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Jan 04, 2008, 01:25 PM
RJPIoW's Avatar
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Build Log

Fidgit 3D an 18" KF plane for UH10g outrunner and 24" larger version

I have been really playing with KF stepped wings and created a 23 1/2" span plane which I called Fidgit 3D because it was Very responsive, but would fly really slowly in a harrier.

I am delighted with the performance of the ubiquitous United Hobbies 10gm outrunner so decided to scale the Fidgit down to 100gm AUW 18" version. It flies really well and is very cheap to make from 3mm EPP so I thought you guys might like to see it.

There is very little CF strengthening as the KF step and top sheet provide the wing with all the strength it needs. I have braced the tailplane with 3x0.6 CF. The weight is made up as:

Wing skin 3mm EPP 8.2
KF step 3mm EPP 0.3
KF skin 3mm EPP 3.0
Fusalage 3mm EPP 2.8
Hinge tape & glue 7.0
Firewall 3mm Liteply 0.7
Firewall butress 8mm EPP 0.1
pushrods, horns etc 5
Rx Hitec HFS-05MS 8
Servos 3X3.7gm Torque 11.1
LiPo hexTronik 460mAh 2S1P 15C 29
Motor 18-11 2000kv Micro Brushless 10.0
Esc H-Wing Pentium 10amp 9.0
Prop GWS 7x3.5 4.0
Total weight 99 gm

The UH motor does take 4.3A off a 2 cell and the 140gm thrust is more than enough for the 99gm version, however, I now relaise that using a Corona 4gm Rx and a 13gm 350mAh 7.4V 2Cell and a 6gm HW Pentium 6A ESC would save a further 20gm so Ive bought all these.

I have flown this thing in 15 knot breezes so far and it handled well, I am jusy waiting for a no wind day to take a video.

Last edited by RJPIoW; May 24, 2008 at 04:12 PM.
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Jan 04, 2008, 09:20 PM
RIP - Caster Of Pods
Crash Hancock's Avatar
I am really digging on this plane! I have been wanting to build the Shark Bait, but since I have two of the 10g motors,I would like to build this one, as well.

Would you mind posting the PDF untiled?

Sweet plane, RJPIoW!
Jan 05, 2008, 12:24 AM
RJPIoW's Avatar
Thread OP

Untiled pdf - A1 sized

Here you go single page pdf

I notice that I forgot to add to the plan that I used 1.5 deg down and right thrust

Jan 05, 2008, 01:05 AM
RJPIoW's Avatar
Thread OP

weight saving

I could not think of a lighter method of attaching the ailerons other than 0.7mm piano wire rods attached to UH light weight horns. However at the rear I used cut down servo arms with the horizontal arm glued into the 3mm EPP, and kevlar line for a pull - pull arrangement on both elevator and rudder. Its light and works well and doesnt require longer servo arms for +/- 45 deg movement.

Jan 23, 2008, 02:59 AM
Baptised Heathen
batman's Avatar
Hard to believe there are not more replies to this thread. I have been looking for a foamy to build for the park and this is a real pretty looking plane. This will be my first venture into depron and K-F. I was looking for something a bit bigger so I did it on my printer in poster format and it came out at 24". I have not had any luck with any of the scaling and tiling programs including ScaleAndTile V3.
I am using 5mm depron but not sure of the motor yet. I'll get it built then pick one of those idle round things that I bought "just in case". I have everything cut out except the motor mount. Rj, could you tell me a bit more about the bigger version that you started with, please? What control throws did you use, any unusual flying characteristics, is the step just scaled up for the bigger one?
I do plan on using some 1700 3S LiPos for power and 3 9gm servos or perhaps 4 servos. I think a carbon fiber ribbon along the edge of the fuse top and bottom and maybe the front edge of the wing, I tend to get a lot of hanger rash, and a CF rod on the elevator.
Jan 23, 2008, 03:27 AM
RJPIoW's Avatar
Thread OP
Thanks for your interest. I have scaled the larger one up to 24" span and a pdf is attached.

I tried 2 forms of the KF wing. I used an 11mm high x 5mm EPP step across the full span, and a tapered step starting at 11mm at the root tapered to 0 at the tip. Both worked well, the tapered one did not have quite as much lift but penetrated in high wind better.

Forget the CF I hammer this one around a lot and it simply bounces and is ready to go - its very light. The KF step provides huge rigidity. I made the top skin from 5 and 3mm EPP during testing, the 3mm was slightly lighter , the 5mm needed more work to taper the leading edge.

The gear and motor performance is shown on the pdf. It has unlimited vertical with this setup !

Throws ailerons and elevator +/-45 deg rudder full throw within elevator.

