tony0707

HI WOULD LOVE your thoughts on the use of down and right thrust to improve the trim characteristics of an airframe- please only reply if you are very experienced , flying AND TRIMMING for many years
i have been building ,flying and trimming for 20 years-i have always set my wing , stab and engine at zero degrees to each other on all my airframes on jigs in my shop-my stuff flys on rails
i posted this in the 3D section and now the pattern section always looking to improve what i am doing in any way i can ENJOY REGARDS TONY

bjr_93tz

You've answered your own questions. If all your planes fly on rails then you don't need to change your engine thrustline settings.

Changes to engine thrust line angles are only used to correct faults where engine thrust is the predominate cause/cure. ie vertical upline tracking in the pitch plane is trimmed with engine downthrust/upthrust, while straight and level flight tracking (upright and inverted) is trimmed using centre of gravity and decalage.

Sidethrust is a matter of personal preference in that not enough causes some problems, just right causes less problems and too much causes different problems, so you have to decide which problems you can live with and which ones you can't. Generally if you can pull to an upline and your plane doesn't deviate left or right as you slow down while still under power then you're pretty close.

The above are generalisations and I've never seen a zero-zero setup fly straight yet but they fly straighter than a really crooked plane.

For 3D work, if your holding in a heap of right rudder and down elevator in a hover I'd be tempted in add right thrust and downthrust. If your plane needed up elevator and left rudder to hold a hover I'd be temted to add up thrust and left thrust. Every plane is different.

MTK

Flies on rails....not particularly demanding of the flight envelope; sounds like it's sport flying and for that, 0-0 is fine. For demanding pattern performance in the highest level of competition, a bit of down, as much a 1 1/2 degrees and a bit of right, as much as 2 degrees for prop sizes up to around 20" is fairly typical of the current crop of fuse designs. What you are after is straight flight with application of rudder, and pure response in any attitude from any control input. This is the holy grail but unlike the biblical sense, this is achievable, without e-mixing much of anything

For true 0-0 set-ups you have got to eliminate the spiralling airstream. This also is not a particularly tough problem but you have got to be able to think outside the "normal" box when designing.

MattK

David Bathe

I've never had or seen a 0-0-0deg model fly well.Regardless of what ever design I always end up with say 1deg down 2.5-3 deg right thrust on the engine. Wing set at about plus 0.5 (ish) deg and stab set at about 0(ish).Infact it's became so evident years ago that I just build the models with these setting on the board.I've tried the ol' mixing rudder with throttle instead of right thrust but just decided that right thrust was easier. Only thing I kept was a little left rudder at very low throttle settings.If you're happy with 0-0-0 Tony you're going to be super delighted after a few tweeks. Start with the engine. Slowly pull up to vertical, let go of the sticks and keep adding right thrust until the model goes dead STRIAGHT up.You know the routine.

cmoulder

Hmm... on ALL you airframes?!

On a high-wing design with a flat-bottom airfoil? On a motor glider, some of which have 10 degrees down thrust?

Try 0-0-0 on the one pictured below - my aerial camera platform - and you will not get off the ground!

The motor thrust is set at 2.5 degrees of right thrust and 4.5 degrees of UP thrust, about -1 deg on the stab. It flies as if the motor were in the nose.

bjr_93tz

Well I have to say that I've discovered a new piece of bait for the forums if I'm having a dull day and it's to post a statement in a pattern forum that a 0-0-0 setup flys straight :-)

Thanks Tony0707, and don't take the comments to heart too much, pattern flyers are very glass-half-empty folk when it comes to how straight and neutral a plane flys and strive for perfection in nearly every conceivable orientation and loading even though deep down we know it's an impossible dream.

I'm off to a 4x4 forum now to ask if I should fit a diff locker to the front or the rear.... :-)

klhoard

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Well of course a 0-0-0 setup works well in AUSTRALIA, you are in the Southern Hemisphere!!  "Up" here in the Northern Hemisphere we have 1G of gravity pulling DOWN on our planes at all times.  Bring your 0-0-0 airplane up here and see how well it works!!!!

klhoard

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. . .Double Post. . .

cmoulder

Cool! Planes that fly with no AOA! Awesome!!

tony0707

HI THANK YOU to all who replied to my question i am a sport flyer and do not yet do any 3D stuff myself my planes do fly on rails and go right were i want them to at all throttle settings-i do a clean loop with no control inputsas long as i am square at the start of the loop-and into the wind ( 98 % of the time )
part of the reason i am asking the questions i am is-at my field i am now in contact and discussion with a gentileman who is very accomplished -in flying pattern -he has traveled the pattern circut for 17 years he flys his own design and has become one of the flight trainners at my field
he has told me that he sets his wing 1/2 degree positiveengine 3 degrees down and 2 degrees rightjust as DAVE BATHE explaned he does in a post above- this is the first time this set up was suggested to me( although a friend who is responsible for desgning 3 of the 3D manuvers used todaytold me to put in down thrust so the plane flys inverted with a little down elevatoryou then have the balance right ) i do realize that each plane is set up a bit different-but this is a new and very interesting subject to me that i have never tried -and having my RC planes fly as well as i can is one of my lifes passions -after 20 years of building and flying these trimming adjustments seem to me to be those very fine adjustments that can add the icing on the cake to a plane that is already flying very well i will be making these adjustments to one of airframes in the near future and see were it may take me The pictures below are of my 60 ULTRASPORT kit with an OS 91FX glo engineall contols surfaces were centered on the first flight THANKS AGAIN ENJOY REGARDS TONY

David Bathe

You'll enjoy it Tony.

bjr_93tz

I never said I fly 0-0-0 I was just backing up Tony0707 a bit as the first four (4) replies jumped on him for it

All my planes are crooked so they fly as straight as I need and my free flighters are bent even more to fly "straight" circles.

