Tadpole - RC Groups
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Jan 24, 2003, 08:49 PM
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Jgardner's Avatar


Using the technique of integral framed split F3 I built an airframe for a Tadpole, I have been messing about trying to come up with an airframe for a sub oz. Tadpole. It needs a pusher configuration, F3 material, and slow, easy flight characteristics. This one shows the most promise.

The airframe comes in at 4g on by food scale. It is only accurate to 2g, so I don't know for sure its weight, but it is radically light for its size, I think.

It has a 14" WS and a 2.5" chord

At 35 sq. in. area a 14g plane would have a 2 oz./sq. ft. wing loading.

The first gear will be a bitchar-g hack. Actually the Motor Works from Wally World is the car. That car is the one Mike Cross had success with at about 14 g, so I will start there.

Integral framed split F3 will need a name, I think.

What do you think of this airframe?

What should we call this building method? (other than sloppy in my hands.)

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Jan 24, 2003, 08:50 PM
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Jan 24, 2003, 08:51 PM
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Jan 24, 2003, 09:44 PM
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RC_AV8R_181's Avatar
wow, that's really impressive work. And light too. I need to get some foam and try this out.
Jan 24, 2003, 09:54 PM
Foam rules
Thatovalguy's Avatar
Yeh that should fly real nice. I was at Lowes today and almost bought some fan fold. Now I wish I did.
Jan 24, 2003, 10:34 PM
Crash Master
Gene Bond's Avatar
Nice work!

You are leaving the skin on and carving out the foam, right?


Split Fan Fold Foam Skeletal Remains

Jan 24, 2003, 11:01 PM
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Jgardner's Avatar


SF3SR it is.

To try it you just need a small bit of F3. You might try to get the folks at Lowes to give you a chunck of a ratted up bundle as a sample, or bum some at the next indoor meet.

The Tadpole took less than one half of one square foot. 400 planes per bundle. Less than a dime each in foam. Can't be much glue either. Glue at 97 cents for a few hundered planes as well.

I hope some others can try this out too.

And I still have to get something to fly with it.
Jan 25, 2003, 03:18 PM
Registered User
Split Skelecor.

Put an led in there and turn off the lights!
Jan 25, 2003, 05:04 PM
Thats NOT indestructible
j8m8l's Avatar
Hey J

You might try using another adhesive, as hotglue (if you are still using it), is a bit heavy for this sub oz work.

Otherwise, this is VERY cool, and much lighter then your other ones with all that excess foam gone


Jan 26, 2003, 08:45 PM
Got helium filled wings?

foam by any other name

skinned foam skeleton = SFS
foam skinned frame = FSF
skinned foam framework = SFF
bluecor frameboard
bluecor frame foam
framed foam process = FFP
foam frame flyers
skiinned + foam = skoam
skinned foam lightening process = SFLP
split foam framework
half naked foam
bare side foamwork

Gardners foam process = GFP
Jan 26, 2003, 10:36 PM
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Jgardner's Avatar

All good

Except the last one. No fun in that.

Split skelecor has a nice ring.
Jan 27, 2003, 10:11 PM
Got helium filled wings?

does it fly yet

split foam skeleton bluecor = sploam skelecor

have you flown "the wild bluecor blunder" yet
tried some from work and it twist or torques easy
would it fold or tip stall in hard turn?
wonder if you coat inside edges of ribs with glue would stiffen
off to see the gluer

oh yeah tried to use remover under patch to keep empty area taught
did not work with thinner, alcohol, or hot water
any suggestions?
Jan 27, 2003, 10:37 PM
Got helium filled wings?

can we sponsor contests?

just got idea to have contest for best design of one ounce AUW aircraft
uses your process to build and entrants own power/control systems
would be willing to put up X dollars worth of purchased product from internet
this way no money really involved, just buying something for winner over internet
just idea
am thinking of limiting it to one sheet design where all components are drawn out in silhouette and when cut out must fold together to form plane

front of sheet is wing that folds back over sides that are fuselage,etc.
am fan of good challenge
Jan 27, 2003, 10:47 PM
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Jgardner's Avatar

It may fly.

I flew it across the living room, but the test was inconclusive. Not enough room.

