johnr Posted August 20, 2012 Report Share Posted August 20, 2012 Hi All, We are fortunate in Australia in not only being allowed constant speed props but we can legally use the full speed potential of the CT by going to -12 degree flaps. I would like to make the necessary adjustment & I presume that is all that is required. Has anyone on the forum experience of what is entailed & could they please share the knowledge.If it is to sensitive to post on this forum I could be contacted off line. Thanks . John Link to comment Share on other sites More sharing options...
Roger Lee Posted August 20, 2012 Report Share Posted August 20, 2012 Hi John, We can talk through PM about how since it's legal there, but you 'll be surprised that what you seek to gain is very little. I have tested it on 4 planes so I have some good data. All on ground adjustable setups. Your best addition is an in flight adjustable prop if you don't have one and to go from a 65" to a 68" prop. Component combinations are important. Just doing one thing is usually very disappointing. I have heard a few claims, but it isn't a reality without all the component combinations in place and even then some claims are just out there especially if the air speed gauge is off a little which happens. Link to comment Share on other sites More sharing options...
FastEddieB Posted August 20, 2012 Report Share Posted August 20, 2012 Logically speaking... ...at some point wouldn't negative flaps become de facto spoilers? Seems like there would be a very narrow range where they might be of some benefit, but its hard to figure. Link to comment Share on other sites More sharing options...
Tom Baker Posted August 20, 2012 Report Share Posted August 20, 2012 Logically speaking... ...at some point wouldn't negative flaps become de facto spoilers? Seems like there would be a very narrow range where they might be of some benefit, but its hard to figure. The answer is yes to your question, they indeed would become spoilers. The reason for the negative flaps on our airplane is because of the airfoil shape. The trailing edge curls down. I think the airfoil comes from the sailplane community. With the -12° flaps the trailing edge is in line with the airflow reducing drag, instead of curling down. Link to comment Share on other sites More sharing options...
FredG Posted August 20, 2012 Report Share Posted August 20, 2012 Tom, do you know what the actual flap angles (0, -6, -12, etc) are in reference to? From what reference line on the plane do the flap angles refer to? Thanks. Fred Link to comment Share on other sites More sharing options...
Roger Lee Posted August 20, 2012 Report Share Posted August 20, 2012 From the zero angle which aligns with the little protrusion off the fuselage at the zero flap setting. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted August 20, 2012 Report Share Posted August 20, 2012 Are not all such measurements made from the wing chord line? Link to comment Share on other sites More sharing options...
Roger Lee Posted August 20, 2012 Report Share Posted August 20, 2012 Yes they are, but that also lines the flaps up with a fuselage protrusion at the zero setting. Look at the CT flap and the fuselage in zero flaps and you'll see what I mean. This is the reference point for the flap settings. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted August 21, 2012 Report Share Posted August 21, 2012 Yes they are, but that also lines the flaps up with a fuselage protrusion at the zero setting. Look at the CT flap and the fuselage in zero flaps and you'll see what I mean. This is the reference point for the flap settings. Cool, I just wanted to make sure I understood the aerodynamics. Link to comment Share on other sites More sharing options...
johnr Posted August 21, 2012 Author Report Share Posted August 21, 2012 Hi John, We can talk through PM about how since it's legal there, but you 'll be surprised that what you seek to gain is very little. I have tested it on 4 planes so I have some good data. All on ground adjustable setups. Your best addition is an in flight adjustable prop if you don't have one and to go from a 65" to a 68" prop. Component combinations are important. Just doing one thing is usually very disappointing. I have heard a few claims, but it isn't a reality without all the component combinations in place and even then some claims are just out there especially if the air speed gauge is off a little which happens. Thanks for that info Roger, If there is little benefit I will give it a miss. I thought maybe there was a similar reduction in drag as there is when changing from 0 to -6. Thats like taking the brake off, in fact the Ct tells me at 100Kn that I need -6. On another subject I am a little disappointed with the 2 blade Neuform, its not nearly as smooth as the Warp drive on the Jodel. In fact I think I may try the Warp Drive to prove my assumption. Ted said he had the best climb , but it was maybe because of a lesser load. What was your opinion?. Best Regards John Link to comment Share on other sites More sharing options...
FlyingMonkey Posted August 21, 2012 Report Share Posted August 21, 2012 Thanks for that info Roger, If there is little benefit I will give it a miss. I thought maybe there was a similar reduction in drag as there is when changing from 0 to -6. Thats like taking the brake off, in fact the Ct tells me at 100Kn that I need -6. On another subject I am a little disappointed with the 2 blade Neuform, its not nearly as smooth as the Warp drive on the Jodel. In fact I think I may try the Warp Drive to prove my assumption. Ted said he had the best climb , but it was maybe because of a lesser load. What was your opinion?. Best Regards John That leads me to another question. I know that handbooks for the CTs say to use -6° for speeds above 100kt, but is that a speed requirement or a structural one? In other words, is it a case where the CT just will not go much above 100kt at 0° and needs the reflexed flaps to get there, or is it required to reduce drag loading on the wings/flaps that could cause damage? Or is it neither, and the CT will get there either way and it's just more efficient at -6°? I guess I'm wondering what would happen if a pilot was in cruise flight at normal cruise rpm (5400+) and forgot to go to -6° and left them at 0°...would he just burn more gas and go slower, or would the consequences be more dire? Link to comment Share on other sites More sharing options...
