FEJ F18 1/6 OWNERS BUILD THREAD
03-21-2010, 03:38 AM
#28
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
But things were not really easy with this plane.....
The CG of this plane as anounced by FEJ is WRONG
220mm is tail heavy. I'm not sure if the plane with SLATS have the same CG as the ones without.
And this plane has SLATS. After long long trys the owner ended up.....
THE CORRECT CG IS 180mm FROM THE FRONT TIP OF THE WING WITHOUT THE REAR LEFT AND RIGHT TANKS
Please beware of your set up
Tassos
The CG of this plane as anounced by FEJ is WRONG
220mm is tail heavy. I'm not sure if the plane with SLATS have the same CG as the ones without.
And this plane has SLATS. After long long trys the owner ended up.....
THE CORRECT CG IS 180mm FROM THE FRONT TIP OF THE WING WITHOUT THE REAR LEFT AND RIGHT TANKS
Please beware of your set up
Tassos
03-21-2010, 03:56 PM
#29
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
Other findings except incorect CG
1) The wing skins need more reinforcment. Especially the outer flap servo deflects so much that the whole flap moves up and down about 10mm
Of course as you can see in the pics we reinforced the wing with carbon fiber but that was not enough. Today we installed and glued reinforcment wooden strips 4mm thick and about 250mm x 50mm on the top skin on the left and right of the servo boxes. I think it should be fine now.
2) The stab axis is not straight looking at the plane from the rear. It looks like that the servo frames for the stabs are not glued in straight in the mold. Perhaps the bearing axis are not straight. I'm not sure how to explain this but the axis of the stab is not parallel to the wings looking from the back. However we will investigate further to see how this could be fixed.
3) As Oliver has repeatedly pointed out the wheels are not as wide as the real thing. This is causing unwanted tilting left or right while fast taxying or landing. We have solved this problem partially by replacing the stock springs inside the oleos. This means that the plane sits lower at the back thus bringing the CG closer to the ground (not much but enough to avoid too much tilting). This also gives a positive AOA to the plane while taking off thus making the plane taking off easier.
4) While flying there is a tendency for the plane to roll right. In order to trim there was a considerable amount of left trim set on the radio. We are not sure why this could be. The slats and flaps are perfect. The wings incidence is the same on the left and right wing. The stab incidence is the same for both left and right stabs. Perhaps it is because of 2. We will investigate.
We have another suspicion why this is but would not like to speculate at the moment only try to get the facts.
5) Finally the mechanics of the stabs don't seem very solid. Perhaps Oliver could comment. My idea is that the half arms are eliminated from the servos and instead double arms are used with new rods and ball links. There is some flex there but we think we can fix it.
Other than that the plane is really big and it creates pure awe when it passes by you. There are a lot of clever ideas and details in this plane which seems that FEJ has done a great job on.
The plane will fly again pretty soon and we'll let you know of our findings.
Tassos
1) The wing skins need more reinforcment. Especially the outer flap servo deflects so much that the whole flap moves up and down about 10mm
Of course as you can see in the pics we reinforced the wing with carbon fiber but that was not enough. Today we installed and glued reinforcment wooden strips 4mm thick and about 250mm x 50mm on the top skin on the left and right of the servo boxes. I think it should be fine now.
2) The stab axis is not straight looking at the plane from the rear. It looks like that the servo frames for the stabs are not glued in straight in the mold. Perhaps the bearing axis are not straight. I'm not sure how to explain this but the axis of the stab is not parallel to the wings looking from the back. However we will investigate further to see how this could be fixed.
3) As Oliver has repeatedly pointed out the wheels are not as wide as the real thing. This is causing unwanted tilting left or right while fast taxying or landing. We have solved this problem partially by replacing the stock springs inside the oleos. This means that the plane sits lower at the back thus bringing the CG closer to the ground (not much but enough to avoid too much tilting). This also gives a positive AOA to the plane while taking off thus making the plane taking off easier.
4) While flying there is a tendency for the plane to roll right. In order to trim there was a considerable amount of left trim set on the radio. We are not sure why this could be. The slats and flaps are perfect. The wings incidence is the same on the left and right wing. The stab incidence is the same for both left and right stabs. Perhaps it is because of 2. We will investigate.
We have another suspicion why this is but would not like to speculate at the moment only try to get the facts.
