PDA

View Full Version : Higher boost versions of Spitfire IX, P51 for late 1944?



Pages : 1 [2]

p1ngu666
01-28-2005, 06:38 AM
well our 100% would be 18lb boost, then W key would raise that to 25lbs

but yeah, use lower power for cruise http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif

MEGILE
01-28-2005, 09:52 AM
http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

OldMan____
01-28-2005, 12:30 PM
Does anyone has info of how long where they capable of runnig at 25lb non stop ? Am I right in supose less time than they did at 18 lbs ?

lrrp22
01-28-2005, 12:58 PM
Nope, exactly the same restrictions at +25 lbs as +18. Five minutes WEP- a restriction which was intended to extend engine life, and not because engine damage (or even overheat) would occur if used more than 5 minutes.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by OldMan____:
Does anyone has info of how long where they capable of runnig at 25lb non stop ? Am I right in supose less time than they did at 18 lbs ? <HR></BLOCKQUOTE>

Kurfurst__
01-29-2005, 04:08 AM
A seperate W key should not be needed, the throttle should be just pushed fully forward, to get +25lbs, like to get 110% on the 109F etc.

Otoh I am not Spitty expert, but I believe it`s wrong for all Spits in the game (I mean the w key). I only know the Spit I had a seperate switch for +12lbs, not the later marks. I think they should just use throttle alone, max. boost was not a kind of special liquid or such on them... It should be just 100% throttle to get +16 and +18 on the Mk V and IX/VIII respectively.

And yes, get the +25lbs IXs in the game if possible. They were contemporaries of the G-14 and A-8.

Oh and +25lbs was appearantly restricted to 5 mins due to engine temperature load.

lrrp22
01-29-2005, 12:15 PM
Kurfurst,

You phrased your response to make it sound like the 5-minute limit was an *additional* restriction imposed on the use of +25 lbs. You know it wasn't, it was exactly the same limit as the +18 lbs limit.

In fact, as hop2002 posted previously, after a 10 minute level run at +18 lbs followed by 5 minutes at +25 lbs, the tested Spitfire's coolant temperature was still below the temperature mandated for Continuous Cruise conditions. That same Spitifre was able to conduct a +25 lbs climnb from 2,000 ft to 32,000 ft *with radiators forced CLOSED* while only slightly exceeding the max permissible temperature at the end of the climb.

So, as I said, the +25 lbs 5-minute limit- like the +18 lbs limit, was implemented to limit general engine wear and tear, and not because of any cooling or detonation issues. Certainly the use of +25 lbs boost reduced the Merlin's life cycle, but it had virtually no effect on the use of higher power settings in combat.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Kurfurst__:

Oh and +25lbs was appearantly restricted to 5 mins due to engine temperature load. <HR></BLOCKQUOTE>

ElAurens
01-30-2005, 06:11 PM
Here is a new little nugget I have discovered this weekend. It seems that both the RAAF in the Pacific, and the RAF and USAAF in North Africa ran their P40Es at 66 to 70 inches of manifold pressure. This gave the V 1710 F3R and F4R engines used at that time between 1745hp and 1780hp depending on temperature and altitude. The documents I have seen state these power levels could be sustained for "extended" periods. Although no exact time is given. This is from a document dated Dec. 12, 1942 from Allison Division to the commander of USAAF Materiel Center.

My host is down so I cannot post the doc. today.

lrrp22
01-30-2005, 10:15 PM
Wow!

I've seen accounts of the RAF running its Allison Mustang I's and II's at similar settings in the ETO. Apparently, they would run them for up to 20 minutes at that boost!

Performance numbers would be very interesting for a 1780 HP P-40. It would probably be 20+ mph/32 kph faster below 14,000 ft. I'm anxious to see those doc's.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by ElAurens:
Here is a new little nugget I have discovered this weekend. It seems that both the RAAF in the Pacific, and the RAF and USAAF in North Africa ran their P40Es at 66 to 70 inches of manifold pressure. This gave the V 1710 F3R and F4R engines used at that time between 1745hp and 1780hp depending on temperature and altitude. The documents I have seen state these power levels could be sustained for "extended" periods. Although no exact time is given. This is from a document dated Dec. 12, 1942 from Allison Division to the commander of USAAF Materiel Center.

