雖然Stall Turn可以有好多變化, 但玩得多都會覺得悶...
Spin比Stall Turn困難少少, 因為做得好唔好係同機體及Settings有直接關係, 每一款機種嘅特性都唔同, 唯有多作試驗才可找出最適合嘅配搭...
以下篇文章, 解釋得相當詳細...
SPINS
To spin or not to spin? That's a good question. Most planes will spin, but some are a lot easier to spin than others. Several factors affect an aircraft's ability to spin, but for a conventional plane, you can generally reduce them to CG (balance) and surface throws. Some aircraft don't recover easily from spins; in fact, some don't recover at all! So, before you start to spin your pride and joy, please follow the designer's set-up instructions carefully. A spin occurs when an aircraft is stalled then autorotates around its CG toward earth at a constant speed. If the speed builds, the aircraft doesn't stall, it spirals. Some airplanes spin in a fairly nose-down attitude, others in a flatter attitude. Many spin at about a 45-degree angle.
YOUR FIRST SPIN
Let's assume that you've set up your aircraft properly. Now climb to plenty of altitude (200 feet or more), point the nose into the wind, and cut the power to idle. You may want to climb slightly, as this helps to slow the aircraft more rapidly. As you slow down, you'll need an increasing amount of up-elevator to maintain altitude - until either the aircraft stalls or you run out of elevator and the aircraft mushes down, i.e., the airplane is still flying, but it's descending with the nose slightly down and full up-elevator. If it mushes, this means you haven't stalled, so it won't spin.
There are two adjustments you can make to help the airplane spin. Either add more elevator throw, or move the CG aft, i.e., toward the tail. I usually start by adding elevator throw in small increments until the plane stalls or becomes too pitch-sensitive at high speed. If your elevator is as sensitive as you like it and it still won't stall, try adding tail weight gradually. Eventually, with enough elevator and tail weight, your plane should stall. Remember, too much tail weight can mean disaster, so be careful.
Not all airplanes behave the same way after they've stalled. Some drop wingtips first and enter unprovoked spins. To recover, you must "unstall" the wing (I'll discuss this later). When your plane is near a stall, its air speed is low; under these conditions, rudder is the most powerful control. For example, you can use it to help your plane overcome a left-dropping wing so that it drops the right wing and enters into a right turning spin.
HERE WE GO
Now that you can stall the aircraft properly, you're ready to enter the spin. At the moment of stall, as the nose falls past the horizon, apply full rudder and aileron in the same direction, and maintain the full up-elevator. Generally, left-turning spins are easier to enter than right-turning spins because the engine's torque can assist.
If the plane spun as defined, great! If not, you probably need more rudder throw. Don't be shy; go to high rate and add rudder until your plane spins properly. In some planes, I've found that additional aileron can help as well. (Contrary to what some people claim, it can really make the difference.) There's a fairly small margin between an aerobatic setup and instability, so make changes to your aircraft gradually.
NOW WHAT?
To recover from a spin, simply let go of the controls, and the autorotation should stop. The nose will point toward the ground, and air speed will be very low because the plane has just recovered from a stalled condition. At the moment of recovery, speed will consequently increase, but don't immediately pull up-elevator, or you may accidentally start another stall/spin. Let the air speed build slightly, and then carefully apply up-elevator to recover from the dive.
If you let go of the controls and the spin continues, you have a real problem. Before you give up, try some down-elevator and, if you can remember, rudder that's opposite to the rotation of the spin. That should do it. If it doesn't, hold down-elevator and opposite rudder, and add some power. If these methods don't work, start planning to repair your pride and joy. You gave it your best shot! The good news is, if it's in a true spin, it will descend fairly slowly, which can minimize the damage.
VARIATIONS
The spin you've just read about is an "inside spin from upright." An outside spin from upright requires down-elevator at the stall point (along with full opposing rudder and aileron), so that the plane will "pitch through" the horizon and keep going until it's in an inverted position. It will then be in an inverted spin. The spin entry is described as "outside" because it requires down-elevator to perform (just like an outside loop).