5) Finally the mechanics of the stabs don't seem very solid. Perhaps Oliver could comment. My idea is that the half arms are eliminated from the servos and instead double arms are used with new rods and ball links. There is some flex there but we think we can fix it.
Other than that the plane is really big and it creates pure awe when it passes by you. There are a lot of clever ideas and details in this plane which seems that FEJ has done a great job on.
The plane will fly again pretty soon and we'll let you know of our findings.
Tassos
03-21-2010, 04:09 PM
#30
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RE: FEJ F18 1/6 OWNERS BUILD THREAD
Ho Tassos...
Amazing airplane...
My friend Raul Lozano have one too... hope see that planes flying soon.
João Matos
[link]http://joaomatosjets.blogspot.com[/link]
Amazing airplane...
My friend Raul Lozano have one too... hope see that planes flying soon.
João Matos
[link]http://joaomatosjets.blogspot.com[/link]
03-21-2010, 05:51 PM
#32
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: tassos p
Other findings except incorect CG
1) The wing skins need more reinforcment. Especially the outer flap servo deflects so much that the whole flap moves up and down about 10mm
Of course as you can see in the pics we reinforced the wing with carbon fiber but that was not enough. Today we installed and glued reinforcment wooden strips 4mm thick and about 250mm x 50mm on the top skin on the left and right of the servo boxes. I think it should be fine now.
2) The stab axis is not straight looking at the plane from the rear. It looks like that the servo frames for the stabs are not glued in straight in the mold. Perhaps the bearing axis are not straight. I'm not sure how to explain this but the axis of the stab is not parallel to the wings looking from the back. However we will investigate further to see how this could be fixed.
3) As Oliver has repeatedly pointed out the wheels are not as wide as the real thing. This is causing unwanted tilting left or right while fast taxying or landing. We have solved this problem partially by replacing the stock springs inside the oleos. This means that the plane sits lower at the back thus bringing the CG closer to the ground (not much but enough to avoid too much tilting). This also gives a positive AOA to the plane while taking off thus making the plane taking off easier.
4) While flying there is a tendency for the plane to roll right. In order to trim there was a considerable amount of left trim set on the radio. We are not sure why this could be. The slats and flaps are perfect. The wings incidence is the same on the left and right wing. The stab incidence is the same for both left and right stabs. Perhaps it is because of 2. We will investigate.
We have another suspicion why this is but would not like to speculate at the moment only try to get the facts.
5) Finally the mechanics of the stabs don't seem very solid. Perhaps Oliver could comment. My idea is that the half arms are eliminated from the servos and instead double arms are used with new rods and ball links. There is some flex there but we think we can fix it.
Other than that the plane is really big and it creates pure awe when it passes by you. There are a lot of clever ideas and details in this plane which seems that FEJ has done a great job on.
The plane will fly again pretty soon and we'll let you know of our findings.
Tassos
Other findings except incorect CG
1) The wing skins need more reinforcment. Especially the outer flap servo deflects so much that the whole flap moves up and down about 10mm
Of course as you can see in the pics we reinforced the wing with carbon fiber but that was not enough. Today we installed and glued reinforcment wooden strips 4mm thick and about 250mm x 50mm on the top skin on the left and right of the servo boxes. I think it should be fine now.
2) The stab axis is not straight looking at the plane from the rear. It looks like that the servo frames for the stabs are not glued in straight in the mold. Perhaps the bearing axis are not straight. I'm not sure how to explain this but the axis of the stab is not parallel to the wings looking from the back. However we will investigate further to see how this could be fixed.
3) As Oliver has repeatedly pointed out the wheels are not as wide as the real thing. This is causing unwanted tilting left or right while fast taxying or landing. We have solved this problem partially by replacing the stock springs inside the oleos. This means that the plane sits lower at the back thus bringing the CG closer to the ground (not much but enough to avoid too much tilting). This also gives a positive AOA to the plane while taking off thus making the plane taking off easier.
4) While flying there is a tendency for the plane to roll right. In order to trim there was a considerable amount of left trim set on the radio. We are not sure why this could be. The slats and flaps are perfect. The wings incidence is the same on the left and right wing. The stab incidence is the same for both left and right stabs. Perhaps it is because of 2. We will investigate.
We have another suspicion why this is but would not like to speculate at the moment only try to get the facts.
5) Finally the mechanics of the stabs don't seem very solid. Perhaps Oliver could comment. My idea is that the half arms are eliminated from the servos and instead double arms are used with new rods and ball links. There is some flex there but we think we can fix it.
