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Old 12-17-2009 | 07:53 AM
  #32  
riot3d
 
Joined: Feb 2005
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From: oakland, CA
Default RE: Neptuno 170

Well, one step closer to completion.

For the header & pipe, I wasn't quite able to get them to line up properly at first. I've tried all different combinations – 822 & 823 header with 29 & 37 mm Nishioka pipe mount. Finally, I settled on the 822 header with the 37 mm mount. However, I still have to prop the pipe mount with two pieces of 1/8 wood block to get the correct angle. If you install the header & pipe correctly, you will not see any oil residue on the pipe deck and the bellypan, unless the engine is not tuned correctly. In addition, the pipe's O ring will last much longer. I have had planes for over 200 flights with the same O ring.

Plumbing & landing gear is also done, I'm going to use the supplied gear set for awhile. However, I may switch to a wider canard gear set on a later date.

One of the thing that we always have to pay attention to other than AUW – all up weight – is meeting the noise requirement. Since we're using props with longer diameter & higher pitch, tip noise is also higher. It is easier to manage noise on an all wood plane, but much tougher on a composite design, composite tends to magnify sound/ vibration. Therefore, we go the extra mile to lower the noise level by – using a good engine mount, balance the prop, secure all leads, even go as far as stuffing the spinner cone. As for glow, most of us uses a pipe stinger extension. I've been using an extension with a diffuser from Japan on the past two years with good results. However, before this year's WC, I have tried a new gadget from Japan – an exhaust tip restrictor that dampens the tone of the exhaust. Originally, I thought it was another gimmick from the Japanese. However, after installation, you could tell the exhaust tone is indeed mellower – both on the ground & in the air.

The set comes with an aluminum tip for installation onto the end of the stinger, and it has 4 openings with different diameters. After attaching the tip, you install the teflon extension the normal way. It probably cuts the top rpm by about 100 to 150, but should help passing sound a bit easier.

Final few steps is to install the cdi unit mount, enlarge the spinner cone to accommodate the prop & to determine whether to change the bellypan's release mechanism. It should only takes a few more evenings, I hope. However, with me, that can turn into weeks …
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