There is at least 2 reasons I like tailsitters. They are perfectly suited for my small flying field and I like to see a plane just floating in the air. Since Arduplane support tailsitters I made dual motor types but more recently copter types were added. Special thanks to @kd0aij and @iampete
I thought the quad plus was the right type to make a racer able to land in my hand. The top image shows what it looks like from the front
And floating in my garden
Wing span is 90cm, wing is made of wood on a foam core and fuselage is made of Balsa.
Airfoil is TP100, a 7.3% thick profile designed for fast plank tailless wing. Like other airfoil in this class, it is designed to have a stable “almost 0” pitching moment whatever the speed. When looking at longitudinal stability a stable Cm allow to reduce the static margin and this is what we want to get a stable hover. For this wing static margin was set to 7%.
Vertical fins are set at a certain V angle to bring more stability.
Wing motors are sunnysky 2212 2600KV, top and bottom motors are Viking 2208 2600KV.
But the most important is the batteries 2200mAh 2*3s graphene 70C, potentially more than 3KW, not bad for a 1300g plane RTF. Maybe you would warn not to use 2600KV motors on 6s and you are right, I have burned several of them so throttle must be managed with care.
To go fast you need power and fast propellers. Pylon racing propellers are fast but not available CW/CCW and they hardly produce a small thrust at low speed. The fastest suited propellers I found are Emax Avan S 5x7.5. Their pitch is surely not 7.5 inches but they produce a nice thrust.
ESC’s are multistar 51A, I know they do not always have good reputation but in my case they were rock solid. The BLheli soft is able to detect the short produced by a burned motor so they survived a lot of abuse. I just added a aluminium capacitor at their input.
An other important detail is elevon servos. Because you want 45° throw to fly as a copter and only 2 or 3° when flying fast. So, fast and accurate servos are mandatory.
A first video to show hover flight, transition and fast forward. To be honest, this is not the more stable in hover I have made but this is OK on a calm day.
Is the quest completed ?
Two speed run with yaw in one direction and other direction almost 180°. In both directions max airspeed is about 84 m/s (302km/h). Max gps speed are 88m/s and 81m/s. I think gps speed is only horizontal speed so adding the vertical speed would give a higher speed.
An other interesting speed is max vertical speed about 64m/s.
And for those who want to know how it looks like from the air