Other than that the plane is really big and it creates pure awe when it passes by you. There are a lot of clever ideas and details in this plane which seems that FEJ has done a great job on.
The plane will fly again pretty soon and we'll let you know of our findings.
Tassos
Hi Tassos,
Congratulations to the builder(s) and pilot !
1) The 1/7 th scale F-18F had the same problem. And I recommended to fit balsa boxes around the servo bay to stiffen the wing around. What you have seen for the flap is the tremendous hinging momentum exerted by this huge flight control. Once again, 4 Chinese quality hinges are not enough to cope with the 1000 oz-in hinging momentum generated in flight. If you want to keep this beautiful plane for a long time, I'd strongly recommend you to take a 3,5 mm drill, cut all the hinges with it and re-fit 6 hi quality Robart point hinges per flap.
2) From looking at the picture below I would guess that the left aluminium tray is screwed at the wrong angle (too much anhedral )
To be compared with this one and the real one ( the elevator should be nearly flat ):
3) The only answer to the gear stance problem is to rework the cinematics. Looking at the gear bay pictures, you should be able to tilt the gear outward by 20 degrees. Just initially try it by placing wood blocks as I did for mine. Only when you are sure about the cinematics, you can rework the gear brackets.
Then putting a shorter and stronger main spring will reduce the wobbling effect of the FEJ setup.
4) The answer here is very clear: the left elevator has about 5 degrees more angle of attack than the right one. This gives you the unwanted roll effect.
Have a look here:
Setting the stabilators with an incidence meter as well as visually is essential on these planes.
5) The flex is not a problem if the pivot point is set at 17% MAC. This is essential and if you give me the dimensions of the stabilators as well as the position of the pivot point, I could verify it.
Regarding the pivot mechanism, and as I said before, I find them undersized on this plane. Moreover, the 4 screws fixing the mechanism at the back of the pivot and placed to narrowly. Since you will have to redrill and refix both sides ( the right elevator has a bit too much anhedral as well ), I would consider reinforcing the screws area with a large 2 mm carbon fiber plate glued with slow epoxy the rear former.
Also one thing I find looking a bit strange is the very thin gear. The real F-18F gear is massive:
03-22-2010, 01:22 AM
#34
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: AndyAndrews
How much was the basic kit?
How much was the basic kit?
Tassos
03-22-2010, 01:27 AM
#35
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: jetspud
Looks great,
How did the P-200 push this massive beast around.. I am glad you got you maiden down and past you..
David
Looks great,
How did the P-200 push this massive beast around.. I am glad you got you maiden down and past you..
David
Gentle flying is the way to go here.
Tassos
03-22-2010, 01:31 AM
#36
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: tassos p
Not easily, max climb rate is at around 45-50 degrees. This is a new P200SX in this plane but the plane for sure lacks power. However for the type of flying this plane was bought for ie slow scale flying it is perfect. This plane cannot reach 200mph. It is massive and so will be the forces on it.
Gentle flying is the way to go here.
Tassos
ORIGINAL: jetspud
Looks great,
How did the P-200 push this massive beast around.. I am glad you got you maiden down and past you..
David
Looks great,
How did the P-200 push this massive beast around.. I am glad you got you maiden down and past you..
David
Gentle flying is the way to go here.
Tassos
Yes and don't enter the drag curve too much because you'd need 300 N of thrust to get out of it !
03-22-2010, 01:41 AM
#37
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: olnico
Hi Tassos,
Congratulations to the builder(s) and pilot !
1) The 1/7 th scale F-18F had the same problem. And I recommended to fit balsa boxes around the servo bay to stiffen the wing around. What you have seen for the flap is the tremendous hinging momentum exerted by this huge flight control. Once again, 4 Chinese quality hinges are not enough to cope with the 1000 oz-in hinging momentum generated in flight. If you want to keep this beautiful plane for a long time, I'd strongly recommend you to take a 3,5 mm drill, cut all the hinges with it and re-fit 6 hi quality Robart point hinges per flap.
2) From looking at the picture below I would guess that the left aluminium tray is screwed at the wrong angle (too much anhedral )
To be compared with this one and the real one ( the elevator should be nearly flat ):
3) The only answer to the gear stance problem is to rework the cinematics. Looking at the gear bay pictures, you should be able to tilt the gear outward by 20 degrees. Just initially try it by placing wood blocks as I did for mine. Only when you are sure about the cinematics, you can rework the gear brackets.
