DTFB Single Sheet Trainer

[tadiasa]

Perhaps I'm overstepping by abilities here as I have very little flight experience and very limited knowledge of aeronautical engineering, but I am trying my hand at a trainer design that is made of a single sheet of DTFB. Here are the parameters I am trying to follow:

Must use no more than a single sheet of Dollar Tree foam board
Must be easy to assemble
AUW < 250g
Must be stable in flight
Must be aesthetically pleasing

I know this last requirement is completely subjective, but if I don't like the way it looks, how can I be proud of it?

In my first prototype I opted to use a V tail configuration with a flat wing (no dihedral) that slides through the fuse at the top. This was just a rough cutout and slap together with no electronics and I made some mistakes in the layout that resulted in me having to insert doublers in the nose so a standard FT mini power pod would fit snugly. These errors will be fixed in my second prototype as well as adding a dihedral to the wing and perhaps using standard stabs instead of v tail. Glide tested only (no electronics installed) with motor and battery friction fitted for nose weight revealed that we are already nose heavy with a 1806 2400kv motor, 12A Emax ESC, and a 1000mAh 2s battery. More work on this build tomorrow, but input, and constructive criticism are always welcome.

 

[tadiasa]

Got the main construction completed on the second prototype. Dropped in a couple servos and ran some push rod. Tomorrow I mount the control horns and power pod and we'll see if it flies. I have to remind myself, pictures before maiden.

 

[Crazy Goats]

Cool! Id like to see how this goes.

 

[AndyP57]

Hi, You will probably find out on flight trials but personally, as a trainer, I would have added some dihedral for stability. It's also difficult to see due to the angle of the photo but it seems you may need a little more tail area. As a rule of thumb for V tails, if you look directly down at the setup, you should see about the same area as if it were a conventional tail. The same goes for equivalent fin area. Good luck though and these are tips and tricks that you will learn through time and experimentation.

 

[tadiasa]

Prototype 2

I opted for the standard stabs, though there was plenty of material for v tail. Last time I cut the fuse too long which resulted in less material for tail feathers. Control surfaces are 4cm long and this is a 3 channel. CG has me a little worried, I may have to make the nose a little longer. Balances almost perfectly under the center of the spar which is about 1.5mm aft of the 1/3 mark from leading edge of the wing. Tolerances are a little tighter than I would have liked, but I'm off for a maiden.

 

[tadiasa]

We'll, after flight trials I found that I had nothing to worry about with CG. Nose heavy from the get go, moved it back a bit and had some relative success. Wind was a bit strong today which kind of put a damper on things, but even after moving CG back a little up elevator was in order to trim it out. It kept dipping the right wing and was very anemic on left rudder input. After inspection I've come to the conclusion that 20ga galvanized steel wire is not strong enough for push rods. Also the rudder control horn came loose which sent me back to the bench. I think that this is certainly a viable build and once I make the necessary modifications it will be a gentle little trainer.

Specs:
Wingspan 29.75"
Length 21.5"
Chord 5.875"
Motor 1806 2400kv generic ailexpress
Battery Floureon 1000mAh 2s 20c
ESC 12A Emax BLHeli
Receiver Flysky FS-IA6 (FS-I6 TX)
Servos Tower Pro 9g x2

She'll snap like nobody's business and if I can get the push rod issue taken care of we should be able to snap roll with ease. This entire build has been pretty much by the seat of my pants and I haven't put together any plans yet, but they are in the works. The entire build used a single sheet of dollar tree foam board including 2 power pods (I know myself, I will need that second one) and enough material for a throw gauge and a dihedral gauge, even though I kind of cheated and used the one from the mini mustang build. So far I have used a single stick of hot glue and I'm still using the same gift card from my original TT build for control horns and the same sheet of 1/16 ply for the firewall. Cost breakdown looks like this:

DTFB $1.09
Servos $4.38 ($2.19 each)
Receiver $13.50
ESC $6.67
Motor $8.64
Battery $7.50
Total $41.78

Bear in mind that most of these components are electronics and can be reused and I'm not including the cost of my TX.

 

[rcspaceflight]

It's amazing what a person can do with one sheet of Foam Board. I love how everyone comes up with something different when restricting themselves to only a single sheet.

