bem

My Feedback: (1)

g) Flight LiPo battery tray for the 10 cell LiPo.

Last in the list to do was mounting the battery tray for the 10 cell flight LiPo battery.
In my old MythoS Pro I made two smaller shelves and although it was simple to do and has worked great it did not give as much possiblility as I wanted to move battery any longer distance forward and to rear.
Galactika is shipped with a glass fibre laminated battery tray that can be used if one want.
But I decided tro make my own tray of Carbon-Herex-Carbon 3 mm sandwich plate. A very light and strong material. One such plate is standard 290 x 160 mm, 3 mm thick and weight 62 grams. I used a plate 250 x 120 mm. I did not weight it but one can calculate weight of the area I used compared to the 62 grams of the original plate area. Original plate has area 29x16 cm = 464 cm2 area, 464/62 grams = 7.48 gram/cm2. My battery tray has area 25x12 cm = 300 cm2 area, 300/7.48 gram per cm2= 40.1 grams
I could probably make it 10 grams lighter if I make lightening holes in the tray.
The original Oxai battery tray weight 18 grams.
For battery tray support I use 2 square carbon tubes 8 x 8 mm across the fuselage supported at fuselage sides with square 2 mm polywood pieces, all glued with slow curing epoxy.
The tray is held in place on the square carbon tubes with electric plastic locking straps, so it is easy to take out the battery tray for inspection of fuselage under the tray, where ESC is mounted.
One thing I noticed when cutting the 8 slots (4 on each side) for the Hacker battery straps is how fast the knifes get blunt. I think i used about 10 knife blade before I was finished. Carbon eat steel.
On top of tray it is two stripes of 30 mm welcro (with the harder side on tray and the softer stripes on the batteries).
I use two Hacker 400 mm battery straps that can be moved between 4 different slots in the tray. For the moment I use the middle slots since I think the battery is probably going to stay about on the middle of the tray to have proper flight CG, so far I have not needed to move the battery any more forward or back to get desired flight characteristics but I have tried the battery in most farward position and all way back to most rear position (150 mm distance) for tests.
I will probably make lightening holes in the battery tray and goal is to get it 10 grams lighter then the weight of 40 grams it has now.


Battery tray rest on two 8 x 8 mm square carbon tubes. The 4 small hardwood pieces is there to lock the tray sideways when the plastic straps are tightened.


Battery tray is 250 mm (9.84 in) long and 120 mm (4.72 in) wide and is made of 3 mm laminate Carbon-Herex-Carbon (originally a 290 x 160 mm plate). It is held in place with 4 electric plastic straps, making it easy to unmount if needed. Where the plastic straps has been cut I have smoothen it with wet sandpaper to get very smooth ends so the LiPo battery can not be punctured by misstake by a sharp end of the cut plastic strap.



ThunderPower flight battery mounted with Hacker 400 mm (15.75 in) welcro battery straps. In this photo I have the welcro straps mounted in the two middle slots, there is also slots to front and rear so battery can be strapped correctly more to front or rear if needed. Total possible travel of battrery forward-rear on the tray can be 150 mm (5.90 in).

/Bo

bem

My Feedback: (1)

h) Galactika transportation cover.

From factory Galactika is shipped with a very nice light blue transportation cover. It is really needed to protect the rather fragile surfaces on the plane, especially the wings and stabs. The whole transportation cover is custom made to fit only Galactika. The material is some soft fabric of two layers, an outer light blue layer and an inside white layer.

The cover has these parts:
Wings: left and right bags
Stabs: left and right bags
T-canard: left and right bags
Fin and tailwheel section: one bag
Fuselage: one bag

The quality of the transportation cover match the finish on the plane in general - excellet quality.
It is embroidery "Galactika" on the wing and fuselage bags.
On some areas it is dark blue thicker plastic material for little better durability and to make it nicer.
The different parts meet and is held in place with welcro lock on the parts.


Galactika dressed up in the light blue transpoirtation cover.


Wing bags. Notice the nice pocket inside one of the wing bags for wing carbon tube storage.


T-canard bags.


