Sam James Cowl and Plenum Installation

Introduction

Matthew — Wed, 08 Nov 2006 20:45:00 +0000

I'm going to detail the installation of the SJ cowl and plenum in my RV-9A. This is my first cowl installation and I have limited fiberglass experience. I'm doing this because I haven't found anyone else that has and the instructions are text only and cause head scratching every now and then

A builders support group on Yahoo is located at http://groups.yahoo.com/group/JamesAircraft/?yguid=168192882. I'd recommend joining if you haven't already. Liz keeps the most current set of instructions posted in the group files section.

I welcome comments, criticisms, and corrections!

Newest updates will be at the bottom of page.

Additional hardware required

Matthew — Tue, 08 Nov 2005 20:59:00 +0000

Here are the items not included with the kit that you will need to procure yourself.

MS20257-5 hinge material - Aircraft Spruce #MS20257P5 (2 - 3ft pieces)
MS20257-4 hinge material - Aircraft Spruce #MS20257P4 (3 - 3ft pieces)
Epoxy/Resin and associated supplies (West Systems)
Proseal
K&N Air filter #E0995
Various aluminum sheet pieces to construct alternate air system.
Mild steel sheet. (I used leftover from Van's kit)
Cable End B-Nut from ACS. (Attaches to door arm)
3" SCAT tubing
3" Silicone 'Turbo' tube
RTV
#8 screws and nutplates
3" hose clamps (3)
6" hose clamps (4)
Some sort of hinge and latch for oil door

Prep work

Matthew — Tue, 08 Nov 2005 20:16:00 +0000

Before you start on the cowl, there are a few things (obvious?) that need to be done.

The engine must be hung and torqued up. Any changes to mounting may cause cowl to not line up with prop spinner.

The flywheel, prop exentsion and rear spinner bulkhead must be installed. The rear spinner bulkhead acts as a positiong reference. The prop should probably be on, as the weight of the prop will cause the engine to sag a bit more than with it off. You will want the engine generally in the final position so you can get the appropriate gap between cowl and spinner.

Step 1: Preparing and fitting the top cowl

Matthew — Tue, 08 Nov 2005 19:28:00 +0000

The top half of the cowl gets fitted first. The first thing to do is hot-glue a couple of 3/16" spacers to the front of the cowl. These will position the cowl the appropriate distance back from the spinner. (SJ instructions say 1/4". 3/16" puts you closer but also gives you some wiggle room when fitting.)

Next you need draw a line on the forward top skin of the fuse. The line should be 3" back from the front edge. This line is a reference and will aid you in marking the trim line on the cowl. (SJ instructions have you making a little tool to do this.)

You will need some way to support the front of the cowl to hold it at the correct height. SJ instructions indicate to glue a couple strips of aluminum to top of cowl. I just used a small block of wood taped to the top of the prop extension that the cowl rested on. Either method works.

Position the cowl over the engine. Adjust the cowl at the front to get the approprirate fore/aft position using the spacers glued to face of cowl. Also position it left/right so it is centered with the spinner bulkhead. Finally position it vertically. If you have the bare spinner back plate, keep in mind that thickness of the actual spinner.

With the cowl now positioned, use the reference line to measure forward 3" and make a mark on the cowl. Do this every 3 to 4 inches. When done, connect the lines. This line will serve as your trim line. (Alternately, you can put a bright light under the cowl which will easily illuminate the edge of the skin.) Be careful when making the lines to not shift the cowl. You should either clamp it along the sides or drill a couple holes through the cowl and use cleco's to hold it in place.

(My time: 1.5 hours)

Remove the top cowl from the fuse and using a cut-off wheel, cut the excess off the aft edge of the cowl. Say 1/16"-1/8" from the line. After cutting the excess, use a long straight sanding block to sand up to the line.

You'll need to install the hinge material along the top edge of the firewall to support the cowl. You can do this permanently if your top skin is already riveted on or temporarily with cleco's. If you're installing permenantly, use some Proseal or some sort of fire retardent goop between the skin and firewall flange to prevent any nasties from entering the cockpit. You may need to include a shim between the hinge and the firewall to get the thickness to match that of the cowl.

