Incedence and thrust angles.....
11-14-2011 | 10:26 AM
#1
Thread Starter
Incedence and thrust angles.....
on and older H9 CAP 232.
See thread here for reference; http://www.rcuniverse.com/forum/m_10804273/tm.htm
In the process of the rebuild and am wondering if it would be prudent to set the wing/horizontal stab incidence to 0 & 0. I plan on some right and down thrust and am thinking 1 & 1????
I guess I should say this is a 60 2C size plane and I had an Enya 90 4C on it running a 14 X 6 prop. There wasn't enough left of the plane to be able to get any measurements, only enough to make some outlines and general assumptions. So far it's looking like the old plane, but I want to set these two parameters while I'm in the building process.
Thanks!
Ken
See thread here for reference; http://www.rcuniverse.com/forum/m_10804273/tm.htm
In the process of the rebuild and am wondering if it would be prudent to set the wing/horizontal stab incidence to 0 & 0. I plan on some right and down thrust and am thinking 1 & 1????
I guess I should say this is a 60 2C size plane and I had an Enya 90 4C on it running a 14 X 6 prop. There wasn't enough left of the plane to be able to get any measurements, only enough to make some outlines and general assumptions. So far it's looking like the old plane, but I want to set these two parameters while I'm in the building process.
Thanks!
Ken
11-14-2011 | 10:41 AM
#2
RE: Incedence and thrust angles.....
For this sort of model just go 0-0-0 and then include 1.0 to 1.5 degrees of right thrust to aid in counteracting torque effects. It's an aerobatic model after all. If it needs too much up trim following the new "first" flight which results in too strong a nose up pitch with added power then it is a sign that your CG is too far forward. Shift it back, retrim the elevator trim to compensate and you should find that the power on to power off trim change reduces. Shift the balance back in small steps with associated elevator trim changes until the plane is as pitch neutral as you can tolerate. By that time the model should be quite neutral and snap roll and do other such things cleanly. The 0-0-0 initial setup is prep for working the CG back in this manner.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the "sport" setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the "sport" setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
11-14-2011 | 05:13 PM
#3
Thread Starter
RE: Incedence and thrust angles.....
ORIGINAL: BMatthews
For this sort of model just go 0-0-0 and then include 1.0 to 1.5 degrees of right thrust to aid in counteracting torque effects. It's an aerobatic model after all. If it needs too much up trim following the new ''first'' flight which results in too strong a nose up pitch with added power then it is a sign that your CG is too far forward. Shift it back, retrim the elevator trim to compensate and you should find that the power on to power off trim change reduces. Shift the balance back in small steps with associated elevator trim changes until the plane is as pitch neutral as you can tolerate. By that time the model should be quite neutral and snap roll and do other such things cleanly. The 0-0-0 initial setup is prep for working the CG back in this manner.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the ''sport'' setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
For this sort of model just go 0-0-0 and then include 1.0 to 1.5 degrees of right thrust to aid in counteracting torque effects. It's an aerobatic model after all. If it needs too much up trim following the new ''first'' flight which results in too strong a nose up pitch with added power then it is a sign that your CG is too far forward. Shift it back, retrim the elevator trim to compensate and you should find that the power on to power off trim change reduces. Shift the balance back in small steps with associated elevator trim changes until the plane is as pitch neutral as you can tolerate. By that time the model should be quite neutral and snap roll and do other such things cleanly. The 0-0-0 initial setup is prep for working the CG back in this manner.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the ''sport'' setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
OK! Thanks for the info.
I'm kind of thinking this will be a basic IMAC machine. Even though there doesn't seem to be any IMAC competition in this area. I like the concept and this should "learn me" to do things in the correct manner. In the factory setup it was a bit of a "snappy cappy"
You had to be on your toes, so to speak. I only got about 10 flights out of it before the..... mishap.... So with the above said I'll try the 0-0-0 setup with 1.0 right thrust to start.
One last question. I know I've seen it someplace, but can't find it. I'm would like to know how to change a measurement into degrees. For setting the thrust angle of the firewall. Example, my fire wall is 5 inches wide. To get one degree of thrust change I need to set back one side XXXX inches.
