Engine offset VS. Adj. leadout wires?

Adj. lead out wires work the same way as adding engine offset.

Fact or fiction?

CB

>Adj. lead out wires work the same way as adding engine
>offset.
>
>Fact or fiction?
>
>CB

fiction. Engine offset will change the outward yaw and may get the leadouts in line with where they should be (for that offset), but the offset will certainly mess up the trim.

If the engine/airplane is properly otherwise trimmed, then the adjustable leadouts will allow you to set the leadout position in line with the line rake caused by air drag and which is also affected by line length, line size, and air speed (as well as air density if you really want to get critical).

An engine set at zero degrees will already generate some "offset" by virtue of the constant left turn. Adding excessive offset (outboard) will only add to drag and can cause a loss of line tension overhead. Moving the leadouts forward/backward can allow one to adjust line tension more equally throughout the pattern.

Slightly forward of "optimum" while in level flight will increase tension overhead since gravity reduces line rake up above and necessitates a more forward location at that point in the pattern. Give some in one location (level flight) to gain some in another (overhead).

LN,

OK, understandable.

So, with that trim information given, it seems pointless, possibly even lazy, to build a model, which has absolutely no leadout wire adjustment?

So, I should add that feature?

Thanks,

CB

Yes add the adjustable leadout feature as well as the wing tip weight box.
DOC Holliday

As I said in another thread, yes, add every adjustment you can. In the "good old days" we would cut into the wing tip to adjust the leadouts. We would cut into the other wing tip to add or remove weight. We would cut into the nose to raise or lower the tank.

Much simpler when you build these adjustables into the plane in the first place.

>An engine set at zero degrees will already generate some
>"offset" by virtue of the constant left turn.
>Adding excessive offset (outboard) will only add to drag and
>can cause a loss of line tension overhead. Moving the
>leadouts forward/backward can allow one to adjust line tension
>more equally throughout the pattern.
>
>Slightly forward of "optimum" while in level flight
>will increase tension overhead since gravity reduces line rake
>up above and necessitates a more forward location at that
>point in the pattern. Give some in one location (level
>flight) to gain some in another (overhead).

Just to extend on this one, what if (and there is always a 'what if') the plan that you have gives 2º engine offset.
Is it wise to follow that even though it could be dated knowledge or simply go the more modern route of 0º offset?

I have only used + degrees of offset in the past and never noticed any detriment to the model, but that's not to say that it couldn't be improved upon.

Thanks.

>
>Just to extend on this one, what if (and there is always a
>'what if') the plan that you have gives 2º engine offset.
>Is it wise to follow that even though it could be dated
>knowledge or simply go the more modern route of 0º offset?
>
>I have only used + degrees of offset in the past and never
>noticed any detriment to the model, but that's not to say that
>it couldn't be improved upon.
>
>Thanks.
>

In the "good old days" people thought you needed wide amounts of engine offset and rudder offset and that this would help line tension. I, too, was guilty of doing that because I didn't know any better. There are still some advocates of maybe up to 2 degrees of offset, so maybe it is not too bad. I, personally, would go with zero.

Matt's goal is zero+. In other words, it is sometimes hard to get it exact. But if you are going to miss by half a degree or so, make sure you miss by aiming out, not in. Just how accurate can you get it?

Edit: Some planes have a lot of inboard assymetry. They make the inboard wing longer (measured from the fuselage) than the outboard wing thinking they are compensating for the greater lift of the outboard wing moving faster. But the wing does not know any difference. All this does is move the fuselage outboard on the wing to become "tip weight", while it also moves the thrust line outboard as well. When you move the thrust line outboard, then you maybe should add a "little" outboard offset on the engine as well The farther outboard you move the thrust line, the more engine offset you will need to keep it moving forward and not have it turn your plane inboard.

Since some of these early designs had excessive assymetry (anything much beyone half an inch becomes excessive) then maybe the outboard thrust offset could become necessary.

>Adj. lead out wires work the same way as adding engine
>offset.
>
>Fact or fiction?

Fiction.

Brett

Science fiction horror story, with possibly drama at the end.

Dave Hull
LA_Flyer