Using Van's plans, a short piece of hinge goes on the right side of the upper firewall, then a 3 1/8" space, then a longer piece running the rest of the way across the top and down the left side. The gap allows you to put in/pull out the hinge pins. The gap is on the right side near the oil door for easier access. The hinge material along the top is the 20257-4. (You might also want to cleco a couple of short pieces of aluminum along the vertical sides of the firewall near the top to help hold the sides of the top cowl out.)

Update: The Van's design for the hinge setup makes it a bit of a challenge to get the hinge pins in and out. A new builder trick is to put two pieces of hinge along the firewall with a small 2-3" gap in the top center. A small cutout in the cowl and a plastic block mounted to capture the hinge pins makes it MUCH easier to insert the pins from the outside of the cowl instead of through the oil door. If I can find a picture, I'll post one but seriously consider this option.

With the hinge in place, position the cowl back on the fuse. Continue to make adjustments to the fit by sanding the aft edge until you get a uniform edge. Remember to leave _at least_ a 1/32" space between cowl and skin for a paint gap, otherwise your cowl will rub and crack the paint.

(My time: 2.5 hours)

Step 2: Preparing and fitting the bottom cowl

Matthew — Tue, 08 Nov 2005 12:11:00 +0000

Mark a centerline on lower cowl for the notch you will cut for the nose gear. Measure out a 1 3/8" wide notch and about 12" deep and remove the material.

With the notch cut out in the lower cowl you can now slide the lower cowl in place and begin fitting the bottom to the top. You will need to improvise ways of holding the cowl up from beneath. Fitting the lower cowl to the top is a LONG process. Be patient and take your time. Stop every now and then to make sure you haven't forgot anything.

On my cowl, the lower half of the cowl around the spinner area and air inlet holes, I needed to trim about 1/4" off. You want to make sure the inlet holes are concentric and of the right size as well as having a 13" diameter area where the prop spinner goes. I almost didn't notice this until I had the bottom cowl in position the first time and saw that there was a good portion of the cowl below the spinner.

With the front edges trimmed to produce the right diameter holes and a straight fit, I positioned the cowl and marked trim lines along the aft edge where it hits the firewall. Use the same method as the top cowl, drawing a line back from the firewall 2" or so and then measuring forward from that line. Do the same for the bottom edge. Remove cowl and trim.

While the cowl is off for the first trim, go ahead and install the vertical hinges along the firewall. This will help hold the cowl in place when fitting.

Reposition cowl and check for fit. I used cutoff wheel to take bulk of material off initailly, staying back from my line about 1/16" and then sanding down towards the line using some 40 grit paper. Note adjustments on cowl, remove, sand, repeat. I probably removed and sanded 15-20 times working on a good fit. When sanding the aft edges, watch the front area of the cowl to make sure everything lines up well. I used clamps on the front in alignment.

When you get close to getting a good edge along the aft edges it is time to trim the sides where the top/bottom meet. Use some duct tape to hold the top/bottom together. Instead of using the measure method, I reached inside the inlet hole with my arm and marked a trim line with a fine tip marker using the edge of the top cowl as the reference. Towards the aft end, I did have to measure since my arm isn't long enough to reach all the way back.

Remove cowl, trim, sand, reposition. Here is another spot where you'll take the cowl off a dozen times make small corrections, sanding high spots, getting a good split line.

When you've finished sanding and have the sides lined up, the aft edges fit well, it is time to drill the vertical and bottom hinges to the cowl. The bottom you can do yourself by laying on the floor and with one hand reaching in the outlet area to hold down the hinge and drill with the other. For the sides you really need a partner. One to reach in the outlet and hold the hinge while the other drills/cleco's 3 or 4 holes.

(My time to fit the bottom cowl was about 10 hours or better over two days. I went slow and took lots of breaks, stepped away for awhile. You could probably do it faster.)

Step 3: Attaching the hinges

Matthew — Tue, 08 Nov 2005 10:53:00 +0000

With the cowl trimmed/sanded to fit it is time to attach the hinges to the cowl. Countersink the holes in the cowl. Rough sand the rivet line on the inside of the cowl and also rough sand the side of the hinge that will face the cowl. This will give the epoxy/proseal something to adhere to.

Rivet all the hinge pieces to the cowl. When using epoxy/proseal, do your best to prevent it from oozing out on the eyelet side of the hinge. Any excess will only get in the way and have to be ground/cut away.

