SFM Exec Jet - HELP
 

Hi All,

Well - I take my Exec Jet down to the park the other week, merrily perpare it for flight using a cricket pitch as a runway (approx 20m long). I set the aircraft into wind, and take a look at a large patch of trees at the end of the field and remember thinking "mmm, i am sure i can get it airborne on the cricjet pitch and out-climb those trees!".

Anyhow, it stayed on the ground well past the length of the cricket pitch, through some wet long grass and i managed to lift her into the air - and straight into a large palm tree shattering it into a million pieces!

So - she is back together (thanks goes to this company [link=http://www.rmax.com.au]RMAX[/link] who gave me a 750x750x200 dense white foam for FREE!).

My question is: HOW MUCH RUNWAY DO I NEED TO GET THIS THING AIRBORNE?

Specs are:
4000 kv outrunner max 23A
3S 2200 MaH 15C
ESC 30A

I would like to avoid the nasty happenings of the other week if possible!

THANKYOU!

RE: SFM Exec Jet - HELP
 

"...HOW MUCH RUNWAY DO I NEED TO GET THIS THING AIRBORNE?..."

More than 20 m, that's for sure :D

Seriously though, a lot depends on how deep is the grass, what size are the wheels and the AUW of the plane. It looks like you have a little less than 300W going in, perhaps 250~ish available to push. This is probably plenty for a paved runway.

If it were mine I'd do one of three things.

First, I'd dump the wheels and try SOG (slide on grass) take-offs. If the wheels are too small to roll freely through grass, they will be damaged when you land in grass.

If SOG's don't work then resort to either hand launch or bungee.

RE: SFM Exec Jet - HELP
 

Thanks Larry,

I also though hand launch would be the go - can you suggest any tutorials etc on good hand launch practices - never done it!

RE: SFM Exec Jet - HELP
 

tasesq,

I have made literally hundreds of hand launches, 99.99% of which were successful. All of my HL's are done while standing still. I guess I can not run and throw at the same time.

Regardless, I think the important parts of a HL, especially with an EDF, are:

Make sure the plane is balanced per the instructions, including lateral balance
Full throttle, of course
Aim the HL into the wind, of course
Try to throw level or just slightly nose down, not up. Launching with a nose up attitude is inviting a stall.
Once launched, resist the urge to use the elevator. It will "get on step" within a few seconds but during this transition your plane will be just above stall. Let the plane accelerate before using the elevator. If balanced properly, the plane will climb on its own as the wing's lift is a function of velocity. Within 5~7 seconds, the plane will be flying as fast as it is able.

I forgot to add the most important item.

Use as much "arm" as you can muster when launching. This is not the time for a limp-wristed wimper of a push