First scratch-built plane build, need help - RC Groups
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Nov 09, 2017, 02:24 AM
WW5
WW5
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Help!

First scratch-built plane build, need help


So I'm starting my first scratchbuilt rc aircraft and I need some help. I have 5 micro 9g servos and an 40amp esc with an electric 135OKV brushless motor that I got from one of my crashed planes and I was wondering if anybody knows very simple build plans for an 25 to 30 in wingspan trainer (Ish) plane that is suitable with the type of servos, motor, and so on that I have. Also If anyone has recommendations for tools that are cheep that are able to cut foam well.

With kind regards,

Ethan
Last edited by WW5; Nov 09, 2017 at 02:35 AM.
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Nov 09, 2017, 02:57 AM
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Extreme Sports's Avatar
You are going to have to tell us more about the motor. The Kv on its own says very little about how much power the motor can transfer to the prop. Motor mass is probably the simplest, and the bell diameter and length are also helpful. Just be clear what length you measure.

That said, if the motor is a good match with the ESC, then your whole power combination is probably too much for a 30" span plane. More suited to a 40 - 50" span or thereabouts.

For comparison a good motor for the size plane you want would weigh about 25g and should handle around 10A or about 100W. You'd not want your lipos to weigh much more than about 100g - preferably 60 - 80g. How do these rough guidelines compare to your components?

The servos sound fine. 9g is suitable for a wide range of planes.

The only tool you need to cut foam is a very sharp knife and lots of spare blades. Later on you might want to look into building a hot wire cutter but a knife is all you need to start building.

Good luck
Last edited by Extreme Sports; Nov 09, 2017 at 03:04 AM.
Nov 09, 2017, 03:09 AM
WW5
WW5
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WW5's Avatar
Quote:
Originally Posted by Extreme Sports
You are going to have to tell us more about the motor. The Kv on its own says very little about how much power the motor can transfer to the prop. Motor mass is probably the simplest, and the bell diameter and length are also helpful. Just be clear what length you measure.

That said, if the motor is a good match with the ESC, then your whole power combination is probably too much for a 30" span plane. More suited to a 40 - 50" span or thereabouts.

For comparison a good motor for the size plane you want would weigh about 25g and should handle around 10A or about 100W. You'd not want your lipos to weigh much more than about 100g - preferably 60 - 80g. How do these rough guidelines compare to your components?

The servos sound fine. 9g is suitable for a wide range of planes.

The only tool you need to cut foam is a very sharp knife and lots of spare blades. Later on you might want to look into building a hot wire cutter but a knife is all you need to start building.

Good luck
Thank you, I will tell you the power and dimensions of the motor later.
Nov 09, 2017, 07:33 AM
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Extreme Sports's Avatar
Mmm. I noticed another post you made where you mention that you crashed your Flyzone Sensei, which, it seems also uses 5 servos and a motor with a KV of 1350.

Sorry to be blunt, but surely you are not expecting a 25" to 30" plane to fly with the electronics from a 58" plane? That is a bit like wanting to fit a 250hp outboard from a ski boat into your little 5hp fishing tender (Yes...it will break...if it does not sink first). The Sensei battery alone probably weighs more than a full 25" plane ought to weigh.

More than happy to help, but we need to use the same basic laws of physics

Nov 09, 2017, 08:11 AM
Registered User
Id agree youd probably want something a little larger, planes dont like having weight added to them,t hey are designed for a particualr all up flying weight, at weight and they become harder to fly and dont fly as slow.

If you want a slow flying plane you may need to go larger. Look at flitetest stuff they have a few planes in the full sie series that may be suitable.

the other option is a big pizza box flier :-)
Nov 09, 2017, 09:51 AM
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Extreme Sports's Avatar
That size power set up opens up lots of options! It is at the big end for a scratch built depron style foamie, but would work really nicely with foamboard or correx. As mentioned, Flitetest is a good place to start, or, if you can get 2mm correx, there are a bunch of designs that could work (I can point out some if you want to try correx...some folk turn their noses up at it ). Construction techniques are very similar for the two materials, with correx probably giving a better airfoil and strength.
Nov 09, 2017, 12:21 PM
WW5
WW5
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Quote:
Originally Posted by Extreme Sports
That size power set up opens up lots of options! It is at the big end for a scratch built depron style foamie, but would work really nicely with foamboard or correx. As mentioned, Flitetest is a good place to start, or, if you can get 2mm correx, there are a bunch of designs that could work (I can point out some if you want to try correx...some folk turn their noses up at it ). Construction techniques are very similar for the two materials, with correx probably giving a better airfoil and strength.
Sorry I'm still pretty new to the hobby and kind of oblivious.
Nov 09, 2017, 12:51 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
What type of foam is available to you where you live ? If you live in the USA or Canada , you can use cheap foam board from a Dollar Store .

