Author Topic: Bellcrank, normal or reverse (Read 135600 times)

Steve Hines · « **on:** December 31, 2014, 12:38:13 AM »

What is the pro and con's of a normal mount or a reverse mount. We fly off mostly grass fields, and try to have the down line in front. We have lost 3 planes for hooking the up line and had the plane come in at us. I did find a school that will let us fly off a parking lot. Sam only fly off pavement at the Nat's.

Paul Smith · « **Reply #1 on:** December 31, 2014, 07:03:16 AM »

Snagging a line is a bad thing either way.

In my opinion, just do what fits into the model best. None of this comes into play unless you hang the model on one line in maneuvers.

Tim Wescott · « **Reply #2 on:** December 31, 2014, 09:44:01 AM »

I have the luxury of flying off of a field that I mow, so it's short grass. Come dry flower head season, I just give up on graceful takeoffs and hold the handle over my head until the plane is clear of the ground.

I assume you've already figured this stuff out for yourself, but...

Bill Little · « **Reply #3 on:** December 31, 2014, 07:05:09 PM »

The reverse BC is an Al Rabe decision. He felt that by reversing the BC it would counter the effects of the torque caused by the prop on inside and outside maneuvers. As it is I do it by habit now on 99% of my models.

BIG Bear
RNMM/AMM

Istvan Travnik · « **Reply #4 on:** January 01, 2015, 03:39:46 PM »

I think, this question is far more complex, than it looks at first glance.
-it is not sure that the front positioned line will always hooked by some flower's head...

-all the models do some movements around the vertical axis, and -since the distance is not zero between the leadouts (usually it goes 1/2 to 1 inches)- this modulates slightly the controlling. We instinctively "calculate" with this, but inverting the bellcrank, we can get unwanted surprises.

-most pilots make not pure "up-and-down" movements with the handle, but sometimes turn it, and/or diverting his arm from the accurate radial, (backwards or forwards). See a nice video on this:

Interchanging the "up" and "down" lines requires a lot of training, I am sure...

john e. holliday · « **Reply #5 on:** January 02, 2015, 08:37:03 PM »

I notice that you don't keep your handle verticle all the time. I used to lay my hand on its back while inverted, but that was many years ago. I wish I had a video of Billy Werwages flight at VSC one year. I could swear his flying hand did not move that much. Of course the left arm is clutching the chest for some reason. Thanks for a very entertaining video. I can see why you are a champion.

Igor Burger · « **Reply #6 on:** January 04, 2015, 02:32:07 AM »

Hey!!! I know that man :-))

Thanks for posting Istvan ... I did not know I have such muscles in right hand when I fly :-P

BTW Istvan is right, line separation in tip makes unwanted inputs to lines, up line back makes negative feedback, while up line front make positive. That is reason why I build my models with up line back, it makes model more patient, however I always try to exchange them during initial trimming and test, I have one model which flies with crossed lines inside :- )). I probably depends on amount of Rabe rudder.

Brett Buck · « **Reply #7 on:** January 06, 2015, 11:17:35 AM »

Quote from: Igor Burger on January 04, 2015, 02:32:07 AM

Hey!!! I know that man :-))

Thanks for posting Istvan ... I did not know I have such muscles in right hand when I fly :-P

BTW Istvan is right, line separation in tip makes unwanted inputs to lines, up line back makes negative feedback, while up line front make positive. That is reason why I build my models with up line back, it makes model more patient, however I always try to exchange them during initial trimming and test, I have one model which flies with crossed lines inside :- )). I probably depends on amount of Rabe rudder.

I have tried that in the past, but I always wound up with them as close as I can get (within reason) and always with the conventional rear line "up". I just build it that way now, with no independent adjustment.

I think it's generally a big mistake to count on the difference in the line rake to adjust the yaw angle. If the lines were rigid rod, it might be viable, but it's more like pushing on a long, weak, spring. If you push on it one way, it will come back the other way in pretty short order.

Brett

FLOYD CARTER · « **Reply #8 on:** January 07, 2015, 12:15:50 PM »

In my opinion, people who insist on "front-line-up" are beating a dead horse! I've built both ways, with no difference. In fact, a couple of my very best stunters have the rear line as the UP. I make my line adjusters so the lines are very close, without snagging. Maybe that's the best way.

Floyd

Istvan Travnik · « **Reply #9 on:** January 07, 2015, 04:17:42 PM »

Dear "DOC" John,
Thanks for the nice mistake of you: sorrowfully Igor is the reigning WCh, not me

Istvan

Target · « **Reply #10 on:** March 21, 2015, 10:21:50 PM »

I saw an old design, "Angelique" I think it was, where the lines were shown to be on above the other in the wing tip.
Seemingly, that is not popular, but it seems to be a solution to this debate, of which I know nothing (I'm a newbie!).

Has anyone tried that arrangement?
What were the results if so?

