winglift

My Feedback: (10)

I am building a Bridi Utter Chaos with an OS .61 FX engine and there are no thrust corrections built in and really no room for it. It is an extemely tight fit. I am assuming that it was built and flown this way as it was built to plans. Any ideas?

Balsawings

I'm building the Super Kaos and have the plans for the Dirty Birdy and neither one uses any right thrust. Apparently Joe Bridi didn't use any and must have used rudder corrections. Takes quite a pilot to manually input rudder to offset the tork of the engine. We can easily use programing in todays radios to add rudder mixed in with throttle to offset the tork. I personnally prefer to use rudder mix than right thrust. The vertical down lines are straighter without the right thrust.

If your using a computer radio you will want to mix some right rudder. You want the rudder to have no offset at low throttle and slowly increase to maybe as much as 10% at full throttle. You will need to experiment with the mix to find how much the plane needs. Fly the plane away from you into the wind and pull a vertical up line. Add rudder until the plane flies the vertical without pulling to the left.

Bob Cox
SPA 374

winglift

My Feedback: (10)

Thanks for confirming what I was thinking. It does make some sense though, if the thrust line in inline with the centerline of flight then it would theorectically track better.

NM2K

My Feedback: (14)

The problem with engine right thrust is that it becomes left thrust when inverted. I build mine straight ahead, no right or left thrust.


Ed Cregger

dhal22

thx for that comment Ed. i've always built straight ahead. maybe my 1st trainer back in the 80's had built in thrust, but i've never had a problem with a straight engine setup.

winglift

My Feedback: (10)

I appreciate your comments Ed and dhal22. Now I am really interested in this for future building and flying. How long have you been building and flying and if you are building a kit, do you take the thrust correction out?

dbacque

My Feedback: (3)

I've had some planes that perform best with thrust line offset and some that fly great with none. I tend to trust the designer to have done his job and worked out things like optimum thrust line. I usually won't build a plane without knowing something about how it flies or knowing something about the designer.

With Joe Bridi designs you can trust that he's done his homework and worked out the kinks like thrust lines and incidence.

I have an 18 yr. old Super Kaos and a new Dirty Birdy. Both of these planes are built with no right thrust. I think the Dirty Birdy has 3 degrees down thrust, don't know on the Kaos, built it too long ago. Both these planes fly beautifully with the thrust lines Joe put on the plans.

If you built your Utter Chaos to the plans you'll have a great flying airplane.

Dave

Mad Man Marko-RCU

I have an old (1985) Utter Chaos with OS 61FSR. Built to plans no thrust offset. Flies fine still any offset can be easily done with rudder throttle mix (9ZAPS). I would however if I built another one enlarge the vertical surfaces about 5-10%. I think that Ed is right about using rudder rather than thrust. Thrust is also dependent on throttle setting and is fixed a mix is programmable for the throttle curve. Extra fin and rudder would make the knife edges easier to carry and require less surface deflection and mix. Also make sure that yours is balanced on or just slightly behind the shown CG. This will also help knife edge, rolls andspins but still slow right down to land.

May have to build a new one for myself.

Hope this helps.

Peace

Mark O

NM2K

My Feedback: (14)

We're just talking here, chewing the fat. I'm not trying to tell anyone that they are wrong and that I am right.

Things were really changing fast around 1970. Lots of old building habits, such as right thrust and carrying too much positive wing incidence, were held over in some models that would have flown much better without it. The jump from reeds to proportional was quick, but the aerodynamic philosophies didn't keep up with the technological improvements. Early proportional systems had terrible system resolution to boot. Hence the need for aerodynamic solutions to problems such as poor servo centering (diamond shaped airfoil for horizontal stabilizers are one example). In less than a decade, pattern went from models that were basically free flight models with R/C interruption to models that were neutrally stable and which required constant flying inputs throughout the flight. Is it any wonder that some old design habits were retained? Not hardly.

A sport flyer that does not fly his old pattern model in a neutrally stable manner can benefit from the increased ease of flight that is provided by right thrust, down thrust and a bit of positive incidence in the wing. However, these same features can provide a model that is a real cow when flown inverted.


Ed Cregger