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Author Topic: Stab alignment question  (Read 665 times)

Offline kevin king

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Stab alignment question
« on: January 25, 2023, 03:15:41 AM »
When viewing from the front of the ship, should the leading edge of the stab be exactly parallel to the top of the wing, on an unequal panel wing? I noticed the outboard leading edge of the stab is higher than the inboard side on my Vector 40.
Thanks.

Kevin

Offline Miotch

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Re: Stab alignment question
« Reply #1 on: January 25, 2023, 07:16:33 AM »
I guess it would depend on exactly what angle you are viewing it from the front.  If you are viewing it dead on, the centerline of the stabilizer should run parallel to the centerline of the wing.  If the wing ribs are the same depth on both sides of the wing near the fuselage, it should be symmetrical.  Now, if the slope of the top of the wing is different near the fuselage, then it might look different.  But my memory tells me the Vector rib slope is symmetrical.  My memory is sometimes wrong, though.  The leading edge of the stab will not be exactly parallel to the top of the wing because of the rib slope.  But it should be symmetrical on inboard/outboard sides.

I think some of my fuselage's warp during building because no matter how exacting I think I do it, sometimes I notice the same thing.  I've had a few planes with slight differences I just left alone  and they've flown just fine for what I do.   But I'm not out there practicing the pattern or competing.  But it has happened to me even when I thought I had it perfect when glueing[/i].

Online Brett Buck

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Re: Stab alignment question
« Reply #2 on: January 25, 2023, 09:44:51 AM »
When viewing from the front of the ship, should the leading edge of the stab be exactly parallel to the top of the wing, on an unequal panel wing? I noticed the outboard leading edge of the stab is higher than the inboard side on my Vector 40.
Thanks.

Kevin

   I think the centerline if the stab should be on a plane parallel to the plane of the wing. if you are just eyeballing it, then, make the stab parallel to the hinge line of the wing, or the top surface, it will be close enough.

    I strongly recommend measuring the stab alignment to the wing using a flat reference surface and trammeling everything parallel in all directions, both tilt and skew. It is extremely critical.

     Brett

Offline Joe Ed Pederson

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Re: Stab alignment question
« Reply #3 on: January 25, 2023, 10:13:29 AM »
 
    I strongly recommend measuring the stab alignment to the wing using a flat reference surface and trammeling everything parallel in all directions, both tilt and skew. It is extremely critical.

     Brett

Kevin,

I use the top of my table saw for a flat surface and use the alignenment sticks (plywood with numerous small holes drilled by a lazer cutter) that I bought from Walter Umland at BuiltRiteFlyRight.  He's listed in the vendors section on Stunthangar.He has had health issues and isn't back to full production but you can email him at  builtrightflyright@builtrightflyright.com and see if he has any.

Here's a video Rusty made that shows how to use them:   and    

I've had really good success with this system.

Joe Ed Pederson

Online Dan Berry

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Re: Stab alignment question
« Reply #4 on: January 25, 2023, 01:25:04 PM »
Parallel to the trailing edge of the wing is what you need. The TE makes a straight line.

Offline kevin king

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Re: Stab alignment question
« Reply #5 on: January 27, 2023, 01:12:12 AM »
Its definitely misaligned stab or the fuse twisted while putting in the formers or something. HB~> Resetting the stab at this phase would also mean cutting off the fin and resetting it as well. This was supposed to be an expendable ship for practicing the pattern. From the back view the high side of the stab is up an 1/8" at the tip. Maybe i could try slitting the fuse on beneath the stab, tweek it down and glue it there. Kind of disheartening anyway you look at it.
 Thanks for replies , suggestions gentlemen. Its appreciated.

Kevin.
« Last Edit: January 27, 2023, 01:39:56 AM by kevin king »

Offline Miotch

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Re: Stab alignment question
« Reply #6 on: January 27, 2023, 07:36:10 AM »
I have the same problem now on the Starduster Too I'm trying to design as I build (you should design and plan it all out first, I've learned).  Thought about sawing a slice on both sides of the rear fuselage, and trying to clamp one side down and insert an 1/8" sliver in the other side, but then realized I'm likely to pull the fin/rudder out of alignment if I do that.  So, I'm going to have to start carefully slicing through some glue joints and trying to reset it.  ........... sigh .............

Beautiful work on your Vector, by the way !!

Online Dan Berry

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Re: Stab alignment question
« Reply #7 on: January 27, 2023, 09:08:33 AM »
Its definitely misaligned stab or the fuse twisted while putting in the formers or something. HB~> Resetting the stab at this phase would also mean cutting off the fin and resetting it as well. This was supposed to be an expendable ship for practicing the pattern. From the back view the high side of the stab is up an 1/8" at the tip. Maybe i could try slitting the fuse on beneath the stab, tweek it down and glue it there. Kind of disheartening anyway you look at it.
 Thanks for replies , suggestions gentlemen. Its appreciated.

Kevin.

Slit the fuselage below the low side. Wedge in some 1/64 plywood and check the tilt.  Adjust as needed and glue it in.