My host is down so I cannot post the doc. today. <HR></BLOCKQUOTE>

ElAurens
01-31-2005, 11:06 AM
The copy of the document does not include the charts of dynomometer runs, and the last 2 pages of the 3 are the Allison exec pretty much covering his behind by saying that they cannot warrantee that anything over 60" won't hurt the engines.

http://www.blitzpigs.com/photos/Allison%20Overboost%20doc.jpg

Kurfurst__
01-31-2005, 11:16 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by lrrp22:
In fact, as hop2002 posted previously...., <HR></BLOCKQUOTE>

Hop 2002? That basically means the claims has absolutely no relevance to real life. We all know Hop`s attitude, this one claim was about 'Spitfires should not have any WEP limit, unlike all other planes in the game'. He added some of his own bogus calculations, claiming the temperature should rise only 1-2 degrees after an 3/4 hour at full WEP and closed radiators... LOLOLOL. Typical for Hop2002.

Choose your references more carefully next time.

lrrp22
01-31-2005, 12:26 PM
The "reference" isn't hop22002, Kurfurst, it is the actual RAF test that arrived at these results. Keep your dislike for hop from coloring your objectivity- the fact is that the RAF found no cooling probelems with the use +25 lbs boost.

If you are going to discount the source, then admit that you are discounting the RAF/Rolls Royce's testing establishment, and not a poster on thses boards.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by lrrp22:
In fact, as hop2002 posted previously...., <HR></BLOCKQUOTE>

Hop 2002? That basically means the claims has absolutely no relevance to real life. We all know Hop`s attitude, this one claim was about 'Spitfires should not have any WEP limit, unlike all other planes in the game'. He added some of his own bogus calculations, claiming the temperature should rise only 1-2 degrees after an 3/4 hour at full WEP and closed radiators... LOLOLOL. Typical for Hop2002.

Choose your references more carefully next time. <HR></BLOCKQUOTE>

hop2002
01-31-2005, 01:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>He added some of his own bogus calculations, claiming the temperature should rise only 1-2 degrees after an 3/4 hour at full WEP and closed radiators... LOLOLOL. <HR></BLOCKQUOTE>

Straw man argument.

I've never claimed anything like that Isegrim.

You can see what I actually claimed at http://forums.ubi.com/eve/forums?q=Y&a=tpc&s=400102&f=63110913&m=472102426&p=4

What I said was 46c temperature rise in 3/4 of an hour, with radiators half open (known as "closed" position on the Spitfire, which had 2 settings, fully open and half open)

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> We all know Hop`s attitude, this one claim was about 'Spitfires should not have any WEP limit, unlike all other planes in the game'. <HR></BLOCKQUOTE>

I haven't mentioned much about WEP limits on other aircraft. To know what they were, you need to look at the individual aircraft.

The Spitfire IX should not overheat in level flight for a long time. That's not the case for all aircraft, though. Looking at the figures for the Hurricane II, it was borderline in level flight in temperate conditions after 5 mins, and would overheat before that time under tropical summer conditions.

The Spit IX, however, was "limited" to 5 minutes, which was the guideline figure for almost all RAF fighters.

I've just seen the details for the conversion of the Sabre IIa to IIb. Both engines, despite the IIb running at much higher power, were limited to the same 5 minutes. The Merlins were limited to 5 mins when they ran at 9 lbs boost, still 5 mins when they went up to 12 lbs, then 5 mins at 15 lbs, then 5 mins at 16 lbs, then 5 mins at 18 lbs, then 5 mins at 25 lbs.

The time limit at 25 lbs was exactly the same as at 18 lbs, and indeed was the same as when WEP was first introduced to the Spitfire I at 12 lbs.

This is what a US manual had to say on the subject of time limitations:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>It is often asked what the consequences will be if the 5-minute limit at Take-off Power is exceeded. Another frequent inquiry is how long a period must be allowed after the specified time limit has elapsed until Take-off Power can be used. These questions are difficult to answer, since the time limit specified does not mean that engine damage will occur if the limit is exceeded. Instead, the limit means that the total operating time at high power should be kept to a reasonable minimum in the interest of prolonging engine life. <HR></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>evertheless, it is still the aim of the manufacturer and to the best interest of the pilot to keep within reasonable values the amount of high-power time accumulated in the field. The most satisfactory method for accomplishing this is to establish time limits that will keep pilots constantly aware of the desire to hold high-power periods to the shortest period that the flight plan will allow, so that the total accumulated time and resulting wear can be kept to a minimum. How the time at high power is accumulated is of secondary importance; i.e., it is no worse from the standpoint of engine wear to operate at Take-off Power for one hour straight than it is to operate in twelve 5-minute stretches, provided engine temperatures and pressures are within limits. In fact, the former procedure may even be preferable, as it eliminates temperature cycles which also promote engine wear. Thus if flight conditions occasionally require exceeding time limits, this should not cause concern so long as constant effort is made to keep the over-all time at Take-off Power to the minimum practicable. <HR></BLOCKQUOTE>

