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Starduster
| During the overhaul we decided to take on a couple of special projects. Well, not that we don't have enough work to do to get 45GG back in the air, but since everything was apart... N45GG runs about 214 degrees most of the time in the summer. While this is within recommended limits, I thought it could be a little better. Since we were going to have to rebuild the baffles anyway, we decided to build a fully enclosed plenum box for the engine to improve the cylinder cooling and just make the cooling system a little more efficient. Jayson had built one for one of his planes and it had a dramatic effect on the cooling, not to mention an additional 9 mph in cruise, so we wanted to give it a go here. So basically, the reasons for going to all this additional trouble are:
The box was made out of .032" 2024 T3 Aluminum except for a couple of stringers which were .040". We debated on how to do the top. Jason planned on putting panels in the outboard part of the top so you could change the spark plugs. I thought it might be just as easy and a little stronger to screw the top on and you could just remove the whole top if you needed to get to the plugs. The debate continued... We decide to go for something a little different. We'll screw the top on as well as the back two halves so the whole plenum is completely removable whenever we like without tearing the whole thing up. We cut holes big enough for a plug wrench above each plug and cover with two-piece plates that wrap around each plug. Each plug has it's own cover. We installed nut plates on the top for each plug as well as around the border so the top can be easily removed. We put a doubler around the top of the entire box for stiffness. We installed nutplates under the doubler and countersunk the holes for the AN426A-3-4 flat top rivets so it would be easy to take the top off and on. While the top may be easy, the nutplates took forever to put on! Mostly we used F5000-08 nutplates, but used K3000-8 in the corners and F2000-8 at the edges. The inlet for the heater used to be on the back of the old baffles behind the #4 cylinder. We relocated the inlet to the front of the engine so we don't steal air from inside the plenum. This should keep our airflow where we want it and provide a good flow for the heater. The only outlet on the back of the plenum is a small length of 1" SCAT to cool the fuel pump. We thought about painting the Plenum Box when it was finished but I liked the look of the silver against the black engine so we decided to burnish them. Should make it very easy to keep them looking good. After they were done, it really gave the plenum a very unique look.
Jayson had some personal issues to deal with so he was out of touch for quite a while. Actually, I eventually gave up and decided to finish it up. Thank goodness he had done most all the hard stuff! I took my time and have no doubt that this is one of the strongest boxes going! Plenum Is Finished! January 3, 2005Unfortunately, it's now the first week of January, 2005... much, much longer than I wanted this whole process to take but at least its finished. Ok, so now we finish the Nose Bowl and we're ready to fly!
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Cylinder skirts were connected with a threaded rod with a spring on either
end to maintain tension. I'm not sure if we're going to keep this but it
was an interesting experiment anyway. They are tightened down so much
there's not much give.
