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One Off Racer FrSky test plane

Tench745

Active member
#1
I'm breaking a promise to myself; I'm posting another project.

After FFEast I was incredibly burnt out. Months of working on the Spirit of St Louis left me pretty tired. Losing my Cafe Racer to a radio failure at the event left me even more disheartened and questioning my choice of Spektrum and Orange receivers. A week later my versa-spear refused to pull out of a loop and stripped a servo. Accelerated stall, my fault. I was not confident in my radio or abilities. The choice in my mind was, do I improve my equipment, or, basically, give up.

I opted to buy a Taranis X9D+ and X8R receiver.
Not willing to risk any of my current models and wanting to tackle something simple after the Cafe Racer and Spirit builds I decided to tackle one of my favorite doodles.
IMG_0533.JPG

The first iteration didn't work so well. I'm not entirely sure why. Test flight from a hand launch started and ended with a simultaneous uncontrollable climb and roll to the left, totaling the plane.
The wing was made thinner for a lower coefficient of lift which will hopefully reduce the climb tendency. I also moved the wing from a mid-wing configuration to a low-wing for ease of construction.
Race Plane CAD.JPG
IMG_0535.JPG

After building Version 2 I realized that the tapered wing led to some wash-in at the wingtips. I trimmed the ailerons up to help negate this error during testing. My working drawings have been updated to hopefully remove the underlying cause.
IMG_0536.JPG
IMG_0537.JPG

Of course, now I had a brand new Taranis and 8ch RX to play with, so I added flaps and played around with slowed flap deployment, flaperons, crow, etc. I wanted to add retracts, but didn't feel like spending any more on a prototype.
IMG_0538.JPG

Completed V.2 next to the stripped V.1
IMG_0540.JPG

V.2 Has not yet flown. I didn't have the weather before winter hit and Spring is still a ways off here in NY. So, despite my promise not to share another project before it had flown, here it is.

Incidentally, I'm looking for a naming scheme for my models, something to brand them as mine like Flite Test has FT and Nerdnic has NN. I was thinking MM for McBurney Manufacturing, but that gets confusing with Mountain Models...
 

PsyBorg

Wake up! Time to fly!
Mentor
#2
MacDonalds has Micky D's you could play off that and say the Micky B Racer or like the MickyBee P40 v2.3 or what ever model and revision plane you come out with. Then use some kind of Bee logo instead of golden arches. (Would not suggest using same bee as Beta Flight though.)
 
#5
It looks like it's going to be a fun little bugger. I'm eager to see all those channels in action, particularly if you do end up adding retracts later. I'm looking at buying an 8-channel receiver myself to take advantage of my Q X7's capabilities in the future.
 

rockyboy

Skill Collector
Mentor
#6
Glad to see you back in the building side again!

The look and proportions of that are very similar to the Caudron and Goon - and I think both Josh and I found that we needed to increase the emgennage size about 15-20% over scale to help tame the beast :p
 

Tench745

Active member
#7
I posted it to the FT Fans page but forgot to mention it here. This plane flew! I took it out to my second choice flying field (the first was ironically being mowed) and tried to do a ROG takeoff, but the grass was too long, so I decided to try a hand launch.
This plane seems to either want a lot of speed on takeoff or something was terribly off in the design. It flew straight ahead, but it was a struggle to keep wings level. After a few seconds of trying I lost the fight; it rolled left and the nose skidded into the ground. Things were a bit crunched, the forward turtledeck was ripped clear off and the landing gear had cleanly removed itself, but I was able to stuff the firewall back in place firmly enough to run up the engine without it moving. I thought, "Ah what can it hurt, I've already crashed it" and I tossed it back into the air.
This time she was perfectly stable and controllable. That is, until the firewall broke free and pulled it, rather comically, straight into the ground.
Things got torn up quite a bit, but I glued it back together once more. I'm hoping to do some more test hops with the wheels on. I'm afraid they may either be too draggy, or are turbulating the airflow over the wings. Testing will tell, it may become a belly-lander. I did draw up a slightly larger v-stab, but with how well it flew after the first crash I'm not sure I'll need it. I suspect the first few landings will let me know that too.
I have plans available with both tails drawn if anyone is interested.
 

PsyBorg

Wake up! Time to fly!
Mentor
#8
That looks very similar to a Caudron 460. Maybe once this one meets its end you might wanna give Rockboys design from last years races a shot.

