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Mini Q
- Thread starter Glenn Beer
- Start date
Diceman
Moderator
You get a forward tumble when too nose heavy? I have never experienced that, so I wouldn't know. But when the plank is too tail heavy, it is very pitch sensitive. First flights of any plane is always safest to be a bit nose heavy. Then you can start moving CG back and see how you like it. The CG the manufactures give us is the best starting point. It is all on preference where we actually like it and where it ends up.
I thought I had my Sunbird pretty well dialed years ago. I didn't fly it for a long while because something was weird about it and I could not put my finger on it. Flying on the front side mainly back then, I think I moved the CG back some to get it to be more aerobatic. Maybe I moved a bit too far, but I had Mehrdad fly it at the slot one day and he agreed on how poorly it was flying and doing strange things. He then told me to add nose weight at bit at a time and each time it was getting better and better until we had it dialed in real good. Now that I use it mainly for DS he had told me to add a bit more nose weight. The carbon Sunbird is a fantastic DS ship as well having speeds up to 200 mph by Alan Caconie (or however you spell his last name, LOL)
I thought I had my Sunbird pretty well dialed years ago. I didn't fly it for a long while because something was weird about it and I could not put my finger on it. Flying on the front side mainly back then, I think I moved the CG back some to get it to be more aerobatic. Maybe I moved a bit too far, but I had Mehrdad fly it at the slot one day and he agreed on how poorly it was flying and doing strange things. He then told me to add nose weight at bit at a time and each time it was getting better and better until we had it dialed in real good. Now that I use it mainly for DS he had told me to add a bit more nose weight. The carbon Sunbird is a fantastic DS ship as well having speeds up to 200 mph by Alan Caconie (or however you spell his last name, LOL)
We have made some suggestions to the manufacturer. Being that we only have had the one batch of planes from them, it will be interesting to see how well they respond to our requests. Thus far they have been great to work with and usually have a positive response, but as I say, until you open the box of planes, you really never know.
I like the idea of top drive, but keep the bottom servo pockets. Basically have them flip the hinges to the bottom surface. Should be easy to accomplish. It does make the build a little more difficult, but I guess if you wanted you could just let the servo arm pop out the top and have a totally exposed linkage setup.
These planes are pretty darn cheap, fly great and can be built in a single night. There is a lot to like here. Can't wait for the next batch.
I like the idea of top drive, but keep the bottom servo pockets. Basically have them flip the hinges to the bottom surface. Should be easy to accomplish. It does make the build a little more difficult, but I guess if you wanted you could just let the servo arm pop out the top and have a totally exposed linkage setup.
These planes are pretty darn cheap, fly great and can be built in a single night. There is a lot to like here. Can't wait for the next batch.
Konrad
Very Strong User
As long as we aren't talking about divergent flight, most pitch sensitivity is as a result of too much control movement. When narrowing the margin of stability (moving the Cofg aft) it is a good idea to cut down on the control throws. Yes, the amount of dampening (margin of stability) is a personal thing.
With a nose heavy plank one needs to carry a lot more reflex at trim speed. As the plane speeds up this reflex forces the nose up into a climb. To maintain level flight one removes some of the reflex (forward stick). At some point this removal of reflex changes the pitching moment of the airfoil from positive to negitive. When this happens the wing will tumble forward, making a great lomcevak.
Some flying wings like the Klingberg 100 have variable CofG that are moved as a function of speed. Variable CofG allows a flying wing to have a much broader speed range.
With a nose heavy plank one needs to carry a lot more reflex at trim speed. As the plane speeds up this reflex forces the nose up into a climb. To maintain level flight one removes some of the reflex (forward stick). At some point this removal of reflex changes the pitching moment of the airfoil from positive to negitive. When this happens the wing will tumble forward, making a great lomcevak.
Some flying wings like the Klingberg 100 have variable CofG that are moved as a function of speed. Variable CofG allows a flying wing to have a much broader speed range.
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Diceman
Moderator
True, but also can come from being to tail heavy as well, just like I had with the Mini Q this past weekend. You could just barely move the control surface a half of mm or less and it was real pitch sensitive even with 40% expo. LOL. Added nose weight and it flew 100% better. 
I guess when you say "tumble" I pictured flipping end over end. I have never experienced this action.
