Side Tracked

Well I can honestly say absolutely nothing has been achieved on the Sonex this week. I had to carry out a bit of routine maintenance on the Aeropup and also fit in a trip to Perth.  Part of the maintenance was a cylinder leakage test at 50 hours. Needless to say things didn't turn out too well.


1- 62/80
2- 74/80
3- 72/80
4-  62/80


It turns out that two exhaust valves were leaking and that further attention was obviously going to have to take place. I ran out of time that day and then went to Perth the next. I managed to get home on Sunday morning and shot straight out to the airport to take the heads off and check the barrels and pistons. I was just spewing to find some really bad vertical scouring on the two rear cylinders and, pulling a few valves out of the head, to find some seriously sick looking valves and seats. The valves had really been hammered into the head. This would explain the constant need to loosen up the tappets to maintain clearance. I investigated further as to why I have had to do valve work in such relatively short time.  I have always been dubious about the initial setup regarding the compression ratio and needless to say, yes, I had set it up incorrectly. Hopefully anyone reading this blog, and building an Aerovee, learns from my mistake. What I had actually done, was when reading the chart contained in the Aerovee assembly manual regarding setting the compression to 8-1,  I had read the measured protruding piston as a +.020  instead of a -.020.  So I was required in this situation, to add shims, but I failed to add enough so ended up with a much higher compression ratio. I had actually ended up with around 9-1 and didn't realise. So higher compression = higher heat, not cool. Bad joke.


I'm in the situation now where I will have to spend some good time and cash rebuilding this bad boy  because of something I should have done right in the first place.  I have to choose now as well whether to go with the new Mofoco 040 heads that Sonex are supplying or rebuild my current CB 044  heads. Everything I read on the net doesn't seem too positive on the Mofoco heads however if Sonex are supplying them, I expect they have been tried and tested and found to work well. The problem with rebuilding my current heads however may be that the aluminium may not pass the hardness test. Excessive heat softens the alloy and may render them useless so that will have to be checked I guess when I get home.

I'm hoping that when I build the motor this time and have everything right I may gain a few ponies as it seems that it has always been a pretty anaemic engine. With the new ground adjustable(lemon) Sensenich prop I was unable to turn it over 2850rpm static. The prop is another saga that I'll leave for another day but just a short note;  I flew it for about 6 mins and the vibration was horrid. Having spent close to $2000 Australian for a prop that was going on the Sonex turbo, then being told it is not compatible,  is frustrating beyond all belief. I just have no idea at all what I am going to do about it.


So I'm at work now this week and just trying to sort out the parts for this repair job. I really want this plane going ASAP as there is a Fly in organised in the near future. I would like to take my own plane so I need to pull my finger out on this one.


About the only thing 'Sonex' related to this update, would be that I have ordered the missing hardware from Aircraft Spruce for the dual controls. The original hardware kit was basically on back order for months and months, and you may possibly have guessed it, I got an automated email from them a day or so ago saying this order is delayed as well. I will really have to rethink where I get the rest of my stuff from for this kit as it just chews the build time up waiting for those little things that should be easy to get hold of. 


I was missing a few other items from my main Sonex kit too, like the brake handle and flap levers and things like that made out of ally parts. A quick email to Sonex and they have sent them to me no worries. I'm just waiting for them to arrive now but I think by the time I get home they will be waiting for me. Sonex as a company really do look after their builders.