Square hole aft of antennae opening on Zero canopy, why?

[GeoffSteer]

Hello-

  I am currently building 3 1/32 scale Zeros using two Tamiya A6M2s and two A6M5s. I am using the cockpit from one A6M2 to add to the other A6M2 to produce an A6M2 K which, is just about complete. The left over wings from the cockpit donor will be used on one of the A6M5s to backdate it to an A6M3 Hamp. The other A6M5 will be built out of the box (hard to imagine such a thing!). All the canopies in these kits have a rather pronounced square opening aft of the antennae opening. The instructions never show anything being put into this hole. I was guessing it may have been a vent hole for the gun's gasses that are in the cockpit with the pilot who would likely appreciate those gasses having some place to exit. However, I have yet to find a photo that shows this hole on an actual aircraft.  Any ideas as to why Tamiya put these holes in this location?

With thanks-

Geoff Steer

[Martinnfb]

Edited April 6 by Martinnfb

[Martinnfb]

[Finn]

Maybe another place for an antenna wire:

 

 

 

 

Jari

[Hubert Boillot]

No idea what this is for, but Martin and I had recently an exchange about the removed panels on the rear of the Curtiss Seahawk’s canopy. This was to reduce some buffeting encountered when the canopy was open, a US Navy safety rule for take-offs and landings. Could it be the same for the Zero ?

 

Hubert

[Oldbaldguy]

11 minutes ago, Hubert Boillot said:

No idea what this is for, but Martin and I had recently an exchange about the removed panels on the rear of the Curtiss Seahawk’s canopy. This was to reduce some buffeting encountered when the canopy was open, a US Navy safety rule for take-offs and landings. Could it be the same for the Zero ?

 

Hubert

Very likely.  The rear part of the canopy would be nothing more than a big draggy air scoop with the slider open - all that captured air has to go somewhere or it starts doing weird and unexpected things.

[CRAZY IVAN5]

7 hours ago, Oldbaldguy said:

Very likely.  The rear part of the canopy would be nothing more than a big draggy air scoop with the slider open - all that captured air has to go somewhere or it starts doing weird and unexpected things.

I think you guys are right on that . The only reference I can find is in the Aero Detail 7 on page 56 where they call it out as for ventilation . It seems that it changed shape through the versions too. I'm going to speculate here [ I'm a mechanic not an engineer], that originally the opening was for the early radio /antenna configuration[ 2 wire] and when this went away the opening was left. Perhaps they tried to close it off and it ran into buffeting issues [which would make sense] so they opened it back up with ventilation being a side benefit, AGAIN ONLY SPECULATION. It's curious to note that in the Aero detail 7 there's an A6M7 pulled from a lake and it shows the aft canopy being closed off[?],page 15 pic number47. For what ever it's worth the hole was here from the 47th machine on along with a change in the canopy configuration page number 56. On page 57 there's a drawing of the aft canopy of the -K and it shows there being an opening but of a different shape so apparently the trainers had it too. Which again would make sense from a buffeting /ventilation point of view.