Landing Dynamics

[Matt Piatkowski]

Hello,
Please see the attached.
 
MiniBee lands very well each time. When the wheels touch the tarmac, the plane sticks and rolls without jumps to the stop.
EParrot is not that easy: it takes a very delicate touch to land it well and it has a tendency to stall during landing with annoying "kangaroos" before rolling to the stop.

MPBee is also not easy to land smoothly but a bit better than eParrot.

We all know that the position of the main landing gear w/r to the C.G is one of the main factors determining the landing quality. Landing gear too much FWD while landing on the hard and reasonably smooth surface leads, statistically speaking, to more "kangaroos".

I am trying to understand WHAT causes MiniBee to land so well each time.
I am trying to understand WHAT causes the kangaroos in the eParrot and MPBee landings.

The planes parameters (RTF weights, wings spans, wings surface areas, airfoils, distances between the C.G and the wheels e.t.c.) are available if you need them.

Your opinions are always appreciated,
Happy Flying,
M 

 

[Steve Thompson]

Stiff vs. springy landing gear?

Full stall vs. wheel landings?

[Steve Helmick]

Can't tell from the pictures 1& 2 what the LG is made from...maybe wire? #3 appears to be carbon fiber. A lot of folks around here have had CF gears give bad landings on pavement, and improved that by putting a tensioner between the axles to totally stop the LG from flexing and rebounding. Then, they all had trouble breaking the tensioner wire, even on a pretty smooth landing. This was typically .018" cable, so I guess shock load or stress concentrations were the problem. I don't recall anybody using .027" cable.

I look at CF landing gears and compare them to carbon fiber fishing rods...much different action when compared to a glass/carbon composite rod. While I have not made a CF landing gear, I think that a composite of CF/Kevlar or CF/glass would be better that pure CF. Keeping the weight down becomes more difficult, but a core of some kind of foam sheet seems like a good thing to try.  Making the LG reversible for grass/pavement is a great idea, but takes some planning. Either a 4 bolt pattern or 3 bolt with 6 blind nuts in the mounting plate will work. Finally, with electrics more forward CG's and no CG shift, their LG will have to be more forward than a glow powered plane.

As for wheels, I believe you want a narrow tire and not a lot of rubber...a "low profile" tire...less foam to compress and therefore less foam to rebound...for pavement. Dave Brown Electra-Lite slicks are very good. If you're flying on grass, I like a wide tire with a large footprint...Dave Brown's wide slicks are perfect. Object is to keep the plane on top of the grass as long as possible, and more area to prevent sinking in when it slows...fewer nose-overs.

IMO, you want to "grease it" vs. a stalled landing. Personally, I like a wing mounted gear or an aluminum gear mounted on the fuselage if quality of landing is your goal. It's important to keep the wheels pointed straight ahead and turning, which wire fuselage LG's don't do very well.  A wide track wing mounted gear really helps...you'll land the outboard wheel first, which seems to cut the potential for bouncing tremendously. IMO, there is no downside to this. Steve

[john e. holliday]

Look at the pictures close.  See where the wheels are located according to the leading edge.   In racing I liked the wheel location further aft than on a conventional plane.  With a little down elevator on landing and holding a little down my planes would stick to the pavement.  wheels too far forward will cause kangaroo landings even with down elevator.

[Steve Helmick]

Look at the pictures close.  See where the wheels are located according to the leading edge.   In racing I liked the wheel location further aft than on a conventional plane.  With a little down elevator on landing and holding a little down my planes would stick to the pavement.  wheels too far forward will cause kangaroo landings even with down elevator.

True enough, Doc. But don't ignore the fact that these three planes appear to be electron powered and therefore will have the CG farther forward than a typical glow model with an empty fuel tank. That will then require the LG be farther forward than the same plane with a glow engine.  Steve

[Ken Culbertson]

Hello,
Please see the attached.
 
MiniBee lands very well each time. When the wheels touch the tarmac, the plane sticks and rolls without jumps to the stop.