Fuselage and stabs cover. Even the tail wheel is inside the bag and has custom fit.

This finish this part "2. Assembly."

Next is part "3. Setup."

/Bo

FinnSpeed

Bo, thanks for the photos again, this is a very clean installation indeed!

I do have a couple of comments though (yet again ) :
- If you turn the Scorpion backup guard around and move it just a few centimeters back, you could get rid of the extra servo extension between the guard and RX. This would lose a couple of grams weight and improve reliability.
- The horizontal antenna is very close and in parallel to the carbon wing tube. This is not optimal since the closeness of conductive material will affect antenna efficiency and shadow it in the worst case. I would move the antenna at least 3 cm away from the carbon structure.

***Risto***

bem

My Feedback: (1)

Hi FinnSpeed / Risto,

Yes, to get rid of that 200 mm long servo cable for Backup Guard would save 4.5 grams.
I mounted the Backup Guard rather forward in fuselage to help prevent the model to get tail heavy. To move the Backup Guard 50-60 mm to rear and that way be able to stick in the connector directly in receiver would not have so much effect on CG, I can always compensate to move the large flight battery slightly.

The horizontal antenna is 20 mm from carbon tube today. I must admit I had some doubt if that was to close, although the receiver has two antennas, one vertically also (Dual Antenna Diversity) so it is perhaps not that bad.
Even if I increase the distance from wing carbon tube it will be in "signal shadow" at some angles so this will not be possible to avoid completly.

Thanks for the suggestions, they are welcome. It is very easy to be "blind" on own "builds". It needs fresh eyes to have a look, and this forum is helpful regarding this as You have shown.

It would be no problem to move the balsa strip down 10 mm so I get the horizontal antenna 30 mm distance from wing carbon tube.

/Bo

bem

My Feedback: (1)

Hi,
I was out yesterday evening (in calmer winds) and started to do some fine trimming of my Galactika.

I flew 10 flights, concentrated only on fine trimming flights.

Some of my findings so far:

1) Horisontal flight - as on rails hands off flying. No trim.

2) Vertical upline - straigt as rocket going up, I could not see it wanted to go in any special direction.

3) Vertical downline - without any down elevator mix it has a slight tendency to go to canopy.
I tested and 2.5% down elevator mix (as seen in transmitter) at stick idle position (break on) gives perfect vertical downline.
I have not decided yet if I will use this mix or not.
There was another guy over at my Galactika datum line thread that suggested I would keep the mix:
http://www.rcuniverse.com/forum/elec...l#post12210047
I have never had a F3A plane that was able to go straight downline without a tendency to go to canopy. But if it should be possible to finetune the plane to use no mix here I want that of course. I do not know how to achieve that (yet).

4) Knife edge with left rudder - perfectly straight. I even made about 5 knife edge loops seen from side so I could see if it moved to belly or canopy during the knife edge loop but to my surprise my Galactika did a beautful knife edge loop as I increased power and added more rudder as it was going more vertical. I have never flown a plane that was making a knife edge loop so beautifully.

5) Now to the problem I struggle with for the moment:
Knife edge with right rudder - it has a clear tendency to go to canopy. Just a little down on elevator and it track beautifully. But I want straight knife edge without any elevator input. I could of course mix this away but I prefer not if I'm able to.
So I was thinking what might be the root cause to this. Obviosly when the wing get unloaded in the knife edge a slight elevator up effect seems to jump in and make the plane want to go sligthly to canopy in this case.
I have read all info I have found about the Triangulation trimming and one suggestion is that moving the CG back could maybe take care of such problem:
"If it goes to the canopy on right rudder knife-edge, the CG is very far forward"
Source:
http://www.ckaero.net/blog/triangulation-trimming-2-2/
(it is at nr 6 "green arrow" list there)
But my Galactika has not the CG very far forward, it is actually slightly behind the recommended 212 mm, and I have tried also moving the battery rather much to rear but did not notice any effect on the problem as I could detect.
I tested with some more positive wing incidence thinking that more lift might be needed and resulting in little down trim that would take care of the knife edge pull to canopy problem when wing gets unloaded but I could not detect any visable effect on the problem in right direction.

