Bachem Natter

[Richard Harris]

Couldn't you support the centre of the shaft with a separate bearing? getting it in the model may be a challenge though

[Erfolg]

I have finally got around to estimating the final all up weight, that is balancing at 30% wing chord. It comes out at between 750-800 grm.

 

The wing loading at the top end (hope it is the top end) is 18-19 oz ft-^2 .

 

It could fly, if my discipline can be reimposed.

Edited By Erfolg on 08/08/2011 14:52:27

[Erfolg]

Having come to the end of my FW 152H and own design park flyer, build and fly projects, I am now considering what to do next.

 

I have thought of a Fairey Hendon, Me110 and Guillows Thunderbolt as potential projects. Yet at the back of my mind is the Bachem Natter. It has sat there in the model room, scolding me for neglect.

 

It has been not on the back burner but of the hob, as a disappointment, primarily in myself. Before final abandonment, I thought another assessment was required. AS all the major components are complete, it was a simple task to stick it on my balance device.

 

I have balanced it with and without motor

 

 

Without motor, the all up weight would be 2lbs

 

With motor the all up weight would be 2lbs 6oz

 

More importantly the wing loading comes out at 18oz and 21 oz respectively.

 

I am not sure if the model is viable, in this configuration. The motor has a max rating of 18 amp, indicating that I could have 150w available. Is this enough, to fly, if not sprightly?

 

 

[Simon Chaddock]

Erfolg

150w does sound a bit thin for what is at best a 2lb 6oz 'sport' plane although if you took 10V as the working voltage you would have 180w.

 

Interesting that Hobby King puts 23A in the title but then gives a maximum rating of 18!

 

My best guess is it will fly all right but it will need a pretty good throw to launch as you won't have much reserve of thrust to overcome the drag trying to climb out at slow speed.

 

Having got this far it would be a pity not to give it go.

[Erfolg]

Quite agree Simon, 180w is not confidence inspiring.

 

Although I did anticipate to some extent the problem of the CG being rearwards, without ballast, I did not anticipate how significant an issue this would be. A lot of ballast is required to get an acceptable CG. I have had an hankering to build a Bede 5, Lear Fan Jet etc. I now think these could be very challenging.

 

My instincts are to put a bigger motor on the back, which will lead to the need for more ballast, which would benefit from more power. A less than virtuous circle.

 

I have learnt a lot about carving "Blue Foam", it seems that the Bf 109H is doable, by me, using this method.

[Erfolg]

Although threatening to restart work on the Natter, the rearward CG and the implication of Pb nose weight, somewhat dampened my enthusiasm.

 

However I was reading a October 1997 QFI mag. In it, is a picture of Nigel Hawes 1/4 scale Yokosuka Ohka, better known as a Baka" or "Cherry Blossom".

 

The NH model is a little bigger at 40" span. The wing loading at 18oz ft-1. There are similarities.

I have had a change of heart of where and how to mount the servos. The more I thought about mounting the servos in recesses in the cockpit area, the less I liked it. I just thought it would weaken the nose considerably. In a model, which I suspect will see the ground, in unintended ways than i would like. They will now hopefully go in the middle area, Lipo permitting.

 

It was interesting to read that NH installed an Estes rocket motor, which provided spectacular performance. Given the problem of achieving a satisfactory CG due to the motor assembly, a rocket motor could be the solution. If I only knew what NH used.

 

 

[Keith Simmons]

That may be the best way to go, have a look at rocket kits which the motors can be supplied separately and do have a short burn. Does the Natter glide well ? If yes, a short zoom to height and speed then a nice glide back and no torque involved, Perhaps you can choose the motor to achieve your CG issues. Good Luck

[Erfolg]

Keith

 

It is nowhere near finished. It stares at me when I enter my modelling room. I would banish it into the garage, other than there is nowhere there to store it. all the spots are taken, by retired or models awaiting another outing.

 

The NH model does/did not glide apparently in still air. It seems it was primarily a slope soarer. They do say anything will fly on the slope, if it blows hard enough.

 

None of the Bachem Natters on U-tube seem to glide, they are either under power or rapidly descending. So I am anticipating something similar.

 

Almost being silly, the best solution could be a rocket motor and parachutes as per full size.

[Mowerman]

Leave the motor out and chuck it off a hill.

[Erfolg]

Today, I was starting the clearing process to start the construction of a 42" Spitfire. That damned Bachem was looking at me. Although I still have to decide if an earlyish model with the longer nose or a 24 Spitfire, with the bubble canopy.