Look at the angle of attack of the wing on MiniBee vs the other 2.  The reason it sticks is that the angle does not increase much as the tail drops.  If you can slow it to a near stall speed it will stick like glue with a small amount of down elevator.  Gieseke introduced me to this concept and all of my planes since take off and land effortlessly.  You can set the controls to neutral and it will take off just under the 1/4 lap and stay at about 1-3" off the ground till you tell it to go up and you can land by just keeping the wings level till it lands itself.  If you increase the length of the tail wheel on MPBee by about 1/2" it will probably land better than MiniBee.  Now if you can just find a way to do an effortless reverse wingover - let me know.

Ken

[Target]

Mini bee has the wheels closer to the cg, it looks to me. I wish you'd have taken the pictures just a little further forward on each plane. But the pictures are very consistent.
If the tail wheel lengthening helps, please post.

[Ken Culbertson]

If the tail wheel lengthening helps, please post.

It will help but I forgot to add the Surgeon General's warning.  You have to be careful not to make it too tall.  The rules require that the tail wheel does not touch down before the main gear.  It takes a little practice to learn to land hot so that the main gear touches first or 3 point which is what I do, but once you have the hang of it it is like landing on fly paper.

Ken

[john e. holliday]

I read that part 13.15 several times and still wonder, isn't the tail wheel part of the landing gear?

[Ken Culbertson]

I read that part 13.15 several times and still wonder, isn't the tail wheel part of the landing gear?

14:37.10

It is a poorly worded rule.    The "tail wheel" or "nose wheel" touching first is implied in the rule but explained in the judges guide. "Main Wheels or 3-point landings are permissible" implies that the tail or nose wheel is not a "main wheel".  Somehow I think that the people that wrote the rules were not the same ones that wrote the judges guide!  IMHO If it is a "Critical point:" in the judges guide it should be listed as an "error" in the rules!

My guess is that a lot of fliers, even serious ones,  have never read the judges guide.  I am sort of sensitive to this particular "rule"  because I use the Gieseke tail wheel and you have to learn (it is not hard) how to make a smooth 3-point landing.  Letting the tail wheel hit first and pull you down IS an error.   There was quite a flap about this in the 70's.  I remember some rather heated discussions between some rather well known fliers. 

Ken

[Matt Piatkowski]

Thank you for your responses.

I will raise the tails of eParrot and MPBee by 0.2" by bending their tail gear wire forward and fly trying the three-points landing. Right now only one landing in five for these planes is, in my opinion, acceptable. If I can get, on my skill level, 50% of reasonably good hard surface landings, I will consider the issue solved. The rest is simply flying, flying and more flying.

If raising the tails does not improve landings, I will move the main landing gear in MPBee aft about 1.25". This will require another plywood piece with the blind nuts and the reinforcements. Weight penalty about 10 grams. Please see the attached. I have already opened the bottom part of the fuselage that is permanently attached to the wing and the place, the access and some supporting plywood structure is available. The MPBee wing is removable as one piece.

I will install the carbon composite main landing gear in eParrot in the location 1.2" aft from the current gear. I have the attachment points already there.

Hi Steve. Indeed, the structural damping in the carbon composite beams working in bending is poor. Tensioner? Like you wrote. Perhaps the damping can be increased by using some tape glued on both sides of the LG beam? The glue, especially a bit gooey, absorbs the shear stress and this disperses some of the energy. Let me experiment.

Yes...MiniBee and eParrot have now the landing gear made of steel wire. I had to add additional struts to make these LG stiff enough to avoid shimmy. There is another thread in which I described what I did.

Happy Flying,
M

[Trostle]

14:37.10

It is a poorly worded rule.    The "tail wheel" or "nose wheel" touching first is implied in the rule but explained in the judges guide. "Main Wheels or 3-point landings are permissible" implies that the tail or nose wheel is not a "main wheel".  Somehow I think that the people that wrote the rules were not the same ones that wrote the judges guide!  IMHO If it is a "Critical point:" in the judges guide it should be listed as an "error" in the rules!

(Clip)

Ken

OOPS!!!