Here is what I came up with 2 years ago: http://flitetest.com/articles/one-sheet-swappable-trainer

 

[jipp]

what size rod are you using for the push rod? i think most use typical piano wire at .047?

yeah its amazing what you can do with foam board.. I sometimes wonder what the powers at be who develop the foambaord from addams think of what has happen from what i assume had a purpose of signs and other crafts in a office or school setting.
i doubt they ever thought hey i bet we could make this fly!

chris,

 

[tadiasa]

what size rod are you using for the push rod? i think most use typical piano wire at .047?

yeah its amazing what you can do with foam board.. I sometimes wonder what the powers at be who develop the foambaord from addams think of what has happen from what i assume had a purpose of signs and other crafts in a office or school setting.
i doubt they ever thought hey i bet we could make this fly!

chris,

I'm using 20ga galvanized steel wire (hanging wire for drop ceilings) because it's cheap and abundant. This will definitely have to be revised as it is too flexible... I suppose I could put my metallurgy skills to use and harden it, but fair warning to anybody who tries this: ONLY DO THIS OUTDOORS IR IN A VERY EELL VENTILATED AREA! The nickle used to galvanize wire makes toxic fumes which if inhaled can cause neurological damage and lead to death within 24 hours. Better to just use a different material instead of put your health and life at risk for the sake of a hobby.

Rcspaceflight wrote
"Here is what I came up with 2 years ago: http://flitetest.com/articles/one-sh...ppable-trainer"

Cool build, and I like the polyhedral on the wings, I may have to incorporate that into the next build. I also like the idea of external servos, but I'm afraid that will be an exposed point of failure which will cut down on the durability and as this is a trainer, I want it to be as strong as possible

 

[kerrycorcoran]

Interesting and cool!

 

[Jugsy]

This is awesome, living in Australia I love the material efficiency!!

 

[rcspaceflight]

Cool build, and I like the polyhedral on the wings, I may have to incorporate that into the next build. I also like the idea of external servos, but I'm afraid that will be an exposed point of failure which will cut down on the durability and as this is a trainer, I want it to be as strong as possible

I was always too lazy to properly hide all of my electronics. I actually went through a lot of redesigns with the wings because I kept folding them mid-flight or didn't get the polyhedral right.

 

[tadiasa]

I actually rebuilt today and added a hatch for servo access and increased the dihedral. Also using some 19ga hanging wire instead of 20ga and moved the servos back to shorten the push rods. Hopefully that should take care of the issue with the push rod bending when trying to turn left. Pictures will be posted in a bit (have to finish assembly, I had to pack it up and pick up the kids and make dinner). I hope to maiden tomorrow

 

[tadiasa]

Prototype 3

Here is my latest prototype


Here is how it lays out on the foam board. Note the rectangles at the ends of the wing for under camber, these pieces can be used for power pods and there is plenty of room around the tail section to generate a dihedral gauge and throw gauge


See the increased dihedral? I just used one of the scrap corners from the wing cutout which gave me a 3 inch rise over 14 7/8" wing. If somebody wants to do the math to see just how much dihedral I have, they are welcome to it.


V stab and H stabs now have equal amounts of surface area. Not sure if this is important, but it makes for a symmetrical look.


Access hatch for servicing servos, I seem to be having a problem with the tower pros as they strip if you look at them funny. I used to know some girls who did that, but it was half a lifetime ago


This is the standard thrust angle for the FT mini power pod. On it I have a cheap Chinese import 1806 2400kv motor with a 1000mAh 2s 20c lipo battery and the Emax 12A ESC with BLHeli

I upped the push rod to 19ga galvanized steel hanging wire and have everything set to zero on trims. No rates or expo programmed in the Tx and waiting for the wind to die down so I can go for a maiden. Headed out of town for the weekend so if i can't get it done today or tomorrow, it'll have to wait for about 10 days because there is nothing but rain in the forecast.

 

[tadiasa]

update

So my last post was over a month ago, which is really the last time I touched this project, or any plane for that matter. Car broke down on the way back from Florida and that has become my primary focus. Maybe I'll have time to fly this weekend

 

[rcspaceflight]

Sometimes life gets in the way of living.