flyncajun

Brian Have you had success with this method? or ,are we using Marks Airplane as a test subject

I think Mark stated he added positive to the Wing at one point, I know this from flight reports , and here is where his problem probably started.

If he had a thrust line issue with a bipe ,from experience I can tell you he would have a roll coupling on knife edge. Because if the bipe wing separation is not equal there will need to be either anhedral on the top wing ,or dihedral on the bottom wing. So in my mind I rule that out. I also carefully watched his flight videos I can see his problem.

Sometimes, like I said before you chase one problem (I`m privy to) a pull to the canopy on knife edge, and you think you fixed or helped that problem (by adding inc. to the lower wing), in the excitement of potential progress ,you didn`t realize you created another issue. You chase that issue endlessly before you realized it was caused by the so called fix. (remember I said a real fix, will fix multiple issues it will never create another one, or fix just one. You cannot blindly pick a pet hypotheses and ride that pony into the sunset. First you have to gather all the facts given separate the possibilities, and formulate a direction from an educated and experienced approach. I know, I know, I sound like a mechanic

His problem is a classic symptom of over adjustment of wing inc. on a bipe. coupled by either asymmetrical stab half , and overadjusted engine thrust . throw a forward cg in the mix POW! ( I also know he running the cg forward) A real fix would adjust the elevator trim to keep the airplane happy when the wings are unloaded ( up lines, knife edges ,down lines) vertical cg will not help knife edge problems since we know he still has a knife edge problem, he has not really helped his problem just over rode it with a Band-Aid ,then the problem manifested itself elsewhere.

SO,to get to the bottom of the problem we need to measure, first we need to have exact Numbers of where his settings are wing inc. C/G. thrust or we cannot proceed by throwing out random suggestions. measurements to the tenth of a degree is required. and a perfect measurement of cg. and part of the problem is he has flying stabs so now, things get a little muddy how do you accurately measure where the elevators are trimmed, One of the biggest( tattle tail )aids in trimming a model for this very problem.

Bryan

serious power

Hi Bryan,
I'll take the 2nd part of your opening question first.
Mark is not the first person on here to raise the subject of CG in the vertical (the height dimension).
I did and do encourage Mark to do some testing of this.
By doing so he might even end up with a vertical CG position similar to your glow alferma - seriously though he may get a benefit or learn that he won't.

The answer to the first half of your opening question requires a history resume and a longish post - later

Brian

flyncajun

Brian, OK,


I understand and don`t take this the wrong way, I`m not trying to be cute.

But ,you can make any hypothesis come true with figures and numbers , the proof is in the outcome and application of the experiments.
How is it that I can trim and fix airplanes all over the world without ever flying them? from experience and understanding of the problems and corrections. if you would ever see how well thought out and complex My trimming guide is even you would be impressed. not the written one the flow chart I sell.
In these debates I never stutter, back peddle, or waver in my advise, yet no one has ever called BS on me , Ever wonder why?

I just laid out 90% of the answers you've been looking for on Bipe trimming and you glossed straight over it, to continue to make your points, this is why I don`t give it all away in one shot. There is free and pertinent advise in my last few post and lies almost all of the answers, (if you can piece it all together) you would be wise not to disregard it The draw back is, it will require Many re designs and fixes on many current models.

My glow Allure is setup just like the contra Allure and my Electric Allure ,Not once have I ever used or considered vertical CG. they fly Identical I never worried about vertical cg.
As for My Glow Alferma , if he were to try to set it up as such. he would have to go the opposite direction of where you are trying to lead him Further , you are talking to some one who has designed two Bipes one very successful Bipe of that bipe 3 versions now (near Perfect to mine and Bretts standards not George Washington's) I`ve Advised and fixed Many other Bipes around the world top pilots, with never asking them to check vertical CG. glow and electric. I also designed 20 + mono planes in the last 28 years so you could say I was an authority on the subject The information did not come from reading other post or, from typing away at the keyboard LOL. I`ve seen this subject batted around many times no body ever said Eureka ! there is no moment of enlightenment down that trail. if there was we would have the advise , correction and an explanation here already ,your still postulating a conclusion with no testing!

I wise man once said if you can`t explain it simply you don`t really understand it.
I`ve laid out all the don't s and left the do`s in a tight window. you could say I understand it completely.

Look I`m not trying to toot my own horn, but you know the saying, you can lead a horse to water?

