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Help! First Build questions: (Tiny Trainer) Getting ready to fly!

#1
Hi all. My 17 year old son was looking for a quarantine hobby and decided to build planes. He started with the FT Explorer and the 3 channel wing. After limited success in a local park (successful flight but many obstructions and a broken wing), we took a drive to some wide open spaces and he had some long flights. He has finished the 4 channel wing and is ready to try that next.

I decided I want to join in the fun but with something smaller and more appropriate for limited space AND 55 year old reflexes. My box of goodies from FT Store arrived yesterday morning. Time to build! I decided on the Tiny Trainer and finally found version 1.1 Tiny Trainer plans updated by Dan Sponholz.

The questions:
Firewall plywood:
Other than needing longer screws, is there any downside to using 4 mm plywood? I have lots of good quality 4 mm Bruynzeel Okoume 3 ply BS 1088 rated plywood. I also have some lesser quality 3 mm luan.

Screws: I have an Emax CF2822 1200kV motor. Are the mounting screws for this going to be M3 with the coarse 0.5 pitch? Is this the standard for all RC stuff?

Thanks in advance!
Jim
 

Indy durtdigger

Well-known member
#2
I've been using the 3mm luan with no issues and it cuts easily with a utility knife. Only drill or make the holes you need, no need to copy the store bought ones. They still break sometimes during crashes but all the wood ones do. The 4mm stuff will be heavier (and considerably stronger) but probably not much heavier than the aluminum ones some of the folks on the forums have posted pics of. Just looked and all of the wood screws that came with my motors appear to be M3 or something similarly sized. Also I quit drilling the screw holes and just use an awl to make a deep center punch to start the screw in.
 

Aireal Anarchist

Well-known member
#3
I have used luan and am in a current build, actually with trainer type models Im not picky at all, I have glued old credit cards together to make firewalls, I very often hot glue my motor mount to the model so what screws Im using to fasten my motor to the motor mount are not such a concern to me.
If im building a more advanced plane for FPV or an acrobatic speedster that Im deliberately over powering, or a glider that I am concerned with weight issues, I now pay more attention to details and tend to go the extra mile

my advice with your tiny trainer is follow the video build M3 will be fine and have fun
 
#4
Thanks. I looked more carefully at the motor and realized it isn't threaded at all and has plenty of clearance for whatever screws and nuts I choose to make. Now we are trying to figure out if it's prudent to extend the motor pod so that it can hold the receiver and speed controller too and be truly "swappable". I got a gyro-stabilized receiver which needs a solid mounting position. The airframe is ready to go- tomorrow we mount up the electronics.
 

Hai-Lee

Old and Bold RC PILOT
#5
Thanks. I looked more carefully at the motor and realized it isn't threaded at all and has plenty of clearance for whatever screws and nuts I choose to make. Now we are trying to figure out if it's prudent to extend the motor pod so that it can hold the receiver and speed controller too and be truly "swappable". I got a gyro-stabilized receiver which needs a solid mounting position. The airframe is ready to go- tomorrow we mount up the electronics.
You could mount the stabilizer almost anywhere I suppose though my own preference is to mount it at the centre of gravity for best performance. Mounting the stabilizer in the powerpod is actually asking for problems as the powerpod is only held in place by skewers and after time the holes for the skewers can enlarge and there can be minor changes in its alignment or position even in flight.
Whilst this may sound bad it is manageable at small amounts but the Stabilized might over react and the plane become difficult to control.

Just my thoughts!

Have fun!
 
#6
Tiny trainer is almost done- need to install pushrods and need to get velcro for battery and receiver mounting. I watched videos for a couple hours today and decided that downloading firmware and setting up the gyro-stabilized FRSKY S6R receiver isn't my priority. I just want to fly!

I think we're overpowered. I had to build a larger mini PowerPod to handle my motor and with the heavy motor the 3s 850 battery needs to go right at the CG. I'm going to ask my son if he can program the controller to either limit the max power or at least reduce throttle sensitivity.

With the battery needing to go near CG and the receiver needing a specific orientation, ideally at CG, I mounted the servos externally similar to how they get mounted on wings for ailerons. They're visible if you look at the attached photo.

Airframe without servos was approx 150 grams. Fully assembled (minus pushrods) with battery it's 350. It looks better today than it will after flying! The good news is I know how to rebuild it. IMG_3648.jpg
 
#8
Thanks.

I'm a little concerned about the overall weight with my over-spec motor and battery. Design spec ready to fly weight is 270 grams which results in 22g/dm2 (7.1 oz/ft2); Mine is 350 which will be 28g/dm2 (9.2 oz/ft2). I notice many of the other single engine/high wing planes have quite a bit higher wing loading.

Note that it was constructed with Ross Foam Board from Walmart. It is noticeably thicker than Adams from Dollar Tree. My box of brown Flite Test foam board was delayed in shipment and should arrive today.
 

Innaviation

Well-known member
#9
Hmm, I don't think the weight of the motor will make the plane not fly by any means... Since your motor has more power it will just end up being slightly faster than a typical tiny trainer. However, It will have some CG issues since all of the weight is up with the larger motor. You may just have to mount the battery outside of the plane fuselage.
 