Let's go back to the basic rule for the landing, Paragraph 13.15.   There is nothing there that says that letting the tail wheel touch first is specifically an error other than the statement that "Main wheel(s) or three-point landings are permissible."  This sort of implies that maybe the tail wheel should not touch first, but it is not so stated.  Now, let's go to 14.37.10 which is part of the "Judges' Guide" and states that a tail wheel touching first during the landing is an error.  The wording in the entire Judges' Guide essentially came from an earlier version of the FAI F2B Judges' Guide and that wording obviously does not match anything specifically mentioned in our AMA rules.  When this Judges' Guide was adopted from the old FAI rules, a major effort was made to purge inconsistencies that were inherent between that FAI wording and our AMA rules.  It took several rules change cycles to accomplish this.  Obviously, this is an inconsistency that was missed.

There still may be more such inconsistencies.  That is why Paragraph 14.1.1 was added to the Judges' Guide:  "The maneuver descriptions and maneuver diagrams of Paragraph 13 take precedence over any difference that might appear in this Judges' Guide."  There is also the statement in 14.1 that "The information in the Judges' Guide is strictly advisory and does not define any rules or requirements of the event."

The ambiguity of 13.15 regarding a tail first landing and the inconsistency of 14.17.10 should be and will be addressed in the next rules change cycle which starts in January 2019.  After this rather "quiet" CLPA change cycle (2017-2018), there is a growing list of topics that the Control Line Aerobatics Contest Board will be addressing for the next change cycle.

Keith

[Ken Culbertson]

The ambiguity of 13.15 regarding a tail first landing and the inconsistency of 14.17.10 should be and will be addressed in the next rules change cycle which starts in January 2019.  After this rather "quiet" CLPA change cycle (2017-2018), there is a growing list of topics that the Control Line Aerobatics Contest Board will be addressing for the next change cycle.

Keith

Thanks for clearing that up.  I don't know why but these little things both bother and fascinate me.  I remember the flap over this in the 70's but I can't remember if it was over the actual length of the tail wheel or the realism points awarded and, since we didn't have things like StuntHangar back then it might have been a very local flap.  Glad that this will be addressed.  Given my luck though it will be resolved by making the tail wheel short and the 3 point landing a deduction!

[Matt Piatkowski]

Good news!
Please see the attached.
I have tilted the carbon composite landing gear in MPBee in such a way that the main wheels are now 0.75" AFT (blue line) w/r to the original position (red line) and the hard surface landings improved. Five flights and five good landings: the plane glides, touches the tarmac, sticks and rolls.

I am still considering moving the main landing gear more aft but for now I will simply fly until the winter comes.

Now, I have to fix eParrot's landings.

M
 

[Target]

:-)

[Trostle]

I am still considering moving the main landing gear more aft but for now I will simply fly until the winter comes.

Now, I have to fix eParrot's landings.

M

A general rule of thumb to place the main gear of a tail dragger is to place the axles of the main gear about 15^o forward of the CG of the model.  This assumes you can locate the lateral and vertical position of the CG.  Even if you are not sure of the vertical CG position, you can approximate it as generally somewhere between the thrust line and the wing chord line of the wing.

For really smooth landings, you can experiment by moving the main wheels  slightly aft of that 15^o parameter.

Keith

[Ted Fancher]

Hello,
Please see the attached.
 snip

EParrot is not that easy: it takes a very delicate touch to land it well and it has a tendency to stall during landing with annoying "kangaroos" before rolling to the stop.

snip

Matt, re the EParrot.  Your comments about stalls and kangaroo hops sort of raise a red flag for me.  One of the traits of a proper longitudinal (fore and aft) location of the CG is a "positively controllable" glide.  A smooth controllable glide is a harbinger of a good landing on the way...assuming the relationship of the CG and the "touchdown" point of the wheels are in close proximity to what you've suggested: the wheels touch the tarmac with the fuse level at or near to a point 15 degrees forward of the CG (Keith's comments about the vertical location of the CG are accurate as well but most normally configured stunters will have the vertical location pretty darned close to the middle of the top to bottom location of the wing...if for no other reason than to make the ship fly with wings level in level flight without any aerodynamic gizmos "forcing" the wings to level.

My suggestion (in addition to others comments about gear strut rigidity to minimize "elastic" compression and rebound) would be to move the CG forward until the tendency to stall or balloon into any wind is eliminated and then do the CG to touchdown point of the wheels check.  If you lose desired sensitivity of response in maneuvers simply widen the line spacing at the handle to regain the pitch rates you prefer.