It is early for a contest, lets just mess about for a bit.

The report that an N20 is not too much for the Rx is encouraging. See the Bit thread by Epilot. The current attempt is with the car motor and a DD GWS 2.5X.08. It likely will not work, but I did not think the FrogBipe with the 50XC would be good either, and it is great.

Here is a pic of the Tadpole all ready to fly. It weighs in at 14g, so there is some hope. Without the geared prop, I can reduce the size of the fuse on the next version.
Last edited by Jgardner; Jan 27, 2003 at 10:50 PM.
Jan 27, 2003, 11:22 PM
Got helium filled wings?

wow what a plane

wish i could post pix
that is so cool looking and the weight is amazing
how far do the controls transmit

do have a question about BOOM running to tail controls
with it going up in front of propeller would it add upthrust from propwash
could the boom be made to go back in a straight line
will have to build my own and see what weight i can come up with

hey the glue is dry on both sides
the left side of wing i glued sides closest to rib and not LE or TE
the R side glued corners--- all four
woah the corners make it hard to tweak, much sturdier with CA
went one quarter inch on either side of corner
this pink stuff is brittle...just broke left side when squishing from front to rear
folded like piece of bread (you want camber, you can't handle the camber)
Jan 28, 2003, 10:41 AM
AMA 697691 / FAA 13675
Here is the "Tadpole's" bigger relative, the "FrogBipe" v4.2 that John also made from F3 blue core foam.

Personally, I think he owns stock in this stuff!

WingSpans - 39” Upper, 23” lower
Weight - 4.8 oz.
Motor - GWS 50XC
Prop - red Sky Zap 4.25X?
Battery - K880

Click here for a larger image.
Latest blog entry: Greg's Web Hangar
Jan 28, 2003, 01:35 PM
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Thrust bust

Well, the DD car motor won't push it. It flies to the floor nicely. There are two paths open. One, put two motors on it. Make it somewhat like a P-38. Two, go geared setup with a bigger prop. I am leaning toward option one.

The basic ariframe at about 5g is robust, however. It has taken a beating without meaningful damage. Leading with the box shaped fuse means no damage to the fuse or motor on nose-in.
Jan 30, 2003, 12:32 AM
Got helium filled wings?

too much drag

am looking at the tail boom and thinking if you cut it off and sliced at angle so when reattached it would be straight
this would reduce parasite drag on propwash
rudder should be only thing in line with prop

my model has passed hand launch test
will send pix this weekend when sister visits with digital camera

what about sanding prop down to increase RPM's?
Jan 30, 2003, 12:08 PM
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Drag is an issue with this design

The original Frog was meant to be a bit draggy in order to fly slow and be a good trainer. In order to keep with the spirit and looks of the Frog, I will keep the upswept boom, along with the drag. It also makes things like stall turns work very well using the propwash.

The solution I will pursue is to change to RFFS and KP-00 geared setup. This will give massively more thrust, allowing a stronger build of the fuse and wing and more wing area. I am sure that will work, but I thought I would start with the lightest, cheapest choice first.

For the bitcharg conversion path I will try a twin. The WalMart cars seem to have two identical electircal circuits for F and R and R and L. If two car motors with 2.5X08 props were used for each circuit, then differential thrust may be a viable approach. But this would not be a Tadpole. It could be a P-38, however.
Jan 30, 2003, 04:27 PM
Foam rules
Thatovalguy's Avatar
Why not try a E-charger setup or a N20 setup? Than it would stick with its roots. We need plans when your done.
Jan 30, 2003, 11:08 PM
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Yes, maybe N20 DD with a small prop. Cheap and simple. The mosfets came today. Now, can I solder that small/neat.

Do folks use solder paste to do the tiny SMD replacements?
Feb 01, 2003, 12:02 AM
Foam rules
Thatovalguy's Avatar
Just did a thrust test on my E-charger motor and gear box with a GWS EP-3020 prop at 3.4v and was getting right at 17 grams of thrust and a amp draw of .108ma. This was the best setup and in the air it should unload even more.

