Official Fulqrum Publishing forum - 109 prop pitch (rpm) and the supercharger

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Official Fulqrum Publishing forum (http://forum.fulqrumpublishing.com/index.php)

- FM/DM threads (http://forum.fulqrumpublishing.com/forumdisplay.php?f=196)

- - 109 prop pitch (rpm) and the supercharger (http://forum.fulqrumpublishing.com/showthread.php?t=34328)

bongodriver

09-14-2012 02:14 PM

Quote:

Originally Posted by JtD (Post 460823)

I find that very insulting. I'm not calling you names just because you don't want to "believe" a simple technical fact.For your consideration: 1500 rpm with a 3.1m diameter prop is 240m/s prop tip speed. Combined with 430km/h cruise you're at 270m/s. If you now consider going supersonic (300ish m/s at altitude) is a bad thing, you might find the figure much more believable. Hope that helps, even if my charm is still lacking.

I was eqally insulted by your sarcasm, I don't recall putting my query in any form that called your intelligence in to question.

Al Schlageter

09-14-2012 02:16 PM

bongo, what is the prop tip speed of a 3.1m prop at 2400rpm and 1500rpm?

ACE-OF-ACES

09-14-2012 02:50 PM

Quote:

Originally Posted by Crumpp (Post 460705)

Completely out of context. Silliness like this adds nothing to the discussion and simply an attack.

Attack?

Not at all.. I am simply pionting out that what you said about how to fly a Bf109 is in conflict with what Steinhilper said about how to fly a Bf109

At which point it is up to the reader to choose who they want to belive

Thats all

Crumpp

09-14-2012 03:22 PM

Quote:

Originally Posted by bongodriver (Post 460824)

as soon as I'm shown data that says a prop turning at 1500 rpm is going to be efficient.....yes I would happily accept it, it's all I'm asking for and not a tirade of sarcasm.....so you can stick your little blue face up your rectum.

Quote:

Maximum helical tip velocity is an important parameter for propeller selection. In the absence of specific data from the prop manufacturer, it is safe to assume that (a) the maximum prop efficiency will be about 87% (for any metal prop a non-governmental agency can afford), and (b) that the prop efficiency begins to decrease dramatically when the prop is operated at a helical tip velocity in excess of 0.85 Mach. That occurs because the local air velocity over the surface of the prop (near the point of maximum airfoil thickness) will reach Mach 1, and create a shock wave, separating the flow and dissipating prop energy.

http://www.epi-eng.com/propeller_tec..._propeller.htm

You should probably spend more time reading such things as the Pilot's Handbook of Aeronautical Knowledge instead of lurking on gaming sites if you are professional pilot who does not know this kind of basic stuff.

Just saying, it would be safer for you and your passengers.

JtD	09-14-2012 03:22 PM

Quote:

Originally Posted by bongodriver (Post 460832)

I was eqally insulted by your sarcasm, I don't recall putting my query in any form that called your intelligence in to question.

I wasn't being sarcastic, the plane manuals did not appear to clarify the things for you. With the benefit of hindsight the if clause wasn't necessary, but not meant as an offence in the first place.

Crumpp

09-14-2012 03:26 PM

Quote:

I am simply pionting out that what you said about how to fly a Bf109 is in conflict with what Steinhilper said about how to fly a Bf109

:rolleyes:

But is not in conflict and agrees with what is related in the anecdotes.

If you understood how an adjustable pitch propeller works in conjunction with the engine, you would see that.

It is useless to discuss it with you. Have a nice life, Tagert.

bongodriver

09-14-2012 03:32 PM

Quote:

Originally Posted by JtD (Post 460885)

I wasn't being sarcastic, the plane manuals did not appear to clarify the things for you. With the benefit of hindsight the if clause wasn't necessary, but not meant as an offence in the first place.

Ok, sorry for jumping on you, actually likening you to Crumpp was probably the most insulting thing for which I am most regretfull, I have to admit my mistake was not thinking 10 foot diameter props.....goes to show how your own experience can get you stuck in a rut sometimes, I fly a Stearman with a 7 foot and a bit prop and 1500 rpm is practically idling, the R-670 engine has no reduction drive.

bongodriver

09-14-2012 03:33 PM

Quote:

Originally Posted by Crumpp (Post 460884)

I dont need some walt without a pilots license telling me what I should concentrate on thank you.

:rolleyes:

Crumpp

09-14-2012 03:38 PM

Quote:

P. Ponk Aviation
Propeller Efficiency Calculator

Quote:

To produce maximum thrust at full power your tip speed should fall between .88 and .92 mach. To move between .88 and .92 mach usually takes a change of about 110 to 120 RPM. This of course varies depending on your particular propeller and the temperature.

Quote:

If your tip speed is less than .88 mach you should increase RPM to achieve maximum thrust. If your tip speed is greater than .92 mach you should reduce RPM to achieve maximum thrust. Do not exceed the published operating limitations of your engine or propeller.

Over .92 mach the airflow begins to detach from the propeller which decreases efficiency and dramatically increases noise. To improve performance and public relations you should consider reducing RPM so as to fall within the .88 to .92 mach range. Your propeller will be producing maximum thrust which is good for you, and less noise which is good for all of us.

http://www.pponk.com/HTML%20PAGES/propcalc.html

ACE-OF-ACES

09-14-2012 03:49 PM

Quote:

Originally Posted by Crumpp (Post 460888)

But is not in conflict and agrees with what is related in the anecdotes.

If that is true..

Why get so upset and say I was attacking you?

Brings to mind the old saying..

thou dost protest too much

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