Baffle Sealing

Time: 4 Hours

One last step that I needed to do on the baffles is to seal up any gaps in the baffles where they meet to engine. The idea is you need to imagine a molecule of air and you want the molecule to cool the engine. That molecule needs to travel past the cooling fins of the cylinders to me the most efficient. If there are other spaces that the molecule can go then that reduces the effectiveness of the cooling properties. So to force as many of those molecules around the fins you need to close any other escape paths for them. One area that had a very large gap was on the right side of the forward baffle. I think it would have been tough to fill it with just RTV so I made a filler strip out of .025″ sheet. Once I had it to the shape I needed I drilled, deburred, primed and painted it to match. Most of the areas that need seal are pretty obvious to see for the not-so-obvious areas I used a light shining up from the underside of the engine to identify them. I used a grey colored RTV sealant, think caulking for environments that get hot and have contact with oils/fuels. It seals well and creates a good bond however can be removed when needed. It’s messy and hard to get it to look good but it is needed to properly cool the engine. I bought a couple large tubes that fit in a caulking gun to make it easier to apply. A couple areas that were too hard to access with the nozzle on the tube so I used a piece of 1/4″ plastic hose that was extra brake line stock attached to the nozzle to help get to those. I was able to use a wet finger to smooth some of the areas but others it was just too tight to get a finger on the seal. They aren’t beautiful but the will accomplish the task. I’m glad I was able to find a color that didn’t stick out like the red RTV that most planes use and would really be an eyesore.

I have a few areas that I want to clean up a little once they cure all the way. In the mean time I went ahead and cleaned all the baffle seals for the top of the baffles and installed them.

Overall I’m happy with how the baffles turned out. I think they will provide good cooling but will have to wait until I’m flying to confirm that.

Throttle Quadrant Support Bracket Redo

Time: 4 Hours

Since my arm rests and throttle quadrant are all custom, meaning I deviated from what Van’s calls for, I had to do some engineering that’s unique for the support of the throttle quadrant cables. I took the idea from my buddy Glenn and made a bracket out of some large aluminum angle. I had completed this task and installed it some time ago and moved on to other tasks. Since then I was really happy with how the arms of the quadrant were moving and it felt like there was some binding. So yesterday I decided to investigate and see if I could fix the problem. What I found after a closer look was that I had actually measured the distance from the side skin to where the holes for the cables needed to be by about 3/8″. This meant that as the cables left the quadrant they angled outboard to hit the bracket holes. This caused each cable to cause a torquing action on the levers and caused the mixture and propeller cable ends to actually touch as they went through there motions in one spot. That was not good and needed to be fixed. So I decided to make a new bracket that would extend 3/8″ farther inboard. So I went about removing each cable from the quadrant then removed the two bolts holding the bracket. This allowed me to slide the bracket off of the three cables and remove it. I used it as a template and just extended the arm length by 3/8″. With the new measurements I went about drilling and trimming the angle to create a new bracket. I then did the task of getting the bend of the arm where the two bolts attach the bracket to the angle on the side skin. This was the time consuming part as it’s a little bit of a task to get the cables in and situated while checking the angle. Once that was done I bolted the bracket down and went through the process of setting the correct throw of the cable ends. These all looked good so I removed the bracket and primed/painted it so it would look presentable. Today the paint was dry so I reinstalled the bracket and worked the cables from outside to inside. First was the throttle cable as it’s the outermost cable on the quadrant. Once I had the throw all set and got the throttle arm on the servo to hit the full and idle stops I locked the cable arm in place with the nut and attached it to the throttle lever with the pin and cotter pin. I repeated this process for both the propellor and mixture cable. The propellor arm has given me the most problems part due to the angle that it goes through the bracket and the arm length on the propellor governor. What I ended up with was the prop lever goes to the full forward position on the quadrant and is short of the full aft portion by 3/8″ or so. I’m ok with this as it will never be in that full aft position and only off the full forward position a little as you increase the propellor pitch and reduce the engine RPM. The mixture arm works perfect allowing the full rich and idle cut-off.All three cables operate much smoother and there is no binding at all. I’m happy about that but I’m happy I spent four hours repeat a process but that part of experimental building. One other thing I did was to give the RV-8 some fresh air so I could sweep out the hangar. She really looks good stretching her legs after a long winter being cooped up!

Fuel Pump Overflow

Time: 1 Hour

The engine driven fuel pump has an overflow port to allow excess fuel drain after engine shutdown. Van’s uses a 90° elbow that has a soldered 1/4″ copper line on it. When I was installing it the copper line broke off. So I decided to upgrade to a AN842-4D elbow. This has the 1/8″ threaded side and a 1/4″ OD barbed side. I could then use some 1/4″ ID hose to run from the AN fitting to some 1/4″ aluminum tube that directs the fuel overboard under the fuselage. I cut some tubing and made the required bends so that it exits underneath the fuselage through a hole I drilled. I then secured that tubing with adel clamps. With the AN fitting secured in the pump all I needed to do was cut a length of tubing to connect the two. I will use zip ties to secure the hose to the tubing and AN fitting.

Alternator Blast Tube

Time: 2 Hours

Not required by PlanePower but it doesn’t hurt to have cool air blowing on the cooling fins located on the aft portion of the alternator. I had drilled the hole on the right hand inlet baffle ramp a long time ago so I would have to drill through the painted product. Now I just needed to figure out how to get the tube situated to blow air on the right spot. What I decided on was to fabricate a bracket that would allow it to be riveted to the alternator aft cover and hold the tube in the right position. So I took some measurements and cut out a blank from .040 sheet aluminum and formed up the bracket. I drilled a 3/4″ hole for the tube and match drilled four holes for blind rivets. Once I had the shape and all the bends looked ok I cleaned it up and primed/painted it to match the baffles. Once it was dry I riveted it in place and installed the tube. I drilled two holes in the end of the tube that allows a small zip tie to be installed at the top and bottom of the tube and secure it to the bracket so it doesn’t come loose. I then installed the aft cover now with the bracket and measured for the opposite end and made the cut. There is a third zip tie securing the tube to the alternator as it comes forward and keeps it away from the exhaust pipe. I also drilled two small holes on the bottom at the lowest spot of the tube so that any moisture that were to get in the tube would drain out and not be directed at the alternator. It’s simple and secure, I think this will do a good job of cooling and was an easy project.

Sniffle Valve

Time: 1 Hour

At the bottom of the engine is the Superior cold air sump. This is where the air that comes in from the air filter/servo gets divided up and sent to the individual cylinders. During engine shutdown there can be a very slight chance that unburnt fuel travels back down into the sump. AeroSport power said this is very rare in a fuel injected engine but still recommended the sniffle valve. The valve is a mechanical means to drain any fuel out of the bottom of the sump. The valve is heat activated, or the lack there of as heat actually closes the valve and when it cools it opens allowing any fuel to drain. I was pretty straight forward installing the valve and I just needed to extend the line so that it would exit past the lower engine cowl onto the ground. I used some MIL-6000 hose to give it the bend and flexibility and secured the other end with a clamp to the engine exhaust bracket. I’ll replace the clamp with a high temp one after I get it from Aircraft Spruce. I think I will also put some eat shields on the exhaust where it’s close to the hose.