Mighty Mini Spitfire - Beta

[SheppO]

Mighty Mini Spitfire - IKEA box build

I took the mini speedster and spitfire plans and kind of amalgamated them to make a simple mighty mini style spitfire. These are calibrated for 3mm board as I wanted to try out some leftover IKEA corrugated cardboard as a build material (feels pretty light) . Tail surfaces over sized and quite a lot of dihedral. 185g AUW (6.5oz). used a 2204 multistar elite motor, 460 2s under the power pod. Balancing on the wing crease right now which is a bit aft of the speedster's CG marks. The guts are all stuffed up the underside like the scout / speedster.

 

[rockyboy]

Interesting - looking forward to seeing how she flys!

 

[T-Richard]

Looks interesting

 

[SheppO]

Here she is, 70grams at the moment minus power pod - probably a bit on the heavy side, but I do like the look of the cardboard, a touch of green spray and ill have instant camo - any recommendations for motors appreciated - maybe that HK Hextronix 10g ? The wing surface is around the same as the mini speedster - so i need to keep as close to 115g all up weight without battery to hit a similar WCL, which might not be possible. I'd like to know how much one would weigh in DTFB - so if anyone across the pond fancies joining in on this, please do !

 

[ika]

Did it fly?

 

[davereap]

Its a nice one for going with a depron or EPP build... now my plans are printed and joined..
I re-drew your plans in sketchup, then moved all the parts closer together..
the re-draw is slightly different in that there are no folds shown, my construction has no fold overs, it will be just butt joints. glued with UHU por..I also lengthened the ailerons you made , In case I want to use a single center mounted servo to work them..
The plans now take 8x A4 sheets to print out.. the construction will need some fiddling to get a similar result to the folded build

also thinking to make a top access hatch, and add a central internal horizontal spline just above the wings

the pdf here needs some adjusting on shapes.. the depron build requires some different methods compared to the foam board

 

[davereap]

which is what I did.. I have put a central horizontal spline just above the wing to provide fuz strength, so I can make a top hatch...

I am using 3mm depron covered with ironed on laminating film to emulate the paper board

its getting there.. I made a few mistakes along the way, the worst being to glue the wing in out of square with hot glue... this is now straight, but I have warped the wing slightly.. it will need some ironing out...
you wont get this problem with the paper covered board, its just my covering that allowed warps in when I heated it up to correct the wing position..

some more mistakes here.. servo holes were made, but the arms will be too close, so I will be filling them in.. then gluing the two servos flat onto the spline at the rear here... the arms will stand vertical with a better space between them..



hatches closed...


here the ESC is sitting on the spline, the leads go through and up to the top of the spline for the RX and battery. And a simple wire UC is sandwiched in an EPP block
I am thinking of cutting an extra servo into the wing just behind the UC block to work the ailerons

 

[SheppO]

I haven't had much time to work on mine - so stoked to see Dave picking this up. Looks great buddy ! Ailerons - kind of required for a warbird I now realise ! And landing gear also a nice addition.

Depron is most definitely going to work better than cardboard ! I have just ordered some electronics and once delivered made various discoveries that I guess are common for newbies, like.. hmm so that esc doesn't have a BEC on it, and er so the motor doesn't come with mounting bolts, and.. those props dont fit this motor, and that esc needs a JST power connector, and bullets for the motor soldering on. And
my soldering iron is knackered. oh well. One day when I can carve out a bit of hobby time I should be able to get it flying. But Dave - you will likely beat me to it and considering all I have built is a 2 channel glider - i am likely to crash mine instantly anyway - so you will be able to test the design far better than I - I expect.

 

[davereap]

I think you did well on your build, although cardboard is not used much.. it showed the idea is practical and looks good..
esc's ...most have a bec circuit. its normally only the bigger stuff that has an option to go without a bec, as big planes have their special power requirements ..
Motors .. normally come with a prop adapter and a mount.. no bolts.. sometimes they have small bullets soldered on, sometimes you have to do it yourself..
On this size of model, I fit my motor using 1/2" long self tapping screws . these go into a 1/16 ply plate.. I screw on the mount, then remove it again.. the screw holes are given a drop of CA to make them tough.. once set ,the mount is fitted back on and the ply is glued to a nose block made from EPP... EPP works well because its got give, so in an impact it doesn't snap like depron will..
Props and adapters , its rare that the prop will fit easily, but they mostly now come with a series of rings to help... on mine I have to fit a ring, then drill it out a touch to get a good tight fit.. then balance the prop..

loose fits are no good because the prop will always vibrate, being fitted off center its going to be out of balance..