I had my Galactika up on the bench this morning and measured the elevator alignment with two long carbon tubes taped to the elevators and I could see they where not perfectly parallel. I corrected that. We will se what effect it may have on the "problem".

There is after the alignment adjustment a 0.1 difference in incidence between left and right stabs, the right stab has 0,1 degree more negative incidence (0.1 degree less angle of attack).
I can not do anything about the 0,1 degree difference unless I tear down one stab front tube and fix this, that I'm reluctant to do. I can not adjust each stab incidence individually, only whole stab as an unit.
But I do have the elevators exactly parallell now that is good to know - see photo below. That is at least a step in right direction. We will se what effect it may have on my next trimming flights this evening.
Could be "small tuft topples large loads"? We will see.



If anyone has any suggestion what I should try to help with the problem that the plane goes slightly to canopy at knife edge on right rudder I would very much like to hear.
I ordered the more detalied Triangulation Trimming guide a while ago but it has not arrived yet from the trimming "Master" himself.
I will check Bryans Triangulation Trimming Guide in detalil when I get it in my mail in a few days. I have read everything on his homepage (I hope) what he has written about trimming but he gives more deltalis and suggestions in his Trimming guide ($30). In the meanwhile I have to use the knowledge I have and understand at present.

/Bo

flyncajun

Bem


I just did a comprehensive overhaul of my trim guide( Third revision ). It is twice as much information and a big improvement over the first guide(second revision )
As I learn more about trimming and designs I upgrade the guide .. you got lucky and are receiving the first of the latest version
All the information you will need and more is in this guide. http://www.ckaero.net/guides.php
U.S.Mail to Sweden takes about 3 weeks

You have found the problem, But, There is no easy solution

Bryan

cartercg

Hi Bo,

My Galaktika does exactly the same, as does Grant's. I have 0.5% down elev with left rudder and 3% down elev with right rudder. We tried different incidences and CGs and could not remove the pull to canopy. Moving the CG back did not fix it and only made the plane track worse. It seems to be an outcome of the design and related to the large t-can. Many bipes have the same tendency. Let us know if you find a fix, but you will probably have to mix it out. It is a relatively small mix. My stab incidences are identical. There was previously an RCU post about purposely changing the inc of one stab half to correct for this. There were differing views. You can try increasing the inc of the left stab by dropping the left elevator sub trim. See if that helps before you consider changing the actual stab incidence which will be a bit of work.

Clint

big_G

My Caelus does this also. I will see if it changed now that I have a 3 blade prop. I will remove the canalizer to see if this helps/hurts k/e pull to canopy on right rudder.

bem

My Feedback: (1)

Hi Clint,
Nice You folllow this thread. It is great to know I'm not alone with my findings, problems and struggle to solve the knife edge problem with Galactika.
Your mix make sense to me, probably the "medicine" also for my Galactica to cure the knife edge problem(s). I might discover if I study more carefully knife edge with left rudder a slight pull to canopy there also but so far I think mine goes pretty straight without any touch of elevator in any direction.
The knife edge on right rudder is easily seen that it pull to canopy, so I would guess that a 3% mix (as sen in transmitter?) would more or less take care of the problem on my plane also.

So You came to same conclusion as I have (so far).
It feels little better that I'm not alone with the knife edge problem with Galactika.
I wonder if Bryan Hebert had a chance to lay his hands on our planes if he would be able to get it mix free.
I think the Galactika problem in knife edge might be a challenge even to him to solve without any mix, despite his wealth of knowledge.
The huge T-canard on Galactika is an extra thing that complicate the trimming process for anyone I suppose.
No wonder his Allure has no T-canard.


It seems maybe inherent in the design.
It would be very interesting to know CPLR's knife edge mix, if any. And if he has a mix free Galactika, or if he use mix where he use it and amount. Maybe a secret he will not tell.
It was another guy over at the tread "OXAI No more??"
http://www.rcuniverse.com/forum/elec...l#post12206637
that suggested I contact CPLR. But I do not dare (to bother a WC with my Galactika "problem").