Once more, Isegrim, the results from the Spitfire IX cooling trials:

With radiator flaps "closed" or half open:
<pre class="ip-ubbcode-code-pre">
Altitude Suitability

3000ft cruise max
trop 1.12 1.17
temp 1.32 1.36

13500ft
trop 1.16 1.18
temp 1.32 1.32
</pre>

The suitability is given by the formula:

suitability = (permissible coolant temp - standard summer air temp) / (observed coolant temp - observed air temp)

You've seen the formula often enough, Isegrim, and from your reactions (straw man arguments, claiming it doesn't say anything about the coolant temps, etc) I can only assume you don't understand enough maths to work out what it means.

If that's the case, might I suggest you ask someone who does understand maths to help you.

Kurfurst__
02-01-2005, 06:21 AM
The test was done in the wintertime in England.

"What I said was 46c temperature rise in 3/4 of an hour, with radiators half open (known as "closed" position on the Spitfire, which had 2 settings, fully open and half open)"


Facts, Hop claims the above temperature increase, based on his OWN calculations, OWN set of number used.

Fact that the test doesn`t mention any actual temperature values.

Also a fact, that this test was done on Mk IXLF Spitfire serial no JL 165, which Hop 2002 usually displays as a totally non-representative example of the type... all Spitfires, of course, were much-much better than the performance measured on JL 165... Hop likes to pick a report on one plane he claims otherwise unrepresantative, play with the numbers a bit here, a bit more there... and then claims bogus numbers on cooling capacity, mixing his own fiction with reference to an actual report It`s so typical for Hop2002 in his never ending claim campaign about the Spitfire being flawless in every regard. His playing with the radiators terms (renaming "Open" to his own 'half closed') is a result of a correction from Neil Stirling, and the Spitfire`s manual, pointing to that the Spitfire`s radiators were automatic only, and were always "Open" in climb conditions. This little play with terms has importance to Hop, as he wishes to compare climb rates in minimum drag position for the Spitfire to Bf 109 climb rates with moderate drag radiators.. the usual stuff from him.

Still, whenever I ask him to point out where exactly the report points to actual temperatures measured - it`s met with silence, as it is now. The wilds claims are stated again and again though, attempting to convince in the way Goebbels did to the masses.

hop2002
02-01-2005, 07:47 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The test was done in the wintertime in England. <HR></BLOCKQUOTE>

Isegrim, I've shown you the equation used. I've suggested you get help, as your maths is clearly no better than mine.

However, as you persist.

The equation the RAF used adjusts for the actual air temperature used at the time, so it doesn't really matter where or when the test is done.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Facts, Hop claims the above temperature increase, based on his OWN calculations, OWN set of number used. <HR></BLOCKQUOTE>

No, using the RAF's equation, using ASSUMED values for air temperature. The figures I quoted are accurate for the assumed air temperatures.

In other words, if the air temp was 9c at 3000 ft, and the standard air temp was 9c at 3,000ft, then the coolant temp was 94c.

That's the beauty of an equation, it lets you put in different values and get results, which are valid for those values.

The important point, though, is that the RESULT of the equation is the figure the RAF came up with, not me.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Fact that the test doesn`t mention any actual temperature values. <HR></BLOCKQUOTE>

No, it gives the RESULT, not the conditions.

Now, as you can't, or won't, do the equation for yourself, here it is with some more assumed values for air temperature:

Radiator suitability = (allowed coolant temperature - standard summer air temperature) / (observed coolant temperature - observed air temperature)

We know the suitability, because the RAF gives it as 1.32 at 3000ft at standard temperature.

The permitted temperature is given in the test, 125c.