Thanks!
Ken
11-14-2011 | 06:01 PM
#4
My Feedback: (29)
RE: Incedence and thrust angles.....
It is going to be difficult to get any model this size to do even the basic sequence well. There are a few things that will help. If you had to be on your toes at all then you were running too much throw. IMAC flying does not requre much surface throw at all. Go with about 12 degrees on elev, 25 on rudder and aileron, use a fair amount of expo. Set it up so it feels soft, if you are used to running excessive throw to the point of instability this will feel uncomfortable but practice and get used to it. As for setup, I agree with everything BMatt sayes except I suggest you run one degree positive in the wing, zero stab, zero down thrust and 3 degrees right. The positive in the wing will allow you to run the CG a little more forward. I would suggest starting at 30%.
Now for the really hard part, Get rid of any and all excess weight. This means lighter hardware, in some cases if you san shrten a screw do it. Look to your wheels, axles, tailwheel assy, batteries, fuel tank, servos. Basically anything you can replace with something lighter. I needed a CG shift on my pattern airplane, my fix was to replace a dozen of steel screws in the tail with aluminum screws so be creative. Dropping a pound out of that airplane will be the biggest performance gain you can do.
Now for the really hard part, Get rid of any and all excess weight. This means lighter hardware, in some cases if you san shrten a screw do it. Look to your wheels, axles, tailwheel assy, batteries, fuel tank, servos. Basically anything you can replace with something lighter. I needed a CG shift on my pattern airplane, my fix was to replace a dozen of steel screws in the tail with aluminum screws so be creative. Dropping a pound out of that airplane will be the biggest performance gain you can do.
11-14-2011 | 06:32 PM
#5
Thread Starter
RE: Incedence and thrust angles.....
I agree I had to much throw in the control surfaces. I've been out of the hobby for quite a while, (10 years or so). This is the first plane EVER, I used expo on. My next change was to reduce the throws and back off on the expo. While I was only running 35%, I felt it was to much. My change was to look for a more linear control throw feel. While it had the old snappy cappy feel to it, the plane never surprised me on landing and I made several touch and goes on each flight. I believe I had the CG very close to the correct point, but only 10 flights in I was just starting to get the feel for it and those changes were forth coming.
Weight reduction is in the process right now. The vertical fin is a chunk of 3/8 balsa, I've taken out anything I think I can get away with. The factory doublers were 3/32 ply with lightening holes. I'm using 1/16 ply with out holes. Maybe no weight saving, but IMO, stronger. I've also taken out some of the structure under and behind the firewall which added no strength, only weight and may have even weaken things a bit???
Vertical performance while not unlimited was more than enough. At an 80 degree angle it would climb out of sight.
Weight reduction is in the process right now. The vertical fin is a chunk of 3/8 balsa, I've taken out anything I think I can get away with. The factory doublers were 3/32 ply with lightening holes. I'm using 1/16 ply with out holes. Maybe no weight saving, but IMO, stronger. I've also taken out some of the structure under and behind the firewall which added no strength, only weight and may have even weaken things a bit???
Vertical performance while not unlimited was more than enough. At an 80 degree angle it would climb out of sight.
11-14-2011 | 06:43 PM
#6
RE: Incedence and thrust angles.....
If it was snappy before then it isn't going to be any better when repaired. An overly snappy model that surprises you with unwanted snaps strongly implies that the wing loading is too heavy. And all the repairs it's going to need are not going to help in that regard. If the plane was just plain vicous and it caught you off guard and snapped into the ground leaving you with a WTH look on your face then I think I'd suggest a nice warm bonfire with a "good riddance" glass of wine to toast its passing and move on to a better flying option. Really. We just can't fix "heavy".
What you're looking for is trigonomic tools. Lucky for you the Windows operating system comes with a Calculator program which has the trig functions in it. If you don't see the trig and other scientific functions then click on "View" and click on "scientific". To use it to find the offset dimension for a 5 inch firewall enter "1" then click on "sin". The resulting small value is then multiplied x5 to find the amount of set back to the right side for a 1 degree offset. As it happens it's .087 inch. Try it a few times to get familiar with the function.