I probably will not find any other fix then You have found to apply. But the mix solution is kind of last resort to apply.
It feels little like defeat if we strive for a mix free plane. But I suppose some problems is very hard to solve without a mix solution, unless You do not mind cut, carve and change structure on the plane. But who want to set a knife in a shining brand new Galactika? After all it is a WC model and CPLR plane must have come out of same moulds as our Galactika. So... Do we need to fix anything on a WC design? For me - No not much (I'm not flying at that level anyway).
I can live with a mix solution if other option to solve the knife edge problem is to start using the knife and alter things on the plane.
When I get the new latest edition of Bryan Heberts Triangulation Trimming Guide (in a week or so) I will study it carefully to se of I can pick something I can apply for the solution to the knife edge problem. He said I was one of the first to receive his new third revision Smoking hot in other words.

I wonder who will be first with a 3D printed F3A machine or mould - that would be very accurately. All incidences correctly (no misalignments on wing and stab etc).
I was a little surprised i must say that my stabs did not have exactly same incidences (0.1-0.2 degree difference).
Obviously Oxai did not built repetable on all things like stabs since You Clint have not that difference in Your Galactika stab incidence.
If building in jiggs (that I assume they did) and with lasercut parts (or similar exact parts) such difference should not be possible I suppose, but it was still.

If is funny You wrote "increasing the inc of the left stab by dropping the left elevator sub trim". That was exactly what I did at the field this evening when I had run out of things to try. It helped some actually. The knife edge on right rudder is not really as bad as it was before.
I have not applied any mix yet so I will have to experiment more (tomorrow) - I want to strike while the iron is hot so to speak.

/Bo

bem

My Feedback: (1)

Hi,
Back from the evenings trimming flights. It was crowded at the airfield with engine driven parasail (5 of them flying at the same time all over the sky).

The elevator alignment did not help for the knife edge on right rudder pull to canopy problem. Actually on knife edge left rudder the plane very slowly started to roll to the right (but it was very slow on a long long knife edge).
So I had to change back a little to get rid of that.
I also added some down elevator trim on left elevator. It helped a little on the knife edge right rudder problem, see post #32 and #34 above.

I can tell You that Galactika needs a lot of positive wing incidence. I'm close to max possible on the incidence adjusters - see photos below of right and left adjusters as it is today.




I did some more tests:

Full power, trimmed for absolute level flight, and then at the end I slowly decreased power - plane continued on same path, until I turned throttle stick to lowest and brake is activated and also elevator mix (2.5%) and of course the model started to descent. But I think the up/down trust is pretty good and no force is acting on the plane to noticeably change its flight path at different power settings.

Upright 45 degree upline - fine, maybe slight tendence to dive if I let it fly very long at this angle but it should stay on line in any 45 degree manouvre I think.
Inverted 45 degree upline - OK but some down elevator needed, not much but some. I had this on my MythoS Pro also so I'm used to that. I do not know if I want (or if it is even possible) to get a plane maintain an inverted 45 degree upline without any slight down elevator. Perhaps it is possible. But for me I think it is OK to apply just a bit of down elevator in this situation.

I have not tried 45 degree downline, upright or inverted, yet.

I tested some loops just for fun:
It was no wind this evening so it was perfect trimming weather.
I just applied full elevator up and watched what the model did. It did about 7 or 8 loops almost on same track before I aborted.
I have never seen a plane do loops in such consistent circles.
It was fun to watch and I waited in every loop for the heading to start wander in some direction - but it did not.

Galactika is a rather fast plane and it is faster then my MythoS Pro at landing speed for sure. But it is very good control at lower speeds so landings are easy although the roll out is little longer then I'm ued to because of higher landing speed.

I will try some rudder to elevator mix tomorrow on the knife edge right rudder pull to canopy problem.
I might settle for that solution to the problem despite my desire to not use a mix here.

/Bo

bem

My Feedback: (1)

Hi Clint,
Do You know where that tread is about changing one stab incidence only to correct the knife edge right rudder pull to canopy problem? I would like to read it.