We don't know the actual or standard air temps, so we have to assume them. We don't know the coolant temp, but we can calculate it if we assume values for air temperature.
<pre class="ip-ubbcode-code-pre">

standard air temp 9c, observed 9c
1.32 = 125 - 9
___________
96.8 - 9
Coolant temp = 96.8c


standard air temp 9, observed 0

1.32 = 125 - 9
___________
87.8 - 0
coolant temp = 87.8


standard air temp 20, observed 0

1.32 = 125 - 20
___________
79.5 - 0
coolant temp = 79.5c


Standard air temp 20, observed 20

1.32 = 125 - 20
__________
99.5 - 20
coolant temp = 99.5c


standard air temp 20, observed 30

1.32 = 125 - 20
__________
110 - 30
coolant temp = 110c


standard air temp 20, observed 50

1.32 = 125 - 20
__________
130 - 50
coolant temp = 130c
</pre>

See, to get overheating you have to have extremely high air temperature, and it has to be far higher than the expected temperature*.

50c at 3000 ft would of course be around 55c at sea level, which I think you'll agree is a bit hot for standard temperate summer temperature.

*because the expected temp is already factored in to the result, which we have. What we are doing is trying to work out the conditions from the result.

Tell you what, Isegrim, as you can't, or won't, do the equation yourself, tell me what you think the standard air temperature should be, and the actual air temperature at the time of the test, and I'll tell you what the coolant temp would be.

Once again, for those who haven't seen it, the original cooling test for the Spit IX at 25 lbs:

http://www.onpoi.net/ah/pics/users/282_1090694499_climbcropped.jpg

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Also a fact, that this test was done on Mk IXLF Spitfire serial no JL 165, which Hop 2002 usually displays as a totally non-representative example of the type.. <HR></BLOCKQUOTE>

I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive.

Remember, it's calculated 18 lbs performance? Which you had, the last time I saw you talking about it, switched to saying was simply the result of not factoring in the performance drop from the prop not being able to handle the power.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>His playing with the radiators terms (renaming "Open" to his own 'half closed') <HR></BLOCKQUOTE>

Playing? I'm just clarifying. Here's what the Spitfire cooling report says:

http://www.onpoi.net/ah/pics/users/282_1095182613_radiators.jpg

Here's why I'm clarifying for people.

This is a diagram of the 109 radiator setup:

http://www.onpoi.net/ah/pics/users/282_1107268348_bf109f-1radiator.jpg

As you can see, closed on the 109 means almost totaly closed, and is going to provide little cooling.

Here in contrast is the Spitfire radiator fully open:
http://www.onpoi.net/ah/pics/users/282_1107268540_spitradiator.jpg

and here "closed", which as you can see is still half open:

http://www.onpoi.net/ah/pics/users/282_1107268583_spitradiator3.jpg

Now, fairly obviously, the 109 isn't going to get much cooling with it's radiators closed, because they really are closed, and airflow will be minimal. Equally obviously, the Spit is still going to get a lot of cooling with it's radiators "closed" because they are still half open, and airflow will be substantial.

Kurfurst__
02-01-2005, 01:47 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive. <HR></BLOCKQUOTE>

Typical strawman arguement from Hop 2000.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Remember, it's calculated 18 lbs performance? Which you had, the last time I saw you talking about it, switched to saying was simply the result of not factoring in the performance drop from the prop not being able to handle the power. <HR></BLOCKQUOTE>

Here`s what the RAF`s test in question notes :

"The improvement in climb is not so great as would be expected from a comparison of the relative powers obtained at + 18 lbs. and + 25 lbs. boost, which indicate that the gain should be of the order of 1,100 feet/minute. This is probably due to a decrease of propeller efficiency at the higher powers. A propeller of greater solidity should show an improvement in this respect."

Funnily enoogh, the test results done on the plane match almost 100% two other, similiarly engined real life tests of Spitfires...


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
This is a diagram of the 109 radiator setup:

http://www.onpoi.net/ah/pics/users/282_1107268348_bf109f-1radiator.jpg
<HR></BLOCKQUOTE>

This is a hand made drawing with absolutely nothing noted on it about what it shows, and I seriously doubt it would even a correct scale one.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
As you can see, closed on the 109 means almost totaly closed, and is going to provide little cooling. <HR></BLOCKQUOTE>

No, you don`t know the 109s radiator operation. It was automatically controlled by thermostat, or manually by the pilot to any value between 0 and 400m. 243mm, 87mm, 350mm etc. Not just a two-position (full open/closed) as on the Spitfire.

All German climb tests otherwise note that, as opposed to what you claim, the 'totally closed' radiators on the 109 can keep the engine very cool at higher altitudes.

