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03-08-2010, 10:51 PM | #1 |
RCC Senior Contributor
I am: Rob B
Join Date: Dec 2008
Location: Uxbridge, Ont.
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Slight Mistake - Can I Compensate?
Fellow Builders/Flyers,
While assembling the pieces of my latest kit built plane I was concentrating so hard on getting the horizontal stab/elevator square to the fuse that I forgot to check it was truly horizontal. After gluing the horiz. stab/elev. in place I discovered it was off by a few degrees. Looking from the front, the left side is lower. My question is: Does anyone have an informed opinion of how this will affect the handling? If the effect is predictable, what do I need to do in terms of trim to compensate? Thanks. Hope I can make a trim tweak to avoid a messy fix to the tail. RB |
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03-08-2010, 11:05 PM | #2 |
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Re: Slight Mistake - Can I Compensate?
If the stab is not parallel to the wing, or the fin, your model will yaw with every application of elevator.
If this plane is for aerobatics, you should really fix it because it will never fly right (and there is no practical way of trimming or mixing it out), if its for something else, maybe it won't make a big enough effect to notice. |
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03-09-2010, 07:19 AM | #3 |
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I am: Cliff S
Join Date: Feb 2007
Location: Belleville Ont.
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Re: Slight Mistake - Can I Compensate?
If the stab and fin are properly orientated to the fuse simply shim or re-cut the wing mount so the fin and stab line up properly.
Kip |
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03-09-2010, 07:27 AM | #4 |
RCC Contributor
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Re: Slight Mistake - Can I Compensate?
Cut it out and put it right. One hours work.
When ever gluing the tail in place screw the wing to the fuselage. Set up at the correct wing incidence. Sopport the tail at the correct incidence. THEN glue. Note the incidence meters. Ed S
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03-09-2010, 09:26 AM | #5 |
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I am: Dave F
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Re: Slight Mistake - Can I Compensate?
Hi RB,
Been there, got the T-shirt ! Chad explained the problem nicely. A 'TRUE' airplane is a joy to fly. One that has some/any mis-alignments will need extra pilot effort to fly well.(and limits what you can do with it.) The difference between a good airplane and a great one is all about getting 'everything' just right. I have flown/crashed/flown/crashed/flown/crashed planes that are great when they are repaired properly. The exact same plane when I don't take the time to line up everything, turns into a 'dog' that flys terribly. Same plane, repaired properly, turns back into a 'great' one. (although heavier !) Is your wing rubber banded on RB? If so, you can shim the wing to the horizontal stab. It is a 'shabby' fix, but works. I prefer to 'bite the bullet' whenever I don't get the tail glued on straight. I reglue it, even though it can be a painful effort to do so. I'm not sure who taught me this...but...it works for me: Set the plane up, so you can see it from the back about 2-3 wingspans away. Close your weakest eyeball. You will see the minutest miss-alignment. Amazing how accurate it is. Beats any other measuring devices. Easy to check at the field too, if your plane is not performing the way it should. My repairing skills have improved flying Maac Scale Combat. Take care, Have fun, Dave'crosscheck'Fallowfield Maac 6437 Unabashed Combat Team |
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03-09-2010, 11:33 AM | #6 |
RCC Senior Contributor
I am: Rob B
Join Date: Dec 2008
Location: Uxbridge, Ont.
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Re: Slight Mistake - Can I Compensate?
Thanks for all your very well informed responses. I guess I knew the answer - some delicate surgery will be required to set the stab/elev. straight. Just thought with the miracles of modern Tx technology I might be able to program out the build error.
Wings are fixed on carbon rod so they are good. Vert. stab/rudder are correct. Just have to bite the bullet & square things up. RB |
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03-09-2010, 04:05 PM | #7 |
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I am: Bill G
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Re: Slight Mistake - Can I Compensate?
If it's epoxied in ,heat from your covering heat gun will soften the epoxy so you can remove the stab.
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03-09-2010, 08:14 PM | #8 |
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I am: Cameron T
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Re: Slight Mistake - Can I Compensate?
If you align the wing to match the horizontal stab, then your vertical stab will be out. Its a no win situation. Small surgery required. Outpatient basis.
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03-09-2010, 11:16 PM | #9 |
RCC Senior Contributor
I am: Rob B
Join Date: Dec 2008
Location: Uxbridge, Ont.
Feedback: 4 / 100%
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Re: Slight Mistake - Can I Compensate?
I am going to fix the problem so it will fly accurately but conditions were so perfect today my flying buddies & I decided to give her a test flight. Picture shows her sitting on the rapidly disappearing snow.
I had one of my very experienced & skillful friends buddy box with me to increase the probability of success & reduce the pucker factor. She took off perfectly in less than 10 feet & my friend took her around a couple of circuits at modest power. Flew beautifully with a bit of aileron trim needed to keep her straight (presumably because of mis-aligned tail surface). After a couple of minutes he decided to increase power & try a steep climb. As soon as he did so something wierd happened & the nose suddenly shot up & she started to act weird. He reduced power & got her under control & landed very nicely. Turned out the elevator servo had stripped when the high power/up elevator was applied. Luckily the elevator centred itself & my friend landed just using throttle control. A big pat on the back to Matt for his fast reactions & cool under pressure (in real life he is an Air Canada pilot - one who I'd be very happy to have fly me around). Not sure if the one servo was a problem or if it is not strong enough for the large control surface. Anyway, I'm going to upgrade to better servos with metal gears before Maiden Take 2. RB |
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