It seems I got the 0.1-0.2 degree stab incidence difference (from factory) the right way:

My right stab has more negative incidence (less angle of attack), or in other words left stab has more positive incidence (more angle of attack).
This is basically same (as I understand) as dropping the left elevator sub trim a little (little down on left elevator) as You suggested (and I did, so I increased the effect little more).

It is so small corrections that is needed to get a straight knife edge on right rudder in my case with my Galactika without any pull to canopy.
But it is one thing to get a horizontal knife edge, where very small rudder is needed to maintain height, and to add more rudder for a knife edge loop or similar maneouvre and plane still stay on track.

To get a mix free plane and a plane that flies hands off in horizontal and vertical up/down, and in both right and left knife edge with no deviation to canopy or belly and so on is really a challenge in my opinion (if You aim at perfection).
And to get the plane to stay on track as You apply more throw like in knife edge loop makes the trimming even more challenging.
It would be nice to hear if Bryan Hebert has no mix whatsoever in his Allure(s).
If he has no mix at all I'm really impressed.
Is there anyone out there that has a mix free F3A plane (except maybe Allure)?

I have not reached such level in trimming knowledge that I can understand the root causes on many problems. I rely very much of Bryan Heberts findings and conclusion based on real world testing and his suggestions to correct an undesired behavior.
Although some of his suggestions did not have any effect on my Galactia it seems. But he just can not cover all situations on all planes in universe. I do not know if Bryan work part time on his F3A designs, sales and production these days but if he, as he writes, spend about 90% of his flying time testing his designs to be as perfect as possible and has done so many years one has to be humble when he has gone through all the work to get his finding in writing in his trimming guide and also on his homepage. And he writes himself that he constantly try to prove himself wrong. With such attitude You really feel that the guidelines he gives us is based on solid ground. I'm sure if one read all he has written on triming one can extract also on most undesired flight behaviour why the plane behave the way it do. For me I have some grey areas I do not understand why I get this and that undesired behavior, like my problem with knife edge right rudder pull to canopy. I understand his suggestion how to correct it but in my case it has almost no effect. So for me it is unknown factors that is in effect. If one do not know the root cause it might be improper action to correct. One can guess or sometimes follow Your gut feeling but often there is a small clue that can lead You in right direction.


Two things that would have made the Galactika better for the trimming work would have been:
1) Individual stab incidence adjustment. To have incidence adjustment on whole stab as a unit the factory must make sure the stabs are perfectly same incidence and in my case they are not.
2) T-canard also incidence adjustable. That would perhaps give possibility for a mix free plane - who knows?
Since the T-canard on Galactika is so huge it must have effect on flight behavior in in general and in some manouveres in particular.
And I'm sure it can have not desired effect on some manouvers.
So a plane without a T-canard would probably make the trimming work less demanding since you have one less flight surface to worry about. And Allure has no T-canard and it flies very well so it is proven it can be good flight characteristics without a T-canard.
Maybe You loose some important flight characteristics without the T-canard that can not really be compensated in any other way, I do not know.

It would be very interesting to let several top flyer fly both a Galactika and an Allure (assuming both is set up and trimmed as best possible) and get opinion on the flight characteristics - pros and cons. A good T-canard design against a good no T-canard design.
I suppose we will never get such test but who knows?

/Bo

bem

My Feedback: (1)

Hi,
I have shorten the LiPo flight battery cables on each battery now with total 200 mm (7.87 in) and saved 9 grams
I like such easy weight reduction although it took some hours to do it with resolder the bullet connectors. Well worth the time spent.
I was tempted to get another quick weight reduction by changing to the MK SkyBlue 60 mm (2 1/2 in) wheels to save another 15.8 grams and then I will pass the 5000 gram limit with flying colors: 5020 - 9 - 15.8 = 4995.2 grams. But I wait a little with that.
I have a list in post #21 with more rather easy weight reductions:
http://www.rcuniverse.com/forum/elec...l#post12209182
FinnSpeed also found out another 4.5 grams saving, by moving the Scorpion Ultra Guard battery closer to receiver and that way eliminate the 120 mm servo extension lead. I will do that next.
If I do all in my weight saving list 1) - 6) and the Backup Guard servo lead saving I can come down to 4954 grams now if I want. Change to lighter aileron servos and not use my current sensor to save weight (total 69 grams) I will probably not do.