Ted

[Igor Burger]

MPBee is also not easy to land smoothly but a bit better than eParrot.

Compare your LG with MaxBee. I think you have it inch or so forward of MaxBee position. That on MaxBee is compromise between nice concrete landing and safe take off on grass. Better landing will need it little back and bullet proof safety on grass will need it more forward.

[Matt Piatkowski]

Keith, Ted, Igor,
EParrot has 23% airfoil and weights 47.8 oz.
With wings loading 11.8 oz./ft.^2 gliding before landing is rather short without massive pilot's pull. I have never made one full gliding lap with this plane no matter how hard I pull and run backwards.

The plane is very sensitive for the AOA in the gliding phase and the slightest input error leads to stalling.

I will add some lead at the nose like suggested by Ted and fly with the LG moved AFT.

Igor,
The Max Bee I am building will have the LG attachment points according to your plans. Like you know, MPBee was built for me by Tomek Jadczak in Poland. Tomek builds reasonably well but this plane has several features that I want to change and the LG position is one of them.

Regards,
M

[Brett Buck]

Keith, Ted, Igor,
EParrot has 23% airfoil and weights 47.8 oz.
With wings loading 11.8 oz./ft.^2 gliding before landing is rather short without massive pilot's pull. I have never made one full gliding lap with this plane no matter how hard I pull and run backwards.

The plane is very sensitive for the AOA in the gliding phase and the slightest input error leads to stalling.

     Where is the CG in percent of the mean chord? From your description, it is *way* off, like large fractions of an inch at least.

     Brett

[Ted Fancher]

     Where is the CG in percent of the mean chord? From your description, it is *way* off, like large fractions of an inch at least.

     Brett

I expect Matt is reluctant to add weight because of the wing loading, and I understand as nearly 12 oz/square foot is pretty heavy. 

Nonetheless, my response remains that whatever it has to weigh in order to fly controllably it has to weigh.  If the plane is tail heavy there are only two ways to reach that goal: 1. Add weight to the nose, or 2. Make the tail end lighter.  My first thought would be to start adding weight to the nose until the plane is controllable in the glide and then consider carefully whether or not enough weight can be removed from the tail to get the CG at the same location.  My expectation is that t won't be possible to do so by removing weight so either adding weight to the nose or some combination of adding to the nose and removal from the tail will be necessary.  The bottom line is that the CG must be at a point where the aircraft is airworthy before proceeding to other trim issues.

I've a separate question for Matt re the picture of EParrot.  There looks to be a very large yellow tab apparently attached to the right flap trailing edge at quite a significant "up" angle...perhaps to cure a roll induced by a warp??? (if so the warp would have to be on the inboard wing cause the outboard appears quite straight from the photo).

IF that is the case and it is attached to the flap at that angle it will be acting as a "control tab" attempting to drive the flap to which it is attached down which, in turn, would be driving the connected elevator "UP" which will attempt to raise the nose which can lead to a stall especially during a dead stick glide.  Won't say any more until Matt can advise if my observation of the yellow "thing" is accurate.

Ted

p.s.  A "control tab" is a device intended to assist the pilot in deflecting large control surfaces.  Some early air carrier jets utilized them  as the means by which the pilots could deflect very large control surfaces aerodynamically prior to the implementation of fly by wire or hydraulically driven surfaces. 

A "trim" tab as we speak of them on stunt ships is used to correct unwanted roll and must be attached to a fixed trailing edge surface so that it acts like a tiny aileron to control the roll attitude of the aircraft...not to displace a control surface.

[Target]

That yellow "thingie" could also just be a fence on the end of the flap, to attempt to keep the airflow from slipping off the wing.
It could be a "side force generator" for use in the overhead eights!

:-)
I'm basing my guess on the shadow of it on the fuselage in the picture.


R,
Target

[Matt Piatkowski]

More good news.

Please see the attached.

The carbon composite LG installed is lighter than the previous, steel wire, LG. To keep the CG where it was (Ted, Brett...I hear you. Please keep reading), I added 1/2 oz. of lead to the nose. The total weight of RTF plane is, as it was, 1355 grams (47.8 oz.) but the yaw inertia is probably different.