A good rule-of-thumb for salvaged electronics is : for the same performance , build a plane with the same flying weight and dimensions as the plane the electronics came out of . If you want 3D performance ( hanging on the prop ) , make it significantly lighter weight . If you want very slow flight , make it with as much wing area as is reasonably possible ...... RELATIVE to the flying weight ( light wing loading ) .



Here is a home made plane built SPECIFICALLY for the single purpose of flying slowly , so it was made with very light wing loading :



FT Old Fogey-ish with 60" wingspan (1 min 56 sec)
Nov 09, 2017, 08:19 PM
WW5
WW5
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WW5's Avatar
Quote:
Originally Posted by balsa or carbon
What type of foam is available to you where you live ? If you live in the USA or Canada , you can use cheap foam board from a Dollar Store .

A good rule-of-thumb for salvaged electronics is : for the same performance , build a plane with the same flying weight and dimensions as the plane the electronics came out of . If you want 3D performance ( hanging on the prop ) , make it significantly lighter weight . If you want very slow flight , make it with as much wing area as is reasonably possible ...... RELATIVE to the flying weight ( light wing loading ) .



Here is a home made plane built SPECIFICALLY for the single purpose of flying slowly , so it was made with very light wing loading :



https://www.youtube.com/watch?v=mGLj43y-VUM
To answer your question about the dollar store foam, I live in America.

And thank you for the advice
Nov 09, 2017, 09:44 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
I recommend building the trainer-ish EzFly . It is very stable and can be slow flying if built with light wing loading , and has the added bonus of protecting your motor/prop . The airframe can easily be scaled up to be suitable for heavier electronics . What is the size/weight of your motor and battery ?



Here is my standard size EzFly :


Copy of EzFly with under-cambered wing (1 min 57 sec)







Here is my scaled up EzFly for heavier electronics :


( slightly ) better video of 60" wingspan EzFly (2 min 32 sec)






Both were made out of Dollar Store foam board .
Nov 10, 2017, 02:28 AM
WW5
WW5
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Quote:
Originally Posted by balsa or carbon
I recommend building the trainer-ish EzFly . It is very stable and can be slow flying if built with light wing loading , and has the added bonus of protecting your motor/prop . The airframe can easily be scaled up to be suitable for heavier electronics . What is the size/weight of your motor and battery ?



Here is my standard size EzFly :


https://www.youtube.com/watch?v=VxaUadvhgbc






Here is my scaled up EzFly for heavier electronics :


https://www.youtube.com/watch?v=Q1byiR_7hCU





Both were made out of Dollar Store foam board .
I think the motor will be too big but I will just buy a new one.
Nov 10, 2017, 01:46 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by WW5
I think the motor will be too big but I will just buy a new one.
You can scale an airframe up to suit the motor ...... but if you want to build a standard size EzFly , let me know and I can link you to recommended electronics . And I can guide you through the whole build process .
Nov 10, 2017, 03:35 PM
Flying a Falcon or a 3D plane.
fauconnier's Avatar
Take a look at the videos on the foamies scratchbuilt page: Foamboard Scratchbuild University
There are few models for a 40 esc combo and 9 gr. servos.
Nov 11, 2017, 06:33 PM
Registered User
Quote:
Originally Posted by fauconnier
Take a look at the videos on the foamies scratchbuilt page: Foamboard Scratchbuild University
There are few models for a 40 esc combo and 9 gr. servos.
what sort of motor fits a 40a esc?

just curious, cause i robbed my trex 450 40a esc for my flitetest t28, although i doubt its pulling upto 40a as its propped as suggested. anyway....


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