Let`s review
1Cg is given and settled on a design due to the efficiency/ deficiency of a wing or set of wings. add inc to said inefficient wing ,create other problems.
2Down thrust and asymmetry will create the need for a more forward CG this creates more problems. compounding
3 the purer , straighter the set up the farther back you can run the cg with fewer to no mixes and,this solves some of the above problems
4 adding pos inc may overwhelm the ability/ capability of the setup ,or wing platform and cause other issues that you think are design problems.
5 I privately gave you the magic CG but I made you guess
6 you may have to cut or redesign the plane for satisfactory results no one is willing anymore to do it especially on a 6000.00$ airplane
7 don`t bother with vertical cg.
8 I think we scared away Mark sorry
9 (big clue here!) different sized wings will not cure the problem but make it worse, especially if one incidence is set negative to the other.

ever wonder why some bipes run a recommended cg of 18-20% ?

I know it`s fun to postulate and calculate , But I save that to understand the issue after I find the answers , it`s faster that way for all of us.
There are Many Many other factors that trump your suggestions on it`s face, I just layed them out, but I welcome the testing and reporting it will teach many lessons. but be a big waste of practice time.

I remember a similar debate about spiral slipstream and the contra ,I was not in line with the thought process because I know the answer after proving it with my designs Of coarse nobody ever comes back and Says Dude , you were right!! and I don`t expect it, it does further the hobby but people forget where they learned it and times marches on. But just once after being right so... many times, it would be nice to take my road first, and save yourself some grief

I like to say everybody`s expectation and perceptions of perfection is different and based on experience and ability. I can Assure you mine is probably the highest when it comes to design,and being so, I have gathered the most answers

I came really close to flat out disclosing the answer to bipe perfection here But, you will have to keep reading between the lines although I just fleshed it in a good bit . Now find your saw

Bryan

serious power

Bryan,

Both you and I were at this game when the models were so small that the equipment nearly did not fit inside them.
You may even remember the pipes on the outside and then the first 4 stroke motors hanging out of the front.
As with all things the models have been 'evolving' all the while and this evolution really took off with the advent of the 5Kg/unlimited engine rule - a bit like the evolution of life here really took off straight after the Snowball Earth phase .
Anyway the models started getting much bigger and continue to do so right up to this day.
They are so big now that it is very likely that one could take all the radio gear out of all the models at any local comp,, and chuck the lot of it into one Fuz,, and not even fill the thing .
Also we have had the relatively recent advent and development of electrics in F3A.
However the majority of the model 'design evolution' that happened has happened around the glow installation NB . Of course this is mostly driven by the top pilots and an occasional designer , but not entirely.

So at all times, right up till now, the best and most current designs were/are subtle evolutions of those from immediately before them, which were also subtle evolutions of those before them - and so on.
As I said already this has been, for the most part, around glow.
This has resulted in models that are as good as they can be, at any given moment in time, in every regard ; Finish, weight, size, form, wing area, tail area, fin/rudder area, power, noise, CG, etc etc etc .
This includes, for glow models which have driven just about all the development till 'now', inverted engines c/w exhausts, thrust line, wing position, wing height and 'vertical CG'.
None of what we have now just magically appeared - it evolved, bit by bit by bit. Aesthetics lurk in the background all the while also and are a minor driver of form.

Now however we find ourselves with two new kids on the block ;
- Electrics (including contras) c/w their big battery packs.
- Enormous, cavernous, very deep and quite wide Fuz's.

To the first part of your question;

Firstly I would not describe this as 'a method'.
It is, or can be, an extra/new adjustment that we can use - if we wish - all be it within a small range (I'll post separately re this)

About 6 or 7 years ago both Niall and I were preparing two new Prolines.
These were made for glow but we were putting Pletty's in them.
To save weight we were removing, completely, the canopy floors (net saving 60g - still remember that also). We had arranged for the canopies to be packed loose.
At that moment we could have fitted the canopies as removable and put the packs inside or we had the option of under-slinging them in the belly pan (one piece wing etc).
As we discussed this I passed the following comment to Niall ;
' We're going to have to start thinking about where to install all the stuff in these things - they're huge from top to bottom '
There was only a rudder servo, receiver and a mini lipo in the area above the wing when we finished - it looked lost.
Anyway I checked the vertical CG with the pack in both places (inside and/or under-slung) and with the pack under-slung the CG was 6mm above the wing centreline at the root - happy days .
So we moulded c/f trays and mounted them there.
That was the first time I made a conscious choice that affected the CG vertically.
I did the same test with a pair of Zeque's.
Then came the bipes, 3 so far and I found these were best with the pack as high in the Fuz as I could get them.
The last two have the radio tray as high as I could get it as well - it's the best rolling model I've ever had.
Verticals are dead straight (no mix ) under power.
I moved the battery tray up and back in the first few days of flying these, or in the case of the last one installed it high to begin with.