Roger Lee Posted August 21, 2012 Report Share Posted August 21, 2012 Hi John, I hope this helps. I had a Warp 66" 3 blade on my CT for years. I have 6 CT's at my field with a Neuform 65" (Used to be stock stock), a Neuform red 2 blade (used to be stock a long time ago), a 66" Warp Drive (used to be optional with FD) and a Sensenich 68" 3 blade which now comes on all CTLS. I have tested 5 other Sensenich props of different lengths (Sensenich ask me to do some research), 2&3 blade and different stiffness blades. I flew these planes side by side in test against the other CT's at the field to get some real time comparisons and all with a max rpm right at 5600 rpm WOT. A couple planes had -6 and a couple -12. Two blade props just have a different vibration frequency. It isn't bad, just different. I can certainly feel it in the air frame while flying. The 2 blade has a courser frame vibration over the 3 blade with a little finer vibration frequency. The bottom line after a couple of months of testing was that so long as everyone (-6 &-12) had there WOT rpm set to 5600 or at least the same and we flew 5200 rpm we all were the same speed. I do think that a 3 blade is a little smoother, but just because of its vibration frequency. Now here is one thing I did find. The Sensenich 68" which is what FD now puts on the CTLS would out climb the Warp fairly easily. The Sensenich is also a much lighter prop because it is a composite and the Warp is solid and the lighter prop makes it easier on the gearbox during starts and stops and any additional vibration into the engine components. It is important to static and dynamic balance the Warp, but the Sensenich can get away with just a dynamic balance. I believe your Neuform 2 blade will out perform the Warp in a climb. Cruise speed should be the same. If I had to buy a new prop I would pick the Sensenich 68" 3 blade right now over the others and partly because that is what FD would give an LOA for and they have moved on from the other props. Sensenich or Warp doesn't have the 1000 hr. send it back inspection, the blades are easy to come by and the other blades can take the outside elements better than a Neuform. Neuform wants their props hangared and not left outside. Either way I would always use a prop cover on any prop blade outside. Link to comment Share on other sites More sharing options...
Jim Meade Posted August 21, 2012 Report Share Posted August 21, 2012 There is a lot of discussion of the number of prop blades. Among the factors involved in prop choices are tip speed, aspect ratio, number of blades, speed of the aircraft, fixed or variable pitch, engine horsepower and more. For light, slow planes like we have, it is generally agreed that 2 blade props are simpler and more efficient in cruise. 3 blade props are a little better in climb, have better ground clearance, are smoother, are quieter (and some think just look better - hmmm how would four look ). Simply put, a 2 blade prop is best except when it isn't. Since we are theoretically speed limited, and most of us are not out to sip the last drop of gas, that probably doesn't make much difference and you can choose based on construction, looks, price, smoothness, climb performance or (gasp) manufacturer recommendation. Of course, a one-bladed prop would be better yet. It has an efficiency gain over all others, though not much. It has been used in motorized gliders and models. I don't know of any production aircraft that used it, although I understand some prototypes tried it out. You can find a lot of info by searching on "one blade airplane propeller" and "2 blade versus 3 blade propellers". Link to comment Share on other sites More sharing options...
Tom Baker Posted August 21, 2012 Report Share Posted August 21, 2012 That leads me to another question. I know that handbooks for the CTs say to use -6° for speeds above 100kt, but is that a speed requirement or a structural one? In other words, is it a case where the CT just will not go much above 100kt at 0° and needs the reflexed flaps to get there, or is it required to reduce drag loading on the wings/flaps that could cause damage? Or is it neither, and the CT will get there either way and it's just more efficient at -6°? I guess I'm wondering what would happen if a pilot was in cruise flight at normal cruise rpm (5400+) and forgot to go to -6° and left them at 0°...would he just burn more gas and go slower, or would the consequences be more dire? The negative flaps are for reducing loading on the trailing edge, or aleast that's what I was told by someone at FD Germany. The airfoil has a down curl at the trailing edge. Link to comment Share on other sites More sharing options...
Jim Meade Posted August 21, 2012 Report Share Posted August 21, 2012 Does anyone know what airfoil was used for the wing? Link to comment Share on other sites More sharing options...
FlyingMonkey Posted August 22, 2012 Report Share Posted August 22, 2012 The negative flaps are for reducing loading on the trailing edge, or aleast that's what I was told by someone at FD Germany. The airfoil has a down curl at the trailing edge. So...damage can be done by cruising at 0° instead of 6°? Link to comment Share on other sites More sharing options...
