Thread Tools
Nov 08, 2009, 04:13 AM
Registered User
davereap's Avatar
Thread OP
Build Log

The CYCLONE a KFm4 delta for two BW motors, with differential and deflected thrust

The Cyclone design was originaly posted at the end of my Superfly clones thread, simply because it was supposed to have a Superfly shaped wing.

However a simple measuring mistake when cutting has changed the wing shape, and now that I have it all sorted, and it has become a very different machine and an excellent performer, I am posting the design as a new build log.

The inspiration for my Cyclone came from the Goolie design posted by Paul Cook
and after a couple of posts marked its similarity to a Superfly in its wing shape, I decided to modify my KFm4 Superfly clone design to take the twin motors..

Working in Sketchup it was an easy job to modify my plans to take two motors. I designed the plane around two BW motors using 8" props in slots.
To get the performance I was going to build with all 3mm depron, and having previously built a few wings, I increased the wing span slightly from the Goolie to achieve as low a wing loading as possible
Last edited by davereap; Nov 08, 2009 at 04:55 AM.
Sign up now
to remove ads between posts
Nov 08, 2009, 04:13 AM
Registered User
davereap's Avatar
Thread OP
Ive started on the Cyclone.. here are the lines, and so far ive cut the main layers all in 3mm depron..
Note the span on my model has been raised to 30".. this is because I think my build will end up slightly heavier than the stock Goolie. I wanted a touch more area now at 2.5 sqft) in order to get as low a wing loading as possible for the best slow flight..
I am going KFm4 again, but the step positions are altered to get the slots forward to help achieve the COG..
Remember KFm4 is a step on top and an identical step on the bottom. See the earlier superfly construction for general methods..

On this build because the LE is close to the spar there is no additional depron spacer needed between the layers, just a 3/4x1/4" balsa spar at the step line

I am not going with an upper fuz, but I will have top and bottom fins in 6mm depron, and an enlarged lower 2 layers of 6mm depron.
In my normal fashion I will leave the top clear for the multiple velco strips I use for fixing the battery etc.

Increasing the size to a 30" span was a good move the final AUW came in at 13.5oz with a 1250 3cell lipo.. this is 5.27oz sqft ...the 28" goolie was 4.4oz sqft..
Possibly another couple of inches span would have reduced the loading, but it is going well enough at this size
Last edited by davereap; Nov 08, 2009 at 06:55 AM.
Nov 08, 2009, 04:14 AM
Registered User
davereap's Avatar
Thread OP
The build has progressed...a similar build to the superfly at the begining of this thread. but note the distance between the LE glued areas and the steps is small depron spacer/spar is needed
One silly mistake ive just noticed, for lots more extra strength I should have taped along the wing before I fixed the fuz and fins..still its supposed to be light weight so stresses should be minimal.. time will tell..I might yet remove the fuz so I can tape across the centre section, then replace the fuz, if it comes off easily
edit...the fuz was too well fixed to remove so the taping was only made on the exposed surfaces...however flying and crashing has shown the wing is more than strong enough as I built it, so no worries
Last edited by davereap; Nov 08, 2009 at 04:41 AM.
Nov 08, 2009, 04:15 AM
Registered User
davereap's Avatar
Thread OP

fixing motor mounts

Info on shapes
The Superfly shape makes for an excellent delta , the kit versions are well worth buying.
However using the KFm4 section or a KFm2 with the superfly shape gives a low cost clone alternative, which flies excellently. It is also a quick build..
With the superfly the original size has always been the most liked, that was about 27" span.
The Goolie is produced at 28"
The CYCLONE is 30"

Ive now mounted the motor mounts..
Ive use the tube type.. first I cut them down to fit against the step.

Then I use a drill to extend the line, and after lining them up with pre marked thrust lines, I fixed them in place with cool melt adhesive

The mounts are locked in place with multiple depron strips, using uhu and cool melt to gap fill.. and when fully blocked in the block is rounded off.

Lastly cutouts are made for the motor, and to get at the mounts fixing screws
Last edited by davereap; Nov 08, 2009 at 04:53 AM.
Nov 08, 2009, 04:15 AM
Registered User
davereap's Avatar
Thread OP

Tape it up

Been taping up and fitting the elevons and gear..Taping over depron is essential, it adds more strength than you would think, and makes depron much stiffer when the tape is on both sides..I always fully cover my elevons etc with this tape and reinforce all the areas that can be seen in these pictures...
Without the tape depron will tear in an impact..with tape not much damage, and since its been flying ive already rolled this plane into the ground with bad hand launches a few times with no dammage at all

Only the control rods and REC remain to fit

The AUW will be 13.5 oz with a 1250 lipo its 5.27oz sqft ....the 28" Goolie comes in at 4.4 oz sqft...
Last edited by davereap; Nov 08, 2009 at 05:09 AM.
Nov 08, 2009, 04:16 AM
Registered User
davereap's Avatar
Thread OP
Notes on other parts.

Fuz and Fins...
The central lower Fuz is made from 2x laminated 3" wide lengths of 6mm depron... Fitting requires some cutting out, to seat the front of the fuz against the slope of the outer layer.. the rear of the fuz behind the step fits flat, so is no problem.. The front of the fuz is shaped round and the rear is tapered down to about 1.25" depth at the back..
The lower fins are cut from 6mm depron one layer thick and are also 3" in height, cut to length for the location of fitting.. again they need fitting over the slope at the front, and the rear portion glues flat.. again shape as you like... When fuz and fins are fitted the plane sits on all three bits nice and level
The top fins should also be 3". Fitting on the opposite side of the wing.