Then putting a shorter and stronger main spring will reduce the wobbling effect of the FEJ setup.
4) The answer here is very clear: the left elevator has about 5 degrees more angle of attack than the right one. This gives you the unwanted roll effect.
Have a look here:
Setting the stabilators with an incidence meter as well as visually is essential on these planes.
5) The flex is not a problem if the pivot point is set at 17% MAC. This is essential and if you give me the dimensions of the stabilators as well as the position of the pivot point, I could verify it.
Regarding the pivot mechanism, and as I said before, I find them undersized on this plane. Moreover, the 4 screws fixing the mechanism at the back of the pivot and placed to narrowly. Since you will have to redrill and refix both sides ( the right elevator has a bit too much anhedral as well ), I would consider reinforcing the screws area with a large 2 mm carbon fiber plate glued with slow epoxy the rear former.
Also one thing I find looking a bit strange is the very thin gear. The real F-18F gear is massive:
Hi Tassos,
Congratulations to the builder(s) and pilot !
1) The 1/7 th scale F-18F had the same problem. And I recommended to fit balsa boxes around the servo bay to stiffen the wing around. What you have seen for the flap is the tremendous hinging momentum exerted by this huge flight control. Once again, 4 Chinese quality hinges are not enough to cope with the 1000 oz-in hinging momentum generated in flight. If you want to keep this beautiful plane for a long time, I'd strongly recommend you to take a 3,5 mm drill, cut all the hinges with it and re-fit 6 hi quality Robart point hinges per flap.
2) From looking at the picture below I would guess that the left aluminium tray is screwed at the wrong angle (too much anhedral )
To be compared with this one and the real one ( the elevator should be nearly flat ):
3) The only answer to the gear stance problem is to rework the cinematics. Looking at the gear bay pictures, you should be able to tilt the gear outward by 20 degrees. Just initially try it by placing wood blocks as I did for mine. Only when you are sure about the cinematics, you can rework the gear brackets.
Then putting a shorter and stronger main spring will reduce the wobbling effect of the FEJ setup.
4) The answer here is very clear: the left elevator has about 5 degrees more angle of attack than the right one. This gives you the unwanted roll effect.
Have a look here:
Setting the stabilators with an incidence meter as well as visually is essential on these planes.
5) The flex is not a problem if the pivot point is set at 17% MAC. This is essential and if you give me the dimensions of the stabilators as well as the position of the pivot point, I could verify it.
Regarding the pivot mechanism, and as I said before, I find them undersized on this plane. Moreover, the 4 screws fixing the mechanism at the back of the pivot and placed to narrowly. Since you will have to redrill and refix both sides ( the right elevator has a bit too much anhedral as well ), I would consider reinforcing the screws area with a large 2 mm carbon fiber plate glued with slow epoxy the rear former.
Also one thing I find looking a bit strange is the very thin gear. The real F-18F gear is massive:
2) Correct, this indicates wrong wood placement inside. I think we're going to redrill the holes to get it right.
3) Reworking the kinematics is not an easy job. The problem are that the gear doors don't allow it perhaps only if we remove them. But I guess all the model F-18s have this problem, even TAM's F-18. I'm not sure about the Yellow F-18. There was definetely an improvement with the softer springs
4) This was done on purpose to act as an aileron. There's something else not right with the plane. Perhaps it is the wrong dihedral. We're trying to figure out. Wing incidence seems right.
5) We'll try to get that data to you. For sure the stabs are not parallel to the wings.
Thanks alot,
Tassos
03-27-2010, 05:55 PM
#38
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
Well Oliver,
Here it is, the calculations on the aileron and flaps for the plane.
For the aileron was easy. For the flap I assumed 2 seperate flap surface with 1 servo per flap.
For the aileron and a max speed of 180mph the servo max torque is 352 oz-in. The servo used on the ail is 400 oz-in
For the flaps at max speed of 90mph (more than enough) and max deflection of 17 degrees (as per instructions) max torque 366 oz-in and 209 oz-in torque on 2 hinges. Do you think this is critical?
Thanks,
Tassos
Here it is, the calculations on the aileron and flaps for the plane.
For the aileron was easy. For the flap I assumed 2 seperate flap surface with 1 servo per flap.
