First flying video taken at Damai with Flycam One.
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Friday, June 27, 2008
Saturday, May 3, 2008
Removing Unwanted Epoxy Blob / Stain from your Model?
How many times have you got that unwanted and excess epoxy after joining two joints together and leaving behind the ugly residue?
or
How many times have you got epoxied fingerprint all over your beloved models?
or
How many time have you tried to removed some dried out epoxy but failed?
Well here's the solution! Denatured Alcohol!
So what is this wonderful solvent? A quick definition and explanation of Denatured Alcohol here in the Wiki.
http://en.wikipedia.org/wiki/Methylated_spirits
or
How many times have you got epoxied fingerprint all over your beloved models?
or
How many time have you tried to removed some dried out epoxy but failed?
Well here's the solution! Denatured Alcohol!
Denatured Alcohol is a gentle, multi-purpose solvent, which is essential for thinning shellac and cleaning brushes. It evaporates quickly, making it an excellent glass cleaner. Also works great for cleaning metal, water rings, color-safe fabrics, and it is even used as a hot, clean-burning fuel for marine stoves. Best of all it removes epoxy! Even for long dried out epoxy, just 'soaked' it using Denatured Alcohol and clean / scrapped it off after that.
So what is this wonderful solvent? A quick definition and explanation of Denatured Alcohol here in the Wiki.
http://en.wikipedia.org/wiki/Methylated_spirits
Sunday, March 23, 2008
Wing Fence
The term “wing fence” may also be identified by the terms “boundary layer fence,” “potential fence,” or simply “fence.”
Wing fences have been used on swept wing aircraft for fifty years. The MiG-15, one of the earliest examples of their use, incorporated two fences on each wing. The F-86 used them as well. Fences can also be seen on more recent production aircraft like the Fiat G91 and the BAE Hawk and Harrier.
Despite their use on aircraft flying at supersonic and near supersonic speeds, wing fences are also of use on low speed swept wing aircraft such as man carrying sailplanes and RC models. The Akaflieg Braunschweig SB-13 and a rendition of Hans-Jürgen Unverferth’s CO8 by Glyn Fonteneau and Dave Camp serve as examples within those realms. Wing fences have both an interesting history and an interesting effect.
As we mentioned in the opening parenthetical paragraph, wing fences have had other terminologies applied to them. “Boundary layer fence” is the most common, so let’s take a critical look at that nomenclature for a moment.
Wing fences have been used on swept wing aircraft for fifty years. The MiG-15, one of the earliest examples of their use, incorporated two fences on each wing. The F-86 used them as well. Fences can also be seen on more recent production aircraft like the Fiat G91 and the BAE Hawk and Harrier.
Despite their use on aircraft flying at supersonic and near supersonic speeds, wing fences are also of use on low speed swept wing aircraft such as man carrying sailplanes and RC models. The Akaflieg Braunschweig SB-13 and a rendition of Hans-Jürgen Unverferth’s CO8 by Glyn Fonteneau and Dave Camp serve as examples within those realms. Wing fences have both an interesting history and an interesting effect.
A wing fence is nothing more than a flat plate which is attached perpendicular to the wing and in line with the free stream air flow. Wolfgang Liebe is credited as being the inventor of the device, for which he received a German patent in 1938, during his work on the Messerschmitt Bf 109B. The Messerschmitt Bf 109B had a rather peculiar stall.
The stall initiated at the wing root, and a cross span flow very near the leading edge then travelled outward toward the wing tip at high speed. The result of this aerodynamic behavior was that the entire wing stalled at essentially the same time, a very dangerous characteristic.
The stall initiated at the wing root, and a cross span flow very near the leading edge then travelled outward toward the wing tip at high speed. The result of this aerodynamic behavior was that the entire wing stalled at essentially the same time, a very dangerous characteristic.
Installation of a wing fence prevented the cross span flow, thus eliminating the stall problem. That a solid plate in the path of cross span flow close to the wing surface would obstruct the flow, as was seen on the Bf 109B, may seem obvious.
In actuality, however, the mechanism of operation was more covert in that the beneficial effect was provided by the initiation of a sideslip and the resulting vortex generated by the fence. Wing fences on swept wings have been found to be very beneficial to inhibiting the nasty stall behaviors which result from severe angles of sweep, but their operation in this environment is entirely different than on a straight wing such as the Bf 109B.
