Baffle trimming and intake ramp finishing

In order to get the top cowling back on, the baffle needed to be trimmed. I saw two ways to do this, and I ended up sort of using both. I started by elevating the top cowl 6″ above the lower cowl. Care was taken to make sure it was aligned both fore, aft, left, and right to the bottom cowl. I just used some pieces of scrap wood and clamps that I had lying around on each corner on the outside of the cowl. I measured in multiple locations along the horizontal split to be sure I was satisfied before moving on.

Cowl elevated 6″
More of a front view.

I then made a tool out of a tongue depressor and an aluminum block I had. I taped a sharpie to the bottom of the block and adjusted the stick to get exactly 6″ from pen to top of the stick. I didn’t take any pictures, but the idea here is that you have enough room (with the 6″ elevation) to get your hands/arms inside to hold the stick at a 90 degree angle with the sharpie along the inside of the baffle. Holding the stick on the inside of the upper cowl, you move it aft tracing the contour of the top cowl onto the baffle which will serve as a trim line.

I then trimmed to that line. That basically got me to flush. One could certainly add some extra to the length of the stick to get the the gap you’d like to achieve. Instead, once the initial trim was done, I utilized the 2nd method of paper clips all along the baffles. You barely stick them on and then place the top cowl into position. They slide downward and give you an exact indication of how much gap you have at that location to the top cowl.

Paperclips in position to measure gap

Below you can see the results of the first attempt. You’re shooting for somewhere between 12/32″ and 16/32″ gap per the plans. At each paperclip location, I wrote the number of 32’nds needed to get to 12/32″ by measuring how high each paperclip was above the edge of the baffle.

Measuring current gap

Those measurements basically were used to draw a new trim line.

Marking a more precise trim line.

I ended up doing this for a couple of cycles until I was completely satisfied with the gap all the way around. Making smaller adjustments in specific areas as I went. Below isn’t the best picture, but it was the results of the baffle trimming with a gap to the top cowl.

I fabricated the clips and drilled them into position per the plans. I’m holding off riveting most of this stuff until later.

Now that the baffles were trimmed, I decided it was time to affix the top cowl inlet ramps. I placed them into position with clecos and some scrap metal strip to hold them in place at the front.

I then test fit the cowl and had to trim the outer side baffles more to account for the curvature. I did get somewhat lucky due to my cowl being so far forward based on my prop/spinner setup compared to most. The ramps didn’t require trimming at the prop governor to at least test fit. I did end up trimming around to give some more clearance, which I’ll foam in later to provide a good backing for baffle material.

No initial trimming required for prop governor.

Once I was happy with their location, I epoxied them into place. Later I will layup some cloth, but for now just epoxy to hold them in position. I also did a single layer of cloth and some peel ply on the inlet circle just to hold that area into position.

Epoxy ramps into place.
1 temp layer of tape with peel ply on the outside.

I then laid up 3-4 layers of cloth for the underside of the circular inlet.. Placed that into position and let it cure. I sanded down the outside area and added micro. Once that was cured, I sanded to a smooth finish.

Right inlet ramp micro’ed
Same on left side.
Cutout for prop governor

With the upper ramps completed enough for now, I moved on to customizing the center baffles. I started with the right side, seeing it’s the easier side without compressor interference to deal with. I cut the stock baffle leaving just enough flange to rivet a new piece that would angle toward the inboard side of the inlet. I first made a template from construction paper and got it as close as I could. I transferred to metal and worked on trimming to get a good gap to the upper inlet ramps.

Paper template of right side.
Transfer template to metal and test fit.

I then spent some iterations trimming this custom piece to match the curvature of the upper inlet ramp with some gap for baffle material. Below are the results.

Right center baffle gap.

To hold the inboard side in place I fabricated up some 3/4″ x 0.125″ Angle. Seeing there was a slight bend in the baffle I just created near the inlet, I marked a cut to match that bend in the angle. I marked and cut out a “V”

Marking the cut to bend the angle
Cut made.
Bending the angle to match the bend in the baffle.

