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Ultimate Trainer Design and Test.

is this a good idea?


  • Total voters
    10

Matthewdupreez

Legendary member
#1
hey guys recently i have been thinking of attempting to design the ultimate trainer plane, with exceptional characteristics.
here are some of my goals:
- sub 250gram, for those in countries where licenses are required.
- floaty and excellent glide slope.
- stable and minimum stall characteristics..
- easy to build.
- capable of hand launching and gear..
- 3ch for minimum cost and weight.
- Power pack F or B or maybe even A
- approx 1m wingspan.
- hopefully around 1 sheet of dtfb
- UPDATE: Modelled after a real plane
UpDATE - Pusher configuration.

please let me know if you have any more to add.
 
Last edited:

JasonK

Participation Award Recipient
#3
power pack F/B are likely to big for your targeted plane. If you build a FT TT as light as possible, you can get it under 250g for the 3 channel version and at that point... other then the 1 sheet of foamboard, it meets your goals.
 

JasonK

Participation Award Recipient
#4
with a 2s 650mAh lipo, my 3 channel build of the TT is 247g (and it has had repairs and extra BBQ sticks/glue/tape to make it stronger). with a 6x4 prop that will do well for a trainer.
 

Matthewdupreez

Legendary member
#5
power pack F/B are likely to big for your targeted plane. If you build a FT TT as light as possible, you can get it under 250g for the 3 channel version and at that point... other then the 1 sheet of foamboard, it meets your goals.
oops forgot the one point... updated now
 

Matthewdupreez

Legendary member
#9
why? what value does this add for a trainer?

edit: it seems like a response to the TT filling the initial request and not wanting it to.
maybe maybe not, but also i've noticed that some people don't want to build the tt as their first plane because it doesn't resemble a real plane.
 

Ketchup

4s mini mustang
#11
While a pusher will make it harder to break props, if you make it a tractor it would be much easier to model it off of an existing aircraft (there are many more tractor configuration airplanes, so more to choose from).
I would suggest working with at least one experienced designer, builder, and pilot on this one. From my knowledge you are a bit new to all this, and having both very experienced perspectives and a beginner perspective would be nice when designing a beginner plane.
People will probably have more access to a power pack B equivalent (a lot of cheap motors and electronics match the B pack) but it might be too heavy for a sub 250 plane. The A pack would work best for that, and tbh you might be going too big with 1 meter. You said you wanted it to be based off of a real plane, and it might be hard to make a scale or semi scale plane that has a 1m wingspan under 250 grams, it would be even harder on a 3s setup with a power system larger than an A pack.
Also, about it being based off of a real plane, from what I have seen that isn't really what deters people from the tiny trainer. It is more that it doesn't look "cool", not that it doesn't look like a real plane. Basing it off of a real plane would definitely help a bit, but to not deter people, just don't make it look too boring (sorry for not being more specific about that).
 

Matthewdupreez

Legendary member
#12
c
While a pusher will make it harder to break props, if you make it a tractor it would be much easier to model it off of an existing aircraft (there are many more tractor configuration airplanes, so more to choose from).
I would suggest working with at least one experienced designer, builder, and pilot on this one. From my knowledge you are a bit new to all this, and having both very experienced perspectives and a beginner perspective would be nice when designing a beginner plane.
People will probably have more access to a power pack B equivalent (a lot of cheap motors and electronics match the B pack) but it might be too heavy for a sub 250 plane. The A pack would work best for that, and tbh you might be going too big with 1 meter. You said you wanted it to be based off of a real plane, and it might be hard to make a scale or semi scale plane that has a 1m wingspan under 250 grams, it would be even harder on a 3s setup with a power system larger than an A pack.
Also, about it being based off of a real plane, from what I have seen that isn't really what deters people from the tiny trainer. It is more that it doesn't look "cool", not that it doesn't look like a real plane. Basing it off of a real plane would definitely help a bit, but to not deter people, just don't make it look too boring (sorry for not being more specific about that).
cool, that sounds good, and yea i also meant that they don't like boring looking planes, it must look cool, i think everyone here likes cool planes
 

JasonK

Participation Award Recipient
#13
c

cool, that sounds good, and yea i also meant that they don't like boring looking planes, it must look cool, i think everyone here likes cool planes
part of what makes the TT 'boring' (If that is how you see it), is the very stuff that makes it a good trainer. So the less 'boring' you make it... the less likely it makes a good trainer.

Also, if you want to model off of a real aircraft, [nearly] none of them are 3 channel. If you want something that is a 'real' aircraft design, 3 channel, and a pusher... good luck... especially finding one with good trainer tenancies.
 

JasonK

Participation Award Recipient
#14
On the pusher vs tractor
- tractors on a trainer are going to have the thrust line below the wing and any throttle -> pitch coupling should be throttle -> positive pitch (and sometimes even have some down thrust to counter act this)
- pusher planes almost all have the thrust line above the CG and closer to the wing (outside of a dual boom or a few other design that let the motor be better in line with the CG), if not setup correctly, they will have throttle to negative pitch coupling. (if setup correctly they still push the plane down, but without pushing the nose down). Pusher planes will also be harder to hit the weight goal because you need more material to work around the prop when building your tail boom (instead of straight out, you typically go under or 2 booms to go around)

Instead of a list of "it needs all of this," I would suggest prioritizing your goal list and start coming up with some design ideas.

