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Old May 23, 2012, 04:14 PM
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Multiplex KA-6e

Hi guys,

I have inherited a Multiplex KA-6e, with 'vintage' servos and no instructions. My first big scale glider, so very excited!

I am replacing all the servos, but have a few questions.

What range of movement do I need for the (all moving) tail - will +/- 7 degrees be enough, or do I need more? And any ideas about aileron r.o.m.? The model came with some c.o.g. marks on it, so I am planning on using those. Oh, and what incidence should the tail be to the wing?

What is flying like? I am envisioning a big middle phase, but anything I should be wary of?

I know it is an old model, but hopefully somebody will have some memory of it! The youtube videos look good.

Many thanks

Simon
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Old May 23, 2012, 04:23 PM
Life-abstract=conformity
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I think that's the first I've heard of a MPX KA-6.
Prolly won't believe it til I see it either (hint hint).
Full flying stab on a KA6? IDK about that either.
Wing/tail incidence (decalage) is typically ~ 1-1/5deg. Pos or Neg is the question.
Ailerons? Depending on wing span vs. ail. length/chord, IDK this either.
Maybe some picts and details (dims) would help.
Skies
Jay
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Old May 23, 2012, 04:34 PM
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Photos tomorrow, when I find my camera (recently moved house).

And soon when it is flying!

I know I should probably just 'suck it and see', but thought I would get as much info as possible first
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Old May 23, 2012, 05:04 PM
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so. cal.
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The MPX KA6-E is a fine flying model to this day, I am sure someone will chime in on the incidence, I believe you need a little more down elevator at neutral then the fairings on the tail would indicate. The models thermals very well.
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Old May 23, 2012, 05:09 PM
MTT
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@Patitifa & AirBorn One :

It is old !
But as they say, oldies are goodies !

MPX made the Ka6 kit in the 70's and 80's, I believe, 1/4 scale, which translates to 3.88 m
It was a scale model of the Ka6e, so the full flying stab is correct.
And +/- 7 deg should be more than sufficient.
I had a Ka6e, in the same scale from another manufacturer, and the required deflection of the stab was less than that.
I have never seen one, but from what I read on the german RC-network forum, it's like any Multiplex model : Good solid allrounder, more for relaxed thermal flying than wild aerobatics, no bad habits.

Wing/tail incidence differential : 1.0 - 1.5 deg is a good starting point, positive, of course, i.e wing has 1.0 -1.5 deg higher AOA than the tail

Found this: http://www.grossegler.de/Ka6mpx/Ka6.html
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Old May 24, 2012, 12:12 AM
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I had one of these, a fantastic model to fly, one thing to watch out for is the stabs have an a symmetrical section that must be installed upside down so as to pull the tail down, as a result there will be approximately 3-6 mm at the leading edge above the leading edge of the of the fairing. Otherwise you'll need a heap of lead to make the model fly at those angles. From memory I ran 2-1 differential of up to down in the ailerons and about 50% rudder mix.
No nasty habits and does very big ellogant aerobatics.
All in all a great model.
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Old May 24, 2012, 01:00 AM
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Here is the K6E datasheet from the British Gliding Association.

I used to be a full-size glider inspector and instructor in a former life!! I've flown both the K6BR (elevators and small canopy) and K6E (all-flying stab with large canopy) and they are very nice.

If you scale the control deflections down they won't be far wrong. What I usually do with all-flying stabs is have a larger than needed range of movement (especially 'up' elevator) and use exponential to make it less twitchy around neutral then try a short test glide.

Multiplex have an online instruction archive that includes some of the older gliders but the K6 is not there.

Cheers

Gary
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Old May 24, 2012, 05:12 AM
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Thanks guys, all really helpful.

Hadn't picked up on the semi-symmetrical tail section. Will check it when I get home.

That data sheet was useful - tail has +/- 12 degrees r.o.m!
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Old May 24, 2012, 06:54 AM
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The upside down tail is a Multiplex thing from that era, there are two theories, one is that it provides more down force at high speed to prevent tucking under and the other theory I can't remember (must revisit the forum I read it on!). My MPX Fiesta has an upside down stab and it doesn't seem to make much difference.

The full-size K6 stab range of movement is designed to give full up elevator with the control stick on the backstop which coincides with stalling in level flight. On some of my models with stabs I make sure that there is enough movement to stall/spin them out of thermals.

Not sure if the full-size K6 is the same but the K18 (which uses virtually the same wing) has a clever mixer that raises both ailerons with full up elevator (more washout to prevent tip stalling at low speeds).
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Old May 24, 2012, 10:36 AM
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Not sure if the full-size K6 is the same but the K18 (which uses virtually the same wing) has a clever mixer that raises both ailerons with full up elevator (more washout to prevent tip stalling at low speeds).[/QUOTE]

Now that's an interesting point I wasn't aware of the aileron mix being employed in full size, would hate to imagine the matchbox required to mix that together.
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Old May 24, 2012, 11:21 AM
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On my fullsize E model the ailerons go up a bit with up elevator.
The linkage is somewhat simple looking.
On a modern flapped ship it's a different story.

Regards Dean
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Old May 24, 2012, 04:01 PM
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Photos attached. I know it is a little grubby - it does need a good clean/ repaint to get it gleaming white, and I'm thinking of glassing the wings this winter - but first priory is to get it flying!

I must confess that the tailplane does look symmetrical to me. And please forgive the somewhat untidy cockpit - it will be gleaming.

And I know the pilot seems a little out of place - would it be so wrong of me to call him Viper?
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Old May 24, 2012, 04:16 PM
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Cracking, look after it!!

That tailplane deffo looks symmetrical to me as well.

GB
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Old May 24, 2012, 06:43 PM
Life-abstract=conformity
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Fantastic Patitifa!
Surely can't correctly judge from a photo but the stab appears asymmetric to me.
Good score!
Skies
Jay.
P.S.
Quote:
It is old !
Glad you said it and not me MTT
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Old May 24, 2012, 11:48 PM
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Congratulations Simon she's a ripper. Just a thought one of the modifications the guys over here started to do for better access was to cut the fuse out just in front of the joiner box and half way across the leading edge therebuy giving you full access to the servos between the wings. The hatch is held inplace with a lacky band as a just in case but the wings also hold things in place, makes life much easier!
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