Anhedral stab setup
09-19-2007, 05:20 PM
#1
Anhedral stab setup
I am looking for any tricks to assure that both elevators in an anhedral stab setup travel equally. In a flat stab setup I use 1/8 inch carbon fiber rods about 15" long atttached to each elevator half and meeting behind the rudder. I have found this to be much more accurate than measuring from the table top or using clip on throw meters. With the anhedral stab the rods come together and cross with down elevator and seperate with up elevator making an exact comparison difficult. Any suggestions that would work as well?
Thanks,
Stuart
Thanks,
Stuart
09-19-2007, 08:20 PM
#2
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RE: Anhedral stab setup
You could use a single hardwood pushrod, wrapping and expoying 2 metal pushrods to it,and exit the fuse at the same distance from the tail to a set of bases with adjustable control-arm posts. ( Making sure the main pushrod goes down the center of the fuse).
Mont 2 servos ( one on each side) for eack stab half.
Mont 2 servos ( one on each side) for eack stab half.
09-19-2007, 09:22 PM
#4
RE: Anhedral stab setup
Bobcat, I am not looking for a servo connection but way to compare the throw to each elevator half to make sure that they are equal. Even with a single pushrod or dual servos there will usually be slight mismatch in movement due to slight control horn position or angle differences. Or in the case of dual servos, slight differences between servos.
Stuart
Stuart
09-19-2007, 09:59 PM
#5
RE: Anhedral stab setup
Stuart,
I made myself a throw meter from Depron (pasted on a paper compass), using a hanging weight...thanks to Bob Pastorello's web site (see link below). If clamped carefully to each elevator half, one at a time, it can read with good repeatability.
http://www.rcaerobats.net/DeflectionGauge.htm
good luck,
mark
I made myself a throw meter from Depron (pasted on a paper compass), using a hanging weight...thanks to Bob Pastorello's web site (see link below). If clamped carefully to each elevator half, one at a time, it can read with good repeatability.
http://www.rcaerobats.net/DeflectionGauge.htm
good luck,
mark
09-19-2007, 10:59 PM
#6
RE: Anhedral stab setup
Stuart,
I've set up an anhedral stab and just used the method you described in your first post. If you attach the carbon rods so they don't cross, but actually just come right next to each other at full down elevator, you can still compare them using this method. I've found that the space between them doesn't make a huge difference. Because you're essentially extending that elevator so far out with the carbon rod, small misalignments can be spotted pretty easily.
-Brett
I've set up an anhedral stab and just used the method you described in your first post. If you attach the carbon rods so they don't cross, but actually just come right next to each other at full down elevator, you can still compare them using this method. I've found that the space between them doesn't make a huge difference. Because you're essentially extending that elevator so far out with the carbon rod, small misalignments can be spotted pretty easily.
-Brett
09-20-2007, 04:43 AM
#7
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RE: Anhedral stab setup
I have an idea using two laser pointers, beamers etc. and small mirrors mounted temporarily to the control surfaces. Mounting model vertically next to a wall few feets off so you can use tape measurer or even draw some sort of scale to the wall. For lasers there is a need for a simple wall mounting device which you can adjust height so that when neutral they are aligned horizontally with reflected laser dots which makes scale equal to both directions.
Because of reflection the scale will be logarithmic in the wall and multiplied with two and it limits the control surface deflection you can measure but with aerobatic models I believe it can be done in normal workshop. Usually control surfaces taper so flat mirrors won´t be aligned with zero line. Therefore model does not have to be perfectly vertical but needs some tilting. This principle should be really accurate as long the beams are horizontal when neutral.
Because of reflection the scale will be logarithmic in the wall and multiplied with two and it limits the control surface deflection you can measure but with aerobatic models I believe it can be done in normal workshop. Usually control surfaces taper so flat mirrors won´t be aligned with zero line. Therefore model does not have to be perfectly vertical but needs some tilting. This principle should be really accurate as long the beams are horizontal when neutral.
