| Every part of ever aircraft can do one or more of the following. It can add weight It can add drag It can add lift.
Thrust is a form of lift, especially when produced by a propeller.
Drag can be on the airframe or the engine, and is a bad thing. Weight ultimately causes drag.
So... if you have to carry around the extra weight of the first 16 inches of a 72" prop, why would you want to cover it up? Why not have at least half of that 16 inches produce forward thrust? ...or at a minimum, help cool the engine?
The large spinner is at best a band-aid, that will cause aerodynamic drag in order to shield the aerodynamic drag from a honorably designed propeller, that causes drag on the engine (shielded or not) and additional weight on the aircraft.
I suppose that if you MUST use the IVOPROP, then this is an effective way to minimize the negative effects of using the prop, but by far, the tradeoff just isn't worth it.
The allure of in-flight adjustability is understandable, but in reality, it's difficult to beat a properly designed fixed-pitch prop.
On Tue, Aug 2, 2011 at 8:51 PM, Kelly Troyer <keltro@att.net> wrote:
Doug, Pat and All,
When Tracy tested the "IVO" against his "Performance Prop" he gained a lot in takeoff and climb
performance but lost considerable top speed and coolant temp went up.............He attributed both the
speed loss and higher coolant temps to the flat hub area of the "IVO" blades which his spinner did not
cover (added drag) and essentially blocked some coolant air from his radiators................This flat area
also as has been noted sucks up hp but produces no thrust..............
I have a three blade 74 inch electric in-flight adjust "IVO" prop for my "Dyke Delta" that if I live long
enough to get in the air will have a 16 inch diameter "Mustang 2" spinner which will cover most of this
flat area of the "IVO" blade hub.............The "IVO" seems to work well in the pushers from all reports
since the flat blade hubs are mostly shielded by the engine cowl in these installations............IMHO
Kelly Troyer
"DYKE DELTA JD2" (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo
From: Pat Panzera <editor.contactmagazine@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tuesday, August 2, 2011 8:48 PM
Subject: [FlyRotary] Re: Ross Farnham IVO testing
Jim Smith with his 150 HP, auto-fuel RV-6 is reaching speeds of 200 mph TAS using a fixed-pitch, three-blade wood Elippse propeller.
That's nearly 30 mph more than the Ivo, on the same? power.
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