Author Topic: 2nd ECL Flight (Read 1102 times)

John Hammonds · « **on:** March 15, 2009, 05:15:16 PM »

Hi All,
After my rather underpowered attempt at the end of last year with my Flightstreak (Post lost in the server crash). I finally got around to the 2nd instalment, weeks of wet, snowy or windy weather along with a string of honey do's meant this was my 1st free day since new year. Digesting replies to my last post suggesting not enough volts and or insufficient rpm/v, and or excessive line length. (If I could get it wrong I did).

We returned to the field still with A123's but my local shop had the AXI 2820/8 on offer, and at 1500 rpm/v this seemed like an ideal solution to my power issue. I broke all my own rules of only changing one thing at a time and also reduced the line length down to 52'. Also courtesy of Ebay I'm now the proud owner of 2* CC45 and a CC35, total cost was less than 1 new CC45, all now updated to the latest firmware and I'm a happy camper.

I know my 3s1p A123 set up is never going to give me 6 minutes with this motor but if it will give me 3-4 minutes of aerobatics against 6 minutes of mostly straight and level I'll be happy.

So how did it go?

Well B!"£$Y brilliant is the answer, at least for the minute and a half before I completed my 2nd lap inverted had brain fade and stuffed it into the dirt. Took the motor and mounting ring clean off, likewise the canopy, and I've discovered since I got home split the fuselage just in front of the leading edge. Not a pretty site but a fairly easy repair. It still seems to lose line tension at the top of a loop so I think I'll try a bit of engine offset and/or increase the RPM a bit next time. The CC software is simply amazing, I don't think I could ever go back to a programming card again.

I've bench run the set up since getting home and I'm pleased to say that the current protection circuitry did it's job and no damage to the power train so I'll be back in the air as soon as I can.

TTFN
John.

Leester · « **Reply #1 on:** March 15, 2009, 06:16:14 PM »

Hey John, Congratulations on a great minute and a half. Show us what it looks like when you get it repaired, BEFORE your next flight

John Hammonds · « **Reply #2 on:** March 17, 2009, 05:42:51 PM »

Funny..

...

It's all back together apart from leaving the glue to cure and re covering the nose section, I did have the motor mount epoxied to the end of the bearers peggs on 1/8" dowels (Which sheared clean off). It's now got 3/4" No4 wood screws replacing the dowels again epoxied, so next time I'm sure I'll write off the front end completely before it breaks loose. I've also added a conventional U/C as so far I've had to rely on a hand launch as the mono wheel set up does not seem up to the task for unattended take off's, at least until the circle gets it's 1st cut of the year. So.. it's beginning to become a real porker weight wise. Still more than adequate for my inane attempts though. It's also now definitely beginning to become a 50/50 finish (Looks great at 50ft doing 50 mph).

On the last flight it still seemed a bit twitchy in level flight but at the same time but not overly responsive when actually trying to change direction. The CG is 1 1/4" back from the leading edge. Is it just me going through a learning curve or should I possibly get a handle with narrower line spacing? I currently have an old DC handle spaced at 4". The pushrod is already in the hole furthest from the elevator.

Thanks in advance

TTFN
John.

Alan Hahn · « **Reply #3 on:** March 18, 2009, 08:09:19 AM »

I'd move the CG forward. I'm not sure why the Flitestreak is such a sensitive plane with respect to CG, but it is. If you search on the ARF Flitestreak, there were several posts on how the cg given in the manual was wrong. I think that was even true for the Top Flite Kit.
To counteract the extra stability, I would increase the elevator throw.

John Hammonds · « **Reply #4 on:** March 18, 2009, 07:15:59 PM »

Hi Alan,
Thanks, The CG reference was taken prior to the crash so I'll see where it sits with the addition of the conventional U/C once it's all back together.

I've not really had it in the air long enough to have any real opinions on my CC45 parameters but any thought on a good starting point for the prop and rpm? I'm running it in CL governor mode. Currently I have an APC E 10*7 with head speed 1 set to 8000 (about 20 seconds on the timer after the walk out to the handle) and head speed 2 set at 9000 (For the rest of the flight - if I ever get that far).

Head speed 3 is also set to 9000. I just picked these figures out of the air. It's a 1500rpm/v (AXI 2820/8) on a 3s1p A123. I remember somewhere hearing "target rpm" should be no load rpm at pack voltage * 0.7. Does that sound about right? That would put me up around 10,000 rpm. Would I be better decreasing the pitch and /or diameter and running the higher rpm? It's a portly beast weighing in at a tad over 32oz. (Pre crash configuration).

Thanks in advance

TTFN
John.

Alan Hahn · « **Reply #5 on:** March 19, 2009, 08:05:23 AM »

John,
I am running that prop (APC 10-7) on my SuperClown E-ARF (at 28 oz) and fly at ~8400 rpm. My lapspeeds are ~4.8 seconds.

The SuperClown has a very thin airfoil and probably needs that low laptime. The FliteStreak airfoil is a lot thicker and can probably fly a bit slower and still feel pretty good.

So for test flying I think you are ok. I would just take it easy at first, and try to dial in the speed that makes you feel comfortable. Usually with first flights I put the total time at ~2 minutes so that I can get a couple of tries per battery charge to dial in the speed. You might bring an APC10-5 prop to the field just in case the 10-7 is ballistic at 9000 rpm.If it does, then just put on the lower pitch 10-5 prop and that by itself will slow you down (aren't governors wonderful?!).

