Electro Power for small aircraft and drones

[aleatorylamp]

Hello Ivan,
I was referring to the one .air file you attached to post #114. I have downloaded it three times already, just to stop the confusion that I find myself in, but the confusion is still there..

Although that .zip is called NemesisNXT-Air.zip, it contains one .air file called HubrsHXT.air, which handles "not so good but not horrible either" as you say. There is no .air file called Nemesis NXT.air attached.

The HubrsHXT.air contains my old parameters, some of which were erroneous:
>It has Cylinder Displacement 90.15 instead of 90.25 (I know it is not an important mistake on my part, but it is still in), >Compression Ratio 8.7 (I know this IS an important one, and it is still in - I had it at 7.3 already),
>Boost gain 2.65, (This is what sets Critical altitude, at least on my computer),
>Critical altitude 17000 (I found this entry not to make any difference, but OK, I´ll put in 16500 from now on)
>Pitch range at 21.5-51.5 degrees, (I had changed it to 20-55 after you said it was creating problems for the governor, but it is still in there).

Then, I looked through the thread already 3 times, and prior to the above, the only other .air file you have ever attached, was to your post #74 (which also contained the Warhawk model you were using as your proof of concept plane): Hubris-20241101KPW.zip, containing 2 .air files: Hubris.air, and Hawk87W.air (the original Warhawk .air file).
This Hubris.air file already contains most of the corrected parameters from which I corrected my erroneous ones.
>Cylinder Displacement 90.25 (I corrected mine to that)
>Compression Ratio 7.3 (so I changed mine to that)
>Boost gain 2.65 (I already had that)
>Critical altitude 13500 (this has changed in the meantime)
>Pitch range at 20-55 degrees, (I corrected mine to that)

Anyway... Perhaps this can illustrate why I am confused.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,
Much past my bedtime here, so I will keep message short.
Just making another attempt to upload the NemesisNXT.air file.

- Ivan.

 

[aleatorylamp]

Hi Ivan,
OK, no wonder my head was already reeling trying to get around what you kept saying. So, now I more or less know what to do.

Update: You said "For some reason, you had gotten it in your mind that the critical altitude should be 18,000 Feet and I am tired of arguing with you." Lowering Boost Bain to below 2.65, e.g. 2.57, by far gave me insufficient power further up, but with B.G. 2.65 I never had Critical Altitude at 18000 ft - I never argued about it, and you never mentioned how much you meant it to be lowered, although I asked.
I lowered it from 2.657 to 2.65, and you made no comment, so I thought it was OK.
Update 2: Anyway, in absolutely all speed vs. altitude tests I did with B.G. 2.65, performance always, without exception, fell after 17500 ft - that´s why I always put in the test reading for 18000 ft, which always, without exception showed less power and less speed than at 17500ft.
So does my computer compute Critical altitude differently from yours?
With B.G. at 2.57 there was always an unwanted peak lower down, around 16000 ft perhaps, which didn´t happen at B.G. at 2.65.

For Nemesis.air you said it "was a propeller tune up for your Nemesis NXT version. The handling on that one is just plain awful. It is wrong in so many places, I am not even sure where to start. I don't believe it is realistic to fly it outside autopilot which is why I encouraged you to do a lot more test and tune cycles."

It seems to me that other than for the tuned propeller tables, this .air file should be be scrapped. Best would be to have its new propeller tables inside the new HubsHXT.air file, but for the moment this combination reduces Hp to 337 at S.L., and correcting this to 351 Hp, causes speed at 17500 ft to be 461 mph. I´ll have to see how I can do this better. If I can´t, I´ll have to keep the Hubris HXT and the Nemesis NXT separate.

Update: So.... the awaited results:
HubrsHXT .air file as you attached it: Boost Gain still at 2.65. Maybe wrong still?
500 ft: 385.4 mph, 351 Hp, 39.5 Hg, 37.9 pitch ------ Speed OK?
1500 ft: 409.3 mph, 370 Hp, 39.5 Hg, 40.5 pitch ------ Speed OK?
17500 ft: 404.0 mph, 421 Hp, 39.5 Hg, 45.2 pitch ----- Speed fine, power too high.