09-23-2007, 07:08 AM
#8
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RE: Anhedral stab setup
ORIGINAL: esamart
I have an idea using two laser pointers, beamers etc. and small mirrors mounted temporarily to the control surfaces. Mounting model vertically next to a wall few feets off so you can use tape measurer or even draw some sort of scale to the wall. For lasers there is a need for a simple wall mounting device which you can adjust height so that when neutral they are aligned horizontally with reflected laser dots which makes scale equal to both directions.
Because of reflection the scale will be logarithmic in the wall and multiplied with two and it limits the control surface deflection you can measure but with aerobatic models I believe it can be done in normal workshop. Usually control surfaces taper so flat mirrors won´t be aligned with zero line. Therefore model does not have to be perfectly vertical but needs some tilting. This principle should be really accurate as long the beams are horizontal when neutral.
I have an idea using two laser pointers, beamers etc. and small mirrors mounted temporarily to the control surfaces. Mounting model vertically next to a wall few feets off so you can use tape measurer or even draw some sort of scale to the wall. For lasers there is a need for a simple wall mounting device which you can adjust height so that when neutral they are aligned horizontally with reflected laser dots which makes scale equal to both directions.
Because of reflection the scale will be logarithmic in the wall and multiplied with two and it limits the control surface deflection you can measure but with aerobatic models I believe it can be done in normal workshop. Usually control surfaces taper so flat mirrors won´t be aligned with zero line. Therefore model does not have to be perfectly vertical but needs some tilting. This principle should be really accurate as long the beams are horizontal when neutral.
The problem with any of that is that it isn't simple to get perfect alignment of the pointer lasers to begin with. If the elevators extended all the way out on the stab, then the lasers could be attached at the elevator ends
09-23-2007, 12:23 PM
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RE: Anhedral stab setup
Surface mounted pointers should work fine and give more accuracy than sticks etc.
I wrote vertically but I saw in my mind nose down. For experiment perhaps a chair is sufficient mount for a model. Wings against handrails and pillows stuffed around the nose to keep model stable. When the distance is three feet and reflection multiplies the deflection 5 decrees equals 6,34'' in the wall. Using Tangent:
10 = 13,1''
15 = 20,8''
20 = 30,2''
25 = 42,9''
30 = 60,4'' which starts to bend to the floor and roof.
Perhaps stamp size of Mono-kote "mirror" is good for reflection and bottom side they won't ruin the design. Advantage using mirror is that it shows if there is angle difference between surfaces facing to the beamers, which is not so easy to find with surface mounted devices. Their accuracy can be verified mounting them first to the same surface and next turning another upside down.
I wrote vertically but I saw in my mind nose down. For experiment perhaps a chair is sufficient mount for a model. Wings against handrails and pillows stuffed around the nose to keep model stable. When the distance is three feet and reflection multiplies the deflection 5 decrees equals 6,34'' in the wall. Using Tangent:
10 = 13,1''
15 = 20,8''
20 = 30,2''
25 = 42,9''
30 = 60,4'' which starts to bend to the floor and roof.
Perhaps stamp size of Mono-kote "mirror" is good for reflection and bottom side they won't ruin the design. Advantage using mirror is that it shows if there is angle difference between surfaces facing to the beamers, which is not so easy to find with surface mounted devices. Their accuracy can be verified mounting them first to the same surface and next turning another upside down.
09-23-2007, 07:01 PM
#10
RE: Anhedral stab setup
ORIGINAL: rwlewis
Silly me, I just stand behind mine and eyeball it...
Richard
Silly me, I just stand behind mine and eyeball it...
Richard
I added a sekrut tekneke- setup the lighting to cast an even- low angle shadow -front to rear .
Using this method -I can get it spot on.
after all is said n done -the worst errors are usually found to be hinging errors so all the alignment setups , which all the special fixtures in th world will not correct
anymore -I fly the plane and then tweak trims as needed
The methods used by carpenters and builders -over the centuries - work fine on these models
I gave away all the do dads my son purchased to do alignments -they were nicely made and gave the numbers but I never saw any improvement in accuracy
