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Old Feb 15, 2013, 05:39 PM
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Dave .
Excellent work and looking good .
As Malcolm suggests a hex head machine bolt is a better option for the rotor bolt , and less likely to bend following a rotor ground strike, which can happen ....no....will happen lol.
Your latest delta plate photos do look very different leaving no doubt about the material spec. I am impressed with the way all you guys are interpreting my build blog and how constructive the interaction is between the thread contributors is .It's all good stuff and I am sure some very flyable models will result .

Tom.

PS Don't forget the thread lock !
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Old Feb 16, 2013, 04:23 AM
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You betya, Tom!

Dave
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Old Feb 16, 2013, 02:53 PM
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Build Update 3

As before, photos speak for themselves. This design is ingenious, but I felt if there is a weak point it is perhaps the 3mm hole through the quarter inch spruce articulating arm. So I beefed this up (as per Tom's suggestion in the PDF) by fitting 0.8mm GF plates top and bottom. Also, I extended the side plates. This means that the articulating arm is fully sheathed in GF up to the whipping.

One final departure from spec: I drilled the rocker arm hole out to 3mm (rather than the 2mm specified). I will use 3mm OD/2mm ID brass tube as a sleeve to carry the 2mm steel rocker arm. This stiffens the assembly, provides (inner) end-stops for the ball joints and spreads the stresses transferred to the articulating arm via the rocker arm. Extra weight penalty is 3 grammes for the brass sleeve.

Despite the beefing up, this is still a lightweight, super-strong structure. The mast and assembled articulating arm weighs 26 grammes. The combined mast, arm and rotor head assembly is just 44 grammes - quite remarkable given that this is the guts of the machine. As I said, an ingenious design.

Dave
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Old Feb 16, 2013, 03:07 PM
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Ooops. Forgot this photo for some reason....
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Old Feb 16, 2013, 04:43 PM
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martinsville indiana
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2mm piano wire

at the end of my 2mm piano wire i put a little bend in it and then i press it into the wood for more grip
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Old Feb 16, 2013, 04:54 PM
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Do 2 crashes count as a maiden flight??

Well, tried to maiden my Baby today but it didn’t go too smoothly, disaster springs to mind!!
2 Attempted launches both ended in the model flying a knife edge circle to the left until contact with Terra Firma, tough old bird this one, only damage was a bent rotor head bolt. Pulling my hair out trying to figure out why and what thinking all about torque and the 3 degrees left tilt (which I defiantly got right) and my brain kept telling me that 3 degrees of left tilt is the wrong way for a clockwise spinning rotor head, PING, on the picture of Tom’s model he has the blades on the wrong way around!!!!
YEP, I build the blades for clockwise as opposed to anti-clockwise and man do I feel stupid. I also managed to strip my servo gears when ‘testing under load’ to make sure that it was not faulty but luckily I have another one which I am fitting right now.
So, test 2 tomorrow with a couple of degrees of right tilt and see how it goes.

On the up side, the rotors span up really nicely, after 7-10 paces you suddenly get a kind of turbo sound and she was really tugging upwards, nice. The motor also seemed to have loads of pull and actually, she looked quite good doing a knife edge race track pattern, might be a good party trick if she will do it when she flies properly and with no damage after 2 arrivals I might spend more time flying the Crane that repairing unlike my Depron AG.
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Old Feb 16, 2013, 06:34 PM
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Aw, thats a bummer, Paul. Still, on the upside, its still all in one piece. Thats got to be good. Like you say, its a tough old bird.

It must be an easy mistake to make, and if its any comfort I will learn from your experience and make the blades so they go anticlockwise.

I hope it goes better tomorrow. Fingers crossed.....




Thats a good idea, Channelmast - wish I'd thought of it!

Dave
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Old Feb 16, 2013, 06:44 PM
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Wow Paul !

This needs a little thought .Firstly I not sure if you have seen a photo with the blades fitted for clock wise rotation ,or was this a humorous comment? .
Don't worry we have all done the same thing once ! But I have not flown a CF with CW rotation . For sure the trim will be opposite ,but the motor zero side thrust ,is designed to reduce the amount of left trim needed ,so it is possible that more right rotor trim will be needed,.
Clearly during your exciting 3D exploit, application of full opposite roll control was not quite enough to contain the reverse trim set up so based on that experiance starting with three degrees right trim should allow sufficient control to to hold it on the stick ,but theory suggests it may need more .
Give it a try and see what you think , but if it wants to go left a little motor right thrust should help.
If you are successful tomorrow remember these machines will fly nice and slow ,just trim back the elevator and go easy on the power, leave the pylon racing until you have got used to it lol.

Regards

Tom.
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Old Feb 16, 2013, 06:53 PM
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Dave.

Good progress , thanks for the photos, it's good to see what you guys are up to , even if some get things back to front lol...sorry Paul could not resist !