There were several in the actual race and I am sure at least a few others were built once the design was proven and plans finalized.
 

rockyboy

Skill Collector
Mentor
#9
Now that I've got another year's flying experience under my belt from when I did the Caudron, I'd suggest adding a bit of washout - raising the trailing edge of the wing by about 3/8" out by the tip should help with the nasty wing dropping stall tendencies. At least it will help keep the ailerons effective in the air long when she is about to stall, which gives a fighting chance of getting her back level
 

Tench745

Active member
#10
I modified the McB Racer plans a bit.
The wingspan is now 3" longer, moved the gear further ahead of the CG. This should make takeoffs from the grass less likely to nose over. I increased the amount of undercamber at the wingtips and kept the ailerons back from the undercambered wingtip, which should eliminate much of the tip stall characteristics of the first model. I switched to the larger vertical tail and removed the curve I had in the nose to ease building and allow it to take an FT powerpod. I still have to build the new version and test fly it, but if anyone wants to be a beta-builder for me, I wouldn't say no.
I even have an icon for the Taranis.
 

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Tench745

Active member
#11
I spent today building version 2.1 of what I'm calling the McB Racer. (Logo pending)
It works better when you don't accidentally double the chord thickness. :facepalm:
Building another new wing tomorrow with the right spar height.
image1.JPG image2.JPG
 

PsyBorg

Wake up! Time to fly!
Mentor
#12
Uhhhh. Ooops?

Save that wing for a different project. Looks like a good starting point for a bomber style 4 engine experiment in my mind anyways.
 

Tench745

Active member
#14
Build 3 of the McB Racer, as I'm now calling it, is finished. I balanced it up today and took advantage of a calm warm morning to maiden her. I tried my new head-strap camera rig to get some video, but my camera died just after the engine run-up, so I have nothing to share.

Maiden Flight
The grass was very long, so I opted for an underhand launch at about 2/3 throttle. There was a little bit of wing rock as the aircraft wallowed it's way quickly up to flying speed. With a little more throttle, maybe 3/4, the climb-out was quick and manageable.

Even on low rates (30% throws) you get the sense that this is an agile plane; on mid-rates (60%) one may even call it "twitchy," but I think that would be unfair as I had no expo set for the maiden. I did not try high rates (80%) as they seemed unnecessary and ill-advised.

This aircraft NEEDS rudder to fly well, especially as you slow down; I'm glad I enlarged the tail. If you don't keep coordinated in turns and you get slow the plane will drop a wingtip rather suddenly. If you manage to keep coordinated a wallowing motion warns of the approaching stall. This tendency is exaggerated significantly as flaps are deployed.

The aircraft seems rather unstable in roll. If a wingtip lifts, the plane is happy to keep going until it's upside down, but as long as you keep on top of it it is very manageable.

The first flight was about 5.5 minutes before I brought it down to tweak radio settings. I flew throughout the speed range, but did not play with stalls much other than to see approximately what speed to maintain on approach.

Subsequent flights
The second and third flights were made with 30% Expo set for mid-rates on the Elevator and Ailerons which made them sufficiently powerful without feeling touchy. Again, I did not switch to high rates.
On my final approach I let my airspeed decay too far and she started to wallow around, warning of the approaching stall. I am very out of practice and in the heat of the moment I started to push the slider forward to reduce flaps instead of pushing the throttle forward like I meant to. It was a bit of a scramble to keep her from stalling but I managed to get her level before she hit the grass. She skidded sideways a foot or two which folded the right gear under, ending my flights for the day. No other damage occurred as it was a pretty low-energy impact.

Summary:
Finally this airplane flies and I LOVE it! She has a great presence in the air, speeds up quickly and feels right at about 3/4 throttle. She'll hold altitude at about 1/2 throttle, any less and she decends. Speed bleeds off slowly compared to some of my other airplanes; flaps help slow things down quicker, but do require elevator to compensate a noticeable pitching moment.
I wish the grass had been shorter so I could try some touch-and-gos because setting the racer up for a landing and dialing flaps in as she slows is a very satisfying activity.
I have only flown the FT Spitfire in sims, but this plane feels like a sleeker, heavier Spit.
There was a moment when I flew overhead and just fell in love with the presence this plane has when in the air. It is not a beginner's plane by any means, but I think with some dihedral and smaller control throws it would become a good intermediate airplane.

I'm going to look at swapping around aileron and elevator linkages to reduce throws mechanically before the next flight.