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Old Nov 26, 2012, 07:02 AM
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Mark
Glad you got it down in one piece. I noticed that there was a lot of down and right thrust induced as a result of the tilted firewall (down and to the right). I assumed it was correct by design. Yet another design issue to deal with.

G-Forced
As for down thrust, how much down thrust is in your model (you have the original design that may be different than ours).

Thanks for the info on the elevator push rod. Although some of us are veteran builders, it is always good to get reminders to check these types of problems especially when they result in flight performance issues.
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Last edited by Iflyrc_vic; Nov 26, 2012 at 07:37 AM. Reason: edited
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Old Nov 26, 2012, 07:33 AM
Battery Puffer
Orange, California, United States
Joined Nov 2001
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The leading edge of the left elevator is twisted down enough to need almost 10mm to get it back to normal. I have to remove it and see if it can even be fixed. I may have to build another one. It was causing the plane to crab and roll left and fight any right rudder. I never had a plane be such a handfull.

Mark
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Old Nov 26, 2012, 07:43 AM
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Flight/Design Issues

Quote:
Originally Posted by MarkF View Post
The leading edge of the left elevator is twisted down enough to need almost 10mm to get it back to normal. I have to remove it and see if it can even be fixed. I may have to build another one. It was causing the plane to crab and roll left and fight any right rudder. I never had a plane be such a handfull.

Mark
Although I have not flown mine yet, I am thankful for all of the flight report issues listed in this thread. As I have noted in my posting, this plane has some serious design issues that have caused many experienced pilots major flight problems. I am VERY CONCERNED about taking mine out for the maiden flight.

G-Forced, I think you got lucky or you are just a better pilot than most of us.
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Old Nov 26, 2012, 11:10 AM
Battery Puffer
Orange, California, United States
Joined Nov 2001
1,126 Posts
I think the container got really hot inside on the trip over and caused some serious warping. This has happened many times before and there's not a lot the vender can do about it. I doubt I could get any replacement parts for it. Anybody remember the web site we got these planes from at a discount?

Mark
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Old Nov 26, 2012, 11:26 AM
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Quote:
Originally Posted by MarkF View Post
I think the container got really hot inside on the trip over and caused some serious warping. This has happened many times before and there's not a lot the vender can do about it. I doubt I could get any replacement parts for it. Anybody remember the web site we got these planes from at a discount?

Mark
I got mine from General Hobby (generalhobby.com). they don't have any spare parts.
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Old Nov 26, 2012, 04:50 PM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
Joined Nov 2006
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Quote:
Originally Posted by Iflyrc_vic View Post
Mark
Glad you got it down in one piece. I noticed that there was a lot of down and right thrust induced as a result of the tilted firewall (down and to the right). I assumed it was correct by design. Yet another design issue to deal with.

G-Forced
As for down thrust, how much down thrust is in your model (you have the original design that may be different than ours).

Thanks for the info on the elevator push rod. Although some of us are veteran builders, it is always good to get reminders to check these types of problems especially when they result in flight performance issues.
About 5c or so.
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Old Nov 26, 2012, 04:56 PM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
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Quote:
Originally Posted by MarkF View Post
The leading edge of the left elevator is twisted down enough to need almost 10mm to get it back to normal. I have to remove it and see if it can even be fixed. I may have to build another one. It was causing the plane to crab and roll left and fight any right rudder. I never had a plane be such a handfull.

Mark
The best way to completely eliminate warped wood is to lightly soak it, and then apply heat. As the moister evaporates, the wood will expand back to its original shape. If you check the start of this thread you can see my R-3 came badly damage and I used this technique to repair it back to as good as new.

Just a side note, This is a very experimental plane that for many reasons, was never built as a full size. There are always going to be development areas and its no 3D plane or proven pattern plane. Its different, fast and has a high wing loading with a long fuse and smallest tail... lol.. anyone that know anything about optimal design layouts for both directional stability and general handling knows this is not it. But its looks and flys great. Its just something you need to fly differently.
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Old Nov 26, 2012, 10:40 PM
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This was the damage ( after I removed the covering ) from shipping. Actually, there were a few more damaged parts but with water and a covering iron and alot of patience, it come back to shape before I recovered it. I have used a similar method on my MXs that had a warped inboard wing and it worked great but it goes without saying, you are going to have to recover effected areas.
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Old Nov 27, 2012, 09:43 AM
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Dumb Move

Guys, I have discovered that I have made a HUGE blunder in the construction of my plane. I feel like an absolute dummy, rookie, stupid, and total dumb-ass.