Now would also be a good time to cut-out the oil access door. You can't install the hinge pins without an access door (unless you did as mentioned earlier). The door you cut out will become the actual door, so do your best to cut straight. I used a hack-saw blade and a coping saw blade.

Update: The door I cutout was not satisfactory. I created a new oil door by laying up 5 layers of fiberglass on the inside of the top cowl over the oil door cutout and then trimmed to size. It came out REALLY nice. Don't kill yourself trying to make nice cuts, just cut out the hole and make a new door.

Clamp and drill the -5 hinge to the side of the top cowl (or bottom). Position the hinge 1/4" above/below the split line. This will mask the eyelets. Countersink and debur. Epoxy/rivet hinge to cowl.

Install the cowl on the airframe, top and bottom. Clamp/tape as necessay and drill the lower cowl to the other half of the hinge.

All of the hinges should now be installed. For the side hinges, drill a small hole in the firewall for the hinge pin to pass through. Create some sort of mechanism to hold the hinge in place when inserted. SJ recommends installing some brake line to help guide the hinge but it isn't necessary, you can just lean over the side and look up under the panel to put it in.

Lower cowl support

Now would also be a good time to install the lower cowl support per Van's plans. SJ instructions don't call for this but seems like a wise idea to install.

Step 4: Lower Inlet Ring and layups

Matthew — Tue, 08 Nov 2005 09:26:00 +0000

I mixed up a batch of epxoy/balloons and put the small inlet ring in place. I suspended the cowl up a bit off the floor so the ring wasn't resting on the floor. I poured in the mixture and let it cure. Put enough in to fill in the groove but not so much as to not leave enough ring to attach too.

I pinned the top and bottom cowl halves together and started doing layups where the top and bottom meet at the front. I used some clear masking tape on the top half to keep it from sticking. I also used some aluminum strips and cleco's to hold the top/bottom half together to keep it from shifting.

It was a challenge doing the layups way down inside!

Now trim those layups to give some nice smooth edges. With the cowl pinned together and clamped in position, drill two holes on each side to #8 CS screws. Install nutplates on back sides of new layups. Countsink the holes on the top cowl to accept a countersunk washer.

Step 5: Air inlet

Matthew — Mon, 07 Nov 2005 14:34:00 +0000

Before you start this step you need to make sure that you have the right carb inlet box. SJ makes two versions of this box depending upon the height of your carb. The one that comes with the kit assumes you have a newer carb that is tall. Some carbs (like my MA4-5) are shorter. The nozzle on the carb inlet box is angled differently. Confer with Will/Liz on whether you have the right version.

A small fiberglass box is mounted to the bottom of the carb to act as an air box. To the front of that box is a conical shaped box that contains the air filter and alternate air door.

Sand the edges of the mating surfaces of the inlet air box smooth. (Don't sand off the buttons and matching dimples!) Install nutplates around the perimeter of the upper portion. These will hold the two halves together.

Next you will need to mount the upper half to the carb. Prior to mounting the carb on the engine you might go to the trouble of creating a template of the carb itself getting the holes layed out. The carb is not centered on the bottom of the engine, so the air inlet box gets offset to the right of the carb. Important: Position the carb inlet box as far AFT as possible. This will help fitting the filtered airbox later. (The photo's below do not show accurate AFT positioning.)

I'm sure all carbs are a bit different from each other. The upper half has a small depression on the aft edge to clear the carb drain boss. My carb (MA4-5?) also had another protusion on the bottom. I made cutouts for these protusions in the box and drilled the holes using the template I made prior to mounting. I'll cover up the holes with some fiberglass layups.

January 6, 2006

The carb inlet box I was given wouldn't work for my setup. The stock box is designed for taller carbs. Mine is a short carb. Will made up a new box that has less of an angle on it. The newer box solved my fit problems.

2.5 hours installing new carb box.

Step 6. Filtered air box

Matthew — Mon, 07 Nov 2005 13:43:00 +0000

The filtered air box holds the E0995 K&N cone shaped air filter and attaches to the airbox on the carb via a duct and attaches to the cowl on the front side.

First step is to attach the alternate air bracket to the box. This bracket holds the flapper that allows you to run warm air to the carb, closing off the fresh air. The bracket is positioned about 1" back from the front. (Do not position it too far aft. I have a report from a builder who had to trim a notch in his door to clear the air filter.) File and trim as necessary to get a decent fit. Make sure that it doesn't flex when you put it on. The top surface needs to remain flat.

