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Date: Thu, 24 May 2007 23:30:39 -0400
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From: "Matt Hapgood" <matt.hapgood@alumni.duke.edu>
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Subject: convert 14V to 28V
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My 360 is a 14V plane, and now I'm considering changing it to 28V. I'd love
feedback on:
1. Insanity level
2. Difficulty level
3. Cost level

History:
1. I built the plane as 14v because I used many automotive parts (a few
lights, and more than a few engine components).  
2. It's a dual battery system, with a switch on the panel to choose the
battery that will power all the electrical components.  Single alternator.
3. The starter uses both batteries.  
4. All instruments are internally lit (no post lights, etc)
4. Avionics and instruments are currently as follows:
  a. Dual Garmin 430's - original OLD 28V only ones, therefore I have two
voltage converters  
  b. Sandel 3308 HSI (multivolt or 14V - I'm not sure which, but I know
there isn't a converter)
  c. VM1000 and VM100 remote annunciator
  d. S-Tec 30 with Alt hold (14V)
  e. King remote gyro (multi-volt I'm pretty sure)
  f. Microencoder


Here's why I'm thinking about converting:
1. I removed all of the engine electronics last year 
2. I am considering a panel upgrade, which has turned into a HUGE ordeal.
Originally I planned to upgrade only ONE 430 to WAAS...
plug-and-play-isn't-life-grand, but that had issues.  

First, the two 430's would no longer cross-fill.  I use that function often
and don't want to lose it.  Secondly, the wiring would have to change.

So then I thought, I won't tell my wife, but I'll upgrade both.  Then I
found out I'd be in for a few thousand in labor because the SN-3308 wouldn't
effectively talk to the GPS anymore, and the autopilot would need a remote
switch (all is currently controlled through the Sandel).  The only logical
solution is to upgrade to the new Sandel 3500 HSI, which makes it a 4-wire
connection and no remote annunciators needed.

So then I thought, I'll upgrade both 430's and buy the new Sandel... maybe
my wife will talk to me after a few months.  Not so fast.  The new Sandel
requires 28V, so I need another converter...  or I need to change one my
430's out for a newer multivolt and use my existing converter.

Now that I've got all this wonderful equipment, it seems a shame I can't fly
a coupled approach or even an enroute GPS course because of my crummy
autopilot... so maybe I should upgrade my autopilot.

In order to preserve my marriage, I found a couple of used S-Tec 55x's for
good prices (and if I stay with S-Tec I can keep my existing servos) but
alas, they are all 28V units.  So methinks, why not just change the darn
plane to 28V???

I figure I'd have to change a bunch of bulbs, and now that the engine is no
longer all electric, I could use my two batteries, rewired, to generate the
proper voltage.  I'd lose the redundancy (whatever I may have had
originally?).

So the question is - am I better off getting voltage converters and spending
my $$ converting equipment, or am I better off converting the plane to 28V?

I barely know a amp from a watt from a volt, so clearly this would all have
to be done by a willing expert (and where do you find them??).

Thanks for your thoughts,

Matt