I have to run the numbers to check it but I have made four flights today and eParrot lands reasonably well after longer and better gliding.

There was virtually no ground lever wind so the conditions for testing were very good.

Ted,
The yellow tab is needed to level the wings in horizontal normal and inverted flights. There is some warp somewhere.

Target,
The vertical "thingie" is indeed for that but I do not know if it works as intended. Looks cool and high tech, though...(he...he,he..!).

Happy Flying,
M

[Trostle]

Ted

p.s.  A "control tab" is a device intended to assist the pilot in deflecting large control surfaces.  Some early air carrier jets utilized them  as the means by which the pilots could deflect very large control surfaces aerodynamically prior to the implementation of fly by wire or hydraulically driven surfaces. 

 

I know this is off topic, but the subject of "control tabs" or "boost tabs" is interesting.  One of the "early air carrier jets" Ted mentioned  that used these is the DC-9.  Among other full size aircraft to use boost tabs was the B-29.  The B-29 did not use hydraulics or electrics to move its ailerons, elevators and rudder.  Instead, the pilots controls were connected directly to the boost tabs on those moving surfaces which in turn moved these rather large control surfaces.  Boost tabs are not a new subject for our CLPA models.  Howard Rush has experimented with them for several years.

Keith

[Matt Piatkowski]

Additional comment regarding eParrot: perhaps slightly better gliding before touch down is caused by LESS drag on the landing gear?
The removed LG has six wire pieces exposed to the air flow: two main 0.118" dia. legs and four 0.0625" dia. stiffeners. See the attached.
I had to add stiffeners to eliminate shimmy during take offs - there is a separate thread describing what I did.

Newly installed LG has 7% airfoil similar to Clark Y and the carbon composite surface is smooth.

Just a thought....
M

[Brett Buck]

I expect Matt is reluctant to add weight because of the wing loading, and I understand as nearly 12 oz/square foot is pretty heavy. 

      Still, that's well below almost all recent NATs winners - and as you note, it doesn't matter, it has to balance even if it takes 8 ounces.

     Brett

[Brett Buck]

Additional comment regarding eParrot: perhaps slightly better gliding before touch down is caused by LESS drag on the landing gear?
The removed LG has six wire pieces exposed to the air flow: two main 0.118" dia. legs and four 0.0625" dia. stiffeners. See the attached.
I had to add stiffeners to eliminate shimmy during take offs - there is a separate thread describing what I did.

   What the heck is that?! You put that on an airplane?!  It's all unnecessary, just use regular 1/8" music wire, or .040-.045 2024 aluminum, or one of the widely-available carbon fiber sets. And for goodness sake, don't put a lifting airfoil on it!

     Regarding the CG - where is the CG with respect to the mean chord? Telling us you added a tiny bit of nose weight doesn't really help if we don't know where you started.

     Brett

[Matt Piatkowski]

Brett,
I put the extra struts on the wire LG to prevent shimmy. There is a separate thread regarding this.
I cannot change the LG main wire to 1/8" without major fuselage surgery and it is unjustified in circumstances.   

The CG of the RTF model is where it was before the LG change. Please see the attached.
The CG is located along the orange line. Blue line indicates MAC. The intersection of both lines is located 15.5-16% from the LE of MAC.

I am going to fly all afternoon today so there will be plenty of time to test and re-test eParrot and MPBee landings.

Thank you,
M

[Ted Fancher]

 

I know this is off topic, but the subject of "control tabs" or "boost tabs" is interesting.  One of the "early air carrier jets" Ted mentioned  that used these is the DC-9.  Among other full size aircraft to use boost tabs was the B-29.  The B-29 did not use hydraulics or electrics to move its ailerons, elevators and rudder.  Instead, the pilots controls were connected directly to the boost tabs on those moving surfaces which in turn moved these rather large control surfaces.  Boost tabs are not a new subject for our CLPA models.  Howard Rush has experimented with them for several years.

Keith

Exactly Keith. 

