OK, this is a legit question

I have read many bits and peices about the newer widebody planes for competition. It seems that the goal is to acheive good slow pace to the whole sequence. uplines, downlines, straight and level flight.

my question is what makes this possible and in what combination.

widebody design - more physical displacement of the air?

drag - such as fixed gear, cowl cheeks?

wing area and wing design?

overall weight - 9lbs vs 11lbs?

2-stroke vs 4-stroke?

prop selection?

I fly a Focus/Webra 1.45. it seems that compared to a Smaragd/YS 1.40 that the Focus flys much faster.

so 'cmon all you Jedi masters, please share with us your knowledge.

Hubb

Throttle management.

bigger prop

Only one thing makes an aeroplane fly slowly on a down line...Drag

To fly at the same speed on an upline...Power

To fly at that speed straight and level... A throttle!!!

Low wing loading is a big factor, also a constantly moving throttle, you don't need a fat plane to fly slowly, but odly enough you do need lots of power. You need the power to be able to pull you up the verticals when you have little kinetic energy flying along slowly.

so, wing loading will affect downline speed as well?

then what is the trend for the bigger fatter fuselages? I guess what I am asking is what makes that package seem to fly slower and pace better than the narrow older style planes?

Hubb

Bigger planes appear to fly slower than smaller planes at the same real speed (e.g., perceived speed).

If you are asking about real speed (relative to the air mass), the ability of the plane to fly slowly depends on the lift generated by the wing and the weight of the plane.

Since pattern planes use symmetrical wing profiles at almost 0 incidence and wingspan is limited to two meters, we can rule out those three variables. Then, you can definitely say the flying speed will be most affected by the wing thickness (much more than any landing gear and cheek cowl), and chord (Reynolds number). Therefore, fat and wide wings will fly slower than thin narrow ones. By the way, the wing chord also affects aspect ratio, but we can use one or the other in our calculations since they are matematically equivalent (given the almos fixed wingspan around 2 meters).

Now, given the same wing, a fatter fuselage with side cheeks, fixed landing gear and lower pitched propeller will definitely be slower than the opposite side around.

Considering the speed patten is flown at, the drag from anything on the plane ( baring airbrakes ) like cheek cowls fixed gear etc is really quite negligible. You really have to look at it as a whole system rather than saying wide bodies fly slow. The wider bodies tend to get pushed around more in a cross wind, so they need rudder correction to hold the heading, this crabbing slows the plane down. Wider bodied planes can be built lighter, the strength comes from the shape and size not the amount of material there is holding it together, which gives a lighter wing loading. The wide bodies are usually powered by well behaved 140 YS, OS or webra, they have loads of torque which means they can swing a bigger prop, which means that you can have a lower pitch to get the same thrust. This bigger prop gives a greater flywheel effect, combined with the new well behaved engines means a verrrrrrrrrry low idle, low enough that the prop is supposedly creating more drag than thrust, giving a slow downline speed. Then you have to think about the people that are flying the wide bodies, they probably have several years of pattern experience so they don't forget to shut down the throttle when coming over the top of a humpty bump that sort of thing. You put all of this together and you have a graceful slow package.

Matt

Low wing loading is the key to slow flight, the higher the wing loading the easier it stalls.

One way to slow the down lines is a larger prop so people use 4 strokers because they'll swing that larger prop.

I'm not sure anyone here is answering Hubb's question. Skirting around issues yes as I have wondered the same thing.

My uneducated assessment is this.

As mentioned drag is a big factor. Several years ago, cheek cowls came out that could be added, this increased drag on the front end, therefor the plane set up the same(same engine, prop etc) as one without cowls would fly slower. In this example the wing loading would be essentially the same as cheek cowls weigh almost nothing.

Next, enter fixed gear. Again, added drag. Fly a plane with retracts with the gear down vs gear up and gear down will probably fly a little slower. May not be terribly noticeable but have seen retract servos break and large manuevers with the same plane more difficult to achieve due to the extra drag.