Online Brett Buck

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Re: Stab alignment question
« Reply #8 on: January 27, 2023, 10:08:42 AM »
Its definitely misaligned stab or the fuse twisted while putting in the formers or something. HB~> Resetting the stab at this phase would also mean cutting off the fin and resetting it as well. This was supposed to be an expendable ship for practicing the pattern.

      If it is "expendable", it is also no big deal if you cut it up and realign it, right?  I have been cut into several fully-finished airplanes to fix less critical issues than this. It's not that far along, rework will be invisible.  I have made very extensive changes to finished airplanes to fix  various issues including a week before last years NATs.

   It is *very important* to get this sort of alignment issue corrected. Practicing, flying in the world champs, doesn't matter. Do whatever you need to do.

     Brett

     
       

Offline Dan McEntee

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Re: Stab alignment question
« Reply #9 on: January 27, 2023, 02:39:31 PM »
Slit the fuselage below the low side. Wedge in some 1/64 plywood and check the tilt.  Adjust as needed and glue it in.

   Depending on how the bottom sheeting is installed, diagonal slits and shims can be installed there to twist the fuselage in the direction you want to go. Sometimes it takes only one, sometime three or more, but is usually rock solid and will hold the sitting once glued in with thin CA. If you can twist the fuselage easily to get it to move the way you need to, these slits and shim will work. Or you can just steam it and old it on the opposite twist for a while and see how it holds. The slit and shim methods work mechanically against the force that caused the twist, so usually will not change once locked in.

 Type at you later,
  Dan McEntee
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Offline kevin king

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Re: Stab alignment question
« Reply #10 on: January 27, 2023, 02:45:44 PM »
Surgery it is guys. S?P

Online Brett Buck

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Re: Stab alignment question
« Reply #11 on: January 27, 2023, 03:33:05 PM »
   Depending on how the bottom sheeting is installed, diagonal slits and shims can be installed there to twist the fuselage in the direction you want to go.

  Yes, that is a generally very useful and low-impact solution. You should have seen Ted's face when I took one of Shareen's bread knives to the trailing edge of an ARF Strega to straighten it. Cut horizontally through the hinge line, from about half-span to the tip, then up the tip to the LE. Twist it straight, dribble thin Hot Stuff in the crack, poof, problem solved.

    I am not sure if he was more alarmed about the cut, or about the fact that I dared to use one of Shareen's knives.

    Brett

Offline Dan McEntee

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Re: Stab alignment question
« Reply #12 on: January 27, 2023, 06:11:33 PM »


    I am not sure if he was more alarmed about the cut, or about the fact that I dared to use one of Shareen's knives.

    Brett

    That would have been my biggest concern!! I use some kitchen utensils for model building but I have learned to buy my own. I need to add pizza cutter to my list, though. It's handy for scoring corrugated cardboard or even chip board. Just keep forgetting to head down that aisle at the store. The slit and shim trick works on sheeted foam wings also. I think that's where I first learned it, back in my sailplane days.
  Type at you later,
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Offline Ken Culbertson

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Re: Stab alignment question
« Reply #13 on: January 27, 2023, 08:24:33 PM »
Its definitely misaligned stab or the fuse twisted while putting in the formers or something. HB~> Resetting the stab at this phase would also mean cutting off the fin and resetting it as well. This was supposed to be an expendable ship for practicing the pattern. From the back view the high side of the stab is up an 1/8" at the tip. Maybe i could try slitting the fuse on beneath the stab, tweek it down and glue it there. Kind of disheartening anyway you look at it.
 Thanks for replies , suggestions gentlemen. Its appreciated.

Kevin.
I had one like that.  I made the mistake of using white glue on an imperfect saddle.   It started straight but the glue pulled it crooked.  I have since used Epoxy on all alignment type joints.  Anyway, I cut a slit on the low side of the fuselage about 1" below the stab and broke loose the fuselage end joint above it.  Then I made some wedges out of 1/8" balsa and slid them into the crack till it lined up.  Used CA to glue in the wedge and sanded the whole mess flat.  Works.

Ken
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Online Brett Buck

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Re: Stab alignment question
« Reply #14 on: January 27, 2023, 09:13:12 PM »
    That would have been my biggest concern!!

  See, not that big a deal, because if its becomes an issue, I can just go home and leave Ted to explain. Problem solved!

      Brett

p.s. Bread knife because I needed about a foot-long but thin blade. You want a knife for this cut, not a saw, because you want to just push the wood aside, not remove it completely. Although this was an ARF Strega, losing .020 using my Japanese no-set saw wouldn't have made much difference.

Online Brett Buck

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Re: Stab alignment question
« Reply #15 on: January 27, 2023, 09:25:46 PM »
I had one like that.  I made the mistake of using white glue on an imperfect saddle.   It started straight but the glue pulled it crooked.

   That is always an issue. White glue is particularly bad about it - it both wets the wood, causing it to swell, and the glue itself shrinks, with unpredictable results. It has lots of water compared to something like Titebond. Ambroid and other model cements are the dead worst, of course.

