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Old May 27, 2012, 10:43 PM
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Tumbler's Avatar
New Jersey
Joined Feb 2003
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I had looked this up a while ago and the reason for the anhedral stab was due to its effect of yaw control believe it or not. For the main wings, +/- dihedral affects lateral stability (where +dihedral yields greater positive lateral stability). For the horizontal stabs +/- dihedral effects directional stability (where anhedral yields greater positive directional stability)

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Originally Posted by Brickyard View Post
Why does the Bandit have anhedral on it horizontal stabs? Maybe to keep them out of the wings disrupted air. Not sure how big the wind tunnel is, but perhaps the entire assembled aircraft should be put in.
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Old May 27, 2012, 11:24 PM
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Brickyard's Avatar
United States, NY, New York
Joined Dec 2008
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Originally Posted by Tumbler View Post
I had looked this up a while ago and the reason for the anhedral stab was due to its effect of yaw control believe it or not. For the main wings, +/- dihedral affects lateral stability (where +dihedral yields greater positive lateral stability). For the horizontal stabs +/- dihedral effects directional stability (where anhedral yields greater positive directional stability)
Thanks Brian
Interesting.. I remember thinking without the rear stab to support the tail, the tail would drop causing the plane to pitch upward toward the sky. I was amazed when I found the opposite, the rear stab is actually creating a downforce, almost like an upside down wing & without it the plane would dive toward the ground. Aerodynamics 101...lol. Anyways, very interesting that anhedral in the stabs affects yaw control.. I don't get it at all, but being a student of aviation for so long leads me to take a humble approach to aerodynamic theories.
It's mind boggling to me how some here claim to know for sure that there is no flutter/problem associated with this current design.
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Old May 27, 2012, 11:36 PM
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New Jersey
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I think all designs need a little tweaking. I remember reading the F-4 phantom started out with out the wing tips bent up and without anhedral stab and they found it to be totally unstable so they added dihedral to wing tips and anhedral to the full flying stab, Just an example how even the experts don;t get it right the first time.

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Originally Posted by Brickyard View Post
Thanks Brian
Interesting.. I remember thinking without the rear stab to support the tail, the tail would drop causing the plane to pitch upward toward the sky. I was amazed when I found the opposite, the rear stab is actually creating a downforce, almost like an upside down wing & without it the plane would dive toward the ground. Aerodynamics 101...lol. Anyways, very interesting that anhedral in the stabs affects yaw control.. I don't get it at all, but being a student of aviation for so long leads me to take a humble approach to aerodynamic theories.
It's mind boggling to me how some here claim to know for sure that there is no flutter/problem associated with this current design.
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Old May 27, 2012, 11:42 PM
Current project: Electrolyte
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
5,471 Posts
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Originally Posted by Brickyard View Post
Why does the Bandit have anhedral on it horizontal stabs? Maybe to keep them out of the wings disrupted air. Not sure how big the wind tunnel is, but perhaps the entire assembled aircraft should be put in.

The windtunnel is 24" at its narrowest point. Its a low speed tunnel so I doubt it will get close to the speeds required to flutter. Plus the dept. would not be very happy if something was sucked into their fan. At a few thousand dollars per hour to opperate the tunnel this test would be very expensive if the research was well done. Putting a little pocket camera on a flyable airframe might yield much better practical info.
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Old May 28, 2012, 09:24 AM
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Tamjets's Avatar
San Jose, CA
Joined Jun 2006
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Wind tunnel test. Why waste money. Get the elevator done right cost less.
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Old May 28, 2012, 10:20 AM
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United States, NY, New York
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Wind tunnel test. What a joke.
Simple design elevator everyone else know how to do it right and these folks screw up and still try to cover up they mistake.
They mistake cost customers money.
Hate to get into negativity, but really, no need to reinvent the wheel. You currently have more than a 50% "total loss" stat, with 100% due to elevator failure . At this point i think you should change it regardless, just to hopefully regain customer confidence in this plane.
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Old May 28, 2012, 10:47 AM
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Everett, WA
Joined Aug 2002
659 Posts
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Originally Posted by Tamjets View Post
Wind tunnel test. What a joke.
Simple design elevator everyone else know how to do it right and these folks screw up and still try to cover up they mistake.
They mistake cost customers money.
Wow... This is very low...

Do you know that you are leaving a very poor taste in the mind of the potential customers regarding you and your company?

Just a thought for you to ponder...

Dave

PS: I am a lowly consumer, sponsor by no one except my own paycheck! My purchase experiences and communication from them has always been positive. I will continue to purchase from them. Their action regarding this situation will further cement my mind as a great dealer.
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Old May 28, 2012, 10:55 AM
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San Jose, CA
Joined Jun 2006
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Originally Posted by eaticus View Post
Wow... This is very low...

