HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 05, 2013, 10:01 AM
This says nothing.
benjamin presten's Avatar
United States, CA, Sonoma
Joined Jun 2012
140 Posts
Help!
scratchbuilt help needed.

I designed and build this airplane, it does fly but it wobbles around all the time and I don't know what to do to fix it. Please help. Here is a video.

chopping board flyby (0 min 36 sec)
benjamin presten is offline Find More Posts by benjamin presten
RCG Plus Member
Last edited by benjamin presten; Oct 05, 2013 at 10:09 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 05, 2013, 10:29 AM
serial scratchbuilder
Granted's Avatar
Canada, BC, Mission
Joined Sep 2012
1,298 Posts
Nice kite! Does it fly the same on a still day?
Granted is offline Find More Posts by Granted
Last edited by Granted; Oct 05, 2013 at 10:59 AM.
Reply With Quote
Old Oct 07, 2013, 06:34 PM
Registered User
MaydayMayday's Avatar
United States, CA, Fremont
Joined Jul 2011
734 Posts
Not sure if this is a real comment, or a troll in search of gold.

If it's a real question:
- Part of your problem is you built the most basic design possible, so you're going to get the most basic results. It looks like you're flying in too high of wind.
- it's also possible your CG is WAYYY too far forward.
MaydayMayday is offline Find More Posts by MaydayMayday
Reply With Quote
Old Oct 07, 2013, 06:57 PM
Registered User
Chatenever's Avatar
USA, CA, Oxnard
Joined Mar 2006
797 Posts
I think the CG is too far BACK. Try moving the battery forward.
Chatenever is offline Find More Posts by Chatenever
Reply With Quote
Old Oct 07, 2013, 10:59 PM
Registered User
MaydayMayday's Avatar
United States, CA, Fremont
Joined Jul 2011
734 Posts
Actually I think I was on crack, I agree the weight looks farther back, the battery kinda looks like it's right in front of the prop
MaydayMayday is offline Find More Posts by MaydayMayday
Reply With Quote
Old Oct 10, 2013, 03:27 AM
Will work for foam
wingnutt's Avatar
United States, WI, Muskego
Joined Apr 2005
1,502 Posts
IMHO it's the tip fins. Remove those and move them inboard like a Superfly (http://www.superflyrc.com/). A delta wings stability in high AOA flight is a blend of the vortex lift on the forward section of the airfoil and the tip wash. I believe the tip fins are disrupting or totally blocking the tip wash.
wingnutt is offline Find More Posts by wingnutt
Reply With Quote
Old Oct 12, 2013, 05:05 AM
Will work for foam
wingnutt's Avatar
United States, WI, Muskego
Joined Apr 2005
1,502 Posts
Just curious if there was any progress on fixing the wing-rock?
wingnutt is offline Find More Posts by wingnutt
Reply With Quote
Old Oct 13, 2013, 02:07 PM
Gone Fly'n
planecrazy1969's Avatar
USA, NV, Las Vegas
Joined Jan 2007
287 Posts
I have seen this before in one of my profile jets...when I attempt to fly at slow speeds with a high AOA my jet starts wobbling just like this...I think it is due to a flat-plate wing with no step or airfoil as well as torque roll and the lack of air flowing over the top of the wing to stabilize flight...just a guess
planecrazy1969 is offline Find More Posts by planecrazy1969
Reply With Quote
Old Oct 21, 2013, 12:53 AM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,391 Posts
I think it's just very high AOA. I've had delta wings with huge tip fins that flies very well. Reduce the up elevator. CG may or may not be too far back or forward but the AOA is too high. If possible, can you post a photo indicating where the CG is currently.

The funny thing about high AOA is that it is the result of either CG too far back of CG too far forward. You'll only really know which by the "feel" on the sticks. Too far back (tail heavy) will tilt the plane up which results in high AOA. Too far forward (nose heavy) will cause the plane to tilt down into a dive - which pilots counter by adding lots of up elevator trim which causes the plane to have high AOA.
slebetman is offline Find More Posts by slebetman
Reply With Quote
Old Oct 21, 2013, 01:10 AM
Registered User
slebetman's Avatar
Malaysia, Selangor, Kajang
Joined Jun 2009
1,391 Posts
Quote:
Originally Posted by planecrazy1969 View Post
I have seen this before in one of my profile jets...when I attempt to fly at slow speeds with a high AOA my jet starts wobbling just like this...I think it is due to a flat-plate wing with no step or airfoil as well as torque roll and the lack of air flowing over the top of the wing to stabilize flight...just a guess
The wobble is actually small tip stalls. At extreme AOA the drag will be significant enough to cause the plane to fly close to its stall speed. The narrow tips of deltas means that the tips are more likely to stall before the rest of the wing. But deltas, due to their very docile stalling nature, don't stall abruptly like regular wings. Instead they dip a bit and almost immediately recover. When deltas tip stall you'll see it wobble, when deltas stall you'll see it porpoise.

If you practice enough you can learn to control the wobble by applying correctly timed aileron inputs. I do this all the time if I need to glide down slowly at a steep angle to land in small spaces. The 3D guys call it the elevator maneuver and the flying wing guys call it the parachute maneuver.
slebetman is offline Find More Posts by slebetman
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Help I need help!!!!!!!! Ghjghj96 Power Systems 15 Jun 27, 2013 06:47 PM
Discussion need help with choosing wich esc to match a simon k rc timer pls help quadcopterguy Multirotor Electronics 2 Jun 09, 2013 09:11 PM
Help! HELP!!! Tarot FY680 Build - Need help with parts! Yo_Mang Multirotor Talk 5 Apr 13, 2013 08:40 PM
Discussion Help Us Pick A Great Raffle Prize For A Fun Fly Please. Need Your Help To Decide Murocflyer Electric Flight Events 16 Mar 01, 2013 11:29 PM