foodstick

I add down and right as a rule.. there will always be a torque issue, and WW1 planes will almost always make a lot of lift when you throttle up.

I suppose its what you get used to, and how much room you have in the nose to position everything.

Someone mentioned getting the gap correct on something like an Albatross. In a situation like that I would have the motor mounted with the thrust where I wanted it, tack glue the front former with a spacer to the back of the spinner, and build the cowl to match the back of the spinner...

valleyk

VG what happened to your dr1? Really flew nice at the chatfield warbirds event. I took your advice on dialing in right thrust and down thrust for my 1/3 gtm dr1 and it flys great.

fred985

i just build them as the plans say,,,,,but an intersting picture of my old 450 stearman shows well the incidence and down thrust on the p&W 450 VERY WELL. SEARCH" N 4734 C" AND YOU SHOULD FIND A PICTURE OF IT THAT CLEARLY SHOWES POSITIVE INCEDENCE IN THE LOWER WING AND THE DOWN THRUST in the engine,,it also shows the attitude of the elevator.

FireBee

My Feedback: (34)

I use 2 -3 right thrust and 2 deg down on all my 1/4 scale birds. For reference: Proctor N-28 with zenoah g38. Scratch Fokker d7 with Bryson 3.2 (50cc) and mounted my buddies busa pup with zenoah g26.
For 1/3 Sopwith Tripe I am planning da85 and same way 2 riight and 2 down.

All still climb when throttle is full. I trim for scale flight at about 45 percent throttle.

As to post 15 and the Sopwith tripe adjustable stab; one of my reference books has a pilot interview in which he said he loved the flying qualities of the Tripehound. He trimmed the stab to full up and made 22 consecutive loops on day!

R, Mike

abufletcher

For those of you who use right thrust, what's your preferred method of building it in? Do you like to slant the firewall or mount the engine with shims?

GerKonig

I follow Balsa USA directions. On a flat (perpendicular, or 0 -0 degrees) firewall, use washers under the mounting point of the motor to give the down and right thrust needed... No need to slant anything, just build perfectly square, and use some washers.

Gerry
PS: Worked for me...

abufletcher

And, of course, offset the engine so that the thrust washer is still in the center. As far as "following instructions" goes...well, that's now my strong suit.

fred985

piper cubs have a screw tuned by awrap around cable for stab inflight trim.as do most every light plane.

foodstick

This is not a set in stone fact, but I have found with the way I set it up (with a gas engine) that I usually end up with the motor 1/4 inch higher than center, and 1/4 inch to the right of center.

Then looking at the firewall from the front I will add one washer behind the mount top left and bottom right about 1/16 thick, I will put two washers on the top right making it around 1/8th thick.

Simple? or primitive? you decide ! hahahahahha

David Bathe

You will need some (say 3deg), not becasue of torque (aa common missunderstanding)... but because of the prop slip stream hitting the left side of the rudder.
Unfortunately right thrust looks odd on a WW1 model IMO. A couple of degs of down not so obvious to the eye... but right thrust, Hummmm.

There is a very simple solution though which is used in F3A: Mix rudder to Throttle.
Set up Zero, fly around, find the amount of rudder needed to maintain straight flight at full gass, land and mix that ammount to full throttle position. Idle- is 0. ;Max- the desired amount. A straight line mix will work to start (and possibly end) with. If you want to get picky, program a curve.

It's simple and works very well.
Definatley better than having an aircraft the slowly and constantly yaws left.
No right thrust is one of the largest contributors to why people have problems naturally flying in staright lines, prefering instead to fly in circles.

abufletcher

One further (final?) question: Does these engine thrust issues only apply to our models...and if so, why? As far as I know, none of the WWI round cowls had their rotaries mounted at an angle. But, I did read that the engine on the RE8 was mounted with up-thrust.

David Bathe

I guess it was a heavy airplane?

They've built in down thrust on full scale for years, but regarding right thrust...
I don't know if people completely understood what was happening back then. they knew it was a problem, but where unsure of the built in solution.
Perfering instead to do what I've suggested, mix it in - with your feet! or once airboarn, with a trim wheel.

There are many reports from WW2 reporting yaw problems and being "ready on the right rudder" during take off  being associated with engine torque, when we now its actually due to the prop stream hitting the rudder, not so much the engines torque/twist... which is an issue, but a different one. Still they knew the cure: feet and pedals. And having looked at a couple of full sized merlins and rotorys installed in Wwrbirds... I'd guess that there just wasn't any room to off set the engine anyway. They must have known... just couldn't impliment it. A couple of aircraft did have an off verticle fin though, which is the same thing.