Although I'm sure I flew several control tab equipped ships in my early career the one that sticks in my mind was the Boeing 707-720 equipped, IIRC, with tabs on the elevators and ailerons.  I don't recall for certain the power source to the rudder but expect it was believe it was directly controlled by hydraulic boost activated by pilot rudder pedal inputs. 

The rudder system also utilized a Yaw damper mechanism which controlled the tendency for the swept wing to induce sort of "out of sync rolls" due to yaws affecting lift which increased lift on the forward moving wing and vice versa.  One of the great thrills of simulator training on the 720 (not so much in the real world) was simulating disabling the yaw damper and turning control of the pitch/roll couple manually to the pilot flying.  A "LOT" harder than handling an engine failure on takeoff!

Ted

[Ted Fancher]

More good news.

Please see the attached.

"snip"

Ted,
The yellow tab is needed to level the wings in horizontal normal and inverted flights. There is some warp somewhere.

"snip"

Happy Flying,
M

Matt,

Any warp that you thought required that much angle and that large a tab should be clearly visible!  The correct reaction is to straighten the wing.  I seriously doubt you've got a warp big enough to require such a mammoth fix even if it was mounted correctly (to the "fixed" wing surface). 

More directly, re your landing problem.  Pay close attention to Keith and my comments about control tabs and you'll quickly understand why attaching that tab to a "control surface" (the flap) is doing way more to the EParrot's aerodynamics than what you think it is regarding simply leveling the wings under power.  The primary aerodynamic affect is not leveling the wings but "attempting" to drive the flap in the opposite direction...in this case "down" which in turn attempts to drive the connected elevators "up"!!!!!

Question: how does a student pilot practice stalls and stall recoveries?  First the instructor pulls back the power (sort of like running out of gas with the EParrot, huh).  The student is then instructed to pull back on the stick/wheel to pull the nose up by deflecting the the elevators up (sort of like what the large "control tab" on your flap of the EParrot is trying to do to the connected elevators.  Sure enough, in short order the lack of thrust and the nose high attitude causes the student's Cessna 150 to slow and stall (sort of like what you've described from the start of this conversation) the nose drops in at attempt to regain flying speed assuming there is sufficient altitude to do so (clue, level flight altitude is 4 to 6 feet for our purposes, probably not enough to regain the necessary speed to make a decent landing.  (Ta Da!, baaaaad landing).

Compounding the problem on a control line model is the associated loss of tension and, as a result, reduced ability to overcome the control tab induced climb that is slowing the EParrot to...you guessed it...a stall--no matter how hard you try to whip the thing.

I'd strongly suggest that you take the tab off the flap and temporarily stick on enough weight to the outboard wing tip (at the point it balances when held by finger at the wingtip) to insure it won't be banked into the circle.  If you guess wrong the first flight adjust the amount of weight until the wings are level upright.  For safety do not, during these tests, fly inverted.  These are test flights not practice patterns!

Assuming your first stab at replacing the tab with "tip weight" is close my bet is that you'll immediately get improved handling in the glide.  I base this guess on all of the above plus your latest comments about "improved" landing performance after moving the CG to where it is (15% MAC should be plenty far forward for a controlled glide and touchdown based on any remotely reasonable stab/elevator area.

One last comment on a related but not necessarily critical matter.  Take a look at your EParrot pics and note the relative deflections of the flaps and elevators at rest.  They both appear to be down a noticeable amount.  Is this relationship something you built in on purpose or adjusted during test flights for some reason?  If not you should probably consider adjusting the pushrod to make them level at the same time...at least as a starting point!

Whew!  Sorry.  TMI!

Ted

[Target]

Matt-
Can we get a top view of the outboard wing on the EParrot?

[Ted Fancher]

Matt-
Can we get a top view of the outboard wing on the EParrot?

Think we've lost him, Target.

[Matt Piatkowski]

Hi Ted.
More good and probably final news.
I have learned to pull eParrot for one lap after the motor stops and the gliding and landing segments are satisfactory for me now.

The trick: while flying the last two laps before the motor stops, I fly simply at the fifteen feet height. KR governor I am using adds the RPM for three seconds before switching off the power and then I dive to the level required by the rules, pulling at the same time. The combined effect of diving and the KR governor RPM boost adds enough speed and I do not have to run backwards like crazy to execute one lap without power.

