Planks- R-Swept, Ellipsio- miniplank 1S brushless - Rear motor FPV - Page 3 - RC Groups
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Apr 15, 2016, 08:20 AM
“There’s no place like Foam”
gpw's Avatar
Nice flyin’ Basic !!!
We built several 1/2A planks using Ace Foam Wings ( some time ago) , and they were pretty WILD !!! ( no throttle , ride out a full tank of fuel ) But one , that I think was called “Shoe” ( American Aircraft Modeler mag ? ) , had very large tip fins which added a remarkable dihedral effect , and it would right itself ... smaller tip fins wouldn’t and had to be “flown” constantly ... just something to play with ...
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Apr 15, 2016, 08:52 AM
Laughs at un-boxing videos...
basicguy's Avatar
Self righting on a plank wing? that is pretty wild. .049 powered cool.

I used to fly planks control line. They were elevator only. Had one with a Enya .35 that would run 60' lines in 3 seconds a lap, about 90 mph and was about 20% larger than these. I still have the motor.

If I make bigger one it is going to be a motor glider. I have mental plans for a micro and a higher performance one.
Last edited by basicguy; Apr 15, 2016 at 08:57 AM.
Apr 16, 2016, 08:57 PM
Laughs at un-boxing videos...
basicguy's Avatar

New plank, slope

Taking a bit from Rusty Mustard and others, I decided to build a lightweight sloper plank.

30" span 10" chord 2 9gr servos 6 channel flysky receiver 150 mah 1s lipo cell (stole from one of my wife's helicopters.) Because of the low voltage I am not using a BEC.

The elevons are 3x9". I used the Thomas B. method for control rods. I put on a central rudder rather than the wing tips that I have been using. Just because.

I am using a KFm 2 type of wing with a 2mm spar 3.5" behind the leading edge.
The weight of it in white is 80 grams with battery. giving it a wing loading of 1.4oz/sqft.

We have a gentle slope on my pasture flying field. The wind was 20+ all day thus the reason for building. I finished it about dusk and the wind was diminished to probably 8-10. The longest glide was about 6-8 seconds. I flew it several times without any real problems, I had to take out most of the reflex down to about a 1/16" and had not done any leading edge shaping.

If the wind holds tomorrow I am going try it again.

Need to figure out where I need to be to keep it in the air.
Apr 17, 2016, 02:56 PM
Laughs at un-boxing videos...
basicguy's Avatar

video of flying in back yard

My slope flier in the back pasture.
plank slope KFm2 wing. (0 min 23 sec)

Not there yet but a start.
Apr 19, 2016, 05:47 PM
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basicguy's Avatar

New Plank, The Ellipsio KFm2

Decided to explore an elliptical wing. Making it an ellipse 20x14" as I had a partial sheet of black foam left over.

Using the tried and true string method of drawing an ellipse. I don't use CAD, I traced a line in the shape of an ellipse. It is still in nutball territory but will fly with elevons.

I did a few test glides in the house with a 180grain lead weight taped to the nose and it flew but stalled so more. I have yet to figure out how to calculate the cg at 20% of the wing area. I thought perhaps if I take 20% of the circumference and measure it along the leading edge I might come close. Trig was 50 years ago.
The wing area it calculates to be 219 "^2 and the circumference is 53.8".

Have not decided how to power or if I should power it maybe just slope it. Speaking of slope, I did some research and found 2 public dams that might work, the nearest is about 14 miles sloping SW and a second (facing S) about 20 miles the other direction. There is larger dam levee that faces east about 50-60 miles away.

Apr 24, 2016, 08:20 PM
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basicguy's Avatar


It is done enough to fly, Seems more stable than my nutball
Weight is 125 grams at this point.
24 gram 2050kv motor. 6x4 prop two 10 gram servos 6 channel receiver and 20 amp speed controller. 800mah 2s battery. Was hoping for lighter equipment but went ahead and flew it with what I had at hand. Wing loading is 5.5 oz/sq foot.

Of course no plane can be considered viable without a proof of flight video.
Ellipsio plank flying wing KFm2 (1 min 30 sec)
Apr 25, 2016, 06:24 PM
Laughs at un-boxing videos...
basicguy's Avatar


Simple tapered box fuselage.

