Speed,Combat,Scale,Racing > Speed Talk

Monoline lead out placement.

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Double Deuce:
I seem to remember using Fogg's program back when Bill Nusz and I were working together. And that has been a while and a half. I miss him to this day.

My point is not to criticize the program at all but to try to tell you the airplane does not necessarily  rotate about where the line attaches to the airplane but about the balance point. Has nothing to do with static nor flight balance cause they are the same. The cg will change through the flight due to fuel burn. Never have weighed a charged battery vs run down one, so will not comment on electric. The points of interest for line rake are the cg of the airplane and the line guide. Where a bellcrank is mounted is of no interest to Mother Nature. The inner wing span is not mentioned.  The bellcrank could be mounted in the tail cone and still be made to fly very well. Structural limits apply here. And a measure of common sense. A sorely lacking commodity these days.

Where more work really is needed is in the jet program as the cg change is relatively large and weight is reducing through the flight.  So the rake is changing through the run. this is why I worry more about rake and fuel feed that I do about rake and acft yaw. This does not mean I don't care about yaw and ignore it. It is there so you best deal with it.

And relative to your comment about the program working for you. How you know?

Luke


 

Les Akre:
Luke

"The points of interest for line rake are the cg of the airplane and the line guide."

Agreed, and since the line will have a rearward "Bow" or "rake" during flight due to line drag, where the line exits the wing relative to CG will determine if the model tracks the circle properly.
If our model speed is fairly constant, and it usually is during a powered speed flight, the distance measured from CG to where the line exits the wing will differ depending on the wing span of the model. On a short wing, the location where the line exits the wing relative to CG will be less rearward than with a longer wing, assuming the line rake is the same.

That is the only reason I can see for the inboard wing measurement.

Relative to your comment on the ever changing CG due to fuel burn during flight. I'm sure most of us, I do anyway, build the line guide on a speed model big enough to be able to insert a looped line end through the guide to attach to the control mechanism. Due to making the line guide a certain width for the given loop size of the wire, said wire will ride against either the front, or rear edge of the line guide during flight depending on how accurately the line guide was positioned relative to the CG. If the guide is positioned near, or at optimum for the model, then the width of the line guide should accommodate small CG variances without causing excessive yaw issues.
Obviously, if you use a line guide just big enough to insert the diameter of wire you're using, and then build the line end afterwards so that the line always stays attached to the controls, then any CG variances would be more critical to yaw.

"And relative to your comment about the program working for you. How you know?"

It may not be the last word in determining the line guide location, but it works better for me than what I was doing...

Les

Double Deuce:
I give up.

Luke

Les Akre:
Luke

After re-reading all the posts again, (and looking at your line rake program) this time something stuck. I now understand what your talking about.

I had never considered, or even thought of measuring that aspect of model balance before. Being mostly a two winged guy, I always just balanced a model in the conventional manner and called it good.

I'm older now as well, and sometimes my eyes take longer to open. Thanks for hangin' in there...

Les

Double Deuce:
Les

Thanks for not giving up on me. As a Cajun, I should know better than to try to  to explain anything to anyone else when my hands cannot be seen.

I will not discuss how many years I have been trying to makes sense of this line rake issue. Some of it clears up, and then fades from memory and I have to start all over. Don't ever get old.

I was hoping you would sit and think about what I was trying to say. Glad you did.

This issue exists in 1/2 A protos also. Two wings but engine and tank offset outboard. Not too far because of less weight but should be accounted for.

I don't think I have ever handled one of the sorta new kind of jet layouts but just looking, there has to be serious shift in the balance point on them.

Keep on thinking.

Good Holidays to you and yours.

Do hope we cross paths again before time runs down.

Take care

Luke

Luke

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