Your plane should be able to perform these other interesting spin variations with the same setup that enables it to do a conventional spin. If it can't, carefully adjust your aircraft as noted above, but also keep in mind that not all aircraft can perform all maneuvers.
INVERTED SPINS
This time, approach from inverted, and stall as you did from upright, but use down-elevator to stall. Once the plane has stalled, add full rudder, opposite aileron and full down-elevator. Recovery is the same as in an upright spin, except you'll recover to inverted using down-elevator. It's often easier to enter an inverted spin, but it can also be more difficult to recover from one, so beware. Also, if you must apply rudder to get out of an inverted spin, apply it in the same direction as the spin.
FLAT SPINS
Flat spins are really fun to do and watch, but your plane often must be set up on the edge of instability to perform a true flat spin. A flat spin is "more developed," i.e., the plane rotates and descends more slowly, and its angle in relation to the horizon is flatter. Some planes will develop flat spins from conventional spins after a few turns, but they generally must be coaxed. (I've also found that it's easier to flat-spin from inverted than from upright.) To coax your plane into a flat spin, enter a spin, then try to remove aileron input slowly, or even add opposite aileron. A plane I recently flew required opposite aileron and then a slow application of down-elevator to coax it into a flat spin, but it was a beautiful flat spin! Sometimes you have to experiment to find the right combination. A very important note: flat spins can be extremely difficult to recover from, so perform your first ones with plenty of altitude.
KNIFE-EDGE
The unusual-looking knife-edge spin is becoming more popular. Basically, instead of spinning around the nose, the plane spins around a wing tip. I've found that the easiest way to enter this maneuver is after you've established a conventional spin. Then, simply apply opposite rudder. On some planes, it only seems to work from inverted, but one thing is for sure: you'll lose altitude very rapidly, so start with plenty of height! You can also change the type of spin as you perform it, e.g., upright to inverted to knife-edge. Just remember the recovery technique you'll need to get out of your fancy spin!
Thursday, November 15, 2007
Thursday, November 8, 2007
IMAC has been around for over 24 years, and its original intent and premise have managed to remain fundamentally intact for nearly a quarter of a century because of their simplicity.
IMAC's goal is simple: "To duplicate full-scale aerobatics with RC aircraft in a realistic manner that is challenging for the contestants as well as interesting for the spectators."
Basically, IMAC competition is broken into two completely separate events: "Compulsory" and "Freestyle". Scoring for each is kept separate, and you do not have to enter both to compete. By far the most popular is "Compulsory" - a set of 14 to 16 maneuvers grouped together to form a sequence. These sequences are changed yearly and often reflect the maneuvers flown by the full-scale Inter-national Aerobatic Club (IAC). Scoring is based on a perfect 10 for each maneuver, with downgrades for Tournament of Champions.
Here are some tips and insights on how to begin flying IMAC.
The beginning category is called "Basic". Basic is the first 10 maneuvers of the Sportsman sequence.
Take a minute to review the 1998 sequence and follow along.
Start by entering into the wind, wings level. Call the box to the judges by saying, "In the box!"
1. Loop:
Fly to the center of the box (straight in front of you) and perform an inside loop. The loop should be symmetrical, centered and should end at the same place as you started it. Make the loop at least 100 feet in diameter, or it will present terribly. Exit straight and level and head to the end of the box for the next maneuver.
2. Hammerhead (also called a Stall Turn):
From level flight, pull vertical and head straight up. Pull back on the power. As the plane approaches zero airspeed, apply full rudder in either direction to allow the plane to rotate around its center of gravity. After the plane rotates and begins heading downward, slowly release the rudder. Retrace your upward line and exit with the same radius as you entered. Exit straight and level and head to the center of the box for the next maneuver.
3. Two Continuous Rolls:
Before you reach the center, apply aileron to begin rolling. Your goal is to have the plane cross the center pole as you begin your second roll. As you watch your plane roll, feed down-elevator when inverted and up-elevator when upright to keep your plane from losing elevation. The roll rate is not important, but maintaining heading and elevation is.
Note: these rolls are continuous, and stopping anytime during the maneuver will earn you a zero! Exit straight and level and head to the end of the box for the next maneuver.
