KFm4 42'' Scratchbuilt FPV WIng - RC Groups
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Oct 20, 2011, 05:02 PM
Dixie Normious
Eastcoast78's Avatar

KFm4 42'' Scratchbuilt FPV WIng

Well i decided to get into FPV seeing its coming on Fall here now, the air is getting cool and before you know it, the days well be shorter.

First up i wanted something that would be easy to fly! Carry anywhere between 4200mah or maybe even up too 5000mah, I am shooting for a AUW anywhere between 1000-1500g.

I considered Buying a Ritewing or something like it, But i like building.
So i decided to build one from 1/2 Owens Cornering Pink Foam.
I got 2 4'x8' sheets for $14 from my local Home depot!

For the FPV i have the 5.8g 200mw FPV Wireless AV Tx & Rx Set
I well not be using goggles at first. I have plan to get a LCD monitor and install it in one of those Big Black Rubber maid Action packers.
Could easily make/install it like a Speaker and surround with Black foam, like the inside of a TX case!!

Or Wal Mart has aluminum cases that can easily be modified to fit a Nice LCD screen.

For the camera i well be wiring a 2.5mm 4 pole jack plug it directly feeding the video through my GoPro!

Thanks for RC Flight Test for this great video.
How To Use a GoPro for FPV (7 min 12 sec)

In trying to find a decent Powerplant that was semi efficient!! I needed something that could swing a 8 or 9 '' Prop.
So i decided to give this one a shot!

If ordering this BL get this. be sure to pick this up as well this BL does not come with any mounting hardware!
I also got 2 of these servos to test.

I have a HK 40-50A esc now...Which should hold up. Having the ESC on the wing well Provide Lots of ventilation...

Model: NTM Prop Drive 35-36A 1400
Kv: 1400rpm/v
Turns: 7
Max current: 55A
Max Power: 550W
Shaft: 4mm
Weight: 117g
ESC: 60A
Cell count: 3s~4s Lipoly
Front Mounting Hole Distance: 25mm or 19mm
Connection: 3.5mm Bullet-connector
Suggested Prop: 8x4 ~ 11x5.5

Prop Tests:
8x4 - 14.8v - 621W - 42A
8x4 - 11.1v - 277W - 25A
9x6 - 11.1v - 432W - 39A

10x5 - 11.1v -510W - 46A
11x5.5 - 11.1v - 543w - 49A

FPV is all new to me and i well not have OSD for now. Ill just keep it in view
But thats on the list as well

Thanks to schraut5 for these plans, his original plans are 30'' and had great flying results.
Heres his Thread on it

Heres a few pictures of the build.
Last edited by Eastcoast78; Oct 22, 2011 at 06:45 PM.
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Oct 20, 2011, 06:00 PM
Dixie Normious
Eastcoast78's Avatar
It is pretty much ready for a Maiden, Just cut the bays for the battery's and a few small things.
Also added SFG's out for Coro board
AUW is 1140g
Oct 21, 2011, 10:30 PM
Zen in the art of foam
djacob7's Avatar
I think you meant "I am shooting for a AUW anywhere between 1000g-1500g"
Oct 22, 2011, 06:45 PM
Dixie Normious
Eastcoast78's Avatar
lol yea Grams...

Wow over 100views and your the first post...Maiden is tomorrow, but i may let this thread die and post the results in my Blog and on the scratch builder page's...

Oct 23, 2011, 08:57 AM
CrashMeUp's Avatar
ah i know what you mean
most of my build threads are like that
it seems that people like to read them tho so you should keep posting
as long as theres nothing to buy or to reply to theres not so many posts ;-)
Oct 23, 2011, 05:27 PM
Dixie Normious
Eastcoast78's Avatar
Yea i hear yea!!

Well the Maiden was successful, well after a few trial and error launch's.
Its weird. with the 2 2200's up front, i was thinking it was still tail heavy!! When i tossed it, it nosed in big time...
I took 1 battery out and it was way tail heavy!! I put the Battery back in and trimmed a lot of up trim in the travel adj and sub trim and it flys pretty darn good...But with all that it still needed almost full up trim in the main menu!!
So i wonder if i should adjust the motor or work on the CG?

Video is Processing
Oct 23, 2011, 07:25 PM
CrashMeUp's Avatar
you always need a bit of reflex on wings (aka a bit of up elevator) although full trim might be much, it depends on the radio/servos, some don't trim very hard.

On all my wings, I always calculate the cg, put it right where it should be, toss it and crash :-) (or, well, you know, "more or less controlled landing")
Then I change the CG and it flies half decently
Then i refine it a couple more times until it flies really good.

Its a tricky thing to get right IMO
Oct 23, 2011, 08:38 PM
Dixie Normious
Eastcoast78's Avatar
That's what i ended up doing after the 2 botched launches. found it wanted to bank to the right, so i sub trimmed some and that fixed that. then needed about 25% up trim.

Im going to replace the control rods with some normal steel rods,with clevis's the CF ones i made aren't the greatest, the rod part with clevis bent a few times.

When you change the cg, usually what way you go? Aft?
Oct 23, 2011, 11:00 PM
Dixie Normious
Eastcoast78's Avatar
Maiden today was a success!! KFm4 Rocks...Still working on the CoG
I need to do some research on finding the right CG. I used the CG calculator, but its off...
saying it was 10.5'' form the nose...but was way to nose heavy.

Got around a 13min flight on a 2200mah...Once i get my Parallel hardness ill be able to use the other Batt i have there for Weight.

But all in all was a good flight!!
FPV Wing Maiden (6 min 19 sec)

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