Dear Group:

I was looking at Mick Duckt's web page on his ducted fan long ez, and
noticed that the 13b is capable of producing between 80hp to 120hp in

the

3500rpm to 4000rpm range. Considering the orginal long ez was designed

for

the 0-235, and the plane achieves good performance with the 0-235. My
question is why not get rid of the psru and save the weight and

complexity?

How much would the engine efficiency suffer to operate at the lower

rpm?

Interested to hear any thoughts.

 Andrew Shaw

David Leonard wrote:

Andrew,

Since everyone else seems to be busy playing with their computers

instead of

building I will throw in my 2 cents.  Perry is doing a great and

reasonable

thing.  He is meeting the goals he set out to achieve but you should
consider a few points.

Most importantly, the thrust bearings in the 13B were not designed to

take

prop loads - or any significant amount of thrust for that matter.  I

believe

perry has replaced them once but otherwise they seem to be holding up

OK.

It is possible to replace them without doing a complete re-build, but it
does require removing engine from the plane.

If you are only hoping for 80-120 hp. you could get that from an

aircraft

engine for probably less weight and much more simple installation.

3500-4000 RPM is still too fast for most props without going to very

short

and inefficient blades.

As far as 'efficiency' goes (shaft h.p. per pound of fuel), slowing the
engine will imporve efficiency somewhat, but what you gain there is more
than lost in reduced prop efficiency.

All that said, Perry's plane FLIES, is RELIABLE, and INEXPENSIVE to

operate

and maintain.  What more do you really need?

JMHO,
Dave Leonard

If I were not playing with my computer you would not be reading this :-)

Paul Lamar

Dave,

   Thank you for the response, and Paul your the best. We are all greatful
for your help.
   Andrew

 
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