Tadpole - Page 2 - RC Groups
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Feb 02, 2003, 09:20 PM
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Jgardner's Avatar

It climbs!

Here is the first version that I made that climbs. I don't know if the Rx will handle a long flight, and I may want less prop, but it gains about two feet in the 15 feet across the livingroom.

It is a 16" WS
2.5" chord
20g AUW
N20 motor
U80 prop
K145 Batt
Hand wound 28 ohlm coil and 2 wondermagnets 1/8" by 1/16"
Actuator done BIRD style
Tx and Rx are unmodified and from WM bit cars (Motor Works).

The motor and prop draw about .85 amp. I think I will try the 2.5X08 first when I find a big space or a still day.
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Feb 02, 2003, 09:24 PM
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Jgardner's Avatar

From the back

The airframe is overbuilt. It will withstand any beating flying is likely to inflict, in my estimation.

The Frog heritage is still evident, so I like the looks as well.
Feb 02, 2003, 09:46 PM
The effect is sadly temporary
Hippo's Avatar

I'm excited now!


This is getting good. I was thinking of doing one like that with the ikara prop, the stock motor, and the 9.8 to 1 gearing, but I've got a bag full of N20's and both 2.5x.8 and 2.5x1 props. I sure hope nothing burns out in the reciever. This looks like the one I want to build.

Did you skeletonize the foam?


I'm heading to WalMart tomorrow.
Feb 02, 2003, 09:51 PM
Registered User
Awesome progress. It is starting to sound like a winner!

What is the n20 motor? Is that like one from a standard servo?

I guess I'm going to have to find some magnets and learn to wind coils.
Feb 02, 2003, 11:18 PM
The effect is sadly temporary
Hippo's Avatar

This is it:

The N-20 Motor

Shown just about actual size.
Feb 03, 2003, 12:27 AM
Foam rules
Thatovalguy's Avatar
John, I'm soooo glade to here that. as you were posting I was building. I did motor tests all afternoon and came up with using the 2508 prop, a tick under the 2510 in trust but way under in amp draw. I need to get a U80 to try out. Still waiting for my charger for my polys, guess I'll have to make one while I wait for the backordered one.

Still cutting frame out, didn't Know how far to go but i'll keep trimming till it gets to where I want it.
Last edited by Thatovalguy; Feb 03, 2003 at 12:30 AM.
Feb 03, 2003, 12:42 AM
Foam rules
Thatovalguy's Avatar
By the way, I have over 4 hrs of testing time so far using a N20 and 4 cells on the stock board. No signs of a problem so far. One thing is to connect the positive motor lead direct to the batt negitive to the board. Suffers less voltage drop this way. Test it with a volt meter first, dont want to short the board out of any thing.

By the way glide tests prove fine. Need to hook up some power now.

John how many wraps on the coil you made?
Last edited by Thatovalguy; Feb 03, 2003 at 12:45 AM.
Feb 03, 2003, 07:55 AM
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Jgardner's Avatar


The one I flew was not skeletonized. I think it could be if the weight is a problem. The strength is a nice plus.

The coil was wound from the wire in RS's smallest relay. I just wound till it looked about as heavy as a DU and tested it. I have no clue as to the number of winds. The car's stock coil was at about 12 ohlms, so 28 was plenty. The rudder works with authority.
Feb 03, 2003, 07:58 AM
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Jgardner's Avatar

Great Tadpole


That is a great Tadpole. I think you take much more care than I in building. It is only on the third or fourth iteration that I start to think about neatness and precision.
Feb 03, 2003, 11:15 AM
Foam rules
Thatovalguy's Avatar
Thanks but thats just thrown together, needs the corners sanded and rounded. Did trim off more foam, empty it weights in at, lets just say .5 oz. I found the tape no one likes at work today, the super thin clear stuff that you can't find the end of. Going to skeletonize tonight, even though I know I have enough thrust, I want to lighten it up some more. Never can be to light.

The next one I'm going to trim the sheet thickness in half, this stuff is plenty strong. Also going to try heat bending the wing curve next time. Also the width of the body can be much narrower too, its about 7/8" wide.

Checked the weight of parts before hot glueing and after, found this method adds nominal weight to it as long as you go sparingly.

All in all happy with the first complete foam airplane I've ever built.
Last edited by Thatovalguy; Feb 03, 2003 at 11:20 AM.
Feb 03, 2003, 09:46 PM
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Jgardner's Avatar

Another Tadpole

This one has a red cap Zip Zap motor and a 2.5X08 prop. It weighs in at 14 g AUW. Same airframe specs as the last, 16" WS.

