Especulus - just another low wing sports plane! - RC Groups
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Mar 13, 2011, 09:58 PM
Mr. Brazilian Nut
Rho's Avatar
Build Log

Especulus - just another low wing sports plane!

I have been scratch building a low wing model, based mostly on E-Flite Advance 25e.

My project is a tail dagger instead, it has a longer wingspan (138 cm = 54 / in), larger control surfaces, four channels, and a cowl.

The chosen airfoil is NACA 2412, semi-symmetrical, with a 4 dihedral angle.

I'm building it with balsa and some ply wood.

Some drawings below.

Hope you enjoy, and I will need some help and opinions....
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Mar 13, 2011, 11:02 PM
Visitor from Reality
Hi Rho
Good start - a plan. Your NACA 2412 wing section is one that will work well for sports aerobatics.

Main aim is to build it strong enough for your flying, but as light as possible. I have just built, and am covering, a similar sized model. I estimate it should fly at around 64 ounces / 1.82 kilos and think I could have made it lighter. There are some construction photos in this thread:

Taildragger - much more fun, plus you only have to buy two wheels! Cowlings always make this sort of model look better too.

Good luck with your project - ask away.

Mar 13, 2011, 11:14 PM
Mr. Brazilian Nut
Rho's Avatar
Hi Dereck,

It's an honor to hear from you in my thread!!!

I have been following your New Kid On The Block, and it's very inspering!!!

I'm quit sure it will be under 2 kilos (70,5 ounces), as I have built an high wing aerobatic model, 55 pol ws, and it weights only 1700 grams (55 ounces) ready to fly.

Some pictures of the wood job.
Mar 20, 2011, 05:31 AM
Mr. Brazilian Nut
Rho's Avatar
I could not get it under 2 kilos. Her final weight, ready to fly, is 2040 grams (71-72 ounces).

My set up:
Motor - Turnigy SK 3548 - 900 kv
ESC - Turnigy Plush 60A
Ailerons - 2 servos HXT MG 14 - mixed as flaperons - 2.2kg/cm(4.8V)
Rudder and elevator - D-MG16 Metal Gear 2.9kg/.08sec/18.8g(6.0v)
Battery - Zippy 1P4S 4000mA 20C
Propeller - 11*7

The ship had its maiden last Friday, when it was already dark, with low visibility conditions. Yesterday was very windy and I didn't take a chance.

Hope to fly and record it today!!!!
Last edited by Rho; May 29, 2011 at 11:21 AM. Reason: see comment below
Mar 24, 2011, 02:14 PM
Mr. Brazilian Nut
Rho's Avatar
And she flies!!!

Just watch the video and tell me what you think of it; plx.

Speculus - Asa Baixa Elétrico (6 min 24 sec)
Mar 24, 2011, 05:46 PM
Visitor from Reality
Hi Rho

Looks good to me. Handles take off and landing well, good, smooth flying inbetween.

Reckon you've built yourself a good sports aerobatic model there, Congratulations!

May 29, 2011, 10:54 AM
Wood Chucker
Lacquerhead's Avatar
First off, another beautiful plane Rho. Very pretty construction. It's almost a shame to cover it!

I put your power system into Castle Creations' flight calculator and found some interesting things. It seems like most people (myself included) use much less prop than the power system can handle. It's not a bad thing since everything stays nice and cool but it may be good to know the upper limit of what the system can handle so you can get the maximum performance for the amount of weight you're carrying.

According to the calculator your setup should be putting out about 250W. Power input is 320W but the motor's maximum is 835W. A larger diameter prop may not be practical but if you can swing a 13" prop you can get 364W output drawing around 45A with 2.4kg of static thrust. A 11x6 prop on 4S would start to push motor temperature up but with a 10% margin it should be safe and produce 464W output with 2.5kg static thrust at a 41A draw.

So, you have plenty of room to experiment with prop pitch and diameter if you would like a bit more wind over the wings.
May 29, 2011, 11:19 AM
Mr. Brazilian Nut
Rho's Avatar
Hi Lacquerhead,

I have mistyped the battery.

Actually I'm using 1P4S 4000 mA, swinging a 11*7 Xor wood prop!!!

And your calcs are absolutly corrct because my system gets a little warm, and I have to take care with full trothle otherwise my batteries puff a little...

So I have edited the information above.


May 29, 2011, 11:37 AM
Build more, websurf less
FlyingW's Avatar

Nice plane, and really nice landings.

Good luck with her!


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