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Dec 12, 2009, 05:17 AM
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Build Log

"Pushy" a pylon wing KFm2 glider use for training and minicam


pushy1.AVI (4 min 50 sec)


The video shows the maiden flight of the Pushy, during which I trimmed and sorted out a couple of teething problems including the COG location.
First launch...rudder in reverse... I should have know better..
Second launch and third launches not shown, but the flights were ok except it was very nose heavy..
Fourth flight with the COG now at 50% .. shows the best results.. with a super glide and a very easyly flyable plane.. As it was it flew very well, the only criticism from me was the gentleness of the response to stick inputs.
Definately very well suited as a trainer for beginers with the small rudder and elevator, but I prefer to have more response, so I have enlarged the control surface areas.
It is waiting now for its next flight..
heres an inflight video using that minicam..
.
The Pushy a KFm2 glider for minicam (6 min 55 sec)
Last edited by davereap; Jan 16, 2010 at 03:42 AM.
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Dec 12, 2009, 05:17 AM
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starting the build


The Pushy design is similar to many other builds.. I was wanting a pylon mounted wing, around 48" span, and weight to suit a 1300kv BW motor. Other than that I hadnt decided on much else, so some of the build pics on the Fuz show extra depron in place, where later it was chopped away as the shape and build developed.
Be aware of this, I have made some sketchup diagrams to show the best way to build the Fuz, to avoiding wasting the foam..

First I made a wing

The span was 48" and the chord was 6.75... why because thats the size of a bit of depron that was going spare... There is no reason why you cant go bigger in span or chord... what depron and rods do you have spare?
Make the wing to suit what you have, but I would sugest keeping the chord between 6.5" and 8" and the span 48"-2M..Then the fuz can be kept to the same sizes and it wont look odd..

The wing is basicaly a normal KFm4.. however two new things are being tried..
one is the zigzag and two is the air gap below the zigzags

The zigzags are 1" deep at 45 degrees which gives a 2" spacing between the points along the length of the wing.
As can be seen in pic 2 the 50% line is midway between the front and back points, so the spars are laminated 1/2" forward of this 50% line..see pic 5
Last edited by davereap; Jan 16, 2010 at 03:44 AM.
Dec 12, 2009, 05:18 AM
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All laminating is made using UHU POR adhesive...any gap filling, servo fixing, is done with a cool melt glue gun...Epoxy is used for the wing platform to depron fix and reinforcement, the jointing of the tail..
With uhu put a thin film of the glue onto both surfaces..leave to dry.then push together.. position with care, you wont get two chances..
order of laminating... spars and cf rod to main 6mm layer... top 3mm layer to spars first.. then pressed down last onto the Leading edge.. start at the center of a panel and work outward using both hands at the same time
At the leading edge spread the glue to fix together the 2 depron layers for at least 1-1.25" width.... a steel rule is usually 1" wide so makes the marking up easy

LE and TE shaping
The LE is rounded to a semisymetrical shape.... the Trailing edge was sanded to taper it off ...note the sanding of the center section is done all off the top, but the tips are sanded a bit different... on the trailing edge of just the tip section, draw a line going from the bottom edge at the dihedral join to the top edge at the tip...This is the line that you want to keep as the Trailing edge ..so some sanding needs to be done from the top and some from the bottom to keep the edge on that line...The result is that you have sanded in some washout, which helps some gliders... stops tip stalling..

Make sure when laminating that you do it on a totally flat surface so the wing ends up flat.. I use a glass topped table to do mine..when adding tips make sure all is lined up properly...raise one end of the main panel to get the dihedral and have the other panel flat on the surface... keeping the build even and flat with no warps is essential... its not difficult but just take care
Last edited by davereap; Nov 08, 2010 at 06:22 AM.
Dec 12, 2009, 05:19 AM
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the fuz


Notes..
The motor mount used was a tube type..I slotted it into the top of the pylon and fixed it with cool melt.. the thrust line was at 0 degrees compared to the CF fuz tube

The wing incidence...I made the prototype at 0, but it needs at least 1 degree of positive...
.when cutting add 3mm to the front height on the pylon.. this is about correct..and is the thickness I added to the prototypes pylon

Pod shape Pic 1 shows a rectangle, but now is the best time to shape it.. the length in pic1 is correct..so keep to this length but enlarge the pylon and its wing plate if needed to suit your wing chord