HubrsHXT .air file combined with new Nemesis NXT propeller tables and power corrected to 351 Hp at S.L. and other entries corrected. Boost Gain still at 2.65. Maybe wrong still?
500 ft: 374 mph, 351 Hp, 39.5 Hg, 38.4 pitch ----- Speed OK?
1500 ft: 407 mph, 370 Hp, 39.5 Hg, 41.2 pitch ----- Speed OK?
17500 ft: 461.5 mph, 419 Hp, 39.5 Hg, 46 pitch ----- Much too fast, Power too high.
>>>>>A possible good next step will be to try Boost Gain at 2.56 like in your new Nemesis NXT .air file.

Nemesis NXT: New .air file as is. (Boost Gain at 2.56). Everything is too fast.
500 ft: 395.4 mph, 352 Hp, 39.5 Hg, 39.9 pitch ------ too fast.
1500 ft: 416.3 mph, 370 Hp, 39.5 Hg, 41.5 pitch ------ too fast.
17500 ft: 465 mph, 400 Hp, 39.5 Hg, 45.7 pitch, 38.1 Hg ----- much too fast.

Nemesis NXT: New .air file, (Boost Gain at 2.56) adjusting lower Cd0 to get slower at 17500 ft. However, too slow lower down.
500 ft: 363.8 mph, 352 Hp, 39.5 Hg, 37.6 pitch ------- rather slow
1500 ft: 392 mph, 370 Hp, 39.5 Hg, 40.8 pitch ------- much too slow
17500 ft: 445 mph, 400 Hp, 39.5 Hg, 45.1 pitch , 38.1 Hg ----- a bit OK.

Well... Why easy if it can also be done complicated.... indeed.

OK, then, sleep well, and have a nice breakfast after.
Cheers,
Stephan

 

[aleatorylamp]

Hello Ivan,
Just a short note about having the lower Boost Gain at 2.56:
Power/speed vs altitude tests for HubrsHXT .air file and HubrsHXT .air file which combined the new Nemesis Propeller tables, showed an unwanted peak at 16000 and 16500 ft. Then, power and speed started going down at 17000 ft. and it was noticeably lower at 17500 ft.
Hence my preference for Boost Gain values of 2.65.
A possible next step could be trying out using Boost Gain values of 2.65 in the Nemesis NXT .air file, with and/or without adjusting Cd0.
All in good fun,
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,
I think there are a lot of things that you are not understanding here.
It all DOES sort of make sense if you break down the pieces by themselves.

Regarding Boost Gain:
You want me to give you a Supercharger Boost number that will correspond to a target Critical Altitude for your Nemesis NXT Air file.
I don't believe that is possible. The reason why is because I believe the Supercharger Boost is only ONE factor that affects critical altitude. I believe there are a bunch of other engine parameters that also affect critical altitude. The engine parameters between Hubris and Nemesis are different enough that what works for one may not work for the other.

I also don't believe you know the critical altitude of your NXT as precisely as you should. Note that I am telling you the Hubris critical altitude to within 100 feet. The way that I am doing this is finding the last altitude at which it can maintain Sea Level Manifold Pressure and then setting the autopilot into a slow / moderate climb and observing engine power and manifold pressure.
You will find you can tune very precisely this way.

Regarding Swapping Propeller Tables:
You commented that swapping propeller tables reduced low level engine power. This should NOT happen. If it happened, then it means you accidentally broke something else. Don't tune more than one thing at a time unless you REALLY know what you are doing. So many things are inter related that you can create some really unpredictable side effects.
Another thing worth observing is that the Hubris and Nemesis use different sized propellers. Two inches does not sound like much, but it makes a difference for power coefficients, pitch angles selected, advance ratios, and where you end up.
Remember, if there is a problem, look at where you fall in the advance ratio axis and compare it to where the donor aircraft was.

