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Mar 02, 2018, 07:33 AM
Registered User
agfrag's Avatar
Help!

Returning to hobby - pusher V tail brushless Foamie build electronics help sought.


Hello everyone. I am returning to the RC world after a long hiatus (10+ years) and boy have things changed in the electronics arena! So, I am asking for some help with my first build, a foamy pusher with FPV.

I'm thinking about a 30 inch wingspan with a V tail (see pic) but I'm a bit lost electronics wise.

Any advice would be appreciated, and I know I'm asking a lot, but but here is what I think... maybe... I'm getting so far:

Receiver: FrSky D4R-II 4 channel. I have now a FrSky Taranis transmitter, but I also have an IrangeX IRX4 4 in 1 module, some I'm not stuck on a FrSky receiver.

Servos: Two Hitec HS-53 budget Feather.

ESC: Maybe a Turnigy 5A 1S brushless?

Brushless motor: No Clue

Prop: No clue, but right now the distance between the two V tail support rods is 4 inches, so maybe a 3 inch prop?

I don't know what the weight will be, and I also have a supply of the old blue1/4 inch foamboard, and some 2mm Coroplast, and a ton of carbon fiber rods, tubes, control wire,etc.

I want it to fly as slow as possible, so lightness is cool, and low cost is cool too (lol), I'd like to aim for about $100, but that might be totally unrealistic, and 1S battery is the goal (I have 4 new 1200ma lipos ready to go) but if I have to go with 2S, I'll go that way.
Last edited by agfrag; Mar 02, 2018 at 07:44 AM. Reason: typo
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Mar 02, 2018, 12:16 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by agfrag
Hello everyone. I am returning to the RC world after a long hiatus (10+ years) and boy have things changed in the electronics arena! So, I am asking for some help with my first build, a foamy pusher with FPV.

I'm thinking about a 30 inch wingspan with a V tail (see pic) but I'm a bit lost electronics wise.

Any advice would be appreciated, and I know I'm asking a lot, but but here is what I think... maybe... I'm getting so far:

Receiver: FrSky D4R-II 4 channel. I have now a FrSky Taranis transmitter, but I also have an IrangeX IRX4 4 in 1 module, some I'm not stuck on a FrSky receiver.

Servos: Two Hitec HS-53 budget Feather.

ESC: Maybe a Turnigy 5A 1S brushless?

Brushless motor: No Clue

Prop: No clue, but right now the distance between the two V tail support rods is 4 inches, so maybe a 3 inch prop?

I don't know what the weight will be, and I also have a supply of the old blue1/4 inch foamboard, and some 2mm Coroplast, and a ton of carbon fiber rods, tubes, control wire,etc.

I want it to fly as slow as possible, so lightness is cool, and low cost is cool too (lol), I'd like to aim for about $100, but that might be totally unrealistic, and 1S battery is the goal (I have 4 new 1200ma lipos ready to go) but if I have to go with 2S, I'll go that way.
For your first build I recommend building an existing , proven , well supported plane with an active RC Groups thread in this forum . The thread will have plans for building the airframe , electronics recommendations , and plenty of help if you need it . Another forum you can look at is this one for micros : https://www.rcgroups.com/scratchbuil...cro-models-85/ if you want to use your 1S batteries .

A very good way to build a lightweight slow flyer is by using a "brick" : all-in-one receiver/ESC/servos unit . If your multi protocol module can use a FlySky receiver , you can use inexpensive bricks from WL Toys aircraft , such as this one with a brushed ESC :
https://www.banggood.com/WLtoys-V911...r_warehouse=CN
or this one :
https://www.banggood.com/WLtoys-F949...r_warehouse=CN
or you can buy the entire plane to scavenge all the parts ( motor/prop etc ) :
https://www.banggood.com/WLtoys-F949...r_warehouse=CN


There are also bricks available for other protocols such as DSMX and Tactic SLT , but they are more expensive .
Last edited by balsa or carbon; Mar 03, 2018 at 08:38 PM.
Mar 03, 2018, 06:05 PM
Registered User
JabiruAbe's Avatar
Your gonna need a heck of a lot more than a 5A 1S ESC in my opinion... Try a 610mah 2S and a 1306 motor.
Mar 04, 2018, 08:30 AM
Registered User
If you intend to fly outdoors:
It's so much easier to work with a larger airplane with correspondingly beefier electronics (the reasons are too numerous to list here) . You can achieve very low wing loading easier at larger scale, too.
I'd recommend the plane design you posted at 45 inch span or more (again, without getting into all the reasons).
Mar 04, 2018, 02:28 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
FYI , those Hitec HS-53 servos operate on 4.8v - 6v .... so they will not work with a 3.7v - 4.2v 1S battery .
And Coroplast is too heavy to be suitable for a lightweight 1S powered slow flyer .
Have you already constructed your v-tail airframe ?
Last edited by balsa or carbon; Mar 04, 2018 at 04:44 PM.
Mar 04, 2018, 07:12 PM
Registered User
agfrag's Avatar
Thanks for the input Balsa or carbon, JabiruAbe, and Nuteman.