So ; 1 Yes and 2 No
Talk later.

Brian

serious power

Bryan,
I took a tea break , mid post, so just posted without seeing your last one.
I'll read it now.

Brian

serious power

' I just laid out 90% of the answers you've been looking for on Bipe trimming and you glossed straight over it, to continue to make your points, '

Hi Bryan,
As they say around here ; ' Stall the digger '
I was simply and politely returning the thread to Mark - picking up where he left off.
Then I was answering directly (all be it slowly - family arrived home here ) the questions you posed at the start of your post.

I assure you I glossed over nothing. I never do
Actually I've been reading better from between the lines than you may realise.
It's just that when 'it's between the lines' a response is awkward/tricky to give.

What saw ??

Talk later
Brian

flyncajun

Ok

I talked to Mark and apologized for hijacking his thread So
I`ll leave it at that

I was never trying to be cute just care full. have fun!
Now back to the previously scheduled show
May be, there were some pearls collected in those riddles

Bryan

serious power

Bryan,
All good
At the heart of every pearl is a grain of sand !!

I will , just for the hell of it, flesh out some thoughts on this VCG stuff.
If nothing ever comes of it - well - cest la vie !!
These models are fast heading for 0.5M in depth.

Brian

serious power

' That will move the CG up by approx 5mm - significant considering the effect of the lead.
Though you may have reduced the drag some low down at the tail and increased it some high up at the tail (and or a small aero effect - at the extreme of such a long lever ??) !?? '

Hi Mark,
I could have phrased the text (in blue) a little better, and or it may have have got shrouded in smoke
I was referring to the moving of the lead from the bottom to the top of the fin and to the way it's presented to the air flows involved. (see below)

Getting back to the subject of vertical CG ;
Firstly, considering how sideways we got, I thought it a good idea to remind ourselves of some basics/fundamentals and or where we came from.
I am trying to keep it simple and relative to the subject of vertical CG.

The two outline sketch's (excuse the quality) below are a good reference point and relate well.
I am, for simplicity, just focusing on wing position and CG and the corresponding reactions/interactions.

Take the high wing trainer.
This has the wing placed 'high' above the CG so as to introduce stability for upright flying. Dihedral increases further the height/distance above the CG. That's height relative to CG verticaly !!
The greater the distance the better the stabilising effect. Old hat.
This is even though the wing (the lift) and the force exerted by gravity remain constant.

Now take the 'old school' low winger.
To keep the comparison fair we will take the wing from the trainer, c/w it's dihedral and semi-symmetrical section, and put it on the low winger.
We will also keep the moments etc the same.
It will have lost most of the inherent upright stability the trainer layout had.
This is mostly due to the CG now being a relatively large distance above the wing (centre of lift). Obvious really.

Now let's take a modern pattern plane.

1st a quick look at a fundamental issue that sometimes arises ;
- A model, mono, that rolls with or against rudder when it's applied.
This is generally accepted as a dihedral problem. So we'll take the eg of one that rolls 'with' the applied rudder.
The correct fix is to cut the wing (or make a new one) so as to correct the dihedral.
To correct the 'roll with rudder' we need to reduce the dihedral ! Simple !!
However what reducing the dihedral does in this case is to increase the distance between the CG and the mean wing position.
That's the distance vertically. Lowering the entire wing would also work as would moving the CG up (might cause another issue )
So the vertical CG is very much in play.
Hardly a surprise, it even works on a trainer .All be it that we exploit it a little differently !

The modern pattern planes current design is standing on the shoulders of those that went before and whose designs also stood on the shoulders of those before that.
As alluded to, in an earlier post, inherent in the decisions that drove these 'evolutions' are all the fundamentals that are/were in play.
Such fundamentals as; sq,, areas, moments, tapers, sweeps, thrust lines, wing heights, tail heights etc.
Also inherent in the decisions that drove these evolutions is the CG, and in all dimensions.
Decisions made with regard to, thrust lines (engine positions), wing heights and tail heights are in fact made relative to Vertical CG, in that they relate to each other through the CG.
Some designers are very conscious of this and others just know that they relate. I suppose not knowing 'why' makes no difference provided one knows 'how' !!?
Cumulative experience gives us what we have today ; That is a very large degree of uniformity in terms of these fundamentals.