4. Immelmann:
Use the same technique as you used with a full loop, but immediately after executing the half loop, roll to upright without losing heading or elevation. Maintain this higher elevation and begin reducing throttle for your next maneuver.
5. Two-Turn Spin:
As you approach the center pole, reduce throttle to idle and begin holding the nose up with your elevator. The pitch of the plane is not important as long as you don't gain altitude. Your goal is to have the plane stall right over the center pole. When the nose finally falls, begin applying full aileron and rudder in the same direction to induce a spin. The direction of the spin is not important. Just before you have completed two full revolutions, let go of the stick and recover heading straight down. After establishing your downline, pull level and exit. Head to the end of the box for the next maneuver.
6. Half Cuban-8:
As you approach the edge of the box, pull back on thestick and perform 5/8 of an inside loop. As you approach the 5/8 mark, begin feeding in down-elevator to establish an inverted 45-degree downline; calculate how far it is to your entry altitude and roll upright when you are halfway there. As you approach your entry altitude, apply up-elevator to exit with the same radius as you drew during the loop portion. Maintain wings level and head to the other end of the box for the next maneuver.
7. Humpty Bump Half Roll Down:
As you approach the end of the box, pull vertical with a radius you can easily duplicate throughout the maneuver. Head straight up long enough to establish a vertical line, and perform a half loop at the top with the same radius as used to enter the maneuver. Don’t forget to reduce throttle to idle before you pull over the top, or you will be screaming toward the ground. As you begin heading straight down, calculate at which altitude you’ll want to exit, and perform a half roll when you are halfway there. Now end the maneuver with the same radius, heading back toward the center of the box, wings level.
8. Hammerhead, 1/4 Roll Up, 1/4 Roll Down:
Immediately before approaching the center pole, pull vertical with a gradual radius and head straight up. Decide how tall you want to make the maneuver, and when you are halfway there, roll the plane 1/4 revolution.
Note: you can roll in either direction, but the preferred method to make the maneuver easier is to be looking at the top of your airplane instead of the bottom. Now, cut the throttle as you approach the top of the maneuver, and perform a hammerhead as previously described. After the hammerhead, proceed straight down and 1/4 roll in the opposite direction at exactly the same location as before. Continue straight down and exit with the same radius and altitude as you entered. Fly to the end of the box, wings level for the next maneuver.
9. Humpty Bump, Half Roll Up:
This is basically the same as the other Humpty, except you roll on the way up instead of on the way down. Be sure to keep the radiuses the same throughout the maneuver. Head to the end of the box, wings level for the next maneuver.
10. Half Reverse Cuban-8:
Way before you approach the end of the box, pull the plane to a 45-degree upline and decide how high you want to make the maneuver. Hold the 45; when you are halfway to the top of the maneuver, roll to inverted, apply a little down-elevator to maintain the 45-degree line and continue upward. When you have reached the top, reduce the throttle and begin your 5/8 inside loop. Begin with a radius that will ensure that you end up at the altitude where you started. End the maneuver with wings level and call, "Out of the box!".
IMAC's goal is simple: "To duplicate full-scale aerobatics with RC aircraft in a realistic manner that is challenging for the contestants as well as interesting for the spectators."
Basically, IMAC competition is broken into two completely separate events: "Compulsory" and "Freestyle". Scoring for each is kept separate, and you do not have to enter both to compete. By far the most popular is "Compulsory" - a set of 14 to 16 maneuvers grouped together to form a sequence. These sequences are changed yearly and often reflect the maneuvers flown by the full-scale Inter-national Aerobatic Club (IAC). Scoring is based on a perfect 10 for each maneuver, with downgrades for Tournament of Champions.
Here are some tips and insights on how to begin flying IMAC.
The beginning category is called "Basic". Basic is the first 10 maneuvers of the Sportsman sequence.
Take a minute to review the 1998 sequence and follow along.
Start by entering into the wind, wings level. Call the box to the judges by saying, "In the box!"
