Billy

My Feedback: (15)

It is all the same if I put some right thrust angle on a plane or if I build the firewall straight then mix rudder with the throttle.

I am building a plane which will have a very powerful motor for it's size.

Thought please.

Thanks,
Billy

ktcanuck

Thrust angle will be effective at any air speed and thrust level. Has to be the preferred route.

bubbagates

My Feedback: (32)

It's really not all the same. Do the thrust angles first. Let's say you end up with needing 3.5 degrees of right thrust but can only get 3.25, then you mix rudder to throttle to get the rest. You also need a downline rudder mix as well, don't forget that. Why you may ask, on the downline, all that right thrust is going to pull the nose to the right so you need left rudder at low idle to keep it tracking true.

Mick B

I agree with Bill.

It is critical to add both down and side thrust to make an airframe track true.

Adding elevator, rudder and aileron to compensate for improper trust line management will result in a slip as the airplane tracks through the air. If you have ever watched several airplanes flying around the field, you will probably see an airplane that, when watched closely, looks like it is flying a little bit sideways or nose down while in level flight. This is the result of either servo throw adjustment being out of wack or poor thrust line.

It is important to check that the manual adjustment of your servos to remove any trim offset that you may have put in electronically. This will allow you to use the trims on the radio for fine-tuning while in flight and furthermore will allow the plane to track more smoothly while in flight.

Adding adjustment for thrust line is also simple, however a little bit time consuming. It involves adding washers or other shims between the firewall and the engine mount. It is also possible to add the shims between the engine mount and the engine itself but you may need to redrill your engine mounting holes in the engine mount to get the proper sideways orientation. I prefer to just add washers between the firewall and engine mount as it doesn't require any cutting or drilling.

I once had a friend who worked in a machine shop cut a motor mount to obtain the correct angles. It worked very well but I needed the recomendation from the kit supplier to get it right. Now, I prefer to do the washers as it can be done at the field.

Happy Flying!

Remember... Only the take off is OPTIONAL!!!

[8D]

Mick

ggraham500

My Feedback: (4)

1 average washer approximates 1 degree of angle, correct?

Zeeb

My Feedback: (41)

Uhh.... NO

Having just went through this issue with one particular model I can tell you that washers vary in thickness, even those out of the same bin at the store.

I'd installed 4 fender washers as spacing when the engine was originally installed and checked the thrust angles which were okay, not perfect but close enough. I later had to pull that engine to go through the carb and when I re-installed it, the thrust angles were all screwed up. So I pulled it off and measure the washers, they went from .055 to .086 thickness. I'd just got lucky the way I installed them the first time and basically wound up with 0 degrees right thrust when I re-installed the engine.

I've found that standard size flat washers run anywhere from about .020 to .045 and in experimenting with this model and another similar one using standoffs for spacing a .040 produces a 1 degree change at the prop flange.

Now there are formulas for measuring to get the offset, but a simpler way is to just use something like the electronic protractor in the H9 incidence meter. Just put the model on it's side, use the first fuselage former for a reference and then check the prop hub. Works great and is quick and easy to do. Set up the thrust angles according to the manual if that information is there, if not just go with what you've found works and then some adjustment may be necessary after starting your flight trimming sequences.

There are those who advocate using 0 degrees of right thrust angle for various reasons, and some use less than what I like, so as you can see it is something of a personal preference on how much to use. Up or down thrust angles are a different story....