Also, as said, nearly all of this has happened around the 'glow' installation as it also evolved.
Not to be forgotten is that this was almost exclusively on the Mono platform. (I omitted this yesterday, so there are three new kids - not two - electrics, huge fuz's and bipes )

This leaves us with the current glow, mono.
Up to now everything in and/or on one of these has had it's place, predetermined by the the design, all be it just a design from an evolutionary process.
[[ That's exactly how F1 works also. An occasional new idea and a lot of copy-cat development. ( occasional is said in the context of the 10's of €1,000,000's they pay for new ideas) ]]
Even if one wanted to test/play around with vertical CG, on any given model, there was very little scope to do so. Maybe move the RX pack up or down a little - or - add the dreaded lead !!!


A btw, is that all or most of the discretionary installation is centred to keep the mass at the extremes as low as possible, while attaining the desired CG.
Also that this is done in conjunction with the rest of the installation, for eg aileron servos etc, so that the lateral CG will be centred.
Again this 'planning' of layout has lateral CG 'inherent' in it - it is taken as a given - it's not an option. It's seldom or ever discussed, again because it's a given.
So until recently vertical CG position was 'inherent' in what was planned and not really amenable to adjustment. It had to be designed in, as has lateral CG.

So with all of this in mind we now have to deal with the 'New kids'.
You have two of them; A bipe and an electric at that.

You're model is what it is.
However you have to do the install.
Does it matter what goes where - of course it does - it affects the CG.
There are no or nearly no relevant shoulders to stand on.
If I could tell you what to put where, for the optimum CG position, I would - for sure.
I will, however, try to help some ;
- Lateral CG ; Bang on the centre line - easy but very important - As everything relates to/acts through the CG, so if this is off then everything will be asymmetrical !!! (even I know this )
- Longitudinal CG ; Ask Bryan - I'm not kidding
- Vertical CG ; I honestly don't know for absolute certain, but can say it's not in the wing as there are two wings and there are not two CG's
I suggest you move it up to or towards the MAC to start with. (Maybe more later )

Just shooting the breeze - maybe some food for thought.
Have fun.

Brian

Holystone

Hi Mark
I know you are flying and focusing on the F maneuver now. and BJ wants me to give you his tips for your F maneuver.
I think this trimming advice is good enough for improving your F maneuver score, please consider it and I believe it worth enough.
Most probably, the F3A flyers are quite conservative, so BJ hesitated a lot with worrying about that people may be consider it nonsense.
Just like in the past, when Galileo Galilei said the earth is round not square, most people blamed him.
I guess this advice will be much more useful then the 1980’s trimming chart of full power and idling with the so-and-so engines and props.

The below sentences is my English translation from BJ’email.
----------------------------------------------------------------------------------------------------------------------------------
Hello Mark.
From my point of view, you look like already satisfied with your Passion but you face only one dificulty of the vertical and KE setting at slow air speed.
Here I give you my tips how to handle it. now your plane looks like need little bit elevator down mixing at KE and vertical. so I suggest you to set your
elevator trim down at KN.

The result will be.
1.No need for elevator down mixing at vertical.
2.Much easier and comfortable at inverted flight and 45 inverted flight.
3.Also have more margin (degree) for snap roll from inverted flight.
4.Easier at rolling maneuver due to no mixing coupling.
5.Can feel that rolling is much closer to the axle.
6.Comfortable landing in strong wind.(due to head down tendency)
7.Weak point is that you have to pull your elevator stick at level flight and 45 up line.

If you follow up the above guidance, of course you will get the worse result at vertical with slow air speed due to thedown elevator trim. Reduce the sideeffects from this trimming.
1.Lift up your battery tray higher as much as you can.
2. Sandyour landing gear leading edge as sharp as you can.
3.Replace your main wheel and wheel pants with the narrow size.

If you still have the same side effects after following the above with slow air speed, you have to vertical up with the general vertical air speed (push the throttle stick a bit harder).

If I were you I would do that setting, I guarantee that you will have much more comfortable at F maneuver. Of course you have to hold your elevator key at level flight.

You lose one, but gain more benefits. If you set your Passion with that, I guarantee that you are much easier and comfortable at F & unknown maneuver .

Only the thing you have to practice is holding elevator stick exactly for the level flight at the field.
I think this is very worth thing to do for the Passion like well balanced, and you aiming for F and unknown maneuver, The total time of level flight is only 20-25% around, as you know the most time, the plane’s attitude are in inverted or KE.
Someone can possibly say “if you follow this guidance, your plane will be perfect”
But, I would rather say, “I can give you valuable advice for making better balance and setting.”
It’s up to you Mark.

I gently suggest that you stay focus on your maneuver and score more, and have to change the point of view how to challege the difficulties.
It’s the year of 2015. If we have more chance, let’s talk about later.

This advice makes sense for the Bi plane and the one with canalizer only.
And one, last thing, some of the world top flyers with Bi planes and the canalized one, they already do this way. It’s not the new one. Good luck.

