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A fellow pilot was seen experimenting with negative angle on his horizontal stabiliser recently. Thing is that his HS is right smack bang in the centre of his prop wash.question 1: Does any of the general airflow around the aircraft intergrate with and have any affect of the air within the prop blast and if so what would be a rough percentage? question 2: Would negative incidence on a small HS smack bang in the centre of the prop wash have a desirable affect on helping keep the nose up as speed is increased.PeteBairnsdale,Vic.
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Gidday Pete. - My opinions:-1)The air from within the prop blast all comes from the general airflow around the aircraft, hence one reason for noisy propellers. The prop creates a low pressure area directly in front of it and air will rush into the low pressure area from wherever it can. With forward speed, most of the air will feed in from around the aircraft.2)Yes, but the negative incidence must be in relation to the horizontal flight datum, (not the keel). Tim McClureBroken Hill
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Gidday Pete. - My opinions:-1)The air from within the prop blast all comes from the general airflow around the aircraft, hence one reason for noisy propellers. The prop creates a low pressure area directly in front of it and air will rush into the low pressure area from wherever it can. With forward speed, most of the air will feed in from around the aircraft.2)Yes, but the negative incidence must be in relation to the horizontal flight datum, (not the keel). Tim McClureBroken Hill
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Given the above, with a total of say .25 sq.meter surface area, would any secondary HS in the prop blast be better:1. Flat plate with negative incidence.2. Flat on top, aerofoil bottom surface.3. Full flying surfaces top and bottom and negative incidence.4. Flat on top, aerofoil bottom surface and negative incidence.PeteBairnsdale,Vic.
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Given the above, with a total of say .25 sq.meter surface area, would any secondary HS in the prop blast be better:1. Flat plate with negative incidence.2. Flat on top, aerofoil bottom surface.3. Full flying surfaces top and bottom and negative incidence.4. Flat on top, aerofoil bottom surface and negative incidence.PeteBairnsdale,Vic.
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Pete, plotting lift/drag curves for different airfoils is a very specialist field. Perhaps you should run this one past Chuck Beaty.Having said that, the "efficiency" of the airfoil used in a H/S is not a vital factor because its performance is not critical as an efficient lifting device.Where a wing has to have area, it needs strength to support the load, which means some sort of internal structure is required. An airfoil is an efficient way to streamline the internal structure for the least possible drag. The design of that airfoil will determine its efficiency as a lifting device.To be cont.Tim McClureBroken Hill
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Pete, plotting lift/drag curves for different airfoils is a very specialist field. Perhaps you should run this one past Chuck Beaty.Having said that, the "efficiency" of the airfoil used in a H/S is not a vital factor because its performance is not critical as an efficient lifting device.Where a wing has to have area, it needs strength to support the load, which means some sort of internal structure is required. An airfoil is an efficient way to streamline the internal structure for the least possible drag. The design of that airfoil will determine its efficiency as a lifting device.To be cont.Tim McClureBroken Hill
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Pete, These two seat machines have the HS set at about 1 degree negative AOA and are all in the center of the prop. All the helicopters I have seen have either negative angle or inverted airfoil (zero AOA) HS's. In the second image you can clearly see the forward tilt on the tall tail.On this machine I set the HS angle at 1.5 degrees to make up for the higher thrust line.All the engines are level. In my opinion you need a serious HS on a two seat(especially side by side).Image Insert:
57.64Â KBImage Insert:
56.9Â KBImage Insert:
69.97Â KBM Barker
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Pete, These two seat machines have the HS set at about 1 degree negative AOA and are all in the center of the prop. All the helicopters I have seen have either negative angle or inverted airfoil (zero AOA) HS's. In the second image you can clearly see the forward tilt on the tall tail.On this machine I set the HS angle at 1.5 degrees to make up for the higher thrust line.All the engines are level. In my opinion you need a serious HS on a two seat(especially side by side).Image Insert: 57.64Â KBImage Insert: 56.9Â KBImage Insert: 69.97Â KBM Barker
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I had to take my "mack the knife" to work. Someone has got to keep me in my habits.A flat plate has an abrupt stall which would normally be considered undesirable. In the case of a H/Z on a gyro, it is not considered to be much of a problem because (a) by the time you stall it, you would probably be in trouble anyway, and (b) there would be a sudden increase in drag which in itself has a correcting effect. At our low speeds, a cambered airfoil is more efficient than a symmetrical airfoil, for creating lift in a particular direction. A symmetrical airfoil is more efficient if it is required to operate in both directions (eg rudder)In my opinion, a reverse cambered airfol would make the most efficient and effective H/S, but given sufficient area for all options to supply equal lift (or downforce,) then the differences would be minimal at the speeds in which we operate.Brian's noise generator above (orange tail) is a good graphic example of a negative angle at work (given that the dodgy pilot is flying it level). The keel could have sloped up or down and it wouldn't have mattered as long as the end result is as the designer intended.Tim McClureBroken Hill
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I had to take my "mack the knife" to work. Someone has got to keep me in my habits.A flat plate has an abrupt stall which would normally be considered undesirable. In the case of a H/Z on a gyro, it is not considered to be much of a problem because (a) by the time you stall it, you would probably be in trouble anyway, and (b) there would be a sudden increase in drag which in itself has a correcting effect. At our low speeds, a cambered airfoil is more efficient than a symmetrical airfoil, for creating lift in a particular direction. A symmetrical airfoil is more efficient if it is required to operate in both directions (eg rudder)In my opinion, a reverse cambered airfol would make the most efficient and effective H/S, but given sufficient area for all options to supply equal lift (or downforce,) then the differences would be minimal at the speeds in which we operate.Brian's noise generator above (orange tail) is a good graphic example of a negative angle at work (given that the dodgy pilot is flying it level). The keel could have sloped up or down and it wouldn't have mattered as long as the end result is as the designer intended.Tim McClureBroken Hill
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Those legs need a bit of sun...Nicholas TomlinAlarmist - www.alarmist.com.au - we scare for you
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Those legs need a bit of sun...Nicholas TomlinAlarmist - www.alarmist.com.au - we scare for you
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Thanks Tim and Murray. The existing HS is very adequately sized as it is but no harm in helping it if I can. You have confirmed my thoughts Tim and I will go the cambered way.PeteBairnsdale,Vic.
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Thanks Tim and Murray. The existing HS is very adequately sized as it is but no harm in helping it if I can. You have confirmed my thoughts Tim and I will go the cambered way.PeteBairnsdale,Vic.
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