For the aileron and a max speed of 180mph the servo max torque is 352 oz-in. The servo used on the ail is 400 oz-in
For the flaps at max speed of 90mph (more than enough) and max deflection of 17 degrees (as per instructions) max torque 366 oz-in and 209 oz-in torque on 2 hinges. Do you think this is critical?
Thanks,
Tassos
03-28-2010, 03:30 AM
#39
RE: FEJ F18 1/6 OWNERS BUILD THREAD
Hi Tassos, the Chinese hinges cannot support more than 100 oz-in.
So if you stay at max 17 degrees you'll be fine.
However your computations look a bit weird to me.
Do you use only +-15 degrees ( Rs+, Rs-) on the servos ( out of the +-60 degrees available ) ?
Similarly do you use only 0 to 10 degrees out of the 120 degrees available for the flap servos ?
If this is the case then the setup is very wrong.
So if you stay at max 17 degrees you'll be fine.
However your computations look a bit weird to me.
Do you use only +-15 degrees ( Rs+, Rs-) on the servos ( out of the +-60 degrees available ) ?
Similarly do you use only 0 to 10 degrees out of the 120 degrees available for the flap servos ?
If this is the case then the setup is very wrong.
03-28-2010, 04:16 AM
#40
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: olnico
Hi Tassos, the Chinese hinges cannot support more than 100 oz-in.
So if you stay at max 17 degrees you'll be fine.
However your computations look a bit weird to me.
Do you use only +-15 degrees ( Rs+, Rs-) on the servos ( out of the +-60 degrees available ) ?
Similarly do you use only 0 to 10 degrees out of the 120 degrees available for the flap servos ?
If this is the case then the setup is very wrong.
Hi Tassos, the Chinese hinges cannot support more than 100 oz-in.
So if you stay at max 17 degrees you'll be fine.
However your computations look a bit weird to me.
Do you use only +-15 degrees ( Rs+, Rs-) on the servos ( out of the +-60 degrees available ) ?
Similarly do you use only 0 to 10 degrees out of the 120 degrees available for the flap servos ?
If this is the case then the setup is very wrong.
Thanks alot,
Well I have not really measured the angles but indeed calculated this based on the servo horn hole positioning for each servo as I measured it. I mean for example on the flap inner servo I measured a 4cm length between the servo axis and the servo horn ball link distance. I know this is output data from the RC calculator but I think this is closer to the reallity (I mean the measured distances are the same as the RC calc output data distances). Maybe I'm doing something wrong. I got the new RCJI that you have an article on this but haven't had the time to read through it yet.
Now you also asked for the stab dimensions and I measured them and here they are for you to check.
Thanks alot for your help.
Regards,
Tassos
03-28-2010, 11:23 AM
#41
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: tassos p
I mean for example on the flap inner servo I measured a 4cm length between the servo axis and the servo horn ball link distance. I know this is output data from the RC calculator but I think this is closer to the reallity.
Tassos
I mean for example on the flap inner servo I measured a 4cm length between the servo axis and the servo horn ball link distance. I know this is output data from the RC calculator but I think this is closer to the reallity.
Tassos
This setup is COMPLETELY wrong.
You must tell the owner that he has to change it or he'll end up with a catastrophe.
In this case the mechanical advantage principle is inverted and becomes mechanical disadvantage.
He's actually dividing the servo torque by two with this setup.
This is exactly the purpose of my different RCU threads and article in RCJI: help people in avoiding such mistakes.
The manufacturers are partly responsible for this mess in that they encourage people in putting long servo arm through the servo hatch with external linkages.
THIS IS WRONG.
Have a look at the new RCJI page 59. You'll see how Collin did modify his big F-86 aileron system to avoid this problem.
This is the perfect setup and what I recommend as well. Put the ball link as close as possible to the axis on the servo arm. Invert the arm to get through the surface skin as close from the control horn as possible. Get a strong double control horn.
Here is my setup on the F-18F:
03-28-2010, 11:42 AM
#42
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: olnico
Hi Tassos.
This setup is COMPLETELY wrong.
You must tell the owner that he has to change it or he'll end up with a catastrophe.
In this case the mechanical advantage principle is inverted and becomes mechanical disadvantage.
He's actually dividing the servo torque by two with this setup.
This is exactly the purpose of my different RCU threads and article in RCJI: help people in avoiding such mistakes.
The manufacturers are partly responsible for this mess in that they encourage people in putting long servo arm through the servo hatch with external linkages.
