Sledge 540 Extreme 3D DTFB plane with free plans!

The Sledge 540!

Designing/testing

       I recently got into 3D flying and wanted a DTFB plane that could fly 3D. Don't get me wrong, the FT3D is great, but it can't perform slow maneuvers as well as a larger model. I wanted to design a plane that could perform easy harriers, hovers and other 3d maneuvers. I came up with the Sledge 540. I named it the Sledge 540 because I tried to make it look like a Slick 360/540 and a Edge 540. One of the main deviations from the Slick/Edge design I made was I that made a lot of side area on the fuselage. I wanted to give it lots of side area so it would be able to do good knife edge flight with little rudder input. I also ended up making the leading edge of the wing swept back as opposed to straight like on an Edge. V1 and V2 had a straight-leading edge, but it flew better with the leading edge sweeping back.

3DHS Slick 540                                                           

 Edge 540 (Full scale)

       I started building the first version at the end of July, and I am now on v5. The first version flew great as a sport plane, but it could not perform slow maneuvers, and it would fight you every step of the way. It would stall VERY badly when you tried to harrier and was very unstable in hovers. Luckily I ran into Andrew Grant at our local field a week or so after I built v1. Andrew Grant is an incredible 3D pilot and also has some great articles on FliteTest under the username VoroRC. I asked Andrew to fly it and maybe give me some tips on how to make it fly better. He took it up and did some awesome 3D flying. He flew it so hard he stripped a servo and was hovering with one aliron! He instantly knew what it needed: taller rudder, longer rudder, wider wing, side force generators, and a slightly lower elevator/horizontal stab.

       The first thing I did was give it a taller/longer rudder. It completely changed the plane! Harriers were super stable with little to no wing rock and no stalls. In addition to the harrier, it also made the plane hover much better. Then on the 3rd version, I extended the wing chord at the base of the wing by simply adding some flat foam at the front of the wing. I could have built a completely new wing which would have looked better, but this was the fastest/easiest option given that I would have to use two sheets of foam board per wing. This made the plane fly ‘’lighter’’ and made the hover significantly more stable. The final thing I did was lower the elevator 1/2’’ and add side force generators. This helped with knife edge and a little bit with harrier.  

Building

        I used some aluminum landing gear from a old trainer that worked great. I had wheel pants on the first version, but I took them off to save some weight. I mounted the gear by simply gluing an 1/8th inch light plywood plate inside the fuselage and I just bolted the gear to it. The first version had a tail wheel, but I ended up removing it and replacing it with a piece of 1/8 ply  to save weight. On my new Sledge, I tried not using gear and it was great. It was able to hover at a little over half throttle, but I ended up putting the gear on it anyway because it is so fun to take off and land with the Sledge. Landing is very easy, and it takes off in tallish grass with 2.75’’ tires.

1/8th inch ply wood plate

Tail Skid

        For the hatch/canopy, I just used a flap of foam board. This is what I do for most of my scratch built foamies. I usually put hinge tape (really any tape would work) on the hinge for the flap so it doesn't wear out. Then I simply put velcro on the top of the hatch to hold it down, It isn't the most aesthetically appealing method, but it works. To get the CG right, the battery needs to go right on the spar. So I put velcro right on top of the wing inside the fuselage, and I put a popsicle stick through the fuselage over the battery so it can't fall out. On my second Sledge, I glued down the canopy and made a battery hatch on the bottom of the plane in an attempt to get a lower CG. This made harriers a little bit more stable and took away some coupling in KE flight. Currently in knife edge, there is very very very little to no aileron coupling, although it does need a very small amount of down elevator in KE. I simply put a rudder to elevator mix (4%). Also the leading edge extensions and SFGs help a small amount with KE coupling. My good friend Paul Jennings tried some vortex generators on his, but he said that it didn’t fly as well.

       The wings were made using the exact method as the FT3D: full symmetrical airfoil that tapers down. The ailerons just tape on. I used hinge tape on V1, but packing tape works fine. The wing  is currently just glued in, but I don't think it would be all that hard to make it removable. The wing does have two 12’’ pieces of ⅛’’ light ply on each side of the spar in the center. This is to join the two spar halves and to just add more strength. If you aren't going to be pulling very high G maneuvers, then  you could use foam instead of ply. The servos are mounted close to the ailerons so there is less slop. I also covered the servos with a piece of foam to make it look a bit better.

Power system

       There are two batteries that I use. I use a 2200 4s for sport and more fast and violent maneuvers, but I found that a 2200 3s worked much better for slow 3D flying. It has much less power on 3s, but it flies significantly lighter than the 4s. The only down side to 3s is that you have to hover at ¾ to full throttle with the gear on as opposed to ½-¾ on the 4s. I think an 1800 4s would be the perfect battery for this plane if I had one. Lots of power, but the same weight as an 3s. The power system is very similar to what I use on my other 45”-60” planes. It is a Detrum (Dynam) 3520 650kv motor swinging either an 13x6 or an 13x4 prop. On 3s, a 14x4 prop would probably be best. I used a 40 amp esc from Detrum as well. The motor is just glues in, but it could be made swappable.The servos in the 1st version were all tower pro 9 gram nylon gear servos, but they were a bit too small.  Currently I am running some HS-65HB servos from HiTec. I have never understood why people buy pricey HiTec servos when they could but a Hobbyking knockoff, but now I understand. These servos rock!

Tips on 3D

       If you ever plan on building or designing a 3D plane here are some things I learned while building this. One of the main things is keep it as light as possible. It was crazy what 50 or 100 grams can do to the flight performance. Weight didn’t make that much difference when sport flying, but when you are trying to hover, harrier or just fly slow it makes a ton of difference. One more thing is that if your plane harriers or stalls bad, then try making the rudder taller! I have extended the rudder on two other planes and it make the harrier stability much better. The reason for extending the rudder is because when you are in upright harrier, the wing blocks airflow over the rudder, but by extending the rudder you can get the top of the rudder in nice smooth air. Andrew explains it very well in his Harrier tutorial video. One other thing that Andrew taught me is that when it comes to side force generators, sometimes less is more. I have always disliked SFGs, likely because I always made them too big. When you make small SFGs, it can increase stability and KE flight.

Specs!

Wingspan: 48’’

Length: 45.5’’

Root chord:14.5’’

Tip chord:9.5”

Wing loading: 11oz/sq.ft

Weight (4s): 44oz

Wing area: 576 sq.in

Battery: 3-4s 1800-2200

Motor: 2035 650kv

ESC: 40amp

Servos:  9g MG servos or HS-65HB (Best)

Prop: 12x4.7-13x6 (13x6 best)

Plane Pics!

Flight Pics!

Final version video (v5)

V4, tallter rudder, larger SFGs, wing extencions, small SFGs on tail

V2, taller rudder with very small SFGs

V2 in lots of wind

Plans

      The plans include SFGs, wing extenders, and the tail SFGs. My favorite configuration is SFGs only. The other things help with slow maneuvers, but make faster maneuvers less crisp and violent. You can play around with the configuration and see what you like most. My favorite CG location is right on the spar, but this plane dosen't care about CG all that much so put it where you like it. For throws, I am 100% on everything with 25-30% expo. 

https://drive.google.com/folderview?id=0B_Vajn7eE2YdekhHNjRvUnMzaWc&usp=sharing