Below is the end result after match drilling and cleco’ing the baffle to the angle.

I utilized 3 screws to tie the aft piece of metal holding the carbon fiber ramp to the front pieces, including the piece of metal that runs under the carbon fiber ramp. I trimmed the excess away on the inboard side of any carbon fiber and metal plate so it didn’t protrude past the angle.

I then did a similar thing using a template on the left side. I decided to use one piece of metal to wrap around the governor and bend around the AC compressor belt to box it out of the inlet area.

Beginnings of a paper template

Once I was satisfied with the paper template, I transferred it onto metal, cut it out, and made the needed bends as shown below.

Initial trim of the custom left baffle.
A front view.

I then worked to fabricate another short piece of angle with a notch cut out for AC belt clearance to hold the inboard side in place. I drilled 2 holes for #6 screws to attach to the stock baffle that I had cut off and left a bit of a flange for connecting my custom piece to.

View of left ramp area with baffles screwed together and cleco’ed to the angle
Front view showing the angle and 2 #8 screws holding it in position, allowing clearance for the AC belt.
View of the finished up left ramp area.
Both ramp areas complete (beside riveting everything).
Final picture with top cowling in place.

This was a lot of work!

Air Conditioning Scoop

During various periods of downtime waiting for epoxy to cure or waiting on parts to come in.. I continued some work on the Air Conditioning Scoop that houses the Condenser on the belly. The first step was to mark the center line front and back as well as a line around the perimeter for the screw holes to line up to.

I then placed a string between the center point at the firewall and the center point at the tail to line up the centerlines marked on the scoop. A single hole was drilled for a cleco to hold the scoop in place fore and aft.

Side view

I then drilled approx 32 holes around the perimeter per the instructions making sure to not drill into any underlying structure. The corners are where you have to be really careful as they approach the rivet lines for the ribs.

As most of these holes are blind and there is no access from the inside, I had to install rivnuts to accept #8 screws. I practiced on some scrap that I had prior to doing it for real so I could get a feel for the tool and how rivnuts work in general.

Below you can see the rivnut squeezed down and onto the metal on the inside holding it in place.

I enlarged all of the #40 holes that were drilled to the proper size (#2) for the rivnut installation. The holes on the scoop were countersunk to accept #8 flat head screws with a tinnerman washer.

Below is a picture of me using the tool to set the rivnuts into their holes with a small amount of red loctite on the barrel of the rivnut.

Each rivnut has a “key” feature on the inner face of it to help prevent it from ever rotating. A notch had to be added to each hole to accommodate this feature of the rivnut. An example is shown below. I used a flat file to do this..

Seeing I had previously removed the seat pans and baggage area floors on the right side, I oped to use nut plates instead of rivnuts in this area. Also any holes in the tunnel utilized nut plates as well. Given access, using nut plates will always fare better than rivnuts, which could potentially spin in the future and make it impossible to get the screw loosened or tightened without drilling it out.

One of the thing about the scoop, is it didn’t sit very flush to the bottom of the fuselage skin.. so I applied packing tape to the bottom skin in the area and then applied a generous amount of micro around the flange and screwed the scoop into place to cure and fill in the gaps etc.. between the scoop and the skin.

Once cured, I took the scoop off and sanded around the perimeter of the flange. (shown below prior to sanding.

The next step is to put the condenser coil in place and work on a template to drill holes into the bottom skin for the hose connections inside of the plane.

Intake part 2

Now that the basic shape of the left intake tube was formed, it was time to sand it down to perfect shape. I used mostly the Permagrit sanding blocks for this task, and it was relatively easy. Of course, at some points I had to put the lower cowl on to make sure I had clearance to it. I also carved out a bit more in the back for the AC hose connections to the compressor.

