You're probably not driving it fast enough to cool itself--They'll put out
their rated amps at a low speed, but they're used to turning quite fast in
long time operation.
Calculate the cruise rpm from the auto it came from, then on your plane---

I drove one on my lathe as fast as I could, both fwd & reverse & could
find
hardly any difference in cooling air output.

Paul Lee wrote:

I am using a mini Denso 45A alternator that just went on me when I put
the whole load on it. The load is not more than about 30A but is
continuous. Had another similar size alternator quit under load. What
is the problem/solution?

Since these automotive alternators are CW rotation (the cooling fan,
not the rest of the alternator) is this the problem - or does it
matter much? Or where can I get a lightweight CCW alternator or a
replacement fan for it? Or the rated load capacities are peak and need
bigger alternator for continuous 30A?

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SQ2000 canard: www.abri.com/sq2000