This picture shows the radiators flaps 'half open' by Hop`s reworked nomenclature. Clearly, the exit area is massively larger than the Spitfire`s in full Open position.

http://109lair.hobbyvista.com/techref/systems/cooling/f_hrabak.jpg


http://www.onpoi.net/ah/pics/users/282_1107268540_spitradiator.jpg


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Now, fairly obviously, the 109 isn't going to get much cooling with it's radiators closed, because they really are closed, and airflow will be minimal. <HR></BLOCKQUOTE>

Now, fairly obviously, as the 109 had larger exit area when the flaps were 'closed' in climbs, as you call it, than the Spitfire. One just have to do the maths...


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
Equally obviously, the Spit is still going to get a lot of cooling with it's radiators "closed" because they are still half open, and airflow will be substantial.
<HR></BLOCKQUOTE>

Equally wrong, as the Spit is still going to get a lot LESS of cooling with it's radiators "closed" because they are a much smaller area than the Messerscmitt`s at what you re-named 'Half open'. However, the 109 needs a lot less air for cooling, and lot less exit area is sufficient. The radiators can be closed more tightly, drag will decrease, climb rate will increase. The Spitfire couldn`t close any better than a semi-open position.. in fact, the pilot could not operate the radiator flaps at all. They opened out as soon as airlow slowed down - ie. in climbs.. The 109 pilot could gain a lot more from closing the radiator flaps, which had much greater area to start with, could be operated manually.

This was actually tried, the radiators were closed in some real life tests done on 109s, resulting in 4800 feet/min climb rate at 1.3ata, which is just military rating (Spitfires with open radiators needed +600 HP, special 150 grade fuel, and use of +25lbs boost to exceed this rate of climb, not until 1944).

Hop just renamed the nomenclature in order to hide this away.

p1ngu666
02-01-2005, 03:26 PM
http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif u guys

i think u are being mean to this man
http://www.mennonitechurch.ca/img/witness/wwow/large/Straw%20Man%202.jpg

http://forums.ubi.com/images/smilies/16x16_smiley-sad.gif

ElAurens
02-01-2005, 03:33 PM
http://www.icon.co.za/~pauljnr/radiator.jpg

The only radiator that matters.

Be sure.

hop2002
02-01-2005, 05:12 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive.


Typical strawman arguement from Hop 2000.

<HR></BLOCKQUOTE>

Isegrim, do you know what a straw man argument is? Or are you, as is you're normal behaviour, just accusing me of doing what I've just pointed out you have been doing?

A straw man argument is where you present a distorted version of someone's position, and attack that.

For example,

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>He added some of his own bogus calculations, claiming the temperature should rise only 1-2 degrees after an 3/4 hour at full WEP and closed radiators <HR></BLOCKQUOTE>

When my actual position was:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Ignoring that, you get a 1c coolant temp rise per minute, from 89c at cruise.

The maximum allowable coolant temp in real life was 135c. That would take 46 minutes to reach, even ignoring the fact that as the temp gets higher, the coolant transfers more heat to the air. <HR></BLOCKQUOTE>

Do you see the principle? I say 1 degree temp rise a minute, or 46c in 3/4 hour, you attack my position, which you claim is "1 - 2 degrees in 3/4 hour".

That's a straw man argument.

Now, you've just accused me of a straw man argument for saying:

"I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive."

For it to be a straw man argument, that would have to be misrepresenting what you've claimed.

But it's not. That's exactly what you've claimed.

Here, for examplee:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The 'normal Spitfire IX LF' JL 165 is slower than the Spitfire PROTOTYPES WITH EXPERIMENTAL AIRSCREWS which Hop is desperate to sell here? <HR></BLOCKQUOTE>
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Well it still shows a 'normal spitifre IX LF' as the record says, <HR></BLOCKQUOTE>
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Well that`s the only data me, and also what you know about a serial production Spitfire IX LF <HR></BLOCKQUOTE>
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Now, since JL 165 is the only serially built and tested Mk LF IX we know, that is what I will use for comparison, <HR></BLOCKQUOTE>

All from http://forums.ubi.com/eve/forums?a=tpc&s=400102&f=63110913&m=541109106&r=519102506#519102506

There are plenty more, just search for your posts with "jl 165"

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>This is a hand made drawing with absolutely nothing noted on it about what it shows, and I seriously doubt it would even a correct scale one <HR></BLOCKQUOTE>

Scale doesn't matter, it's just a diagram showing the layout of the 109s radiator. It shows quite clearly that when they are closed, they have very little gap.

