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Old Dec 30, 2011, 08:21 PM
Registered User
Potage, MI
Joined Dec 2003
534 Posts
I certainly agree that test flying is the only way to evaluate results. I have a wall with nails for just about every size of APCE and APC Slowfly prop I'm likely to use (over 60). On a new airframe I'll go through prop testing to get the performance I like. My starting point will be Motocalc info or user data from RCgroups. I see Motocalc as most useful to inexperienced users to see what happens to thrust, speed, efficiency, etc, as prop diameter and pitch are changed.

Vince
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Old Dec 30, 2011, 10:16 PM
Registered User
Moore, Oklahoma
Joined Oct 2004
4,322 Posts
You can’t beat real world flight testing. That’s just a fact. IF you want to get above a certain L/D with the AR restrictions we limit ourselves to along with size you will need CFD or a type of finite analysis to determine where and how you can fix or improve your aerodynamics. Simple things can turn into a game changer for most aircraft. If you have access to these types of programs and the knowledge to analyze and know how to understand the data given, you will be capable of creating an aircraft that has great abilities.

Now in most cases for sport flying you would almost never care about the difference between a 6:1 L/D and a 12:1 L/D bird. Where the significant notice comes in is more specifically when you are trying to achieve the flight times that are most desired for sUAS or FPV. There is a lot more to setting up the aircraft for extended flight times and maximized efficiency than CFD. Knowing your aircrafts limits, abilities and optimized flight conditions such as specific speeds the aircraft will perform at its best L/D will go a long way in helping you determine power needed along with pitch speed of propellers and static thrust.

A great example of this is the Boomerang. It’s very high L/D and the knowledge of the aircraft intimately allows us to fly the 5lb aircraft with a 320W motor pulling 3.5-5A for a cruise speed of 85kph dependent on weather conditions.

Both Gene and Jimmy are very correct and as mentioned, a little science behind it will go a long way if applied properly. They have both designed and sold successful aircraft and continue to produce solid viable aircraft that have a place in the sUAS world. Gene’s birds can take one heck of a beating fly in crap weather and are very stable and Jimmy’s birds fly like they are on rails with no bad habits, his are also very durable aircraft. Both are very different aircraft but achieve the same goal. At this point most of us that design and manufacture aircraft for sUAS or FPV will not allow our aircraft to reach the public if it does not perform as we expect. I think I can speak for all three of our companies in saying never will we release an aircraft that would result in negative feedback due to flight abilities or bad habits. The Froo is no exception. It preforms as described and in many cases surprises the heck out of us when hit by adverse conditions.

The numbers and real world flight data does not lie. A combination of the two can become very powerful.

Happy Holidays and I hope all has a very Happy and successful New Year!

Chris
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Old Dec 31, 2011, 03:12 PM
DragonLINK UHF only!!!!
Joined Feb 2011
1,217 Posts
dalbert02

Thanks for those calculations:-)
It shows that the Scorpion Motor (3014/ 800kv-1300kv) I have is not that great for increased flight times.
(it shows an average of ~30min.)

What are you set ups for inbetween normal flying (fast, slow, cruising....etc.)

I think those Scorpion Motors are too small.... there is no way I'm putting a 6x4 prop on this F'roo and its already hard to launch with our extra weight on.....and you are right, my whole entire flight time wil not be at 80-90% throttle.

p.s.
those CFD calculations are nice numbers, "BUT" severly goes down (Suffers) when we put our FPV gear on this plane.
(MOST PEOPLE WHO BUY THIS PLANE DON'T REALIZE IT UNTIL THEY PUT THERE FPV GEAR ON)

There are antennas'(dragonLink, ImmerionRC, ThomasScherr LRS UHF antennas)
, PanTilt servos carrying a Squared camera's CCD,
and Squared GoPRO,
more antenna's sticking out of this F'roo when fully loaded.

FPV is my main purpose, not UAV....


.....but overall, I like this plane for easy care free FPV'ing around :-)







On 4S2P 2500mAh packs, the 3014-830kv shows 37 min @80% throttle w/8x6 @36mph
On 3S2P 2500mAh packs, the 3014-830kv shows 38 min @90% throttle w/9x6 @33mph

On 4S2P 2500mAh packs, the 3014-1040kv shows 25min @90% throttle w/ 6x4 @31mph
On 3S2P 2500mAh packs, the 3014-1040kv shows 33min @90% throttle w/ 9x5 @33mph

On 4s2P 2500mAh packs, the 3014-1220kv shows 26min @ 80%throttle w/ 6x4 @31mph
On 3S2P 2500mAh packs, the 3014-1220kv shows 37min @ 90%throttle w/7x4.5@32mph

Remember, you probably won't have your throttle at 80% or 90% the entire time so your flight time may be even longer. The data supports the theory that spinning a larger prop slowly is more efficient that spinning a smaller prop faster. I would think the 6x4 setup would not be hand launchable. As a wise old colonel used to tell me, one carefully controlled experiment is often times worth more than a thousand expert opinions.

