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Mar 09, 2011, 06:35 AM
Vertical Unlimited
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Back Down Under... but the fleet continues to expand!


Alas the Canadian experience came to an end last June. It was awesome - from the surreal experience of genuine snow, to the vivid summer green, to the amazing Fall colours. An experience to be savoured. Now it's back to 100'F, olive coloured leaves and yellow grass. However, the sky is nearly always blue and we fly all year... but I flew year-round in Canada too!

First New Plane – Hobby King Sniper Pushy Cat EP
I ordered a Sniper Pushy Cat EP from Hobby King to "tie me over" while I waited for my gear to be shipped from Toronto. What a beauty! I built it initially as a belly-lander, with the intent of fitting retracts later. I fitted a 400W Hobby King motor and 2200mAh 3S Lipo for serious motivation. The first launch was a complete disaster - not enough airspeed, so it tip-stalled in and rekitted itself!

Luckily I only busted one of the tail booms. I don't know how I got so lucky. The ground is HARD here! I glued it back together and had my buddy and ace-flyer Kristian launch for me on the next attempt. He was a bit freaked by the prop, and everyone gasped as it tip-stalled again... but this time Kristian's firmer throw and my thumbs starting on the sticks meant I caught it. It flew very well after the initial launch, and trimmed easily into wide, fast circuits. After a smooth belly landing Kristian commented “nice plane, but it needs wheels!”

After this “proof of airframe” flight, I stripped it down and fitted Hobby King pneumatic retracts. These cost a paltry $36 and seemed as good as “best in class”. I used Carl Tulenko’s method to fit the mains, comprising 2 x ply beams oriented “on edge” as a pair of half-span spars. The mains retracts were then mounted between the beams. The plane was flown again, and rose of ground beautifully from a local sports field. Time to fit rudders!
Sniper EP retracts action.mp4 (0 min 31 sec)


I cut a pair of rudders from 1/8” balsa, and mounted them using tape hinges. The rudder servo was placed under the tailplane, as per the elevator servo. The only challenging part was joining the two rudders. I used a carbon rod, strung between two control horns, with easy connectors on the horns.

The final “proof” flight complete with rudders and retracts showed this was a great plane. It was now fully aerobatic, capable of spins and other rudder manoeuvres. It was only slightly heavier than the original prototype, and despite the CG shifting a bit further back, only flew better. I had omitted the motor box in the original build and mounted the motor directly to the “firewall”, fearing CG issues – this was a wise choice.

Final task was to pretty it up and make it presentable. Now she looks as good as she flies.

Back to the AMD Hawk DF
In early 2005 I bought a BAe Hawk ARF from AMD Hobby. It was supposedly quick to build, with the catch-phrase “buy it Monday, fly it Sunday”. They didn’t specify that they meant the following Sunday! This was quite an undertaking. Not as bad as my original scratch-built Hawk, but still a bit tricky, with a lot of the engineering needing rework to get it sorted.

I ordered a set of air-up/spring-down retracts from AMD with the original purchase, and these proved to be nothing but trouble. They leaked despite all my best efforts to get them to seal. New O-rings made no difference. Regreasing didn’t help. I just couldn’t get them to work, and lost 6 months trying. In the end I hit up AMD for a refund, and they obliged – damn good customer service considering I’d disassembled them so many times!

It was now mid 2006 due to the delay with the retracts, and also significant issues at work. By this time I had a new job in Saudi Arabia, so the Hawk was reboxed and left in storage. When I returned to Australia in mid 2010 I found it safe and sound, so I pulled it out and got back to work on it. Wow had things changed in 4 years! My original power source was to be a K&B 100 DF and a Ramtec fan. However, electric flight had come on in leaps and bounds, with me keeping up while overseas. Suddenly it was possible to get even better performance using an electric power system! I ordered a Big Screamer outrunner, Ramtec EDF, Castle ICE 160HV ESC, and 2 x 6S Turnigy Flightmax 30C 5000mAh batteries. Tony Roessen at Trim Air provided excellent service. The Ramtec GDF was pulled out of the Hawk, and the EDF dropped in – nice compatibility! Initial tests on 8S and then 10S revealed this fan was a serious piece of machinery, as I saw the highest power numbers EVER on my watt meter (103A, 3500W!). Each spool test ended up with something being blown over in the workshop. The eventual test on 12S exceeded 5500W, but ended in disaster when a pack of servo plugs resting under the jet were sucked up into the intakes, destroying the fan. Tony Roessen furnished me with a replacement in quick time.