Next came the wide body style, Hyde Away, Smaragd, Partner. The Smaragd has a huge amount of frontal area, again drag. A corvette slips through the air a whole lot easier than a cab-over tractor trailer. Add bigger and thicker canopy and fixed gear this plane will fly slower than my Oly whose fuse is only 3" wide(guess)

So the next question is does throttle management make a plane fly slowly, WELL. I challenge this to say NO. Some designs are for some reason inherently happy flying fast. My OLY will not fly well slow. When I try to manage the throttle my level manuevers go from scores of 8-9's down to 5-6's because the plane doesn't like the slower speed. Everything from wing rocking to the wind having much more effect etc. This plane was 10lb 12oz with 77" wing with straight trailing edge. Am not aware of Sq" but don't think that was the culprit here.

My Oly Medal flies much slower with cheek cowls and is not as sensitive to slower flight problems. The span is 78" and the fuse is a little taller, otherwise they are almost the same. Haven't weighed it though.

Personally believe the design of the plane is key here and I am unable to guess why.

Lastly, we have bi-planes entering the mix now. If read correctly, Chip has said the leading edge of 2 wings is more frontal area than the leading edge of a monoplane, as well as the drag caused by the flying wires is why he gets same speed flight level, up down 45's. Or at least makes it more controllable.

These are my thoughts and certainly not studied but hope it helps.

ed

Widebody - No I dont think this is important for slow flight, maybe has a marginal effect on downlines but that can be acheived on a small fuse through other methods.

Gear/Cheeks - Again no, the cheek cowls are largely for looks and do nothing except maybe to help cool the motor if they are cutout. Most fixed gear is quite aerodynamic and would contribute little to the drag.

Wing Area/Design - Definately the design of the airfoil on the wing and stab will effect drag. I think this is a biggie, a properly designed wing has the potential to really aid in the downline breaking.

Weight - Again yes, a lighter plane is much easier to get a nice contant speed flight than a heavier one. I am not talking about 9.25lbs - 9.75 lbs, thats really insignificant for most models, but 9.75 lbs to 11 lbs now that is a difference.

2-stroke/4-stroke - I dont think so, the two strokes have come a long way. I think it takes more effort to set them up to get similar breaking etc as a four stroke but if properly setup and flown right I dont think its a key element anymore. The four stroke is easier to throttle manage than a two stroke though IMO.

Prop Selection - Yes most definately. I just tried a three blade 15x13W on my 140DZ and it didnt break any better than a 16.5x12W!! You need to try lots of props, and find one that gives lots of up power and good down breaking. Diameter is your friend when it comes to downlines. Now getting the right prop for that may not put you in the noise limits so you sometimes need to compromise a litte. That is where good throttle management comes into play.

If I was to rank the importance of the ones I said yes to it would be something like this I think

1. Throttle management!
2. A light model
3. Propellor selection
4. Design, shape etc of the wing/stab/fuse

In preparing for the Worlds I have spent a lot of time trying to acheive that elusive constant speed flight. The correct use of throttle is key! In this day with our massively powerful motors its really easy to overuse the throttle and really get your plane moving at warp speed. Really focus on the throttle when flying and using only enough power to maintain your speed, I think you will find that your constant speed flying starts to improve almost immediately.

Anyways those are my thoughts on it

I have all of my F3A experience here in Europe. Europe, I believe, started the trend of slower flying and I have seen it taken to the extreme. In Romilly, however, I noticed that Qui-Que, Christophe, Marco, and Wolfgang (the top four, no it that order) all kept more throttle in than most. Marco flew the Angel's Shadow in Romilly which is a good deal more slippery than his new Supreme. They flew with relative quickness compared to most of the field. Too slow is a major cause of mushy, uncrisp manuvers. To fast, well, no time to think, snap become less controllable, and corner radiai become to large.

On constant speed, there is a notion here that I have not yet found in the rule book. Although it adds to precision if you are a counter (1,2, roll, 1,2, push), a geometrist uses the artificial horizons visualized mentally as another way to center the figures. Although I understand the judges have particular tastes, I do not find constant speed in the rules, thereby, according to me, only the geometry and not the speed of the figures should be judged. That said, the new airplanes with fat fuses, thick profiles, and parasitic drag here and there manage quite well to keep a constant speed to compliment the trend. Yes, I too am trying to become an expert at constant speed.