Life I said, my describing the Spit's radiators as "half open" is just to clarify, lest people think that "closed" on the Spitfire means the same as "closed" on the 109.

Kurfurst__
02-02-2005, 07:24 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by hop2002:
Isegrim, do you know what a straw man argument is? Or are you, as is you're normal behaviour, just accusing me of doing what I've just pointed out you _have_ been doing?

A straw man argument is where you present a distorted version of someone's position, and attack that.

Now, you've just accused me of a straw man argument for saying:

"I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive."

For it to be a straw man argument, that would have to be misrepresenting what you've claimed. <HR></BLOCKQUOTE>

Then it`s correct to describe it as a strawman arguement.

Ie. Hop`s statement :
"I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive."

My statements :
_"The 'normal Spitfire IX LF' JL 165 is slower than the Spitfire PROTOTYPES WITH EXPERIMENTAL AIRSCREWS which Hop is desperate to sell here?"_

Thus I claim the JL 165 was normal, the one Hop was using a prototype.
No mentioning if +18 lbs boost (Hop`s distortion). No mention of JL 165 being the "most representative" (Hop`s distortion).

_"Well it still shows a 'normal spitifre IX LF' as the record says,"_

Thus I claim again the JL 165 was normal.
No mentioning if +18 lbs boost (Hop`s distortion). No mention of JL 165 being the "most representative" (Hop`s distortion).

_"Well that`s the only data (to) me, and also what you know about a serial production Spitfire IX LF"
"Now, since JL 165 is the only serially built and tested Mk LF IX we know, that is what I will use for comparison."_

Thus I claim again the JL 165 was again the only detailed serial production Spitfire IX LF we know.
No mentioning if +18 lbs boost (Hop`s distortion). No mention of JL 165 being the "most representative" (Hop`s distortion).

If anyone has doubts if JL 165 was a standard Spitfire, should read the preface of the test :

"Spitfire IX JL.165
(Merlin 66)
Trials at +25 lb/sq.inch boost
with Rotol 4 blade propeller

SUMMARY

..................Performance trials and a brief assessment of handling characteristics have been completed on _a standard Spitfire IX with Merlin 66 engine,_ adjusted for maximum boost of +25 lb/sq.inch. 150 grade fuel to Specification RDE/F/253 was used through all tests. "


Let`s recall Hop`s criteria for a straw man arguement :

"For it to be a straw man argument, that would have to be misrepresenting what you've claimed."

As shown above, Hop had misrepresented what I claimed completely. Therefore he was using the strawman arguement. He also repeated misrepresenting the nature of the JL 165 tests.
From my past experiences, it`s rather typical for Hop2002 to attack his opponent`s persons, rather than his facts, as Hop 2002 is usually short of facts, but overloaded with claims.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>He added some of his own bogus calculations, claiming the temperature should rise only 1-2 degrees after an 3/4 hour at full WEP and closed radiators



Now, you've just accused me of a straw man argument for saying:

"I claimed it's performance at 18 lbs was totally non representitive, when you tried to claim it as the most representitive."

For it to be a straw man argument, that would have to be misrepresenting what you've claimed.


[QUOTE]Scale doesn't matter, it's just a diagram showing the layout of the 109s radiator. It shows quite clearly that when they are closed, they have very little gap. <HR></BLOCKQUOTE>

Like I said, appearantly you don`t quite understand how the 109 radiators worked. They could be at any intervene position between fully open and fully closed. They did not work like the Spit`s radiators.
The drawing hard prooves anything, except for two possible positions out of the infinitive variatons on the 109 radiator positions.


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Life I said, my describing the Spit's radiators as "half open" is just to clarify, lest people think that "closed" on the Spitfire means the same as "closed" on the 109. <HR></BLOCKQUOTE>

Not exactly, your goal is to make people think Closed radiators ("half open") on the Spit are comparable with ROC data done on 109s with apprx. half open radiators, when it is not for the following reasons.

The trick is to use minimum drag ROC figures for the Spit to get exaggrevated figures, as the normal figures fell behind that of the 109, shown by JL 165 tests, which you attack for the reason pointed out already.

Spit pilot had no manual control over the radiator flaps. He could not close them if he wished, the flaps were operated by thermostat which opened them fully in climbs, where the airflow was minimal (Spitfires climbed at very slow airspeeds), to maintain cooling capacity. For this reason, 99% of the British climb figures show radiator flaps in open position, thought as the most representive during climbs.