One thing you can do is get the total weight expected for all of your electronics (say 10g for a receiver, 5g each for 2 servos, ESC, battery, motor, prop) subtract that from your max goal weight, and that will leave you with a mass goal for airframe construction, which will let you estimate how much foam you can use... remembering you want your WCL to be in the trainer range... which means for a 250g plane, is going to be either in the 170 sq.in. [6.9 WCL] to 210 sq.in. [5 WCL] or 170 to 185 [6 WCL] ranges - different sites give different WCL suggestions for a trainer sized plane). If we use the highest WCL from that, we get 170 sq.in., for a single layer of ROSS/DTFB, that is ~33g (170/600*115g), the TT's 2 channel Airfoil is about 1.5 thicknesses total, so just your wing's foam is going to be around 45g.

So, taking the parts I have sitting here as a quick reference:
  • 10g - receiver (most of mine are about 8, but this gives some room)
  • 10g - 2x 5 gram servo
  • 18g - A pack motor
  • 28g - FT 20A ESC w/XT-30
  • 50-55g - wing (after glue/tape)
  • 40g - 2s 650mAh Lipo (55g for the 3s version)
  • 4g - propeller
so we are at 165+g for just the 'required' bits, you still need to build a fuslage, tail, account for the motor mount/firewall, pushrods, control horns, etc. Very doable, but you need to consider what your doing with every bit of glue/foam/etc to make sure your not being wasteful in reaching that goal.

to get that goal wing size at a 11:1 aspect ratio you would want a wing approx 11cm in cord and 100cm in wingspan (which gets you your 1m wing span)
 

Matthewdupreez

Legendary member
#15
On the pusher vs tractor
- tractors on a trainer are going to have the thrust line below the wing and any throttle -> pitch coupling should be throttle -> positive pitch (and sometimes even have some down thrust to counter act this)
- pusher planes almost all have the thrust line above the CG and closer to the wing (outside of a dual boom or a few other design that let the motor be better in line with the CG), if not setup correctly, they will have throttle to negative pitch coupling. (if setup correctly they still push the plane down, but without pushing the nose down). Pusher planes will also be harder to hit the weight goal because you need more material to work around the prop when building your tail boom (instead of straight out, you typically go under or 2 booms to go around)

Instead of a list of "it needs all of this," I would suggest prioritizing your goal list and start coming up with some design ideas.

One thing you can do is get the total weight expected for all of your electronics (say 10g for a receiver, 5g each for 2 servos, ESC, battery, motor, prop) subtract that from your max goal weight, and that will leave you with a mass goal for airframe construction, which will let you estimate how much foam you can use... remembering you want your WCL to be in the trainer range... which means for a 250g plane, is going to be either in the 170 sq.in. [6.9 WCL] to 210 sq.in. [5 WCL] or 170 to 185 [6 WCL] ranges - different sites give different WCL suggestions for a trainer sized plane). If we use the highest WCL from that, we get 170 sq.in., for a single layer of ROSS/DTFB, that is ~33g (170/600*115g), the TT's 2 channel Airfoil is about 1.5 thicknesses total, so just your wing's foam is going to be around 45g.

So, taking the parts I have sitting here as a quick reference:
  • 10g - receiver (most of mine are about 8, but this gives some room)
  • 10g - 2x 5 gram servo
  • 18g - A pack motor
  • 28g - FT 20A ESC w/XT-30
  • 50-55g - wing (after glue/tape)
  • 40g - 2s 650mAh Lipo (55g for the 3s version)
  • 4g - propeller
so we are at 165+g for just the 'required' bits, you still need to build a fuslage, tail, account for the motor mount/firewall, pushrods, control horns, etc. Very doable, but you need to consider what your doing with every bit of glue/foam/etc to make sure your not being wasteful in reaching that goal.

to get that goal wing size at a 11:1 aspect ratio you would want a wing approx 11cm in cord and 100cm in wingspan (which gets you your 1m wing span)
thanks for the info.
 

quorneng

Master member
#16
For a trainer there is another characteristic to consider - how well does it bounce!
Just knocking bits off is one thing but if a hard impact weakens the structure then repairs are more difficult particularly for the less experienced.
So the question is although the 'lightweight' construction resulting from keeping below 250 g may mean it flies well but does it actually make a better trainer?
I have a number of below 250 g planes but I am not sure their flight characteristics make them particularly good trainers
 

Matthewdupreez

Legendary member
#18
For a trainer there is another characteristic to consider - how well does it bounce!
Just knocking bits off is one thing but if a hard impact weakens the structure then repairs are more difficult particularly for the less experienced.
So the question is although the 'lightweight' construction resulting from keeping below 250 g may mean it flies well but does it actually make a better trainer?
I have a number of below 250 g planes but I am not sure their flight characteristics make them particularly good trainers
yes yes that is a very important i also need my planes to bounce more