The Hawk is now ready to test fly, after a lot of careful work getting it right. I installed a set of Hobby King all-metal retracts, still air-up/spring-down, and they have worked flawlessly. She’s a bit heavy, but I’m hoping all the thrust of that screaming Ramtec will overcome any weight issues. I’m going to need those flaps on landing!

BAe Hawk motor test and taxiing.avi (1 min 27 sec)


New Flying Field
Last item on my agenda upon arriving home was to find a suitable flying field. In Canada I lived just 10 minutes from the OMFC field, which was fantastic – I never flew so much in my whole life! However, my beloved former club MADMAC had moved from the convenient location in Pinjarra, 30km from my house to Waroona, over twice as far away. I paid them a visit and had a good flight on their exquisite field, but it’s just a bit too far to go. Again my buddy Kristian came to the rescue, finding a local farm only 10 minutes away that was keen for us to come and fly.

It started out as an unkempt field, but the tenants asked if we wanted to mow some runways. I just about jumped out of my shoes! I explained that I’d bring my own lawnmower, and they said “don’t bother – use our ride-on mower”. It just doesn’t get any better! I spent a couple of hours mowing new runways, taxiways and even a pits area. I’ve since flown my Extra 300 from it, and found it to be “adequate” although a bit pot-holed in places. I’m sure it will mature into a nice field.
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Sep 05, 2011, 08:41 AM
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chuckflem's Avatar
Wicked cool!!!
Sep 07, 2011, 08:44 AM
Vertical Unlimited
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Quote:
Originally Posted by chuckflem
Wicked cool!!!
Thanks Chuckflem! I don't get many comments - not sure why not. I try to keep a fairly full blog.

Good things are coming! Sadly the Hawk crashed on maiden. Good flight, but I flew too long (just 4 minutes) and ran out of battery. It hit a tree in the emergency landing approach and was destroyed. I'm now rapidly building a Trim Air Spectre - pics coming soon!

Cheers, Straight Up
Sep 30, 2011, 08:15 AM
Registered User
Hi,

Just got the Sniper from HK, and I got no manual at all.

Where do you suggest the CoG ?

Do you think a 1600kv motor , 3S and 6x4 propeller will be enough ?

Tchuss

e_lm_70

ps: Going to hand launch , no plan for mount the landing gears

pps: Did you put two servos for ailerons ? Or only one has the servo hole shows ? ... and how do you stick the servo for the elevation ?


--------------------

EDIT .. Actually I found the manual on the HK site ... anyhow .. any tips will be nice to have
Oct 12, 2011, 08:50 AM
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chuckflem's Avatar
http://www.ejf.com/index.php?main_pa...x&cPath=89_224

do you think a necelle kit on the pushy cat would work out?
Sorry to hear about the Hawk. Fear of losing planes detered me for a long time but I finally got over it and got into flying. Its worth the risk as long as you don't lose one too often.
Oct 15, 2011, 12:33 AM
Vertical Unlimited
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Thread OP
Nacelle kit could be made to work. You'll have less static thrust than a prop, but more dynamic thrust and therefore probably higher top-end speed. I'd target 300W/lb power loading. Budget 2.5lb flying weight so you'll be chasing 750W. Probably best done on 4S. HET Typhoon 2W-20 would be a good motor, turning a Wemotec Mini Fan (70mm), or equivalent 90mm fan. The 90mm will give more static thrust.

BEWARE hand launching with an EDF. This plane gets going quickly, but I found it VERY difficult to hand launch. It's not easy to hold, and prone to snapping as it leaves the hand. I crashed mine on its first hand launch, and only just saved it on the second.

1600Kv on 3S will work with a 6x3 prop, pulling around 450W. You'll get more static thrust if you use a lower Kv with a bigger prop. 1000Kv will draw the same power on a 7x5. For hand launching you will be keen for static thrust.

I used one servo for the ailerons, in the stock location, using torque rods. Elevator servo is wrapped in masking tape and then glued to the tail with silicone.

Go with stock CG to start with, but I prefer to have mine 20mm further back for a more neutral feel and less down when inverted. Don't start at this point.

You'll save a lot of weight by not using landing gear, but hand launching is hazardous. If you end up using retracts, mount the mains as far back in the wings as possible.
Oct 28, 2011, 09:52 PM
Registered User
Hi Straight Up. I flew this plane for about a year with a Turnigy C3530 1700 fitted until it had a servo failure and the plane was destroyed. Any chance of a few more pics of the area behind the motor with the wing off. Going to try and fit a glow 25 if possible to a new one.

Thanks
Rudolf


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