What you're looking for is trigonomic tools. Lucky for you the Windows operating system comes with a Calculator program which has the trig functions in it. If you don't see the trig and other scientific functions then click on "View" and click on "scientific". To use it to find the offset dimension for a 5 inch firewall enter "1" then click on "sin". The resulting small value is then multiplied x5 to find the amount of set back to the right side for a 1 degree offset. As it happens it's .087 inch. Try it a few times to get familiar with the function.
11-14-2011 | 07:40 PM
#7
Thread Starter
RE: Incedence and thrust angles.....
ORIGINAL: BMatthews
If it was snappy before then it isn't going to be any better when repaired. An overly snappy model that surprises you with unwanted snaps strongly implies that the wing loading is too heavy. And all the repairs it's going to need are not going to help in that regard. If the plane was just plain vicous and it caught you off guard and snapped into the ground leaving you with a WTH look on your face then I think I'd suggest a nice warm bonfire with a ''good riddance'' glass of wine to toast its passing and move on to a better flying option. Really. We just can't fix ''heavy''.
What you're looking for is trigonomic tools. Lucky for you the Windows operating system comes with a Calculator program which has the trig functions in it. If you don't see the trig and other scientific functions then click on ''View'' and click on ''scientific''. To use it to find the offset dimension for a 5 inch firewall enter ''1'' then click on ''sin''. The resulting small value is then multiplied x5 to find the amount of set back to the right side for a 1 degree offset. As it happens it's .087 inch. Try it a few times to get familiar with the function.
If it was snappy before then it isn't going to be any better when repaired. An overly snappy model that surprises you with unwanted snaps strongly implies that the wing loading is too heavy. And all the repairs it's going to need are not going to help in that regard. If the plane was just plain vicous and it caught you off guard and snapped into the ground leaving you with a WTH look on your face then I think I'd suggest a nice warm bonfire with a ''good riddance'' glass of wine to toast its passing and move on to a better flying option. Really. We just can't fix ''heavy''.
What you're looking for is trigonomic tools. Lucky for you the Windows operating system comes with a Calculator program which has the trig functions in it. If you don't see the trig and other scientific functions then click on ''View'' and click on ''scientific''. To use it to find the offset dimension for a 5 inch firewall enter ''1'' then click on ''sin''. The resulting small value is then multiplied x5 to find the amount of set back to the right side for a 1 degree offset. As it happens it's .087 inch. Try it a few times to get familiar with the function.
While it was a bit snappy it is after all an aerobatic airplane
Like I said it never bit me unless I was stupid
. IIRC I think the all up weight was around 6 1/2 pounds. The rebuild is for the most part a scratch build so weight saving is fairly easy at this point. I've already eliminated some unneeded structure that was used in the ARF building process to make it easy to assemble the sub assemblies. I'll save a ton of weight in the wing by not having that huge box spar and 2X4 that held the wings together. Not to mention the 2 gallons of epoxy used in the wing joining process. The new wing will be a foam core sheeted and glassed. Stronger and lighter that the factory wing. I strongly believe the root cause of the demise was the elevators waving by-by at me on a high speed pass. The cause of this was weak factory balsa push rods. I knew better but it was all I had at the time and I wanted to fly the darn thing. Hadn't flown a plane in 10 years and HAD to get in the air. Thanks for the Windows trick. Oh, you miscalculated just a bit.... it's actually .087262032186417564097094892581581
And I can hold that tolerance with my wooden yard stick.........................
11-15-2011 | 05:52 PM
#8
RE: Incedence and thrust angles.....
ORIGINAL: kenh3497
.....Oh, you miscalculated just a bit.... it's actually .087262032186417564097094892581581 And I can hold that tolerance with my wooden yard stick.........................
.....Oh, you miscalculated just a bit.... it's actually .087262032186417564097094892581581
And I can hold that tolerance with my wooden yard stick.........................
YOU GO GUY! ! ! !
11-15-2011 | 07:11 PM
#9
Thread Starter
RE: Incedence and thrust angles.....