/Bo

cartercg

I played around a bit with the t-can incidence to see if that would reduce the need for so much positive on the wing. It did not have any real affect. A mix free plane is a function of trimming and design. Some designs will not be mix free no matter how you trim it. A good design will be mix fee or very close. I think the large t-can provides great rudder authority but does cause some trimming issues. So I don't think you will get it completely mix free. It's very close and the small mix will have little to no negative impact. The inherent positive incidence on the wing will always cause the plane to drop when inverted and to pull slightly on the down lines. Those are inherent outcomes with the way we trim modern F3A planes. Don't stress about the tiny mix. I have striven to get all of my planes to have as little mix as possible. Invariably there is a small amount of mix that is inherent to the design. I have not flown an Allure, and it may well have no mix except for some down elev with throttle. It has a much bigger wing, which I expect with no t-can will provide excellent no mix performance.

i have installed my V3 brenner contra drive in my Galaktika. I'll revert when I have had some flights but it may be some time as the wife has banned flying on Mother's Day ��

MTK

Bo,

have you you considered the possibility that Oxai built the stab incidence difference on purpose? Potentially from input from CPLR? With top right rudder, it is believed that the left stab half is flying in clean air and a small incidence adjustment to this half is most effective. CPLR knows that as do many of us that have flown pattern awhile (nearing 40 years here)

Are you you flying with a contra rotator or single prop? If single prop, thrust angle is causing the difference in pitch couple most likely. If contra rotator, wing incidences are suspect assuming there is no thrust angle built in by mistake.

Air is massive and slight differences cause considerable effects; i.e.- It takes very little to cause a force differential with the model at flying speed.

A cannilizer at mid ships enhances the fuse vertical area at that location. It is no different than adding a vertical fin to the fuse at that spot. Either way, an effective vertical area in the middle of the fuse will tend to destabilize the vertical stabilizer some.. A destabilized vertical fin enhances the rudder effectiveness. Stated another way, if cannalizer is removed the model should become more yaw stable or more directionally stable.

bem

My Feedback: (1)

Clint,

Exacly where are the 3.0% and 0,5% rudder to elevator mix seen that You use? In transmitter Prog. Mixes for the Rudder to Elevator (and Elevator2)?
Or is it percentage of normal elevator throws, like if You have 10 degree throw on elevators it is 3% of that you have down elevator when applying right rudder in knife edge?
I just want to compare same values as You mean.

Do You use linear curve in the Rudder to elevator mix? In my view it might be worth to try non linear curve since I want little more elevator down already at rather small rudder throw since it is required so little rudder in level knife edge flight.

I flew this evening also working with the rudder to elevator mix in knife edge. I have it almost finished now, a very so slight tendency to roll right on knfie edge with left rudder, but it is about 20-30 degrees roll on 600-700 meter knife edge flight. Not much but I will try to solve that.
I will fly more tomorrow.

Tailwheel solder broke today. I had to repair it this evening, two hours work.
It is much stronger solder now then it had originally. I also enhanced it a little by solder a M2 washer at inside tailwheel rim to get better support sideways for the tailwheel rim. The tailwheel is very steady now at the horizontal axle.


Tailwheel washer and steering pin soldered back with much more solder and it is rock steady now. A small washer for better side support of tailwheel rim was also soldered on the horisontal axle.


The tailwheel plastic holder in fuselage had to be slightly countersunk at the end since I reinforced the washer on the metal vertical axle with a servo metal eyelet to get more area for the solder to attaceh to on the vertical axle.


Taiwheel mounted back. I had to add a M2.5 lock washer under the blue plastic lock that holds the tailwheel in place since the washer that is soldered to the vertical axle came slightly higher after the resolder then it was before. I do not expect the tailwheel solder to fail again.