1. Loop:
Fly to the center of the box (straight in front of you) and perform an inside loop. The loop should be symmetrical, centered and should end at the same place as you started it. Make the loop at least 100 feet in diameter, or it will present terribly. Exit straight and level and head to the end of the box for the next maneuver.
2. Hammerhead (also called a Stall Turn):
From level flight, pull vertical and head straight up. Pull back on the power. As the plane approaches zero airspeed, apply full rudder in either direction to allow the plane to rotate around its center of gravity. After the plane rotates and begins heading downward, slowly release the rudder. Retrace your upward line and exit with the same radius as you entered. Exit straight and level and head to the center of the box for the next maneuver.
3. Two Continuous Rolls:
Before you reach the center, apply aileron to begin rolling. Your goal is to have the plane cross the center pole as you begin your second roll. As you watch your plane roll, feed down-elevator when inverted and up-elevator when upright to keep your plane from losing elevation. The roll rate is not important, but maintaining heading and elevation is.
Note: these rolls are continuous, and stopping anytime during the maneuver will earn you a zero! Exit straight and level and head to the end of the box for the next maneuver.
4. Immelmann:
Use the same technique as you used with a full loop, but immediately after executing the half loop, roll to upright without losing heading or elevation. Maintain this higher elevation and begin reducing throttle for your next maneuver.
5. Two-Turn Spin:
As you approach the center pole, reduce throttle to idle and begin holding the nose up with your elevator. The pitch of the plane is not important as long as you don't gain altitude. Your goal is to have the plane stall right over the center pole. When the nose finally falls, begin applying full aileron and rudder in the same direction to induce a spin. The direction of the spin is not important. Just before you have completed two full revolutions, let go of the stick and recover heading straight down. After establishing your downline, pull level and exit. Head to the end of the box for the next maneuver.
6. Half Cuban-8:
As you approach the edge of the box, pull back on thestick and perform 5/8 of an inside loop. As you approach the 5/8 mark, begin feeding in down-elevator to establish an inverted 45-degree downline; calculate how far it is to your entry altitude and roll upright when you are halfway there. As you approach your entry altitude, apply up-elevator to exit with the same radius as you drew during the loop portion. Maintain wings level and head to the other end of the box for the next maneuver.
7. Humpty Bump Half Roll Down:
As you approach the end of the box, pull vertical with a radius you can easily duplicate throughout the maneuver. Head straight up long enough to establish a vertical line, and perform a half loop at the top with the same radius as used to enter the maneuver. Don’t forget to reduce throttle to idle before you pull over the top, or you will be screaming toward the ground. As you begin heading straight down, calculate at which altitude you’ll want to exit, and perform a half roll when you are halfway there. Now end the maneuver with the same radius, heading back toward the center of the box, wings level.
8. Hammerhead, 1/4 Roll Up, 1/4 Roll Down:
Immediately before approaching the center pole, pull vertical with a gradual radius and head straight up. Decide how tall you want to make the maneuver, and when you are halfway there, roll the plane 1/4 revolution.
Note: you can roll in either direction, but the preferred method to make the maneuver easier is to be looking at the top of your airplane instead of the bottom. Now, cut the throttle as you approach the top of the maneuver, and perform a hammerhead as previously described. After the hammerhead, proceed straight down and 1/4 roll in the opposite direction at exactly the same location as before. Continue straight down and exit with the same radius and altitude as you entered. Fly to the end of the box, wings level for the next maneuver.
9. Humpty Bump, Half Roll Up:
This is basically the same as the other Humpty, except you roll on the way up instead of on the way down. Be sure to keep the radiuses the same throughout the maneuver. Head to the end of the box, wings level for the next maneuver.
10. Half Reverse Cuban-8:
Way before you approach the end of the box, pull the plane to a 45-degree upline and decide how high you want to make the maneuver. Hold the 45; when you are halfway to the top of the maneuver, roll to inverted, apply a little down-elevator to maintain the 45-degree line and continue upward. When you have reached the top, reduce the throttle and begin your 5/8 inside loop. Begin with a radius that will ensure that you end up at the altitude where you started. End the maneuver with wings level and call, "Out of the box!".