Tomorrow I hope to be able to test the two of them out.
Feb 03, 2003, 10:12 PM
Registered User
Wow, I can see right through that thing! My meat hooks would crush it just trying to plug in the battery.
Feb 03, 2003, 10:39 PM
Got helium filled wings?

lookin good

what are you using to center the rudder?

due to the dihedral in wing you could remove elevator to reduce tail weight and turns would be just as smooth

anyone try using brushless motors from computer cooling fans?
Feb 04, 2003, 12:43 AM
Foam rules
Thatovalguy's Avatar
Went and wound a 61.4 ohm coil tonight, more power, was shooting for 50. Used wire from a old battery clock. Skeletoning the plane out didn't help much just a couple grams, oh well, looks wild though. Glide tests at 30 grams ballast proved fine so now its just finishing the thing off.

Next one I will have to trim some thickness from the foam and make it a lot thinner across the width of the fuse.
Feb 04, 2003, 11:52 AM
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Jgardner's Avatar

Centering and test flights


I just used tape to center the rudder. The cheap tape which is thinner did not stick. Back to 3M Scotch tape. Sticks better and centers well. The actuator has lots of power, so this is fine.

Test flights:

Zip Zap a bust at 14 g. The N20 w/U80 prop was too much. It would go too fast and climb too fast. The ideal prop might be a 3X1 prop. I am not sure there is such a thing, however. So far the winner is an N20 with less prop than the U80. The 2.5X08 is next. Perhaps the two to try next two variaitons with that prop, one with a bigger wing.

The plane was controllable all the way across the gym and the rudder worked fine. Another plan would be to just scale up the plane by 30 percent and use the U80.

I need a simple way to attach and move the battery fore and aft. Perhaps magnets on the battery and a strip of very thin steel or music wire.

Lots of things to try.
Feb 04, 2003, 03:29 PM
Foam rules
Thatovalguy's Avatar
Might try a resister in line to cut motor speed. Need the 2 speed setup using the duel coil clone. One on the resister for cruse and one for power and clime for at the end of the flight, or with wheels for takeoff.

How about thin strip of velcro for the battery?

2508 or 2510 should do it. The 3020 seems like to much.
Feb 04, 2003, 03:55 PM
The effect is sadly temporary
Hippo's Avatar

or the "cruise" mod.

I was thinking the same thing about two speeds, but you can do it on the single coil model too.

Just wire F to the motor, and B to the motor through a resistor. Use two little diodes to keep F and B from shorting to each other. Then you can use Reverse for level flight, and Forward for climbing etc. That's what I'm going to try.


Ah. This should help.
Last edited by Hippo; Feb 04, 2003 at 04:06 PM.
Feb 04, 2003, 04:00 PM
Sticky Shepherd
Graham Stabler's Avatar
It is nice to see e-man and skelecor working together for a change.

By the power of blue foam...... I HAVE THE POWER


p.s. applogies
Feb 04, 2003, 04:04 PM
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Jgardner's Avatar


My understanding of electronics is weak, so help me out. If I add a resistor to a motor circuit will the current be the same but the motor only gets part of the power and the resistor gets part? Thus, with the modificaition for cruise, the battery drain is relatively constant but you get two power settings?

This could still be worthwile given the lipoly energy density. At 850 ma the 145 might last almost 10 min. A lower amp drain and a single power setting might be good too. Mike Cross' Minnow would fly forever on a charge. It used a geared car motor.
Feb 04, 2003, 04:13 PM
The effect is sadly temporary
Hippo's Avatar

Well, it's been a long time since electronics class...

But, if my understanding is correct. Ohm's law states that:

Current = Voltage / Resistance

So if you increase the resistance at a constant voltage, you should get less current draw. I'm sure in the real world, some energy is lost in the resistor as heat, but you should still use less energy with it, than without. Therefore, hopefully flights that aren't greatly reduced by the process.

I hope,

P.S. Graham, that is hilarious! (unless anyone is looking. )
Feb 04, 2003, 04:28 PM
Foam rules
Thatovalguy's Avatar
Wasn't thinking, that should work fine. The switch rest state is negative, on is positive.

Laymans terms, the resister is the valve only lets some voltage thru not all, some minor loss, but should increase run time.
Feb 04, 2003, 04:51 PM
Foam rules
Thatovalguy's Avatar
One of the guys over on the bit thread is using a 2.35 ohm resister for cruise, a starting point at least.

I'm torn between building a Selman actuator or a bird. Would like the first to keep weight forward, so I'm leaning toward the first option, we'll see.
Feb 05, 2003, 03:06 PM
Foam rules
Thatovalguy's Avatar
Went bird style on the actuator, now I think I'm going to have to limit the throw.

But first I'm going to remake the plane. First the nose needs to be a touch longer and the wing needs to be moved back or I'm going to need lots of ballast in the nose and the fuse could be way thinner. The 1oz auw is a little scary so chuck it and start over. I'm going to try splitting the 3mm I have. This should make for a really lite and strong air frame. Also my wing plan is 14x3 and I'm going to try Johns 16x2.5 wing. This will also bring the cg back some.
Feb 05, 2003, 03:42 PM
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Jgardner's Avatar

Yes and yes

The balance can be a problem. Until something flies reliably, it is hard to know. The glide tests I have done are not perfect matches to the powered performance.

