I had a project I started working on a couple of years ago, but had to put on hold when we moved.  A post in a thread over on the CEF reminded me that I needed to finish it up real quick so I can fly it at S.M.A.L.L. in a couple of months.  I was originally going to put it in my Q-Tee, but decided that a motor glider would be better to test the system out first.  I don’t have one at the moment, but the post had a foam glider with a 1/2A engine grafted to the nose.  Actually looked pretty good.  We’ve all seen them.  But, I don’t want to do a graft on the nose.  I do have a power pod that’s been sitting in a box for a few years and thought that that would be a fun afternoon project.  It is one of these Cox beam mount pods:



Now, I know the rules for down and right thrust for tractor engines, but I don’t remember ever reading about thrust lines with a power pod.  So, I went to OZ and did a search by putting “power” and “pod” in the search fields.  I downloaded 24 sets of plans for gliders with power pods, figuring I could just look at the average thrust lines and get an idea of how to set the pod.  Wow! Wide range.  Most were somewhere between +3 and -3 degrees.  One as low as -6 degrees and one at +16(!) degrees.  One design wasn’t even going to commit to a thrust line, so the pod had a pivot bolt and slot that would swing the thrust line between -15 and +15.  I guess that’s smart in that you can set your optimal thrust line for the finished plane/engine.  But the plans did not give a suggested starting position.  I know that with elevator control it's not critical, but I'm wanting to set this up for  rudder only control, so the thrust line has to give the glider a gentle climb under power with the plane trimmed for a shallow glide engine off.  Going old school here.

So, is there any good thumb rule for power pod thrust lines?

Mark