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Andrew;
It may make a difference on what the plane is; and on how high you intend to
fly.
I have a 20B on a Velocity SE RG, which also has the IO360 as the
recommended engine. I think the choice is not just 20B vs 13B; but rather vs
turbocharged 13B. A NA 13B is probably not in the running, especially for
high altitude cruise. If you are going to have O2, and like to fly those
x-country trips above about 12,500, go with the turbo 13B (with
intercooler), because it will give more power up there as the NA 20B with a
less weight.
I'd also suggest that a renesis with a 2.81 (or higher) redrive ratio may
be an excellent choice. New engines available for less than you could get
for your 20B, and NA should give you 20-30 more HP than the IO360 at less
weight. The all-up NA 20B will weigh about 50 lbs more than the IO360.
Al
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Andrew Martin
Sent: Monday, October 01, 2007 9:21 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] motor decisions!
Hi
I have a 20b and about to start building a plane that is designed for a
IO 360. It has been suggested to me that I should change to a 2 rotor to
save weight. I’ve gone through the archives but didn’t really find any
pro’ and con’s of 3 or 2 rotors other than the max power available.
The plane will be used almost exclusively for long X-country cruising
once the bugs are worked out and hours flown off.
If my estimated max power required due to VNE is around 200hp, is the
Renesis always the engine of choice or are there advantages to keeping
the 20b, accepting the weight penalty and letting the engine loaf along.
I originally presumed the 20b would be better for me especially when at
my gross weight of 2420 lbs. but now I am unsure, so to change now
rather than later would be easier.
Any help from anyone flying either engine, and points that governed your
engine of choice would be greatly appreciated.
Regards
Andrew Martin
Western Australia
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