Gravity work the same way independent of the hemisphere but we need to fly the patterns inverted with our planes in the northern hemisphere when flying north-south flightlines due the the reversed coriolis effect.....

mjfrederick

Tony, I'd say that right and down thrust are pretty much necessities for any propeller-driven model, but 99.9% of the time the designer has done his homework on those settings and they should be OK as recommended from the designer. The issue I would take is that 0 incidence on the wing. Fully symmetrical airfoils like those used on almost all aerobatic models cannot produce lift without a positive angle of attack. If you have an airplane with 0 incidence on the wing, the only ways to have the airplane fly level is to trim in up elevator (which will lower the tail and increase the wing's angle of attack), or put weight in the tail. Putting weight in the tail is the most common method because people want to have their trims at neutral. Flying tail heavy leads to all sorts of other nasty trimming and mixing issues that are beyond the scope of this discussion. So to sum up: I'm a fan of what the pattern guy said.

flyncajun

Tony,
we are talking IMAC,Sport planes ,and Pattern planes here,
.5 pos is only a starting point ,,many factors are included to find the right inc. airfoil ,wing area, overall weight of the airplane ECT, But thats a good place to start.
OTOH you never need more than 1.5 down or 1.5 right thrust on any modern pattern plane, no matter the prop size ,and,no matter who tells you other wise.
The engine thrust has almost no effect on trimming( if done correctly with the proper CG and wing inc.) and should be the last thing adjusted for trimming a pattern model.
and then only a very good flier can even tell the difference.
If you use the engine thrust to fix something you just broke 3 other things it`s not an adjustement you would want to use to fix anything. so,
If you have to use aileron trim or throttle to rudder trim , mixing for different model speeds your not finished trimming your airplane and your c/g is too far rearward.
don`t let no one fool you an that..
Engine thrust has been given too much credit over the years and just repeated from guys with little credibility on the matter. The Wing is the most important thing to adjust ,
CG is Second, other things next ,thrust, Last ,But if the design is sound , and the designer has done his homework,, then your thrust should be correct from the start,,unless the designer uses a .3pos, down to 0-0 setup, then he will adjust the thrust first and you have to mix the crap out of everything else.
This was used till a few years ago but most modern designs have started using some measurment of Positive inc. in the wings ,,,they just have not figured the rest out yet
Bryan

mjfrederick

You should listen to Bryan, he's been deigning and flying pattern planes for almost as long as I can remember and knows what he's talking about. I started in pattern back in 1990, and he was sort-of an outcast because everyone thought 0-0 was the way to go and he's flown positive incidence for as long as I've known him. Of course, his trimming techniques are much more refined now than they were back then, but he's been doing it forever.

tony0707

HEY BRYAN do you know who ED CARPENTER is by chance-not sure if he was flying pattern in the same time slot that you have been REGARDS TONY

tony0707

HEY MJFREDERICKI started to build RC and sport fly in 1990-was buiding U control for 7 years in the late 50's prior to that a lot of combat then building a lot in that total 27 year periodhave 23 planes ready to go-thanks for the heads up on BRYAN AND YOURSELF REGARDS TONY

tph1

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let me ask a dumb question here, is positive incedence with the leading edge higher that the trailing edge or lower?
thanks

Oilsands

Positive is with the leading edge higher than the trailing edge.

tph1

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that's what I thought, just had a brain fart gettin' old

flyncajun

Hi Tony

Yes I know Ed Carpenter,
and I know Everett Carpenter ,,although, I have not seen either one at a contest in many years
if you see them give them my regards
Bryan

grotto2

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Don't Nat Penton's symetrical designs all use 0-0 thrust?

flyncajun

Mark Hunt would be able to tell us he has Nat`s Plans done in CAD.
Bryan

tony0707

HEY BRYAN it is ED CARPENTER who is a member of my club in BROOKSVILLE FLORIDA ( west central florida ) and the person that i am now very much in touch withwho has put these trimming set up ideas into my head and inspired me to start this thread for my own infoit is a small world for sure- i will be very happy to pass on your regards to ED-your last name would be very helpful if you are ok with that. were do you live ?
ED is practicing now for a pattern meet that is being held in OCALA FLOIDA on March 20th if he gets enough good time to practice, weather permitting ,i will be going to the meet with him to help him with anything i can at the meet
i may have the very good fortune to get one of ED'S pattern planes that he designed in the near future -as he has offered it to mehis design is unreal to watch in the air and through its manuvers-he is a great flyer and very great asset to our club for many reasons i am a big fan of his these days and just stop all i am doing to watch him when he takes to the air he is also one of the nicest sweetest people i have ever had the good fortune to meet and talk to in this hobby and i have had the good fortune to meet many in 20 years. i retired to FLORIDA to fly five years agodid alot of my flying on LONG ISLAND NEW YORK'S CEDAR CREEK PARK in SEAFORD N. Y.

Columbus Ron

Tony, the instructions on every plane I have ever built require some degree of down and right thrust. Some beginner kits don't mention wing or stab incidence. For example, my first kit was an Eagle II (high wing trainer). It would kick hard left on take off without right thrust and without down thrust would not take off without a lot of up elevevator. Perhaps the kits you are building actually have right and down thrust and you just haven't realized it. All pattern flyers use a robart incidence meter or similar when setting up their planes. If you don't have one you should get one.