Once you get a good fit, mark an outline around the bracket on both the outside and inside. Then measure 1/8" from the INBOARD line and cut out a hole using that line.

Cut a piece of hinge material and tape it in place on the bracket. Make a paper cut-out for the flapper and tape to hinge. Make adustments necessary for flapper to fit nicely and so that it swings freely.

Obtain the E0995 K&N air filter ($45 from Advanced Auto). Place the filter in the housing and put the end cap on. Clamp in place. Mark 6 to 7 holes around the perimeter, drill to #12. Install nutplates.

Alternate air door

Bond the fiberglass door frame to the inlet cone. Fill all the gaps on the inside with epoxy/flox.

I'll let pictures tell the rest of the story:

I'll point out that I did the flapper door a little different than the instructions. Mostly because I couldn't find the drawings that came with the instructions and I did it on my own.

Will has you mounting the flapper on the other side of the hinge. You then have to make a 'spacer' the same shape as the door to take up the gap between the flapper and the deck so it sits flush. I put my flapper on the other side and then sanded down the area where the hinge mounts to the deck and put a spacer on top of the hinge to take up the space between it and the deck. I think I like this a litte better. The spacer is smaller/easier to make.

Connecting the FAB to the CIB:

The filtered airbox connects to the carb inlet box via a piece of 3" tubing. I used a 3" piece of silicone tube. It took me awhile to find this stuff but I finally figured out it is used on turbo-charger systems for cars, so a google search for 3" silicone turbo hose should net you something. Use 3" clamps to hold it in place.

The front inlet is also held in place but a piece of 3" tubing. I discovered that once the airbox is in place, the lower cowl is difficult to get on and off. Use a piece of 3" flexible scat tubing clamped to the aluminum inlet ring. Leave the aft clamp loose until you get the lower cowl in place and then you have just enough room to get it tight.

It is also advisable to support the filtered airbox from the top in some manner. Refer to the photo's section in the Yahoo group for an option.

Warm air inlet

Install Van's warm air inlet tube onto the exhaust and connect it to the inlet on the FAB. (NOTE: Make sure you have the 2" version of the inlet on the FAB. They were shipping a 2.25" version which made it difficult to connect to the tube on the exhaust.)

Install the cable to operate the door on the FAB using the B-nut. It takes a lot of stroke to take the door from open to closed, almost using the limits of the carb heat cable. Some design changes could be made to improve this, just not sure what.

Step 7: Baffles & Plenum

Matthew — Sun, 06 Nov 2005 15:23:00 +0000

Sam provides drawings with his plenum for the aluminum baffles that go along the sides of the engine. I opted to use Van's baffling kit. It was an extra $200 but a big time saver I think. Sam's drawings don't appear to be exact and even have some errors on them. The baffles are essentially the same but Van's comes pre-formed. The following assumes you have Van's baffles and aren't making your own.

First step is to fit the side and rear baffles to the engine per Van's instructions. Do not trim the top edges at this point! Just get the baffles installed along the sides and back. (On the back baffles, you do not need to install the support bracket at the top center.) The tops of the baffles will have to be trimmed, so just cleco the baffles together until after they are trimmed, then rivet as necessary. (Do not install the scat connections yet)

With the sides and back baffles installed, you can start playing with the plenum itself. Sand around the outside edges of the plenum to remove any excess flash material where it will rest against the aluminum baffles. Make sure your plug wires are in place.

Place the plenum in place. I think the object here is to get the plenum as low and close as possible to the engine without interfering with the spark plugs. I think there are some comments in the instructions about removing the ferrel on the spark plug wires to help clear. This doesn't sound like a good idea to me. There is plenty of room to leave the plenum sit high enough to provide adequate clearance for the plugs/wires.

I spent a good 3 hours trimming the plenum along the front edge where it goes around the engine case. My D2J has some large pads on it that required some major surgery on the front left side to get to fit.

Once the plenum has been trimmed as necessary, put it in place and get it level. You should put the lower cowl in place so you can line up the inlet holes with the cowl cutouts. Once you have the plenum positioned, use a marker to draw around the plenum on the inside of the aluminum baffles.

