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KNUFFAN
Feb 14, 2006, 12:09 AM
Ive been trying all kinds of different control linkages on my planes lately--boredom and weather helped in the process... The pull pull with very fine motor wire is not only extremely light, but it centers better than the hard pushrods on even the sub 4 gram servos. Maybe the load is just that much better balanced.? Pull pull is also very fast to put together and dead simple to adjust on the fly. Just 2 cents worth. Also noticing that a little 7 inch prop is very cool for indoor pattern--I was sure that a bigger diameter prop would have to be the thing but now Im not quite so convinced-On my 5 oz Knuff and Elite (both monoplanes) the 7 inch really works better for me. Just food for thought,.,.,.,
Erik Johansson
Feb 14, 2006, 02:44 AM
I loved how the 7x3.5 GWS prop felt on my Knuffel. It sounds horrible due to the rpm, but it really felt good in the air.

As far as pull-pull goes, itīs really the only way to go if one wants the lowest possible weight and best control. The germans have found that Berkley Fireline (the thinnest one) along with Cormoran Corastrong (0.08 mm version) works the best. It seems other lines tend to slack when it gets cold outside... if flying outdoors with your indoor planes that is... :)

/Erik
Kimmo Kaukoranta
Feb 14, 2006, 03:18 AM
How do You guys adjust the tension and centering of the pull-pull lines?
Aio_1
Feb 14, 2006, 07:10 AM
...The germans have found that Berkley Fireline (the thinnest one) along with Cormoran Corastrong (0.08 mm version) works the best. It seems other lines tend to slack when it gets cold outside...
Is there any problem with kevlar thread that you know of?
I was thinking of giving that a try.

Aidan
KNUFFAN
Feb 14, 2006, 08:42 AM
Yep, kevlar seem to work well. I kind of like the thin motor wire because it doesnt change with temperature and can just unwind one end at the servo to tighten or center the surface. Plus, there isnt any real stretch to deal with. Its weird, but most all of the stuff I didnt like about the 3.6 gram servos is not so noticeable as it was with pushrods. Time will tell.
Trisquire
Feb 14, 2006, 09:47 AM
Some guys get more throw by using a long servo arm and short control surface horn. I'm wondering how that works with pull-pull. I would think that unless the arm and horn are the same length, you would get either slack or tension as you move the arm.

Regards,
Tom
ZORCY
Feb 14, 2006, 03:11 PM
if its pull pull, how about unwaxed floss? and how do you tighten it up, that seems tricky.. would CA shrink enough to pull it up a bit?
Devin McGRath
Feb 14, 2006, 04:14 PM
I use a combination of monofilament and fireline. two pieces of fire line and one piece of monofilament in between for each line this give you a pretty rigid surface with a little bit of stretch to expand and contract with the foam.


Devin McGrath
UltraBob
Feb 14, 2006, 05:56 PM
Kimmo,

I use kevlar thread for my pull/pull. Although this isn't a picture of a pattern ship I have used this method on some of my foamies. I use a small piece of c/f rod and shrink tube and use the small dubro pushrod connectors. It's easy to adjust the tension and centering this way.

I forgot to mention I use a small drop of CA to secure the thread and shrink tube to the c/f rod.

Bob
dcronkhite
Feb 17, 2006, 10:49 AM
Kevlar isn't going to stretch with temperature changes and I find it easier to setup quickly than other methods. I don't particularly like the connection hardware in that picture just because I think there are lighter ways to do it.
Erik Johansson
Feb 17, 2006, 11:02 AM
How thin is the kevlar thread? I prefer lines thinner than 0.12 mm (0.005") and thatīs why I choose the Fireline. I will try some 0.06 mm Dyneema fishing line Zero stretch in normal temperature, but some stretch in freezing conditions. Not a problem though for my indoor-only planes. :)

I agree with Doug about the hardware pictured. Itīs too heavy for my taste.

/Erik
Aio_1
Feb 17, 2006, 11:59 AM
...I agree with Doug about the hardware pictured. Itīs too heavy for my taste...
However you could easily use a short length of very small diameter piano wire with a "Z" bend to connect to the servo arm in place of the carbon rod and clamp fitting. Also you could use a "V" bend in the wire both as a tensioning spring and for adjustment. I might try that.

Alternatively I might mould a very simple little fitting from a couple of strands of carbon tow. Shouldn't weight more than 0.05g!

Aidan
sno
Feb 18, 2006, 01:02 AM
run the line through a couple holes on the servoarm...pull it snug and twist it under the servo arm screw, tighten screw
dylan roberts
Feb 18, 2006, 07:57 AM
hi all, on my shockflyer im using the dubro micro(or mini, cant remember)pull pull system, i threw out all the extra stuff just using the line and ferrules. to adjust just squeese ferrule open and recrimp. someone told me the line is the stuff doctors stich u up with, i think they said it was catgut or something like that. it does not sretch or become slack with climate change
ChrisBowker
Feb 18, 2006, 10:39 AM
catgut is what the vet uses ;) searisly. my dad is a vet and we used the stuff all the time when i was younger on planes.

Chris
David Kyjovsky
Feb 25, 2006, 01:50 PM
Look at this page (http://www.rcmania.cz/modules.php?name=News&file=article&sid=499) to see how I have solved the pull-pull on my Roller Shocky. It is good to use long arms on both servo and control surfaces - in such a way you minimize slop and the effect of low tension. Low tension usually appears in cold, where the plane "shrinks" a bit. Still, no big deal.
Trisquire
Feb 25, 2006, 05:22 PM
David,

Thank you for posting the link. It's good to hear from another elite F3P flier.

Could you tell me how much control surface travel you use? Mechanically it makes sense to make the control surface arm the same length as the servo arm. However, depending on end point adjustments, this limits your control surface travel to 30-40 degrees one-way.

Is this adequate? Some fliers keep the control surface arm short in order to get 60 degrees of travel one-way.

Regards,
Tom


P.S. Perhaps you can post some information on your Endorphine plane?
wrenwright
Feb 25, 2006, 07:57 PM
Yep. Pull-pull is pretty neat. What is there not to like? It's sure a lot easier to setup than long, sloppy pushrods.....

Fly high....
David Kyjovsky
Feb 26, 2006, 12:46 PM
David,

Thank you for posting the link. It's good to hear from another elite F3P flier.

Could you tell me how much control surface travel you use? Mechanically it makes sense to make the control surface arm the same length as the servo arm. However, depending on end point adjustments, this limits your control surface travel to 30-40 degrees one-way.

Is this adequate? Some fliers keep the control surface arm short in order to get 60 degrees of travel one-way.

Regards,
Tom


P.S. Perhaps you can post some information on your Endorphine plane?

Tom,

I use the servo arm longer, for the Shocky in any case. This one has some 60° + for elevator, 50 or so for rudder, not sure about ailerons (45 or so).
Such throws are very difficult to achieve with any pushrod. The need to get such throws actually made me to use the pull pull... and I will never look back :)

As for Endorfine, the production as far as I know just about started. I just hope that they (MS Composit) will design some more colour schemes. They have a very skilled guy for that...
The specs are 78 cm wingspan (may differ a little bit), 95 cm long, AUW 150 - 160g. Flies pretty well, the actual setup (throws, CG, differentiation etc) limits or helps the flyer much more than the actual plane.
For the curious ones who dont know what we talk about:http://www.rcmania.cz/modules.php?name=IndyNews&MediaOp=show&idMediaAss=s460&MediaName=En4.JPG&MediaNum=1