Tom.
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Old Feb 17, 2013, 05:22 AM
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Quote:
Originally Posted by Tom Wright View Post
Wow Paul !

This needs a little thought .Firstly I not sure if you have seen a photo with the blades fitted for clock wise rotation ,or was this a humorous comment? .
Don't worry we have all done the same thing once ! But I have not flown a CF with CW rotation . For sure the trim will be opposite ,but the motor zero side thrust ,is designed to reduce the amount of left trim needed ,so it is possible that more right rotor trim will be needed,.
Clearly during your exciting 3D exploit, application of full opposite roll control was not quite enough to contain the reverse trim set up so based on that experiance starting with three degrees right trim should allow sufficient control to to hold it on the stick ,but theory suggests it may need more .
Give it a try and see what you think , but if it wants to go left a little motor right thrust should help.
If you are successful tomorrow remember these machines will fly nice and slow ,just trim back the elevator and go easy on the power, leave the pylon racing until you have got used to it lol.

Regards

Tom.
Yes Tom, joking about your blades being on backwards

I was thinking side trust and stuff last night and for sure, my rotor configuration is going to add to the Torque problem but I am going to try her this morning and see if I can get her going straight. Can’t be worse than yesterday and she survived that so it’s worth a try. I also decided last night that I will change to the ‘correct’ rotation (i.e. anti-clockwise) because with a motor creating torque to the left it makes far more sense to make the rotor head counter some of it out.

No wind and no rain at the moment so I’m off flying (got just an hour before I take Wifey to Mother in Laws, pity me ).

Paul B
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Old Feb 17, 2013, 08:14 AM
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Just look at the smile on my face.

2 Second update, just on my way out.

100% Success, 2 full flights (6 minutes each), 1 ROG take off (explain later) 1 hand launch. Model trimmed out hands off within 2 minutes, wide flat rudder turns, 45 degree banked aileron turns, WOT climb outs to high, engine off to Auto back down, GREAT FUN. First landing quite fast and shallow with a roll out, second landing pretty much 0 speed right in front of me, perfecttttttttt!!!

Detailed report later,

THANK YOU TOM.
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Old Feb 17, 2013, 11:13 AM
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Fantastic, Paul - great news!!

Its really great to hear its all come good in the end, very encouraging!!

Dave
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Old Feb 17, 2013, 02:58 PM
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8 Hours later and still smiling.

OK, arrived at the field to absolute zero wind which meant that even jogging across the whole 120 metres did not get the blades up to speed. Decided to wait for the wind and to do a taxi trial, got 1/3 of the way across the strip when she took off on her own!! The problem was that the blade speed was too slow causing a roll to the left but a dab of throttle and a hand full of right rudder got her back and looky here, she was climbing out nice and stable!! First successful launch and ROG at that!! She was out of trim needing half of the available right aileron trim and 5-6 clicks of down made her more comfortable in the mid-throttle range. Took maybe 2 minutes to have her trimmed out hands off and both left and right turns, banked or flat were fine with no tendency to drop the nose or to ‘dig into’ the turn. Full throttle saw her climbing fine and cutting the engine gave a nice slow 60 degree decent which was easily arrested with a bit of throttle. The first landing was a fixed wing type, keeping the forward speed up and coming in flat, slight bounce and then she settled down on the grass to roll out.
Flight 2 and I was being cocky so I went straight for a ROG but I opened the throttle too quickly causing a premature lift off again and the associated left roll. This time the rudder correction dropped her back onto the ground so I aborted. Followed the Guru (Tom)’s advice and hand launched (there was now a 1-2 MPH breeze), 10-15 steps, ¾ throttle had her climbing like a home-sick Angel and I then did 6 minutes of low slooooooow fly-pasts, steep climb out to auto back downs and generally had a ball.

The Crane Fly flies fine rotating clockwise (as far as I can tell) and I tried to provoke unwanted torque effects by abusing the throttle but once trimmed she stayed straight regardless. Tomorrow I will try to accurately measure how many degrees of right tilt that I have but it does not look to be much more than 3 degrees. Turns left and right were slightly different, she reacted better to left aileron than to right but strangely, right rudder seemed to be more effective than left however first flight nerves e.c.t. this is not definitive, I will monitor this.

All in all a fantastic morning and I am WELL happy with my Crane Fly, going to have some fun this summer and to be honest, I don’t think that I will bother to make a set of anti-clockwise blades as she flies fine as she is (but then again, to compare ).
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Old Feb 17, 2013, 03:18 PM
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Paul, it sounds like you had a superb day! You must have a truly unique Crane Fly (CW rotors). It'll confuse the hell out of anyone wanting to study the model close up though.....!

Dave
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Old Feb 17, 2013, 03:59 PM
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Anyone recommend a prop size for the E-power BL2220/07 motor suggested in Tom's PDF?

I'll test with a wattmeter, but I'd like to get as close as possible beforehand.

Dave
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