Bf 109 F series

stona said:

Not conclusive, but I've been through a couple of Bf 109 hand books and no angles for toe on the main U/C are given. They give angles for just about every other conceivable part of the airframe so I'm leaning towards a toe of big fat 0.
Cheers
Steve

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I may be wrong but my understanding of physics tells me that the angle of the wheel axis works the same as a conventional toe in would do.
cimmex

The fuselage joins to the firewall in a sort of 90° oval ... not quite an oval actually. Along the lower portion is a sort of straight section.

Inside the fuselage there are two 90° L-shaped extrusions bolted into the fuselage-firewall joint in the mostly straight section. The landing gear attach pivots are bolted to these two shaped extrusions and stick straight out from the firewall. Since they are somewhat wide, relatively speaking, the front of the pivot is triangulated to the center of the firewall with a sort of turnbuckle affair.

If you twist one way, the front is forced outward. If you twist the ohter way, the front is forced inward. In this manner, you twist until each gear leg retracts into the center of the wheel well and then safety the turnbuckles so ithey can't move. That sets the retraction plane of the gear leg and the alignment of the wheel is cast into the upper gear leg drag link point with no adjustment possible other than setting the gear to retract into the wheel well. I suppose you COULD offer several lower drag link pivots that would slightly alter the alignment. I am not aware that this was ever done, but it COULD be the most simple "fix."

If there were a separate alignment for the drag link alignment, it would be simple to set the tracking of the gear. It would have been a minor redesign. But it never happened.

There is no possibility to move the wheel well since it is right up against the spar. So you'd have to either re-align the drag link (wheel alignment) or make it adjustable in the field. Of the two, I'd opt for an adjustable alignment with a screw or bolt head with threaded alignment movement and a tabbed lock washer that is set and then bent into a locking recess. There are several of these type locking washers in most engines of the time. You set them, bend the lock into place, and it never needs to be touched again until disassembly.

End of the issue. If that didn't fix the tracking, it would be time for redesign.

Out of curiosity, how would a F-4 stack up against a G-10 and K-4?

Also, can someone please clarify what "toe-in" is?

The tires are NOT aligned in line with the fuselage or direction of travel. Same with cars,

No toe at all or very slight toe-in is quite stable. Too much toe-in is bad, too.

Toe out makes the vehicle very "twichy" ... it seems to want to dart one way or the other at all times.

GregP said:

Improvements to the Bf 109F:

1) Bubble canopy and a windscreen with much more narrow posts or no posts. No big deal, DO it.
2) Landing gear. Move the gear outward to widen the track. Easy but would mean a production interruption.
Not so easy. Landing gear designed to carry loads into airframe - not wings. Take the gear attach points to the wing could cause big structural re-design and added weight.
3) Add a rudder trim tab. No real issue and not much weight.
4) Increase mechanical advantage for the control stick. Easy and NO extra weight.
5) Reduce flap span by about 1 foot per side and add aileron span. Increase aileron travel and add tabs to reduce roll forces at high speed. The 109 already had a very low stall speed and short takeoff and landing distances. These steps wouldn't affect them much.
Wonder what that would mean to wing torsion?
6) I'd leave the engine alone and try a wider-chord propeller. They worked well on the Fw 190's. Why not the 109's?
All about tuning performance - which attribute do you want to diminish?
7) Add ore fuel. Put in another 20 gallons at least.
Where?
8) Finally, the biggest headache for many units all during the war ... add a damned electric starter! The scrambles would be MUCH quicker!
9) Once these are done, quit messing with it and get on with the successor while producing the new Bf 109F as rapidly as possible.
10) Steal as much 130-grade fuel as you can get and make that DB hum!
Steal from where? Houston, NJ?

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Uncle Willy must have been pretty stupid to not figure out how 'easy' such design changes would be..

drgondog said:

7) Add ore fuel. Put in another 20 gallons at least.
Where?

