Review and build log of the FPV Model Trenerka - RC Groups
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May 19, 2010, 06:19 PM
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hugy's Avatar
Build Log

Review and build log of the FPV Model Trenerka

Hi there guys,

this will be my review of the Model Trenerka. This review will consist of 4 parts,
1 the building of the airframe,
2 installing the electronics,
3 the first flight of the plane (and for me)
4 installing the FPV equipment and flying FPV.

But before we begin I will tell you something about myself. I'm 16 years old and live in the Netherlands, so my English won't be perfect. I have had Rc cars, Rc helicopters and this will be my first Rc Plane. I got interested in this side of Rc because of the FPV flying. I liked the whole community that is flying FPV. And of course the view is just stunning. So my goal would be: Learning to fly all by myself, Learning to build a plane all by myself, learning to fly FPV all by myself. I knew this would be a big challenge so I started with an simulator. I bought Realflight g4 for cheap and started practicing. First with a downloaded easystar and no wind. Then a brushless easystar. After about half an hour I could fly those reasonably well so I started to add some wind. Now it became something different, the plane reacts a whole lot different upwind and downwind, but after some practice everything was fine. Now I have about 50 hours of simulator time and I can fly every plane with a lot of wind. Inverted, knife edge etc no problem. So I moved the camera position to FPV. This was something different, I lost the airfield the first 10 times because it was right below me. But after some more practice I can fly FPV reasonably well. I know this is simulated but I think this will help me big times in real life. So after getting familiar with the simulator. I started collecting money and ordering parts. Plane from, Servo's etc from Hobbyking and a lot of stuff from ebay. So after receiving everything I started the build yesterday the 18th of may. And now I will start the first part of this review. Why did I choose for this particular plane I hear some of you asking.
1. It is cheap.
2. It is made of epp foam so almost indestructible.
3. It has good flight characteristics.
4. It has a high payload.
5. It has long flight times.
6. It is a pusher.
7. It is designed for FPV.
8. It is CHEAP.

Part 1: Building the Airframe

When I received the plane I was amazed at how big the box was, this was partly because of the carbon rods that I ordered with it. But it sure was huge.

The box was about 1.20 meters long and 40 centimeters high and wide. After opening the box I placed al the foam parts on the floor.

The plane is 150 cm wide, 106 cm long and the wings are 23 cm wide.
So this is everything you receive when you order the plane. You get all the epp parts, some wooden parts and that's it. No instructions or anything else. So what I used to make this plane receiver ready is:

3x hxt 900 servo's
3x 1m 3mm x 2mm carbon tube's
5x Servo extension cords twisted
1x 1m 5mm x 3.5 mm carbon tube
1x 2200kv motor spinning a 6x4 prop
1x 30 amp esc with 3amp bec.
3x Steel pushrods with clevises
3x control horns.
Plus some basic modelling tools and stuff
More than enough hot glue

I started with gluing the wings together, the wings come in 4 pieces. Because I wanted to make them separatable I glued the wing halfs together. You use the black piece with the pre-cut, hinged aileron on the outside. I put some hot glue on the piece and put them together nice and straight.

Afterwards I glued the fuselage together. This consists of 2 big pieces, but it is designed with a little room in between the top part. You can put your servo wires etc through here. Keep this in mind when gluing. Then you have to glue the big flat piece on the underside of the fuselage and cut the excess foam off. When I had those done I glued the tail section together. Take your time and do this straight.

Here you can see all the parts glued.

Because the plane is made of epp foam you have to strengthen it, I used carbon rods but some prefer other material because carbon can reflect radio waves. I think this is only marginal so I just did it the easy and strong way. After some thinking about the separating halves I came up with an idea. I put two pieces of 25cm of the 5x 3.5 mm carbon. So I made some slots for those, you do this by holding a straight steel ruler on the cutting line and cutting it with a knife. After the cutting you just carve the foam with a screwdriver and you can insert your carbon rod. Glue it down good, you don't want this separating mid air.

It is explained here
How to Install Carbon Rod in Foamie Wings (2 min 23 sec)

So now you will have something like this.