Like anything, now, the speed at which an airplane flies is a synergistic principle of drag, wing loading, and propellor selection. I will separate my major areas with paragraphs only to be more clear.

Drag is created in several major areas.

Although fuselage width does not play a great factor, the radius of the curve from the nose to the sides of the fuselage does make a large difference. Then there is total skin area, although at the lower speeds this too is minimal.

A huge and often overlooked drag factor are the thicknesses of the trailing edges of the wing, stab, and rudder . Thicker TEs add great amounts of drag.

As far as wind affecting the flight goes, actually the wing geometry and airfoil design have more of an effect in this than the fuselage side area. Remember that pressure on both sides of the fuselage are equal when the aircraft is following a constant flight path. More side area is getting hit by the windward side, but there is the same side area on the leaward side so the effects balance out. Side area balance between the nose and tail of the airplane is quite important in this respect.

The gear add a little bit, the ductings and cooling holes add a little. The further back along the fuselage, the less the effect these little pieces have.

Yes, wing loading has a very significant effect, especially on downlines. It's a little bit bizzare, but draggy airplane fly faster with higher wing loadings (see gravity) and racing airplanes fly slower with higher wing loadings (see angle of attack in regards to lift induced drag). OK, this is greatly simplified and much here depends upon the flight attitude, but always shoot for lighter. We have not yet found the point where the airplane is too light.

Then, of course, there is the propellor. Pitch is effective in pulling the airplane uphill, and the slow spinning prop slows the airplane on the downlines. Prop braking loses all effects when the airplane slows or goes below the speed at which prop thrust velocity equals the airplanes airspeed (hence, killing the motor will shorten the rollout).


There are some ideas from this peanut gallery.

Cheers all and fly greatly!!!

Mark

The wide-body fuselages have what is known as a larger flat-plate area when the aircraft is viewed head on. Fuselage shapes may be very streamlined, but you will never have true laminar flow from the tip of the spinner to the tail wheel. Around the edges of the fuselage where this airflow begins to separate you begin to build up drag. The larger in diameter this area of separation, the more Flat-plate drag area. Plus Propeller area works in much the same fashion. In a down line, a 17" propeller(when being "back-driven" by the relative wind) has a larger disk area than a 15" diameter propeller. The larger the disk area, the greater the drag when at Idle in a down line. Plus four strokes maintain a slower RPM in a down line, and 2 strokes are revved up by relative wind. JB

Sorry, but that's not true. If there is 20 knots of crosswing, a pattern plane, F3d racer, park flyer or concorde flys sideways at a gound speed of... 20 knots

Quite a bit of aerodramatics in this thread.

i am not very familiar with pattern but being arospace eng. i think the wider bodies play a role in slowing the plane down, if nothing else you have more air displacment then more slimline models (More volume moving ) and this thing called air to surface contact area, more area you have for air to contact, more drag you get.
on the other hand i think larger propelers create more bad air behinde the prop and chick cowls and most of the landing gear are in the bad air sreem and dont play much of a roll, retract bays also create lots of drag that imo = to a good grear,
i might be wrong but some stuff to think about

true, but I find this a very intruiging subject. it is nice to see everyones collective thoughts in one place. might dispell some myths and misinformation.

Mark,while there is no judging criteria, I see two benefits to this from my experience - perhaps the reason for the trend (?)

1, constant pace gives the pilot more time to think between manuvers and can help us geometrically un-inclined to space our figures inside the manuvers. also keeping from having to drive some vertical manuvers to the stratosphere to cope with a string of downline manuvers such as point rolls (the ground can come up pretty quick when you are trying to get the rolls in and keep your line spacing equal) which leads to #2..

2, again, while there is no criterea, a nicely constand pace to a sequence or manuever presents to the judges better than one that is potentially rushed and could in fact lead to bad geometry of a figure. all part of presentation and could lead to a 1/2 or point or more - you never know.

interesting reading gang

Hubb

Lots of interesting information here.

