Birdbrain RC SKEW_R 5

By CarbonRain on Jan 14, 2019

10  240  3

Hadn't flown the Mahou Shoujo prototype for a while (been doing more freestyle than racing over the past 7 or 8 months), so when I cracked it out for some circuits last weekend I fell in love with how it flew all over again. Planning on doing more race events in the 2019 season, so I decided to revisit the design and whip up something a bit more race-day friendly.

The Mahou Shoujo is a great quad, but its main advantage is also its main disadvantage - it's a very low maintenance build, which makes it difficult to damage but if you do damage it, it's practically impossible to fix on race day. Last race I flew with them, I broke a baseplate in a big crash and had to write off the quad for the day, as fixing it would have required desoldering and resoldering all the motors from the 4-in-1 ESC board, and with only 4 groups at the event it didn't leave enough time for that sort of work between spotting and flying.

As a result, I decided to whip up a frame with the same stretch plus geometry, but in carbon rather than HDPE, with individually replacable arms to make field repairs easy. I also decided to stick with the skinny arm and cross brace layout of the plastic equivalent. Fitting it all together with those constraints was a bit of a challenge until I realised I could make it work if the arms were all rotationally skewed, making the frame asymmetrical. In terms of flying this shouldn't make any difference, as stretch plus quads are already technically asymmetric in nature, having uneven yaw due to the front/back motors being further apart than the left/right pair, something you never notice in the air.

The pod went through a few design iterations, starting with a plain pod I found the FPV camera would foul on the pigtail at the max 60 degree notch (up from the 30/45 degrees on the Mahou Shoujo pods, not that I expect I'll be using it much!) Whilst tweaking that, I added a fin to help protect the antenna by deflecting impacts from close to the connector. What's probably hard to see in the photos is that directly under the pod is a printed shelf for the VTX and RX (both fastened down with velcro), and I incorporated a little V shape for the RX antennas too.

Build was a straight swap from the Kittilyt 6 (excluding the ESC which was new, old one finally called it quits after 6 months of abuse). Happy with the result, it looks pretty tidy and is 40g lighter than the identically built Mahou Shoujo. Time will tell as to how the frame holds up to crashes, but I'm cautiously optimistic (and already have files prepped for slightly stronger parts if required. Just need some good flying weather now!



Sign in to comment

Mellowme17   Jan 17, 2019  

curious about this i love plus frames not manh out there can you fit race wire on the arm? looks like fullsize cam... nice work

Mellowme17   Jan 17, 2019  

curious about this i love plus frames not manh out there can you fit race wire on the arm? looks like fullsize cam... nice work

QU|(K_F0X   Jan 15, 2019  

Looks like a really well designed frame, good job!

Guides & Reviews

49 5,141  43
Jan 15, 2019

The iFlight XL5 V3 is a fantastic freestyle frame for the price. It features chamfered edges on some very nice quality carbon fiber. My goal for this build was to use high quality components at a relatively low price. Not only that, but I managed to reduce the number of solder points to the bare minimum. I've never built such a plug-in-play quad! The flight controller has an integrated VTX and doesn't..

Read more
14 2,882 
Nov 16, 2018

Update! Happymodel has released a new V2 Frame which uses a more durable plastic. The Happymodel Mobula7 is one of those rare treats to hit the micro scene. Countless models hit the market every month, but this one just happens to check all the boxes. It's a 2S brushless micro with a 75mm motor stance. It's slightly larger than the more traditional 65mm brushed micros, but it's still quite small...

Read more