Electric Airspeed Record.
Discussion
Equus said:
IforB said:
No he stated that the best place for weight in an aircraft with this kind of performance is in the wing. I am just pointing out that it absolutely isn't.
And AW111 has explained why MaxTorque is absolutely right, and you are absolutely wrong.Even the most inept 1st Year Engineering student will be able to tell you that it's better to have a load distributed along a beam (which is effectively what the wing is performing as) rather than concentrated as a point load in the middle.
So, with your knowledge, why would you put weight out into a very thin and limited space such as a laminar flow wing. What do you think the stall/spin characteristics would be like on an aircraft like that with weight outside of the centreline?
Would that make the performance better, worse or potentially downright dangerous?
Obviously I would love to hear your views on how aircraft with wing sections like this operate at and beyond the critical angle and how outboard weight would assist or hinder this. I’d also love to hear your thoughts on what the flight test regime would need to be to establish the safe envelope of operation. If you could reference EASA regs as opposed to the FAA experimental flight category, that would be even better.
There is more to building an aircraft than simply drawing up load paths. The thing still has to be fit for purpose for its primary job, which is to fly and perform as required.
CanAm said:
IforB said:
The old Supermarine aircraft were trucks in comparison to the Nemesis. It is tiny in comparison and weighs very little. That’s progress. It is able to better the speed of the S.6 but on a fraction of the power. The S.6 simply battered physics into submission through power! 1900hp doing 328mph vs 350hp doing over 400.
But not bad for an aircraft of 90 years ago with a pair of bloody great floats underneath! The S.6b finally cracked the 400mph barrier too!IforB said:
I am bringing the discussion back to what it should be about, this aircraft and the attempt on the speed record, not some nebulous and irrelevant nonsense about electric airliners.
Hear, hear!ash73 said:
Why are people suggesting putting batteries in the wings? It's a speed run, they should be as thin as possible to minimise drag.
If you had a free hand - and no budget restrictions - even the amount of thickness which is necessary to give the wings sufficient structural stiffness (and that that structural thickness could itself be reduced by having some of the battery weight distributed along the wings, instead of concentrated as a point load in the fuselage) would be sufficient to offer useful battery space.Technologies are now available/being developed where battery cells don't need to be cuboid or cylindrical - you can shape them to the space available.
As with most record attempts, though, this one isn't about the best that technology can achieve - it's about the best that the sponsor's marketing budget is willing to stump up the cash for.
Equus said:
ash73 said:
Why are people suggesting putting batteries in the wings? It's a speed run, they should be as thin as possible to minimise drag.
If you had a free hand - and no budget restrictions - even the amount of thickness which is necessary to give the wings sufficient structural stiffness (and that that structural thickness could itself be reduced by having some of the battery weight distributed along the wings, instead of concentrated as a point load in the fuselage) would be sufficient to offer useful battery space.Technologies are now available/being developed where battery cells don't need to be cuboid or cylindrical - you can shape them to the space available.
As with most record attempts, though, this one isn't about the best that technology can achieve - it's about the best that the sponsor's marketing budget is willing to stump up the cash for.
Do you know anything about super critical laminar aerofoil profiles and how thin they actually are?
Or are you talking out of your hat?
IforB said:
Do you know anything about super critical laminar aerofoil profiles and how thin they actually are?
Yes thanks; do you?This is the NACA NLF (natural laminar flow) aerofoil section, of the sort used by the Nemesis NXT:
As you will see, you needn't worry too much about cutting yourself, and there's actually quite a bit of space within the profile.
I used to have a budgie like you when I was a kid. He'd argue with anyone or anything, just for the sake of it. We gave him a mirror with a bell on it, so that he could argue with himself.
Bearing in mind that this thread is (allegedly) about this particular project, to beat the existing record of 210mph(?), there is no need to muck about with the technology. The airframe is proven to be capable of over 400mph with a known Lycoming engine. I think earlier in this thread, someone calculated the power of the electric motors to be in excess of that. There is a nice 90 US gallon space in the middle of the fuselage, so why even think about changing the wing and putting the batteries other than in that space?
CanAm said:
Bearing in mind that this thread is (allegedly) about this particular project, to beat the existing record of 210mph(?), there is no need to muck about with the technology. The airframe is proven to be capable of over 400mph with a known Lycoming engine. I think earlier in this thread, someone calculated the power of the electric motors to be in excess of that. There is a nice 90 US gallon space in the middle of the fuselage, so why even think about changing the wing and putting the batteries other than in that space?
Indeed. There is absolutely no requirement to change the aircraft structure. It has already more than proved capable of doing the job required. Stuffing around with the structure just for the hell of it is not needed. If it is required for practical purposes, then great, but the beauty of batteries is that you can place them where you want if you have space. We use them as ballast in our autonomous ship, ok, we chose AGM old fashioned batteries, but the weight of them was actually a bonus and very useful for trim purposes.
Once you start going down the rabbit hole of mucking about with the structure, then it all gets expensive fast.
The calcs are not too terrifying, but why bother when you have no need? If you can avoid a design and certification loop by not touching something, I’ve always been a great fan of that!
IforB said:
It may be a racer, but they pull some proper G around the towers. It might not be +10 -10, but at +6 -4 G then it is just as capable as many aircraft designed for Aeros.