BJ Park.

serious power

' And one, last thing, some of the world top flyers with Bi planes and the canalized one, they already do this way. It’s not the new one. Good luck. '

Hi,
Seba is /was using this and some other notable European fliers.

Trim the elevator in power off vertical dives !!
Thus up elevator has to be held for horizontal straight and level (not for me).
They call it / nick-named it '0 Gravity' flying !??

I can see/understand how it works.
It get's away, more or less completely, from setting wing incidence and CG for vertical up lines and knife edge - so it has huge merit.

Brian

flyintexan

My Feedback: (1)

Mike, I apologize for what this thread has turned into. You have provided me with a great product at a great price.

Anyone who judged Masters Finals at last year's US Nats, thank you for your time and I would assume from what you witnessed, you might understand what kind of performance I expect to achieve from my own design airplanes. After 65+ flights, lots of thought, and valuable feedback from others who have flown my Passion, I feel that I now have that performance with the Passion.

If you are one of several who have bought an Akiba, BJ Passion, and you would like to know my particular setup, please feel free to contact me privately ([email protected]).

To those that have posted here, thank you for your input.


Best Regards,
Mark

mups53

My Feedback: (41)

flyncajun

OK
This has gone horribly wrong for me I was wrong to jump in on the thread.
I was genuinely trying to help and we went down the dirt road again.

There was no intent to bash the airplane I only was trying to help Mark not chase his tail.
I`m sorry for My post.
Mike, Mark ,and I are friends, I intend to keep it that way. If my attempt at help was taken the wrong way I`m sorry.
I called and apologized to Mike, I was wrong...



I`ll keep my opinions to my self from now on

Bryan

Jason Arnold

Hi Guys,

It has been some time since I last posted on this thread but I have been watching from the sidelines with great interest. The Passion is a pretty sexy looking plane and has a very "reputable" designer behind it. Was somewhat surprised to see Mark buy a Passion but hey, he must have been seduced by it. :-)
It should also be noted that I was the originator of this thread and therefore should have some say. Well, one would think that would be the case but perhaps I'm wrong. Another thing that should be noted is that I have no ties to the designer or the manufacturer whatsoever...

I'm unable to really comment on what was said in the post that upset people because it was deleted before I could see it. I can only imagine that it contained some information that people didn't want made public. If the posts intent was to help people then there should be no problem with it. Some may think the thread has been taken off the subject some but at the end of the day it seemed to be discussing an issue Mark had with his model. That's my view on it.

I have a few personal comments about posts on RCU.
1. Commercial interests should never get in the way of the truth. Often not the case in reality unfortunately.
2. RCU posting rules should be followed. Very important!
3. What we type is read by many eyes so if misinformation is posted, it has the potential to be taken as gospel. We all have a responsibility here....
4. Banter is good IMHO. If you can read between the lines much can be learnt. :-)

Cheers,
Jason.

flyintexan

My Feedback: (1)

I would like to share with other owners of the Passion bipe what the current measurements are on mine. I tried the zero gravity method just for fun and it was good, just not for me. My cg is approximately at the 110mm position. With a meter on the stab and set to 0deg, the other measurements are: bttm wing +1 deg (shimmed at te). Top wing +0.5 (no shims). Downthrust -1.5 (matches nosering ). Right thrust is a touch more than what is on the nosering. Weight with 1150g packs, 45g rx pack, 3 blade falcon: 4900g. I have 2% down with idle. I am using a throttle to rudder mix of 4% right at full throttle, rudder trimmed straight for idle downlines. I was surprised how seamless and well it's working. I have flown in only one contest so far and managed a very close win against a very practiced pilot. He had me by a couple points in the p sequence, but I gained ground in the f to win. Since then I feel the setup is stronger and win or lose I am really enjoying flying the plane whenever time allows.

mups53

My Feedback: (41)

At the contest this weekend in Peoria Illinois I finally got to watch the Passion fly. Bill Ahrens from St Louis one of the finest F3A pilots I know and multiple District 5 FAI champion flew his.
Bill was using the SDC 21x13 3 bladed prop and the speed envelope it flew at was really impressive with the Pletty Advance.
All in all I watched every flight and started to think I should probably start building one for my hanger.
Here is a picture of Bill's new plane.
Mike

mups53

My Feedback: (41)

Guys I have 3 Passion Bipes left.
Two yellow and one Pink.
If interested give me a call and make an offer.
Please don't do it online. And yes I'll ship international for about an added $500 DHL.
http://www.f3aunlimited.com/bj-craft...-yellow-scheme
Thanks, Mike Mueller