Tuesday, October 9, 2007
我有習慣收集各種數據, 以備不時之需...
在新手階段, 對槳嘅運用唔係咁明白...
用唔同嘅摩打, 知道需要配合唔同嘅槳...
但推力是多少? 負載電流會唔會過大令摩打Overload? 摩打轉數及空速? 應該點樣選擇? 以甚麽為依據?
一大堆問題, 真係一籌莫展...
為解決以上嘅疑慮, 決定自製一個靜態推力量度器...
材料 :
- 廚房電子磅
- 3mm Plywood
- 三角木條
- 電子變速器
- 接收器
- Eagle Tree MicroPower eLogger
- Eagle Tree Brushless RPM Sensor
製作好簡單, 用Plywood做Motor Mount, 最重要係上下兩塊一定要平行...
由於靜態推力係用壓磅法量度, 所以隻槳安裝嘅方向要稍為注意, 運轉向前方向一定要向下...
駁上eLogger及RPM Sensor, 電壓、電流及轉速等數據就可以記錄低, 只要專心留意電子磅數據就可以...
另外, 亦可加上Thermal Sensor, 量度摩打温度, 測試數據更為全面...
我亦特別保留一排1800mAh 16C電池, 專為測試摩打用, 令數據更為公平...
因為安全理由, 唔用Servo Tester控制電子變速...
用接收器控制電子變速, 測試時相距摩打四至五呎, 萬一有意外, 都無咁易俾隻槳打到自己...
用同一個摩打, 不同Size或Pitch嘅槳, 靜態推力及轉速都會唔同...
我會用摩打廠方嘅建議為依據, 測試及記錄唔同槳嘅特性, 為日後作為參考...
以上為例:
APC 9x6E出到950g靜態推力, 10x5E就出到1050g...
但轉速就以9x6E為高, 加上Pitch較10x5E高, 所以空速較快...
另一樣要注意就係負載電流, 10x5E比9x6E耗電, 所以要留意摩打温度及廠方所訂嘅最大容許負載電流...
要點樣選擇槳? 因人而異, 唔同機種或唔同機手, 要求都唔同...
要機速, 選9x6E...
要推力, 選10x5E...
要更高推力玩3D, 可選負載電流更高嘅10x4.7SF...
所以一定要定下目標, 才可以揀到最適合嘅配搭...
在新手階段, 對槳嘅運用唔係咁明白...
用唔同嘅摩打, 知道需要配合唔同嘅槳...
但推力是多少? 負載電流會唔會過大令摩打Overload? 摩打轉數及空速? 應該點樣選擇? 以甚麽為依據?
一大堆問題, 真係一籌莫展...
為解決以上嘅疑慮, 決定自製一個靜態推力量度器...
材料 :- 廚房電子磅
- 3mm Plywood
- 三角木條
- 電子變速器
- 接收器
- Eagle Tree MicroPower eLogger
- Eagle Tree Brushless RPM Sensor
製作好簡單, 用Plywood做Motor Mount, 最重要係上下兩塊一定要平行...
由於靜態推力係用壓磅法量度, 所以隻槳安裝嘅方向要稍為注意, 運轉向前方向一定要向下...
駁上eLogger及RPM Sensor, 電壓、電流及轉速等數據就可以記錄低, 只要專心留意電子磅數據就可以...
另外, 亦可加上Thermal Sensor, 量度摩打温度, 測試數據更為全面...
我亦特別保留一排1800mAh 16C電池, 專為測試摩打用, 令數據更為公平...
因為安全理由, 唔用Servo Tester控制電子變速...
用接收器控制電子變速, 測試時相距摩打四至五呎, 萬一有意外, 都無咁易俾隻槳打到自己...
用同一個摩打, 不同Size或Pitch嘅槳, 靜態推力及轉速都會唔同...
我會用摩打廠方嘅建議為依據, 測試及記錄唔同槳嘅特性, 為日後作為參考...
以上為例:
APC 9x6E出到950g靜態推力, 10x5E就出到1050g...
但轉速就以9x6E為高, 加上Pitch較10x5E高, 所以空速較快...
