Redshift; Used Purchase

[Doc J]

IPA=India Pale Ale?

Thats the one!

But if you can't find any, then Isopropyl Alcohol will do.

Cheers, Doc (Who is only here for the beer)

 

[purview]

today I had lil bit of airtime with my Redshift till the slope forced me to say goodbye.
Redshift is very sensitive to thermals and I can choose if I want go up, or doing it faster, or do some (I am not here) tracking corrections - if I want to stay in that thermal.
By the way this is not what the Redshift likes most. It is a good one and tracks also very well with high banking angle

 

[Konrad]

IT WORKS!!!

I have to admit I had some reservation. But the repaired hinge looks to be working just fine. I was able to maintain clearance with the arms that are now effectively twice as long as those from the OEM. In neutral there is less than 0.5mm clearance This was the ultimate limitation as to how long I could make the V-tail arms. The arms are now effectively 10.5mm maybe 11mm long from the hinge line and the center of the clevis pins. ( I measured the OEM set up as 5mm).

Now I have to clean up the area by repairing the damaged wipers and repairing the damaged surfaces from as received condition. (Ok I added a few dents and tears).

(Yes the clevises are pointed the wrong way in the photos)

All the best,
Konrad

 

[Hank GB Z]

Good Job Konrad,

its always nice to see hard work pay off.

Hank

 

[Konrad]

I have to say I hated being as vague as I was. Now that the epoxy is full cured I measured the arm length. I'm pleasantly surprised that they are in fact 11mm from the hinge and the pin. And what really surprised me is that they are the same length with in 0.15mm. All the more so, being as this was done with a hacksaw, files and a hand held drill combined with free style (non-fixtured) glueing to the tail.

What I'm trying to show with this post Is how the "fern head" arm allows the clevis pin to actually be centered over the hinge. This is done to ensure that there is no mechanical bias (differential) in the V-tail linkage. Most arms like those found on the RCRCM Strega are just angle brackets with little thought towards their mechanical function. I think you can see the differences in the arms in post #91.

 

[Konrad]

I guess I should show what not to do. Here I'm showing what one will find for linkage with the RCRCM Strega. Along with the omission of a torque arm the geometry of the supplied arm result in some gross differential. That is more down movement* for any given movement of the push rod. This needs to be taken into account with the servo arms or in the programing.

*With V-Tails it is understood that generally you want about 3% downward differential. But what is shown results in a gross exaggeration of the need!

 

[Wayne]

If we are talking about a v-tail, I'm told that differential is a good thing as the loading on a v-tail is not even for up and down. As I recall you want a little more down throw then up. With this said, I rarely bother with this level of detail, but thought I would throw it in since you love the little details.

Also, when thinking of this, would this differential only be with pitch, and not the yaw? Hmm, possibly an interesting side conversation for maximum efficiency in v-tail tuning.

 

[Konrad]

I think I said 3% is the normal starting point not the 15% or so that the offset shown (RCRCM) would take to get a balanced response. It has been my experience, that the differential is used mainly for rudder, to address the dead zone changing from positive to negative loading of one of the surfaces in a rudder command. Also there is some concern about the very slight adverse roll from the rudder command.

Or put another way both surfaces of the V tail do not respond linearly, when the lift vector switches direction on one of the surfaces.

Now because of the pitching moment of cambered airfoils I try to have more down that up to get that balanced feel inverted (less forward stick inverted). This has nothing to do with the V-tail but rather the wing. I try to add more down in my T, X and V tails.

 

[Konrad]

Wow, how much servo resolution did you guys need to leave behined in the servo? I just measure the control arms on my Strega, and from the OEM they are about 14mm long. With the Strega a 7mm servo arm still ends up with me having to cut way down on the servo motion in race trim.

I'm ecstatic that I was able to get 11mm control arms into the Redshift. Based on my experiance with Strega It looks like I'll need to get the servo arms down to 6mm maybe 5mm long. To get that short and arm looks like it will be another engineering exercise. You guys with the stock 5mm surface control arms, what are you doing on the servo end?

All the best,
Konrad

 

[purview]

Dear Konrad,

I've noticed that the CG that I given to you needs a bit of down elevator.