Foam sanded to shape

I then laid up 4 layers of cloth and put some peel ply over the top and let the tube cure overnight.

Of course prior to doing this I covered the foam in packing tape as a release agent and also sprayed some silicone based release agent on that for good measure.

Once cured, I removed all the foam inside of the tube and test fit it.

I then cut some cloth to close out the top part of the tube where I had cut for clearance to the compressor. 4 layers again were laid up and peel ply placed over the top.

Closing out the top of the tube.

Once cured I test fit the tube once again to make sure things looked good. below you can see the blue sharpie lines that I used to mark the cloth for cutting pieces to shape.

Tube clearance to compressor
Aft view of bump in for AC hose connections
Closer look at the bump-in.

Then it was time to wrap a single piece of cloth to span the gap between the two tubes to join them back together. You can see the black line I marked for alignment. I also used a jack to allow the tube to sit on vs. having gravity pull down on the tube while this was curing. I used a single layer on the outside, because clearance to the cowl is a bit tight. Once this cured, I placed a thick layer of flox on the inside of the tube to fill the gap and create more strength in this area.

re-joining the tubes.
Complete except for some sanding.

One of the other tasks that needed to be done was to redesign the air ramps seeing I’m using the Showplane’s cowling and the stock metal ramps were cut out for this intake system. I fabricated a .032″ thick piece wide enough to go under the baffle angle and still protrude enough to serve as a flange for the new ramp. This will be bent downward somewhat depending on the angle between this and the from of the intake. It’ll provide a nice flat surface for attaching the ramp material to with screws.

I also bent up some of the side baffle material to provide 1 screw location. I also decided to fabricate up a metal piece that sits up front on top of the intake area. It has a bent flange that will rivet to the side baffle material. I’ve left everything to the inside (closest to the flywheel) long for now. Once I get the center baffles completely figured out this area will be trimmed and I suspect some aluminum angle will be used with some screws to connect the front metal piece to the aft piece I made with screws.

Picture of ramp area prep for screws and carbon fiber ramps.

I then cut some carbon fiber material I bought for the ramps to fit in the ramp area. Again, leaving the inboard side long for now.

Test fit right ramp material

I then match drilled everything, added nut plates, and screws to hold everything down.

Right Ramp.

I put the center baffle material in place after cutting it somewhat. This will need to be angled back towards the intake opening. In fact, I may cut the piece coming out towards the flywheel and rivet in a new piece of my own at an angle to achieve this.

Right Center baffle piece in place

I really had to trim away the left center baffle piece. It interferes with the AC compressor quite a bit. So I decided to cut the forward most section completely off, leaving enough material to rivet more metal to later, and also the notch for the aft part of the prop governor. Later, I’ll work on a custom piece to go over the prop governor and along the ramp to the intake area.

Working on the Left center baffle
Match drilling the hole for the 2 center baffles.

The same process was repeated for the left, with the exception that the compressor complicates the ramp..

Metal flange for ramp added

I decided the best way was to use construction paper to create template prior to attempting to cut the carbon fiber piece.

Creating a template
Transferring template to carbon fiber.
Ramp cut and in place.
Another angle
Bending up the side baffle for a screw location.
Ramp in place!
Another view. Looks like a #6 nutplate made it into my #8 bin.. I’ll have to fix that at some point..
All finished up with the left center baffle in place.

More panel pics

Just a quick update with some additional pics of the backside of my panel in progress at Aerotronics.

Probably a couple more weeks before it’s ready to ship.

Closeup of the G5 and switches above.
Note the switch pod up high
A nice closeup of the shelves that house most of the subcomponents including the FlyLED controller.

Air In…Take 1

The next area to tackle was the air intake system of the Showplaces cowl. Fiberglass tubes were supplied which take up the bottom 1/4 of each round air inlets on either side of the cowl. These tubes house air filters (one on each side) and join together with a servo plenum. The plenum connects to the SDS throttle body.

