Jabiru Cabin Heat
Just a brief overview of how a cabin heat system was made for an Xair Hawk. This engine was fitted with a single outlet pipe silencer, so standard dual pipe types will need to modify cutouts to suit. Drawing below is just a rough scanned sketch of measurements to give you a guideline, maybe in the future I will put together a more accurate & detailed drawing.
The jacket around the silencer is made in two halves (shells) which are made from aluminium sheet and 10mm alum tube as a stand off/spacer. The inlet and outlet pipes are folded aluminium to suit scat pipe used. On the Hawk we dont fit a pipe on the inlet as there is enough air flow inside the cowling so the inlet was made square for simplicity.
Find a suitable former (fire extinguisher used here) preferably slightly smaller (3 1/2") than the diameter of the silencer (4") and wrap your tube around it as shown. We used 10mm aluminium tube bought in a local DIY stores like B&Q, Homebase etc it comes in 1M lengths. You could also use copper tube if you wish. Try to end up with two 4" inside diameter rings.
Below is rough sketch from the one made above, one half of the shell is wider, as it is designed to overlap the other. Cut the aluminium rings so they are flush with edges of the smaller (205 wide) smaller shell. see picture above. Pop rivet the ring to the alum sheet. Pop rivet the other half rings to the wider (210mm) sheet so that there is a lip on each side, which will over lap the other half.
Fold up some inlet/outlet pipes (top hats) to suit dia of scat hose, (40-50mm best) if you roll a tube you can make a series of slits and fold them over on the inside (see pictures above and below) then pop rivet in place. Shells are clamped in place around silencer with two large hose clips (see top picture).
The selector box can be bought commercially normally they are a "Y" shape, with a inlet and two outlets, one for cabin and the other for dumping hot air. On the hawk installation we drill a 50mm hole in the firewall and a folded up (see drawing above) selector valve is mounted over the hole with a flap actuated by a push/pull cable (Car Choke cable) and warm air is just dumped out the bottom.
Some pics of the selector valve are shown below if anyone feels they would like to make up there own, rather than buying a commerical one. The flap is hinged at the bottom, which closes off the warm air going into the cabin and is dumped out the hole that the actuating cable enters. The scat hose fittings (top hats) are made as the silencer jacket above.
This selector box could be made with a top hat on three sides if you wished to use a dump pipe and a seperate pipe to enter cabin. To do this you would need to make a different flap lever mechanism so it could be operated outside the box. This could be done by using the pin on the hinge and extend it through the side of the box, and a lever fitted to it on the outside.
Scat hose is clamped to the top hats with a Hose clip.