Exhaust planning, fuel line work

The front right exhaust currently interferes with the radiator placement, so we plan on rerouting that part of the exhaust to fix this.  Michael used his 3d printer to print up some straight pieces and bends so that we could make a mock-up of the exhaust routing first.  The pieces didn't snap well together, so we used some tape to hold it together while experimenting.  We came up with a relatively simple routing that bumps the exhaust out a bit to go around the radiator (The radiator is not installed in the picture below, but the radiator bracket is in place).  Exhaust parts were ordered, and I've been practicing some stainless welding in prep for this part of the project.

Mock-up of right front exhaust

Two holes were drilled in the firewall for the fuel inlet and outlet, and bulkhead feed-through fittings were inserted.  Due to the thinness of the firewall, two aluminum spacers (1/8" thickness) were made to ensure the nuts held these fittings tight.  A  T-shaped bulkhead fitting was installed to allow for a restricted bypass that is required by the Rotax 912is.  Hours:12

Fuel outlet in firewall (engine side)

Fuel fitting on back side of firewall

More Lower Cowl Work and Oil Lines

Continued working on the lower cowl modifications.  Additional Micro/Epoxy mixture was added to fill in the fiberglass weave and imperfections.  After allowing it to dry, it was sanded down.  The excess fiberglass on the inside of the cowl was removed as it was no longer needed.  A coating of filler/sanding primer was sprayed on the part.  This is VERY revealing and immediately highlights the imperfections.

Lower cowl lookng nice

Excess Fiberglass removed on interior

Filler/Sanding Primer Sprayed

We spent a few hours planning our firewall penetrations and what would mount on or near the firewall.  This was needed so we can start progressing toward installing fuel and oil lines.

We plan to have an oil fluid thermostat in our system.  This will hopefully help keep the engine oil at a more appropriate temperature, also allowing the engine to warm up faster, bypassing the oil cooler until the temperatures of the oil are elevated.  A bracket was made and the oil fluid thermostat was installed on the firewall.

Two oil lines were built and installed.  The first one goes from the bottom of the Rotax engine and to the oil tank. The second oil line was run from the oil tank to the oil fluid thermostat.

Hours: 12

Oil flows out of the engine to the oil tank on the Rotax 912iS

Oil flows out of the oil tank to the oil fluid Thermostat

 

Lower Cowl Fiberglass work

More work was done on the lower cowl in preparation to fiberglassing in the the front openings.  The 2 part foam was shaped with a 1/4" radius front edge.  After removing the gelcoat, it was found that some large air pockets were in the original fiberglass layup so that needed to be repaired with filler. 

Lower Cowl Ready for Fiberglass

Three layers of  omni-directional fiberglass were epoxied in on the front cowl and a final peal ply was added.  After a 5 hour cure, the peal ply was removed.

Fiberglass added

Peal ply Removed

The coolant radiator was mounted and all bolts were torqued and cotter pins were added where needed.  We used Titanium M10 bolts on the main brackets to help reduce some weight. 

Hours: 10

Coolant Radiator Mounted

More Lower Cowl Modifications

 With the openings for the Oil Cooler and Radiator set we set out to make the openings a little more pleasing to the eye and a little more aerodynamic.  A mixture of epoxy, flock, and microbeads was added around the two openings and allowed to cure.  Using a 1/4" round over bit and a router the edges of the openings were eased over, giving a nice pleasing look.  

Oil Cooler and Radiator Openings with round over

Angled view of the addition

We also determined that we wanted to close up the cowl openings on either side of the propeller.  After much discussion we decided that just closing off the bottom cowl opening (ala Steve Henry and others) would be the easiest and quickest way to achieve this.  We bought some 2 part expanding foam and after taping off the area we wanted to fill the foam was mixed and poured into the area.  Now we've got to shape the foam so we can add some fiberglass fabric to finish the opening close-out.

Expanding foam added to cowl openings

Hours: 10

Lower Cowl Openings

After a lot of tweaking on the placement of the Oil Cooler and Coolant Radiator, we think we've finally nailed it down.  New brackets were constructed to mount to them to the engine.  Also, a single bracket ties them together.  Rubber shock mounts were added for vibration isolation.

Original bracket used to determine correct spacing

Final brackets installed

With the locations fixed.  The two cowl openings were planned.  We drew on the cowling the maximum size and placement of the openings.  We started with a 4" hole and slowly opened up the hole until we were happy with the size to hopefully provide ultimate cooling air into the two cooling devices.  Our plan is to glass in some curve edges to make the openings more aerodynamic and provide some strength to the cowl in the areas that material was removed.

Hours: 24

Cowl Openings

Another View of the Cowl Openings

Lower cowl mod, Planning for oil cooler and radiator

To aid in the cowl placement, we created a thin 1/4 inch circular wood spacer that is the same diameter as the spinner, and attached it to the prop flange.  This is used to set the spacing between the back of the spinner and the cowl. 

wood spacer attached to back of prop flange

We then trimmed the back edge of  the top cowl in order to get it to fit into place behind the prop flange, and then attempted to attach the bottom cowl to the top.  Found out we had another interference issue as the top and bottom halves couldn't quite meet up.  This was frustrating as we had followed the instructions and had performed the initial cut to a "trim line" that was provided. That's what we get for following instructions.

 Luckily, we still had plenty of overlap between the top and bottom, so we just needed to fill in a few holes, and adjust the bottom edge to line up with the top cowl.  We used epoxy mixed with flock for added strength, and later added a few layers of dry micro (epoxy with added glass micro-balloons) to smooth it out.  Some sanding was done between each step.

bottom cowl modified to line up with top cowl

We also trimmed the back edge of the top and bottom cowl so there is now a straight line along the back edge of both top and bottom cowls.

Currently, we are planning out the placement and mounting methods for the oil cooler and radiator.  This is tricky as there isn't a lot of room.  We have considered extending the lower cowling down to provide more room, and have borrowed some cowling pieces from a friend that has a newer Rotax 914 cowl that allows for this.   We haven't ruled this out, but are currently focused on seeing if we can squeeze in everything with the existing cowl first, as this would minimize the weight added.  

We created a few test brackets with slotted holes that allowed us to vary the placement of the radiator, and also created a bracket for the oil cooler.   We cut a foam block the same size as the oil cooler so that we could play around with placement easier.   The first thing we learned is that the exhaust outlet from the front left cylinder interferes with the radiator hose with just about any position of the radiator, so we may need to build a custom exhaust for the left front cylinder.  We haven't got this all nailed down yet, but we're considering our options.  Hours: 16

Planning out position of oil cooler and radiator