The two Tadpoles I have ready for testing tonight or tomorrow have really strong throws both in terms of force and angle. I may have to put on stops or cut down the rudder size. Future versions could have lighter coils and smaller magnets.

Both have N20s with GWS 2.5X08 props. The first has the 16X2.5 wing which makes for a fairly fast plane. The other has a 3 chord and 17 span. Both are more heavily built than the bitchar-g version.

Off to smash, er, fly airplanes soon.

Feb 05, 2003, 11:48 PM
Got helium filled wings?

been working

you guys are really moving along
given away secrets here
magnets and steel are so heavy to hold down battery
i have used beeswax on balsa floors for years
don't know if will work on F3
take beeswax ball and melt on battery in center
take strip of beeswax and melt with covering iron onto floor
then push battery onto strip -cold
you have to remelt spot now and then on battery
use sponge to put even pressure on ends when in combat
Feb 06, 2003, 01:18 AM
Foam rules
Thatovalguy's Avatar
Found a problem with the readyboard, its made of a dense foam which is strong but heavy. Would be good for a Extra or something of that nature, not this.

My new tadpole came out way lighter but I had to cut it so thin ((( 1.25mm))) for the wing and fuse sides, ((((3/4mm)))) for the top and bottom fuse capping. The horizontal and vertical stab are 2mm. 10 grams empty which should come out at 20 grams all up. I did git scared and put a stiffner in the wing center section which caused about a gram.

Glide tests with this one are really nice. I added more incedence to the wing on this one too. Now to figure out the up thrust required so power on and off are relatively the same. Even bought a new car to strip for this one.

Going to have to try durovent next time. Really don't want to buy fanfold right now or I would start building something bigger.
Feb 06, 2003, 11:08 AM
The effect is sadly temporary
Hippo's Avatar

Another Tadpole on the way.


I finally got started on my own micro plane. Looks like (with some allowance for glue) that the airframe will end up about 10g. So, with 3.5g for the battery, and 2g for the receiver, + 6g for the motor and prop, I'm hoping for around 20g in the air.

Here's the parts. They don't look any different than your ordinary Frog...

Until you see it next my other Frog...

Now I've just got to get some 145ma Li-Polys, and I'm off and running.
Feb 06, 2003, 11:34 AM
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Jgardner's Avatar

Better results today

Flew the smaller wing version today. The connector wire broke on the larger wing version, so it was not tested.

This is the 16"X2.5" polyhedral wing version. It could make multiple trips around the gym, perhaps three, but would not climb. There was significant tail fluttering, so a centering magnet is in order. I have some of Forcefield's smallest, so that shouldn't be hard. I need to rebuild with the Rx further forward, as the balance could have been a bit further forward.

The power system seems good. The N20 with GWS 2.5X08 pushed it at a nice indoor speed. I should be able to shed a gram of weight, center the rudder, and reposition the Rx to achieve better flight characteristics.

We are so close. I will weigh the whole mess tonight and build two new versions a bit more refined.


That looks so much better than my crude versions. Your design skills are showing through. Attentioin to detail shows through as well.

Note that my last couple were made up with the bottoms of the fuse sides glued directly together and a V shape achieved by gluing an oversized strip of center-cut F3 on the tops. The excess is trimmed off after gluing. This made for an easy assembly, lightened it a bit, and used the inherent strength of triangles.

You may also want to try a fuse entirely of center-cut F3. The stuff is incredibly light. Peeling the F3 may yeild the same results, but I used the skinned for wings, so there is always some center cut available.
Feb 06, 2003, 11:46 AM
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Jgardner's Avatar



I hope you can make it work using alternative foam. The split F3 is hard to beat, I think, but flexibility in materials would be good.

Sliced block foam might be worth pursuing as well. Do you have a splitting rig? You can assemble one from an old model train transformer and a piece of cutting wire from the Woodlands Senics display at your LHS (~$3).


Great potential for beeswax. The battery dosen't need much holding in the V shaped fuse I have been using lately, since it jams in the shallow V angle. A bit of beeswax on the battery only, and a gentle pinch could be all that would be needed given that it is up against very rough foam. Well worth a try.

Feb 06, 2003, 11:53 AM
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Jgardner's Avatar

Frog family in the air together


How about three sizes in the air together. Standard Frog, FrogBipe size, but with the real Frog form factor and single wing, and the Tadpole. That would be a real treat.

A fourth size is possible with the RFFS-100, KP-00 and about a 1.5 oz AUW.

I am not sure about a supersize Frog, however.

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