   My usual approach is to get it aligned, then tack-glue with thin Hot Stuff. Let it sit for a while or overnight, then remeasure it, if no good, crack it loose and scoot it whichever way it goes, try again. Work up to it, once you are good, tack it better, wait an hour, measure again, repeat, until it is very solid in all the likely trouble spots and you can't easily move it. Then glue it solid with more Hot Stuff.

    Letting it sit between cycles is very important, because you usually have to nudge/slide/push things around to get it to line up. You need to give it time to relax and attain a stable new position, then see if it stays. If you hard-glue it all at once, you have to do something else more drastic (like Kevin's case). I know what other people do for alignment, and someone like Paul would be horrified at my lack of alignment jigs, but I have had very repeatable results, as hacky as I am.

     Brett

Offline Joe Ed Pederson

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Re: Stab alignment question
« Reply #16 on: January 28, 2023, 09:26:09 AM »
   That is always an issue. White glue is particularly bad about it - it both wets the wood, causing it to swell, and the glue itself shrinks, with unpredictable results. It has lots of water compared to something like Titebond. Ambroid and other model cements are the dead worst, of course.

     Brett

Brett,

Glad I read your post.  I have been using Sigment to glue on horizontal stabs and vertical stabilizers for three or four years now, thinking that if it turned out misaligned when dry I could dissolve the Sigment with lacquer thinner.   So far the alignment has not changed when the Sigment dried, so I guess I've just been lucky so far.

I'll switch to gluing stabs on by tacking them on with thin CA and checking the next day and then finishing the job as you suggest.

By the way, I love to do some of the stages of construction (build the wing), but other stages can stall me out for days or even weeks.   Gluing the wing in and the stab on are stages of construction that cause me to say, "I don't have enough time to start and finish aligning things, it'll have to wait for another day."  Mainly, it's just my apprehension of gluing the wing or stab on, only to discover the next day that it went crooked on me.   This thread helps reduce my apprehension since I have learned better ways of getting it right the first time and knowing several ways of fixing it if it does come out crooked.

One of the reasons I abandoned RC in 2017 is the RC ARFs are so good, there's no point in building your own models.  Control line ARFs aren't very appealing because you either need to replace the motor mounts (ARF Nobler) or replace the leadouts (many Brodak ARFs).  And over time I've learned that models sold or given away by individuals at contests and funflys nearly always need a lot of aggravating rework to fly well. But I do like building my own models start to finish and I like building from plans as much as from kits.  Now, if I just had enough lifetimes to build all the models I would like to build.  And it is always difficult to stay focused on one build all the way through without getting distracted by the "OOOh, now that (other) model is prettier or would fly better!)

The other reason I came back to CL is the challenge.  Nobody ever masters the pattern and I can't even do half the maneuvers yet.  CL stunt will be a challenge until I can't stand in the circle and spin around anymore.


Joe Ed Pederson

Offline Ken Culbertson

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Re: Stab alignment question
« Reply #17 on: January 28, 2023, 02:17:51 PM »

The other reason I came back to CL is the challenge.  Nobody ever masters the pattern and I can't even do half the maneuvers yet.  CL stunt will be a challenge until I can't stand in the circle and spin around anymore.

Joe Ed Pederson
When I came back to the sport in 2017 my wife asked why I was not flying RC again.  I wish I had your answer then.  There never has been and probably never will be a 645.   

Ken
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Offline Joe Ed Pederson

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Re: Stab alignment question
« Reply #18 on: January 28, 2023, 02:52:41 PM »
When I came back to the sport in 2017 my wife asked why I was not flying RC again.  I wish I had your answer then.  There never has been and probably never will be a 645.   

Ken

Ken,

 And even if you could fly a 645 once, it would most likely energize you all the more to see if you could do it twice.

Joe Ed

Offline Ken Culbertson

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Re: Stab alignment question
« Reply #19 on: January 28, 2023, 03:48:24 PM »
 HB~>
Ken,

 And even if you could fly a 645 once, it would most likely energize you all the more to see if you could do it twice.

Joe Ed
You are absolutely right!  I bowled a 299 once in my inglorious youth and it took me 10 years before I gave up chasing that rouge 7 pin. HB~>

Ken
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Offline kevin king

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Re: Stab alignment question
« Reply #20 on: February 01, 2023, 09:35:09 AM »
Stupid stab. I'll teach you not to be crooked. (Stab gets lesson on torque).

Offline MikeyPratt

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Re: Stab alignment question
« Reply #21 on: Yesterday at 02:17:08 PM »
Yeah Kevin,
Don't take any off that crap from that pesky stab, Take that you Crooked SOB.

Mikey

Offline Tim Wescott

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Re: Stab alignment question
« Reply #22 on: Yesterday at 08:23:19 PM »
I'm not saying this to be cruel, or rub it in, etc.

But -- the next time you build a plane, you want to check it every which way before it goes together, then as you're gluing it, then right after you glued it, then check it again after the glue is dried and before you invest any more time at all into it.

I glue that sort of thing with epoxy mixed with microballoons, so I have time to fuss over it before it gets hard.  If I'm lucky in my timing I'll get it all glued up, go find something to do for half an hour, then check back in with it -- usually if it's wrong at that point I can't just move it so it's right, but I can rip it all apart with minimal damage and try again the next building session.
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