Here comes the smart part. Now you can put your 50cm 3x2mm carbon rods in the glued in rods and you can join and separate your wing. For the people that want a strong wing you can just glue them together and strengthen it. But it won't be separatable.

Now we have the wings done we are going to work on the removable wing holder. You will have to glue the wooden pieces on your foam. It is best explained by the pictures.

Here you can see that you glue the bottom part to the fuselage ant the longer top part and motor plate to the removable wing holder. You then put 4 screws in them 2 on the top and 2 on the bottom plate, those are not included.

On the other side you glue the big piece with the square hole in the fuselage. Glue this good because this will be holding your wing on. It will look funny if it became loose mid flight.

And on the other side of the wing holder you glue the small half round piece with the small hole.

You have to put something through this hole, this will interlock with the hole on the fuselage. I used a plastic plug that I cut off at the right size.

To secure the wings to each other and to the plane I used some strong Velcro from hobbyking. I put a large piece in between the wings and 2 small pieces under the wings.

The 2 pieces under the wings lock onto the pieces I placed on the fuselage.

Now the wing can't go anywhere, it is almost firm. But if you want to get the wing of you just pull it of the Velcro, fold it and there you go.

The last stage was gluing the tale section to the airplane and Strengthen the control surfaces. Those are also made of epp so they are a bit flimsy.

I put a large piece in the horizontal stabilizer.

And one in each aileron and a 50cm piece in the middle of the wing.

I will ad an final picture of the finished airframe here but it first has to become daytime again.

So now I'm ready for the electronics. My first impression of this plane is good, it is a bit rough designed and cut but it all comes together. You just have to be a bit creative and use your head. This is my first ever plane and I put it together in about 3 hours. So next step will be the electronics this will be online around the weekend. The maiden will also happen in the weekend. But this will all be a surprise.

If you got any tips or questions, ask them and I will answer.

Greetz Hugo
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May 19, 2010, 06:21 PM
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hugy's Avatar
Hi, guys. This is an update to part 1. After some information I got from you and other people on the internet I decided to make the carbon wing spars thicker. I followed ramsus method. They went from 3x4mm and 2x3mm joiner, to 8x6mm and 6mm solid joiner. So this is a massive strength improvement. I also changed the way the wing would separate and I put some dihedral in it. So some changes to the rigidity of the airframe. So lets start.

Update part 1

What you need:

1.6 meters of 8x6mm carbon rod.
1.6 meters of 6mm carbon solid rod.
Bison Construction glue.
3mm triplex.

I first cut one white piece (or the piece that doesn't have pre-cut ailerons) in half. Those will be glued to the 2 black parts (or the parts that have pre cut ailerons). Now you will have to cut the 8x6mm carbon rod in to 6 pieces. 4 pieces of about 20 cm length and 2 pieces of 40 cm. Now you have to make slots into your wings and glue the carbon rod's in place with the construction glue. This glue will bubble up and fill all the gaps.

Now you will have something like this.

Now we are going to glue the black pieces to the short white wing sections. I put 15 degrees of dihedral in this joint using some angled triplex joiners. So this is what you need to put the removable sections together with dihedral.

Here they are glued.

And the dihedral.

The middle white piece will be glued to the plane itself, so the most stressful part is solid. No more rubber bands and your motor and esc won’t need to disconnect all the time. Before you do this you have to guide the servo extension wires through the slot I left open during the building of the fuselage. Because you can't excess this place after you have glued the wing on. Because I put the receiver in the back of the plane to get the best signal I can. I needed to extend all the servo wires through this hole to the receiver. Now you have to put a generous amount of construction glue on the fuselage and put the wing on.

Put the wing on and glue the top piece with construction glue too. You have to compress the glue for 4 hours so I put some logs on it.

Now you only have to cut the 6mm solid rod in half and put it through the carbon tubes in the wings and slide your wings on.

You're airframe is ready now.

