Quote:
Originally Posted by Graham Boak
I understand the loss in speed due to the gondolas as more than that: I have 15 in my memory, but whether that was kph, mph or knots I can't say! kph probably. The loss in speed due to the drag of internally mounted guns would be significantly less than that of the gondolas. Weight has a negligible effect on maximum speed.
The 109 wing wasn't significantly weak, and there's no guarantee that fitting extra open spaces would have strengthened it at all. Carrying weight outboard on the wing does reduce the bending moment at the root, but the penalty on agility would over-ride that.
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Here's a recent post of mine on the subject, copied over from LEMB, for what it's worth :
Contrary to popular belief, the gunpods were not so hurting to performance, Soviet trials showed the following results with a clean and gondie G-2 : top speed 666/650 km/h at 7000m, time for a 360 degree turn at 1000m 20 sec vs. 22.6 sec, time to 5000m 4.4 vs 5.1 min.
Messerschmitt's specs for gunpods with ammuntion added 215 kg (135kg w/o ammuniton) to the takeoff weight, and a decrease of speed by 8 km/h at SL.
The weight increase was comparable to normal (inside-) wing installations, taking into account the weight of ammunition boxes, mounting rails for guns which the cannon gondolas contain in one single unit. As noted the gondola guns complete with housing etc., but without ammunition weight 135 kg for a pair of MG 151/20. In comparison, Fritz Hahn gives the installation weight of a pair of MG 151/20 complete with all accessories, but without ammo into the FW 190A-4/U8 as 126.7 kg.
As far as the drag goes, it would be interesting see the drag penaly for a internally mounted MG 151/20 in FW 190, but I've no such data; I have it for Spitfires though, which is detailed for various installations, understood for the change of speed at 360 mph. It goes as, as far as cannon armament concerned compared to the 'ideal' Spit, for our purposes, a Mk I without the cannons in the wing :
Two cannons : - 6.25
mph (ie. B-Wing
Two cannons and two cannon stubs : -8 mph (ie. C-wing)
Small bulge over wing : - 0.5 mph (late C-wing)
Large bulge over wing : - 1.5 mph (early C-wing)
This being compared to about 15
kph (~9mph) measured by the Soviets as speed penalty for gondolas at rated altitude of 7000m on G-2, and the 8kph@SL/~12 kph@VDH given by Messerschmitt in Leistungzusammenstellung Me 109G, here :
http://kurfurst.allaboutwarfare.com/...ragitems_table
The 109K-6's speed with the internal wing MK 108 cannons is given as apprx. 10 km/h slower than the K-4's at altitude.
Overall, it doesn't occur to me using gondolas were any heavier or draggier than using internal armament which would have resulted in some distruption of the aiflow near the surface, and some additional blisters on the wings. The gondolas may have been of greater surface area, but they pushed the gun well below of the boundary layer and probably made up for their greater size by causing less turbulance in the airflow. This was probably a very deliberate choice by Messerschmitt, who probably considered the need for such a heavy firepower involving three fast firing 20mm cannons only required in special cases, as so opted for removable gondolas which does not seem to hurt performance any more than internally placed cannons. When carrying gondolas, the early Me 109Gs could match the FW 190's firepower, as well as speed at altitude, rate of climb and turn.
PS : Spanish 109G 'Buchon' airframes had carried Hispano cannons inside the wings, so it was certainly technically possible..
Kurfürst! - The Messerschmitt Bf 109 Performance Resource Site
http://kurfurst.allaboutwarfare.com/