-dave
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Old Jan 14, 2012, 05:48 PM
vau
Registered User
UK
Joined Jan 2007
252 Posts
Putting the final touches on now - it's pretty much 2kg fully loaded which is a little heavier than I had wanted. That's with the 485g 8000mah battery.

I'm hoping the EFlite power 10 is up to the job but will find out any day now.
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Old Jan 14, 2012, 05:56 PM
DragonLINK UHF only!!!!
Joined Feb 2011
1,217 Posts
Vau.....

wholly crap that is heavy. Let me know if it can be hand launched?

wow!
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Old Jan 14, 2012, 06:53 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Let us know how it flies when you get her going. Might want to have someone hand launch it for you on the first flight so you can trim it out. Bungee is easy to build if you want to make one.

Jimmy
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Old Jan 17, 2012, 09:28 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Some pix of the removable skid rail. Hope to the mold done in a week or two. Will post more pix then.

Jimmy
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Old Jan 19, 2012, 09:45 AM
Registered User
Joined Jul 2008
35 Posts
Motocalc
Twinstar 2
measured climb rate 300m/min Motocalc :240 m/min
measured speed : 75-78km/h Motocalc : 72 km/h
Flight time : 18min Motocalc : 35min
measured Ampere: 23A Motocalc : 25A
Even after ajusting numbers to match my installation.
The flight time is half that the
rest is a little under but close.
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Old Jan 19, 2012, 10:18 AM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Thanks for sharing that michelcote. That's precisely why I don't put a whole lot of faith into the numbers that we get from the software. It can be a good starting point but that's about it.

Jimmy
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Old Jan 22, 2012, 04:43 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
I recently found some information concerning one of the individuals that had a problem launching his Froo that I'd like to expound upon. The Froo was loaded up very heavily and launched by the pilot (no assistance from others) on its first flight (as yet untrimmed) on a dead calm day. Having flown many flying wings I always seek assistance on the first flight so I can get it trimmed and then will hand launch myself without any assistance after I know the plane is trimmed.

There were a couple of issues here:

1. Heavily loaded planes, no matter what the planform, will require either the pilot run and launch it to get some airspeed under it or that it have a headwind to launch it into. A flat footed launch just won't cut it. It's also imperative on any flying wing that you don't impart yaw when you throw it or it will drop a wing.

2. An untrimmed airplane on a first flight is unpredictable. I HIGHLY recommend that you have someone else launch it the first time so you can be on the sticks and start trimming as soon as the plane is in the air.

3. If you're going to launch it by yourself on a dead calm day, you either need to sprint with it to get airspeed or use a bungee. Starting at zero airspeed and then throwing the plane won't get you enough airspeed to launch unless you have some experience doing so and have a good arm. I always throttle up before I launch to get more acceleration on release and have never gotten bitten by the prop. (This includes the Osprey and myriad of Froos I've flown as well as others Zagis etc.)

Jimmy
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Old Jan 29, 2012, 11:25 PM
Gaftopher
Gary Mortimer's Avatar
Nottingham Road South Africa/Bedford UK
Joined Feb 2007
3,815 Posts
I find a slope is always a good tool for instant altitude launches. Even a tiny one on the edge of flatish fields helps.

As a wise airframe designer once said, the only thing to add is lightness.
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Old Jan 30, 2012, 11:41 AM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Good point, Gary. The video below was the first flight of my Foamaroo fully loaded with my GoPro in the nose and a 5000 mAH battery. I launched it down a hill (as yet untrimmed) and let it gain speed before I pulled up and accelerated away. Worked great! Subsequent flights were done with flat footed launches on flat ground.

100% correct on adding lightness too!

Jimmy

First GoPro Video Shot From Foamaroo (5 min 48 sec)
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Old Jan 30, 2012, 03:12 PM
vau
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UK
Joined Jan 2007
252 Posts
Quote:
Originally Posted by jtprouty View Post
I launched it down a hill (as yet untrimmed) and let it gain speed before I pulled up and accelerated away. Worked great!
Heh just as well - that river looked pretty murky

When I have time, hopefully this weekend, I'll be going for the maiden flight from the top of a gentle slope. I'm pretty lanky and can probably hand launch from 7ft plus but an extra couple of feet extra altitude from a slope just increases the allowable error margin. The flip side is further to fall...

I'll make a point to post the results of the maiden here
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Old Feb 19, 2012, 07:38 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Shot a video on how to hand launch the Froo today. Three flights were done at 1280 grams, 1870 grams, and 2240 grams. All launches were done from a standstill due to me having a bad knee. Motor: Alpha 480 1020 kV 275 watt and APC 10 x 10 prop. Weather was clear and cool with 10 mph wind from the south.

Jimmy

Foamaroo Launch Technique (4 min 16 sec)
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Old Feb 26, 2012, 05:52 PM
Inherent Tinkerer
Wichita, Kansas, USA
Joined Jul 2003
1,428 Posts
Some flat spins with a FRoo.....

Flat Spins with a Foamaroo (1 min 50 sec)


Jimmy
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