Last edited by hugy; May 27, 2010 at 06:07 PM.
May 19, 2010, 06:21 PM
Registered User
hugy's Avatar
Reserved for part 3
May 19, 2010, 06:24 PM
Registered User
hugy's Avatar
Reserved for part 4
May 19, 2010, 06:32 PM
Praying for better weather
Coyote64's Avatar
Certainly looks thee part Hugo, i look forward to the upcomming updates and watch with great interest
May 19, 2010, 07:00 PM
I think my wheels fell off.
Thumb_number's Avatar
Originally Posted by Coyote64
Certainly looks thee part Hugo, i look forward to the upcomming updates and watch with great interest
+1 Hugy. Thats for making the effort to document. Still waiting for my 'big box' to arrive.
May 20, 2010, 12:53 AM
my karma ranover my dogma
galaxiex's Avatar
Mine has shipped....waiting....

Nice to see your progress.
May 20, 2010, 04:05 AM
Flying with the eagles
etman's Avatar
Thanks for the build log Hugo.
How did you ensure the wing tip panel angle is correct?
May 20, 2010, 04:10 AM
On a holiday?
boopidoo's Avatar
Very nice!

I would recommend using rare earth magnets instead of velcro though since the glue holding the velcro to the foam is often less strong then the velcro itself. Especially when it's cold the glued velcro comes off way to easily.

It probably works of to hold the wings to the fuselage since this is under pressure but the velcro that holds the wings together may come off. Just a tip.

BTW, did you build the wings with or without dihedral?
May 20, 2010, 04:32 AM
Registered User
hugy good review!
Yesterday I robbed the store to find fiberglass or composite
and I even found a wick length 40cm
I think I will break the wings (2x6 mm) + 1x8 mm (wing joiner) to join the two wings (I also want this to be removable)
May 20, 2010, 04:07 PM
Houba ! Houba !!
rcmonster99's Avatar
Impressive review and methodical.
For a 16 year old you have a mature and logical approach to the project

OK here are a couple of point that make me feel uneasy:
-I would not use hot glue to put together this plane. I fear that cold weather or age is going to make the glue brittle and that the whole thing will fall apart. I am hoping to be wrong but so far Hot glue has been a disappointment.
There is an excellent glue for this UHU POR . It is so good that I use it for hinging the ailerons and elevators

- the choice of motor does not ring right here : I would expect a plane like that to have al least a 9x6 propeller. for that I would expect a 1000KV motor at least 300Watts
I fear a little prop 6x4 like that will be blanked by the motor pylon and you will not have enough thrust to get going....

I invite comments from other people . I would be unhappy to see you disappointed on your first flight
May 20, 2010, 04:11 PM
Suspended Account
EPP is best glued with CA, and an abundance of kicker if you want to speed the build along.


May 20, 2010, 04:12 PM
Registered User
I agree about motor/prop comment of monster, but the space on this plane wouldn't fit a 9" prop, imo.
I think more to a 1500kv with a 7-8*5-6 prop instead, depending on available space.
Maybe a 3 blade prop worth trying too.
May 20, 2010, 04:16 PM
Registered User
hugy's Avatar
Thank you for the comments.

I built the wing flat so no dihedral. I think it is not designed as a dihedral wing because the sides of the wing pieces are completely flat.

I used glue on the velcro to secure it, I tried the rare earth magnets but couldn't get them to stick very well.

Thanks for the compliment monster. I tried some foam safe ca glue but it didn't work at all. So I have used hot glue which was recommended by different people that use epp foam. I will have a look at the motor and prop combo. I can always change it to something else but I was first going for an easy star so I ordered the motor and esc combo for a great price. Afterwards I found this plane and wanted this one. I think it will buff out. But we will see. It sure is going to fly I think.

I hope that I answered all your questions. One more thing. The wing is getting some major strengthening I got some comments from sander/ssassen. And he said that the wing joint is not nearly strong enough but more info later on.

greetz Hugo
May 20, 2010, 04:18 PM
Suspended Account

If you are relying on just the Velcro to keep the wings attached to the fuselage you'll be in for a surprise. You need a more secure mechanism of attaching the wing. Elastic bands is one method often used, or be creative with nuts and bolts and some triplex.



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