Official Freewing F/A-18C Hornet 90mm EDF Thread

[fredmdbud]

In the case of the flaps, unplugging won’t do anything in the up position because of the leverage from the servo to the hinge. And any aerodynamic forces that would move the flaps down would be from tumbling, not flying

[Hardway]

[fredmdbud]

1. Consider the air flow - with the flaps up, that is the position of least aerodynamic resistance. Any aerodynamic force from flight would would tend to push them up (drag, lift), especially due to their area (thus the rationale for using higher-torque servos on them). And the flaps have a "hard stop" that prevents them from defecting up.
2. And consider the force required to move the flaps. With the servos unenergized (battery unplugged), slowly apply pressure and roughly see how much it would take to move them. Then consider the direction of the applied force (see #1).

[Hoomi]

Well today was interesting. I took mine out and was taxiing when suddenly the flaps started "flapping" up and down very fast like it was possessed! In all of my RC years I have never seen anything like it! No clue if it is the BB or servos or what?! So I unplugged the flaps from the rx and flew without them. Ugh, gremlins!!

Mighty glad it happened on the ground, and not once you were in the air!

[Aros]

Not sure what ya'll mean with unplugging from the rx being a problem? No more flap signal, no more problem. What am I missing?

[Aros]

Mighty glad it happened on the ground, and not once you were in the air!

Amen brother!

[Phantom]

Not sure what ya'll mean with unplugging from the rx being a problem? No more flap signal, no more problem. What am I missing?

I believe they are referring to an unpowered servo doesn't neccesarily hold position like a powered servo. With the flaps I agree with the consensus here, it having a mechanical stop up, and the resistance from airflow underneath the wing creating high pressure there really should be no reason your flaps will change their position in flight.

However having a control surface such as the rudder, or say one aileron working, so you unplug the bad one and decide to fly on the good aileron, I've seen it done, without a servo holding the control surface in place can allow flutter, especially at high speeds and can be catastrophic.

[fredmdbud]

Well today was interesting. I took mine out and was taxiing when suddenly the flaps started "flapping" up and down very fast like it was possessed! In all of my RC years I have never seen anything like it! No clue if it is the BB or servos or what?! So I unplugged the flaps from the rx and flew without them. Ugh, gremlins!!

In my experience, especially with the blue box, if a servo is starting to go bad, servos Y'ed with it will also exhibit erratic behavior. I'd hook each separately to a servo tester and do cycles for a minute to see if one or both are jittering.

In my case, I was cycling the ailerons using the blue box, and both started to jitter, then after a minute they stopped working. Testing each separately, I found one had died completely.

[xviper]

Not sure what ya'll mean with unplugging from the rx being a problem? No more flap signal, no more problem. What am I missing?

I must be missing something, too. I don’t understand. With the flaps in their neutral position and unplugged from the RX, they’re not moving unless you hit something and then, you’ve got bigger problems. Power dive? They’re not moving. Huge wind buffet enough to move them? Again, you’ve got bigger problems. Moving them by hand with the plane unpowered takes more force than any in air condition could muster. It’s not like you’re flying it all the time like that, just that occasion just to get another flight in. If you were to leave them unplugged permanently, sure, I’d secure them in some way so as to clean it up a bit.

[Carlbrainiac]

Heres my 2nd flight after the maiden

https://youtu.be/KohdsHnafqw

All completely stock and flown on Admiral 6000s

[Evan D]

I'll stand by my statement that unplugging a servo without securing the surface is a bad thing to do.

[TiredIronGRB]

I'll stand by my statement that unplugging a servo without securing the surface is a bad thing to do.

I agree, air will push a "free" control surface...I would use a "T" pin to hold it in place.

[Evan D]

Blue Angel day today.

[Hoomi]

Blue Angel day today.

You need a BA A-4 to round out that fleet!

[Evan D]

Yes I do!

You need a BA A-4 to round out that fleet!

[fredmdbud]

Re: flaps - the flap control rod has to “push aft” to deploy the flaps. At least on my plane, I have the servo arm set so that it is flush with the wing when flaps are up, pointing towards the front. Any forces that would try to move the flaps down would also have to overcome a servo arm that is positioned almost directly opposite to the force transmitted along the control rod.

Bottom line up front, Aros flew without incident with his flap servos disconnected until he could replace them. RC field expediency. I would have done the same thing.

[Evan D]

Again it does not take much force to move a surface. If you set up the F-18 by the book the flaps are not all the way up physically and could be moved up or down. That he flew without incident is besides the point. He didn't know better. That you now know better and would still do it is par having read other things you post... Just don't tell others it's a smart thing to do. It's not.

[fredmdbud]

This is arguing about absolutes and hypotheticals. I personally have yet to see a mechanically-restricted flap "flap in the wind" except in the case of a broken clevis/linkage - I've flown my 90mm T-45 flaps disconnected, so it's not new to me. But opinions have clearly been expressed, everyone proceed at their own discretion.

[Veltro]

I just received my gray F/A-18C Hornet in the mail today and plan to do the Navy's VFA-94 Mighty Shrikes livery on it. I saw Youtube vidoes discussing 3D printing for the various armaments and wing loads and would like to find out more and get copies of the files if they exist. Any help in this area would be greatly appreciated.

Hi Ken. Welcome to the Squawk.

I believe so far, just about everything seems to be from the 90mm F-16 ordnance set. "Dirty Dee" has print files for an excellent sidewinder that are free to download. I believe he will also print them for you at a very reasonable price. Here's the link:

https://www.thingiverse.com/DirtyDee/designs

Jay

[janmb]

Not sure what ya'll mean with unplugging from the rx being a problem? No more flap signal, no more problem. What am I missing?

You are missing the fact that without the servo powered and commanded, external forces (aerodynamics and Gs) may move the surface into a position you really don't want it.

A disconnected servo can't be considered "locked"