A 109 pilot could let the thermostat to fine-set the position of the radiator according to the needs, or adjust them manual and lock in that position.

The radiator flaps were 854mm wide, and opened ca220mm wide during climbs on the 109s ("half open"), that is what 109 climb curves represent. That`s an exit area of 2.02 sq. ft per radiator, compared to 1.47 sq. ft and 1.67 sq. ft on the Spitfire (Open). When the Spit rads were closed, exit area was 0.83/0.83. This latter is "Closed", or Hop`s "Half Closed".

http://www.onpoi.net/ah/pics/users/282_1095182613_radiators.jpg

Hop usually compares ROC of the Spit and 109 when the 109 flowns at ca. half-closed, and the Spit with his own "Half closed" (officially : Closed). In other words, he compares the Spitfire with the least possible drag compared to

Total exit areas of radiator flaps in Hop`s comparison between 109 and Spitfire rate of climb :
----------------------------------------------------
Spitfire : 0.83+0.83 = 1.66 sq. ft ("Closed"), Hop`s 'half closed'.
109 : 2.02+2.02 = 4.04 sq. ft ("Steigflugstellung"), German standard.

Hop is comparing the Spitfire with the radiators set to 2.4 times as smaller exit area to inflate it`s climb rate compared to 109 test standards.

British standard was, quite naturally, "Open" radiators, for a total rad. exit area of 3.14 sq. ft.
So even if we compare British standard vs. German standard directly, already the Spitfire`s radiator drag is only 3/4 in comparison to what the 109 ROC figures represent. Thus in comparing like with the like, 109 ROC figures need to be slightly increased to get the ROC at the same radiator exit area.

Yet Hop claims that even the minimum 1.66 sq. ft exit area was sufficient for the SpitIXLF at near 2000 HP, yet the 109 could not afford at all to close the radiators to any less than 4.04 sq.ft...

Aaron_GT
02-02-2005, 09:28 AM
"Hop is comparing the Spitfire with the radiators set to 2.4 times as smaller exit area to inflate it`s climb rate compared to 109 test standards"

Since climb is done at relatively low speed and drag is proportional to speed squared the extra drag will be small and not particularly significant to overall climb rates. What will be more significant is the ability (or otherwise) of the engine to maintain a certain power level.

firedog70
02-02-2005, 11:00 AM
Hello Gentlemen,
Do you mind if I interject into your conversation as a first time poster?
Something that has not been mentioned is the Spitfires radiators were desinged with the Meridith effect. Although the Meridith design has been highly touted with the design of the
P-51 radiator, the Spitfire also used the Meridith design.
The Meridith design would have a direct influence in radiator size, radiator exit area, flap position, drag, etc..
The Spit's radiators closed, in the half open position, is most certainly influenced by the Meridith design.
I'm not sure how you can make direct comparisons between these two radiator designs without considering the Meridith design of the Spit's radiators.

Bull_dog_
02-02-2005, 08:16 PM
I could be wrong about this...but I seem to remember that the difference with the Mustang's design and others was how it automatically operated to optimize flow...that is what set it apart. Other radiators were based on the same principle but the apreture was not automatically regulated...for example the spit was open, closed or some setting between which did not optimize the effect. The Mustang's more graduated aperature is what lead to the low drag efficiency.

Kurfurst__
02-03-2005, 11:17 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Aaron_GT:
Since climb is done at relatively low speed and drag is proportional to speed squared the extra drag will be small and not particularly significant to overall climb rates. What will be more significant is the ability (or otherwise) of the engine to maintain a certain power level. <HR></BLOCKQUOTE>

Radiators do effect climb rate by a rather significant margin, Aaron. Spitfire climb tests show iirc some 5-700 fpm difference between "Open" and "Closed". In case of the 109, I have exact data for the drag increase, ca. 50 kph loss between fully open and fully closed at 500-550 kph speed range. I`d love if someone could convert this to climb rate difference at climb speeds... OTOH, a Finn climb test is known for a 109G-2, on which the 1st 2000m climb was done at higher speed than usual, resulting the thermostat keeping the radiator flaps closed for some time - result, max. 4900 fpm climb rate at 1.3ata boost military power.. and because of the greater drag difference when closed/open between the 109 and Spit, I am absolutely certain the gain is more on the 109.