As we mentioned in the opening parenthetical paragraph, wing fences have had other terminologies applied to them. “Boundary layer fence” is the most common, so let’s take a critical look at that nomenclature for a moment.
The boundary layer is that region next to the surface of a solid body where there is an appreciable loss of total pressure. That is, the velocity is a fraction of the free stream flow. The boundary layer thickness is usually defined as the distance normal to the surface in which the velocity rises to 99% of that of the main flow. The boundary layer is in reality not very thick, usually a matter of a few millimeters, even on full size aircraft.
With the above definition in mind :
If a wing fence is constructed to be the same height as the boundary layer thickness, it is not effective. In fact, fences must be quite high to have any effect at all.
The boundary layer gets thicker toward the trailing edge of the wing, so if fence height were based on the boundary layer thickness the fence would be highest at the trailing edge of the wing. Yet extending the length of a fence much beyond 50% chord does not increase its effectiveness in the slightest.
Wing fences are generally more effective when they wrap around the leading edge.
The term “boundary layer fence” is, as illustrated by the above points, a misnomer. Wing fences do not affect the boundary layer directly, but rather do so indirectly by having an impact on the potential flow, the flow in which the vorticity is zero.
The term “potential fence” is derived from the action of the fence on the potential flow. Wing fences on swept wings work in a very complex way, and their action is not completely understood, but we’ll attempt to make the fundamental concepts easier to understand.
Begin by thinking of a swept wing panel mounted in a wind tunnel and its associated lift distribution, as shown in Figure 1. Note that if the right wall is removed we have a right wing panel for a swept back wing; if the left wall is removed we have the left wing panel of a swept forward wing.
From a slightly different perspective, by removing the walls and attaching a “mirror” wing panel to either the left or right end of the existing wing, we have a complete wing, swept either backward or forward, and an associated lift distribution as depicted in Figure 2.
We can consider a wing fence to be aerodynamically equivalent to a tunnel wall. This effect is demonstrated in a more comprehensive way in Figure 3.
Installing a wing fence changes the lift distribution on a swept back wing as depicted in Figure 4.
Note that on the inside of the fence the cl is higher while on the outside of the fence the cl is lower. This shifting of the load to the inside of the fence is very beneficial to stall behavior. The clmax should be located in the area approximately 40% of the semi-span from the wing root. At a high angle of attack, this should be the area of the wing which stalls, leaving the wing root and the wing tip to continue providing lift and a slight pitch down moment.
When high angles of attack lead to separated flow, the boundary layer is directly involved at a fundamental level. Corrective measures must influence the boundary layer in such a way that flow separation is limited or controlled to some extent. As previously said, wing fences do not directly influence the boundary layer.
Rather, they influence the potential flow which in turn effects the boundary layer. In general terms, the cl load on the wing tips is reduced, the boundary layer is maintained in such a way that separation is inhibited, and the stall behavior is made more benign. Rarely do wing fences extend farther than 1/3 of the wing chord. The forward third of the chord is the area of greatest lift. It is also the area where the sweep effect and the “mirror” principle, described in Figures 1 through 4, are most effective.
For use on RC sailplanes, wing fences are usually constructed using a profile similar to those shown in Figure 5 and are fabricated of stiff cardstock or plastic. They can be conveniently attached with tape for easy removal, replacement, and/or experimentation. The most common location for wing fences is between 40% and 60% of the wing span.
A location directly in front of the inner edge of the aileron or elevon has shown to be very effective at controlling adverse stall behaviors and maintaining control surface effectiveness at high angles of attack. Installing two fences on each wing panel, at 1/3 and 2/3 of the semi-span, has been found to be effective on high aspect ratio wings with steep sweep angles.
Wing fences are sometimes not easily seen. Most airliners have their engines mounted below the wing on pylons. The pylon itself serves as a fence for the lower surface, and the leading edge pylon fairing often comes over the leading edge, serving as a fence for the upper surface.
Controlling air flow to improve swept wing flight characteristics can be accomplished through a number of means - wing slots (as described in our August 1994 column), leading edge slats, and the “saw tooth” leading edge to name just a few. Wing fences are attractive, however, because they can be fabricated quickly, attached readily, and modified easily without affecting the main airframe in any way.
