Need advice about RC options for ultralight paper airframe project

[liftline]

I will have to look into Depron. I'm still capable of learning new tricks, it just takes longer with fewer neuronswall1

I forgot to mention my most important design tool - MS Excel. All the cross section data are put into Excel spreadsheets and macros compute the 2-D patterns. These are usually smooth these a bit with some statistical software.

A few more pics (I haven't looked at some fer years now). The f-15 was commissioned as a retirement "card" for an engineer who worked on the Program for the USAF. The simplest design I done in years, glides well if slingshot launched. Needs tiny ducted fans!

 

[schorhr]

Somehow the images did not show up earlier... Real nice work! Don't worry about units, I can roughly convert them or look them up

 

[liftline]

I could probably adapt to Depron - especially for the larger patterns. If it is a bit compressible it might actually improve the joints between component pieces. My typical model is built up from anywhere from 4-7 joined patterns in the fuselage. At 3mm thickness Dep would work great for bulkheads - that's probably where I'll try it first. Also seems a natural for wing ribs in the traditional model AC style, except that I avoid using ribs in my airfoils - too labor intensive to assemble. My wings are very quick and easy builds - basically just tension structures. A five minute build. Adding articulated control surfaces complicates construction a bit, but not that much. Ten-15 min build? My fuselages are basically semi- monocouque (sp?) tension structures too - the bigger the model the more "semi" things get, since I use the same thin paper for all my skins. A general rule for my construction style is never glue anything unless you must-cut/fold/bend as much as possible.



As you can see, I'm basically an airframe guy, and a distinctly amateur one at that! This has been a fascinating discussion! I'm getting a "world view" that's hard to find in my part of the USA.

 

[schorhr]

You should defenatly give it a try, I'm glad I built my first rc plane with it... It's nice to work with (if the knife' blade is sharp...) and versatile.
Keep me posted how it works out with depron, rc and flying

Depron can be worked with styrofoam glue and even wood glue, but hot melt glue attaches it almost instantly while it is only slightly heavier if used carefully.
It bends, can be formed with heat. Gaps can be sanded or filled with spot filler (I hope thats the right word for it in english).
If your paper models look that great allready, I can't wait to see one airborn


Still a bit puzzled that there's no shop selling those coponents in your area. But as they ship so cheap (might take 1-4 weeks though) that's not a big problem.

 

[liftline]

You are too kind! Every one of the models glides well, with the glide ratios reflecting what you would expect from the era. None of these models take more than one evening to build - faster if you cure the white glue in a microwave oven instead of just letting things air dry! Production cost is tiny-ink is the biggest factor-yellow ink ooohhhhh. Almost cheaper to buy a new printer than to get new ink. Refilled my own until recently, but my Cannon Bubble Jet head clogged and the printer manufactures have taken evasive action on the new models.:cry: I will eventually move on to color laser, the startup is just a bit too rich for my budget.

Had to find a picture of my 1905 Wright Flyer (the first really practical airplane in my humble opinion, and it still lives in my home town of Dayton, Ohio (take that Dearborn Mich, take that Smithsonian) Semi-scale in order to make it stable in pitch and roll. The Wright Bros cared not for stability!

 

[schorhr]

Haha, I bet depron in the microwave would be fun.

Aww... Well, sounds like you need a printer with cheaper ink cartridges ;-) I used to use refil or refurbished cartridges, with ink from a decent supplier there has been no trouble. With clogged up jets, stopping printing and clean the printhead with destilled water or isopropyl alcohol has proofed to be a good cure


Looks neat ;-) For ultra light planes some even cut the depron in half, to get 1.5mm or even thinner... insane

 

[liftline]

I've Googled the density of 3 mm thick Depron and it seems to be about 130 g per m^2. I realize there are different grades, but is that about what the micro RC community is using? The paper I work with (quite ordinary office supply stuff) weighs in at 75 g per m^2, so I have some reason to believe my airframe weights are actually pretty competitive, even with my internal bracing (same density paper for the bracing).

Not knocking Depron though. It gives you a curved edge to glue on to. That's a significant limitation to building with thin paper. As mentioned, bulkheads seem a great application. Depron inserts might keep struts from failing in compression. Especially WWI undercarriages. Hmmm. That would be a big help. Then there is the problem of rain...the Kryptonite of complex paper models (dogs and babies are plane wreckers too). Heat forming would be helpful with some parts, but I tend to shy away from molds. If yer gonna cast, cast.

Definitely going to find a few sheets to play with!

 

[schorhr]

Well, 1.5mm Depron would be the same then. There are also selitron and other softer types; 3mm is for bigger things indeed.
The main advantage of depron is, that it is much stiffer (no need for wood or carbon rods on small models), won't get dammaged when flying outdoors (rain, puddles...), and is robust and can be fixed easily.

As with many things, each material has it's advantages. Some even combine materials, and use thin paper or foil for the wings to make the model lighter.

As for heating: Some just bend it with hot water or air, some cut layers and sand it down to form. Many ways to go... I guess it's a matter of taste and experimenting

 

[liftline]

Think I've found a suitable transmitter I can borrow - but it's packed away in a storage bay that my brother has to sort through - not sure of the freq and neither is he, but it's a 1year old model with 6 channels.