I guess I have never put that much weight on the nose of a flying wing to experience that much distress in a flying wing to just tumble to the ground. LOL. I could see how that is possible though. Even with the Mini Q being way out of CG (too tail heavy) and having 3mm of reflex in the wing, when I push forward on the elevator stick, it did not tumble. But I guess if I had 100% throw and pushed all the way forward on the stick, then yes, I am sure it would not have gone so well.
CG definitely effects speed as well as maneuverability. You put more nose weight in the plane it becomes faster and more stable, but maneuverability goes down (less aerobatic). Move the CG toward the tail heavy side and the plane becomes more aerobatic, but less stable. Most flying wings do not have a broad or variable range of CG. CG is much more critical on a flying wing than a tail and rudder plane. On flying wings it is best to balance the plane on a sharper point or ball point than the traditional flat circle pad. The Mini Q is one of these planes for sure.
I guess when you say "tumble" I pictured flipping end over end. I have never experienced this action.
I guess I have never put that much weight on the nose of a flying wing to experience that much distress in a flying wing to just tumble to the ground. LOL. I could see how that is possible though. Even with the Mini Q being way out of CG (too tail heavy) and having 3mm of reflex in the wing, when I push forward on the elevator stick, it did not tumble. But I guess if I had 100% throw and pushed all the way forward on the stick, then yes, I am sure it would not have gone so well.
CG definitely effects speed as well as maneuverability. You put more nose weight in the plane it becomes faster and more stable, but maneuverability goes down (less aerobatic). Move the CG toward the tail heavy side and the plane becomes more aerobatic, but less stable. Most flying wings do not have a broad or variable range of CG. CG is much more critical on a flying wing than a tail and rudder plane. On flying wings it is best to balance the plane on a sharper point or ball point than the traditional flat circle pad. The Mini Q is one of these planes for sure.
Konrad
Very Strong User
Yep, tumble was a forward flip with little or no loss of altitude. Actually neat to see, but if unplanned in a high speed pass scary!
If you notice more speed as you go more nose heavy it is because you are upping the wing loading. If you kept the wing loading the same moving the CofG forward should slow you down as you would need more up trim (reflex), trim drag.
Variable CofG is not a range but rather servo controlled placement of mass. The stable CofG range is defined by the aerodynamic of the design,( airfoil, wing planform etc).
I'm not advocating being "tail heavy" (unstable). I am saying that narrowing the margin of stability does make a flying wing much more enjoyable over a broader range of speeds.
I suspect that in your example of being tail heavy with 3mm of reflex that you weren't able to take out enough reflex to change the airfoil from a positive pitching moment to one with negative pitching moment.
I set my initial balance on the sharp edge of a table or the use of books (to make a trough to clear the fuselage). I'm not aware of the traditional circular pad. After that I balance by how the ship responds in flight.
All the best,
Konrad
If you notice more speed as you go more nose heavy it is because you are upping the wing loading. If you kept the wing loading the same moving the CofG forward should slow you down as you would need more up trim (reflex), trim drag.
Variable CofG is not a range but rather servo controlled placement of mass. The stable CofG range is defined by the aerodynamic of the design,( airfoil, wing planform etc).
I'm not advocating being "tail heavy" (unstable). I am saying that narrowing the margin of stability does make a flying wing much more enjoyable over a broader range of speeds.
I suspect that in your example of being tail heavy with 3mm of reflex that you weren't able to take out enough reflex to change the airfoil from a positive pitching moment to one with negative pitching moment.
I set my initial balance on the sharp edge of a table or the use of books (to make a trough to clear the fuselage). I'm not aware of the traditional circular pad. After that I balance by how the ship responds in flight.
All the best,
Konrad
Diceman
Moderator
Here is some mini Q specs just thought I would share.
| Mini Q Slope Soarer Specifications | ||
|---|---|---|
| Wing span | 0.81 m | 32 in |
| Wing area | 10.2 dm2 | 158 sq in |
| Length | 43 cm | 17 in |
| Flying weight from | 336 g | 11.9 oz |
| Wing loading | 33 g/dm | 10.8 oz/sq ft |
| Aspect ratio | 6.4 | |
| Wing airfoil | 7% proprietary | |
| Dihedral (EDA) | 2.5º | |
| Centre of Gravity | 17 - 22 mm from wing leading edge | |
| Controls | Elevons |
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