Remove the plenum and baffles. Trim baffles on the line you marked. I recommend leaving the baffles stick up just a bit above the plenum to give plenty of edge clearance for the holes you drill for the screws. (DO NOT USE the template provided to trim the baffles, it will not leave you enough material to work with.)

Position the baffles back in place on the engine.

Locate and mark the location for the 2" scat tube connection on the back right baffle for the cabin heat muff. Make sure it doesn't interfere with your oil dipstick.

Decide whether you want to mount the oil cooler on the back baffle or on the firewall. The firewall option might be better and easier, however, rumor has it that it doesn't perform as well on the firewall. Jury is still out on this as I haven't flown with the setup yet. (I chose firewall) Once you make your choice, install either the 3" scat connection or mount the oil cooler on the back baffle.

Place the plenum back in position. Drill holes for #8 screws/nutplates around the perimeter. I put 4 on each side and 6 along the back edge.

Remove baffles/plenum, install nutplates and scat connections.

Next is the front inlet ramps. I also spent a lot of time trying to figure out the front inlet ramps and how they tie to the plenum. The pictures in the instructions aren't quite detailed enough to show how the baffles/plenum tie together on the front.

Make up and install the inlet ramps along the front of the cylinders per Van's instructions. You will have to rebend/reshape/trim the inlet ramps themselves to match the plenum. I also trimmed some of the lower angled portion of the plenum. This area is challenging.

I have uploaded some photo's to the image gallery here.

Step 8: Upper inlet rings and tubing

Matthew — Sat, 05 Nov 2005 17:49:00 +0000

(You could do the upper rings at the same time you do the lower rings and layups)

With the cowl pinned/screwed together, enlarge the cooling inlet holes just enough for the aluminum inlet rings to fit. Sand and clean the areas on the inside of the cowl where your mixture is going to go to trap the rings.

Put several coats of wax/mold release on the aluminum rings. Use some molding clay to fill the 'notch' in the aluminum ring in the area where the top/bottom cowl split lines are. You don't want any epoxy in this area.

Position the cowl on it's nose and position the rings in place making sure they are flush with the front surface. Use more modeling clay to block off any areas that you don't want epoxy flowing to. The idea here is create a couple of rings of epoxy to capture the aluminum rings.

Create a mixer of epoxy/micro/flox. Leave it thin enough that it will flow into the groove of the ring. Even having it flow out the bottom around the ring is good since it will fill any gaps and can just be sanded down later. Pour just enough mixture to fill the groove and come up to the edge. You don't want to put too much covering the area where the inlet hose connects to the ring. Let it cure for a good 24 hours.

Split the cowl halves and cleanup as necessary! (We are almost done!)

Screw the plenum in position and install the lower cowl. Cut the wetsuit material provided with the kit in half so you have two equal pieces. Wrap each pieces around the ring and the plenum and mark a line for trimming. It will need to be trimmed on both edges. For the lengthwise cut, make it as clean a trim as possible.

Remove. Spread a table with newspapers and pull out the glue provided. Massage the tube a little but not so much that you split it open! Following the instructions on the tube, spread the glue on each edge of the material and let it dry for 5 minutes, then do a second coat and let it dry for 10 minutes. Then butt the edges of the material together carefully. The glue is sticky and you get once chance at this. Let the glue setup overnight.

Now you can take your 6" hose clamps and clamp the 'tube' to the plenum and aluminum ring!

Step 9: Oil door

Matthew — Fri, 04 Nov 2005 18:22:00 +0000

If you haven't already, you'll need to install the oil door. If you did a perfect job of cutting out the door, you can use it as your door. Likely though that you'll want to make a new one as I did.

I taped over the oil door cutout on the inside of the top cowl and then put a piece of plastic over a large area. I layed up 5-6 layers of 8oz cloth over the area where the door goes. When cured, I removed the plastic/tape and drew the outline of the hole on the new layup and trimmed.

I installed an aluminum ring around the opening extending 1/2" inside the hole about about 3/4" outside and riveted in place. I installed two hidden hinges. (Like Dan's setup)

I picked up a latch from B&B that only has a round button showing through the oil door itself, so it is well hidden.

I'm real happy with how the oil door came out. It is perfectly flush, the hinges are hidden and the latch only shows a round button that is flush as well.