Regards,
Chris

Tim Wescott · « **Reply #11 on:** March 21, 2015, 10:31:07 PM »

Quote from: Chris Behm on March 21, 2015, 10:21:50 PM

I saw an old design, "Angelique" I think it was, where the lines were shown to be on above the other in the wing tip.
Seemingly, that is not popular, but it seems to be a solution to this debate, of which I know nothing (I'm a newbie!).

Hey Chris:

I haven't tried it. You see it on some older designs, but I don't know of any current designs that use it. Like a lot of things that have been tried, if it had a stunningly positive effect on flight performance (as flaps do) then you'd see it everywhere (like, for instance, flaps).

I have a strong bias toward not sweating too much over fine details until it actually makes a difference in your flying. The guys who really seem to see a difference in the placement of the up line are people who are at the absolute top of the stunt world -- so unless you're a strong contender in Expert, I'm not sure that you have any reason to sweat it.

And, if you make your leadout guides right, you can experiment with both ways and see if you can tell.

Target · « **Reply #12 on:** March 21, 2015, 10:44:55 PM »

Thanks for the speedy reply, Tim.
I sort of determined that same thing (vertically oriented lead outs) since I only saw that one plan with them, and it wasn't anywhere near current. Nice to see outside of the box thinking though....
Completely understand what you're saying with regard to it being such a fine detail; its the same in all facets of all hobbies I think. It is in RC sailplanes, that I know from experience.
Still, for me at least, I LOVE the theory of all of the details, especially aero-design details. Its brain food for me.
Have a great weekend.
Regards,
Chris

Allan Perret · « **Reply #13 on:** March 24, 2015, 07:26:31 AM »

What about both lines exiting a single hole in the wingtip ?

Would require connectors to be staggered, but that's doable..

Target · « **Reply #14 on:** March 24, 2015, 08:39:36 AM »

That sounds like it could end in a problem (at first thought). The lines could get twisted inside the lead out and bind up, I would guess?

Avaiojet · « **Reply #15 on:** March 24, 2015, 01:26:28 PM »

Quote from: Chris Behm on March 21, 2015, 10:21:50 PM

I saw an old design, "Angelique" I think it was, where the lines were shown to be on above the other in the wing tip.
Seemingly, that is not popular, but it seems to be a solution to this debate, of which I know nothing (I'm a newbie!).

Has anyone tried that arrangement?
What were the results if so?

Regards,
Chris

Chris,

We had leadouts over and under as far back as the early 60's. We put them on the CG and none were adjustable.

None of us flew well enough to see the advantage or disadvantage.

It is possible to have the leadouts over and under with the ability of independent forward and rearward adjustment. Some wing tip ends are thick.

I was giving that some consideration recently with my current stunt design. However I'm old, and I'm lazy.

Possibly something to consider for the young at heart or the competitor. Give it a try!

Speaking of competitors, what are the world champs doing?

Trostle · « **Reply #16 on:** March 24, 2015, 01:57:26 PM »

Quote from: Chris Behm on March 21, 2015, 10:21:50 PM

I saw an old design, "Angelique" I think it was, where the lines were shown to be on above the other in the wing tip.
Seemingly, that is not popular, but it seems to be a solution to this debate, of which I know nothing (I'm a newbie!).

Has anyone tried that arrangement?
What were the results if so?

Regards,
Chris

Bob Palmer had his leadouts one above the other on most if not all of his Thunderbirds. Palmer also used the idea on his Skyscraper I am pretty sure he used that when he won the Walker Cup in 1955. Bart Klapinki (one of the true Golden Arms) did it with his Tempest when he won in 1967. Bart's Tempest is closely related Dick Williams Electra from the early 60's. (Dick Williams was Bart's mentor.) The Electra and several other descendants of the Electra by top fliers in Southern California from that era used over and under leadouts. That was one of the many things that Bob Palmer advocated and seemed to work, at least not in a detrimental way.

It is one of those things that is not needed to have a Nats winning airplane, just like the Rabe Rudder idea. For some people, such innovations might seem to help, but at least, they do not hurt anything.

Keith

Allan Perret · « **Reply #17 on:** March 24, 2015, 02:41:10 PM »

Quote from: Chris Behm on March 24, 2015, 08:39:36 AM

That sounds like it could end in a problem (at first thought). The lines could get twisted inside the lead out and bind up, I would guess?

Not really, think of a single 1/8" eyelet of some sort with a small wire pin thru the middle dividing it into 2 openings side by side.
That would prevent any internal twisting.

Randy Powell · « **Reply #18 on:** March 24, 2015, 04:51:07 PM »

I like having individually adjustable leadouts and usually have the "down" line in the front. Maybe it's just that I know how to trim it configured like that.

Chris Wilson · « **Reply #19 on:** March 24, 2015, 07:54:40 PM »

Quote from: Allan Perret on March 24, 2015, 07:26:31 AM

What about both lines exiting a single hole in the wingtip ?

Stanzel Monoline?

Tim Wescott · « **Reply #20 on:** March 24, 2015, 08:24:22 PM »

Steve, have we pulled this thread far enough off track yet? Or should I mention politics, or supporting evidence that the Apollo moon landings were faked?