The Kraken Killer 2.0 (Flying Yield Sign)

Im writing this after the creating of this article. Do not build this airplane to my specs unless you have substantially more power. My maiden flight ended in a spectacular crash that ruined the nose where none of the expanding foam was. I plan to stick to the 60 inch size. It makes it a lot easier to transport.

The Kraken Killer or better known by it's flite fest nickname the flying yield sign partook in combat for the first time at flite fest 2014. The beast of an airplane showed its true potential after destroying a versa wing but suffered a stripped servo.

The collision can be seen here at the 50 second mark.

With little to no damage suffered there is no reason to build a new one. A simple servo swap and it would be back and ready for action. But at this point in time I do not have a replacement servo. So whats the next best thing? Build an entirely new plane that will become the ultimate combat airplane capable of eating Krakens for breakfast. (but I will fix and continue to fly the first version)

I must pay credit to wear credit is due. The plans can be found here http://www.rcgroups.com/forums/showthread.php?t=1771799

This plan is for a flat plate design which obviousy is not similar to mine. All of the measurements were  scaled up using basic proportions. As an example 30/80=4/10.66   10.66 being the new tip chord. To my knowledge this is the largest delta wing with an airfoil. But you could potentially make one even bigger than mine.

The original Kraken Killer had a wingspan of 60 inches and a surface area of 1440 sq inches. The plane has a wonderful flight envelope and all arround great flying characteristics. The original was powered with a park 480 motor on a 3 cell lipo. With my new plane to have an 80 inch wingspan and 2559.6 sq inches of wing area I will need a larger motor to have the same flight characteristics as the previous plane.

But first you may ask, why go bigger? I say why not? As seen in the video, a FT versa wing barely upset my airplanes flight path. But to me that is not good enough. I want to create the end all be all drednaught of a combat plane that versa wings will bounce of and not even budge my plane. And also its just fun seeing if I can make stuff fly.

Now onto the building portion of the project.

But first I need supplies. This is'nt your average 3 sheets of foam rc plane. I am expecting to use atleast 20 sheets of dollar tree foam to build this monster. Also to strengthen the leading edge I will need some GREAT STUFF Big Gap Filler . I recomend this to anyone who is building aiplanes with the armin wing or FT technique. It will make the leading edge of your wing nearly indestuctable and for very little weight. While my first plane had no spars other then the foam wing formers i plan to use spars in this plane to insure its longevity. I will be using wood spars because they are cheap and easy to come by.

 Be sure to get the white foam. Yes, the black foam would look cool, but for some reason the black paper delaminates much easier than the white foam board.

 This is the stuff i used to fill the plane. If your going to build a large plane buy a LOT of this. I used 6 cans and it was unable to completely fill the plane.

 These are the spars I will be using. It was a little over 3 dollars for two of them at Lowes.

This is the first panel I made to get the 80 inch wingspan. Prior to connecting them all (using same technique as on the kraken), I covered each sheet of foam with packing tape as shown by Ed from experimental airlines.

 The large panel with the outline of the plane drawn onto it

 Here it is with the wing formers and motor mount. The extra foam in the front is going to keep the expanding foam from entering my electronics bay. You can also see where I added foam to the outsides of the larger panel so when i fold the foam over it will be large enough to form the whole airfoil.

 Here is The first test fold to make sure everything will line up before i fill it with foam. I opted for the EA technique of removing the paper for a smooth curve instead of the Flite Test style. Not for perfomance just soley for looks.

 Here it is after filling it with foam and just prior to folding over the second side. As you can see I ran out of expanding foam. Oh well live and learn I guess. You can see the rear most spar but the other spar is further forward.

 Here it is, post filling, and all glued up.

 Just for giggles here it is with the Kraken Killer 1.0 for comparison. 

Before moving onto the vertical stabilizer(s) i think i should mention that I have ran into a problem. When filling the wing with foam I did not put enough of the foam into it in particular areas. To correct this issue I have had to drill holes in the wing for the nozzle of the foam can to fit in, in order to fill the empty voids. I highly doubt it will have any negative structural effects but it is less astectically pleasing. Unfortunately in some areas I put to much foam into the wing. My hope was that it would spread out laterally however in one area it expanded vertically causing a buldge in the wing. This also occured on the first version and the only way I can think of to fix it is to cut the wing open and tear out the foam that is causing the problem. And so that is what I did. I cut out a panel of the dollar tree foamboard and just tore out the problem foam. This may have not been nescessary because the buldge was only on the top. And I am well aware that lift is created by the air on top creating a low pressure zone. So in theory, I would assume it would still make lift but then there would be more drag on that side. 

Prior to adding the vertical stab(s), I have put my electronics in the plane. This is just so I do not damage the stabs if i have to flip the plane over for some reason. The hatch was made by cutting out a rectangle in the wing. The coroplast was cut to size so I could have easy acess to all of my electronics. I chose to run the servo wires on the exterior of the plane for two reasons. First because it will alow for fast servo replacement. The other reason is because it would be impossible to route the wires through the wing without them beccoming lodged in the foam rendering it impossible to replace the servos.

Here you can see the hatch I created for my electronics. You can also see several of the holes I had to drill in the wing to finish filling it.

As you can see I opted for winglets instead of one large fin. This is mostly for redundancy and it gives other pilots less of a chance to render my aircraft uncontrollable. You can also see the hatch I was forced to cut out to remove foam. It is ugly but, but hey, i built it to hunt krakens not enter beauty pagents. You are also able to see my control surfaces. Which, like my winglets, are made of coroplast for extra strength.

Here are the electronics I used.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=37798

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=38929

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26490

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=62638

This motor can run on up to 5s but i only plan to run it on 4s. I hope that with the right prop I can achieve 10+ lbs of thrust at full throttle. This would only be for takeoff and trouble situations. My first version plane could fly on a very low power setting on 3s but could still pull out in case of emergency. This is the type of perfomance that I would like.

The 50 amp esc may seem a little scrawny but I have personally pushed this same model esc to the point that it has melted off the heatshrink and continued to work. I have little doubt that it will suffice. I truly love this esc. It is very versatile and well priced. 

The original version of my plane was flying with small plastic gear servos. This is partially why the servo stripped in combat at flite fest. So I have chosen larger metal gear servos for the job.

I chose that reciever simply because it is cheap and should have all the range I need for combat. If not I will put that reciever in my sport cub and put my diversity reciever in this plane. But with this I dont have to worry about my antennas being on the outside of the plane in an attempt to achieve proper orientation.

From my calculations so far this plane should fly exceptionally well. With this wing area, my plane could way up to 16 pounds and have the same wingloading as a trainer. So far, with no electronics in it, it weighs in at 8 lbs. So I am hoping to be able to achieve the wingloading of a glider which I believe would be about 11 lbs however I forget the calculations I did to figure this out. If I can achieve the glider wing loading then, much like the first plane, It will have great flight characteristics as well as the ability to fly on very low power. To help with this I have altered the airfoil from my previous plane. My previous plane had an airfoil that was about 5% of the chord. This was only because I wasnt sure what to make it and I guessed. This plane has a 10% airfoil in respect to chord. While this is still considered a thinner airfoil, It should be more suited than the 5% airfoil which I have never heard of any other plane with that small of an airfoil. However that plane was able to glide imaculately well. To my knowlege this is solely due to the ridiculously low wing loading.

All thats left is to get a large prop, attach the control linkages, and maiden it. I will post a video later with the maiden flight.