So far as cost and ability to experiment, they are the best suited solution.
With the above definition in mind :
If a wing fence is constructed to be the same height as the boundary layer thickness, it is not effective. In fact, fences must be quite high to have any effect at all.
The boundary layer gets thicker toward the trailing edge of the wing, so if fence height were based on the boundary layer thickness the fence would be highest at the trailing edge of the wing. Yet extending the length of a fence much beyond 50% chord does not increase its effectiveness in the slightest.
Wing fences are generally more effective when they wrap around the leading edge.
The term “boundary layer fence” is, as illustrated by the above points, a misnomer. Wing fences do not affect the boundary layer directly, but rather do so indirectly by having an impact on the potential flow, the flow in which the vorticity is zero.
The term “potential fence” is derived from the action of the fence on the potential flow. Wing fences on swept wings work in a very complex way, and their action is not completely understood, but we’ll attempt to make the fundamental concepts easier to understand.
Begin by thinking of a swept wing panel mounted in a wind tunnel and its associated lift distribution, as shown in Figure 1. Note that if the right wall is removed we have a right wing panel for a swept back wing; if the left wall is removed we have the left wing panel of a swept forward wing.
From a slightly different perspective, by removing the walls and attaching a “mirror” wing panel to either the left or right end of the existing wing, we have a complete wing, swept either backward or forward, and an associated lift distribution as depicted in Figure 2.
We can consider a wing fence to be aerodynamically equivalent to a tunnel wall. This effect is demonstrated in a more comprehensive way in Figure 3.
Installing a wing fence changes the lift distribution on a swept back wing as depicted in Figure 4.
Note that on the inside of the fence the cl is higher while on the outside of the fence the cl is lower. This shifting of the load to the inside of the fence is very beneficial to stall behavior. The clmax should be located in the area approximately 40% of the semi-span from the wing root. At a high angle of attack, this should be the area of the wing which stalls, leaving the wing root and the wing tip to continue providing lift and a slight pitch down moment.
When high angles of attack lead to separated flow, the boundary layer is directly involved at a fundamental level. Corrective measures must influence the boundary layer in such a way that flow separation is limited or controlled to some extent. As previously said, wing fences do not directly influence the boundary layer.
Rather, they influence the potential flow which in turn effects the boundary layer. In general terms, the cl load on the wing tips is reduced, the boundary layer is maintained in such a way that separation is inhibited, and the stall behavior is made more benign. Rarely do wing fences extend farther than 1/3 of the wing chord. The forward third of the chord is the area of greatest lift. It is also the area where the sweep effect and the “mirror” principle, described in Figures 1 through 4, are most effective.
For use on RC sailplanes, wing fences are usually constructed using a profile similar to those shown in Figure 5 and are fabricated of stiff cardstock or plastic. They can be conveniently attached with tape for easy removal, replacement, and/or experimentation. The most common location for wing fences is between 40% and 60% of the wing span.
A location directly in front of the inner edge of the aileron or elevon has shown to be very effective at controlling adverse stall behaviors and maintaining control surface effectiveness at high angles of attack. Installing two fences on each wing panel, at 1/3 and 2/3 of the semi-span, has been found to be effective on high aspect ratio wings with steep sweep angles.
Wing fences are sometimes not easily seen. Most airliners have their engines mounted below the wing on pylons. The pylon itself serves as a fence for the lower surface, and the leading edge pylon fairing often comes over the leading edge, serving as a fence for the upper surface.
Controlling air flow to improve swept wing flight characteristics can be accomplished through a number of means - wing slots (as described in our August 1994 column), leading edge slats, and the “saw tooth” leading edge to name just a few. Wing fences are attractive, however, because they can be fabricated quickly, attached readily, and modified easily without affecting the main airframe in any way.
So far as cost and ability to experiment, they are the best suited solution.
How to Convert a 2 Blade to a 3 or 4 Blade Propeller?
The conversion for a 3 and 4 bladed propeller is a simple tasked if you know what 2 bladed propeller you use on a given Engine or Motor. For example, on a three bladed propeller you would drop the diameter and keep the pitch. On a four bladed, you would drop the diameter and the pitch. For instance if you had a two bladed 24-10 propeller and you wanted a three bladed you would use a 22-10 and so on.