Regarding Critical Altitudes and Maximum Speed Peaks:
I try to keep the critical altitude a few hundred feet lower because it tends to lower the horsepower peak. I figure if there is a difference of 1-2 MPH between Critical Altitude and the Target Altitude, it is of no great consequence. This part is also quite unpredictable because it depends on how the propeller pitch curves, advance ratios and increasing speed and engine power changes all roll up. If you happen to be in a stable part of the propeller graph, it may be 1,000 Feet or more without any noticeable difference. If you happen to be in other parts, you may notice performance differences with just 100-200 Feet. It is hard to tell without trying it out.

In your screenshot from AF99, you did not show any grid lines, so it wasn't possible to tell where the CoG is on your model.
Note that in the profile image I posted, I put a Big Black Dot where I assumed the CoG was and everything was scaled from there.
I suspect if you did the same, you may find some values such as in engine locations that are not quite right.

Hope this makes sense.
- Ivan.

 

[aleatorylamp]

Hi Ivan,
Thank you very much for your explanations - they do make sense, and I´ll study them closely.
I was trying to keep the power peak close to critical altitude, and it never went beyond that.
As the only speed reference we have for the N777XT is the fastest speed it achieved was at 17500 ft, I assumed that this was the critical altitude, after which power and speed should decline.
Please find Attached a screenshot of the AF99 CoG.
The .air file has an 8 inch forward shift of the centre of lift, which I changed to zero.
Regarding switching propeller tables, I think the problem is the difference in the engine torque graph between the two planes, and that the new HubrsHXT .air file has to be corrected again to the lower compression ratio, so I still have to figure that out.

Update: Finally swapping propeller tables worked! The torque graph and Cd0 were different on the model, so they needed compensating.
I lowered Boost Gain to 2.63, and found a little improvement. There is a speed peak at 17500 ft, and a power peak at 17000 ft which looks reasonable. Below and above this, performance is lower.
Adjusting Cd0, depending on which reference altitudes are focused on, there is a choice, of course. Where to have it more or less right, and where to allow it to be rather slow or fast. A certain balance perhaps is as follows:

500 ft, 368 mph 351 Hp 39.5 Hg, 37.9 pitch << Increasing speed here increases speed considerably higher up.
5500 ft, 401.7 mph, 370 hp, 39.5 Hg, 41.0 pitch << trying for more speed here, gives more further down but also further up.
17500 ft, 455.1 mph, 415 mph 39.2 Hg, 45.7 pitch << lowering speed here, considerably reduces thing further down.

I was interested to see how AirWrench did things with its ocean wave shaped perpetumobile efficiency graphs, and it seems to manage to keep the performance curve a bit more within desired limits, (assigning 2.631 Boost Gain on its own accord), with the user setting Cd0 (I chose 19). The result is in an altogether smoother progression between 16000 ft and 18000 ft, with a 440.4 mph and 422 Hp peak at 17500 ft with 422 Hp. Then, at 5500 ft it looks OK with 405.6 mph and 384 hp, and at 500 ft, we get 384.7 mph with 368 hp.

Cheers, and thanks again...
Aleatory lamp

 

[Ivan]

Hello Aleatorylamp,
At this point, I really don't know what you are doing because what you are describing has so many faults I am not sure where to begin. It is also sounding to me like I am being not very nice to you and we both can remember how that turned out a couple years back with the Airacobra projects being worked in parallel.

First of all, I believe you are messing with way too many parts of the Air file when you "Swap a Propeller". There is NOTHING in that process that should affect engine power, torque, supercharger boost or anything engine performance related except perhaps idle speed because of a higher or lower drag of the new propeller. If you are experiencing those other changes, you are doing something terribly wrong.
As for compression ratio, The Hubris HXT that I developed NEVER had a compression ratio other than 7.30:1. The Hubris version you sent me, I simply didn't use for a while and when I did, I renamed it to NemesisNXT.air. If the "Hubris Air file" is something you got from me, it would not have had anything other than a 7.30:1 compression.

