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View Full Version : Fighting a Hacker Osprey...


bugjam1999
11-08-2007, 03:12 PM
Hello all,

After much ado, here is the "i've finished building the plane, will it fly" thread. this links back to a previous thread or two here:

http://www.wattflyer.com/forums/showthread.php?t=26236

but basically i've had a Hacker osprey Seaplane for ages that i bought as a finished but unflown kit from the same guy who sold me his easystar. Knowing i needed to learn to fly first, it has sat on my shelf for... oh, it's been over a year. I should note i haven't been able to fly for all of the intervening time, but anyway, it's been getting dusty.

Firstly i tried to fly it with the 13T motor that was fitted and a 8-cell nicad... underpowered was one description, useless was another. Luckily i visited the USA last month where upon the recommendation of the technically minded and infinitely helpful Dr Kiwi, i bought a LightflightRC 28-37-4 and thunder power 3C 15, 2100 lipo pack. The motor is fitted and it spinning a graupner 6X4.

From some google related searches, it appears that two versions of the kit were orignally available, an electric model, with a larger dihedral and no ailerons and a petrol/nitro version with the same fuselage, but with a wing with less dihedral and ailerons. Mine appears to be the petrol version with a electric conversion. Having said that, the motor mount looks just the same as the photos i can find in reviews for the electric one so either someone who vaguely knew what they were doing built it, or... who knows.

Anyway, one 30amp esc, two hitec hs-81s and a supertec 3003BB complete the electronics. The motor pod is slightly skewed left on the wing, so i mount the motor through some of the other holes in the fron plate, resulting in it being stright but with a bit more down-thrust than it should have. I figure this isn't going to much of a problem...

Right... first flight. So battery charged etc etc i headed out before work (why do i do this? oh yeah, because it's too dark afterwards...) to have a go. All trims set with surfaces straight, expo and reduced throw on the ailerons and the elevator and away we go... climbed straight out of my hand with a gentle throw and up she goes... and up... and up... and up.... holding quite a bit of down elevator and pressing the trim down resulted in me running out of trim? hmmm... plane just about balanced at full down trim, i start flying left and right circuits.

Plane is VERY sensitive and frankly, a bit of handful. It's flighty in all directions and slow to react to the ailerons. I can't get it to trim correctly left or right and so have to get it about right and keep correcting it. It's flying a bit nose up i think, probably something to do with the motor mount and the trim being off. It does, however, have loads of POWER :D and will fly happily at a constant height on just over half throttle.

I try a few aerobatics, out of interest. The one roll i do drops a heartstopping amount of height inverted... but then it wasn't very tight because of the reduced throws so maybe thats fair enough. The one loop i attempt goes fine for the first half, then the plane spectacularly drops out of the loop pointed vertical and trys to spin to the ground... i recover and decide not to try another.

Soon afterwards the battery quits... bit earlier than i was expecting, but then it's the first flight on the pack and it needs a few to "get going". I didn't time it, but guess about 6 mins...

Plane glides like a brick compared to my easystar, about the same as my stryker i reckon. The hyper-sensitive elevator makes it hard to get it to a) glide and b) level to flare slightly for the landing, resulting in me hitting a wingtip first and ripping off a tip float and some of the covering. Arse. Theres no structural damage however, this is going to be a 10minute repair.

Walking back to the car i notice the elevator is a little twisted which i didn't notice before and don't think is accident related; i'll reheat-shrink it.

First impressions: needs tinkering. I need to fix the float/covering, sort the motor mount to remove that downthrust to what it should be and untwist the elevator. I also need to throw the supertec servo (that came with it) as far as i can and buy a decent servo for the ailerons to take the lag away - throw to throw the servos is half a sec behind my movements, the HS-81's keep up.

Hopefully smoother flights and a few more charge cycles will result in longer flights too...

more to come, when i have time! so busy at the mo...

Comments?

Thanks for all who have helped so far....

Bugjam

Dr Kiwi
11-09-2007, 08:09 PM
I'm glad that the power system worked out to be more than adequate... I had no control over how the plane flew.... so I hope you get that sorted.

I'm impressed that, despite all the difficulties, you managed to keep it in the air... I would certainly have crashed it at the first untrimmed moment!

Cheers, Phil