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Using the Vetterman exhaust there is only one place available to place a cabin heat muff. This is on the crossover tube for #3 and #4 cylinder. The heat muff itself did not put out enough heat so I stuffed the inside of the heat muff with a product known as Chore Boy stainless steel scouring pad. The scouring pad is composed of loosely woven stainless steel strands. After 40 hours, the scouring pad is still in the same condition as it was when inserted in. I have noticed no shredding or pulverizing of the pad from engine vibration.

Although the temperature output of the stuff heat muff did improve, there was still not enough heat for the back seat as noted on the Engine page of this web site, I had installed a larger oil cooler that has 13 tubes instead of the standard 7 tubes supplied by Vans. During the winter months, the supply air to the oil cooler has to be restricted by a butterfly valve to allow the oil temperature to remain in the 180-190 range. I decided to use the air after it has past through the oil cooler and supplement the existing heat muff air to the cabin. The parts needed were purchased from Van's Aircraft.

I fiberglass diverter box was made to support the oil cooler and route the exhaust air to the cabin. The sides of the diverter box consists of 6 layers of glass cloth and 2 layers of glass mat. The eight layer were required to support the oil cooler. Pieces of cardboard were taped together to build the mold for the box. After the part was removed from the mold, the open side was closed. This was accomplished by glassing 8 layers of glass on wax paper and then pressing the diverter box into the fiberglass. After the layups were complete the box was trimmed. Holes were cutout of the box to match the bottom of the oil cooler exit and the opening required for the diverter door.

The diverter door was cut from an aluminum sheet to match the opening in the diverter box. A 1/4" threaded rod was used to operate the door. The rod was supported by a brass bushing on each side of the box. Levers were made to connect the door to the pivot rod and also for the levers required to move the pivot arm. The levers were constructed so that when the control in the cockpit was pushed all the way in, the diverter door would open to allow all air to exit the cowling. A solid wire cable was used to operate the diverter door from the cockpit.

The DL-03 2" vent was attached to the left side of the diverter box. 2" scat tubing was routed from the diverter box to the DL-Y 2" Y-tube.

The 2" scat duct was attached to the DL-03 flange and routed to the DL-Y flange. The Y flange was attached to the original position of the duct from the heat muff. The heat muff air was then attached to the upward point arm of the Y flange.

The fresh air ducting to the open end of the T duct has been removed for clarity.

A dramatic improvement to the heat entering the cabin was noted with this arrangement. The flow into the cabin increased as well as the temperature.

I have had problems getting the heat in the front cockpit back to the rear cockpit. I have also had trouble eliminating the cold air draft from the rear of the canopy from coming forward and freezing my passenger's neck. This is my fix for both problems.

The air at the back of the canopy, on the RV8, is high pressure air. No matter how much insulation is placed around the canopy, cold air still finds a way of creeping through the canopy track and make its' way forward to the cockpits. Also I have noticed, when flying in rain, that water is pushed through the canopy track and stays on the top of the fuselage underneath the canopy.

My idea is to place two vent holes on either side of the canopy track on top of the fuselage just forward of the rear of the canopy, but far enough back that the holes do not show when the canopy is shut. I will also fabricate an air vent to place on the bottom of the fuselage tail to exhaust the air overboard. The vent holes and exhaust vent will be joined together with 1" cat ducting.

BOTTOM AIR VENT
The air scoop design was drawn on a piece of plywood. Modeling clay was used to define the overall shape of the vent. After the modeling clay was correct, a 1" dia by 1 1/2" long tube was pressed into the back of the vent. This would be where the 1" ducting would attach. The mold, tube and plywood were smeared with car wax as a release agent. Four layers of bi-directional glass were applied to the mold. After curing, the air vent was removed from the clay, and the 1" tube was removed.

The vent was then primed and the mounting holes were drilled. A pattern was made from the recessed scoop and transferred to a piece of cardboard. The cardboard was trimmed to match the opening of the scoop. The mounting holes on the part were transferred to the cardboard template. This template will be taped to the bottom of the aircraft so the outline can be traced onto the fuselage.

PLENUM CHAMBER

Since the curvature of the fuselage would not allow the use of standard duct flanges, I needed to make a plenum chamber, underneath the skin of the fuselage below the vent holes, that would funnel the air to the 1" cat ducting. The plenum would be located in the baggage compartment just forward of the aft bulkhead.

After marking the location of the 1" dia. holes, I made a fuselage cast of the curvature of the fuselage in this area. This cast would provide me with a representation of the fuselage, at this point, to fabricate a plenum chamber. After covering the fuselage area with saran wrap, I laid up 5 peaces of bi-directional fiberglass cloth and 2 layers of fiberglass matting on both sides of the canopy track.