In the interest of lightness I'm hollowing out the back side of the triangle stock I'm using....every bit counts, especially at the back of the plane. I don't think tail heavy will be an issue as the original was not tail heavy. Never mind the hunk of iron hanging up front (Enya 90 4C). New tail fin will be a built up affair as will the horizontal stab. Both are near solid hunks of 3/8 balsa. All the tail parts will get an airfoil shape of some kind to help reduce weight and hopefully help reduce the tendency to flutter. They will also get sheeted to increase strength and I will gladly accept the small weight penalty. Don't bust me for this but everything will be glass and epoxy. Way back in my 1/4 Midget days I could build a plane (all wood), glass it, paint it and still come out under the minimum weight limit. I will be trying pull/pull on the rudder for the first time and I'm not sure what I'm doing on the elevators. The original had a single push rod (balsa) with a fork at the back for each elevator. I'm not fond of the setup but maybe it will be "good enough" with a carbon push rod.
Ken
Ken
11-16-2011 | 05:29 PM
#10
Thread Starter
RE: Incedence and thrust angles.....
I was just thinking....... HEY! Quiet in the peanut gallery!
I think the Windows calculator should be added to the "Aerodynamic Resources and Online Tools" thread. I've seen several people ask how to convert inches to angles and visa versa when setting control throws.
Ken
I think the Windows calculator should be added to the "Aerodynamic Resources and Online Tools" thread. I've seen several people ask how to convert inches to angles and visa versa when setting control throws.
Ken
11-17-2011 | 04:11 AM
#12
RE: Incedence and thrust angles.....
One suggestion is to borrow or check out from the library a Machinery's Handbook and copy the couple of illustrative pages it offers on using trig functions for triangle solutions. It has served as a welcome tool for a great many years. In conjunction with the windows calculator, you would then have both the formulas and the cruncher.
11-17-2011 | 04:25 AM
#13
RE: Incedence and thrust angles.....
ORIGINAL: BMatthews
For this sort of model just go 0-0-0 and then include 1.0 to 1.5 degrees of right thrust to aid in counteracting torque effects. It's an aerobatic model after all. If it needs too much up trim following the new ''first'' flight which results in too strong a nose up pitch with added power then it is a sign that your CG is too far forward. Shift it back, retrim the elevator trim to compensate and you should find that the power on to power off trim change reduces. Shift the balance back in small steps with associated elevator trim changes until the plane is as pitch neutral as you can tolerate. By that time the model should be quite neutral and snap roll and do other such things cleanly. The 0-0-0 initial setup is prep for working the CG back in this manner.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the ''sport'' setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
For this sort of model just go 0-0-0 and then include 1.0 to 1.5 degrees of right thrust to aid in counteracting torque effects. It's an aerobatic model after all. If it needs too much up trim following the new ''first'' flight which results in too strong a nose up pitch with added power then it is a sign that your CG is too far forward. Shift it back, retrim the elevator trim to compensate and you should find that the power on to power off trim change reduces. Shift the balance back in small steps with associated elevator trim changes until the plane is as pitch neutral as you can tolerate. By that time the model should be quite neutral and snap roll and do other such things cleanly. The 0-0-0 initial setup is prep for working the CG back in this manner.
If you don't want it to be that hard core than with the wing as the reference go with -2/0/-1 for engine downthrust/wing/stabilizer angles. The wing in this case being always zero because you're using the wing as the reference line inorder to avoid shape induced oddities with the fuselage. With this would be included 1.5 to 2 degrees of right thrust. This sort of setup would produce a good sport flying model but is not a good setup for extreme aerobatics or precision aerobatics where you want to get nice straight up and down lines and such things. The plane with such a setup would also end up with the CG set to be a little pitch stable rather than pitch neutral.
For the CG locations for each use one of the online CG calculators (links in the sticky thread at the top of the listings) to find the Neutral Point location and CG's for the stabilty values. For the 0-0-0 setup start at 5% stability and work things back until you're at or just a hair in front of the neutral point. For the ''sport'' setup I'd likely start with the CG at around 7% stability and work it back a little until you like it and the model seems to be happiest.
11-20-2011 | 09:16 AM
#14
Thread Starter
RE: Incedence and thrust angles.....