The performance on a 2 bladed verses a 3 bladed propeller is very little. A 3 or 4 bladed propeller will give you more thrust, and you will sacrifice a little speed. The big advantage to using a multi blade is that you have more ground clearance less noise factor.
The performance on a 2 bladed verses a 3 bladed propeller is very little. A 3 or 4 bladed propeller will give you more thrust, and you will sacrifice a little speed. The big advantage to using a multi blade is that you have more ground clearance less noise factor.
3 & 4 BLADED CONVERSION CHART
| Two Bladed | Three Bladed | Four Bladed |
| 10-6 | 9-6 | |
| 11-8 | 10-8 | 10-6 |
| 12-8 | 11-8 | 11-6 |
| 12-10 | 11-10 | 11-8 |
| 13-10 | 12-10 | 12-8 |
| 14-10 | 13-10 | 13-8 |
| 14-8 | 13-8 | 13-6 |
| 15-8 | 14-8 | 14-6 |
| 15-10 | 14-10 | 14-8 |
| 16-10 | 15-10 | 15-8 |
| 18-10 | 16-10 | 16-8 |
| 20-10 | 18-10 | 18-8 |
| 22-10 | 20-10 | 20-8 |
Tuesday, February 12, 2008
Thermal Soaring
Thermal soaring is one of the most intriguing of all aspects. It can be hard for the average person to understand how a plane can fly for hours and gain altitude without a motor!
It takes a lot of concentration to thermal soar effectively. A sailplane can fly along the edge of a thermal and unless the pilot is carefully watching the model he may not realize the opportunity to gain some altitude. Because most thermals are relatively small (a couple hundred feet in diameter or less at 400' altitude) compared to the rest of the sky, the sailplanes will rarely fly directly into the thermal and start rising.Generally, the sailplane will fly into the edge or near a thermal and the effects the thermal has on the plane may be almost unnoticeable. As the sailplane approaches a thermal, the wing tip that reaches the rising air first will be lifted before the opposite wing tip. This causes the plane to “bank” and turn away from where we would like the plane to go.
When you are thermal soaring, try to fly as smoothly and straight as possible. Trim the plane to fly in a straight line and only touch the controls when you have to. Watch the sailplane carefully and it will tell you what it is encountering.When the sailplane flies directly into a thermal it will either start rising or stop sinking. Either case is reason enough to start circling (especially in a contest where every second counts). Fly straight ahead until you feel like you are in the strongest lift, fly a couple of seconds farther (so your circle will be centered in the strongest lift) and then start circling in a fairly tight but smooth turn. When the sailplane is low the turns have to be tighter to stay in the strongest lift. As the plane gains altitude, the turns can be larger and flatter. The flatter the turn, the more efficient the plane is flying, but don’t be afraid to really “crank” it into a steep bank when you are low. If you see the plane falling off on one side of the turn, move your circle over into the stronger lift. Thermals move along with the wind so as you circle you will be swept along with it. Be careful when thermaling, that you don’t get so far downwind you can’t make it back to the field to land. If the sailplane is flying along straight and all of a sudden turns, let the plane continue to bank (you may have to give it some rudder to keep it banking) until it has turned 270°(3/4 of a full circle). Straighten out the bank and fly into whatever turned the plane. If you encounter lift, and you won’t every time, start circling just as you did when flying directly into a thermal.
Thermals are generated all day long, but the strongest thermals are produced when the sun is directly overhead. 10:00 am – 2:00 pm seems to be the best time to get those“killer” thermals. Some of these thermals can be very large and you may find it hard to get out of them. If you find yourself getting too high, don’t dive the plane to get out of the lift. Sailplanes are very efficient aircraft and they will build up a lot of speed and could “blow up” in the rough air of a thermal. The easiest way to lose altitude is to apply full rudder and full up elevator. This will put the plane into a tight spin that will not over stress the air frame but it will enable it to lose altitude very quickly. This is especially helpful if the sailplane gets sucked into a cloud or it gets too high to see.The twirling action will give the sun a better chance off lashing off of the wing and catching your attention. When you are high enough and want to leave the thermal, add a little down trim to pick up some speed and fly 90 degrees to the direction of the wind. If you are not real high and want to find another thermal, you may want to look upwind of the last thermal. The same source that generated this thermal is probably producing another. Just watch out for “sink” which is often found behind and between thermals.