#10
It seemed the weight balance was perfect until adding 5 grams of pushrods made it slightly tail heavy. shifted the battery to butt against the power pod and it's good. I almost need a shoehorn to get the battery and speed controller plugged together and positioned.

Everything is assembled and the receiver is paired. Son is going to try and get the stabilization set up and hopefully we can fly this evening.
 

The Hangar

Well-known member
#11
It seemed the weight balance was perfect until adding 5 grams of pushrods made it slightly tail heavy. shifted the battery to butt against the power pod and it's good. I almost need a shoehorn to get the battery and speed controller plugged together and positioned.

Everything is assembled and the receiver is paired. Son is going to try and get the stabilization set up and hopefully we can fly this evening.
Good luck on the maiden!
 

Merv

Well-known member
#12
I share a build table with 3 noobs @ FF19, all built TT, all balance the planes at the recommended CG, all were tail heavy. When we moved the CG forward 1/2 inch all flew great.
 

JasonK

Well-known member
#13
I share a build table with 3 noobs @ FF19, all built TT, all balance the planes at the recommended CG, all were tail heavy. When we moved the CG forward 1/2 inch all flew great.
I will second this, Got this same comment from Merv when building mine and moving it 1/2" forward did wonders for the flight characteristics.
 
#14
Thanks for the comments about CG. I'll bring tape and quarters to adjust balance old-school style.

We gave up on setting up the FRSKY S6R receiver for stabilization. We will just use it as a normal receiver. Planning to fly in the morning at a nearby park before it gets crowded and/or windy.
 
#16
Follow-up:

It flies but I'm not a pilot yet. Broke 6 props either crashing hard or forgetting to cut power or both. The plane itself is fine other than a somewhat mushed nose. After running out of props we played with it as a glider throwing from the bleachers and it was very balanced and controllable. I'm going to practice this more.

A few problems and next steps.
We don't have any big spaces nearby. The largest is a soccer field. A few parks have somewhat large areas but there are fences or trees to worry about. We are going to scout a bit more over the weekend.

I'd like to get a flight simulator program to use with the FRSKY transmitter, but we just have Chromebooks, iPhones, and XBox. I haven't found a simulator program that works with these.

Meanwhile my son is swapping the Tiny Trainer motor and electronics into a Simple Sparrow- hoping that being a pusher it will be more forgiving of crashes. I'm going to build a simple Cub this weekend and we'll get appropriate sized motors and electronics to have nice lightweight planes and smaller, tougher props.
 
#17
Follow-up:
Meanwhile my son is swapping the Tiny Trainer motor and electronics into a Simple Sparrow- hoping that being a pusher it will be more forgiving of crashes. I'm going to build a simple Cub this weekend and we'll get appropriate sized motors and electronics to have nice lightweight planes and smaller, tougher props.
My son built the simple sparrow first before the tiny trainer. It was near impossible to fly well and much more difficult than the tiny trainer. It has wicked torque problems. Stick with the tiny trainer for learning to fly.
 

The Hangar

Well-known member
#19
Follow-up:

It flies but I'm not a pilot yet. Broke 6 props either crashing hard or forgetting to cut power or both. The plane itself is fine other than a somewhat mushed nose. After running out of props we played with it as a glider throwing from the bleachers and it was very balanced and controllable. I'm going to practice this more.

A few problems and next steps.
We don't have any big spaces nearby. The largest is a soccer field. A few parks have somewhat large areas but there are fences or trees to worry about. We are going to scout a bit more over the weekend.

I'd like to get a flight simulator program to use with the FRSKY transmitter, but we just have Chromebooks, iPhones, and XBox. I haven't found a simulator program that works with these.

Meanwhile my son is swapping the Tiny Trainer motor and electronics into a Simple Sparrow- hoping that being a pusher it will be more forgiving of crashes. I'm going to build a simple Cub this weekend and we'll get appropriate sized motors and electronics to have nice lightweight planes and smaller, tougher props.
The sparrow isn’t very easy to fly. I flew mine once and then retires it since it wasn’t super fun to fly. Part of that was since mine was way overweight though. I’d recommend building the mini FT-22.
 

Hoomi

Well-known member
#20
First and foremost, everyone crashes. As we get more experience, we crash less often, but even the best pilots crash from time to time (Need proof? Visit the "What did you crash today?" topic, or hop over to the Hobbysquawk forums and check out the "Crash Contest" they're running. Some of them crashes had to not only feel painful to the confidence of the pilots, but also to the wallets.)

The Tiny Trainer is a reasonably decent plane to fly, and probably as good as any for learning. One thing I would suggest trying, is getting it to altitude, and then practice cutting your throttle, letting it glide for a few moments. Getting comfortable with how she flies with no power, will help on your landing approaches. With a belly landing plane, you want to be able to cut the throttle enough above the ground, that the prop has no chance of striking the ground while under power. Since the TT glides reasonably well, it's pretty forgiving with cutting the power earlier. Line up where you want to land, and decrease your throttle to reduce both your airspeed and altitude. Allowing the plane to settle this way, rather than using elevators to "aim" it towards the ground, lets you keep the plane more level, so that it's far more likely to touch down on the belly rather than the nose.