I have picked up an 18A ESC, a "Diatone" DS 1408 4000KV brushless motor, a Tattu 2S 650mah battery, and a 4 x4R(sic) prop. I have constructed my plane, but out of blue foamcore, as you are correct balsa or carbon, the Coroplast is a lot heavier than the foam, and my weight with all the electronics now is about 8oz.

With my wing surface of 180 in sq (6x30in), I'm seeing 6.5oz/sq. ft. wing loading, which is a bit on the heavy side. Also, the balance is a bit more toward the middle of the wing than I prefer.

So, thanks for the comment on the ESC, and on the wing size. I am going to be creating a larger wing (as close to 48in as I can get) and longer front to back (chord?), not sure at this point how much though, maybe 8 inches?

If I allow for another ounce of foam, then my loading at 9 oz and a 8x48 wing goes down to 3.38oz/ft sq.

I'll see how the balance ends up after the next build!
Last edited by agfrag; Mar 04, 2018 at 07:15 PM. Reason: typo
Mar 04, 2018, 07:31 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by agfrag
Thanks for the input Balsa or carbon, JabiruAbe, and Nuteman.

I have picked up an 18A ESC, a "Diatone" DS 1408 4000KV brushless motor, a Tattu 2S 650mah battery, and a 4 x4R(sic) prop. I have constructed my plane, but out of blue foamcore, as you are correct balsa or carbon, the Coroplast is a lot heavier than the foam, and my weight with all the electronics now is about 8oz.

With my wing surface of 180 in sq (6x30in), I'm seeing 6.5oz/sq. ft. wing loading, which is a bit on the heavy side. Also, the balance is a bit more toward the middle of the wing than I prefer.

So, thanks for the comment on the ESC, and on the wing size. I am going to be creating a larger wing (as close to 48in as I can get) and longer front to back (chord?), not sure at this point how much though, maybe 8 inches?

If I allow for another ounce of foam, then my loading at 9 oz and a 8x48 wing goes down to 3.38oz/ft sq.

I'll see how the balance ends up after the next build!
4000kv is a VERY high revving motor for a slow flyer , it may be like trying to go 3mph on your motorcycle ..... in 3rd gear . For a slow flyer , a more suitable motor would be a lower kv with a larger prop ..... that would be like trying to go 3mph on your motorcycle .... in 1st gear .

The greater the wing area ( span & chord ) , the lighter the wing loading will be ..... so I would increase the chord as much as possible . Here is a slow flyer I've made with a 60" (span) X 20" (chord) wing :


FT Old Fogey-ish with 60" wingspan (1 min 56 sec)





BTW , that ↑ plane uses a 750kv motor with an 11" prop .
Last edited by balsa or carbon; Mar 04, 2018 at 07:42 PM.
Mar 04, 2018, 07:34 PM
treefinder
springer's Avatar
I have built a couple dozen foamies in the 28-35" span and nearly all I powered with a 1700kv 24 gram "blue wonder" type motor, 10-12amp esc, 7x6 prop and an 850mah2s Lipo. That combination works well with all types of planes from a 60" span motor glider (OSG), to high wing monoplane (OSF), low wing monoplane (OSP), biplane (OSB), flying wing (OSE), combat planes, etc. That combo has a speed range that works for floater to racer and gets from 5-20 minute flight times. (The 5 is WOT combat flying). Hobby king or banggood has all the stuff.

Your TX and RX are fine, any 9 gram servo will work (Hitec is too pricy for me, I like hextronik hxt900) . Your 18 amp esc will work as long as its not too large to fit in fuse.

I assume you have twin booms, I would consider spreading them to fit the 7" prop. The small dia. prop will have to spin a lot faster to give decent thust and I doubt you will have the floater you want with it. If you click on my username and go to my blog, there are links to the build threads of the planes I mentioned. You might find some useful tips and ideas in them.
Mar 05, 2018, 10:43 AM
Registered User
agfrag's Avatar
Wow, Balsa or Carbon, I could almost outrun that plane!

Question: Is there any reference or information somewhere which would indicate good combinations of plane weight to motor/esc choices? I've been looking at a lot of the posts, but naturally, they tend to focus on particular topics.

treefinder, I understand a bigger prop, but I don't know what a "blue wonder" motor is, and when you mention using a 7 inch prop, are you saying it would work with my current 1408 motor? And when you say "9 gram servo" are you referring to the weight of the servo, or the force it can provide at the end of the control arm in Newtons, or ?