 

I decided it was of to the garage with it, to join the other airframes consigned to the junk. I took it downstairs, left it temporary by the garage door. As I decided that I had better prepare for this evenings dinner.

 

Whilst doing the preparations for dinner, I was contemplating how many times I had seen Phantoms and other scale models with propellers stuck on the nose, how awful they look, with the cylinder head poking in the breeze, silencer sticking out like a giant wart, drenching the model with a blue haze all down the side.

 

I then thought, although not ideal, in my mind, an electric motor is not seen, nothing sticks out other than that propeller. The more I thought, the better it seemed. You see I had been contemplating a bowden cable drive as seen on some fast electrics and IC boats. This seemed rather messy, although it would allow the motor to be sited near to the nose. No I finally conclude, it is a motor in the nose, at least I can then try and fly it. Other solutions can be tried later if it does fly.

 

So after preparing dinner, I picked up the model and carried it back upstairs. Will I actually do something is the question now?

 

Edited By Erfolg on 28/01/2012 15:47:37

[Simon Chaddock]

Erfolg

Given that the Natter was rocket powered does it really matter if the prop is at the front or the back?

Its not as if the nose of the Natter is particularly 'fine' in any case.

 

Go for it!

 

[Erfolg]

I had contemplated a flexi drive to a rear mounted propeller, to date I had not found a combination which is long enough. I also had become concerned with how to mount the propeller, support housing and how it would be mounted.

The idea was to ensure that the motor shaft would be parallel to the prop drive. With the motor mounted in the bottom of the fuselage.

I have come to think that a ordinary prop shaft arrangement would have the model fly able, although there would be some engineering short comings in that the propeller would not be constant velocity, with the motor at some angle to the prop drive line. This would be necessary to get the motor low enogh not to interfere with the wing. Not an elegant solution.

I now think I have been unduly concerned by the prop drive and bearing arrangement, This is based on the numbers of individuals pressing gearbox housings into service, in a manner that they were never designed to be primarily loaded, with the Panther Autogyro. Non seem to have an operational issue. My Natter should, hopefully be far less demanding.

So compromise, however great, seems a worthwhile way of moving this project forward again. If it does not work, I can then try something else, until it does work adequately. At present I am disassembling various gearboxes, with a view to see if I can press something into service. Apart from almost spearing my hand with a screwdriver, undoing a spacer grub screw, I am getting there now with a collection of parts.

Edited By Erfolg on 28/04/2013 21:52:23

[Simon Chaddock]

Erfolg

Wow! You started this thread very nearly 2 years ago!

But know what you mean. I hate giving up on a challenge!

Edited By Simon Chaddock on 29/04/2013 19:52:15

[Erfolg]

Simon I really did not know that!

I am still not moving forward, I spent last night, way into the morning looking at the available bearings from HK. Having jotted most, if not all down, I then realised that a thrust bearing which I thought fitted the bill, had not been restocked for over 6 months.

I then spent some time looking and measuring the tubes I have available, to take the OD of the bearings. Only to conclude that the ones I have are either to small or to large ID.

Not having any machining facilities and tooling is a bind.

I then start asking myself the question, are you trying to over engineer this problem. A good engineered solution may be gilding the Lilly. Many seem to manage quite well with an utilitarian set up.

It seems that what ever i eventually do, the system will be much more complex than I intended. This will mean it will be heavier than it should be and that the model will not fly as well as it could.

Ahhhhhhhhhhhhhhhhhhhhhhhhh!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Erfolg]

I have atarted to make some progress again. I have been scouring web sites for suitable bearing, looking at the collection of tubes etc I have.

A one time engineer who had designed bearing assembly for grinding heads on machine tools and numerous other heavy duty roles, my concepts owed more to battleships than aircraft. My ideal assemblies incorporated thrust bearings for the end loads, ball bearing pair to deal with radial forces, with spacers to ensure acceptable end loadings. Then there was the issue, I do not have a lathe, nor is it just a question of the material being stock item. In short, well over the top, time consuming to make, probably much heavier than duty demanded and probably last four or more times longer than the most optimistic life of the model.

In the end i started again and scoured my not in use parts. Old 540 gear boxes dismissed as being to heavy and over the top. Instead, I decided to go the Lotus route of old, and use something which is possibly right on the edge of viability. A head bearing assembly from a medium helicopter, which I could modify.

