Good Day Diggr

Yes I think its a mistake (in your case and setup) and I will tell you specifically why (agine with your setup). All that follows is strictly opinion based upon many inverted installations I have done for all the various reasons. However these days the only fully inverted installations I will still do with a conventional two stroke glow engine is certain all out pylon airplanes in which streamlining is worth all cost and additional hassle (you could loosely translate that word hassle as 'pain in the butt'. Notice the key phase in that previous sentence, Two Stroke.

The bottom line is a two stroke glow engine typically will suffer a much greater Tank/Spraybar Height relationship change than most four strokes because of the manifold setups of most four stroke when the engines are inverted. Now most all the responders are talking bout four strokes, well that something else and really does not apply at all to your setup Diggr.

Let me digress for a minute, Jester is the only one that hinted at the answer to your first question as to why most all kits and arfs of cubs in 40/60 sizes show a side mounted engine with a PICTURED two stroke. Most of these designs date from a period when two stroke glow is the norm and four strokes were rare. Indeed these designers were not stupid people and knew of the trouble most would have with an inverted mount in a cub with a two stroke glow and as Jester described Any model of a Piper J-2, J-3 or J-5 is gonna need a cylinder like appendage hanging out both sides and with a side mount you are half way there.

Also would like to explain just why it is that any typical J-2, J-3 or J-5 model seem to have such a problem with this fuel tank/spray bar relationship when using two stroke glow engines more than just about any other popular RC model:

The Cub has a very, very deep windshield and accordingly shallow firewall and of course cowl. This nose section behind the fire wall is also very short . The bottom line of the cowl on the full scale rises sharply right up to the bottom of the engine crankcase and this will allow simply no room to lower the fuel tank sufficiently when using a glow engine inverted on a model.

Lets take about your exact installation Diggr. Your engine an OS .40Fx (an excellent engine and fine choice by the way) you have checked you said and found you can have the spraybar even with the middle of the tank, Ok now lets talk about this height relationship thing agine. This relationship is affected by Degree, in other word things can get progressively worse or better depending on the degree of this change from the ideal. I think you will find that ideal and even most OS manuals (of two stroke glow engines) recommend somewhere with the spray bar around level with the top of the tank or just a little higher.

So what does that mean for you with your spraybar level with the middle of the tank? Well that means your engine may run just fine! It also means you may or may not have to use Hemostats on the fuel feed line between and especially after fueling, It means you may or may not have to always be attentive and carry your ship nose up as well as informing others to do so who may pick up your ship. It means you may or may not need to keep a rag over the engine/nose when sitting in the hot sun after fueling. This lat one is a fun one that no one ever thinks of and most definately can initiate a syphon quicker than snot, that fresh cool fuel in a full tank just heats right on up and starts a syphon right on up and little loops of fuel line seldom prevent this.

So its all a matter of degree an what you are willing to put up with.

Yup all the above just that old opinion thing agine John