If I remember correctly, the Center of Lift parameter was something we experimented with back with the Airacobra. I finally figured out that the parameter really didn't do anything. I believe it is a remnant from FS98.

How did you determine the CoG? Where are most of the weights on this aircraft?
Did you notice that your engine location is not in agreement with your CoG in the model?
The Air file says 65 inches. The Model says 77 inches. This is an estimate from your AF99 profile drawing.
Something similar about the cockpit POV can also be determined in seconds from the AF99 drawing.

I believe I have already commented on how you are really working with two different aircraft but trying to use one flight model to do everything.
Go back and look at Post #120 to see why this does not make sense.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Your post #114 has attached NemesisNXT-AIR.zip, and inside is HubrsHXT.air. If you look inside, you will see it still has my initial mistakes in it:
90.15 Cyl. displacement, 8.7 Compression Ratio, and 21.5-51.5 propeller pitch range. You had also tweaked the propeller efficiency graph table as best as possible, I believe. Please see the attached screenshot, which shows where my original mistakes are.

Then, in the NemesisNXT.air you attached the next day, you had further improved the propeller efficiency graph, and it no longer contained my mistakes, but you commented the handling was awful, so I wanted to use the improved NemesisNXT efficiency graph tables in the new HubrsHXT.air version.

I proceeded to correct my mistakes in it and swapped propellers. Testing the plane, I saw that Hp at 500 ft had dropped from 351 Hp to 334 Hp, and to get it up again, I reduced the friction graph until I got 351 Hp. I also tried out different lower Boost Gain values and different Cd0 values to see what fit best, in order to recover the performance the plane had with HubrsHXT .air file with the mistakes.

You mention "First of all, I believe you are messing with way too many parts of the Air file when you "Swap a Propeller"."
It´s not the "swap propeller" that makes it necessary to be messing with too many parts of the .air file. It is that my initial mistakes were still in that .air file and needed corrections, one of which caused a drop in Hp, and that had to be compensated.

Just to be sure, I repeated the process of swapping propeller tables just now, without correcting my mistakes, and the exchanged propeller table works fine. Only after correcting compression ratio from 8.7 to 7.3 did Hp go down.

Anyway, this is all getting too tiring for me. The rest are all minor details that won´t be hard to correct.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,
I have been trying to figure out that zip file myself because the flash drive I was pulling from doesn't even have your HubrsHXT (no I)
on it. I tried to attach a simple Air file and it looked like it went but the result was that it actually attached a ZIP file from some place.
I know I did not create that zip because the only ZIP utility I have on this laptop is 7zip and I did not figure out how to use it until the next day.

We work in such different manners that it is frustrating for both of us. I don't believe there is anything particularly difficult about this Air file as long as you figure out what is realistic and reasonable to simulate. I have given my advice and you choose to do something a bit different, so I am not sure there is anything good I can do anymore.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
So... since last Wednesday I´ve been working on a mistakenly sent .air file one after all. I had asked twice if it was the correct one you were sending.
You had also said you were sending two .air files, the second one with a further improved propeller table but awful handling, which came the next day without further comment. I discarded that one after only pulling out the propeller table for use with the first one which you had said wasn´t too good or too bad to fly, but I didn´t know had been mistakenly sent.

It would have been convenient to tell me as soon as you realized the first one was a mistake (anyone can send something by mistake), as it would have spared us quite a few days of cross-purpose messaging.

A frustrating waste of time and effort, although some of the content has been useful, unrelated to the issue in question. Also, that I do things a bit differently should not really be a problem here.