Both fins should be simple triangle shapes, which is a change/mod from previous pictures. In flight the plane was weathercocking due to the original fins being too large, so I chopped them down

Make sure they are all vertical and line up nice and parallel to the planes centre line..

Recap on the specs
KFm4 wing all in 3mm Depron..each step is 9mm deep (1/4+3mm).. Balsa spars 1/4x3/4..
span 30"..AUW with a 1250 lipo is 13.5oz..wing loading 5.27oz sqft..
motors BW 1300kv.. props APC 7x5 push / pulls..Thrust available 20oz+
servos 2x - DYS 9gm
esc any cheapo 10-12A
rec Corona 2.4Ghz 4ch
Last edited by davereap; Nov 08, 2009 at 05:18 AM.
Nov 08, 2009, 04:16 AM
Registered User
davereap's Avatar
Thread OP

Setup and programing the motors

Ive finally got the motors running as they should, the programming is a bit unusual..

these settings are for a futaba ff9c

Plug one motor into the throttle channel and one into the rudder channel
using two programable mixes
On a FF9 mix 1 throttle to rudder is +100/+100 the mixing should be on...but the link option should be off
On the mix 2 rudder to throttle I use -90/-90 again the mix should be turned on
note + and - .. settings they are very important

dual rates.... on the rudder you can have 0% as the down rate, letting you turn off the differential if you want at the flick of the switch

When you run up the motors they should run up together.. If not make sure the link option is off..
With two identical motors they should be spot on, however slight differences can be resolved with trim, or end point settings
My two motors bought together reved up together from min to max.. measured on a tacho meter
now give left and right rudder.... for left input the right motor should come on, and vice versa..
If it comes on the other way round just swap each esc lead over...try again
Last edited by davereap; Nov 08, 2009 at 05:37 AM.
Nov 08, 2009, 05:38 AM
Registered User
davereap's Avatar
Thread OP


Flying.. The big surfaces deflect the airflow and make this highly responsive.
Make sure you have some well downrated settings at 50% to use and have loads of expo, 70%.. switch off the differential thrust using the downrate rudder... fly and trim..
At slow speeds this will roll fast, on full rates against a breeze it will roll fast without going anywhere.. The deflected thrust really makes it manouver..
Once sorted switch on the motor differential and enjoy.
Try the powered spin and you will see why its called the Cyclone

does it go....oh yes vertical like a rocket....sweet..and I am only using 1300kv motors and props that will be better on 1500 or 1700's
Last edited by davereap; Nov 08, 2009 at 07:38 AM.
Nov 08, 2009, 07:55 AM
Registered User
slick power setup fer sure.
Nov 08, 2009, 12:02 PM
Registered User
davereap's Avatar
Thread OP
heres a video from its first flight.. the motor here were not sync'd , only running together at the low to middle setting I was using to cruise around at,and it was only later that I got the programming sorted... now there are no problems with the flight, and I just need some dry weather to get some more video
Cyclone (3 min 1 sec)
Nov 08, 2009, 04:52 PM
Zen in the art of foam
djacob7's Avatar
Nice design, Dave!
When you tape the plane, how do you treat the KF step? Do you keep the sharp corners or does the tape take a slant on them?
Nov 09, 2009, 05:11 AM
Registered User
davereap's Avatar
Thread OP
The steps are kept square and sharp or they dont work... I usually tape from the front, and think its best to fully cover the top and bottom layer, and then trim along the step line, rather than folding the tape down..
I am also coming around to the opinion that I might as well cover the whole of the airframe, including the elevons. because the tape makes a vast difference to the damage resistance, it stiffens the depron as well as preventing any stress tears if you do hit the ground. The extra weight of the tape is negligable on this type and size of aircraft.
Tape covered multi layered depron can take very heavy impacts

The colored tape makes for easy decor, but you can decorate the wing then tape over with clear tape, or, tape with clear then paint over with something like Humbrol enamel which seems to work ok
Last edited by davereap; Nov 09, 2009 at 05:22 AM.
Dec 14, 2009, 09:08 AM
Registered User
davereap's Avatar
Thread OP
heres the latest video.. I modded the top fins to stop kiting..Its now going a real treat
cyclone 2.AVI (4 min 19 sec)
Dec 14, 2009, 12:26 PM
Registered User
Dickeroo's Avatar
The CYCLONE KFm4 is one plane you don't want to mess with in the air. This is a pit bull of the sky. I love it.
Dec 15, 2009, 03:31 PM
Sussex, UK
RobinBennett's Avatar
It looks like it's got a good speed range, and very nice low speed handling.
Have you tried the high-alpha stuff that the superfly does so well?
Does the differential thrust allow hovering and knife-edge flight?

Quick Reply

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Superfly and Superflea clones KFm4 in depron davereap Flying Wings 204 Sep 07, 2019 02:25 AM
Mini-HowTo A differential thrust steering device parrot pilot Power Systems 1 Oct 28, 2009 10:35 AM
Build Log The Jonas Racer (a really fast delta with KFm4-profile) boopidoo Foamies (Scratchbuilt) 0 Aug 21, 2009 06:31 AM
Differential thrust from two motors? HankF Parkflyers 3 Oct 15, 2003 09:34 PM
How Much Do You Increase Thrust With Two Motors WillowPtarmigan Power Systems 3 Sep 30, 2003 08:03 PM