snoopy's flying dog kennel but I didn't care.

The Design Process

I started out with an 800mm wingspan because I was trying to get away with a smaller battery and power setup. I looked at a few british WW1 fighters (i.e. The Sopwith Pup and the SE5). From these I came up with the shapes for the horizontal and vertical stabilisers.  I wasn't keen on a biplane for three reasons. Firstly there was the added compilcation of struts and aligning the two wings correctly. Secondly I was already concerned about the amount of drag the kennel was going to produce so I didn't want to add to that. Finally an extra wing would reduce the visual impact of the kennel. Besides, for whatever reason, the image in my mind's eye was a monoplane.

I started by sketching a side view and then a top view in QCad. I then spent some time ensuring that the two views were consistent with each other.  The next step was to construct the plans for the wings. They seemed the easiest place to start.  The fuselage came next, followed by the tailplane and vertical stabiliser.  Finally the dog kennel. This turned out to be a tad fiddly because I had to design it so that it could slide into place over the completed airframe.

The construction of the first Snoopy plane was pretty straight forward. The kennel was a bit of a tight fit but otherwise it all went together okay. I decided not to use a power pod because I wanted to maximise the internal space and minimise the weight.

The result looked pretty good. I had a power system that used 1500 mAh batteries and provided plenty of power (or so I thought). The picture below shows the first Snoopy Plane. Note the not so Snoopy like Snoopy.

Maiden of Version 1

I took off easily but found I could not get any higher than about 20 feet. The power to weight ratio was good but I had under-estimated the amount of drag the kennel was producing. I realised that Snoopy was in dire straights and the plane was on the verge of a stall. I tried to gently manouver it around for a landing. I almost made it but I guess I banked just a tad to much when turning onto final and down she went. Apologies for not having any pictures. I was surprised at how little damage there was.  More power meant a bigger motor and shifting up to a 2200 mAh battery. I would end up with a plane that would fly but it would have a high wing loading and basically be no fun at all to fly. In other words my Snoopy plane was easily repaired but would never fly the way I wanted it to fly.

The Re-design

I reasoned that if I simply scaled the plane up I would have exactly the same problem with a bigger plane. I then thought that if I scaled it up so that no forward facing surface increased in size then that would minimise the drag increase. So I increased the length of the fuselage and the area of the flying surfaces by 20%. The width and height of the fuselage and the kennel stayed the same. I made the length of the kennel such that it just fit over the wing. That decision also meant that I could re-use all the 3D printed parts I had made with the one exception of the battery hatch which had to be longer.

I printed the plans and away I went. Before long I had version 2 of the Snoopy plane ready to go. By this time I also had my new and imprved Snoopy pilot (see below). The plane turned out a bit heavier than I wanted and I was thinking it was an even bet as to whether or not it would fly.  I used the power train for the Durafly SE5. My reasoning here was that surely an extra wing and all those struts and wires would generate as much drag as my dog kennel. Also the WW1 style prop looked really cool. My friend Shaun Atkins donated the prop to the project as he had a spare. 

The plane weighed about 1kg and, according to my thrust meter, generated about 1.2kg of thrust.  This was a lower power to weight ratio than the first plane. I told myself that, relative to the overall plane size, the kennel is smaller. On the first plane I used 2mm piano wire for the landing gear but had to go to 3mm for the, larger and heavier, second plane. I didn't do a great job on the bending so it ended up too narrow and a bit lop-sided. The consequence of that is that landings and takeoffs are not very graceful. I'll have a go at bending them wider but that isn't easy when it is already glued to the plane.

In the end I thought that Snoopy Plane Mark 2 might fly okay but was not convinced.

The Maiden of the Second Snoopy Plane

This time I was better prepared. I got my friend Shaun to hand launch and had decided that if power was an issue I would simply cut the throttle and land straight ahead.  As you can see in the video Snoopy did not disappoint me because the plane flew great. Shaun launched it, I did a turn to the right and then could not resist asking Snoopy for a half cuban! He replied by showing me the Snoopy Plane can manage that with no problems at all. Shaun correctly reminded me that maybe I should at least trim the thing out before I start throwing it all over the sky. It needed some left aileron and a tad of right rudder and then was flying straight as an arrow.

Landing took me by surprise. I had kept the throttle wide open for the entire flight. When I backed off in order to land I expected the drag to rapidly slow the plane down and so I reduced power cautiously. What happened was it didn't slow down that much! The Snoopy plane really retained its energy and eventually I had the throttle closed. I guess its a weight/lift versus drag issue. Needless to say my first landing was past where I expected to touch down. My landing gear didn't help so "clumsy" was the nicest thing you could say about that landing.  I did two other flights getting braver and braver. By the third flight I was making low passes and doing aeros quite comfortably.  The video below is of the first two flights.

Snoopy Plane Specifications

Wingspan:  112cm

Length:  77cm

Weight without battery:  866gms

Weight with battery:  1050gms

Motor:  I don't have a model number as Hobbyking do not provide one (see power specs). The motor does have the numbers 3536-850Kv on the motor housing.

