Paulparkflyer

Hi guys,

Being a beginner this may be another "silly" question but,

When mounting the motor and prop is there any reason why on some models it seems to be mounted at angle not in line with the fusalage,

I have just purchesed an E-flight apprentice to cut my teeth on and it seems the motor is mounted at a strange angle to the firewall?

The plastic mounting adaptor for the motor is deliberataly moulding this way so just wondering what the reason is or if it is only done on trainers for some reason,

Cheers,paul

CGRetired

My Feedback: (1)

This is not a silly question. I'm sure you've heard that the only stupid or silly question is one that you really wanted to ask, but did not for fear of being 'silly' or 'stupid'. Not so. Ask away! No one will laugh, well, not on-line that is..

Most if not all aircraft have a thrust angle to offset the motor or engine torque. As the motor or engine rotates the shaft and prop under power, Laws of Phisics say that for every action there is an equal and opposite reaction. That means that that the aircraft fuselage will want to rotate in the opposite direction of the motor or engine shaft and prop. When it is on the ground, for the most part, this tendendy to rotate, which causes the airframe to want to turn and then bank in the opposite direction of the torque, is offset by moving this thrust angle slightly to one side or the other. That is usually a couple of degrees to one side or the other, depending on rotation direction of the motor/engine shaft and prop (clockwise or counterclockwise... anticlockwise for you.. ), usually, I believe, right thrust.

Hope that helps.

CGr.

jetmech05

That Coastie is on the money...Semper Fi...sorry had to be done..haven't givien you a hard time in a while

CGRetired

My Feedback: (1)

Hey Jetmech.. how goes it? Now now.. you have family within the family now..

I recall when I was assigned to go to a Navy seminar in San Diego, there was a young Navy man that kept calling me "Coastie". He thought he was being "cute". I never called him squid, mainly because I was one before I was a Coastie.. ha.. but one crusty Chief Boilerman called me "Puddle Pirate". I laughed my butt off over that one.. never heard it before.

Anyway, I wish you and yours (especially your OWN Coastie) a Happy, Safe, and Prosperous New Year!!

CGr.

lordmerren

Actually my understanding of the reason for thrust angles is completly different from CG's. I feel it has nothing to do with countering engine torque. I always understood that the right thrust was to counter the spiralling slip stream which hits the left side of the rudder/fin and produces a left turning affect on the plane. Also the down thrust is to counter the p-factor, where high angles of attack causes the downward moving propeller blade to bite into the air more than the upward moving blade, also causing a left turning affect. My 2 cents.

Lm

CGRetired

My Feedback: (1)

That too... But, as a beginner, he may not be ready for "P factor" or "spiraling whatever" over the wing.

Paulparkflyer

Thanks guys,

As I am also building a cub with electric conversion is there an easy rule of thumb for setting up the motor angle for best/easiest flight ?
The manual that came with the plane doesnt go into any detail there,

Or do some planes have the motor set inline with the firewall and rely on the pilot to correct when flying?

Thanks, Paul

CGRetired

My Feedback: (1)

Most kits/arfs put the thrust angle in the build process, even without your knowing you are doing it. Trust that the kit/arf is built as such and go for it. Most likely, it will be just fine. Just build the thing right... meaning put the right parts in the right place and glue them down.

CGr

Paulparkflyer

Thanks again guys,
On studying my Cub kit more closely it does have a very slight thrust angle built into the firewall position so will just mount the motor square with the firewall and all should be ok,
Hopefully the up/down angle is also taken care of,

I guess I was thinking too deep into it instead of just building it but my worry was that maybe the manufacturer of the kit assumed the builder would have more knowledge than me and need to determine an angle but luckily I think it is all done,
I must admit the instructions dont have much detail,

Cheers,Paul