Kyosho A6 Intruder challenge - RC Groups
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Mar 28, 2012, 08:07 AM
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Kyosho A6 Intruder challenge

Bought a Kyosho A6 Intruder on sale, my first EDF ...

I knew it wouldn't be easy but reading the following two threads I started to
get a bit sceptic ...

Anyway I've started to test and try to figure out what is wrong with this
A6 Intruder bird from Kyosho.

What I've found so far who is not mentioned directly in the previous/old threads:

The DF-55 duct housing is flexible a gentle squeze my deform it so there is a
"big" gap between fan blades and the housing. This may result in a significant
loss of thrust. The blades may even touch.

The fan quality is not great either one of the blades touched. So both the
duct housing and the fan was/may be elliptic ...

I bench tested stock (no modification) apart from grinding of the touching blade
and got peak static thrust 360g with a 3S 1000mah 25C LiPo.

Added a tail cone to the BL innrunner to reduce turbulence behind the
motor this added 10g of thrust (370g peak)

Reduced the gap between fan and duct with layers of tape. This resulted
in 390g thrust peak, 370g continous.

I'm puzzling with the thoughts of trying to balance the fan dynamicly.

So the reason for "measly" thrust claimed may be that the fan unit was squeezed when installed (double sided tape installation )

I also noticed the seating for the duct in the fuselage is not even.
There is small "humps" from the casting process (who should be sanded
off before installation) to get a even surface for a easily deformed duct.

Weight: In the instruction manual they specify Epoxy as glue for the fuselages
wings etc. Epoxy is a heavy glue mostly suited for metal and/or wood materials
not foam. I will try to use polyurethan glue (Gorilla glue) much less weight
and as far as I'm able to detect better bonding to foam. I hope this will
reduce all up weight.
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Mar 30, 2012, 09:53 AM
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Fuselage duct testing

Started testing again this weekend.

Was able to reproduce my previous result but I'm not sure my numbers are 100% correct. It looks like the output is varies with the temperature of my 1000mah LiPo.

Cold LiPo meagre trust readings 300-320g then the after a few burst
it's heating up and I got 385g peak ~370g continous.

The ducted fan unit is vibrating a lot, need balancing obviously but I'm not
realy competent of doing that yet (a bit afraid I will destroy the unit in the

Installed the fan in the fuselage (taped together and with all slots sealed off)
To figure out what causes most backpressure the aft fuselage duct or
the front I split one of the fuselage halves (see photo) to get a gigantic
cheater hole.

Installed the fuselage with the fan in my test bench and now the thrust reading
was reduced to 330g peak 306g continous. Obviously a lot to be done with the
aft fuselage.

I then added the front fuselage piece and taped it. My trust reading was now
down to 270g

The fuselage ducting is reducing thrust significantly probably around
25%. In addition it's easy to get a bad fan duct installation (the double
sided tape solution from Kyosho making things even worse).

So when people claimed that this bird would not fly and asked for help.
They were most likely misslead when all kinds of setup trouble was
mentioned as the probable cause.

My preliminary conclusion so far to get this thing flyable the fuselage ducting
has to be modified a lot before the fan is able deliver what it's capable of.
Apr 02, 2012, 07:01 AM
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Found another thread about the A6

Did som further testing the aft fuselage proved to be difficult to improve much
made a rough attempt with two cartoon tubes taped together in a Y branch
the thrust result was similar to the stock solution. Did a foam version of the
Y but no success it was worse than the stock.

Did some small mods aft added a tail cone the the BL motor and aligning
the fan a bit tilting the duct a bit top forward.

The only realy successful mod has been to cut a 50mm dia cheater hole
in the bottom of the front fuselage. This added 30-40g of thrust.

The A6 is indeed a challenge to get well performing. I'm probably wasting
time trying to modify the aft end but I've learned a bit more EDF I believe.

It might be an idea to do the Y tube in smooth plastic to reduce surface
friction but I'm afraid weight added might be bigger than the thrust increase.
Last edited by FLOEY; Jan 04, 2013 at 08:18 AM.
Apr 02, 2012, 07:24 AM
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Sketch of my modifications
Apr 02, 2012, 12:22 PM
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Small break through

Was able to get my rough paper tube Y to work better than the stock version

Measured a thrust of ~320g peak for a several seconds until the battery began to
fade. I must start thinking of balancing the fan ... to save energy.

I believe a modification may pay of if done properly. My rough paper ducting
with lots of tape is heavy with a rough surface and unsuitable for e.g. flying
in wet conditions.

The problem is to find the best combination of plastic sheet stiffness/weight
suitable for the duct. It also must be possible to cut the plastic with heat.
Apr 03, 2012, 01:50 AM
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A6 Ducting

Another great thread
Apr 03, 2012, 02:54 PM
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Made it!