Anyhow, just speculating about gear retract for AC in the 40-60 g range. For my paper WWII fleet I can upscale. Even the smallest kit retracts on the market seem made for aircraft about 10X heavier! Something simple would be great, just a one time spring powered system that drops the wheels when you signal the trigger. Surely this was done by in the stone age? Can always launch the planes gear-up by hand, but I'd prefer to avoid belly landings at the higher weights demanded by powered RC. Gear doesn't have to look great in the down mode, just work reliably. Might have to self engineer with my own three hands? Hate to fly them with fixed gear - it just looks wrong, wrong, wrong. Maybe an inconspicuous skid will have to do. Or maybe trail an arrestor hook on a rubber band and try and snag a cable. You can see why I'm hoping for suitable retracts!

Flight test is getting iffy here in the mid west USA - winds picking up. Did verify the Se5a can slope soar at 25 g. You need an ideal hill (got one nearby) and the wind blowing moderately in just the right direction and a lucky toss - but its poetry when it happens. The prototype white bird is looking pretty dog eared these days, the undercarriage is a bit crooked, but she has a few more flights left in her.

 

[schorhr]

For the small stuff, magnet coils, muscle wire or 1.5g servos should be the way to go?
You might want to check out rcgroups as I never built any micro landing gear.
Unless you are on a perfectly smooth area (gym or such), wheels on small models are useless anyway and you tip over ;-)

 

[liftline]

Maybe belly landing isn't such a bad idea after all. :v8: The pre-assembled Park Flyer fighters at my local hobby store all get by with it - and a lot of those weigh 2 pounds or so. Maybe some 3mm depron in my lower fuselages to increase stiffness and durability a bit.

 

[schorhr]

yep, most do belly landings... unfortunaly pavement, grass, rocks and such are not scale...
A lot of people put Tape on the models to avoid damaging the body.

 

[liftline]

Scouting around at my local hobby shop I saw an intriguing little integrated receiver/speed controller/2 servo unit in my local hobby shop yesterday. Priced $59 US, very compact. I hope this is a trend.

My brother can't find his transmitter, he's remodeling his house and most everything he doesn't absolutely need is in a storage bay packed as tight as King Tut's Tomb. :cry: Probably a good thing, with prices so low I might as well modernize and optimize. Moptimize!

I'm very confident in the airframe's aerodynamics and structural integrity. I leave more wheels and axles on the ground than I would like, but that should improve with control if the weight doesn't get too high.

My next step is to engineer control linkages. There is plenty of space inside the wing for push rods but I'll probably get my feet wet by starting on just the rudder. I'm leaning strongly towards implementing your austere throttle & rudder control option. This ship is really docile and executes beautifully banked turns on rudder only. I should really wait until spring for flight testing, but will probably risk testing in a gym, or maybe local enclosed stadium. Absence of wind is nice, but hitting a wall, pillar or seats will fold this thing up like an accordion.

 

[schorhr]

Yeah, those things get cheaper and cheaper.

Well, the $32 transmitter is certainly a bargain, even if it's receiver is not micro, 7g stripped without mods/soldering is not too bad.


rudder control:
You can use a string pulling system instead of push rods, a bit lighter depending on the construction
6th pic http://www.glos-mfc.co.uk/models/panic/panic.htm
(could not find a micro picture that quickly)

Well, with just motor control you can not do any funky loop-de-loops (at least not as agile), but i guess that is not the aim

Build some "sketch plane" before ruining a neat model But at that weight, nothing ever really brakes.

 

[liftline]

F4f prewar paint

This is the belly I'm worrying about. Executed in 1:48, could probably house micro RC. Glides well, aerobatic.

 

[liftline]

Yep, I call 'em blueprint versions. Like the one early Pic of the Se5a with my finger pushing at the aileron. Basically just saves ink unless I leave off all the funky detail parts

 

[schorhr]

Nice
Micro & low wing? Might want to give the wings a bit of a "V" shape to avoid it getting twitchy in flight

 

[liftline]

The wing is pretty ambitious on this little model. It has a fair amount of dihedral, but that' not easy to discern in the photo. Zealot forum seems to scale my jpegs, so what you see is bit smaller than what I sent (or thought I sent. The cool thing is the wing is a good approximation of the classic Clark Y airfoil. A totally flat bottomed wing just didn't quire look right, so I amped it up a notch. Not that a Clark Y is a true scale airfoil section, but it's truer than what I would normally attempt. This model is about a year old now, I've since learned to do a Clark Y easier and lighter. No ailerons yet, and the elevators and rudder are a simple style fine for trimming a glider, but not good enough for RC.

I have a Mitsubishi Zero pretty far along in development, but it lacks wings and a paint job. Canopy is spectacular if I do say so myself aussie. Good candidate for RC too! Build a skid into the belly tank!

 

[liftline]

F4F Guadacanal

Here it is painted circa 1943. That's one of the great things about paper. So easy to change the color scheme.

 

[schorhr]

Yep, paper is really something Looking good!