Baffles

Hours 102

Total Hours 1085

One of my biggest problems and what I have learned to deal with somewhat is multi-tasking. I have always liked to finish one thing before starting another but that cant be done with this airplane. I need to finish the baffles before I can finish wiring the engine. Cowl before the baffles. Spinner before the cowl, and so on. The engine wiring, baffles, and cowl all have to be completed together. This means I have parts scattered all over the hangar waiting for their turn to be installed. I have ordered certain length bolts and various hardware, and by the time they come in, I have a hard time remembering what they were for because I have moved on to the next part of the build! I hope to be clearing some of this up in the coming months. I have been reading a lot and planning my attack on the Baffles, so I began by cutting out the new spinner  for the prop which needs to be removed for easier access to the baffle work ahead.

Then I rigged up a pencil on a stick to check and make sure the spinner was even and not wobbling when spinning. I pulled the top plugs and hit the starter and watched the pencil marks. I drilled the holes thru the spinner and rear bulkhead after getting it good and straight.  Later I plan to mount this spinner without any screws showing. It is a modification I have read about on VAF.

I then unmounted the prop and began the baffles. I had been studying this operation for several weeks so I felt fairly confident. Since the Lycoming IO-360 is an air cooled engine, and the RV7 is a tight cowled design, forced cool air needs to be passing by the cooling fins of the engine while it is operating. Air enters the two holes in the cowl on either sides of the prop into the top area that is separated  from the bottom area inside the cowl by the baffles. This creates a high pressure side on top of the cylinders and a lower pressure side on the bottom of the cylinders. This causes forced cool air to pass in between the cylinders and thru the cylinder cooling fins and exits out the bottom cowl. This, hopefully, keeps the engine operating temperatures in the green. I fitted all the baffles and skipped the oil cooler install for now. Before I knew it I was needing to configure the "snorkle" for the airbox filter and horizontal induction into the left intake ramp.

This is the "snorkle" kit from Vans.

 I found that a 2" PVC collar would fit into the fuel servo after grinding the edges off slightly. Then I wrapped it with duct tape to center the snorkle when it is mated with the servo. 

 

 I need the fiberglass snorkle to come up from the servo to the left inlet ramp and then form a housing for the air filter. This takes a lot of thinking. Since there are so many different engine combinations for these planes, Vans has generic instructions and you have to figure out what is best for your situation. I put the bottom cowl on to trim the front of the air ramps.

I made a template from copy paper by holding it up against the servo and tapping it with a rubber hammer to create a out line for the holes needed in the snorkle.

 I then drilled the holes and cut the snorkle to shape.

Here is the snorkle fitted to the servo and ramp.

  

I cut out the ramp.

 Unfortunately, I realized the filter would be located farther to the outboard side of the engine than what I would like. I researched the matter and found out that the snorkle is designed to go on the IO-360 angle valve engine which is a little wider than my IO-360 parallel valve engine. The only way I can get the filter over where I want it is to cut part of the snorkle and shorten it then re glass it all back together. I decided to take the route several other builders before me did and just leave it where it is. It will not effect the performance at all, I just had it in my mind that when I looked through the inlet hole, I would see the whole filter sitting there right in the center. It bothers me but I will get over it.

This is my bending brake. I am forming a plate to go over the air filter to secure it in place.

Here is the plate installed over the filter. The bend is on the outboard side and it will screw into the #2 baffle. I dimpled all the holes and installed nut plates into the filter box built out of angle. The angle was then riveted to the fiberglass snorkle. It is built so you can remove the filter without removing the cowl but after installing the top cowl I realize you may have to be a contortionist to accomplish getting the screws out!

 I thought I would get by without doing any surgery on the snorkle but the alternator bracket was almost touching the snorkle so I cut out a portion of the snorkle to clear the bracket.

 

Unfortunately I found out what a dremel tool with a multi purpose cutting bit can do when it gets away from you! I spent 15 minutes of my precious time cleaning up DNA all over the workshop. At least I will not have to worry about this fingernail getting too long any time soon!

After I stopped the bleeding, I glassed over the hole with 4 layers of 8oz cloth. Then I sanded it smooth later.

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  I then installed the alternate air door as per Vans plans. I mixed up a batch of flox and blended the opening to the rest of the snorkle. The alternate air door is opened from a control cable in the cockpit in the case of ice or snow blocking the air filter.

I worked on modifying the point where the right air ramp mounts to the engine block. The plans called for taking the constant speed prop oil line loose and fitted thru a hole in the ramp. I cut a slot in the ramp so the fitting would not need to be taken loose every time the baffles are removed. A rubber grommet goes around the pipe at final assembly.