THIS IS WRONG.
Have a look at the new RCJI page 59. You'll see how Collin did modify his big F-86 aileron system to avoid this problem.
This is the perfect setup and what I recommend as well. Put the ball link as close as possible to the axis on the servo arm. Invert the arm to get through the surface skin as close from the control horn as possible. Get a strong double control horn.
Here is my setup on the F-18F:
ORIGINAL: tassos p
I mean for example on the flap inner servo I measured a 4cm length between the servo axis and the servo horn ball link distance. I know this is output data from the RC calculator but I think this is closer to the reallity.
Tassos
I mean for example on the flap inner servo I measured a 4cm length between the servo axis and the servo horn ball link distance. I know this is output data from the RC calculator but I think this is closer to the reallity.
Tassos
This setup is COMPLETELY wrong.
You must tell the owner that he has to change it or he'll end up with a catastrophe.
In this case the mechanical advantage principle is inverted and becomes mechanical disadvantage.
He's actually dividing the servo torque by two with this setup.
This is exactly the purpose of my different RCU threads and article in RCJI: help people in avoiding such mistakes.
The manufacturers are partly responsible for this mess in that they encourage people in putting long servo arm through the servo hatch with external linkages.
THIS IS WRONG.
Have a look at the new RCJI page 59. You'll see how Collin did modify his big F-86 aileron system to avoid this problem.
This is the perfect setup and what I recommend as well. Put the ball link as close as possible to the axis on the servo arm. Invert the arm to get through the surface skin as close from the control horn as possible. Get a strong double control horn.
Here is my setup on the F-18F:
For sure the owner wont be very happy for this but I think you're very right.
On post #15 you could see that in all the wing servos the outer hole of the servo arm was used. Surely the owner (PETROS) won't be very happy of this. New work for easter vacation!!!
Thanks alot for your invaluable help. I will also re-check on my jets the servo arms!
What do you think of the stab?
Tassos
03-28-2010, 01:50 PM
#43
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RE: FEJ F18 1/6 OWNERS BUILD THREAD
Olivier,
I have mentioned many times in the F86 build thread that extra trim tabs needed to be glued onto the wooden servo boxes. This raises the servo to its highest point so that the Fiberglass cover just about lays on the servo. At this orientation, the metel servo arm is protruding to the max out of the slot on the servo fiberglass cover. From this the metel ball link clevis should be attached to the lowest hole possible giving the needed movement of that surface. As you stated, the max torque and stability is now being used from the servo. Using the hole at the outer most distance from the center of the servo arm, is the absolute weakest use of torque.
This is so important, and should be shown, stated, and driven into anyone who is building a jet from any manufacturer.
Thanks Olivier for pointing this outagain.
Kevin
I have mentioned many times in the F86 build thread that extra trim tabs needed to be glued onto the wooden servo boxes. This raises the servo to its highest point so that the Fiberglass cover just about lays on the servo. At this orientation, the metel servo arm is protruding to the max out of the slot on the servo fiberglass cover. From this the metel ball link clevis should be attached to the lowest hole possible giving the needed movement of that surface. As you stated, the max torque and stability is now being used from the servo. Using the hole at the outer most distance from the center of the servo arm, is the absolute weakest use of torque.
This is so important, and should be shown, stated, and driven into anyone who is building a jet from any manufacturer.
Thanks Olivier for pointing this outagain.
Kevin
03-28-2010, 04:16 PM
#44
RE: FEJ F18 1/6 OWNERS BUILD THREAD
You're welcome Kevin.
Also using a platic servo mount on a 8711 loaded to 320 oz-in is really critical:
You guys will have to change completely this setup if you want to get this plane fly long...
For the stab computation, I need the total root length, total tip length and distance of sweep at the tip leading edge. I cannot compute anything with what you have given to me Tassos.
Also using a platic servo mount on a 8711 loaded to 320 oz-in is really critical:
You guys will have to change completely this setup if you want to get this plane fly long...
For the stab computation, I need the total root length, total tip length and distance of sweep at the tip leading edge. I cannot compute anything with what you have given to me Tassos.
05-07-2010, 01:11 AM
#45
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RE: FEJ F18 1/6 OWNERS BUILD THREAD
Hello Tassos,
I am getting ready to maiden my FEJ 1/6 F18 with the front leading Slats/Flaps and would like any information you have learned from flying yours.
