CapnBry
Elite member
I really love the size of the 75% Goblin by JUSS10 and have built a few of those, but then I started looking for more of an endurance build and started making modifications. After 4 or 5 different iterations, I've ended up with this model, which has now flown over 500 cumulative miles!
The electronics are accessed with just the top flap having a tape hinge on one side and a piece of tape to hold it shut. Make a little handle on the tape by folding the edge so you can grab it to open it up, and use another piece of tape on the fuselage to provide a good place to stick to without peeling the paper. The front hatch also is just a tape hinge and if you cut it right it fits well enough that it won't open in flight, but a rubber band over it works too.
The plans have just a round foam nose, but also have a line where you can stop cutting and skip all those annoying curvy cuts and just use a 3D-printed nose with screw holes to mount the camera easily. This went through a lot of different versions, starting with just a reinforcement that went inside (because I bonked into a rock on landing once and broke my lens) to finally just removing the nose entirely and replacing it. Between the double layer of foam and glue and stick to hold it in place, the fully 3D printed nose ended up being slightly lighter than the original and sure is a lot easier to make. Nose and firewall 3D printed parts are on Thingiverse
Caveats!
When you load it up with all this extra hardware, it starts to get a little heavy. Just this plane with no FPV / FC / 950mA 2S is going to run you under 200g and can really slow down, but at 235g the stall speed is around 32kph / 20mph, and with 18650s it is around 37kph so it wants to land fast. With the CG in the perfect right place (somewhere around 20mm) it will just descend when it stalls so no big deal, but with a safer CG (10mm), the nose will bob up and down as it stalls and may cause Sudden Landings if you come in slow. The model is so light though that I've never had a problem with damage coming from a landing stall, the moist grass is a larger threat.
This all still fits on 1 piece of DTFB. The wing is just cut as one piece, and some weight can be saved by peeling the paper off the inside wing surfaces anywhere they aren't exposed / control surfaces. I didn't need any reflex in the elevons, or at most 1mm of reflex. There's no thrust angle on the motor and it behaves really well without pitching wildly when jumping to full throttle, most likely due to the low amount of thrust generated even at max.
EDIT: How does it fly?
Can't believe I forgot to include this information! I think it flies better than most FPV wings in this size range I've see on youtube. It has no yaw waggle, the wings are pretty stable, and it is somewhat agile. With a 60/40 split for pitch/roll and low throws, it will still roll at 400degrees/sec and pitch at 180degrees/sec. It lacks power to loop at cruise throttle though so for loops expect to do 85-90% throttle to have any chance of success. Otherwise it sort of gets to 45-80 degrees of pitch and just gives up. Inverted flight is not a problem at all.
There's a gentle stall characteristic and I've never experienced a tip stall. It can also turn on a dime due to its light weight, but steep climbs (like loops) you'll need to pour on the power.
- Fuselage width reduced by 17%, still room to mount a 30x30 flight controller
- Reduced fuselage tail area, by 10mm vertically, 4mm horizontally to fit 12x12 mount motors more closely
- Reduced wing thickness by 25-33%, removed undercambered wing tips
- Increased wingspan by 10%, wing area by ~20% (can't recall exactly)
- Redesigned vertical stablizers for smaller size and more prop protection
- Cutouts in wing to fit 30x30 FC and space to put an ESC near the vent holes in the back
- EMAX 12A ESC
- Cobra 1407 3500KV motor, also fits 1606 motors
- Gemfan Windancer 4032 (x3) prop although a HQ 4x4.3x3 pulls slightly less current, slightly lower speed, equal efficiency
- 2x Turnigy TGY-1551A 5g servos
- ExpressLRS EP1 RX (mounted in hollow of wing)
- Omnibus F4 Pro V2 flight controller
- Rush Tank Ultimate Plus 800mW VTX
- Caddx Ratel 2 Starlight micro camera
- Lumenier Micro AXII Shorty 5.8GHz antenna
- BN-180 GPS
- 170g dry weight, 235g with 1300mA 2S, 270g with 2S 18650
- 130g dry weight with no FPV gear or FC (ESC+Servos+PWMP RX)
- CG: Around 10-20mm from leading edge
- Wingspan: 660mm
The electronics are accessed with just the top flap having a tape hinge on one side and a piece of tape to hold it shut. Make a little handle on the tape by folding the edge so you can grab it to open it up, and use another piece of tape on the fuselage to provide a good place to stick to without peeling the paper. The front hatch also is just a tape hinge and if you cut it right it fits well enough that it won't open in flight, but a rubber band over it works too.
The plans have just a round foam nose, but also have a line where you can stop cutting and skip all those annoying curvy cuts and just use a 3D-printed nose with screw holes to mount the camera easily. This went through a lot of different versions, starting with just a reinforcement that went inside (because I bonked into a rock on landing once and broke my lens) to finally just removing the nose entirely and replacing it. Between the double layer of foam and glue and stick to hold it in place, the fully 3D printed nose ended up being slightly lighter than the original and sure is a lot easier to make. Nose and firewall 3D printed parts are on Thingiverse
Caveats!
When you load it up with all this extra hardware, it starts to get a little heavy. Just this plane with no FPV / FC / 950mA 2S is going to run you under 200g and can really slow down, but at 235g the stall speed is around 32kph / 20mph, and with 18650s it is around 37kph so it wants to land fast. With the CG in the perfect right place (somewhere around 20mm) it will just descend when it stalls so no big deal, but with a safer CG (10mm), the nose will bob up and down as it stalls and may cause Sudden Landings if you come in slow. The model is so light though that I've never had a problem with damage coming from a landing stall, the moist grass is a larger threat.
This all still fits on 1 piece of DTFB. The wing is just cut as one piece, and some weight can be saved by peeling the paper off the inside wing surfaces anywhere they aren't exposed / control surfaces. I didn't need any reflex in the elevons, or at most 1mm of reflex. There's no thrust angle on the motor and it behaves really well without pitching wildly when jumping to full throttle, most likely due to the low amount of thrust generated even at max.
EDIT: How does it fly?
Can't believe I forgot to include this information! I think it flies better than most FPV wings in this size range I've see on youtube. It has no yaw waggle, the wings are pretty stable, and it is somewhat agile. With a 60/40 split for pitch/roll and low throws, it will still roll at 400degrees/sec and pitch at 180degrees/sec. It lacks power to loop at cruise throttle though so for loops expect to do 85-90% throttle to have any chance of success. Otherwise it sort of gets to 45-80 degrees of pitch and just gives up. Inverted flight is not a problem at all.
There's a gentle stall characteristic and I've never experienced a tip stall. It can also turn on a dime due to its light weight, but steep climbs (like loops) you'll need to pour on the power.
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