另一樣要注意就係負載電流, 10x5E比9x6E耗電, 所以要留意摩打温度及廠方所訂嘅最大容許負載電流...
要點樣選擇槳? 因人而異, 唔同機種或唔同機手, 要求都唔同...
要機速, 選9x6E...
要推力, 選10x5E...
要更高推力玩3D, 可選負載電流更高嘅10x4.7SF...
所以一定要定下目標, 才可以揀到最適合嘅配搭...
Friday, September 28, 2007
Monday, September 24, 2007
我每次整木機都會遇到一個問題: Hinge好硬, 當行程去到盡時, Servo好大機會Dee Dee聲...
依家10g樓下嘅Servos, 大部份Torque都唔會好大, 所以如果Hinge硬, 會增加Servo嘅負擔...
以下係喺"On the Flightline"見到嘅Tips, 可以作為參考.
8 Tips to install CA hinges
When gluing CA hinges into the slots for a model's control surfaces, there are a few things to do to make the job neater and easier.
另一問題, 究竟條狹縫要留幾闊?
最美觀當然係無縫, 氣流亦係最好, 但要整到暢順就唔係咁易...
所以通常我都會留一根大頭針嘅闊度, 唔太闊唔太窄, 啱哂我呢啲又要整又要懶嘅人...
亦睇過有外國師兄, 寧要最大行程, 放棄外觀...
佢哋留一條闊縫, 再用膠紙封番條縫, 做到最大彈性...
由於啲Hinge落CA黐實後都仲係頗硬(已經都只係落咗一滴CA咁大把), 所以我會用銼仔, 上下兩邊銼薄啲個Hinge, 為求更加暢順...
以Aileron為例, 我會磨到Aileron可以自己重量下降到50%最大行程...
不過要小心同要有耐性, 如太重手, Hinge就會變得太弱, 一撞就斷...
依家10g樓下嘅Servos, 大部份Torque都唔會好大, 所以如果Hinge硬, 會增加Servo嘅負擔...
以下係喺"On the Flightline"見到嘅Tips, 可以作為參考.
8 Tips to install CA hinges
When gluing CA hinges into the slots for a model's control surfaces, there are a few things to do to make the job neater and easier.
- Use a sharp hobby blade and remove a thin sliver from above and below the horizontal slot to make a very shallow V. This helps clear covering material away from the slot and exposes some of the wood around the slot.
- Use a small 1/6-inch drill and drill a hole in the center of each slot. This will help wich glue into the hinge cavity.
- Mark the middle of the hinges with a pencil so you can install them equally into the control surface and the supporting surface.
- Use thin CA, not medium or thick CA. Thin CA will wick more easily into the hinge slot.
- Place the hinges into the movable surfaces first and apply two or three drops of adhesive to each side of the hinge. Wipe away excess glue with a paper towel.
- Slide the hinges into the matching slots and center the control surface so it is in the proper position. Be sure there is clearance on either side of the surface so the hinge does not bind.
- Apply two or three drops on the hinges to glue them into place. Use a paper towel to absorb any excess glue that may have wicked into the space between the hinges.
- Don't use kicker or accelerator to speed glue time. Let the glue dry slowly for a strong bond.
另一問題, 究竟條狹縫要留幾闊?
最美觀當然係無縫, 氣流亦係最好, 但要整到暢順就唔係咁易...
所以通常我都會留一根大頭針嘅闊度, 唔太闊唔太窄, 啱哂我呢啲又要整又要懶嘅人...
亦睇過有外國師兄, 寧要最大行程, 放棄外觀...
佢哋留一條闊縫, 再用膠紙封番條縫, 做到最大彈性...
由於啲Hinge落CA黐實後都仲係頗硬(已經都只係落咗一滴CA咁大把), 所以我會用銼仔, 上下兩邊銼薄啲個Hinge, 為求更加暢順...
以Aileron為例, 我會磨到Aileron可以自己重量下降到50%最大行程...
不過要小心同要有耐性, 如太重手, Hinge就會變得太弱, 一撞就斷...
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