The wing warp was ironed out and the gear all fitted... I havnt added the ailerons yet.. Its going to fly first on the two channels like their other minis... but the rest is done.. using all hobbyking items ... 2211-1700 motor .. 4ch orange mini RX.. turnigy 1440 servos 4.4gms ..and a 500 2s for power..8x4.3gws prop
AUW is 6.1oz... on a 1sqft wing.... so first thoughts are that this will be a bit fast for indoor use, but it will get a go tonight..
with the wing section and being all open under the fuz it may be draggy enough to fly slower..

the motor has a few degrees of down and right thrust..
All Up Weight with the covered depron build ....with no battery 140gms....
the other flite test minis are 115gms....

most of my indoor models tend to be nearer the 200+"sq size and so have lower wing loadings on very similar weights , lower loadings flying slower, are just about correct for a hall....
I could have saved weight by not covering the depron with laminating film, but I am trialing this material at the moment.. I could have also stayed away from the hot melt adhesive, its another weight adder
Its got plenty of power, enough for vertical, so it should fly, but perhaps too fast...

the servos are glued in under the cockpit area, laying on their sides with their arms vertical.. the battery has to go as far forward as possible for the COG which is on the fold...

 

[davereap]

the first flight took place last night and it was only half way ok.... the model took off easily at low power, proving the weight is not an issue, but the wing warp previously noticed was still there... it went up rolled left and full rudder had little effect... it carried on rolling into the ground... hitting hard it proved the strength of the lamination film covering.. with just a small crease on one tip...

so partial success and part fail... I will attempt again to remove the warp...

I think if I had fitted the ailerons I could have compensated for this, because it was just a slow roll....

 

[davereap]

I spent ages trying to get rid of the warp.... it looked ok but was still messing up the flight...and the result a creased wing.. so sorry but I have cut the wings off and started to make some new ones...going EPP-KFm2 with this set...

likely with the paper covered board the warping would not have happened, its me that covered the depron and induced the warp

 

[davereap]

new wing... with ailerons... its visible where the old wing was fitted and Ive had to fill in the fuz sides to take a KF wing..

the new wing is from 5mm EPP covered with laminating film... there is an ironed on melamine edging strip top and bottom of the wing on the step line that acts to make a spar.. the result a wing that is very stiff .. you can pick it up on the tips without any bending..

 

[davereap]

the new aileron wing has taken the weight up to near 7oz .. the model flies ok but is too fast for our indoor venue...

so have a care keep the weight low... all the covering I used added too much weight, its very strong however .... so its a trade off.. weight and strength..
I should have put ailerons on the first wing perhaps what I thought was a warp was more of a torque roll... I only thought of that later on, I was using a big prop on mine... so it is another possibility..

 

[SheppO]

Interesting Dave - my whole thinking for this build was - take the ft speedster - proven design , should fly good and just style it like a spit . For a lazy indoor warbird vibe - So I guess I thought as long as the wing surface area, control surface size - angle of attack on the wing / thrust angles were all the same as the speedster - there would not be that much difference in flying characteristics - I guess weight is just a big issue at this scale - and perhaps those elliptical wings are inherently tricky from an aerodynamic PoV.

Also maybe loosing the polyhedral in favour of dihedral adds another level of instability. I've made a little progress on mine - got the pod built and motor mounted, revised my canopy design. Waiting on a 2.5 g lemon rx now - to save some weight . But as it stands airframe with motor and prop plus control rods is 112g - so I will be heavier that the 118g of the speedster for sure.

Must say I was surprised to see your big prop - but then I still don't really understand motor - prop - esc compatibility - I have got a 5x3 three blade gem fan and a 6x3 regular prop - running on a multi star elite 2204 motor with the 12a emax esc ...?

If only we could get some Adams board over this side of the pond - or someone over there to try these plans...gauntlet deployed USA...;-)

 

[davereap]

nothing wrong with your thinking....

I messed up and well over engineered my build... using a bigger motor and prop than it needed for the area of the wings, I also made mine much too heavy, I should have simply used uncovered 3mm depron.. and a smaller motor /prop setup
result it flies, its strong, but its not slow enough..

To correct this I suggest going a larger span to raise the area by 50% and a much lighter build, with a 10gm motor and 6" prop, 6Aesc.....

 

[dpalmer146]

Red Baron Mini Scout

I love the mini platform. Pulled out my mini scout and flew it around.

https://youtu.be/JzL0aNDc9kY

Saw this build and since I have plenty of these little motors, I think I will give it a try.
Since the Red Baron is getting long in the tooth and is mostly hot glue and tape these
days. It would help if I didn't fly it into stuff.

https://youtu.be/KdZVDEC3zrA

 

[xMeox]

If only we could get some Adams board over this side of the pond - or someone over there to try these plans...gauntlet deployed USA...;-)

you can get foamboard shipped from the US: adams foam boar. Just check that you get foam board and not poster board as I did

I have som own ideas that I have to try out first, but afterwards Id really like to build a mini spitfire

 

[m00ndancer]

I tried to build a 50% FT spitfire, and maiden it last evening. Didn't go well.. The throws are too large and I'm just a rookie pilot.
It's to heavy in the tail, so that have to be adjusted, and perhaps a bigger motor. (there is a hextronic 10gr that might fit the bill, solve CG and lack of thrust.) AUW about 89gr with 300mAh
But I'll be testing it on Saturday if the weather is ok, not a good idea to maiden stuff indoor in a smallish venue.

 

[SheppO]

Inspiration:

http://feltondesignanddata.com/id18.html

http://feltondesignanddata.com/id26.html

 

[DazDaMan]

Any more progress on the Mighty Mini Spitfires?