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Should be pretty easy - there is plenty of room in the back of the fuselage, and the 109 versions progressively added more fuel.

See:

Bf 109 B - 235 liter in L-shaped tank
Bf 109 C - 337 liter in enlarged L-shaped tank
Bf 109 E-G - 400 liter in enlarged L-shaped tank
Bf 109 K - 400 liter in enlarged L-shaped tank plus optionally the MW tank could be used as an extra 115 liter fuel tank.

If the drawings are somewhat accurate, you can see they played with the positioning of the tank, too. The second version (C) seems to also have moved back the tank, the third version (E-K) kept its place but extended it forwards.

The late Gs also had this same tank, they just did not have the valves to use it as fuel tank, but this should be an easy fix. If more fuel is needed, I do not see much problem with a further enlargement of the L shaped main tank. At worst, ballast in the nose or a front fuselage extension ring (a la D9) could solve any possible CoG problem.

Cutaway drawing of a G-14 but should be useful.

Tante Ju - where put 130 pounds and 20 gallons of fuel volume aft of main fuel tank? What would effect to CG be?

10) Steal as much 130-grade fuel as you can get and make that DB hum!

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The Germans were using C3 fuel during the BoB in the DB601.

drgondog said:

Uncle Willy must have been pretty stupid to not figure out how 'easy' such design changes would be..

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Mr drgondog
Uncle Willy ,may have not been stupid but
a) it took him 3 years to introduce elementary aerodynamic improvements( tail wheel,streamlined nose, wheel covers)
b) It took him 2 years to introduce the tall rudder and erla canopy
c) never standarised improvements like the fletner tabs, the radiators isolation valves,rudder tabs, and others
d) actually the radiators of the last 109s were simpler than those of -F
I imagine that you would agree that these are not terribly dificult improvements.
Obviously the company had other interests and intentions thatn to improve the 109

jim said:

Mr drgondog
Uncle Willy ,may have not been stupid but
a) it took him 3 years to introduce elementary aerodynamic improvements( tail wheel,streamlined nose, wheel covers)
Trade off between drag and weight
b) It took him 2 years to introduce the tall rudder and erla canopy
Don't know that either was his decision to make.. and tall tail was a function of increased torque as the DB series increased Hp.. P-51H also
c) never standarised improvements like the fletner tabs, the radiators isolation valves,rudder tabs, and others
d) actually the radiators of the last 109s were simpler than those of -F
I imagine that you would agree that these are not terribly dificult improvements.
Obviously the company had other interests and intentions thatn to improve the 109

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Willy was an absolute fanatic regarding weight but after he lost control of the Bf 109 manufacturing I don't think he was involved much in production/production design decisions.

Well, in answer to some of the questions, I never said moving the gear would be simple. I said it should have been done. I like the stub wing idea brought out earlier in the thread. Simple and easy to implement.

The slight extra aileron size would no doubt add a bit of torsion, but that is why you have designers ... to handle things like required changes to correct problems.

Where to add the fuel? Well, we have a Bf 109G-6 and an Hispano Ga.1112 Buchon. In both of them, the fuel cell could be extrnded backward a bit. If I can fit into the space, surely some fuel could ... and I have been in that space when we were working in that area. The room is there.

I never meant to say Willy was stupid, but he was notoriously stubborn. He may well have thought the Bf 109 to be beneath his dignity to re-address, I can't say. However, of the major fighters, how many did NOT have rudder trim? How many had a canopy with so much framing around it? How many got so solid above 350 mph as the Bf 109?

Name one that suffered more takeoff and landing accidents.

Reading quite a few combat comparisons I note that almost all say the way to handle a Bf 109 was to stay fast. When everyone knows that, it's time to change something.