Please give insite to how Jet handles when front slats are put down, does jet pitch up, down or stay level. How mant degres do you use for take off and landing.
When the CG was at the 220mm mark, did you invert plane at 45 degree angle and see if it continues on that plane, or the elevator was just too sensative.
What is the total travel of elevator at mid rates, at the flying set up. Also what was the take off distance. Lastly what was approx weight.
Thanks Tassos for your insite and help. Also please tell me the problem in the severe right tilt the jet wanted to fly at, what should I watch out for.
Take Care.
Kevin
I am getting ready to maiden my FEJ 1/6 F18 with the front leading Slats/Flaps and would like any information you have learned from flying yours.
Please give insite to how Jet handles when front slats are put down, does jet pitch up, down or stay level. How mant degres do you use for take off and landing.
When the CG was at the 220mm mark, did you invert plane at 45 degree angle and see if it continues on that plane, or the elevator was just too sensative.
What is the total travel of elevator at mid rates, at the flying set up. Also what was the take off distance. Lastly what was approx weight.
Thanks Tassos for your insite and help. Also please tell me the problem in the severe right tilt the jet wanted to fly at, what should I watch out for.
Take Care.
Kevin
05-07-2010, 02:17 PM
#46
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: Kmarks
Hello Tassos,
I am getting ready to maiden my FEJ 1/6 F18 with the front leading Slats/Flaps and would like any information you have learned from flying yours.
Please give insite to how Jet handles when front slats are put down, does jet pitch up, down or stay level. How mant degres do you use for take off and landing.
When the CG was at the 220mm mark, did you invert plane at 45 degree angle and see if it continues on that plane, or the elevator was just too sensative.
What is the total travel of elevator at mid rates, at the flying set up. Also what was the take off distance. Lastly what was approx weight.
Thanks Tassos for your insite and help. Also please tell me the problem in the severe right tilt the jet wanted to fly at, what should I watch out for.
Take Care.
Kevin
Hello Tassos,
I am getting ready to maiden my FEJ 1/6 F18 with the front leading Slats/Flaps and would like any information you have learned from flying yours.
Please give insite to how Jet handles when front slats are put down, does jet pitch up, down or stay level. How mant degres do you use for take off and landing.
When the CG was at the 220mm mark, did you invert plane at 45 degree angle and see if it continues on that plane, or the elevator was just too sensative.
What is the total travel of elevator at mid rates, at the flying set up. Also what was the take off distance. Lastly what was approx weight.
Thanks Tassos for your insite and help. Also please tell me the problem in the severe right tilt the jet wanted to fly at, what should I watch out for.
Take Care.
Kevin
Good to hear you got the plane. Lets sum up the serious points we encountered.
1) CG at 180mm should be the right one. I think the slats/flaps mould is different than the fixed wing mold. You can see this in the openings compared to the plane of Raul Lozzano (previous post on this thread) and different to the twin engine mould. This is the only way I could explain why the plane settles with the CG set at 180mm. No the owner did not fly the plane at 45 degrees inverted. The plane could not land unless a fair amount of down elevator was applied (it was pitching up). I was not the pilot of the plane but the pilot was surely frightned while landing. Now the plane flies like a piper-cub!!!! REALLY
The ballast required was around 1.5 pounds in the nose and the stabs although the were ballanced the weight was removed in order to achieve the 180mm CG.
2) The owner of the plane has set 3 conditions on the radio. Condition #1 > normal flight with flaps and slats retracted. Condition #2 > slats fully down and flaps at take off position (as per instructions). Condition #3 > slats fully down and flaps fully down as per instructions. I'm not sure at this point to give you the exact slat deflection in mm but we did it up to the point that the wing skin starts to deform. If you pull too much the slat link the top wing skin deforms.
3) Stab travel as per instructions with 60% expo
4) Take off distance is quite short. You can see in the video on this post. Around 100m (300ft). The plane really flies like a CUB if you set it correctly.
5) Only the 2 middle tanks were used and not the saddle tanks. The weight we did not measure. But I would guess around 27kg (60 pounds) with 6 litrs of fuel. With P200 at full throttle the speed is not that high. Basically the plane could not climb at a higher rate than 45 degrees angle upwards. Its surely underpowered with the P200.
6) You should strengthen the wing skin of the flap servos and insert ribs (this was also Lowell's idea). The wing skin really bends if not strengthened with ribs and/or carbon fibre.