Roger Lee Posted August 22, 2012 Report Share Posted August 22, 2012 Hi Andy, The short answer is no you won't damage the plane in zero flap cruise. You are technically supposed to be under a certain speed in zero cruise. That said if you forgot to go to -6 from zero it just slows you down. I have watched a lot of CT pilots forget to switch to -6 from zero. Now here is where it could cause a problem over time. Trying to go to zero while flying too fast. It puts too much pressure on the flap servo motor. Eventually it may cause it to malfunction. Each flap position has a speed that the plane should be under before going down to that flap position. Just like larger aircraft. Link to comment Share on other sites More sharing options...
johnr Posted August 22, 2012 Author Report Share Posted August 22, 2012 Hi John, I hope this helps. I had a Warp 66" 3 blade on my CT for years. I have 6 CT's at my field with a Neuform 65" (Used to be stock stock), a Neuform red 2 blade (used to be stock a long time ago), a 66" Warp Drive (used to be optional with FD) and a Sensenich 68" 3 blade which now comes on all CTLS. I have tested 5 other Sensenich props of different lengths (Sensenich ask me to do some research), 2&3 blade and different stiffness blades. I flew these planes side by side in test against the other CT's at the field to get some real time comparisons and all with a max rpm right at 5600 rpm WOT. A couple planes had -6 and a couple -12. Two blade props just have a different vibration frequency. It isn't bad, just different. I can certainly feel it in the air frame while flying. The 2 blade has a courser frame vibration over the 3 blade with a little finer vibration frequency. The bottom line after a couple of months of testing was that so long as everyone (-6 &-12) had there WOT rpm set to 5600 or at least the same and we flew 5200 rpm we all were the same speed. I do think that a 3 blade is a little smoother, but just because of its vibration frequency. Now here is one thing I did find. The Sensenich 68" which is what FD now puts on the CTLS would out climb the Warp fairly easily. The Sensenich is also a much lighter prop because it is a composite and the Warp is solid and the lighter prop makes it easier on the gearbox during starts and stops and any additional vibration into the engine components. It is important to static and dynamic balance the Warp, but the Sensenich can get away with just a dynamic balance. I believe your Neuform 2 blade will out perform the Warp in a climb. Cruise speed should be the same. If I had to buy a new prop I would pick the Sensenich 68" 3 blade right now over the others and partly because that is what FD would give an LOA for and they have moved on from the other props. Sensenich or Warp doesn't have the 1000 hr. send it back inspection, the blades are easy to come by and the other blades can take the outside elements better than a Neuform. Neuform wants their props hangared and not left outside. Either way I would always use a prop cover on any prop blade outside. Hi Roger , Thanks for that information. I rode & tuned motorcycles in my youth & if it "felt right" it usually was.After flying the Jodel with the 3 blade warp drive the 2 blade Neuform in the CTsw does not "feel" right. It seems rough ( maybe vibration maybe just the coarser pitch) especially below 5000rpm. I have checked all blades & they are the same. I think it is maybe caused by the size & pitch of the blade. I have retorqued & checked it but no change. The engine will get 5500 at 5000ft WOT so pitch as you had it is pretty much spot on. It would be hard to justify the out lay of a new ground adjustable 3blade prop as I am sure that you are correct in the improvements would be marginal. I may experiment in the future with the 3 blade warp drive from the Jodel. Would it help if the prop was turned say 30degrees in relation to its position on the flange.?. Theory says that it is in balance at 360 but loading may be different. I would appreciate your opinion. The warp drive on the Jodel is a 68" . Best regards John Link to comment Share on other sites More sharing options...
Runtoeat Posted August 22, 2012 Report Share Posted August 22, 2012 John, have you dynamically balanced your prop? I was getting a little vibration during quarter trailing winds - on the ground and while flying. My A&P dynamically balanced the prop and it made vibrations go mostly away. Doing a better carb balance cleaned up the remaining 10% of the vibration. Now all is good. A 1.25" dia. x 3/32" thick steel washer was needed at one of the prop bolts to get things balanced out. Link to comment Share on other sites More sharing options...
Tom Baker Posted August 22, 2012 Report Share Posted August 22, 2012 Hi Andy, The short answer is no you won't damage the plane in zero flap cruise. You are technically supposed to be under a certain speed in zero cruise. That said if you forgot to go to -6 from zero it just slows you down. I have watched a lot of CT pilots forget to switch to -6 from zero. Now here is where it could cause a problem over time. Trying to go to zero while flying too fast. It puts too much pressure on the flap servo motor. Eventually it may cause it to malfunction. Each flap position has a speed that the plane should be under before going down to that flap position. Just like larger aircraft. Roger, I was told by FD Germany that the reason for the limit is to prevent overloading the flap structure. Link to comment Share on other sites More sharing options...
Jim Meade Posted August 22, 2012 Report Share Posted August 22, 2012 CTSW POH 4.2 lists flap settings a an operating limitation. Vfe. That is, it is a limitation on the flap setting, not a limitation on flap operating. Per FAR 1.2, V FE means maximum flap extended speed. Link to comment Share on other sites More sharing options...
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