yet another scratch-built trainer

by ishj | December 6, 2013 | (2) Posted in Projects

 

sorry for those excess pics...

 i have no plane to compare it to...its a 4ch trainer with dihedral, elevon mixing , but regular wings... i just didn't want to cut out ailerons... my electronics are on the way from hk, as there's no hobbyshop in Mauritius. this is my first plane and i'd like to get some feedback on how it flies comparative to others and how to improve... btw sorry for the camera pics... my scanner broke. its easy to build, with high density eps foam of 1/2 inch thickness...

Electronics:

Turnigy 2200mAh 3s 25c

NTM Prop Drive Series 28-30 1200kv / 400w 

9X5 Propellers
Turnigy TG9e 9g / 1.5kg / 0.10sec Eco Micro Servo 
 Prop Saver w/ Band 3mm
Metal Push Rods M2.2xL300 
 Hobby King 30A ESC 3A UBEC

 

 

 

 

COMMENTS

Exhodus on December 27, 2013
Have some advice for you, if you would take it.
First, your diherdar is waay to much its gonna wobble and dutch roll on turn, you might read the 30 degrees somewhere but that is not for one wing but for the two together, if one is sitting flush, that means 15 degrees per wing, wich is still quite much, but should be ok.

Second, the tailfeathers or rather the complete tail end, sorry to say this but you should loose it completely, these patched on contol surfaces with a quite disproportionate tail smells disaster for me.
Check this article it is mighty useful http://flitetest.com/articles/Design_Parameters_for_Scratch_Built_Airframes

I would urge you to design conventional looking tail feathers from a thin material, with correct proportions to your wing, also check the lenght of the tail.
Elevont mixing wont do you much good because there isnt a long enough level on the horizontal stabilizer to actually force the plane with such a large wingspan to turn, especially with dihedral as it will naturally oppose the turning movement. 3 channel control is good with dihedral and it is easier on the beginner pilot as well, just wire the rudder to the aileron channel.

One more very important thing, as you will have no idea where the CG is located, when ready and everything is installed, set your cg location to 30% of the wing chord, make it balance there (a touch nose heavy might do you some good) than do glide tests, just toss the plane and look how it sails if it pitches up than move the cg forward, if it dives to the ground quickly than move the cg back. Important thing, that you should do this with the battery and everything installed first!

Dont take this the wrong way, I dont want to tell you how to do things, just some friendly advice. There are some golden rules in aviation that should be followed and it is very hard to grasp all of them on a scratchbuild airplane especially if you are new to this field.
My experience is either the pilot or the plane should be very solid to have a good time when flying, so if you are just starting this hobby I would advise you to opt for some well tried out desing that wont give you any surprises, there are a bunch of these here at FT.
Designing your own plane is a good challenge but should be started after you are familiar with the rules of flight and have enough flying time under your belt that you can handle a misbehaving plane! Belive me, I learned it the hard way!


Log In to reply
ishj on January 1, 2014
thanks for the advice.. I'm a complete noob concerning scratch building, and I will reduce the angle of the wings. As for the thinner tail, I do not think that I will be able to make one, I have access to only 1/2 inch eps foam, unfortunately. :(

Log In to reply
anonymous rc pilot on January 19, 2014
I've run into the same problem using foam what I did set my foam sheet between two wood rulers then sliced a thin 1/8in sheet using rulers to guide my knife then simply cut out the shapes necessary (remember to reinforce with some light balsa or other material) I wouldn't recommend this technique because it is difficult to get a even cut. Anyways you could use cardboard foam-board a some other light thin material, but whatever you do keep tail-weight in mind.
Log In to reply
rcspaceflight on December 27, 2013
That's a lot of dihedral. And a lot of air is going to spill right off the wing tips and give you very little lift.
Log In to reply
zev on December 28, 2013
basically as Exhodus and others said, you will need less dihedral, a tail made of thinner material (and probably with a classic rudder and elevator design. no need for the elevons, rudder elevator and throttle will be plenty for your first flight, and elevons on the tail wont really work too well anyway). another thing you will need is overhang in front of the wing, this is necessary to get the CG in the correct place. you do not want to fly a tail heavy plane. also, for that heavy and powerful electronics, I recommend a 40-60 inch wing span to get nice flying characteristics.

brave to try designing your first airframe. the first one I built that flew was my own design, it can be done, just remember to glide test, always glide test.
Log In to reply
angus on December 27, 2013
Nice to see some original aircraft. I hope you have a video cam so we can see it with the electronics installed, flying around Mauritious.
Log In to reply

You need to log-in to comment on articles.


yet another scratch-built trainer