Power Specs:  230 watts, 21 amps, 1150gms thrust (My batteries are old. This motor can do better but this is watts/amps that will keep the Snoopy plane in the air).

ESC:  Hobbyking 40 amp (overkill but it is what I had to hand).

Battery:  2200 mAh Zippy Compact

Servos:  9 gram analog.

Receiver:  Lemon DSM2

Conclusion

My motivation for this project was simply that I love Snoopy and I wanted to see if I could turn a cartoon plane/day dream into reality. It took two attempts but in the end I succeeded. I don't expect that anyone would want to build one of these for themselves but, just in case you are as crazy as me, I have included all the plans, 3D models and build instructions below. In the end I have a model plane that flies about the same as the PT-19, Hurricane or FT-Spitfire (although the roll rate is a little faster). Other than landing the extra weight is not noticable when flying. However the point of this plane is for the visual spectacle and nothing else.  I intend to fly the daylights out of this thing and I expect that everytime I see Snoopy sailing past me it will bring a smile to my face.

If you have an idea maybe you should give it a go. After all the foam is cheap and the time spent is you embarking on a quest and making memories.  Even if your project is a total fail you would have still enjoyed the process. You have nothing to lose and everything to gain. The only variable is how much fun you will have.  If my second plane had been a fail I probably would have given up on the idea at that point but that would not have taken from the enjoyment I got from the whole design/build/fly process. Of course its more fun when things go right but that is just the icing on the cake.

Build Instructions
I know its a bit strange having more information after the conclusion but I figure that not everyone is really that interested in building a Snoopy Plane so it makes sense to put the build info here so that those not interested can stop reading now and those that are can read on. If you have never built an FT style model before then this one is probably beyond you at the moment. Start with one of the simpler FT designs and work your way up. After that the Snoopiness can begin.

We start with the wings...

A typical FT style wing. Two wing halves sliced and diced in the usual FT way. The first step is to glue the box spar together.

As marked on the plan these are B folds. Its long so do one side at a time and make sure you get each side tucked in properly and that each side is at right angles to the bottom.

The next step is to tape the two wing halves together. The tape is applied to the outer surface of the wing. The wings are folded back and glue added to the join from the inner side of the wing. The wings are then held down on a flat surface to dry. Make sure you wipe away excess glue.

Next we glue the box spar onto the top surface of the wing. Lining up the edges with the two creases that run the width of the wings.  The spar should be positioned centrally so that the ends line up with the ends of the bottom wing surfaces. Note the little hole in the middle is for the servo wires. Now is a good time to cut the clear tape away so that the servo cables can be passed through later.

Next we add glue to the leading edge and the box spar and fold the wing over and hold it flat on the table with the bottom of the wing held against the table. When dry (hold it down for 5 minutes to be sure) add glue to the trailing edge of the bottom wing and hold that down until its dry.

A very typical Flitetest style build so far. Okay now we move onto the fuselage.

Aside from no power pod this is also typical Flitetest.  We have our main fuselage and some bulkheads. In typical Flitetest style we have partially cut out our wing openings but left them in place to give strength to the fuselage sides when assembling the fuselage.

Start by gluing one side to the bottom. These are B folds. Make sure you have the side at right angles to the bottom.

Glue the other side to the bottom. Again ensuring a right angle between side and bottom.

Now glue the top on. Again B folds. You need to apply glue to both sides at once so trial fit first and make sure the glue gun is hot.

Glue the rear bottom to the sides. Again we have to do two sides at once. Once in place turn the fuselage over and slide it back and forth on the table while pressing down. This will ensure the paper on the bottom edges gets pressed hard against the sides. Do not hold it still because if glue spurts out the side you will have succeeded in gluing your fuselage to the table (ask me how I know!).

Now we cut our wing slots out. Remember we didn't completely cut them out so that the fuselage sides would not be weakened by the holes during assembly. You will note that my Snoopy Plane has few wrinkles here and there. This is because I got a tad carried away with the spray paint and put too much paint on in one go. Sigh...Patience really is a virtue.

Wing cutouts removed.

Tail feathers are glued together ensuring that the vertical stabiliser is at right angles to the tailplane.

Next we ease the wing through the wing slots and get it nice and central. After you have it in position check that the fuselage is still square. Sometimes with all the gentle pushing and shoving the fuselage can end up a bit slanted over to one side. if it has then just massage it back so it is nice and square again. When you are happy run glue along the wing roots (top and bottom). Don't forget to wipe away the excess each time.

Fit the tailplane ensure that it is lined up with the main wing. Then glue it to the fuselage. Note that I seem to have got the plans a bit out of wack here so the ends of the fuselage need to be held against the vertical stabiliser while the glue is drying as they sit slightly off the vertical stabiliser surface. Do a trial run first and you will be fine.

Next add the four bulkheads. The two half ones going on the front, followed by the large full one and then the small full one.

Next add the servos and lead the wires through to the central area of the fuselage. Cut slots into the bulkheads to let the wires through to the central area. You will need an extension lead for each servo and a Y lead for the ailerons.

Okay servos in place and wires fed through.

Next hook up the receiver which will live under the kennel roof. Before we cover everything up it would be a good idea to bind your receiver, check your servos and get the servo arms centralised and moving in the right directions.