As I get older I get smarter....... Well at least I have a dream
I got to looking at the leftover pieces of the fuse and discovered I could measure from the tabs of the former in front of the wing, to the front of the firewall. The right side was set back .120 inch from the left side. If my new found math skills
are correct I have about 1 1/3 degrees of right thrust. I may be able to reconstruct enough of the fuse to determine the incidence of the wing. The horizontal stab lays on top of the fuse sides just above the thrust line, assuming there is no down thrust, which would give it zero degrees incidence.
IIRC, the box the plane came in says it could use a .46 to .55 2C engine or an .80ish 4C. With the Enya .90 I'm thinking slightly more right thrust may be in order so something like 2 degrees right???
Any thoughts on these numbers?
Ken
I got to looking at the leftover pieces of the fuse and discovered I could measure from the tabs of the former in front of the wing, to the front of the firewall. The right side was set back .120 inch from the left side. If my new found math skills
are correct I have about 1 1/3 degrees of right thrust. I may be able to reconstruct enough of the fuse to determine the incidence of the wing. The horizontal stab lays on top of the fuse sides just above the thrust line, assuming there is no down thrust, which would give it zero degrees incidence.IIRC, the box the plane came in says it could use a .46 to .55 2C engine or an .80ish 4C. With the Enya .90 I'm thinking slightly more right thrust may be in order so something like 2 degrees right???
Any thoughts on these numbers?
Ken
11-20-2011 | 11:21 AM
#15
My Feedback: (29)
RE: Incedence and thrust angles.....
The amount of right trust is influenced by the dia and pitch of your prop. As you go bigger you will need more. on my pylon racers I run zero degrees on my IMAC airplanes it ends up being between 3 and 3.5. On my electric 2M pattern airplane that runs a 20X15 prop, I am very close to 5 degrees. The test for this is easy but should be done after you get your CG nailed down. Pull into a vertical upline, you will need to get into the right rudder at the arc but once vertical, let off the rudder. An airplane the size of yours should continue 100 feet or so with no yaw deviation. If it does add right until it will do the 100 feet. Atfer that the speed falls and the rudder becomes less effective and torque takes over. Same for up or down thrust, if the airplane tucks, add up if it pulls, add down. Only after everything else is dialed in though. As for my models, I have never had to put in down thrust and on occasion have had to run a smidge of up.
11-20-2011 | 04:26 PM
#16
Thread Starter
RE: Incedence and thrust angles.....
I guess I'm just looking for a consensuses of where to start with this to minimize changes in the future. I know to get it right will take more than a few test flights. Also getting comfortable with the plane and knowing how it flies and responds to control inputs. I need to bite the bullet and make a decision on how much right thrust to set. That is the holdup right now in the build process. Decisions, Decisions, Decisions.[
] Trying to change the thrust angle later is such a PITA. No good way to do it.
Ken
] Trying to change the thrust angle later is such a PITA. No good way to do it.Ken
11-20-2011 | 04:37 PM
#17
My Feedback: (29)
RE: Incedence and thrust angles.....
It takes me about 50 flights to get an airplane really flying well. I will get it about 85% there on the bench before the maiden. When I start making changes I fly with that change for a bit before making a decision if it was a good or bad change. For your setup, I would start with 2.5 to 3 degrees. If that gets you close you can fine tune with a throttle/rudder mix. The only issue with that is one would have to have good throttle management. If you have a habit of being at either idle or full throttle when you fly then the mix won't wotk as well.
11-20-2011 | 05:25 PM
#18
Thread Starter
RE: Incedence and thrust angles.....
OK I found the build instructions for the plane. engine size is from a 40 2C to a 72 4C. With my 90 4C, I'm going to set the thrust at 2.5. I was going to chicken out and set it at 2, but decided if it flies on a 40 at 1 1/4 degrees, 2.5 should be good on the 90 4C. That converts to .218 or 7/32 setback on the right side on a 5 inch wide firewall. It looks like a god awful amount of off-set. I can double check it with a roofing square that has degrees marked on it. I still might chicken out and set it to 2 1/4
Thanks for all the help and encouragement!
Ken
Thanks for all the help and encouragement!
Ken