Going back to your comments: yes...I am aware that the yellow tab at negative angle has the effect described by you during gliding but I am finding this effect minimal and acceptable in circumstances. The plane glides and lands much better than before and this was the goal of the entire exercise.

You wrote: "Take a look at your EParrot pics and note the relative deflections of the flaps and elevators at rest.  They both appear to be down a noticeable amount".

The control system has intentional slack, namely, certain movement of the elevator is possible without any flaps movement.
This movement is about (+) (-) 1.5 degrees. As I fly now better than before, this "build-in forgiveness" of the control system can and will be eliminated.

Thank you for bringing this issue to my attention.

Hi Target,
Please see the attached as requested by you.

Regards,
M



 

[Target]

Hi Matt. So my request for the top pic is to see if what Ted was looking at in the profile pic, and (i guess) he was thinking it was a 30 degree trim tab, was really what i was thinking it was, a vertical tab, which it is.
Ted, can you confirm that my hunch was correct?

Glad your plane is gliding better and landing better now. I think the key is to have the cg and the wheels not to far apart.

[Ted Fancher]

Hi Matt. So my request for the top pic is to see if what Ted was looking at in the profile pic, and (i guess) he was thinking it was a 30 degree trim tab, was really what i was thinking it was, a vertical tab, which it is.
Ted, can you confirm that my hunch was correct?

Glad your plane is gliding better and landing better now. I think the key is to have the cg and the wheels not to far apart.

100% correct Target.  Good catch.  Matt should take note of my error and your accurate assessment.  I wonder now, however, what the purpose of the large tab might have been?  I wonder if there is a matching one on the left wing and the intention is simply to add interest to the wingtips rather than any aerodynamic purpose.

Glad you asked for the picture which made it very clear.  Alas, a lot of mostly wasted words in my last...  On the other hand, the reminder that "roll control trim tabs" shouldn't be attached to functional control surfaces (flaps in this case) is a valid and important reminder.


Glad Matt has the EParrot under control 'til touchdown.

Ted

[Brett Buck]

This is probably not really going to help - but Matt, you need to get to a stunt clinic, or set up a trim session with experienced competition modelers. Just like the previous issue with the engines (that as far as I can tell, never got resolved), you seem to have launched into a bunch of very elaborate fixes and "solutions" for problems that appear very basic - like getting the wings level, which is normally dealt with in a few flights, and strange "stall" issues and instability on the glide that are probably some very simple CG and pitch sensitivity problems.

  Ted was hinting around it, but this is a situation that he and I have seen over and over through the decades - you need to get the fundamentals correct before you can begin to evaluate anything more subtle, or, alternately, people want to see complex problems when they are generally very simple. What you appear to need - again - is to get a solid baseline bench and initial flight trim, THEN, start looking at more complex issues. Your airplane design is not in any way exotic of tricky, there should be no reason to have to deviate from the simplest of setups - whatever that is on the wingtip, I absolutely, positively, guarantee that it is not necessary and greatly complicated what seems to be a simple problem.

    Part of being successful is knowing where your blind spots reside. I suggest that the tendency to either overlook or simply not knowing how to achieve a baseline using the simplest techniques has led you to looking for subtle ghost issues where the problem is absolutely straightforward. It is *extremely common* with people who do not fly with more experienced modelers because you have no easy way to establish what is normal and what isn't. I did that, too, and even though I was essentially born to be an engineer, I struggle with very slow progress for many years and lots of wasted fuel - and then took quantum leaps when I went to fly with more experienced modelers.

    People are doing their best to assist remotely, but you have had such a series of strange problems that I think you must make the effort to make it to fly with others - people who really know what they are doing - to help you sort of the real iand the simple issues from the phantom perceived issues or things you just don't know. There's no shame in not knowing, no one knows when they are starting out. As near as I can tell, you are in Eastern Canada. There are very good fliers in Detroit and Cleveland, and even if you have to go way down south to a Randy Stunt Camp or other clinic - you should do it.

     Brett

[Ken Culbertson]

Ted:

Does this imply that you should not use a tab on full span flaps.  That only leaves tweaking, or better yet building it straight - correct?