These intake tubes cause several deviations including the bottom inlet ramps needing to be completely cut away. I spent some time getting the inlet ramps cut to match the baffle stiffeners on the front of each side of the engine.

Right baffle stiffener
Left baffle stiffener

I then started to try to get the servo plenum and right intake into position. There are no obstructions like the AC compressor on the right side, so it’ll be the easier side to start with. I did have some trouble getting the plenum onto the SDS throttle body. It’s the correct size (3.5″ ID), but just didn’t want to easily slide on. Bryan at Showplanes suggested cutting 3/4″ slots at the 9 and 3 o’clock position, which is what I did.. That seemed to work better and still gave a nice tight fit.

double checking the ID of the servo plenum.
Plenum didn’t want to slide onto throttle body inlet.

Once I got the servo plenum in place, I quickly noted two things

  1. The left side air filter and tube in general is going to have major conflicts with the compressor and the 2 hose connections coming off the bottom of it. This was mostly expected based on builders that have gone before me.
  2. Due to my cowl being shifted forward quite a bit based on my prop/hub combo.. the servo plenum will need to shifted forward as well and an extension made to mate up with the throttle body.
Left side Air Filter will cause issues with A/C compressor
Need to shift the whole thing forward to get the inlet just behind the cowl opening

I wrapped some packing tape all around/over the throttle body and did a layup of 4 layers of glass to create an extension for the servo plenum.

Letting the extension cure overnight.

Once that cured, I worked on properly positioning the right intake tube. This was fairly straightforward and didn’t require any cuts or mods to do so.

Positioning the right intake
Rough gap to cowl.
A view from below.

One of the other benefits to my cowl being so far forward, is that the intake tube didn’t need to be modified to clear the #1 exhaust pipe. Below is a picture of the intake tube in place and you can see the stock bump in for clearance. Many other builders had to cut this area out and bump inwards more.

Clearance to #1 exhaust

It was then time to use the provided fiberglass sheet to secure the top part of the intake tube to the baffle stiffeners. I cut a piece wide enough to capture 3 of the holes in the baffle stiffener, enlarged to accept #8 screws. Some triangular pieces were also cut to strengthen the joint as these two pieces are bonded together. I also used a piece of aluminum to hold the intake in place while the flox was curing. Also of note the side baffles needed to be trimmed to match the curve of the intake

Getting ready to bond the two pieces together.
Flox on and curing overnight.

The right side was then mostly complete.

Right side mostly done.

I then experimented with some ideas for the left side. Through some reading and asking around.. it seems several builders that have a Showplane’s cowl and AC compressor have chosen to run unfiltered air for the left side seeing there is significant conflict in this area.. I wasn’t too thrilled with this idea.. As once you’re running unfiltered, air will take the path of least resistance and all go through the unfiltered route.. why bother putting in redundant air feeds in this case at all? Although I suppose it would still allow for an alternate air path in the case one side got blocked. I explored some options.. the one I settled on was to adjust the left side to angle the filter downward (more horizontal). Below you can see my attempt at looking at this from a clearance perspective to the AC.. Of course, you also have to balance that against the space you have to the lower cowl..

Filter more horizontal idea.

I marked out lines to basically cut the left side off entirely. I also cut the neck down off as indicated by the right-most lines (well the left-most (bolder) set of the right lines), to allow the filter to re-attach to the stock flange and not have to fabricate something up myself. This is basically cutting 2″ out in the middle and re-attaching the flange back to the plenum.

Marking out the cuts to make to the left side.

What I found was that if I slid the flange part onto the end cap and placed that whole “sub-assembly” onto the servo plenum, it wasn’t too bad of a size mismatch. I taped this up initially to look at clearances prior to floxing the whole thing together.

Filter, flange and end cap taped into place on plenum
Clearance to AC and hose ends
Finally checking clearance to the lower cowl.. There’s plenty!

