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Author Topic: Leadout position  (Read 865 times)

Online Craig Beswick

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Leadout position
« on: October 07, 2020, 04:05:19 AM »
Hello all,
I am just completing an SV-11 ARF. I think the older version with wing mounted landing gear.

I found Randy Smiths post on the CG, 3 3/8" to 3 5/8", behind the LE.

I am sure he, at some stage, posted that the leadouts, to start with, should be placed 1" behind the CG. Is that right? Or a good place to start?

Thanks
Craig
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Offline John Paris

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Re: Leadout position
« Reply #1 on: October 07, 2020, 09:52:42 AM »
Craig,
The one inch rule is a good place to start.  if you can hang it by the leadouts in this position and see a slight nose down condition then you should be fine. For reference, I have the same model in electric and my front leadout is at 2 inches as measured along the wingtip to a point if the leading edge is extended straight inward.  Seems to fly well here.
John
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Online Ken Culbertson

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Re: Leadout position
« Reply #2 on: October 07, 2020, 12:01:24 PM »
I am not one of those that will just nod in agreement when I don't have a clue what you are talking about so this may come across as a stupid question. n~

So much of what we measure is at mean chord.  For whatever reason I have always balanced my planes at that point.  Seems silly since balancing them at the fuselage is just as easy.  Maybe it is so that I can get a quick visual on where my wheels are relative to the balanced point.  So, when we just say 2 1/2" behind the LE, where on the LE is that?  Centerline, fuselage joint, mean chord?  I know, it is on the plans but the only plans I use are ones I drew up and "That looks about right" is not a standard linear measurement. LL~

I just make sure the CG is behind the wheel, tape one of those little line bubbles to the nose and hang it till I get a slight down bubble then go out and fly a couple of 15 seconds flights.  To me on a first flight it is only important that the leadouts be behind the CG, the wheels in front and that there are the same number of takeoffs and landings.  I find bench trimming for balance to be a waste of time.  Getting the right tip weight, CG and leadout position are best done at the field.

OK, this is the point where you call me an idiot .... n1

Ken
« Last Edit: October 07, 2020, 12:33:02 PM by Ken Culbertson »
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Offline john e. holliday

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Re: Leadout position
« Reply #3 on: October 07, 2020, 12:30:19 PM »
Yes hang by the lead outs.  If it hangs nose slightly down you should be okay to start.  If hanging tail down, don't even think about flying it unless you can move back wards real good. D>K
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Online Craig Beswick

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Re: Leadout position
« Reply #4 on: October 07, 2020, 02:31:59 PM »
Thank you Doc and John.

Ken, I always measure CG from where the wing attaches to the fuselage. For me, it is easier to check it there.

So I am looking for the fuselage to be slightly downward, at the nose, when hanging from the lines?

Thank you.
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Online Ken Culbertson

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Re: Leadout position
« Reply #5 on: October 07, 2020, 04:26:09 PM »
Thank you Doc and John.

Ken, I always measure CG from where the wing attaches to the fuselage. For me, it is easier to check it there.

So I am looking for the fuselage to be slightly downward, at the nose, when hanging from the lines?

Thank you.
With the flaps at neutral - you got it.

Ken
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Offline Perry Rose

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Re: Leadout position
« Reply #6 on: October 10, 2020, 09:51:21 AM »
Measuring c/g or leadout location is easier if you measure from the trailing edge. On most planes with flaps the t.e. is straight. So if the c/g is 7 inches up from the t.e.( as measured on the plans) the leadouts should be 6 inches up. Or you can use the line level on the nose method.
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Online Ken Culbertson

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Re: Leadout position
« Reply #7 on: October 10, 2020, 02:17:18 PM »
Measuring c/g or leadout location is easier if you measure from the trailing edge. On most planes with flaps the t.e. is straight. So if the c/g is 7 inches up from the t.e.( as measured on the plans) the leadouts should be 6 inches up. Or you can use the line level on the nose method.
You have just alluded to another use of predictive calculations.  Placement of the adjustable leadout guide.  Ever put one in too far back/forward? 

Ken
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Offline L0U CRANE

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Re: Leadout position
« Reply #8 on: December 02, 2020, 03:58:04 PM »
Yes. I DID have one model that had leadout guides and CG in a really bad mismatch! So bad that when I pulled input in one direction, the 'other' line sagged a long way back from the loaded line. Noticeably more control input effort was needed then.

Learned a lot from that, and studied why and how it happened. Not a pleasant lesson, but I gained more in learning why, and how to prevent it.

Many years ago, and now we all have a much better understanding of such. Go with the current guidance!

\BEST\LOU

Online Howard Rush

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Re: Leadout position
« Reply #9 on: December 08, 2020, 10:09:03 PM »

Yes. I DID have one model that had leadout guides and CG in a really bad mismatch! So bad that when I pulled input in one direction, the 'other' line sagged a long way back from the loaded line. Noticeably more control input effort was needed then.

How do you figure that?
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