Side Thrust Off - how to correct?
 

Hi.

I'm building a Venture 60 Kit (my first build). I mounted the engine mount and then build the fuselage. The fuselage is dead straight, but it looks like the piece that the engine is mounted to is angle just slightly. Therefore, the side thrust is off by a couple of degrees. The down thrust is correct.

How can I correct this? Can I place a couple of washers behind the engine mount? Or sand the mount?

RE: Side Thrust Off - how to correct?
 

"the piece that the engine is mounted to", would this be the firewall? Is it meant to be at an angle? Bruce Tharpe at BTE is VERY good at answering questions like this if you call him.

RE: Side Thrust Off - how to correct?
 

I just reviewed the instruction manual online and I don't see how it could be off if you followed the manual. Everything is tab into slot type of build. It could just be an optical delusion.:D

RE: Side Thrust Off - how to correct?
 

Washers are the best solution until the airplane has been flown to verify the thrust angles.

Bill

RE: Side Thrust Off - how to correct?
 

I am just getting done building my Venture and I don't have any andgle to my Firewall. You might call BTE and see. Maybe I did it wrong or maybe I'm just not that observant. Let me know what yours looks like. I'm quite pleased with the way mine is shaping up!

RE: Side Thrust Off - how to correct?
 

Have you measured the thrust angle after assembly? You should have some downthrust and some left thrust built in. If the sidethrust is 3 degrees right or less, fly it first, this may be just the amount needed. On some of my planes, I have had to have as much as 5 degrees down and over 3 degrees right.

RE: Side Thrust Off - how to correct?
 

I'm pretty sure that when I glued the fuselage doublers together, the right inside doubler shifted forward a little when I clamped them them together. I think this shifted the firewall notch forward enough to move the thrust line to the left.

I considered this also, but what effects can I expect if I attempt to take off and the side thrust is angled 3-4 degrees to the left? I've read and been told that that shifting the thrust angle to the right is ok, but to the left may cause some issues.

RE: Side Thrust Off - how to correct?
 

Foos, can you post a pic?

RE: Side Thrust Off - how to correct?
 

Yeah, gluing the doubler is a critical step. I was hoping you had gotten it right. It's about the only thing that could shift the firewall angle. That or building a banana and I took your word on that.:D Now that it's glued up it's plan B time. First fly it and see how bad it is. You could get a new mount (an ARF "clamp" mount) and cock the engine a bit sideways in it. Washers work but tend to sink into the wood, use strips metal instead to spread the pressure out. LAST choice would be sanding because IMO it is hard to do straight. If you had a 2 piece mount it would be easier, again IMO.

Just a few of the options. More will be offered.

RE: Side Thrust Off - how to correct?
 

BTW, when I do doublers like that I use either 30 min epoxy or Tite Bond II but I CHEAT and tack each end in place with a drop of CA so they can't shift while drying.

RE: Side Thrust Off - how to correct?
 

Yes, I'll get some pics up tomorrow. I called Bruce and he suggested using the play in the engine mount to straighten the thrust line along with some other suggestions. That seems to be the best choice at this point. Looking down over the firewall and onto the plans, the firewall is definently off. I thought about drilling additional holes in the current mount, but I think I'll just purchase a new mount. 8 holes instead of 4 doesn't seem like a good idea.

The plans call for 0 degree side thrust and -2 degree down trust. The downthurst is spot-on.

Funny image. At least the fuselage is straight. Bruce also suggested engine mount wedges by Ernst. Any experience with these?

RE: Side Thrust Off - how to correct?
 

Never used them but I hear they work good.

RE: Side Thrust Off - how to correct?
 

here's a couple of images:

RE: Side Thrust Off - how to correct?
 

You could always do what I do...

Take off the mount and where it mounts to the firewall ( the flat side ) push that up against a belt sander, or any form of flat sander, then slightly tilt it as it sands some of the material away.

That way you can put in 1-2 degrees of corrective offset, while permitting the mount to lay flat on the firewall when you are done.

You can always throw it away should you change engines later, as they are relatively cheap compared to the effort in fixing all of this.

It's also far more secure and stable than shims and washers, since the force is distributed evenly against the firewall and mount.

This is obviously easier to do with plastic mounts...

RE: Side Thrust Off - how to correct?
 

I purchase a package of Ernst thrust wedges and they worked great. The package comes with 3 wedges (3 degree, 2 degree and 1 degree). I used the 2 degree wedge and it straighten the engine perfectly.

RE: Side Thrust Off - how to correct?
 

That's good to hear.:)