Ken

[Tim Wescott]

Does this imply that you should not use a tab on full span flaps.  That only leaves tweaking, or better yet building it straight - correct?

Yes.  And you'll almost undoubtedly need to tweak.  Or follow the instructions here.

[Ken Culbertson]

I struggle with very slow progress for many years and lots of wasted fuel - and then took quantum leaps when I went to fly with more experienced modelers.

     Brett

Matt:
This quote is so true that it should be printed on the plans of every stunt trainer kit.
Nothing can substitute for face to face help in trimming.  Most experienced fliers can have rough trim on anything in about three flights.  To the novice that is usually enough, to the expert that is the starting point.  It is very difficult to diagnose basic trim without actually seeing the plane fly.  For that you need two people and it is best when the other one knows more than you do!  I am very lucky in that regard, I have just about everybody at the field to chose from!

What you can do by yourself and improve is to use video.  There are a lot of very good videos on YouTube of great patterns. (Brett has some really good ones).  If you have a tripod and place it properly you can diagnose many of your problems and work on them - to a point.  When you reach a certain level, it is very subtle things that are causing errors and that usually takes some coaching.

Ken

[Tim Wescott]

Matt:
... It is very difficult to diagnose basic trim without actually seeing the plane fly...

Not to mention just seeing the plane.  A huge part of a well-trimmed airplane is a straight airplane.  Before you can do anything with weights or tweaks or whatever you need to have a straight airframe.  I've looked at a lot of crooked planes in the hands of beginners, and not-so-beginners, and I've been able to do a few "magical" fixes.

[Matt Piatkowski]

Guys,
MPBee was flown by two good stunt pilots - one in Europe and one in Canada and both opinions were positive.
EParrot was flown by one good Canadian stunt pilot before the landing gear change and I was told "I could compete with this plane".

I will ask the members of the Canadian F2B Team for Landres 2018 to fly both planes in October and will listen to their verdict.

I believe both planes are reasonably trimmed and satisfy my expectations right now.
I stress the word "reasonably".

I do not expect to win the next World's F2B Championship in Wloclawek, Poland with these planes.
I do expect to improve my pattern flying both and this is happening right now.

Lastly, there is no perfection - there is only continuous improvement and this is what I do.

"Better is a mortal enemy of good enough".

Happy Flying,
M




   

[Target]

So what is the theory behind the vertical finlet on the outboard wing?

[Matt Piatkowski]

Hi Target,
The fin increases the air drag and creates lift in the direction perpendicular to it. Both forces yaw the entire plane by some angle.
I do not feel any increase in the lines tension in the overhead maneuvers, probably because this yaw change is very small.
Like you probably know, the fins of this kind are used by some of the acrobatic R/C models to improve the Knife Edge maneuver and the Wingover can be treated as the Knife Edge maneuver.

Regards,
M

 

[Target]

It would be interesting to see if you could feel the difference on or off, if it were removable.
I would think that it may also make the flap more effective possibly by preventing spanwise airflow. But it's hard to say with it fixed in place. I'm sure it has some minor effect of some sort.

[Ken Culbertson]

Hi Target,
The fin increases the air drag and creates lift in the direction perpendicular to it. Both forces yaw the entire plane by some angle.
I do not feel any increase in the lines tension in the overhead maneuvers, probably because this yaw change is very small.
Like you probably know, the fins of this kind are used by some of the acrobatic R/C models to improve the Knife Edge maneuver and the Wingover can be treated as the Knife Edge maneuver.

Regards,
M

I don't see how having the fin only on the top of one wing can do anything other than produce roll.  Maybe I am wrong.  I use tip plates and twin rudders a lot on stabs but mostly because I like the looks.  They do improve the effectiveness of the elevator but so does simply making them bigger and moving them back.  But, why not.  No idea was ever made to work by not trying it!

Ken

[Tim Wescott]

... and the Wingover can be treated as the Knife Edge maneuver ...

In normal level flight, the plane is experiencing between 2 and 3 g's of centripetal acceleration.  As long as you keep your speed up, the wingover can be treated is flinging a rock over your head on a string, not as a knife edge maneuver.