As you might expect, with all this air rising, there is also air sinking. This air is the sailplane pilot’s nightmare that can really make soaring challenging. “Sink” is usually not as strong as the thermals in the same area, but it can be very strong. Down drafts of many hundreds of feet per minute are common on a good soaring day. These down drafts can make a sailplane look like it is falling out of the air. Because of this, it is important that you do not let the sailplane get too far downwind.
When encountering sink, immediately turn and fly 90 degrees to the direction of the wind (towards you if possible). Apply a little “down elevator” and pick up some speed to get out of the sink as fast as possible. Every second you stay in the sink is precious altitude lost.
It takes a lot of concentration to thermal soar effectively. A sailplane can fly along the edge of a thermal and unless the pilot is carefully watching the model he may not realize the opportunity to gain some altitude. Because most thermals are relatively small (a couple hundred feet in diameter or less at 400' altitude) compared to the rest of the sky, the sailplanes will rarely fly directly into the thermal and start rising.Generally, the sailplane will fly into the edge or near a thermal and the effects the thermal has on the plane may be almost unnoticeable. As the sailplane approaches a thermal, the wing tip that reaches the rising air first will be lifted before the opposite wing tip. This causes the plane to “bank” and turn away from where we would like the plane to go.
When you are thermal soaring, try to fly as smoothly and straight as possible. Trim the plane to fly in a straight line and only touch the controls when you have to. Watch the sailplane carefully and it will tell you what it is encountering.When the sailplane flies directly into a thermal it will either start rising or stop sinking. Either case is reason enough to start circling (especially in a contest where every second counts). Fly straight ahead until you feel like you are in the strongest lift, fly a couple of seconds farther (so your circle will be centered in the strongest lift) and then start circling in a fairly tight but smooth turn. When the sailplane is low the turns have to be tighter to stay in the strongest lift. As the plane gains altitude, the turns can be larger and flatter. The flatter the turn, the more efficient the plane is flying, but don’t be afraid to really “crank” it into a steep bank when you are low. If you see the plane falling off on one side of the turn, move your circle over into the stronger lift. Thermals move along with the wind so as you circle you will be swept along with it. Be careful when thermaling, that you don’t get so far downwind you can’t make it back to the field to land. If the sailplane is flying along straight and all of a sudden turns, let the plane continue to bank (you may have to give it some rudder to keep it banking) until it has turned 270°(3/4 of a full circle). Straighten out the bank and fly into whatever turned the plane. If you encounter lift, and you won’t every time, start circling just as you did when flying directly into a thermal.
Thermals are generated all day long, but the strongest thermals are produced when the sun is directly overhead. 10:00 am – 2:00 pm seems to be the best time to get those“killer” thermals. Some of these thermals can be very large and you may find it hard to get out of them. If you find yourself getting too high, don’t dive the plane to get out of the lift. Sailplanes are very efficient aircraft and they will build up a lot of speed and could “blow up” in the rough air of a thermal. The easiest way to lose altitude is to apply full rudder and full up elevator. This will put the plane into a tight spin that will not over stress the air frame but it will enable it to lose altitude very quickly. This is especially helpful if the sailplane gets sucked into a cloud or it gets too high to see.The twirling action will give the sun a better chance off lashing off of the wing and catching your attention. When you are high enough and want to leave the thermal, add a little down trim to pick up some speed and fly 90 degrees to the direction of the wind. If you are not real high and want to find another thermal, you may want to look upwind of the last thermal. The same source that generated this thermal is probably producing another. Just watch out for “sink” which is often found behind and between thermals.
As you might expect, with all this air rising, there is also air sinking. This air is the sailplane pilot’s nightmare that can really make soaring challenging. “Sink” is usually not as strong as the thermals in the same area, but it can be very strong. Down drafts of many hundreds of feet per minute are common on a good soaring day. These down drafts can make a sailplane look like it is falling out of the air. Because of this, it is important that you do not let the sailplane get too far downwind.
When encountering sink, immediately turn and fly 90 degrees to the direction of the wind (towards you if possible). Apply a little “down elevator” and pick up some speed to get out of the sink as fast as possible. Every second you stay in the sink is precious altitude lost.
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