I think it's probably more evident with models because of the far higher RPM we run and that we generally take of and fly at speeds that are far faster than scale.

smperry

My Feedback: (4)

Some good information here. I have built lots of smaller, electric powered WWI models, (Peter Rake and Aerodrome RC designs), and followed the motor thrust and flying surface incidences given on the plans. I've recently been moving to larger models, (helps to fly when my poor eyes can see the model in flight).

I have a Proctor Fokker D.VII kit as a first 1/4 scale WWI model. The kit recommended a Laser V-200 or a Laser V-300 engine, (both 2 cyl 4stroke glow engines). I went with the V-300 based on my experience that an over powered model will fly better at a lower throttle setting than an underpowered one wide open. The plans for the Proctor D.VII show the firewall located for the smaller V-200, so I will have to re-locate the firewall to accommodate the larger V-300. Fortunately the mount for the V-300 is a ring type which bolts flat to the firewall. Thrust can be easily altered by using washers like I used to do on my Cox .049 powered free flights I built as a kid.

I'm planning on building it with a straight thrustline and adding down and right thrust as/if needed. I also plan to offset the fin if the original had the fin offset. (My references are still packed from a recent move and my memory is unreliable). Does anyone's experience with large D.VII's indicate that this is the wrong, (or the correct), approach?

sp

GerKonig

No, the engine mounts in the center. In my experience the 2 washers here, one there really do not offset the thrust washer that much... I the cubs you compensate when mounting the cowling... It is really not that much...

Other people might have had different experiences, I can only write about mine.

Gerry

geezeraviation

My Feedback: (3)

Two degrees at six inches is 3/16 of an inch and is noticable. I always off set from center to compensate for side thrust. Angling the firewall can be done, some say a flat firewall doesnt stress the engine mounts as much as spacers, Ive done it both ways and have never had an issue with either.

geezeraviation

My Feedback: (3)

Abu, now having all this discussion, some pro, some con, what you must now do is decide what is best for Abu and carry on. Remember no matter what you decide to do someone out there will think you have done it wrong!

abufletcher

That's always the case, but I've found it's best to listen to other builders before I go off and do what I was going to do anyways!

GerKonig

Exactly. There is more than a way to skin a banana... (It used to be a cat). One could avoid the down thrust issue shimming the leading edge of the horizontal stab... But is would be more complicated. One could also use a lot of down trim on the elevator and no down thrust on the power plant.

Or, you could do neither, and when the model baloons and goes left on take of, you can blame the globe magnetic field shift or make up some excuse on your own:-) Say: My gyro is shot!

Let us know what you do and what the results were when you get to that point:-)


Gerry
PS: If you do A half of the wold will think you are crazy, if you do B the other half of the world will be sure you are nuts.

redbaron1930

One problem, especially if the plane has an undercambered wing is that the lift changes with airplane speed, so chances are it will never be perfect for all speeds.
I do not use engine thrust but adjust my horizontal stab to have it fly level at a certain speed (a scale speed) and then forget it. Above that speed the plane wants to climb, and below that it certainly wants to come down and has to be landed with power on. As a pilot I like compensating for these things, but I think it comes down to a matter of preference.

GianFrancesco

I agree with David; most of us have today a computerized radio that allows
all these adjustments.
In my Strutter I have set a 0° - 0° the side and down thrust.
Anyway the the tailplane incidence adjustment is allowed by rotating ( at ground) the "bottle" in the tail area; that means that all the "wires" will move together the tailplane; as per full size. A bit tricky but it works.

puplover

You are so right pimmnz totally 'British'. It is essentially a trim wheel turning a screw jack at the rear of the stab via cables. Ingenious but for the fact that it must have been heavy, producing a nose up attitude requiring the use of the system to bring the nose down!!. Rube G. maybe??

Abu, TK has an old Berhens Sop. Triplane in his rafters somewhere that I swapped him for an engine and I had built in this scale, moveable, stab. It was electric using a micro switch and servo setip. He took it out. That's Tom.

Jack

TKFOKKER

HM, OK
TK

Eindecker_pilot

I have right thrust on my 1/5 scale Eindecker & my 1/3 scale Pup. I think it helps, but never went back to see how it would behave without it.

Greg