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General control line discussion => Open Forum => Topic started by: Kafin Noe’man on April 20, 2025, 02:58:45 AM
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Hi all, I’m looking for a pic or scan of the Brodak P‑40 plan showing the inboard wing.
I’d like to review the designer’s intended leadout position.
Thanks in advance!
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Use an adjustable leadout guide.
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Use an adjustable leadout guide.
Yes, it’s already installed.
I have been messing around with it for quite some time.
Since it’s an ARF, so I don’t have any plans with me.
I’m just curious where it’s intended at the start.
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I have no idea what the plan shows and that in itself wouldn't be more than a starting point. The ending position will be very close to 1 1/2 to 2 degrees nose down when suspended by the leadouts on a single hook. That position is dictated by the final actual CG location of the airplane. I start with that and may tweak it back and forth a bit in test flying but most always end up with about where I started. If the airplane is electric you might wish to start at one degree.
Dave
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Here are pics of the plan.
My P40 ARF flies well with the following:
CG at 2-3/4" behind the wing LE at the fuselage
Centerline of the 2 lead outs 7/8" behind the CG point
BTW, the Brodak website (P40 ARF) mentions the same CG location as 2-3/4" behind the LE.
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2nd pic
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The plan indicates a range for an adjustable guide.
When in doubt, start aft and work it forward. Or you could start forward and eat the plane.
Lew McFarland originated adjustable leadouts on his Shark 45 because he didn't know where to put them.
This was in contrast to 10,000 Top Flite Noblers which were well trimmed-out and everybody knew where the leadouts needed to be.
I don't fly mass produced ARF's. But I'm of the opinion that the designer would have the leadouts where they belong, or at least close enough for somebody who buys and flys ARF's.
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Yes, it’s already installed.
I have been messing around with it for quite some time.
Since it’s an ARF, so I don’t have any plans with me.
I’m just curious where it’s intended at the start.
3/4"=1" behind the CG, presuming you don't have rudder offset.
Brett
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I have no idea what the plan shows and that in itself wouldn't be more than a starting point. The ending position will be very close to 1 1/2 to 2 degrees nose down when suspended by the leadouts on a single hook. That position is dictated by the final actual CG location of the airplane. I start with that and may tweak it back and forth a bit in test flying but most always end up with about where I started. If the airplane is electric you might wish to start at one degree.
Dave
What Dave said, ignore the plans and hang your model by the leadouts for an initial setting. Even if it's the same design every model is different.
I usually hang it by the leadouts with the leadout adjuster loosened, carefully manipulate the model to where it's center line is level horizontally, then tighten the adjuster. Don't worry about what the plans show or the leadout angle at this point, you want the model to hang dead level or very slightly to the outboard. It's good to also look at it from the front or rear and see if the wing is hanging dead vertical as well. Do both of these initial checks and you'll be safe and should be very close to a final setting.
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What Dave said, ignore the plans and hang your model by the leadouts for an initial setting. Even if it's the same design every model is different.
3/4" is about 1.8 degrees. You don't have to hang it up to figure it out.
Brett
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I don't know if this helps you with your problem, but:
I've got a couple of Brodak 1/2A L'il Jumpin Beans and the line leadouts are shown far ahead of where they are in the old Carl Goldberg original plans. The Motor and gas tank are also far ahead of where they were on the original. I'm going to build mine like the original. (Including using a reed-valve .049.) The Brodak version probably flies great, but the more forward CG means that the plane will be less jumpy than the original.
Jumpy is what I want!
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I don't know if this helps you with your problem, but:
I've got a couple of Brodak 1/2A L'il Jumpin Beans and the line leadouts are shown far ahead of where they are in the old Carl Goldberg original plans. The Motor and gas tank are also far ahead of where they were on the original. I'm going to build mine like the original. (Including using a reed-valve .049.) The Brodak version probably flies great, but the more forward CG means that the plane will be less jumpy than the original.
Jumpy is what I want!
The Brodak P40 ARF is a 53" wingspan model. I believe the original author is using an OS 46LA engine.
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3/4" is about 1.8 degrees. You don't have to hang it up to figure it out.
Brett
To each their own, and I certainly can't debate Brett.
I do like to hang a newly finished model though, if nothing else, to get an eyeball reference on things. I feel like with all the weight variables of a multitude of different engine and tank choices, hardware used, finishes, etc., that even if it's the same design every model wants slightly different settings. All of these variables affect what (I feel) is a front to rear "balance" when looking at the model from the top or bottom while it's hanging. With the process, I'm imagining the model "balancing" at the bellcrank pivot and then I set the initial leadout trim so the thrust line is either level or pointing just slightly to the outboard. IDK, seems to work for me.
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Hi Everyone,
Thanks for your sharing. It took me awhile to try your advices and to see its effect on my flying plane.
After reviewing the plan that Colin has shared, I just found out that my LO position was too far aft, it was about 1" or 1.1" behind the CG.
I moved forward my LO so it's now 3/4" behind the CG, and voila! My tension is much more equal all around now.
Though, I still have to fly more and more to verify it but I can feel the difference.
Best,
Kafin