Thrust angles
 

Hello all
I am just about to fix the firewalls in my new twin and was curious as to what thrust angles others have used with success. I have read some set their twins with 1-2 deg "toe out" others set left engine 0 deg right engine 1-3 deg right. My last twin was set up as per the latter and seems to work ok.
Any comments? Regards Steve

RE: Thrust angles
 

I have heard all that too. I think you will find that Bill and I both disagree with the "Popular" ideas about toe out to help engine out. We both go with "point them straight ahead" or 0 degrees toe.
Now, as I tend to push the envelop a bit......(OK A LOT!!!) I have found that some of the bashed planes, I have had to add down thrust to vertical climb and my poor attempts at hovering, but that is to compensate for the plane pulling on vertical climbs.
If you try to angle the engines out to compensate for thrust of only one engine, the angle will be very high.
Concentrate more on larger rudder, with large deflection capability and long tail moment, both for stability.
What are you building?. If this is some sort of Bash, consider to hold off mounting the firewalls a bit. Install the radio and servos everywhere.If the covering is heavy, might consider to cover it first. Bolt the engines, with mufflers, to the firewalls. Now, using rubber bands or similar, move the engines forward and back to achieve balance before gluing in the firewalls. Save a bunch of added weight to balance the plane.
Good Luck,
Twinman

RE: Thrust angles
 

Thanks Twinman
I agree about not angeling the engines to compensate for a lost engine (lets face it you would have to have some serious angles to help in that situation). I like the idea of angling the one engine to help with torque roll as I will not be bothering with counter rotating props (more trouble than its worth) Is torque roll such a big issue on a twin ( with both engines on song of course). I guess the best bet would be to build in some room to adjust the engines on completion.
The aircraft of the building board is a 1/7 scale P-61 black widow in which I am using a pair of MVVS 1.44 ci opposing twin cylinder 2 strokes (low vibration) gotta love the sound of a pair of twin cylinders.
Thanks again Steve

RE: Thrust angles
 

TWIN -TWIN CYINDER ENGINES DROOLLLLLLLL Slobbbbbber!!!
Oh, Sorry.
The angle I was talking about, is down thrust to reduce the pull, in my case, "up" as the plane goes into a "hang on prop."
Actually, the torque of the engines is somewhat less on a twin, as the "Twist" is not on centerline of the fuse.
There are other factors that do play into, such as P factor that Bill, the co-moderator, can explain much better than me. I am just poor old country boy, trying to keep my poor plane in the air.
Send Pictures!!!!!! Hurry!!!! OK, Just the engines!!!
Twinman
PS Glad you did not worry about counter rotating props. Too much trouble, and in this case not to scale. The P-61 did not have counter rotating props.

RE: Thrust angles
 

Steve:

I too am a fan of multicylinder engines, at the moment I'm trying to get Marc Linville (Technopower) to build me a pair of 7 cylinder radials, he says next year. Don't know if I can wait, might have to go with some other engines. They will be for my latest F7F. The first F7F is shown in my avatar.

But I've heard some nasties about the 1.44 MVVS twins.

Please, run them in on a stand, and make sure they are absolutely reliable. You are going to have too much time and effort, not to mention money, in that P-61 to lose it because of unreliable engines.

Alternates would be the Magnum 1.60 twin, the Saito 182TD, or even the Saito FA-170R3, the three cylinder radial.

Don't misunderstand. I'm not saying you will have problems with the MVVS engines, and it's possible all the nasty I've heard has been one owner and one engine. Just make sure yours are good.

Bill.

RE: Thrust angles
 

Bill,
Et tu Brutus??? More guys with muticylinder twin engine planes?
If you change your signature from "Real Airplanes have Two Engines " to "Real Airplanes has two engines and more than one cylinder per engine", I will never speak to you again!
Twinman

RE: Thrust angles
 

George:

I don't have the radials forthe F7F yet.

But it's all a matter of putting your money where you want it, and ignoring social pressures. My house in Maryland was more than $4K/month, down here I'm renting a trailer for Sam (the cat) and me. We have to be careful not to step on, run into, or bash our heads on the airplanes, but the change in housing left me with a lot more money to play with.

When I had a job and wife I had to pay more attention to other people's opinions, but now I can do pretty much what I want.

And out of deference to you, I will not add any reference to multicylinders to me sig line.

Haw.

Bill.