/Bo

bem

My Feedback: (1)

MattK /MTK,
I do not think Oxai build the stabs with different incidences. Clint / cartercg has same incidence on the stabs on his Galactika.
But mine has difference of 0.2 (minus 0,2 more on right stab if Í do not allign the elevators, if I allign the elevators it is -0.1 degrees difference).
I use Hacker Q80-14XS and a two blade prop so no Contra here.

/Bo

big_G

I hope I'm not hi-jacking here, verrrrry interesting, Matt. Thanks for these tid-bits. I am building a second Caelus, which I'm sure will have the same right rudder mix required. I will try a zero thrust / 3 blade prop combo., mixing rudder to throttle as necessary. On the second Caelus, I will study the flight characteristics without the canalizer.. I might just learn something. .

MTK

BigG I doubt that setting thrust angles at zero will eliminate the asymmetric pitch couple. The single prop throwing the air back is doing so asymmetrically. A contra up front greatly reduces the asymmetry but causes other things to happen if there is insufficient vertical stability in the design.

Agreed lets not not highjack the galaktika thread. Bo's model has some issues that He is trying to solve.

cartercg

Hi, I've run contra and single prop in a Peridot and Citrin, and the Peridot with and without a t-can. The contra has little impact on rudder elevator coupling. There may be a small impact, but it is small.

When trimming for KE coupling it is really important that the wing remain perfectly vertical when checking for pitch coupling. Even a small roll onto wheels or canopy will have a big impact on a pull or push to canopy/wheels. I always start by mixing the rudder to aileron to enature the wing stays vertical with all rudder inputs. The key determinant there is the dihedral on the wing. CG also impacts it, as does wing incidence, but they are both secondary impacts. Use a point mix and ensure the wing is not rolling at the rudder inputs required to sustain KE and also the increased rudder inputs for KE loops. my Glaktica needs around 0.5% aileron mix at KE and around 2% at extreme rudder throws. I is not unusual for a plane to need aileron in one direction, and that the direction then changes at increased rudder inputs. If I recall correctly my Galaktika needs a small amount of right aileron with right rudder for sustained KE flight, and at the increased rudder for hard KE corners it transitions to left aileron with hard rudder.

Once the wing is remaining vertical then you can mix the rudder to elevator. As with the rudder to aileron mix, it needs to be a point mix.

finding the points at witch you want to insert a point for the point mix can be a trial and error and take some time. I fly with a futaba 18MZ and what I have found helps is to fly with the mix screen displayed and have somebody write down the rudder input (stick position values) as I fly KE and KE loops. Then insert mixing points at those rudder stick positions. You can then set the mix values at those points depending on what the plane is doing.

The rudder to elevator mix on the Galatika is very flat. The down elev mix comes in at KE rudder input and then remains at that value for the increased rudder inputs. It basically needs the same amount of rudder mix at all rudder inputs. The rudder mix is a percentage of the total elevator throw on your radio. So 0.5% mix is 0.5% of the maximum elevator throw. It is independent on the elevator rates that you fly with. Changing the flying rates will not change the mix.

Will take some photos of my mix screens and post, but can only do so later.

bem

My Feedback: (1)

Clint.
Your answer did really give me valuable information. I had not thought about rudder to eileron mix at all to solve the slight roll to right tendency on knife edge on left rudder. And it is as I suspected that point curve is to be used.
That the wings must be perfectly vertical in knife edge when doing all the trimming I knew before - I fly basically straight over my head on a line so I can se the plane from front and back while knige edge flight to see exactly how the plane is in vertical position and also how it behaves. Good to know the reference for the percentage of elevator down on the rudder to elevator mix. It will be very helful to compare with my values.
It will take a couple of more evenings I'm sure to set up and trim all this now. But I will start today and rest of this week as needed.
I was not expecting so much mixing on the Galactika - I suppose if the trimming Master read this he will say "poor design"...
Well on my level of flying it does not matter that much if some problems is fixed with mixes, but I sure would like as few mixes as possible.
This show how hard it can be to eliminate all mixes that can be needed otherwise. One has to chase all over the map to find where mixes might be needed and if one want to use no mix find how You eliminate it without the mix - that will be a real challenge and maybe require You take a Masters degree in triangulation trimming
And then probably also start carving and changing on the airplane structure. The plane probably need to go into a prototype design stage again and work from there to try to eliminate all the mixes - who knows.

