Thursday, January 28, 2021

FInishing up the firewall forward wiring

The past few weeks have been mostly about firewall forward.  I managed to get the CHT sensors, EGT sensors, oil pressure sensor, oil temp sensor, manifold pressure sensor, both alternator amperage sensors, and the fuel pressure sensor all installed and wired up.  I also finished the firewall forward installation of my SDS Electronic Fuel Injection and Ignition system (EFII) installed.  

The throttle cable and the prop control cable are both installed and connected although I still have work to do on the prop lever in the throttle quadrant.  I plan on anodizing it black to match the throttle lever.  Speaking of prop governor cables, I had to modify my top cowl because the "notch" I cut into the shroud for the governor was interfering with the full motion of the cable arms.  Oh well...its only fiberglass work.

I did my first install of the exhaust system.  Well actually I only installed the down pipes from the cylinder flanges so far.  I needed to do that so I could drill and install the EGT sensors and associated wiring.  The #1 cylinder downpipe also has the O2 sensor bung welded on at about 12.5" down from the exhaust flange. 

I had to do more work on the top cowl as you will see below.  The #2 cylinder injector was standing a bit proud of the top of the baffles which means there is a significant possibility that the normal shaking of the engine will cause the injector fitting to come into contact with the top cowl.  To remedy that situation I have modified the top cowl by cutting out the honeycomb material on the inside as well as a little re-clocking of the 90 degree elbow on top of the injector mount.

The fuel system forward of the firewall is now complete as well.  I ordered some pressure tested, fire sleeved hoses from Tom at TSFlightlines to finish up the job.  I love Tom's work!

I'm sure there were a dozen other tasks that I forgot to mention in this post but maybe you will spot some of them in the pictures below.

Backup Master Solenoid, XC solenoid, ANL fuzes, and current sensors wired up.

Injectors plumbed and wired up.

Lots of scrap wire on the floor from all the FWF wiring work

This is the number 2 injector that I discussed above.  You can't really see it in the picture but there is only about 1/4" of space between the cowling and the injector fitting.

Odd looking picture but this is looking aft into the intake snorkel on the scoop.  I was measuring the location so that I can align the Filtered Air box.  It looks like it came out perfect!

Another hard picture to visualize but this is looking outboard from the spinner opening at the prop governor and its associated fiberglass work.  The top baffle plate for the governor is not installed so I can see what it looks like outboard.

Friday, January 1, 2021

Its all about cooling

One of my biggest concerns about flying this airplane for the first time is the engine cylinder head temperatures. Traditionally the first hours of an engines life are hot as the rings seat themselves. On the 9A I had piston oil squirters that helped keep the cylinder head temps down, but this engine does not have this option. My only option is to make sure I am making the best of the cooling that is available. That brings me to my last several weeks of work. Cooling mods. I used the baffle kit that comes from Van's and its a huge help, but its designed for a slightly different engine, and even the inter-cylinder baffles that come with the engine fit very poorly. Below are some of the steps I have taken to try to keep the air moving through the cooling fins on the cylinders and keep the cooling drag to a minimum.

The plans call for a series of slots cut into the lower scoop section of the cowling to aid in cooling air flow through the engine. This added air flow is necessary for time when heat load is high such as takeoff and climb phases of flight. They are not needed when in cruise and because these slots are always passing air they create a bit of drag. I decided to install these cowl flaps to eliminate the cooling drag when its not needed. The AntiSplat Aero cowl flaps I purchased are designed to be installed in the bottom of a cowl that has a honey comb core but the scoop area on the 10 cowl does not have honey comb in this area so I had to build up a mounting platform so that the installed flaps are flush on the outside. You will see a picture of the outside down below. To make this mounting platform I used my 3D printer to print up those two white forms you see sitting above the openings. One side was slid into the opening from the outside and the other was fit on the inside so that I would have a smooth flat surface mount.
Up close view of the mounting platform as I was testing fit.

Both flaps installed (no bolts) inside view.

Both flaps installed outside view (looking up at the bottom of the scoop where it overhangs my workbench.

I also formed the fiberglass duct around the top cowl inlet where the prop governor sits.  Still some cleanup work to be done here.

Oil door with hinge and latch cutouts complete.  I did have to fill those two miss-drilled holes on the hinge location and then re-drill the hole.  It took quite a bit of time to get this door to fit the opening properly.
This is the door after I got it all put together.  I did add a bit of carbon fiber plate to keep the door rigid.  This is simply a plate of carbon fiber that was left over from the instrument panel cut out adhered to the door with flox.  It really stiffened up the door.  I had originally used the honeycomb method that vans suggests but the latch I am using does not work well with that type of support.  I used carbon fiber on the 9A and it worked very well.

An outside view of the door after I had faired in the opening a bit.  I am going to have to to a little more sanding as there isn't enough edge distance to allow for paint.

Here you can see the wraps that I put on all cylinders.  The wrap is simply 9oz fiberglass impregnated with ultra black RTV.  These areas are locations where the baffles tend to leak a lot of air and any air not going through the cooling fins is just wasted cooling drag air.

Same as above but a view looking up at the bottom of the cylinders.  The Inter-cylinder baffles are not installed in this picture.

Really hard to see but this is the gap between the cylinders near the injector holes.  There is about a 1/4" gap between the cylinders so I filled it with RTV after putting a barrier of glass/RTV on the surface of the head fins to prevent the RTV from filling the cooling channels.

Aft side of #5 cylinder. 

These are the engine mount covers that I fabricated to prevent any cooling air flow from exiting via the holes in the rear baffles where the engine mounts protrude.  I had originally ordered these from Aerosport but after about 6 weeks I had to cancel that order (poor guys are just swamped) and make my own.  They are not as pretty as the Aerosport version but they will do the trick nicely.