@firedog70


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Something that has not been mentioned is the Spitfires radiators were desinged with the Meridith effect. Although the Meridith design has been highly touted with the design of the
P-51 radiator, the Spitfire also used the Meridith design.
...
I'm not sure how you can make direct comparisons between these two radiator designs without considering the Meridith design of the Spit's radiators. <HR></BLOCKQUOTE>

Firedog, it`s true the Spitfire also employed the Meredith effect, though it hardly was the first, or the best in this regard. In fact of all premiere ww2 fighters, the Spit`s radiator design was the least suited to take advantage of it. The Meredith effect is based on using the thrust of warm air projected out at high density behind the radiator, ie. the difference of pressure between the intake and exit area. Optimally, this means large entry and small exit area; the Spit had basically a box shaped radiator, fixed area, large intake, large exit area, thus not very well suited.. The 109 also took advantage of it, a much better radiator design in this regard, simialir to that employed on the Mustang in working principle : thermostatically controlled inlet and outlet flaps, the entry being small, adjusted to needs, the air gets through the radiators and heats up, the surplus air is driven above the radiator to minimize interference. As the air heats up, it expands behind the radiator and projected out at greater pressure by the adjustable radiator flaps, which are almost closed during high speed : less volume -&gt; greater pressure, more thrust gain. The Mustang`s design is essentially the same, just more aerodynamically refined, at the cost of increased vulnerability of the system.
But note also many other fighters, Yaks etc. also took advantage of the Meredith effect.


@Bull_dog

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
I could be wrong about this...but I seem to remember that the difference with the Mustang's design and others was how it automatically operated to optimize flow...that is what set it apart. Other radiators were based on the same principle but the apreture was not automatically regulated...for example the spit was open, closed or some setting between which did not optimize the effect. The Mustang's more graduated aperature is what lead to the low drag efficiency. <HR></BLOCKQUOTE>

That`s true for the Spitfire. MkI through Mk V had manually controlled rad flaps, no automatic control. MkIX onwards they had thermostat control, no manual, but the former was rather simply, keeping the rads closed until a given temperature was reached, then opening them fully... some workload saved for the pilot, but not efficient.

The 109 thermostat worked automatically to maintain the coolant temp at ca. 85 degrees optimum. (This is optimum for engine operation, but the engine was allowed to run at 115 degrees for 10 mins time, and 105 degrees for unlimited time - so plenty of 'reserves' if he wished for lesser drag during combat). gradully opening and closing both inlet and outlet flaps to optimize airflow required for proper cooling - keeping an optimum balance between drag and cooling requirements. Basically same as the Mustang. The oil cooler flaps was fully automatic, thermostat controlled; both systems hydraulically operated. In event of failure, or wish for manual control, the pilot could disengage the coolant flap automatism and fully close, or fully open the radiators, or ANY intermediate position. In case of damage, either of the two coolant radiators could be shut off from the circle to prevent loss of coolant, and permitting return to base.

LBR_Rommel
02-07-2005, 06:50 AM
http://www.luftwaffebrasil.com/xfiles.jpg

Aaron_GT
02-07-2005, 07:29 AM
Kurfurst wrote:
"Radiators do effect climb rate by a rather significant margin, Aaron. Spitfire climb tests show iirc some 5-700 fpm difference between "Open" and "Closed". In case of the 109, I have exact data for the drag increase, ca. 50 kph loss between fully open and fully closed at 500-550 kph speed range."

I am surprised at the level of the effect (but if those figures are accurate, then fair enough).

A 50 km/h drop at 500 km/h should equate to about 1/4 of that at a typical climb speed of 250 km/h. At 250km/h a 4000 fpm climb rate means a climb angle of 17 degrees. You'd have to reduce the climb angle to 15 degrees to drop the climb rate by 500 fpm at 244 km/h, or a 14.5 degree climb angle at 250 km/h.

In the Spitfire tests were the tests with radiators open or closed done at constant climb angle, constant climb speed, or the best combination thereof for each condition (open or closed radiators)? Also was the boost level for each fixed or was the highest boost that didn't cause an overheat for each plane used. Over how long were the climbs sustained?

HayateAce
02-09-2005, 10:46 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by LBR_Rommel:
http://www.luftwaffebrasil.com/xfiles.jpg <HR></BLOCKQUOTE>

http://www.bc.edu/bc_org/svp/st_org/heightsmen/images/false.jpg