And can anyone suggest a plane size which would be workable with a 1408 4000kv motor? I have much to learn!
Mar 05, 2018, 01:24 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by agfrag
Wow, Balsa or Carbon, I could almost outrun that plane!

Question: Is there any reference or information somewhere which would indicate good combinations of plane weight to motor/esc choices? I've been looking at a lot of the posts, but naturally, they tend to focus on particular topics.

treefinder, I understand a bigger prop, but I don't know what a "blue wonder" motor is, and when you mention using a 7 inch prop, are you saying it would work with my current 1408 motor? And when you say "9 gram servo" are you referring to the weight of the servo, or the force it can provide at the end of the control arm in Newtons, or ?

And can anyone suggest a plane size which would be workable with a 1408 4000kv motor? I have much to learn!
Simplified general rule of thumb : for a plane that you want to fly slowly , use a lower kv motor with a larger diameter & lower pitch prop ( like riding around in first gear : easy to go slowly , torque when you need it , but top speed will be limited ) .
For a plane that you want to fly fast ( like a parkjet F15 , F22 , etc ) , use a higher kv motor with a smaller diameter & higher pitch prop ( like riding around in third gear : difficult to go slowly , not much torque , but much greater top speed ) .

Make your choices in this order :
decide if you want your plane to be slow/fast flying , and what type of performance you want ( mild climb , unlimited vertical , etc ) .
choose an appropriate motor for your slow/fast flying and performance choices .
choose a prop that's appropriate for your motor , battery voltage , speed choice and performance choice .
choose an ESC that's appropriate for your motor/prop/battery's amp draw .
choose a motor/prop/battery/ESC for the flying WEIGHT of the plane , not for the SIZE of the airframe .

"Blue Wonder" style are usually about 24 gram 2730 bell motors , available in kv ranging from 1200kv to 3000kv . Like Springer , my favorite is also the 1700kv hexTronik from HobbyKing .

For servos , 9 gram usually refers to the weight .

I recommend setting your 4000kv motor aside ( save it for a future speedster ) , and getting a lower kv motor with a larger-diameter/lower-pitch prop for your current plane . You can raise the motor higher for prop clearance ( see photo below ) .




Here is a speedster I made , 3400kv motor with a small 6x4 prop :



Dollar Tree foam board SkyFun ( ish ) (4 min 6 sec)
Mar 05, 2018, 01:34 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Here is a 40" wingspan version of the Old Fogey-ish that uses a 1500kv Blue Wonder style motor , be sure to watch the landing at the end :



Lightweight 40" wingspan FT Old Fogey-ish (2 min 58 sec)
Mar 05, 2018, 09:16 PM
Registered User
agfrag's Avatar
That is really floaty for a 40 incher! The wing profile is extreme! Really nice.

Yup, I thought you were gonna catch it at the end it was going so slow...

I will be shopping for a lower KV motor, and a bigger prop!
And Springer, really nice planes, I hope to achieve your level of build quality some day!
Mar 05, 2018, 11:03 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by agfrag
That is really floaty for a 40 incher! The wing profile is extreme! Really nice.

Yup, I thought you were gonna catch it at the end it was going so slow...

I will be shopping for a lower KV motor, and a bigger prop!
And Springer, really nice planes, I hope to achieve your level of build quality some day!
Couldn't really catch it since I had the phone/camera in my left hand , and the transmitter in my right hand .....

If you have any more questions when you get your new motor/prop ..... let me know , I'll be glad to help !
Mar 06, 2018, 10:16 AM
treefinder
springer's Avatar
"And Springer, really nice planes, I hope to achieve your level of build quality some day!"

Thanks, amazing what you can do with building insulation!
Mar 07, 2018, 12:57 PM
Scratch building addict
rotagen's Avatar
Here's my 2 cents for a 30 inch wingspan slow flyer, I have many near this.

Hobby king has a motor-finder app on front page and I think? you can put in weights in grams, or just search online.

Motor: 30 gram (or slightly heavier) 1500 KV (1400-1700 is OK) outrunner.
ESC: 20 Amp but 15 Amp is probably enough and will be lighter.
Prop: 8 inch slow fly prop.
Servos: HXT 500 - cheap and by far more reliable than anything smaller I've found.
Receiver: I bought my transmitters based on cheapness and lightness of the receivers. So I
bought Orange, and Frsky. The frsky I simply soldered in the "hack" module into
much cheaper transmitters. Both of these systems offer a super light 4 channel Rx about 2.5 cm in length.
Battery: 3S 500maH

Key to keeping it light: mark the CG spot on the wing early, test as you go along by taping components etc.
I learned this the hard way - otherwise you are adding lots of lead to nose or tail.
Last edited by rotagen; Mar 07, 2018 at 01:06 PM.


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