Fuji_Abound wrote:
For all intensive purposes isnt drag proportional to the square of the velocity
I think that rule applies even to non-intensive purposes – whatever those may be.
Peter wrote:
significant tradeoff in strength
AOPA: "But in the vast majority of piston singles, retractable landing gear is impossible to justify given the added weight, complexity, and costs—both in maintenance and higher insurance premiums.: http://www.aopa.org/News-and-Video/All-News/2013/April/1/Efficiency-Rationalizing-retracts
Retractable gear are worthless if they fail to deploy either because the pilot skipped that step, or something goes wrong. Modern carbon fiber fixed gear have been shown to have little drag penalty especially when taking into account the added weight of retractable gear. It’s impossible to forget to deploy the gear when it’s fixed and in place…hence the lower insurance costs.
Imagine how much faster it could go though 
both in maintenance and higher insurance premiums.
An opinion from a well known US columnist who gets paid for having opinions opposite to those from another staff writer I read the US AOPA magazine too.
I doubt he even owns a plane and if he does he sure doesn’t get involved in its maintenance.
Retractable gear are worthless if they fail to deploy either because the pilot skipped that step, or something goes wrong.
You could say the same about reducing power to land… the throttle lever is worthless if you don’t use it.
Modern carbon fiber fixed gear have been shown to have little drag penalty
It was never shown thus.
especially when taking into account the added weight of retractable gear
Another myth. Piston GA flies so far up the curve that speed is almost not related to weight – see e.g. here
hence the lower insurance costs.
A myth in Europe, and probably in the USA too once you do a proper comparison which excludes different risk profiles of different pilot populations.
Following Peter’s post, I actually read the article.
That article is pointless, as all facts are twisted to arrive at a forgone conclusion.
I have owned a Cardinal RG for over 12 years, therefore I’d like to think I know the type pretty well.
There are too many design differences between a 177 FG / RG which are not mentioned in the article.
Completely pointless article I am afraid.
For data of differences:
One aircraft is injected, the other carburetted. There is no stock 177RG that achieves 200hp in flight.
The induction system is totally different on both types.
Depending on year, wing section is totally different.
That extra weight is not only down to the RG system. Basically it’s only 2 hydraulic cylinders, a pump and a few small switches and hydraulic pipe filled with oil. Not coming to an extra 145 pounds though.
Higher specification of the RG does add weight, too.
However, a Cardinal is a reasonably drag free design, especially the RG. Small improvements have very good effect.
Further drag reduction of a Cardinal FG’s gear has been proven to increase efficiency and performance greatly.
Today there are a host of products available. The Cardinal FG owner is always looking at ways to reduce drag.
The RG owner is usually only looking for more power upgrades.
A correct comparison should include fuel used to achieve a certain speed, as well as using CHT’s that are viewed with today’s knowledge as safe to use.
So the lower the speed the less you would be bothered.
At low speeds, you save on build cost, complexity, risk of failure, maintenace costs, and possibly have a safety advantage.
As speed increases those advantages disappear as to the square of the speed increase, the only issue is where the curves cross. 
Peter wrote:
Piston GA flies so far up the curve that speed is almost not related to weight
GA doesn’t climb out in that situation, and the airframe design is a compromise between climb and cruise speeds. So I think there’s indirect interaction between weight and cruise speed. It would be nice to have retractable wings , but that’s not (yet) under discussion
Yes; I would point to say Vbg being 95kt (TB20; most IFR SEPs with the predictable Vs of 59kt will be similar) whereas economy cruise is 140kt which is a very long way up the drag curve and most drag is parasitic.
Of course weight affects climb perf – you are converting thrust into potential energy there. 2x weight means 1/2 climb rate (crudely speaking).
As speed increases those advantages disappear as to the square of the speed increase, the only issue is where the curves cross.
That is where the debate revolves
Silvaire wrote:
but that’s not (yet) under discussion
Well, it has been discussed here: http://www.uni-stuttgart.de/akaflieg/projekte/die-flugzeuge/fs29-tf/
and here: http://www.akaflieg-braunschweig.de/prototypen/sb11/
I assume you rule out the slats of the Rallye and fowler flaps?
USFlyer wrote:
odern carbon fiber fixed gear have been shown to have little drag penalty especially when taking into account the added weight of retractable gear.
Please, enlighten me. Show me the calculations, do state your assumptions and boundary conditions.
So if you reduced the gross weight of the plane by cutting airframe weight and maintaining payload constant, then reduced the wing area to maintain the same climb speed AoA, would it as a result go faster in cruise?
(I think I believe so, but would be happily corrected)