Next we get our poster board bits ready to go on. I roll them up in the plans and leave them for an hour or so to get them nice and curved.

Tack glue the rear posterboard piece onto the two rear bulkheads making sure they are central. Run a thin bead of glue along one fuselage side and then press the posterboard down with your fingers. The heat passes through the poster board rather quickly so keep running your fingers along the join but don't stop moving.  Repeat the process for the other side.

Now do the same for the front fuselage.

Now trim the ends to suit. I made an error on the plans resulting in the bulkhead that lines up with the back of the kennel being too far back (the one with the servo leads coming through it in the above picture). The plans have been corrected but I had to do a little posterboard patching to correct my model.

Okay now we basically have a four channel model plane. Time for the kennel.  I drew the wooden planks onto the kennel with permanent black felt marker and then sprayed yellow over the top. I know Snoopy's kennel is actually red but I prefered yellow as I thought it would contrast more with the RFC brown colouring the rest of the plane.

We start by gluing one side of the kennel to the other, ensuring they are at right angles. Note that each corner has the side being pushed up against the front (so a B fold if the front or rear were facing down).

Then the next side and...

and then glue the third corner before...

Finally gluing the last corner. Note we did not glue the lower sides or the bottom front and back below the openings. These will be swung aside when fitting the kennel to the plane.

Tuck your receiver down into the fuselage for now just to keep it out of the way.

GENTLY ease the kennel over the fuselage. You will find its a tight fit but with some gentle easing you should be able to get it into position. When you are happy run a bead of glue across where the kennel meets the wings and the fuselage, wiping away the excess glue each time.

Flip the plane over and glue the pieces which go across the bottom of the openings in place. If you have trouble then cut them free, trim them to fit and then glue them back.

Now we are ready for the kennel roof. There is a central v cut into the underside (just like the wing leading edge on the wings).

Glue one side only into place ensuring the roof overlaps the front and back by the same amount and your V cut lines up with the peak of the roof. The other side will act as a hatch allowing us access to the receiver.

This is where you need your Snoopy pilot. If you don't have a 3D printer then you are going to have to get one from somewhere. I am told people sell McDonalds Snoopy figures on eBay, you could give that a try. Alternatively you could do a silhouette Snoopy in foamboard. You need a square of foamboard as a seat for him and you need to paint it black so that it is as unnoticable as possible. You will also need to cut a foam block as seen on the left. Run some skewers through the foam block and glue them in place. The foam block will sit on top of the fuselage and the seat will sit on top of the foam block.  Hence the height of the foam block needs to be customised to your Snoopy to ensure he sits at the right height. The length is the roughly the width of the Snoopy seat and the width is the width of the fuselage. Glue your Snoopy to the seat.

Glue your foam block to the fuselage, ensuring that your receiver and servo leads can run clear of it.

Now you can get the idea. Run elastic bands from the skewers, across Snoopy's seat and then over to the skewer on the other side. Do this on both sides and Snoopy is held snuggle in place but is easily removed if needed.

Now we need some way of holding our kennel roof/hatch down. If you don't have a 3D printer you will have to come up with something equivalent. I printed two of these brackets, cut slots in the front and back, placed the bracket in place, put some hot glue on the top of the bracket and closed the lid until the glue dried. That way they are in exactly the right place.

Finally I ran a skewer through from front to back to hold it closed.

Next I glued the 3D printed part shown in the above picture to hold the undercarriage. This is the exact same idea as used on my Ugly Stick and it works a treat. If you do not have access to a 3D printer then you could use a 5 or 6 mm thick piece of plywood.  You could then glue 3 mm ply sections on top to create the channels for the piano wire. In the above photo I have cleverly glued the piece on backwards! The two slots on each side that run towards the rear of the fuselage should run forwards instead.  I won't go into just exactly how much fun it was getting the thing off without wrecking the plane and then gluing it back the right way around. Trust me it was interesting. Each wire comes up out of the hole bends 90 degrees and crosses over to the opposite side where it turns 90 degrees and runs forward to the front of the block where it bends downwards and outwards and runs to the wheels. Once bent correctly each wire is hot glued into place. Cut and glue a piece of poster board to cover the bottom of the kennel (poster board instead of foamboard to save weight).

The markings I drew in QCad, printed, cut them out and then used a glue stick to glue them onto the plane. I have included the pdf files for the markings with the plans and other data. Finally add the 3D printed radiator and machine guns, fit your battery to get the right CG and you are ready to go! The centre of gravity on  mine is 55mm from the leading edge and it seems about right. My battery slides under the wing between the wing and the fuselage bottom. If you are using Adams foamboard then it will probably be different to that, depending upon the motor chosen. Okay go forth, build and then let Snoopy loose.  Most of all Enjoy.

Data Files

The pdf files for the tiled plans are here.

The pdf files for the whole sheet plans are here.

The Sketchup files for the 3D printed parts are in two sets to get around the maximum file size allowed in Flitetest articles. The first set is here and the second set is here.

The STL files for the 3D printed parts are here.

The pdf files for the markings are here.