I am getting ready to build the engine box for a AW 33% Extra 330L ARF.Can anyone tell me how much longer the left side panel should be to provide 2.5 degrees of right thrust?
Thanks,
Mike

It will depend on how wide the box is. 1/4" difference on a 1/2" wide box would be 22.5 deg. I think. Spread that out to 5", and it will give a much less angle. Tom

See if you can swipe the kid's protractor, unless you pass by the stationary store.

Here's how to figure how much shorter the right side should be:

take the tangent of 2.5, multiply by the width of the engine box

This will tell you how much shorter the right side should be from the left side

tangent of 2.5 degrees is 0.0436609429

example:

tan(2.5) x 4" wide box = 0.175"

so the right side should be just under 3/16" shorter than the left.

Don't forget to account for this when determining the distance from the spinner back plate to the firewall or the right side of the spinner might hit the cowl.

Ben

I bet you're looking hard for that protractor now Mike!

Like Vinnie says,get a protractor plus a piece of paper,pencil,triangle,& DRAW it out on the paper---no big deal.
Oh,a T-square would be good to....comes in handy when making planes.

Thanks Guys,I should be able to get it.
Mike

Over the years of building for others, I have learned what motor you build for might not be what the next owner might want...

Build you firewall about 3/4" shorter then called for in the plans with NO offset... then use spacers (offset spacers available from Roger at Aerografixs at 613-933-7296, www.aerografixs.com) to set your motor.

I sell alot of airplanes less motors... this is a great "universal" front end set-up.

Ron
R and D Aero

Ron,

I thought about doing exactly what you described, but how do you account for any changes in thrust angles with standoff's? Let's say you have a 3 degree angle machined off the standoff's, when you pass the bolts through you will need a 3 degree tapered washer on the engine backplate or the bolt head will will only contact on one side. Am I missing something, or just not seeing it correctly?

Ben

When I use standoffs, I have Roger cut the taper into all 4 of them. The reason I reduce the length of the firewall is so other motors can be fit that might not have the same exact dimensions as what you originally build for...

Have a chat with him... he is the only standoff manufacturer that cuts tapers (as far as I know) and is VERY knowledgeable about what works and what doesn't.

Ron

I did build the box on my 33% Edga square and had Roger make me the standoffs.He talked me out machining the taper because he said it be fairly expensive.He did however caculate the offset for me on his computer and make two of the standoffs longer than the others,but they are cut square.There was no extra charge for that.So far after about twenty flights all is well.I just thought I would do this right,not that there's anything wrong my Edge.
Mike.

SWB manufactoring sells an engine mount, although it isn't cheap, it already has 2.5 degrees built in and helps you align the 4 mounting holes with the left shift of the engine due to the offset. Check them out, could save you some time, it did for me.

And I also just made the engine box sides the same length and used 4 standoffs from Aerografix's all cut to same length, no offset.

I did buy the mount from SWB,but I decided put the DA aside and go with a ZDZ 80 instead.I think I've got figured out now,Thanks
Mike