Possibly, what I´ll do next is try out the second one and maybe further try to improve it.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,
My apologies for the outcome but there are a bunch of facts you are conveniently ignoring here.
First of all, I never asked you to send me any HubrsHXT Air file or even model.
Next, I never use any propeller tables generated by you for obvious reasons. The Hubris Air file I generated was based on a P-40N as I had mentioned before. It has never had anything but P-40N derived propeller tables. You have seen the efficiency graph, you should be able to recognize what you got as something I didn't create.
If you get an Air file from me and it has one of your sets of modified propeller tables, it should be VERY obvious very quickly (like in about 5 minutes) and discarded.
I did send you a Hubris Air file, but it was before the minor correction to the efficiency graph to cure an interpolation problem and THAT was the one I thought you were asking about.

I still have no idea how your HubrsHXT.air file got into a Zip file because I was only trying to upload an un zipped Air File from a flash drive and there was only one on the root directory of that drive. There isn't a HubrsHXT.air file in the root directory there.
I could make a suggestion, but I don't want there to be any further misunderstandings, so proceed as you will.

Oh well, need to get prepared for the morning. Lots of work to do. Alarm just went off, so not on my own time any more.
- Ivan.

 

[aleatorylamp]

Hi Ivan,

Apologies accepted, and I guess it was quite stupid of me to work on my own erroneous file again, because in effect, I did quite soon recognize the efficiency graph, but I thought that there was a reason, some improvement tweaks in the .air file, to send it... because why else would you send me back my own .air file? At the end it was all a misunderstanding, and we can laugh about it now!

Well, I checked performance vs altitude for the Nemesis NXT .air file, and a similar thing happens as with the last one I managed to fix and try out.
I get to choose where I want speeds right: With 440 mph at 17500 ft, I hardly get enough speed lower down. If I want it correct at 500 ft and 5500ft, then it is way to fast at 17500 ft. the reason being that there is a 71-86 mph difference between S.L. and Critical altitude, depending on chosen Cd0.
Then, Boost Gain at 2.56 gives a power+speed peak at about 16500 ft, and maintains the speed peak at 17000 ft, after which it starts falling.

AirWrench is less extreme, with only 56 mph difference between S.L. and C.A.
Perhaps it´s worth investigating how it gets there... due to its ocean wave shaped efficiency graph perhaps?
I´ll see what I can find.

OK then,
Cheers for now.
Aleatorylamp

 

[aleatorylamp]

Hi Ivan,
As you already said, what I was trying to do, won´t work, as it really is two different planes, so I separated the N333XT from the N777XT.

Sea-Level speed data is not available, and of the numerous available engine certificates, none is for a TIO-450-NXT engine, let alone for the two different turbochargers. Similar engines´ manifold pressure vs altitude tables do not coincide for the required engine powers, and also, the aircraft manufacturer refuses to disclose any of the info.

So, I separated them into the two .air files based on a single point of reference each:
> N777XT, with the known top speed of 440 mph at 17500 ft.
> N333XT, with the only useful known straight-line top speed of 435 mph at 5500 ft.

AirWrench proved of little assitance, as at this point I don´t intend to use the perpetumobile Efficiency tables and I don´t know how to stop the Autopilot porpoising anyway. However, it gave me the 1.835642 Boost Gain it assigned for N333XT´s race-course critical altitude of 5500 ft.

The two separate FD´s have 77-inch propellers, your Airacobra-derived propeller tables, and Zero Lift Drag and Skin Friction tweaks.

For the N333XT low-altitude racing record breaker, after adjusting Boost Gain to 1.835642, and putting in an assumed 44 in. Hg max. MP, I got:
>500 ft: 394.4 mph, 395 Hp, 44.0 Hg, 37.7 prop pitch.
>5500ft: 435.2 mph, 413 Hp, 43.8 Hg, 41.0 prop pitch.
... which looks plausible.

