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Another Tiny Trainer Build “Foamasaurus Wreck”

FDS

Well-known member
#1
So tonight I started with just the fuselage and control rods in, here’s it coming alive with the first servos live, rudder and elevator plus my electrics up and running. This was my first small RX/bec build, when I stopped RC cars the ESC’s and RX’s were huge!

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I built my first big wing, started with the glider wing since I won’t use that as much, so mistakes on that won’t matter.
Here it is with everything in place, just the 4ch wing to build.

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The motor I got is too big, I know sweet FA about the sizing of brushless motors but it will fit the simple scout or I will just make a new bulkhead, then set the throttle up to compensate for the bigger motor. I ordered what I think is the right size too, as I don’t want too much weight forward. I put the servos slightly further back to compensate already.
I have either 9g or 3.5g servos for the ailerons, which should I use?
Couldn’t find 5g ones easily and figured the 3.5’s would manage with likely low rates of surface movement and slower speed.
 
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d8veh

Well-known member
#2
The motor will be OK, but there is a potential problem. If the motor is large compared with the size of the firewall/bulkhead and you used hot-melt glue to glue the firewall to the fuselage, the heat can melt the glue, which can make it detach in flight. You should therefore use epoxy to glue the firewall.

If you use a 2S battery and a 10x5 propeller or smaller, your motor won't get hot. Ifyou want to use a 3S battery, use a 9×5 prop. I'm guessing that your motor is one of those cheap A2212 1000kV motors. If not, tell us what it is if you need advice on how to keep it cool.
 

FDS

Well-known member
#3
Great. I have got a smaller motor coming, this is the one that was too big.
I have a 6x3 prop coming as that was what was in the spec sheet, which I asssume will work with the smaller motor this one, which I hope is right. Took the spec from the FT power pack then looked for just the motor.
If we could just get the FT packs here for the price they are in the USA it would be much easier.
I will be starting off on 2s, as I have that pack already. Thanks for the tip on the firewall, Epoxy is always in my toolbox so I have it if I need it.
Making the 4ch wing now, just finished a simple scout wing with the boy, rest of my TT is now racing red. Pictures in a bit.
 

d8veh

Well-known member
#4
I think that gold motor would be OK with 2S. With 3S, you'd have to be more careful with the throttle. I have one in my Scout, and it climbs vertical really quickly on full power with the 3S battery.
 

FDS

Well-known member
#5
Putting it in the Scout then! That will also stay 2s for now since neither of us have many hours in the logbook.
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Base red done, striping will have to wait. Advanced wing is now finished bar the ailerons and servos, will do those tomorrow.
 

donalson

Active member
#7
the B pack motor will work and fit fine on the tiny trainer... the only caveat of that is the motor and ESC is a little more weighty... so you'll have to put the lipo further back to get CG right... the weight will also mean a little worse slow flight characteristics... aka it'll have to go a smidge faster to stay up... I use a motor somewhere between the F and B pack (2208 1400kv) on my trainer and I far prefer it to the F pack, more thrust and more efficient on a 2s vs the F pack 3s and handles a bit of weather much better... on a 3s the motor is MUCH more fun

I honestly found the trainer more difficult to fly on the A motor than the F and easier still on this motor...

also you really don't need any thrust angle on the tiny trainer and even less so with the B pack motor....

as for melting the glue... if you are using the proper size prop for the motor based on what cell lipo you are using the motor and ESC won't be an issue nor will the heat to the glue... also the glue isn't really holding the firewall on if you build it properly to FT specs... it's really the tape that is holding it on... that being said I do like to use a bit of hot glue along the power pod vs relying on the skewers for the smaller power pods
 

FDS

Well-known member
#8
Thanks for those extra tips. I have finished everything except the aileron linkage on it now. It’s been named “Foamasurus Wreck” and is getting some artwork added, plus the underside of the sport wing is now yellow.
I will post some video of it’s maiden as soon as the motor arrives and the wind drops.
Planning on being pretty careful with its first flight, running all the controls on the low settings and triple checking the CG. The bigger motor has been snapped up by my son for his Scout, he drew the motor mount for it at school and laser cut his own bulkhead as we scratch built that one.
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Nose art added!
 
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donalson

Active member
#9
haha dig the nose art :)

with the smaller A or even F pack motor make sure to wait for a very calm day... start with the 3ch... make sure to watch FTs preflight checks... also try a few hand launch glide tests with it before flying... I found it didn't like wind with the smaller motors... on the bigger motor with ailerons it can handle more wind but either way wait for that till you're more comfortable flying
 

FDS

Well-known member
#10
Thank you! Been flying the Sport Cub S on 4 channel with safe mode off in preparation.
Got about 40 mins in today in 5-9mph wind.
I am still not convinced I got the right motor, this was the second one I bought, using the specs off the FT one, is it correct or too big? If it’s not right can anyone give me a link for about £10 for one that will work with a 6x4 prop on 2 or 3s?
 

donalson

Active member
#11
that should be about equivalent to the A pack... and flying the spot cub S in advance mode in those sort of winds you should be fine with the trainer...

also look at the thrust chart on the link you sent you'll be wanting to run it on a 6040 prop with either 2 or 3s lipos to get the most thrust from the motor...
 