FUZ length pic 1 the tube length should be the width of the pylon + 17-18" + the width of the fixed part of the tailplane
My wings were 6 3/4 chord... why? ...that suited an old bit of 6mm depron I had laying there, which I used for the main layer..Make yours to suit what youve got handy, or even to suit any old glider wings you might have..
My wings were 48" span...yep just right to get out of that old bit of depron..
Last edited by davereap; Jan 16, 2010 at 03:47 AM.
Dec 12, 2009, 05:19 AM
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As can be seen the pod was left till last to decide on length and shape..I first fitted all the gear, motor and snakes etc so then I could determine where the battery needed to go...
That then gave me the length of the pod.. from there I shaped the bottom and fitted the sides deep enough for the batteries..

After flight trials I have found that I could have had a shorter pod, but it flies well so I will leave well enough alone.. The length of the pod and the required 50% COG position now means I can use smaller batteries than I originaly planned for...

I first ballanced using a 1250 3cell Rhino, a prefered size, and the pod I made was to get the COG at 30% on the wing ( best flying was at 50%)...the battery at the front of the Pod then determined my Pod build length..
Last edited by davereap; Jan 16, 2010 at 03:49 AM.
Dec 12, 2009, 05:20 AM
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The tail feathers are a simple cross build.. cut them out, cover all and hinge the surfaces with the decor tape, slot and glue them together..I used epoxy..make sure they are all square..
The tail section is then glued to the Fuz tube..here I used cool melt glue.. then taped over to make a strong fix.
Last edited by davereap; Dec 12, 2009 at 08:14 AM.
Dec 12, 2009, 05:37 AM
occasionally things work
qacermacer's Avatar
Looks great! will you have plans?
In the vid " arhh you donk!"
Dec 12, 2009, 06:54 AM
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Ive not produced any fixed plans, but the drawings show the sizes I used... The idea is a variable build so you can decide the sizes to suit yourself.
The fuz will be about right for most spans and chords, untill you go too large, then it should be scaled up to suit
Last edited by davereap; Dec 12, 2009 at 08:20 AM.
Dec 12, 2009, 07:21 AM
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The micro cam I used to take the video in post 1..
Fitted on a velcro headband I wear it sitting on my glasses frame, on my forehead between my eyes. there is a depron wedge taped to its back which gets the angle correct for videoing
Dec 12, 2009, 08:02 AM
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Nice plane Dave. Does the camera change the CG or is your cover the same weight as the camers?
Dec 12, 2009, 08:08 AM
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Congratulations, Dave. Another outstanding design that you've come up with. You have made a tremendous contribution to the acceptance of the KFm airfoil concept. I can't thank you enough for that.

Dick
Dec 12, 2009, 08:20 AM
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The COG, cam on or off doesnt change much, but the battery has loads of space to go forward or back.. its one thing I am still playing with, even though its at 50% at the moment, I think I will be going further back..
Last edited by davereap; Dec 16, 2009 at 06:10 AM.
Dec 12, 2009, 08:45 AM
Onward through the fog.
Cybernaught's Avatar
Congrats on the new bird.

I finally got both the Pushy and Drenalyn vids to D/L. I haven't had much luck with single boom pushers but this one is intriguing. Three birds on the board at one time at the moment, but I'm tempted to try one. My more conventional planes seem to come out heavy.

You have a real nice trainer/AP plane there.
Steve.
Dec 12, 2009, 11:17 AM
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The Pushy came out heavier than I wanted at 16oz with the cam, but with its thin wings, the extra weight I am sure aids the penetration in the glide.. The use of a bigger area wing would let it fly slower, but better? I am not sure.
As it is its very stable, it cruises moderately fast, and climbs well on that BW motor. And the glide is nice and flat..Its quite stable enough to land itself, just let it do its own thing, throttled down in the correct place of course..

Now I need it to stop blowing and raining
Last edited by davereap; Dec 12, 2009 at 11:25 AM.
Dec 15, 2009, 07:56 AM
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I have made a couple of mods to the control surface areas enlarging them from the original sizes by about 1" along the edges.. these mods are shown in the drawings in previous posts.
I have also given the wing 1 degree plus incedence..again noted in previous posts..in building make the pylon 3mm higher at the front than the back..

After a lot of bad weather I am finaly getting some flights in ..so heres an onboard movie
.
The Pushy a KFm2 glider for minicam (6 min 55 sec)


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