Hello Aleatorylamp,
The measurements I am getting from my version of Paul Matt's P-39Q drawing are a little different.Originally Posted by Aleatorylamp
There is a noticeable gap between the back of the Spinner and the Fuselage.
I am getting 1.35 feet to the back of the Spinner and 1.42 feet to the joint at the Fuselage.
This is one of the strange parts of this drawing.
I have never seen another like it and photographs and films do not show this gap.
Originally Posted by Aleatorylamp
Keep in mind that we are discussing rounding errors here.
30 feet 2 inches = 30.16666666 feet which I initially rounded to 30.17 feet.
From looking at other drawings, I believe that the actual object was about 1/16 inch shorter which is why I rounded it down to 30.16 feet.
Now the difference between the Datum and the Spinner Tip is 3 inches or 0.25 feet thus 30.16 - 0.25 = 29.91 feet.
Of course if you start from 30 feet 2 inches - 3 inches = 29 feet 11 inches = 29.91666666 feet, you might round differently.
I made a choice based on what information I had.
The relevant drawings are all in the Airacobra thread.
Originally Posted by Aleatorylamp
I guess the difference here is that you are working entirely from proportions from drawings and I am throwing in actual measurements from the aeroplane whenever I can.
As an example, the Propeller Diameter of my AeroProp is 10 feet 4.5 inches or 10.375 feet.
This is rounded to 10.38 feet in the model. (An even number is good because it is really the Radius we will be using and not the Diameter.)
Radius would be 5.19 feet
As soon as we go through your multiplier, the new Radius would be 5.19 * 0.991932 = 5.14812708 which rounds to 5.15 feet.
My Propeller just lost about 1/2 inch off the Tip of each Blade!
Regarding AIR files:
I tried to pull some dimensions from the Monografie drawings and use them in the AIR file and that was a mistake.
The scaled dimensions do not agree with the documented dimensions, so I am going with what I can infer from the documented values.
I will need to undo most of what I put in at some point.
- Ivan.
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