Just food for thought.
Feb 01, 2003, 12:13 AM
Living Room Aviator
drliu's Avatar
Just as an important technical point, drag never helps a plane fly slower. Minimal flying speed is proportional to the square root of the wing loading, and adding drag doesn't change this-- rather, it only prevents you from reaching higher speeds that you may or may not need to get your plane aloft.

An ideal plane has minimal drag and flies slower by throttling down, not by drag-rich design.

Feb 01, 2003, 12:48 AM
The effect is sadly temporary
Hippo's Avatar

Just an observation.

My Frog design is draggy because of the extreme undercambered airfoil of the wings. They provide extreme lift at low speeds, and are structurally stronger due to their shape. I did try to reduce all the drag elsewhere as much as possible.

The upswept tailboom is to counter the fact that I was running a 10" prop. The large prop meant that the center of thrust was soooo far above the wing, that the rudder wasn't even in it. I angled the boom up until I found a fairly optimal angle for the controls, and their airflow.

John, since you're using a much smaller direct drive prop now, you don't need to sweep the tail boom up to such an exaggerated extent, however, I still feel that some angle is useful even if only to keep the tailboom up off the ground in hard landings.

Personally I like the style of what you're doing here, and I can't wait to see how it all comes together. I hope that there turns out to be some way to do this without changing mosfets, since that lone step becomes a killer for most builders out there.

Best of luck. I can't wait to see it in the air.
Feb 01, 2003, 12:46 PM
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Jgardner's Avatar

Thanks Dan and Dr. Liu

Good points.

Dr. Liu,
I doubt I can get the drag down enough to fly with just one 4mm DD for power. Maybe two with differential thrust steering would work. Straightening the boom and making the pod smaller are both worthwile in the next version in order to lower the drag.

There really aught to be a way here. The mosfets have arrived, but replacing one of those tiny SMD components is a bit daunting. I have looked back and forth between the tiny pieces I ordered and the tight spaces they go, but have yet to get up the nerve. The total risk is small, however. $15 for the car and less then $1 for the component doesn’t amount to much risk.

I agree with you Dan, if there is a way without the soldering components, it would make it a more widely available project. Just soldering the connections is tricky enough. Just hot-wire splitting the F3 seems to be too much for many. I am amazed that more people are not using this stuff. It is amazing.

Perhaps it is just the blue color. An acquired taste, I guess.
Last edited by Jgardner; Feb 01, 2003 at 12:50 PM.
Feb 01, 2003, 04:56 PM
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Twin engine concept works

The twin engine using two red-cap Zip Zap motors and GWS 2.5X08 props works. At least in preliminary tests. The test involved a knock-together design which was way heavier and tougher than it needed to be.

The plane was out of balance so a lot of up elevator was needed. It could almost hold altitude, it made one trip around the cul-de-sac before landing.

16g airframe. It should not be hard to make one that would come in at 14g with some care.

Turns are intuitive, just let up on the button on the side you want to turn to. I hooked the motor case to the F and R contacts on the Rx and the center of the motors to the positive terminal.

The electrics all weighed 10g on my plus or minus 2g scales.

Now for a better looking, better built design.
Feb 01, 2003, 05:18 PM
The effect is sadly temporary
Hippo's Avatar

Now we're talking.


What battery was that with? And did you change the mosfets on that plane or not? I hope it's not.

Feb 01, 2003, 05:24 PM
Crash Master
Gene Bond's Avatar
We're pulling for ya John!

Can the Bit drive a bigger motor the way it is? I admit ignorance, although I've sneeked a couple looks at the threads, and have a $1.50 Ebay special sitting here (actually, 2 of them)...

You know the RFFS100 & N-20 will work, so it was always a trump card

I hope you make it!
Feb 01, 2003, 11:42 PM
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More testing needed

A bit lighter fuse and still the same result. A much smaller wing on the lighter fuse and still the same result. There is still a distance to go.

The two motors are running on the stock Rx and a K145. Next step is to heat a bit more pitch into the props or carve new props and go back to the long wing.

Perhaps go to a simple stick fuse so I can adjust balance easily.

This still seems possible.
Feb 01, 2003, 11:46 PM
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Biggest motors

Someone suggested that an N20 would work with the stock Rx, but no details. I wanted to work up to that size, since an error would be fatal to the Rx.

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