Do you know that you are leaving a very poor taste in the mind of the potential customers regarding you and your company?

Just a thought for you to ponder...

Dave

PS: I am a lowly consumer, sponsor by no one except my own paycheck! My purchase experiences and communication from them has always been positive. I will continue to purchase from them. Their action regarding this situation will further cement my mind as a great dealer.
Fact is the elevator need some work before it can be safe to be air worthy.
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Old May 28, 2012, 11:13 AM
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eaticus's Avatar
Everett, WA
Joined Aug 2002
659 Posts
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Originally Posted by Tamjets View Post
Fact is major failure with the elevator...good for you continue buying stuff that fail.
Wow... Speechless...

EJF is working the problem. They are not ignoring it.

Ultimately, it is still the modeler's responsibility to build the model with utmost care.

Dave

PS: At this moment in time, my sons are watching cartoon, the animals in the cartoon are screaming "The Sky is falling, the Sky is falling..."
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Old May 28, 2012, 12:04 PM
Robert Wagoner's Avatar
Tucson, Arizona, USA
Joined Dec 1999
1,552 Posts
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Originally Posted by Brickyard View Post
I really don't like the look of this mod (Extreme_RC's).. I think it changes the outline too much. Lets be honest, it's a mini Bandit replica, & the swept design is all part of the look/success. I'll repost this drawing I did many pages back, & I remember seeing another like it. Het could make it longer at the root if desired, airfoil won't change.
1. maintains current look/profile
2. utilizes the existing stab/elevator
3. existing airfoil profile will remain 100% the same
4. flight characteristics unchanged
5. HET can utilize existing plugs/pieces to form the new one
6. easy to do at home if you don't feel like waiting on HET
7. Same BASIC design utilized by the (super successful) BVM Bandit.
"NOT TO SCALE"
Nice mod. I'm trying to review the messages with useful content to move forward and help resolve this. I happen to be working on projects nearby to that Windtunnel and it was suggested. if that's not needed then fine, just another option.

Many helpful people have been on the rcgroups for years and likewise many have been run off so I appreciate anyone trying to help and being constructive. I'm eager to help resolve this in the best way possible.

What about a straight across same width elevator. The Quickie 500's had those for years although I notice most are V-Tails now.

--RW
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Old May 28, 2012, 12:38 PM
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USA, CA, Aromas
Joined Sep 2010
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Quote:
What about a straight across same width elevator. The Quickie 500's had those for years although I notice most are V-Tails now.
absolutly it has a better chance for success and I would make the elevator width the same width as the stock one at the mid point between the center narrowest point and the tip widest point this would be my starting point
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Old May 28, 2012, 12:54 PM
Current project: Electrolyte
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
5,471 Posts
Not trying to be negative but didn't the same issue of a tail flutter come up several years ago with the original super sniper 90mm? Now with a "new" composite version with the same issue of flutter??? The single hingeline is a good idea for lower speed models but at a certain point you can't cut corners anymore. Instead of changing the stab design just make 2 hingelines (instead of 1) so the elevators taper towards the tips and use a servo for each surface. That would more than likely solve the problem.
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Old May 28, 2012, 01:36 PM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
21,779 Posts
tam...anybody who uses a little epoxy and tape to hold a servo on for a major control surface on a 150 plus mph 90mm model is asking for failure. could i blame you for a crash and make a huge deal out of it if i hotglue a stab servo in on a tam jets f16? i think not. get off your damned horse and go someplace else with your cocky attitude. its getting real old. the problem is beeing looked into and fixed. let it go man.
meanwhile i just put 3 more flights on mine today with a number of full power dives with 0 hint of flutter.
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Old May 28, 2012, 01:54 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
20,621 Posts
yep a few passes were really ripping for an 8s set up ..he was diving at full power . i only herd the duct howl and had a good visiual on the pull out as it was a 6ft high pass it looked very smooth .
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Old May 28, 2012, 02:12 PM
Fly allot, Crash allot, next?
United States, CA, Corona
Joined Feb 2006
7,234 Posts
Well, as I assemble mine, I thought I would read the manual which is on a disk included with the kit. OMG guess what it said? Perhaps we all should read the manual more often.

HIGH PERFORMANCE TIP --- Testing of this airframe has demonstrated that the stock Cloth Hinges are sufficient for “Sport Flying” but suffer from fatigue when repeated fast passes and High-G manuevers are performed. If you intend to fly your Sniper XL90 aggressively, a stronger hinge-type (i.e. nylon pinned hinges) are strongly recommended
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