Using a 5.5x4.3 prop it pulls 13 amps with 3s. It is a blast.
Apr 25, 2016, 10:38 PM
Watt Waster
Tsavah's Avatar

Not as Straight Plank Wing

It does make sense the rounded wing would be a good flyer. Do want to see more about it and videos. Any ideas about what might make it better would be good to read. Thanks.
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Apr 26, 2016, 07:43 AM
Laughs at un-boxing videos...
basicguy's Avatar
I only know what I read, The elliptical shape is supposed to have advantages in induced drag and wing loading allowing for a thicker wing at root where the wing is needed to be thicker for strength. Google.

I don't suppose that the either is that critical or even relevant for the model. Have read that ellipical shaped wings tend to have adverse yaw. I think if any, mine has proverse yaw. I have not tried rolling it as the battery attachment was just tape. Wanting to keep the G's positive for the moment.

The shape that I have used is definitely an elliptic but not extreme. I didn't want to have the weight and complication of a spar so I kept the wing span short.

There are tons of other rounded shapes that others have built. This is just one.

Get your ball of string and a couple of thumb tacks out and draw one.
Apr 26, 2016, 05:07 PM
Laughs at un-boxing videos...
basicguy's Avatar
A video flying it with 2s 800.
Ellipsio plank flyingwing c body (2 min 37 sec)

Not shown in the video is that it rolls perfectly when I use a touch of down elevator. I think I give it a bit of up elevator inadvertently when I roll . Bad habit.

The rudder has a bit of flutter. Perhaps I will remake it from MPF rather than DTF and tie it to the rear of the fuselage.

I think my scale must have been funky, My retangular planks are close to 250 grams. This one is 205 grams.

My next one may have a more stretched appearance. Maybe 30x14. Perhaps it will be easier to film.
Apr 28, 2016, 09:25 AM
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basicguy's Avatar

Wing area, CG and wing loading calculator for Ellipsio

I am a numbers guy. Hardly a day goes by that I don't have a spread sheet open doing something.

The area of an ellipse is pretty easy to calculate Pi/4*h*w. To find the segment that would represent the cg line is a complex equation and really deserves a spreadsheet. I wish my math skills were sharp enough to derive a solution for the distance back to get a certain CG percentage but did use an equation in the spreadsheet that you can put in a cg location and it gives me the percentage.

I determined the CG empirically by test flying and ended up at 3.25" back of the leading edge which turns out to be 18%. I have flown it with cg's further back, makes it handle faster and it lands lighter power off.

Here is the spreadsheet that I have written.
You will need a spreadsheet program that can read an Excel file, most brands can.
May 05, 2016, 10:58 PM
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basicguy's Avatar

Video of Ellipseo on 3s

ellipsio flying wing running again (2 min 14 sec)

Flying on 3s pushing 15 amps on my rewound Keda 24 gram motor.
Prop is 4x4.5 paddle blade.

Still very stable. Probably my favorite tonight
May 13, 2016, 09:58 AM
Laughs at un-boxing videos...
basicguy's Avatar

My mini Plank variant.

My latest plank is called my miniplank.
AUW is 1.4 oz
WS 14"
150 mah cell
Brushless motor.

It is big for a micro and small for a standard I put the details on the micro scratchbuilt and indoor subforum:
May 15, 2016, 08:30 AM
Laughs at un-boxing videos...
basicguy's Avatar
Worked on the details of the mini plank. Using some thin foam from a plastic foam plate. I made a two piece cover for top. Gluing the back down I put a front cover that wedges at the front and use a small rubber band near the back. Shaped and reduced the vertical stab. The motor mount is a small piece of vinyl siding. Too brittle to cold bend, I put on a line of hotglue and bent it over a brake.

Also air brushed some orange on the top of the wing.

Flew it at sunset last evening. Definitely is faster
May 16, 2016, 10:30 AM
Watt Waster
Tsavah's Avatar
Doesn't look to have a KFm step, or airfoil. Interesting set-up. Would love to build one like it, but will need to understand the RC parts better. I don't think I have on hand what you used.
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