No joke: 248mph Hurricane dh5-20, 230mph Spit... what on earth is going on??

[trademe900]

Ok, Lolsav's post has brought me to some startling findings...I am positive I am seeing clearly but you guys should see this for yourselves. Forgive me if this has been posted but there is definitely not one post i've read this in.

I always thought the Spit 1 and dh5-20 were slower in outright speed than the constant speed propellers. At least on Repka the 2a seems to be slightly faster than the 1 in outright speed on the deck. Well it seems Lolsav is definitely right; that is in fact not the case up higher and there's also another surprise!

17,000 feet:

dh5-20: 248mph (course/low rpm)
rotol 100octane with tit pulled: 220mph (just before engine blows)

Spit 1: 265mph (course/low rpm)
Spit 1a 100oct with full emergency boost: 230mph (just before engine blows)
Spit 2a full emergency boost: 230mph

Please test for yourself folks, I am not seeing things here.

[ATAG_Dutch]

Well, no mate, in a word.

The two speed DeHavilland prop provided a greater top speed than the CSP.
The advantage the CSP gave was in rate of climb, which was deemed more important in a short range interceptor designed to stop high flying bombers.

In fact, from memory (I'll check and come back), the original wooden fixed pitch prop provided even more top speed than the 2-pitch DeHavilland, but there were lots of other factors involved such as all up weight which became progressively heavier. Interestingly though, the DeHavilland prop was the heaviest of the early props, and required a lot of ballast in the rear fuselage in order to maintain the centre of gravity. This was because it was a metal prop, whereas the fixed pitch and surprisingly the CSP props were wooden.

Interesting stuff if you like buying books and that!

[trademe900]

I think you've missed the point dutch... I am talking about in game Spit 1 vs 2a and more to the point... the dh5-20 is faster than the Spit 2a.

[ATAG_Dutch]

Originally Posted by trademe900

I think you've missed the point dutch... I am talking about in game Spit 1 vs 2a and more to the point... the dh5-20 is faster than the Spit 2a.

Oh, sorry me old chum, I probably did (few beers you know )

Yep we all know there are top speed issues with all the models, but the difference between the top speed of the props should be there. The DH prop should be faster on the level than the CSPs. Whether the difference in values is correct is another issue.

I'd have to have a bash at the DH5-20 v IIa myself to see what you're driving at perhaps.

Oh god.....more testing...........great...........

[NZtyphoon]

Spitfire performance comparisons fixed pitch 2 blade v 2 speed v constant speed props:




NB: The wooden ROTOL CSP is almost the same as the type fitted to the Spitfire IIa (N3171 was part of a batch of Spitfire Is in the N3--- series fitted with Rotol CSP and UHF radios and used operationally Feb - May 1940 by 54 and 66 Sqns)





In general the speed differences between various prop types seem to be reasonably well modeled for CLOD.

[Momod]

Just did a quick test, 17000ft with boost and 50% rads
Spit 1 270mph
Spit 1a 240mph
Spit 1a 100oct 240mph (blown engine)
Spit 11a 225mph
Hurri DH5-20 255mph
Hurri mk1 100oct 220mph (blown engine)
Hurri Rotol 245mph
conclusion :- 2 speed prop is faster on both types, 100oct is fragile,

[pstyle]

Originally Posted by trademe900

Spit 1: 260mph (low rpm)
Spit 1a 100oct with full emergency boost: 230mph (just before engine blows)
Spit 2a full emergency boost: 235mph

ta. did you look at the 1a? (the 87 octane version)
Oh, I see now that someone else has added the 1a to this thread.

[trademe900]

So... the 100octane planes are slower and the Hurricane is faster than the Spitfire. I actually couldnt get 50 percent radiator on the 100 octanes as they blew before I got an accurate measurement.

Can I ask what is it they did do right in this 'simulation'?

Ffs...

[ATAG_Dutch]

Morning! Bit more 'compus mentus' here too!

Thanks for posting this Trademe, It's something I hadn't really noticed as being such a marked difference. Something is definately out of whack here by the looks of things, so thanks for posting the thread up.

[ATAG_Snapper]

Great thread with great input from everyone.