I located the line of pitch moment where the mass (the split volumes of the ibject where the net forces are drawn and must be connect to) is in equilibrium of not too much tucking and not poisonly overshooting at 103mm itis a few mm before the first chequer block ends

...at least one redshift I know flies well with CG 103mm

(the plane is a bit tricky to set up to suit to my flying style. but I am sure to get it right because the sound of this plane is amazing and I'd like to hear more and hope to get as many flying hours as possible ;-)

I changed nothing except that I had to trim and noticed that 1mm down is now for keep level flying. If you do the dive test than you have to set up within the 0.xx margin to attain your preferred flying. So please keep an eye on centering and mid servo resolution. I should have kept more attention on detail or a pair of eyes more¡

Cheers
Chris

 

[Konrad]

Help!

Guys, the redesign of the tail control surfaces is looking real nice I now have a set of tail flipper that are almost DS stable!
But it looks like I made a mistake last night making up the pushrods.

I intended to bias the servo arms forward one spline (I do this for my V-tail differential and upright/ invert balance). It looks like making push rod rods at 11:00pm is not a good idea. I placed the servo arms 2 splines forward. Because of the radial to linear motion between the servo and push rod. I now have a lot less total up. I had planed on having about 11mm of up.

My question to those that have set up and flown a Redshift, is what is the control surface movement you are using? Is 9mm of up surface enough for both the rudder and elevator (I do like to fly with aft CG)?
I know I’ll have a large reverse expo response as is. I was thinking of programing that out with 35 to 40 expo to start with.

(Thinking I might kink the push rod to move them to the outside of the fuselage. I do just make contact with the aft of the ballast tube at full up servo motion. This kink might shorten the bush rod enough to allow me to come back one spline on the servo output splines).

All the best,
Konrad

P.S.
I need to thank Jonathan Wells for the idea of using the push rod threads as the retention feature. This was key to getting the 4.5mm servo arms!

 

[Konrad]

Chris,
Thanks for the feedback. Do you like the responce of the ship with the CG so far aft as to need 1mm of down (incidence issue)? Some guys claim that they get a snappier feel from the elevator going from a bit of down rigging to up command.

I like to have my ships with no trim offsets. I think it lowers the drag.

Can I ask you what your total "UP" control surface movement is (Rudder and Elevator)?

All the best,
Konrad

 

[Jonathan Wells]

This is what i did on my Schwing elevator.
I used a nut on the threaded rod with the hex ground off, for extra peace of mind

 

[Konrad]

As I think there is little force lifting the push rod off the arm (you might remember that a lot of connectors are just snaped on AKA EZ connector) I think the aluminum threads offer more than enough strength. For a nut, even a tube nut, at an arm length of 4.5mm, I'd have to cut into the spline boss. Now I've seen these bosses split.

I have to ask what is that center pin coming off the servo output? Is it some support or just a way the thread the arm retention screw?

All the best,
Konrad

 

[Jonathan Wells]

The nut/keeper just makes me feel ?.

The shaft is for an external bearing.

 

[Konrad]

Custom made shaft? Bearing buried in the rudder post?

Some detail of the 4.5mm servo arm as found in my Redshift.

All the best,
Konrad

 

[Jonathan Wells]

Yes, I get two types made.

 

[Konrad]

Reading Doc's build guide I see that the elevator is set for 5mm and the rudder is set for 10mm. I assume that means total control throw in one direction is 15mm (Full elevator and rudder commanded).

So it looks like I'll need to make up a new set of pushrods. The way I've made them there is no mechanical adjustment. Should I change that?

 

[purview]

today I broke the fuselage of mine at the ballast shotgun reload station... fuse and ballasttube are now each divined as I predicted so far (.. I dreamed of a new fuselage).

yes 10mm of up elevator is enough, for speed flying I need only 4mm and rudder is 5mm to 8mm (speed and thermal)

your solution is nice, as I only used 30% of servo travel, I should adapt to your linkage with... the wings are okay

have a nice evening I must go to the bed


p.s.: the plane is very critical to both elevator and rudder inputs with too much throws

 

[purview]

Here is the taped landing approach, till the last few seconds I pulled the elevator to the max without response, so due to some circumstances the gliding path was nice but fatal for my glider...