I took the plunge and cut the servo plenum.. Hey it’s just fiberglass and I can fix it (I suppose) if I mess it up really badly.. 🙂

Floxing it all back together. I’ll eventually sand this down and probably lay a layer or two of cloth over this area.

I then followed the same procedure as the right on the left side (with the compressor removed for now)… I did, however, decide to cut the tube in the middle because of the angle being way off due to my previously described cuts to the plenum.. I chose to insert the tube into the filter end and cut it so that its length is just beyond the filter. Again no need to try to fabricate up a new piece to fit into the end cap when I’ve got a perfectly good piece to do so already.

Aligning and floxing the left side
Cut of the tube just at the end of the filter.

I then made some relief cuts to the inlet area around the compressor. Both at the intake area and down the length of the tube.

Relief cut

Looking at the angle of this tube relative to the compressor connections.. it was clear that not even this cut will work and cutting more will just cause a very thin tube.

Another angle of the initial relief cut.

It was at this point that I decided it was probably best to just fabricate a new tube between the intake piece and the filter piece. I cut the intake piece up a little closer up at the widest part of the tube.

Cut off the intake piece

In order to fabricate my own tube.. I decided on using a high density expanding pour foam. To do that, I used poster board covered with wax paper and a bunch of duct tape to form the basic outline of what I was after. This tube would connect the 2 pieces together. The liquid foam would be poured into this and it would expand out to fill out the tube.

Posterboard tube

I tested out a very small mix of the expanding foam with Declan. He was pretty excited about the experiment. First the foam I ordered.

I mixed up a very small amount and we witnessed how much expansion happened. Pretty cool!

Declan and I cut up the foam once cured (about 15 minutes) and he was happy stacking the blocks we created.

After that experiment Declan was exited to get to work on the foam for the airplane.. So I mixed up an initial batch which seemed to fill up the tube pretty close to full.

After first pour.

You can see the foam found its way out the plenum side too. Of course I put a cap on this filter side, so it wouldn’t go inside the tube.. This excess will easily be cut/sanded away.

The end result of the second pour.. I captured a short video of the liquid expanding in the tube.

Final pour results

After everything was cured.. I took the poster board off to see the results. Seems pretty good.. Lots of sanding left to do to make this a much smoother tube. Once that is done, I will lay up cloth over the foam to form the custom tube.

Cowl Baffles

Now that the main part of the cowl is fitted, it was time to move onto getting the baffling started.

The start of section FF2 of the plans.

You start off by marking up the #6 cylinder baffle for the scat tube that’ll go to the oil cooler. Also some holes for the top spark plug wires to pass through. Below you see the flange located in place and some holes drilled per plans.

The inner and outer circles were marked. The inner circle was cut out to allow air to flow through to the oil cooler.

Holes for oil cooler and plug wires cut

The entire #6 assembly is then all riveted together.

A similar thing was done for the #5 baffle. The one thing I did different here was to utilize the RV-14 baffle modification. This provides more space between the aft-most cylinder fins and the baffling to get cooling air through and avoids doing “the washer trick” that several refer to.

It’s key to do this prior to cutting the 2” duct hole as it will need to move up.

I started by cutting off the existing piece of the baffle that wraps around the cylinder.

Cut off baffle piece

I then put the CB-00028, CB-00029, and CB-00030 pieces I ordered from Van’s in place of the wrap around piece that was cut off.

Below you can see that I relocated the 2” duct hole a little higher up on the baffle compared to the plans.

Baffle #5 complete

I worked on adding the doublers on the other baffle pieces only to end up with a pile of baffle parts ready to trim, as needed, to fit around my valve covers.

I worked on fitting the #5 and #6 cylinder baffles in place and putting on the Aerosport engine mount covers. 3 #6 screws were used with nut plates to attach making sure to not drill into the mounting ears.

Below the baffling is complete, yet to be trimmed.