I worked on modifying the point where the right air ramp mounts to the engine block. The plans called for taking the constant speed prop oil line loose and fitted thru a hole in the ramp. I cut a slot in the ramp so the fitting would not need to be taken loose every time the baffles are removed. A rubber grommet goes around the pipe at final assembly.

I built the air dam gusset to go onto the right ramp and riveted it in with flush rivets.

Added angle supports

Filter housing installed.

I used two 2x4's to space out the cowl. I cut an aluminum spacer and drilled a hole allowing for the width of the boards plus 1/2" with a hole drilled in it. I inserted a fine point magic marker in the hole then reached inand marked the baffles all around. The goal is to have a 1/4" gap between the top of the baffles and the cowl. 

After confirming I had trimmed just enough to get the top cowl on, I did the paper clip trick I had read about. I put paper clips all around the baffles then lowered the cowl on. The top cowl pushed down the paper clips to the point where I could measure the gap I had. I then added what I needed for a total of 1/2" of gap.

I then went to work on the oil cooler installation. I mounted it as high as possible so the #4 cylinder would block less air to it.

I had to quit at this point and get ready to go back to work. I put in 85 hr building the baffles and still need to add the baffling to the top to seal them. Then I will probably paint them as it looks like I drug them behind my pickup for a hundred miles! I started my mornings at 3AM and worked till noon this month to avoid the July heat in the hangar. There was a 4 day lake trip included in the two weeks I was off but to be honest, I needed that break. I didn't get as much done as I would have liked but I got some pretty big boogers behind me. I will now work a week and then go to Oshkosh for my first trip to Air-venture! I hope to meet and talk to other RV builders there and meet some of the people (venders) I have been supporting these past two years. I also hope to make a decision on the paint that I will use after seeing all the home builts there. I'm EXCITED about that trip!

Cowl Work

Hours 56
Total Hours 983

Well, not much to tell on this post. I had a lot of farming to do on my days off and my nephew got married so not much time left for working on the plane. I did not take a lot of pictures this time as I was in a rush to get something done.

 First, I lined up the cowl to be even with the spinner using the aluminum angle pieces. Made sure the front openings for the air scoop was level. This takes a lot of "eyeballing"! It can drive a person crazy as there is no way to measure to make sure you are level.Then placed a light bulb inside the cowl and drilled the cowl for the hinge.

 

I installed the hinges on the upper cowl after sanding the edges as close as I could. I used the method described in the plans using epoxy flox mixture to glue the hinges down and riveted it up. Much to my dismay, the 1/16th gap in the lower part of this picture looks a little wide. Its a good thing I have learned how to "scarf" the fiberglass edges. You can see in the upper part of this photo where I added or "scarfed" about 1/4" on the end of the cowl edge. I also had to repair the holes left by the previous builder for skybolts. You can learn all you want about "scarfing" on VAF forums like I did. I also made the two upper hinge pins out of .125 stainless steel pins although the plans called for .90 pins. I chucked the pins in my drill and polished the pins down to about .90 on the last 8 inches where it takes a curve down. This allowed me to use the larger pins and prevent any slop in the upper area as other builders have reported with the .90 pins. I was worried about the pins being tight and hard to remove reaching thru the oil door but after working on them for some time, I had them sliding in surprisingly easy.

I fitted the lower cowl to the upper cowl and installed the vertical hinges. These hinge pins do not need to be polished down as the are not curved. I then "scarfed" about 1/2" of new fiberglass on the upper edge of the lower cowl where the upper and lower cowls meet horizontally. The previous builder had presumably planned on using skybolts so there was an unacceptable gap and all the holes for the skybolts had to be filled. I will need to sand a 1/16" gap between the cowl and forward fuselage to allow for paint but I'm going to do it very carefully as I am getting tired of scarfing new material on the cowl.

I installed the horizontal hinges and fashioned the pins. I polished them up with emery cloth and lubricated them and after some work, had them sliding in easily. I applied painters tape all the way around the cowl as a sanding guide for the 1/16" gap for paint. I then sanded the gap with a straight 1x3 board with 80 grit glued onto it. I then did the same for the upper cowl and where the cowls join. I have a lot of work to do on this cowl but I am very happy to find out anything can be fixed on fiberglass! There was a time early on when I thought I would have to buy a new cowl because of it being fitted and cut on by the previous builder..........Hopefully, on my next days off, I can attack the engine baffles installation and work a little more on the cowl.