Finaly I made it

Replaced my cartoon ducting with Depron ducts (only in center) just
tested and got 339g peak thrust / 324g continous (if we say that 360g
was fan only) it's about 90% of the thrust! It was a quick test so I might
have a false reading or something ... hopefully not ...

I've read that some claim 20% loss in split duct solutions I've got 10%
loss (very non scientific testing ... just a kitchen scale)
Apr 03, 2012, 09:18 PM
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Sherlock's Avatar
Dang, you are putting a lot of work into it! Looks like it is paying off Nice job.
Apr 04, 2012, 02:08 AM
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Originally Posted by Sherlock
Dang, you are putting a lot of work into it! Looks like it is paying off Nice job.
Thanks sorry about the bad photos ...

When I read all the "can't get it to fly need help" and the rather "helpless"
replies I understood it was something realy wrong with this plane.

I felt sorry for them. I know how frustrating it is to get a new plane who
just does not fly.

So I took this as a challenge and try to realy figure out what was reality
and what was fiction since I accidentally had bought this "lame duck".

To me it looks like most of the problems claimed by the previous unhappy
owners where true. The plane will most likely not be able to fly assembled
the way Kyosho suggest.

Kyosho could have corrected this with some replacement parts (better
split duct, tail on the BL motor). In addition a improved user/assembly manual
with advices of where to put the cheater hole and how to align and fix the fan.

Sorry Kyosho but Your EDF design/prodct developers failed with the A6 Intruder.
Those who defended Kyosho in this case should have rather have investigated
this properly and not denied the problems, my view
Apr 04, 2012, 06:46 PM
corsair nut's Avatar
great mods! i always liked the looks of this model, but could never grasp the price tag lol. my plan was to put 2 high power 40mm power plants in it.....
Apr 05, 2012, 02:48 AM
Not enough hours in the day
Slaanesh's Avatar
I don't think the A-6 lends itself to be a very good EDF model for the simple reason that the ducting is a nightmare if you are trying to use only one EDF unit.
Another case in point, the J-Power/Skyangel version of the A-6 has some of the worst ducting I've ever seen and it's flight characteristics seem to back that up.
Some of Kyosho's other jets, namely their 45mm series DF-45 suffer from inefficient ducting. The Kyosho Vision in particular. The Illusion and Mirage to a lesser degree.
It's a pity because these are other wise fantstic looking models which would perform really well with a little more effort in regards to proper ducting.
Apr 05, 2012, 10:57 AM
Registered User
Originally Posted by Slaanesh
I don't think the A-6 lends itself to be a very good EDF model for the simple reason that the ducting is a nightmare if you are trying to use only one EDF unit.
Spot on! The A6 is realy a twin.

I did not know that Kyosho also had "problems" with the more straightaft ducting too.

One error puzzles me is how they managed to get the fan unit in the wrong
angle according to the duct. That must be a design error who has been
overlooked in the development process not a bad idea.
Apr 09, 2012, 02:18 PM
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The A6 Intruder flew

My modified Kyosho A6 Intruder flew first atempt. CG was spot on
~103mm from aft edge. I landed it as a glider. Tore of small piece of the
right wing edge. It was raining slightly so no video sorry.

AUW 492g with a 3S 1000mah 25C Lipo.

I launched it with a hard throw full throttle it climbed so the thrust
was OK for take off one hand, no helper.

Spoted one problem after landing (wet and muddy ground) some
dirt went into the fan through the cheater hole.

I'm puzzling with the thought of adding rudder.
Apr 14, 2012, 04:20 AM
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CG and Expo

I added rudder to my A6 the weight grew up 508g this caused the CG to move
aft (too much aft), my Lipo (90g) had to be moved forward. I could not reach
my previous 103mm CG, it became 101 or something like that see photo.

The second test flight showed that the CG was still pretty "perfect". The
plane dived slightly (upside down ) in a roll so the CG could be even further aft
I believe.

I also (instead of expo on radio) selected to install the pushrod a bit different than
Kyosho suggested. I used tha inner most servo horn hole and the outer most
aileron hole. To get max torque and smooth movement. Looks like it paid off.

Small modification I cut a channel/slot through the wing for the servo connector
so it's possible to replace servo without ripping the plane apart. It's angled
and ends up below the hatch (not visible with hatch on).

The hatch lock was also modified. The forward ply rectangle bracked to be glued
in the fuselage cracked before second flight. Replaced it with a plastic one.
The aft magnet is replaced by some wooden pins so the hatch in now
properly secured.

The magnet hatch solution ... the only RTF I've got who this works on is on
my slow flying Alfa Model Albatros (WW1 biplane). On a EDF? !!!

Note kind of disclaimer: This plane was previously reviewed for 4 years ago.
One of the reviewers claimed the first one lost due to a bad CG. If he had taken a
glide test (over soft ground, no power) that would not have happend.

DO ALWAYS real world test.

Be sceptic my experience and finding may contain errors ...

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