When thinking about the fuselage size and shape you must remember a few things. The prop makes the a large disk or displacement in the air. Bigger props have a bigger displacement and also have a bigger dead band in the center. Say you used a 16" (only for comparison) you would have a dead center of roughly 20% or 3.2" that was of no use for thrust. (The center area of a prop cannot be pitched high enough and is stalled any closer than 20% of the prop diameter. There for no airfoil is used in this area.)

Also, the prop causes a pulsing disturbance over the fuselage in a swirling direction the same direction as the prop is rotating. So, you cannot make the have get the fuselage to have laminar flow.

Another point to make about the drag of the fuselage. The longer the body the wider it can be without causing any larger drag penalty. Lets say your fuse length is 78" and you wanted a thin low drag body. You would probably chose something around 7%. That would mean you would make your fuse 4 1/5" wide with the Max thickens at 33 to 40% back. This is very low drag when you consider the large prop needed just over 3" to use for a spinner and the transition from the spinner to the wide point of the fuse needs to transition smoothly.

OK Say you wanted to add a draggy fuse... Lets make it fat ad use about a 12% to actually get some drag. Because a 8 or 9% is still kinda normal. That means you would need a 9 3/8" wide fuse to start to get the fuse to slow you down. The faster you go the less drag you make--this is how Reynolds numbers work.

(Coefficient of Drag the higher the number the more drag .9 has more drag than .5)

I ran some fuses through my Desk top wind tunnel program.

A 12% 2 meter fuse at 50 mph had CD of .0071

Now the real fast fuse that's only 7% wide at 50 mph has a CD of .0066.

The fat 12% fuse at 75 mph had a CD of .0067.

So, the real fast fuse at 50 mph matched the drag of the fat fuse at 75 mph...Kind a freaky when you thing about it...

Some other things fall into play here too. Say you wanted a to do a slow downline. The prop will dictate the airflow around the fuse and it will be different from the air just out side the prop disk. In this case the air around the fuse will be slower and there for more draggy. If you wanted a speed plane it would make a bigger and more significant difference. The prop speed will be much faster than the air speed and the drag would be less. Now don't start jumping down my throat with frontal area, parasitic drag and profile drag. Because this is the stuff that makes the smaller fuses on race planes work better...it not the size so to speak, but the actual amount of molecules the plane disturbs as it passes by. So less is always better in the long haul. But we are not talking about the hole aircraft--just the fuse here and were talking about slower speeds too.

Spend time on the fuse to make it handle correctly.

Wana make it slower. Spend more time on the airfoils. Check out the Eppler 474 if you want to see some backward stuff. The faster it goes the more drag you get and the more it will stall. (this is good for Snaps) Slow it down and under 150K Re and will continue to lift even in a deep stall and high Alfa. Pretty nice for landings and 3D stuff. Landing gear, things that disturb the airflow around the fuse to make it look fatter to the air and stuff like that.

Air brakes would probably work the best. (Hence the Name) Set up Flaps on the inboard of your ailerons. When the throttle is set to lower setting the airbrakes would gradually become stronger. And to balance the aircraft so there is no pitching problems. The flaps would come down and the ailerons would go up...Crow or butterfly as it's normally called.

The flaps can be mixed to the ailerons so you don't lose the roll rate.

For lighter aircraft that balloon at landing; you would reflex the TE (Raise the flaps and ailerons.) This reduces the amount of lift you have to get the aircraft to basically drop down without reducing the speed any farther. Also adds twist (washout) in the tips to keep them from tip stalling.

OK, I got a little carried away here--but it's just something to think about when you buy that new aircraft or decide to try something new.

Thats not really what I meant, by pushed around I meant bumped around by gusts and bubbles, I didnt mean crabbing.

I thought the main purpose of the larger fuse was for handling purposes. Like better roll rate, knife edge performance, etc. And best of all, I can get my hands in the dang thing to work on stuff.

AS for slowing it down... I think the throttle is the most important followed by wing drag(thickness) and prop choices. Wing drag you can't control unless your desigining the airfoil of the airplane.
Look at the fun fly airplanes with wings as thick as a brick yet they have a profile fuse. They will fly very slowly due to the thick airfoil.

Profiles also have an extremely low wing loading.