The flying season is winding down here in Western Pennsylvania so I have returned to the building board. I have a couple of designs I have been flying for a while but have not written up yet. This is one of them. I have flown this for more than a year but did not write an article on it because I was not able to provide adequate plans. Unlike most of my previous designs you need full sized plans to build this one.
It looks like this:
(No power pod or servos yet)
This is a basic intermediate or advanced trainer depending on the wing option. You can start with intermediate wing with dihedral and then move up to advanced by simply making a second wing with no dihedral. It uses a standard FT power pod with tabs removed.
Although it is not patterned after any specific real airplane it does have a somewhat scale appearance. It looks and acts pretty realistic in flight.
We call this the "Stout Trainer". The name came from a comment by Bob McBride who is doing the drawings with me for this design. When I first sent pictures to him he responded saying, "That looks like a really stout wing on that trainer." I liked the ring of it, "Stout Trainer". We have been calling it that since.
“Necessity is the mother of invention”. Truer words were never spoken as applies to the “stout” wing on this model. I was helping the physics teacher at the local high school learn to fly with a buddy cord as a part of my involvement in his aviation based STEM class. Well, there is not a loop that Mr. Rupert does not like. I had flown this airplane numerous times including frequent tight loops. “Rupe” as his students affectionately call him, proceeded to do the tightest possible loop with full power. We had gone up with about 5 degrees of dihedral. All of a sudden we were flying with about 20 degrees. I immediately took the controls back and somehow nursed it back to a safe landing. Obviously the wing had failed. The glue joint was still tight but the wings top panels had developed wrinkles and some delamination on each side of the centerline. That evening I decided to do a quick and ugly repair so I could get back out flying as soon as possible. I cut it at the centerline and made 10” wide top and bottom splice panels to reinforce the weakened area. To make it simple I took the dihedral out. I went out the next evening and low and behold the model actually flew considerably better. Control inputs were sharper. Turns were more consistent. Aerobatics seemed more solid. Within a week or so I had changed to a larger motor, reduced the wing’s angle of attack and added 1” to the ailerons. Each change increased the performance. Over time the ugly wing splice did not seem so ugly. I actually started to like it and it did really work well, especially with the larger motor. The reinforced splice became a design feature to be incorporated in all future wing modifications.
Well, so much for how we got here. Here are a few more shots:
1. Efficient use of materials: The fuselage and tail uses the full width and length of 2 sheets of DTFB joined on 20" sides with very little waste. Each wing uses one full sheet of DTFB on a no waste basis. Wood parts use one 6" X12" sheet of 18" lite ply with no waste. Misc. Parts use another 1/2 sheet of DTFB with very little waste.
2. Conventional high wing monoplane appearance.
3. High lift, short take off wing.
4. Larger size for gentler handling.
5. Large full length ailerons and large tail control surfaces for responsive aerobatic performance.
6. Standard FT power pod with tabs removed for ease of equipment service.
7. Battery at CG to allow large latitude in battery size for longer run times.
8. FT style under cambered wing tips for tip stall control.
This is the fourth build with a few refinements along the way:
1. On the original fuselage design I had placed the tail plane too low. It was in the wing wash. I cut and reshape the original fuselage to test the concept then redesigned to the current arrangement.
2. The original ailerons were 1 1/4" wide and were less responsive than desired. I redesigned the wing to still be a one sheet no waste component with ailerons increased to 2 1/4".
3. The original motor was a D2826-6 2200 kV from Hobby King with maximum power of 342 watts. I changed to a L3010B 1300 kV also from Hobby King with 420 watts. The power increase was significant.
4. The original wing failed performing tight aerobatic maneuvers under full power. I reinforced the center of the wing with top and bottom wing doublers to hold up to the extreme loads.