I have decided to use a rod drive, although I am concerned that whirling will occur. To prevent the occurrence if calculations or experience indicates the phenomena will be present, a central bearing will be place at the mid point to deal with the first critical speed.

I have attached a ply rear attachment ring, to fasten the assembly to it.

The tailring acts as both attachment and a spigot.

The project will continue again as a low priority project whilst I build a HK Firenza for my "A" test back up.

[Keith Simmons]

Erfolg

Have you seen the latest magazine? spitfires over Berlin. The air war in Europe 1945.

it has 8 pages on development work on the Bachem Natter with the fatal mistake of Lothar Sieber, it's test pilot. The mag has interesting stories of the other aircraft including the possibility of the Me 262 breaking the sound barrier in a dive, The Me 163, He 162. plus all other aircraft during the final months of the war including air battles. (German & Allied).

Keith

Edited By Keith Simmons on 19/06/2015 09:12:17

[Colin Leighfield]

The Natter fascinates me as well, I think it's "doable"although I'd be inclined to stick with the scale flying surfaces and probably send it off with a bungee. That would be closer to reality than a hand launch. A good glide afterwards would be completely unrealistic.

The 262 never got close to the sound barrier, fast though it was, it had a limiting Mach no. of only 0.82, so was into compressibility problems at speeds not far above its' level flight maximum. The 163 was similar and its' nose would tuck down, so if you pushed your luck in a dive at high sub-sonic Mach nos. you weren't going to come out of it.

Keith, which mag do you mean, is it Fly Past?

[Keith Simmons]

Colin, the mag was not Fly Past, it's from Mortons & I got it from WH Smith for £6.99 & is it against copyright to show it on here? Look at my album "various" and I have a photo of the front cover. Let me know so I will delete the album.

The development of the Natter was rushed & if the SS who was in control of the project waited for the Autopilot to be completed for the launch/climbing stage to bomber stream height, the test pilot had to keep the joystick in neutral position on the way up. The forces he encountered was 3G.

About the 262, it was unknown, however he went into a full power steep dive from 36,000 ft going beyond 1100kph in the red danger zone with rivets popping out of the tops of the wing and the aircraft vibrating & shaking wildly. For a brief moment the aircraft responded to control again then went out of control. He managed to change the incidence of the tailplane and slowed down. He had wanted to help a fellow trainee from a P-51 mustang and fly down to help.

How do you change the tailplane incidence? By moving the elevators but that's control. Or will trim do it?

According to the article, the fuselage countered against it without knowledge of the area rule resulting to high drag at transonic speeds, but what if he did go supersonic (when he had brief control) and the drag pulled him out of it?

Computer simulations at Munich Technical University in 1999 concluded that the Me 262 might have been able to go supersonic?

[Colin Leighfield]

Thanks Keith, I'll have a look. I think that Siebert was very unfortunate, from what I've read about it the Natter was capable of doing what was intended, but was overtaken by events.

The 262 was tested very extensively after the war here, in the USA and Russia. It's limiting Mach no. In a dive was found to be 0.82, about the same as a Meteor. Similar claims were made for the P38 after a pilot described the same kind of terrifying experience from a terminal velocity dive. I actually spoke to a WW2 Lightning pilot 30 years ago who told me how frightening the Lightning was because it accelerated so quickly in a dive that it hit compressibility in a very short time and began to bang and shake. Many Lightning pilots were killed in high speed dives when the plane simply didn't pull out because of this phenomenon. Later I found out from Winkle Browns writings that the P38 had the very low limiting Mach no. of 0.64, which was why it got into trouble so easily and wasn't in fact.going anywhere so fast as people thought it was. In this situation air speed readings are useless, you need a Mach meter.

Although there's no doubt that the 262 was aerodynamically clean and looked great, the swept wing was chosen for centre of gravity reasons, with the original straight wing design it was too far back. Also by sweeping the wing, you improve cg tolerance. It's doubtful whether the limited sweep on the wing significantly improved the critical Mach no.

Like with all of these things, it's great to speculate. We have reports of Spitfire XIVs popping wing rivets in high speed dives after 262s and they were very likely chasing a plane doing Mach 0.80 plus, which the Spitfire could do as well in a dive, but much faster seems to be very unlikely. So, unless an owner of one of the American built replicas with more powerful engines is prepared to have a go, we will never know. If he does though, we might never see him again.

[Colin Leighfield]

Keith, just looked at your album and have noted the magazine cover details. I think I've seen this somewhere, if I have time I'll drop into Smiths for it. Thank you.