Then, for the higher altitude N777XT speed demon, with 2.56 Boost Gain, and 39.5 in. Hg, I got:
>500 ft: 361.1 mph, 352 Hp, 39.5 Hg, 35.0 prop pitch.
>5500ft: 388.4 mph, 370 Hp, 39.5 Hg, 39.6 prop pitch.
>17500 ft: 440.0 mph, 400 hp, 38.1 Hg, 44.9 prop pitch.
...which also looks plausible. The 2.56 Boost gain, although with a slightly higher performance peak a bit below below 17500 ft, seems to allow for a few more mph at lower altitudes.

Well, I suppose this would be the more correct way to go about this business.
Nevertheless, as there is only one single reliable piece of performance information for each of the two planes, I don´t feel this is good enough for an upload.

Cheers,
Aleatorylamp

 

[aleatorylamp]

Top Speed is now Top Speed Cruise...

Hello again,

There have been some perhaps significant amendments on one of the information pages on the Sharp Nemesis Sports Class Racer N777XT.
The speed reference is no longer "Top Speed: 440 mph at 17500 ft.", and the confusion as to the engine manufacturer being TIO-540-NXT is gone, now clearly stating that this is the engine model.

The first change regarding speed was over a week ago, with a comment approximately: "Cruise along comfortably at 440 mph at 17500 ft", which a couple of days changed again, now reading: "Top Speed Cruise: 440 mph at 17500 ft".

This of course considerably changes the situation, allowing for the 5-minute top speed to lie appreciably above 440 mph, maybe around 253 or 256 mph. It means that the speed values in my last post will hopefully change for something closer to the speeds that were being speculated on previously on this thread, i.e. 380-385 mph top speed at S.L., and around 402 mph for Reno Stead altitude.

Let´s see what happens later on today after further Drag adjustments. If this all fits in properly, maybe I WILL upload the model, that is, if I can fix the aft wing-fairing bleed, which I haven´t been successful at yet.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,
Glad you have things more or less figured out.
It is kind of hard going after a target when it isn't certain what that target actually is.
I was already certain that the TIO-540-NXT was a custom Lycoming setup and didn't really have all that many analogous variants for comparison.

Have Fun!
- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thanks for your comment!
Yes, it is quite a relief that the numbers are now slowly falling into place a little better. It has been like chasing a mirage in a desert, or trying to look around in a shadowy forest where nothing is what it seems.

As you say, that engine was specially built for the NXT and hardly any performance details are quoted anywhere.

So, I suppose that for prop planes, normal cruise lies at about 75% throttle, and my guess is that top speed cruise aka maximum continuous power or high speed cruise would lie between 85% and 90% throttle - unless of course I´m very much mistaken, which could also happen.

Adjusting Drag, at first I got 440.8 mph high speed cruise at 17500 ft with 87% throttle, full throttle giving 467.5 mph. At 500 ft, top speed was 387.3 mph, and at 5500 ft, it was 414.2 mph. Perhaps all this is a bit high.

Then I increased AirEd Drag from 20 to 21, and now got 440.0 mph with 88% throttle at 17500 ft. Full throttle now gives 463.1 mph. Then, at 500 ft full throttle gives 375.8 mph, and at 5500 ft, 408.6 mph, all of which I thought looks much better. Would you agree?

Further increasing Drag to 22, to get the desired 402 mph for 5500 ft would result in too low a speed at 500 ft, and push up the % for high speed cruise a bit more, which may not be so correct, don´t you think?

Anyway... Enjoy your Sunday tomorrow!
Cheers,
Aleatorylamp.

 

[Ivan]

Hello Aleatorylamp,
You are doing the research. I am not. I am not convinced that all the data that is being supplied to you is entirely accurate.
There are probably a lot of qualifications to the data.
This is one of the reasons I don't try to build specific aircraft. Often the data on a single aircraft is incomplete.
I have wanted to build the Hughes H-1 Racer for years, but the amount of reliable data isn't all that great and that has been around for years.

- Ivan.

