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.

Fresh Air

Time: 0 Hours

I did pull the RV out of the hangar to clean and sweep the floor from all the winter dust. While it was out I snapped a few photos for you to enjoy…yes those are shoes under the left wing! My son and new private pilot, Chandler, is sitting in the RV making engine noises.

Trim Tab Hinge Pin

Time: 1 Hour

The last month or so has been slow in the hangar as I have been working a lot at United as well as working projects on the new house. I have been keeping a “punch” list of tasks that needs to be done for projects over the last couple of years. These items didn’t need to be done at that time and it was better for them to remain undone to make the remaining projects easier. One of those items was the trim tab hinge pin. I had originally put a temporary pin in that was shorter and without any bends in it to make it easy to remove the tab as I built the tail. Today I moved on to bend and create a permanent pin and a way to secure it. Van’s would have you just put a bend and safety wire it to a small hole in the small spare of the elevator. I wanted to do something a little nicer. I wanted to use a piece of hinge with its eyelet and create a tab to put a screw through. I made some measurements and came up with a plan. I would drill out the two rivers on that spare and put a #8 nutplate there utilizing the bottom river hole. I would drill another rivet hole for the second rivet in the nutplate and enlarge the top original rivet hole for the screw. I made some test bends in a scrap pin and came up with the perfect setup. I then reproduced the shape on a new pin. I then shaped a piece of hinge so that it had one eyelet and drilled a #19 hole in it for the screw. I dimpled the bottom hole in the nutplate and countersunk the spar for the top rivet. I did it this way since the single sided nutplate is pretty tight to try to dimple both holes. Once I had both rivet holes finished and the hole for the screw done and cleaned up I riveted the nutplate in place. I then cleaned up the shape of the hinge tab and bent the tip of the pin so that the tab could not fall off. I put the parts back together and slid the pin in place securing it with a #8 screw. Turned out really nice and clean. It’s little details like this that make the build fun, most people will never see this but it makes me happy knowing I spent the extra time to make it clean and functional.

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!

Engine Cowl Work

Time: 20 Hours

So over the last month I have been slowly working on the engine cowl surface’s starting with the insides first. I had already started the inside prep earlier so it was a good place to continue. The process was to sand the surface smooth but not break through the epoxy. Once it was smooth and all the ridges knocked down I applied a layer of epoxy on the entire surface using old hotel key card to squeegee the epoxy into the holes. This allows you to remove any excess epoxy which makes future sanding much easier. I would then let the epoxy cure overnight so I could repeat this process. I did this a total of four times on the inside surface for both the top and bottom halves. It’s time consuming since you have to let the epoxy cure and then the sanding, I have learned to hate sanding! I filled in some of the larger imperfections on the inner surface but not getting too crazy as it’s just the inside. The idea for me is to get the inner surface acceptable to paint to keep oil, grease and any other contaminant to be easily identifiable and cleanable. Also most of the inner surface will eventually be covered with an aluminum foil type material that radiates heat from the exhaust system and protects the fiberglass. There are various brands of this heat shield and I have not decided on which one yet. Once the insides were good enough I moved on to the exterior surfaces. The process is the same and just as the inside except I added an additional step. This was to use UV Smooth Prime to fill in all the tiny pin holes. This primer is like paint with drywall mud mixed in. You really have to mix it well. It’s so thick I decided to buy a paint can shaker from Harbor Freight Tools to handle this. As of today they cowl halves are 90% done and I’m just finishing up some small imperfections that are left. Here are a few pics of the process but not much to show while sanding.