I just recently read the new "From the ground Up" article in the latest MA, and had a few questions about the right thrust section. It tells you how much right thrust you need, and how to figure the angles, but how do you adjust the right thrust?, do you mount the engine off center of the mounts? Do you add washers behind the left mount? Whats the best way to do it?

Thanks

LT-40

Hi!
Side trust!! Never use it !!!!
On most airplanes side trust isn't needed. Simple as that!
Down trust is used on high winged airplanes and up-trust on PBY Catalina type airplanes.
Most other models have 0, 0, 0 degree on engine, wing and stabilizer and fly just fine.

Regards!
Jan K
Sweden

Jaka, his question wasn't, "Does anyone think right thrust is necessary?" I have an airplane that could benefit from right thrust and I have been inspired to try fixing the problem after reading that same article. I am thinking of going with some small washers between the firewall and the engine mount. I think I need the right thrust because I need to correct with the rudder trimmed to the right for straight flight. The problem with using the rudder is that this changes as airspeed changes.

If you want to just go punch holes in the sky, right and downthrust are probably not necessary. But for those occassions when your trying to correct a bad habit, some designs do infact benefit from one or both. For example, my GP CAP 232-40 has 5 degrees right thrust built into the firewall, and I added some downthrust to improve its flight.

Adding right or down thrust is as simple as adding some washers behind the engine mount, assuming your engine mount is screwed into the firewall. Its not a precise science. Try one or two washers, and if it improves, then try adding more. Find your optimum and then have fun.

As for off center, if the plane is designed for right thrust, then you will want to put your engine mount slightly off center (you'll have to figure out the distance) to keep your propellor on center. If you don't, however,you probably wont notice the difference. Its only a fraction of an inch.

Good luck,
Brad

Good advise from Brad, I had a Big Lazy Bee that wouldn't get off the ground with a 46 engine. When I went to a 60 engine the plane was pulling so hard to the left when I throttled up that it was very hard to steer on the ground. I added some right thrust with a few washers between the firewall and the engine mount and that solved my problem. I haven't seen a need for it on my planes that have the 40/46 size engines but maybe that just me. [8D]

the correct way to add the right thrust is during the building process.usually 2-3 degrees is all that is needed so the direwall is built with that amount of offset in it.then the engine needs to be mounted off ceenter a tad to put the prop back on the centerline.trigonometry helps give you the required demension when you decide on the amount of degrees.I split the difference and use 2.5 degrees.And yes it does help on scale aircraft with conventional gear.but as others have said,if the plane is already built then adding washers or wedge shaped shims behind the mount will work fine.I prefer to have the entire engine mount secured to a solid back to prevent any distorting or unneccasary stres that could cause flexing or a crack and use thrust plates or even cedar shingles that are fuel proofed and mounted behind the mount,gives a solid ,strong backing to the mount.

It's not just models that need right thrust and/or down thrust. I have been looking a plans of a full sized Beachcraft Staggerwing and it uses 2.5 degrees down thrust but no right thrust.

Don

Hey thanks guys, this is just what I need to know. I believe that this right thrust is totaly nececary because this plane will be coming off of the water, and the "P" factor from the rotating prop is much more noticeable.

Thanks again,

LT-40

Three weeks ago I was flying my SPAD Debonair off the water with a TT Pro 46. Zero Right Thrust, Zero Down Thrust, Zero Problems on take off. Well designed floats and an appropriate water rudder can really help keep the plane straight during your takeoff run. Check out the Seaplanes forum. And if you're anything like me, and your prop is just slightly too long, it might hit the water occassionally and actually drive the plane more to the right!

If you re-read the article in MA, it describes what conditions you would observe that right thrust might correct. Don't add right thrust unless the design calls for it until after you've had a chance to test fly.

Good Luck!
Brad

Ya, but if the plane pulls so hard to the left on a high speed taxi that you need full right rudder to keep the plane going straight down the runway, then you definitely need some right thrust added to the angle of the engine mount. This I know from experience!!!! [X(]

Hi!
...Or perhaps have a look at the wheels....
My Q-500 racer pulled hard to the left onits first take off run. It was the left wheel that was binding.
Regards!
Jan K

Good point. The LT25 uses bolts as the wheel axles. Its hard to keep the nuts tight in the correct position after a few dozen flights which results in the nuts moving in on one or both of the wheels acting like the brakes are on! I got fed up of the constant adjustments and went to a standard wheel axle with wheel collars. The plane, the way I built it is too good to give up. I put minimum dihedral in the wings and made it attachable with four 10-32 nylon bolts and put an OS 32SX on the nose. Makes the plane easy to fly in the wind and has lots power. I can take off in 10 feet if I give it full throttle and full up elevator! [8D]

With most models isn't the thrust usually built into the firewall when you install it? Most of my planes did.

YLike he said, you can just look down on top of the fuselage at the firewall and see if it has and angle to it for right thrust

The easiest way i know to add right thrust after the plane is built. is to use Earnst thrust plates. they come in 20-40 and 60 size. use the one that works with your motor mount. I have used washers in the past to experiment. Problem with the washers is the dig into the firewall after awhile so your right thrust becomes less than where you started. Try the earnst they come in one package with 1,2 and 3 degree shims for under 3.00 dollars.

Dennis