The deeper I dig into trimming the more I understand how little I understood before and still do. I try to be humble, have an open mind and let things take time in the trimming process, it really helps. I have about 50 flights on my Galactika now and most of the flights has been trimming flights. I probably need close to 50 more flights before I will be satisfied and found things I want to correct in the flying.


/Bo

FinnSpeed

Bo, you obviously know more than I about trimming of an F3A plane but I still have a couple of comments.

First of all, avoid overdoing the trimming by mixing since it is possible that you get one thing sorted out but then find that the plane misbehaves in other respects. Often it is tolerable to have a tendency or two that you have to correct by stick input when flying pattern but it is not a problem once you learn where they are. You sort of start to do it automatically when you perform the manoeuvres. Of course a plane that constantly needs correction in every attitude is difficult to fly and that should be avoided by trimming correctly, if possible. Small mixes - let's say max 3 % are probably fine in most cases. If you find that you need a lot more, then it is time to stop and think. I guess you knew this already.

The second thing is that the contra drive removes a lot of non-symmetry from the plane - both in terms of thrust angle and how the surfaces "see" the prop wash. A contra equipped plane will need much less differing mixes on left and right knife edges but since the symmetry is not perfect (the props are not in the same position and the prop wash is still not perfectly free of circular component), there may be some non-symmetry left. Additionally there's the loss of directional stability which must be taken into account in the general design of the plane. Part of this is caused by the fact that contra rotating props generate very little gyroscopic effect compared to a single prop.

cartercg

Hi,

Here are some pics of my Galaktika with the Brenner v3 contra drive with Neu motor. All up weight with hacker 5000 mAh packs will be around 5030g. Right on the limit but I can still run a smaller Rx pack. I'll revert with my thoughts on the Contra as compared to the single prop. Also included some pics of the ruder aileron and ruder elev mixes. Not much to see really as you can't make out the magnitudes, but it will give you some idea as to where the points are and that the mixes are very low.

Battery tray is removable, and spin 99 ESC is mounted underneath the tray. After installing longer landing gear I have a much safer 10cm prop clearance with the 22inch contra props.







Clint

bem

My Feedback: (1)

Hi FinnSpeed,
Good comments. I will keep this in mind. My goal is to use as little mixes as possible.

/Bo

bem

My Feedback: (1)

Clint,

Thanks for the Rudder to Aileron and Rudder to Elevator mix photos. It will be helpful.

The photos: is it the settings for Your Galactika Contra after flight with Contra or is it the settings You where using when You flew Your Galactika with single prop non Contra?

And I suppose You have one Condition for knife edge intense manouvre, so You flip a switch to turn on the Condition just You before You will start such maneouvre, for example before You start F-Schedule maenouvre 11:

F-17.11 Inverted Top Hat with ¼ roll, roll, ¼ roll
From inverted, pull through a ¼ loop into a vertical downline, perform ¼ roll, perform a ¼ knife-edge loop into a sustained knife-edge flight, perform a roll, perform a ¼ knife-edge loop into a vertical upline, perform a ¼ roll, push through a ¼ loop, exit upright.

Your Galactika with Contra looks gorgeous. Very long landing gear - could it be some
negative aerodynamic eftect -drag- with such long gear legs that could influence the trimming for You?

I had not time to fly today (relative's birthday party, training/running, cutting the grass in the garden) but I will probably take my Galactika with me in the car to work tomorrow and on my way home drive to the airfield for some evening flights.

/Bo

cartercg

Hi, I doubt the longer gear will have any noticeable impact. The settings are as for my single prop, and I don't expect will change much. Perhaps a very small mod, but they will be much the same with contra.

i fly the same rates for everything except spins and snaps. So my rudder etc is the same and I don't have to flip any switches other than spins. Snap condition changes are via stick positions. I have enough rudder throw for stall turns, and set the expo to get the feel I want around neutral. The less switches I have to flip the better.