FDS

Well-known member
#13
Thanks again!
Hopefully getting more flight time on the Cub today. Have to wait and see what happens with the Trainer.
Will buy more motors at the end of the month.
Maiden video all planned, I am making a balancer on Friday when I hit the shop.
Just set up the rudder and elevator rates, end points etc, added some mixes in so when the ailerons are operated I get a bit of elevator, set to sub 20% for now, will see how that works. I found on the Sport Cub it would dip the nose with aileron input in intermediate, which in SAFE doesn’t happen because it gives a little elevator so I replicated that to give me a similar feel on the TT. My Sport Cub is flying great with my Orange tX6i, it bound easily and once I got the servo reverses sorted everything was perfect. The TX6i has better trim and control options than the one in the box so I had to try it.
 
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FDS

Well-known member
#14
My second motor arrived today, this one to recap, and I have a choice of 5x3 or 6x4 prop. I will be adding a prop saver to my set up too. I am intending on running it on 2s to start with, would the 6x4 prop be better at the lower rpm?
The only problem is that the mounting holes on the motor don’t line up with the firewall mounts at all. I am just going to measure it out and drill new ones for now.
I had tried to fly the Cub yesterday but got my trims in a mess and forgot the orientation for safe mode, which combined with insufficient height in a smaller flying space cost me the tail getting torn off 1 min into the first battery. Much swearing and glueing fixed that with a good curing over night. Lesson learned, not flying at that field again now I am trying to get higher and push myself more. It’s great for cruising round in safe mode, not so good for flying “properly.”
In other news I flew 6 batteries today on the acro settings on the Cub today to compensate, it was the best flying day we have had for weeks and there was a glorious sun set to boot.
I had to reach for the safety switch about once per battery, especially once the light started to fade and it was easier to lose the plane in the ground clutter. However I did manage to survive a few barrel rolls, loops and half loops as well as the Immleman turn. I only crashed twice, both at low speeds and with the throttle off. All in all a good day.
Really keen to maiden the TT, all I need to know is which battery/prop combo will work best with that motor and is it juicy enough to get her in the air?
 
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d8veh

Well-known member
#15
I wanted to buy one of those motors, but I can't figure out which way the nut screws. can you confirm which way yours is. Does it screw on a normal right hand thread? Can you tell me exactly which version do you have?
 

FDS

Well-known member
#16
I have the exact one in that link, the cone thing is a regular RH (CW) thread. I can’t see how you fit a prop saver to it, the thread seems all part of the motor housing, it hasn’t got a separate shaft. The thread is 5mm.
 

d8veh

Well-known member
#17
Thanks for that. i just ordered one.

I don't use prop-savers, but I'd say that 15,000 rpm might be a bit fast for one anyway. I've never seen a threaded one, but I guess there's nothing to stop you drilling and tapping one for a 4mm plain shaft.
 

FDS

Well-known member
#18
With a bit of late night peace and quiet, my TT is now pretty much finished, just got to connect the motor to the ESC and get a smaller battery, I can get my 800mah 2s to balance but it’s a bit heavy.
I went with a 6x4 prop on the new motor, when the next storm front has moved through I can use the 15mph breeze at the weekend for a test glide with it all loaded. There’s a good field near town with 3” of soft weeds and dead nettles in, perfect for checking the glide slope and CG. Then it’s a waiting game for calm weather before I maiden it. All the rates are set, low on switch 2 position zero, high on position 1, 30% expo on all 3 control surfaces and a little elevator mix (20%) with the aileron. Any more set up hints welcome. CG is spot on the markers but will obviously change a little with the smaller battery.

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FDS

Well-known member
#19
And the bird is ready to fly.
I hooked everything up today, it’s running and all the set up is done. Test glide next, then maiden. Will try to film the first flight/crash depending on weather and if I have time.
Ordered the wrong batteries as well, so fixed that. On the plus side weather is awful for 5 days so waiting isn’t so bad.
It’s running the second motor with a 6x3 prop, my 6x4 didn’t have an adapter, which will need sorting.
I also rigged a hook to hang it from the wall out the way, the domestic authorities were less impressed than I was.

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FDS

Well-known member
#20
IT FLEW TODAY!
There was a small weather window with very poor light just at sunset today, the wind dropped to about 10mph with 15mph gusts. I had intended a few short test glides as I only have a heavier 800mah 2s pack, which makes her a bit heavy, even with the CG done.
Here’s a short video of progress, with 5 or 6 short hops removed from the video, as they were pretty similar. The added weight of the larger pack means it needs a bit of throttle to stay up, the field was picked because it’s the most overgrown in town and it’s too small to go high over, plus the wind higher up was much gustier. I hadn’t planned a full flight but couldn’t resist trying it, even with the weight on.


After flying I realised the motor was pointing down, altering the thrust angle over the wing, plus the power pod was a little soft. I made a new power pod and refitted it flatter in the fuselage, hopefully this one lasts a bit longer.
I also had a better motor in the box, which I have fitted tonight, it’s a slightly higher KV and I am keeping the 6x4 prop for 2s, I have a 6x3 for running it on 3s. I will look at the prop balance before I fly again, there was a bit of vibration in the motor, which could have been down to the crumpled pod.
Overall I was pleased with how it flew, I have adjusted the aileron rates and expo a little bit, as the pitch was a bit much for lower altitudes.
Obviously flying higher with a lighter battery would have been a lot easier, but the wind was a bit savage and the field is near a road and a few big trees.
Other than the motor pod damage and a few scratches in the paint the rest of the beast is in excellent shape. I am just waiting for proper single figures wind to take it out again.