In anticipation of starting on the Showplanes intake I temporarily installed the exhaust pipes.

Right side exhaust pipes in place
Left side pipes

I also worked on making sure my AC compressor was as close to final position as possible. It’s a bunch of tweaking with a couple of different belt lengths, mounting spacers, and arm lengths, to get it all right. There is very little space between the belt tensioner and the starter.

AC compressor and prop governor in place
Minimal spacing between tensioner and starter.

Hidden oil door hinge

In order to have a nice smooth and clean looking top cowl with no fasteners, I’m doing a hidden oil door hinge for opening. I utilized a spring based hinge so the door will pop open and stay up when opened.

Spring hinge

The first step was to trim the oil door on the scribe lines that came with the Showplanes cowl. This piece matches the curve of the cowl perfectly.

Marking the scribe lines

Then I marked out a 3/4″ line for a flange on the recessed part of the oil door location. A small amount of sanding was needed to have the door fit in the recess area. You can see the door fitting nicely below and the marks for the flange behind it.

Oil Door fit and flange marked.

I cut the recessed area carefully and seeing it also follows the curves of the cowl, I used it as a stiffener on the back side of the oil door. I utilized flox and drilled a bunch of holes (which will be filled in later) to make sure there was a good bond between the two. I also used clecos around the perimeter to makes sure the door held tight to the cowl during cure.

Door stiffener curing

I again used some flox and some packing tape to fill in the gaps between the spring hinge and the oil door. The hinge sat an an angle and it required a bit of a buildup to fill in the gap.

Flox filling in the gap under the hinge

It was then time to work on the opening hinge mechanism. I utilized piano hinge for this. On the oil door side it’s just wide enough to allow the hinge to pass through the opening.. The mating side on the cowl is a little longer and I made it a little longer on the forward side, which required a little hogging out of the foam area around the oil door perimeter.

Below is a bigger view of the front cowl as I was prepping for drilling holes to attach the hinges to the cowl and oil door. I used the normal hinge pin for fitting as it’s slightly bigger than the bowden cable wire that’ll be used.

Below you can see all the hinges riveted and the Bowden cable roughy in place. This will ultimately be attached to the inside of the cowl and the pin cable will be cut so that the pin is just inside of the left air intake hole. I’ll be able to grab the pin and pull it causing the oil door to pop open once the pin has been extracted far enough. I’ll need to wait until I finish the air inlet ramps to complete the cable part of this.

Oil door complete for now

Prop has arrived!

I got an email that my prop was ready to ship from Florida.. So I wired the final payment and waited about a week before I got a call from the freight company to schedule delivery. The crate arrived unscathed.. and I opened up the front cover to take a look. It’s a thing of beauty.

MTV-9 Prop

They really do crate these things well. The prop was mounted to about a 2″ thick piece of plywood with nuts and washers. That was bolted to the crate. Below is a pic of the crate in reference to my garage door. It’s pretty big!

Empty crate

Later that night I set to work removing the prop from the crate and mounting it to the plane. I really wanted to see how it looked and also wanted to see how well the cowl fit and the gap between the aft part of the spinner/spinner backplate and cowl. Using the cowl tool was one of those times where you measure 10 times before you start to cut. I utilized my engine hoist and some straps wrapped around the root of 2 of the blades to lift the prop up while I lined it up and threaded the bolts into the flange. The end result is awesome, and I’m happy with how it looks and came out!

MT had advised to shoot for 1/4″ gap and had said that the spinner dome will overhang the backplate a little bit, so the gap will end up a little less. A bit bigger gap is also recommended for a 3 blade prop for getting the cowl on and off easier.. Of course that’s not as much of a concern for me with the lower half of the cowl split into 2 pieces.

In the end, all the measuring and use of the cowl tool placed where the spinner would be resulted in a consistent gap that I’m pretty happy with after fitting the cowl without the prop in my possession

Cowl to spinner gap