SonexBuilders.net

Hi guys,

Since the factory rotax mounts for both the B models and the legacy versions have been out for a few years now, I wanted to know if anyone has done the weight & balance calcs using them. I am not so much concerned about weight as I am CG. From what I understand, The factory engine mounts push the rotax back 3 inches, even though the engine ways about 20 lbs lighter than an aerovee installed. I am worried that CG will be too far aft when fully loaded at 1150 lbs.

If the cg is too far aft, are they ways to compensate for it? Adding a little extra weight to the front, maybe? Any info/suggestions would be helpful.

I will be doing my weight and balance in about two weeks and will report my results. To offset the weight issue, I am using a three bladed prop and a 2.25 nch prop extension that is significantly heavier than the AeroVee propellers commonly used. I also have a muffler. My cowling will also be heavier because it also has to be extended and tapered to fit the extension and the prop spinner. The cowling will also have ducting for the radiator and oil cooler. I also have a cabin heat system ducting hot air from the muffler shroud that adds some weight. If I need further weight up front I will add the Sonex smoke system.

Jake

Correction: it is a 2.25 inch prop extension

Thanks for the info! I like the idea of using the heavier, 3 blade ground adjustable prop. I wanted to use one of those anyway, and the fact that it puts that extra weight as far forward as possible will definitely help with cg.

SonexN76ET wrote:Correction: it is a 2.25 inch prop extension

Hi - I have just opened a new, closely related topic to this one.

I would ask;

What made you decide you needed a prop extension?
Why the 2.5 inches ? (longer/shorter or non at all)