John Hammonds · « **Reply #6 on:** April 05, 2009, 06:18:07 PM »

ok, Several more flights and nothing more serious that a broken prop after a hard nose over on landing, I went back to the mono wheel U/C, the conventional version did little to move the CG but added to much weight to an already heavy beast. The CG seems about right now according to other club members but it's still twitchy to me so I'm going to reduced the line spacing for the next outing. Line tension is adequate and I'm now happily flying loops, lazy 8's, inverted , horizontal 8's and even a reverse wing-over (Although I doubt any of the spectators recognised it as such).

Surprisingly (To me) I'm yet to hit the low voltage cut off. A 5:30 flight (Including 30 sec handle walk) and it's still running like a train at the end. I know that's all down to the governor so I'll see how far I can push it. I've not timed it over any distance yet so still don't know my lap times. It's currently (Until I broke it) running an APC 10*5 E with RPM1=9000, RPM2/3=9500 and I'm putting 1855 ma back into the pack. I have the low voltage cut off set at 6v (So 2v per cell). Is this ok with A123's or should I raise it a bit? How much can I safely take out of the pack bearing in mind I'm purely a fun flyer at the moment so don't want to shorten the pack life to any great degree. In short, life is good, I actually have a setting which works, 99% because of the advice found on these boards. The other 1% might be me or could just be pure luck.....

I do feel a bit geeky though dragging the laptop out at the field to adjust the settings on the Phoenix.

Thanks again all.

TTFN
John.

Dean Pappas · « **Reply #7 on:** April 05, 2009, 07:24:40 PM »

Hello John,
Glad to hear that things are progressing nicely for you.
Please allow me to suggest that you do not push the battery capacity: if you hit the LV cutoff, you have already shortened the cycle life and number of flights you will get from those batteries. They cost too much to abuse them so.
It is best to keep your per-flight consumption under 75% of capacity.

How about that Jensen Button, eh?

best regards, Dean P.

Alan Hahn · « **Reply #8 on:** April 05, 2009, 07:50:09 PM »

John,
I'm not an A123 expert, but those who are claim you can abuse them much more than you can lipo's. That's one of their claims to fame--that you can use more of the stated pack capacity, unlike lipos where you should leave at least 20% in the pack.

You might check some of the A123 posts in the RC Groups. Here is a link to a guy who uses them quite a bit. He gives a lot of links to info in his poat.

http://www.rcgroups.com/forums/showpost.php?p=6769001&postcount=2

John Hammonds · « **Reply #9 on:** April 06, 2009, 05:34:19 PM »

Yep, Jenson Button seems to have struck gold with his new ride. F1 looks to be a lot more entertaining this year, hopefully they finally have some rules which will stop it being a procession on track and won in the pits. I'm more of a motorcycle race fan than cars (More overtaking in a single lap than an entire race of F1 for the past few seasons) and have to say Ben Spies is really amazing in WSB, sitting 2nd to Nitro Nori in his rookie season. The last time I got my Bandit leaned over that far I had already fell off it.

There's a frightening amount of info to digest in that link Alan but I'll work my way through it.

Searching in A123's on this forum turns up far more than I had expected. I notice Igor seems to use his cells to the max without to much apparent damage and on one of the model boat forums I found it seems common practice to discharge them up to and even beyond 2000mah while still getting a season's racing, so probably no more expensive than buying fuel, glow plugs etc. It makes me wonder just how much of an advantage Lipo's really are, at least for a fun flyer like me who hopes enter a few comps in the future without completely embarrassing himself. I know A123's are heavier and run at a lower voltage. But given they can deliver a far higher %age of their capacity without damage, plus the robustness of the design, comparative ease of making custom pack configurations, standard size, impressive discharge and charge rates is the difference quite as large as we are led to believe? I know Lipos are out there now with similar charge/discharge parameters but they seem to be nearly as heavy and similar as far as size is concerned to A123's. I guess it's all down to getting that last 5% and if like most here you are striving for the last 5% then it's a no brainer but for me A123's are a godsend, I'm sure by now I would be at least one Lipo pack worse off after my previous crash.

TTFN
John.

Dean Pappas · « **Reply #10 on:** April 07, 2009, 06:39:16 PM »

Yeah, Haga must be getting nervous right about now, and Spies is making us Yanks proud. Doha was a romp!

The A123s are perfectly happy, even thrive, when run to 90% of capacity each and every flight.
The energy density after correction for the actual percentage of capacity that may be safely used (75% versus 90%) gives only a 20% disadvantage to the A123 for energy per ounce.
If you find that for the kind of flying you do, that you only use 60 or 65% of your LiPo capacity, then try the A123s, but expect to re-prop (or up the Kv) for the lower voltage, or accept less headroom for the governor to do its job.

If you build very lightly, this will be perfectly competitive. For Sport, even the enthusiastic variety, they are just dandy.

best regards,
Dean P.

Author Topic: 2nd ECL Flight (Read 1102 times)

John Hammonds

2nd ECL Flight

Leester

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John Hammonds

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Alan Hahn

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John Hammonds

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Alan Hahn

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John Hammonds

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Dean Pappas

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Alan Hahn

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John Hammonds

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