Once the piece had cured, I marked off the baggage compartment aft bulkhead on the cast and also tentatively marked locations where I might place the 1" holes. To hold the part together, so I could move it to the workbench, I used bondo to attach to wood blocks. This would allow me to flip the part over and build the plenum chamber. Masking tape was used to fill the gap between to the cast haves and car wax was again used as a release agent. 5 layers of bi-directional glass was glassed over the original cast. The new lay-up, which will be referred to as the skin thickness casting, would simulate the thickness of the fuselage skin and it would also provide a solid surface to fabricate the plenum chamber.

Splash layup of outside of
fuselage skin - Fuselage Cast

Wood blocks attached to hold
splash layup in place

Splash layup on workbench. Masking tape
was used to close the opening caused by
the canopy slide track.

It took some thought on where to place the 1" holes. I had two choices, behind the baggage compartment bulkhead or in front of it. After measuring, I concluded that it would be best to place the holes in front of the baggage compartment bulkhead. This would allow clearance for any insulation strips that were installed on the canopy and also place the holes so they could possibly pull heat from the front cockpit to the back. Once the hole positions were finalized, a 3/32" hole was drilled in the fuselage and skin thickness castings at the center of the 1" hole's position.

My plan was to place a 1"dia. hole in the aft bulkhead to allow the plenum tube to go through. There is a tooling hole in the aft bulkhead that would be used as the center for the hole I needed. I covered the new lay-up on the fuselage cast with masking tape. I marked off the location of the aft bulkhead and the location for the 1" holes on the fuselage. Using modeling clay again, I molded the plenum chamber. 5 layers of bi-directional cloth was used. Once the main body of the plenum was achieved, I pressed a 1" dia. by 1 1/2" long tube into the mold. The tube was place so the center line of the tube would be 1 1/4" from the fuselage skin. The reflected the location of the tooling hole in the bulkhead.

Clay mold on inverted skin thickness casting

Plenum removed from mold.

Finished plenum with
1" tube attached.

The plenum was pulled from the clay, and was placed in the baggage compartment where it would be placed. There was a canopy rail attach screw and nut that penetrated the mounting flange of the plenum. The plenum was trimmed to allow for clearance of the nut.

Going back to the fuselage casting (many times), the location of the 1" vent holes were again confirmed. Using the position of these holes, the mounting holes for the plenum were marked and drilled. Using the plenum as a guide, the mounting holes were transferred to the fuselage casting and skin thickness casting.

The tooling hole in the aft bulkhead was enlarge to the 1" dia. needed. Tape was applied to the inside of the fuselage skin to aid in marking the mounting holes for the plenum. The plenum was held in place and the holes were marked and drilled.

The fuselage casting, minus the skin thickness casting, was placed back on the fuselage. The mounting holes, for the plenum, on the fuselage casting were aligned with the holes drilled in the fuselage skin and the fuselage casting was clecoed in position. The 1" hole locations, on the fuselage skin, were marked by inserting a pencil into the 3/32" holes drilled previously in the fuselage casting. A progressive Uni-Bit was used to drill the holes.

1" hole drilled in aft baggage bulkhead

Vent plenum attached to fuselage skin

Locating position to drill 1" holes using the plenum attach holes for a reference.

Exhaust vent holes exposed with canopy retracted.

Exhaust vent holes hidden with canopy closed.

Exhaust / Vent Layout

Preliminary flight tests show the vent holes are exhausting air overboard and eliminating the cold air on the rear passenger. The exhaust vent is also pulling air through the shoulder harness slits behind the rear seat and pulling air from the sides of the canopy. These areas will be sealed. Heat from the front cockpit is now being felt in the back cockpit.


Cardboard mold.	Glass layup in mold.	Part removed from mold.	Closing open side of box.	Completed glass layup.	Cutouts required for oil cooler and door.	Hardware required to operate door	Diverter Door in closed position	Linkage required to operate door


Splash layup of outside of fuselage skin - Fuselage Cast	Wood blocks attached to hold splash layup in place	Splash layup on workbench. Masking tape was used to close the opening caused by the canopy slide track.


Clay mold on inverted skin thickness casting		Plenum removed from mold.	Finished plenum with 1" tube attached.


1" hole drilled in aft baggage bulkhead	Vent plenum attached to fuselage skin	Locating position to drill 1" holes using the plenum attach holes for a reference.


Exhaust vent holes exposed with canopy retracted.	Exhaust vent holes hidden with canopy closed.