7) Finally for the severe right tilt I would suggest you to look at the plane from the front. I think the mold is not straight at all and I'm not happy to report this. Maybe yours is in better condition. The plane we have here is not straight from the mould. This was ofcourse corrected with the elevon trim.
8) I'd suggest you to change also the stock main strut srpings with softer ones (or shorter ones). This really helps on the ground handling.
Other than these issues the plane is a reall beauty in the air and it is really scary because of its size when you make low fly by's. It is a really slow plane easy to fly (if you correct the pitchy attitude caused by the wrong CG). We think that a 70 pound engine thrust would surely fly the plane faster.
No other issues noticed. For sure a GREAT value for money airplane.
Looking forward for your observations.
Tassos
05-08-2010, 12:39 AM
#47
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RE: FEJ F18 1/6 OWNERS BUILD THREAD
Thanks Tassos,
I will post full report by next week, still waiting for EV5 air unit. After that and a few more tweeks, she is ready.
I did infact have new lower struts made and reconfigured the springs. Please measure the distance from outer edge of tire to out edge of tire. I want to compare If in fact I have a greater wheel base.
Thanks for the info and I will set CG to 180 or so for maiden.
Best Regards
Kevin
I will post full report by next week, still waiting for EV5 air unit. After that and a few more tweeks, she is ready.
I did infact have new lower struts made and reconfigured the springs. Please measure the distance from outer edge of tire to out edge of tire. I want to compare If in fact I have a greater wheel base.
Thanks for the info and I will set CG to 180 or so for maiden.
Best Regards
Kevin
05-10-2010, 10:22 AM
#48
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RE: FEJ F18 1/6 OWNERS BUILD THREAD
Hello Tassos,
Last night I was working on the elevators, and noticed something ever so slight. The scribe line on the right side of fuse is NOT at the same distance on the fuse as the left side. I have always centered my elevators to some sort of scribe line to make sure they are set properly. The scribe line on the right is lower then the left. Causing greater bite, and a yaw to the right.
I used only one side for measuring purposes, then with the TX stick leveled the stab by using a T level. I then shut off the transmitter leaving the elevator at that nuetral position and then adjust the other side to level again using the leveler. I think this may have caused your right side yaw effect. Check your elevators and let me know.
Kevin
Last night I was working on the elevators, and noticed something ever so slight. The scribe line on the right side of fuse is NOT at the same distance on the fuse as the left side. I have always centered my elevators to some sort of scribe line to make sure they are set properly. The scribe line on the right is lower then the left. Causing greater bite, and a yaw to the right.
I used only one side for measuring purposes, then with the TX stick leveled the stab by using a T level. I then shut off the transmitter leaving the elevator at that nuetral position and then adjust the other side to level again using the leveler. I think this may have caused your right side yaw effect. Check your elevators and let me know.
Kevin
05-10-2010, 10:33 AM
#49
Thread Starter
RE: FEJ F18 1/6 OWNERS BUILD THREAD
ORIGINAL: Kmarks
Hello Tassos,
Last night I was working on the elevators, and noticed something ever so slight. The scribe line on the right side of fuse is NOT at the same distance on the fuse as the left side. I have always centered my elevators to some sort of scribe line to make sure they are set properly. The scribe line on the right is lower then the left. Causing greater bite, and a yaw to the right.
I used only one side for measuring purposes, then with the TX stick leveled the stab by using a T level. I then shut off the transmitter leaving the elevator at that nuetral position and then adjust the other side to level again using the leveler. I think this may have caused your right side yaw effect. Check your elevators and let me know.
Kevin
Hello Tassos,
Last night I was working on the elevators, and noticed something ever so slight. The scribe line on the right side of fuse is NOT at the same distance on the fuse as the left side. I have always centered my elevators to some sort of scribe line to make sure they are set properly. The scribe line on the right is lower then the left. Causing greater bite, and a yaw to the right.
I used only one side for measuring purposes, then with the TX stick leveled the stab by using a T level. I then shut off the transmitter leaving the elevator at that nuetral position and then adjust the other side to level again using the leveler. I think this may have caused your right side yaw effect. Check your elevators and let me know.
Kevin
In any case the left side panel lines are not the same as the right side so you're right you need to be a little bit carefull there.
Are you going to use elevon set up? We did not use elevons and made our lifes a little bit more difficult. If you use this setup then you can trim the plane during flight.
We did it by trial and error method and we got it right in the end!!
Tassos