5. The original nose was one layer of foam board. I widened the nose 3/8" and added nose doublers to strengthen it.
6. The original horizontal stabilizer curled in the sun. I added two dowels to stiffen it.
7. The original vertical stabilizer warped in use. I added a leading edge dowel extending to the bottom of the fuselage to stiffen it. I also extended the back end down to sandwich between the fuselage sides,
Here are a few more detail photos:
The Windows (duct tape):
The Tail Skid:
The Power Pod:
Top Wing Doubler:
Bottom Wing Doubler, Centering Blocks & Hardware:
Wing Bottom Details: Black(duct tape) and Full Length Aileron:
A while back Bob McBride contacted me expressing interest in building my 80" No Waste Flying Wing. He had a couple of questions about missing or unclear dimensions. He sent his questions in the form of a multi color digital drawing. Now I am thinking, “I wish I could do that!" We went back and forth a couple of times. He ended up with a nearly complete drawing in very short order and offer that I could use it as my own when it as done. I replied that I would like to offer it to the community but would only do so if his work was properly credited. I told him about my predicament regarding the trainer and suggested that we could partner on it. "Designed by: Dan Harkless Drawn by: Bob McBride". He graciously agreed.
For the last several weeks we have been working on the drawings, learning each other's methods and working out the details. I think we are ending up with a pretty good set of plans. Our results will be attached below. You can be the judge.
These plans are pretty complete. They use standard FT building methods. I believe a very experienced builder could build successfully just from the plans.
The following are large full sized sheets. They can be printed as tiles using "Poster Print":
To "Poster Print":
1. Click on the drawing to open it.
2. Left click and "Save As". Select location and save.
3. Go to the saved location and double click to open the file.
4. Click "File" / "Print" / "Poster"
5. Set Tile Size 100% and Portrait
6. Click "Print"
(Tiled drawings to be added soon)
The following are 8 1/2 X 11 sheets that can be printed directly:
I am including a Building Sequence narrative below. It is pretty lengthy so I am including it as an separate file. Moderately experienced builders should be able to follow the plans and building sequence for a successful build.
Update 1-25-16: I have revised the Building Sequence reversing the order of installing parts "G" and "H" based on a suggestion from jalkin to make the installation of "H" easier. Thanks to jalkin for the good suggestion. (This is the second revision. This one is correct.)
You can click below to open then print the Building Sequence file.
(End of update)
(Note: Additional details may be added later)
Type: Single motor high wing (cabin) monoplane
Landing Gear: Tail dragger with steerable tail skid
Wing Span: 60"
Length: 45 1/2"
Weight: 1580 g (3.5 #) with 5000 3S battery; 1400 g (3.1#) with 2700 3S battery.
Wing Area: 4.55 SF
Wing Loading: 12.4 oz / SF: 10.8 oz / SF
Power: 420 W @ 120 W per #; 135 W per # (Hobby King L3010B -1300 kV)
Maximum Thrust: 1800 g (tested) w/ 9050 prop.
Motor: Hobby King L3010B- 1300 kV 420W, 1650 g thrust
Prop: 9050 or 9 X 4.7
ESC: 50 A with UBEC
Battery: 2200 20C 3S to 5000 3S (Wide range because it is located at CG)
Servos: (4) 9g
There are two wing options that can be built. The version in the pictures is the advanced trainer with a straight wing. An optional intermediate training wing can be built with about 5 degrees of dihedral. This would be a good first aileron trainer.
Take off distance is short, as little as 15' to 20' on grass.
Climb rate is fairly quick but not straight vertical with this motor. It will climb at over 45 degrees.
Overall flight performance is pretty impressive with the suggested motor. It has sharp responses to control inputs. It is capable of either extended slow and easy flight or a full range of aerobatics. It does fairly large to very tight loops, sharp to slow and easy rolls, inverted, hammer head stalls, etc.
I have had flight times of 15 to 20 minutes with two 2700 3S and still had about 30% to 40% battery life left. That was with the throttle set at anywhere from 35% to 100% doing aerobatics mixed with some slow and easy flying around. I have not yet had the patience to do a long duration test but I believe I could get between 30 and 45 minutes going easy with this set-up.
It is very easy to fly yet has considerable aerobatic capabilities, an ideal combination for a trainer.
If you are looking for a model that looks like and flies like a real airplane in the air and has flexible training capabilities from intermediate to advanced skills this could be the plane for you.