 

[aleatorylamp]

Hi Ivan,
Well, not a very encouraging situation after all - still too many suppositions then.
Cheers for now,
Aleatorylamp

 

[aleatorylamp]

An educated guess, perhaps?

Hi again, Ivan,

Given the small amount of reliable data not only on the N777XT but also on the whole series of 10 Nemesis NXT Kit aircraft, I was thinking about possibilities for not scraping the project altogether, and upload the machine with at least reasonably approximate performance.

We know CFS1 makes us operate within its limitations, and we can achieve reasonable approximations to get performances as best as we can for our models, so what´s wrong with some educated guesses for one or two missing aspects that no amount of research will reveal? Even AirWrench fills in approximate data if something is missing, so this is be deemed as quite acceptable.

With the latest piece of information about 17500 ft performance being 440 mph maximum cruise, it is becoming quite obvious that pieces are starting to fall into place. The only data missing is really what happens at 500 ft.

Earlier on in this thread, when we were discussing low altitude performance, the conclusion for 402 mph top speed at Reno Stead altitude was an educated guess, and for 500 ft, we had the impression that 390 mph was a bit high. These were educated guesses.

So, we only need another educated guess: When will it give the impression that speed at 500 ft could be too slow? Perhaps definitely below 370 mph, or maybe only below 380 mph?

I mentioned 2 sets of speeds in my post #136, and possibly the first was more reasonably approximate than the second one, but I´m not sure, because my educated guesses are definitely not as good as yours - I don´t know half as much about aircraft as you do.

So, that´s all I´m asking, which of the two sets of speeds mentioned in my post #136 would you feel is more reasonably approximate?

Apart from the speed at 500 ft, there´s the difference between Top Speed Cruise and Top speed, which is 27 mph in the first set, and 23 mph in the second set. What I can´t find in my research, is how much faster a plane like this be under full throttle as compared to high speed cruise.

I was using a boost gain of 2.631, as suggested by AirWrench, but I also tried 2.56, as you had suggested. The difference here is that top speed at 17500 ft is 4 mph slower, and at 500 ft, it is 1 mph higher. At Reno Stead altitude, the difference is only 0.1 mph.

Any possiblity for an educated guess, or shall I scrap the project entirely?

Thanks in advance for your attention and efforts!
Cheers,
Aleatorylamp.

 

[Ivan]

Hello Aleatorylamp,
I suggest you go back to basic principles.
What do you REALLY KNOW about the Nemesis NXT?
All of them share the same basic dimensions, very similar weight, probably the same aerodynamics.
You have a pretty good idea what kind of power it took (about 450 HP) to get a certain speed level on a race course and come in second place.
You know what kind of speed was needed for record breaking runs by Jon Sharp. From that and the Cube root rule, you can estimate the power level.
You have a pretty good idea of the boost level that some of the Type Certified TIO-540 were using most probably without ADI.
You can be certain that Sharp's aircraft was running higher boost and higher power though how high he could maintain that power level was not known.
I believe you are absolutely insane to believe you can put a 45 Gallon fuel tank into each outer wing of the Nemesis NXT.
Don't try just messing with some values and screwing with the tables in the Air file. Do this in basic math. You will run into fewer unpredictable results that way.

Now keep in mind that just from a very casual reading, it seems that the Nemesis NXT in typical form probably was not quite capable of 400 MPH at ANY altitude much less at 5000 Feet. It took a bit more than the typical engine to do that.
When you get your numbers from calculations on the low level record breakers and pylon racers, you may also come to the same conclusion.

Here is a funny story from a couple days ago:
I was showing my Daughter what I thought was a rather cool spreadsheet for doing some conversions of Indicate to True Airspeed.
Imagine my surprise when she told me that she had done a very similar spreadsheet back in college (and she is not an aeronautical engineer). She then went on to explain the principle of pitot tubes to her boyfriend who actually happens to be an aeronautical engineer. You gotta love it when that happens! THIS is my baby girl!

- Ivan.