[Simon Chaddock]

Erfolg

Nice to see work on your Natter starting again.

Just out of interest my Natter manages with its motor right at the back although the battery does have to right at the front to compensate!.

And Erfolg has seen it flying.

When you see the aerodynamic limitations of even the fastest planes at the time you can appreciate why it really was considered to be the "Sound Barrier".

It needed a major step up in power to weight and structural strength to safely go through it.

[Erfolg]

I do agree that personal experiences of pilots in aircraft in active service, although given in all honesty, are often questionable in there varsity.

The maximum speeds attained by both the Me163 and 262 can be stated with a little more confidence, in that they were obtained as part of a test and development programme. The 163 at mach 0.92 and the 262 @ mach 0.82. In both cases the objective at that point was not of increasing the speed, rather more establishing the performance limitations.

One of the main problems for both aircraft was related to the fire power as a rate. The closing speeds being very high compared with enemy aircraft of the time. Both having programmes using solid fuel rockets, which apparently leadi to the Mighty Mouse (although if this is by idea or development programme is not clear). The 262 also explored the use of the rotating multi barrel machine gun (the same idea of the USA Civil War Gatling devise). The 163 with automatic fire systems. All to deal with the performance difference of allied bombers and fighters.

There was a time I had thought that the 262 had been designed from inception with swept wings. I then read that they were swept according to Camm due to the incompetence of German designers. I later read that they had indeed been initially straight. Then due to the late availability (due to development issues) of the BMW 003 engines, that it was decided to use Junkers Motors (JuMo) 004, which were effectively developed, and getting near to production. Apparently it was now that the decision was made to use swept wings, as it improved the aircraft aerodynamically, whilst reducing work on relocating tankage and the view of the pilot. Consideration had been given to use a straight wing and moving the engines to achieve the CG. It was recognised that the engines being moved slightly forward relative to the wing LE would provide a mass balance. Design studies had been made incorporating the engines as the Locheed T33 and as the Meteor. Placing the engines mid wing was thought to provide less frontal area. However underslung provided a cleaner wing and stronger wing (without additional weight), better options for both change of engine supplier and maintenance. I guess the meteor had a ground clearance issue using centrifugal engines. The 262 wings went through a lot of iterations before final design and into production.

One of the surprises of history is that I automatically think that all the facts surrounding any aspect of an event would be known and reported fully nearer the time of the event. Often it seems that initially access is given by authorities to those best described as safe hands. Later if we are lucky, others sometimes involved provide, a different perspective or just a fuller account of events, before they themselves pass into history.

This scenario appears to be true of both Waterloo and the Napoleonic wars. I was taught it was a great victory by the British and Wellington that saved the continent., where Von Blucher, turned up late, and just was there. Now it seems that approx 30% were British, 30% Prussians ( Germany as we know it had not yet been formed, being the German Federation). and that the remainder were Belgians, Dutch, Danes and possibly others. It is a small wonder that they all managed to communicate and corporate effectively. It also seems it was also a victory for privilege, rather than to establish democracy, although Napoleon was establishing his own monarchy.

[Keith Simmons]

I would read the article with a pinch of salt. The German pilot just went into a full power dive & was lucky to survive.

The sound Barrier was at that time a destructive barrier and after the war would anyone really pushed the Me 262 to see if it went supersonic and admit that the Germans got there first, beating the Americans?

The Victor went supersonic to the dismay of the Vulcan crews, was that in a dive?

I would recommend the Magazine as it has so many stories that I have not heard before and the Natter was one of the most dangerous aircraft to fly.

Colin, I accept that you have far more experience in those sort of matters and I would like maybe a full scale test of the unmanned Me 262 shape with the same wartime jet thrust and see what the speed or Mach results are.

[Colin Leighfield]

Erfolg, the 1943 Meteor with the Metro Vick Beryl axial flow motors had under slung nacelles, just like the 262, with the undercarriage lengthened for ground clearance. From the front, they look surprisingly similar.

Keith, I don't know about experience, I have read a lot but forgotten most of it! I think your analysis of what happened is smack-on.

The Victor was faster than the Vulcan and could go supersonic in a dive, the Vulcan couldn't. I thing the reason the Vulcan gets all the kudos these days, apart from looking and sounding fantastic, is that when RAF strategy changed to low level, it was much better suited than the Vulcan.

[kevin b]

Anybody want this ?

Book is about A4 size and like brand new.

I'm collecting old (1970's) Radio Modeller magazines.