I used 650 & 800mah 2 cells, your 1700 will be too heavy I feel.

Hope this helps. The bigger version is great fun and I fly it in high wind - wind when its difficult to stand up - , no wind, it hovers etc with ease.

Jan 23, 2008, 04:56 AM
Build 2 Bounce!
Very nice Richard, not sure how I missed this thread earlier though?

Looking forward to video when you get chance
Jan 23, 2008, 08:19 AM
RJPIoW's Avatar
Thread OP
I have a few photos of the 2 versions - the bigger one has been beaten about after many happy hours !

Jan 23, 2008, 09:55 AM
RIP - Caster Of Pods
Crash Hancock's Avatar
Thanks for the one page plans! I am hoping to get one of these one the building board this weekend!!
Jan 23, 2008, 10:41 AM
Registered User
Looks a bit like the Sumo 3D, but nevertheless cute. My depron from RCFoam came yesterday and I can't decide what to build! It's between the sharkbait and sumo, both of which are similar in size and shape to this (short and stubby.) Could someone who has flown both the Sumo and Sharkbait chime in on how they compare? I'm also anxious to see what people have to say about this one.

I'm looking for something super strong (I'll be using 6 mm depron) I can mess around with in the 2-car garage on windy/rainy days. The sumo, sharkbait, and mini fidget all appear to embody these qualities, except the sumo has a weakpoint were the tail joins the fuse. One thing I love about the sumo though is that the motor is protected because it's in the middle of the fuse, so no bent shafts. Maybe I could add a criss-cross made from piano wire to protect the motor on the sharkbait or mini fidget.

UH shipped my stuff yesterday, here's what I have to use:

8 hxt500 5 g servos
2 AX 2500kv brussless motors
2 9 g brushless ESCs

and lots of other stuff that's not relevant.

- Jeff

Oops, I forgot to inquire about something else. In the videos of these tiny planes it appears that the short stubby planes have atendency to roll by themselves. Almost like they are sorta twitchy and have a mind of their own unless you give them constant input. Also, on the mini fidget, is the kf-step inducive to 3D flying?
Jan 23, 2008, 11:13 AM
RJPIoW's Avatar
Thread OP
For longevity keep it light, & I now use EPP wherever possible. I have finally come to my senses and I now admit I was wrong and that Depron doesnt take as much punishment as EPP. The KF wing makes this one very stiff, so no CF needed.

Fidgit3D bounces well, Ive been learning 3D with it and making loads of mistakes. Roll rate is quick but it flies ok, best use rudder and aileron co-ordinated.

In the end its all down to presonal preference and any one of the 3 would do. Maybe the shielded prop on Sumo would be better indoors.

Apr 15, 2008, 01:19 AM
Registered User


This is one of the best planes I've built to date. Thanks for the design. At 99 grams AUW it can handle very strong winds (flags straight out). yet still slow down for some great front yard flying.

I'm not sure what it is about the design, but it sure works. By the way, mine is outfitted with the same basic equipment as your original except for an 11 gram outrunner instead of a 10 gram.

Thanks, again, for the plans.
Last edited by Salt; May 01, 2008 at 11:15 PM. Reason: I forgot a comma.
May 01, 2008, 12:00 AM
Registered User

Fidgit without KF

I'd like to make a larger Fidgit, but I only have 9mm EPP. Is it the sweep of the wing that makes it fly so well or the KF strip?
May 01, 2008, 12:36 PM
Registered User
yardboz1's Avatar
Great looking plane, thanks for posting the 24" plans. I also will be using 9mm EPP (no 10 gram motors currently, but I do have a spare 24 gram) and am curious about the same thing as Salt. No KF = poor flight or just CF rods to stiffen?

May 01, 2008, 02:01 PM
RJPIoW's Avatar
Thread OP
Originally Posted by Salt
I'd like to make a larger Fidgit, but I only have 9mm EPP. Is it the sweep of the wing that makes it fly so well or the KF strip?
Sorry haven't been seeing your entries not sure why ....

All the sized proptotypes Ive made with the KF wing had tremendous wind speed capability. Ive been out on balmy windless days and floated about at low speed and Ive taken them out on days when you can hardly standup and they penetrate really well. The KF wing holds its shape in gusty conditions, has low drag and good lift

The KF wing improved everyplane Ive tried it on, it makes an epp wing more rigid torsionally.

The wing shape is the result of mods to several prototypes. One prototype used a mid mounting for the motor, but I found it very noisy so abandoned that thought.

Ive made several sized variants, let me know what wing span you want to build with the 9mm and Ill happily mod the original plans for you.


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