Sorry, I don't get the objections to improvements but it's becomming increaslngly clear why the improvements were not to come. Here it is 65+ years later. We KNOW the weaknesses and I'm still hearing excuses for not fixing the Bf 109. No wonder it never got fixed in real life. When the war ended the windcsreen was still the worst in service anywhere in a front line fighter. It was still a short-legged bird that was prone to running out of fuel just when the battle was being fought. The controls were still very heavy at speed, and the landing gear was still not fixed.

I'm not saying the Bf 109 didn't make a significant contribution to the Luftwaffe's war effort, it did. I am saying it could have been better almost immediately, but never was. With so much attention to the quality of their weapons, the Germans left the Bf 109 with major weaknesses that could easily have been corrected.

It almost smacks of conspiracy, but there is no real reason to suspect anything more than indifference on the part of the Luftwaffe to the Bf 109's shortcomings except for the obvious point that the weaknesses were never corrected and could so easily have been.

Greg - could be that pilots very familiar with the 109 were solicited. If so, the discussion is always "if we do that, the other thing won't be quite as good" or "production re-tooling to change wing design is XX months" or "add this and your climb rate will be yy less"

BTW - if you move the gear - it has to re-located to main spar or create a major carry through Structure just aft of the leading edge "d' box is.. last - to do so means a major re-design for fuselage carry through structure if wings are to be made 'removable' as before.

MAJOR re-design and significant weight increase - look to Milosh's post 88 for closer inspection.

Actually Drgondog, it is quite possible that operational Bf 109 pilots WERE consulted and had no suggestions for improvement. If that is the only fighter they flew, then maybe they never thought of the Bf 109 weaknesses AS weaknesses since that's the way it was from when they first flew it.

I've heard maybe 2 dozen P-51 pilots say it was the best fighter of the war ... but it was the ONLY fighter they ever flew. So how good is their opinion? Depends on the listener I suppose. I like their war stories but have little respect for their opinions of other fighters they never flew and never flew against either.

Adding a stub wing would greatly simplify the gear structure since it doesn't have to support for any long distance. I'd probably opt for that if I were doing the job. Since it never happened, it's a "what if" that means doing a redesign and estimating the weight change. I'm interested, but not THAT interested. I'd probably add a stub spar only as long as the stub wings were wide, and attach it across the bottom of the firewall, right where the gear is attached in real life. I'd move the pivots outward by about a foot and half on each side, and correct the geometry by changing the toe-in setting ... assuming it seemed to still be needed after moving the gear.

Let's just say that if the weaknesses had been corrected early on, things might have gone better for the Bf 109 drivers, though I doubt the eventual outcome would have changed regardless of Bf 109 changes unless production could have been substantially increased.

Sounds a bit like the US Sherman tank to me. Some glaring weaknesses that could/should have been addressed, but weren't because 1. top brass didn't see a problem (because they weren't fighting/dieing in it) 2. they couldn't afford/didn't want to slow down production to make the changes 3. cost/money issues

Sounds exactly like that to me, too.

Love the Sherman (we have one and run it ... ours has a Continental radial engine) but, if I were going into a tank battle, I can think of places I'd rather be than in a Sherman ... unless there were a lot of hedgerows around to hide in.

GregP said:

Sounds exactly like that to me, too.

Love the Sherman (we have one and run it ... ours has a Continental radial engine) but, if I were going into a tank battle, I can think of places I'd rather be than in a Sherman ... unless there were a lot of hedgerows around to hide in.

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Agree 100%

There were fighters I would rather be in instead of a 109 also. But with a few changes it would have really helped it, just like a Sherman Firefly or a Sherman with a different turret and a 90mm gun would have been a whole different animal.

In the end tho tens of thousands of (on a one on one basis) 'inferior' Shermans ( T 34's for that matter) were exactly the correct choice verses a few hundred Tigers and a few thousand Panthers.
Dreadful for those poor guys that suffered the Tiger/Panther etc but in the scheme of things it was the winning strategy.

It took another 40yrs or so for tech quality to get so good that quantity really didn't matter so much.

Only in some aircraft