As I was checking my elevators to see if they were setup properly, I discovered that they are, in fact set for equal travel and are not warped. I was also checking the line up of the stabilizer to the main wing when I noticed a BIG PROBLEM.

The horizontal stablizer is actually a "flying stab" that has a flat bottom and a slightly curved upper surface. The upper curvature is very minor but it is there. I installed mine upside down! The flat side is on top and the curve is on the bottom - BAD JU JU.

With all of the other problems I have had with building this model, this one takes the cake. Now I have got to figure out some way to "neatly" remove the stabilizer so that I can turn it over.

What an idiot!!!
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Old Nov 27, 2012, 05:10 PM
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Australia, NSW, Sydney
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Oh dear :-( They should be easy enough to cut the CA hinges away then simply cut slots in another location. Cant see this being a big issue.. just a PITA !
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Old Nov 28, 2012, 12:00 PM
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Airfoil stabilizer

After kicking myself in the butt for this possible blunder, I did some research on horizontal stabilizers. I was absolutely surprised to find that some planes are actually designed with "upside Down" horizontal stabilizers.

Here are a few excerpts for internet articles on this subject:

1. The horizontal on most aircraft is shaped like a wing, only upside down. Take a look at one next time you go to the airport, It's curved on the bottom and flat on top, it's done this way to improve handling and reduce the chances of a stall by keeping the nose from raising and stalling, it is always trying to push the nose down. The low pressure area of a wing is above it, on the horizontal, it's below it.

2. Cambered airfoils create a pitching moment that would cause the plane to pitch nose down. The tailplane actually needs to create negative lift (ie: lift downwards) to counter this.

3. So all of my aero engineering undergrad work, and any post graduation study agrees with the stated conclusions, i.e. the stab should be symmetrical or upside down cambered. So given that the math/aerodynamics proves this, why do we keep seeing stabs with the airfoil on the top? Sometimes set at negative rigging angles! From now on, I'm ignoring kit designers and going with what I know, i.e. airfoil on the bottom.

4. Having a lifting tail can be dangerous if your flight speeds vary greatly. Main problem would be the tail trying to lift at high speed causing a downward pitching, increasing speed and then you have to correct with up deflection.

5. Typically, the greatest effort on the part of the horizontal stabilizer is during the landing flare. Here you’re flying very slowly, and so the stab needs to rely on airfoil shape, and it’s angle of attack in order to produce the required downforce (Note we’re talking horizontal stab AOA… not wing AOA). This downforce is used to raise the nose of the aircraft so that it can assume the two point landing attitude (nose high). If you put an inverted airfoil on the tail, you can create more down force at the horizontal stabilizer to do exactly this, raise the nose. The aircraft designer needs to make sure that the horizontal stabilizer doesn’t stall during the flare process. If the horizontal stab were to stall during flare, you’d suddenly lose almost all of the downforce at the tail, and the nose of the aircraft would violently drop. Not a desirable situation on landing for obvious reasons.

6. The horizontal stabilizers on most RC model planes are small and create very little lift an either direction. Most are semetrical and have zero lift. Elevators are used to change the lift at the tail.


With this information, I am going to leave my stabilizer as it is. The horizontal stabilizer on this model is set at zero AOA and is smaller than most and therefore should create minimal lift, up or down. The inverted airfoil may even help the flight characteristics of this model - certainly won't hurt.

Vic
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Last edited by Iflyrc_vic; Nov 28, 2012 at 12:08 PM.
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Old Nov 28, 2012, 03:39 PM
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Who knows... it might fly better lol
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Old Nov 29, 2012, 09:51 PM
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Final details

Well, I have finished the build for this model. No more. Complete! Done!

This has been one hell of a project. As stated previously, I will not perform the maiden until maintenance has been performed on my flying field for next season. I can therefore get a long look at this great looking model. Here are a few photos of my final details (arming plug, pilot figure and decals).
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Old Nov 29, 2012, 10:14 PM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
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Well done but it would KILL me to not go and fly it now ! Surely you can find a suitable field ? I really like your stand you built. Might have to build one too !
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Old Nov 30, 2012, 01:33 PM
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Quote:
Originally Posted by G-Forced View Post
I really like your stand you built. Might have to build one too !
The wonders of PVC piping! Cheap and easy to work with....
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