The same principle stands. You do not want weight out from close to the CofG if you can avoid it. Centralising mass is a good idea when you are pushing things hard.
If nothing else, to improve roll rate.The same principle stands. You do not want weight out from close to the CofG if you can avoid it. Centralising mass is a good idea when you are pushing things hard.
6000 18650 cells weighs about 300kg. The battery pack does extend further back than the CofG though so will not be putting all of its effort to tipping the plane on its nose...
Equus said:
ash73 said:
No requirement but it would be interesting to see what improvements could be made.
It would be nice if World Records were about pushing the boundaries of available technology, rather than 'what's the least money and effort we have to expend to get the publicity'.wst said:
IforB said:
It may be a racer, but they pull some proper G around the towers. It might not be +10 -10, but at +6 -4 G then it is just as capable as many aircraft designed for Aeros.
The same principle stands. You do not want weight out from close to the CofG if you can avoid it. Centralising mass is a good idea when you are pushing things hard.
If nothing else, to improve roll rate.The same principle stands. You do not want weight out from close to the CofG if you can avoid it. Centralising mass is a good idea when you are pushing things hard.
6000 18650 cells weighs about 300kg. The battery pack does extend further back than the CofG though so will not be putting all of its effort to tipping the plane on its nose...
Equus said:
IforB said:
Do you know anything about super critical laminar aerofoil profiles and how thin they actually are?
Yes thanks; do you?This is the NACA NLF (natural laminar flow) aerofoil section, of the sort used by the Nemesis NXT:
As you will see, you needn't worry too much about cutting yourself, and there's actually quite a bit of space within the profile.
I used to have a budgie like you when I was a kid. He'd argue with anyone or anything, just for the sake of it. We gave him a mirror with a bell on it, so that he could argue with himself.
Could you tell the class how many aircraft you've flown that have similar profiles? I would be fascinated in your opinion on how they handle, especially when you give them some grief.
I'm not here to insult you, so, it's disappointing to see you resorting to that level of discussion, but hey ho, it is the internerd, so not surprising.
Again, I'd ask you how the handling characteristics of the aircraft would be affected by the addition of weight outboard of the fuselage and what that impact might be on the handling characteristics for an aircraft like this that is likely to be pushing the boundaries a bit.
Feel free to use personal experience to illustrate your points. I've only got 20 years of flying to fall back on, so I'm always happy to learn from someone who knows more. After all, you never stop learning in aviation.
IforB said:
I'm not here to insult you, so, it's disappointing to see you resorting to that level of discussion...
What 'level of discussion'? It was you who tried to bamboozle people by using big words that you clearly don't understand. You're now trying to bulls
t, bully and bluster your way out of being embarrassingly proved wrong.A 'supercritical laminar aerofoil profile' is one that is designed to operate with transonic airflow. We're talking about an aircraft here that is designed to operate at no more than 400mph, which is why it uses a non-supercritical, natural flow aerofoil profile.
I merely posted an example of the actual type of aerofoil profile that is used, to demonstrate that there is plenty of volume within the section. The skin, even in composites, will be no more than a few (and I mean a few - low single digits) millimetres thick, the structural sections within it, likewise. What do you imagine, inch-and-a-half plate? Perhaps you've spent too much time designing ships?
We're talking about an aircraft that has to fly in a straight line for long enough for its speed to be measured, not an aerobatic aircraft or pylon racer.
I am sure that a competent and experienced pilot will be selected to fly it, and as much as the idea may bother you, plenty of other aircraft have flown with the addition of weight outboard of the fuselage, even one or two with genuinely slender aerofoil profiles and very high wing loadings:
Of course, I appreciate that you know much more than Lockheed, Northrop and Lear...
Edited by Equus on Sunday 13th January 01:36
Equus said:
It would be nice if World Records were about pushing the boundaries of available technology, rather than 'what's the least money and effort we have to expend to get the publicity'.Spreading the batteries out in the wing could help them stay cool when being discharged at a high rate, if they are in contact with the wing skins. Packing all the cells into one block in the fuselage will only exacerbate their temperature rise, which may be avoided at the cost of additional drag in the form of cooling ducts.
maffski said:
Achieving your objectives with less resources (and so less money) is pushing the boundaries of available technology
It's laudable and challenging, certainly, but almost by definition you're going to be using readily available, off-the-shelf components for the most part (QED), so not really pushing too far into unexplored territory?GliderRider said:
Spreading the batteries out in the wing could help them stay cool when being discharged at a high rate, if they are in contact with the wing skins. Packing all the cells into one block in the fuselage will only exacerbate their temperature rise, which may be avoided at the cost of additional drag in the form of cooling ducts.
This is, on face value a really good idea!When the plane is flying, and power is being drawn from the batteries, the speed of the airflow over the wings will be, generally speaking ignoring AOA changes) proportional to the power being drawn. Using air cooling via conduction with the (massive) wing surface area would negate the need for additional and potentially complex alternative cooling methods.
But, Charging on the ground becomes an issue. A fast turn around means fast charging, which means lots of heat at zero airspeed! Perhaps we could could fit water jets and spray bars to airport terminals to cool the wings during ground charging?
BTW, i wonder if this speed record plane is going to use an air cooled battery. They have said "the lightest battery ever made" and the minimal drawings released show what looks to be a low cell packing density, with enough space to route cooling air around the cells.......
The prop wash also could be used for targeted cooling
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