The original exhaust was coming loose. The well nuts used to
hold up the muffler hangers had pulled out of the fiberglass and were
mostly just hanging loose. Given the weight of the exhaust system,
the vibration and heat, the wellnut solution was prone to fail over
time. So, I reworked the hanger system to support the weight from
the top of the ducts. For each exhaust support I used two plates.
One plate is on top and one is on the bottom of the duct with four
aluminum spacers in between to keep the plates from crushing the
composite material when they are tightened down. The spacers allow
for just enough compression to reinforce the composite material. I
also wrapped the exhaust system to reduce the heat in the duct area.
Below are some pictures of the plates etc. The new plates are 5.5"
square. The small plate with rusted hanger is one of the original
plates that someone had to fix before with some bolts from the top of
the duct holding it up. I used stainless steel U-clamps which
should make maintenance easier later if need be.
March 2006. I noticed that the heat from the port engine exhaust melted a plastic part under the port duct. The plastic part a portion of the emergency flap system each duct is equipped with incase the respective engine fails and you have to continue on with one engine. The flap seals the duct area and keeps the lift pressure from being lost on the dead engine side. The plastic part is one of the side supports/walls and now that it is damaged there well be a sizeable leak in the port flap system which may well preclude proper operation. This is more than just a theoretical issue as an engine failure actually happened to a 512 being used for a tour business in California. With the flap deployed, they were able to return to the dock. However, the way the port exhaust pipe is routed, it is just about impossible to ensure that there is enough space between the plastic part and the exhaust pipe. So... I had a new custom port exhaust made and rerouted down the middle of the hovercraft. At the same time, I had the starboard exhaust replaced with stainless steel. Ian Royal and I wrapped the exhaust pipes and mufflers with hi-temp exhaust wrap which was no fun at all. Ian did most of the work and it is a real pain to get on your back and try to slide far enough into the duct holes to wrap the pipes. It was a fair amount of work and $$ but I should not have to deal with the exhaust again for some considerable time. I ordered a new plastic part from Canhover which I hope will be here soon. Pic 1 shows the melted plastic piece. Pic 2 shows what the part should look like. Pic 3 shows a part of one of the original pipes with heat shields made from aluminum tubing and springs used as spacers. Pic 4 shows the new routing for the port exhaust (the aluminum tubes were removed). The black plastic pipe between the exhausts is a water drain that drains the water that runs down the engine covers out the back of the hovercraft. In Pic 5 the exhaust pipes are wrapped and the silver material is heat shielding. Pic 6 is Ian wrapping the starboard exhaust pipe.
Pic 7 above is one of the top exhaust support plates I made (4 total) to hold up the exhaust pipes and mufflers in the inside of the ducts. Pic 8 - 10 show the new exhaust exit, the old exit that must now be filled in and the Stb exit showing the outside support plate that will be added to the Port exit soon. Pic 11 shows the wrapped exhaust with the newly routed Port exhaust on the left. Pic 12 shows the wrapped port muffler.
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