SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Apr 30, 2012, 05:02 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
Mods

Removed the thrust offset.

Cleaned up the rudder hinge.

Rebuilt the elevator - rounded LE for center line hinge

Working on aluminum can motor cowl

Aileron will take a while

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Sign up now
to remove ads between posts
Old May 01, 2012, 05:11 PM
Registered User
UnDetekted's Avatar
NM Desert
Joined May 2010
16 Posts
Quote:
Originally Posted by Tom Harper View Post
1) Oscillation - It is critically damped in a right turn but oscillates in a left turn. Well, duh! All of that left thrust increases system gain to the left and critically damps to the right.

2) Power - So, why the power increase? Speed, weight and altitude are constant so lift must be constant. In a left turn the single left side aileron decreases lift on that wing panel. Two things must happen in response: the autopilot must increase angle of attack to maintain lift and it must correct for adverse yaw. That results in a significant drag increase and a compensating increase in power. More power = more system gain resulting in oscillation.

3) Cure - Remove the left thrust - Add a right side aileron - Increase rudder area.
Tom
Tom,

Recall that our best flights were our first few flights with no left thrust (actually, I think there was some right thrust?). As such, I'd say your conclusions are valid. However, I doubt we need more rudder area as it has not showed any lack of effectiveness.

Powell
UnDetekted is offline Find More Posts by UnDetekted
Reply With Quote
Old May 01, 2012, 05:37 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
The Left Turn Problem

Powell,

I watched the video this morning and had the same thought. It seemed to handle the left turns fine.

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Old May 01, 2012, 06:23 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
Hinges

I've been using tape for so long that I had to search for hinges. I salvaged these from a box of stuff.

Don't like to glop up hinges with CA or epoxy, also have had binding problems with 3 point hinges. So, I pinned them with toothpicks - no glop. That gives them some float so they are self aligning.

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Old Oct 12, 2012, 06:16 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
Patina of maturity

Asym now carries the patina of experience. It's had a couple bad crashes. Nothing design related - equipment and crew.

I added the right aileron and have spent a lot of time on the electronics. I believe everything is cleaned up. We shall see this weekend.

One of the project criteria was ease of field assembly. The Asym has fallen short in that regard. It takes two people 15 or twenty minytes to assemble this thing. That takes time and can lead to errors.

So, I did some measurements and found that the model will travel on the package cover of the Land Rover. That, and some autopilot packaging changes, removes over half of the assembly time.

Should be back in the air by Sunday.

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Old Oct 14, 2012, 12:58 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
A bit windy

Nice day but a bit of a gusting wind. Hand launch was uneventful.

This was the first flight after the addition of the right aileron. CG and lateral balance look good. Needs a calmer day to get the trim adjusted.

Still having Autopilot problems, will work on them this week.

Brought it home in one piece, so it was a successful day!

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Old Oct 14, 2012, 10:11 PM
Registered User
HELModels's Avatar
Joined Aug 2003
2,654 Posts
It sure looks unique in flight, like it was built with a purpose in mind.

HELModels is online now Find More Posts by HELModels
Reply With Quote
Old Oct 15, 2012, 04:24 AM
Registered User
Joined Oct 2004
2,908 Posts
Looks very sleek for sure. But those low set tail and wing seem made to catch in any possible clump of grass or bush even in the smoothest landing. I understand that it will spoil the aerodynamics a bit, but wouldn't it be better off with a few wire skids under the nose and wings?
Brandano is offline Find More Posts by Brandano
Reply With Quote
Old Oct 15, 2012, 09:00 AM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,664 Posts
Thanks guys,

It has 1/4" square spruce longerons on the bottom of the fuselage and pod. So far they have been sufficient.

I am concerned about field operations. This thing is big. We have been using a county road for landing - narrow with lots of sand (photo). Be interesting to see how it does.

Tom
Tom Harper is offline Find More Posts by Tom Harper
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Asymmetrical Flybar Travel on the Big Lama - Related to Death Dives? rampa202 Coaxial Helicopters 52 Nov 26, 2011 10:58 PM
Discussion AP Full Arducopter UAV Gasser Build. ben1101 Aerial Photography 6 Oct 31, 2011 06:56 AM
Build Log AP UAV like plane , using 10g BL Prime_8 Foamies (Scratchbuilt) 9 Jun 10, 2011 01:51 AM
Small UAV for AP? New project! icebear Aerial Photography 47 Jun 12, 2005 09:51 PM
Asymmetrical AP-plane out of depron century_series Foamies (Kits) 31 Sep 09, 2004 03:49 AM