Malcolm hoods on FAA Hellcats...

[Edgar]

Not sure what Occa is getting at,

Me neither, since it was actually the reference to the "centre frame" that has me foxed.

[occa]

For a dummy, like me, that requires further explanation, please.

You said that photo has all the appearance of a standard 'blown' (I assume Hellcat) hood ...

A standard Hellcat hood has an additional canopy frame on the center, that in the photo (in the OP post, you seemingly were referring to) has not.

Here the vertical center frame I mean can be seen:

http://en.wikipedia.org/wiki/File:Grumman_XF6F-4_Hellcat.jpg

I just don't understand, were there 'standard Hellcat blown hoods' (without said center frame) that were not Malcolm hoods?

[occa]

HI Edgar

....

Not sure what Occa is getting at, maybe that this is some kind of non standard Hellcat canopy, which I think we are all agreed it is, though not technically an actual Malcolm hood though, but more likely a Westland[?] blown hood?

Yes that is what I meant, overlooked you all had agreed to it already, sorry guys, my mistake.

[Troy Smith]

You said that photo has all the appearance of a standard 'blown' (I assume Hellcat) hood ...

A standard Hellcat hood has an additional canopy frame on the center, that in the photo (in the OP post, you seemingly were referring to) has not.

Here the vertical center frame I mean can be seen:

http://en.wikipedia.org/wiki/File:Grumman_XF6F-4_Hellcat.jpg

I just don't understand, were there 'standard Hellcat blown hoods' (without said center frame) that were not Malcolm hoods?

Right, a standard Hellcat hood is NOT a blown hood.

Edgar was pointing out that a Malcolm hood was bulged at the top, but not the sides, because it needed to be taken off a male mould, while a blown hood, as it has bulged sides and top can't be made that way.

Am I reading you correctly Edgar?

[Jon Kunac-Tabinor]

but are there any more pics though?

Jonners, eager LOL

[occa]

Right, a standard Hellcat hood is NOT a blown hood.

Edgar was pointing out that a Malcolm hood was bulged at the top, but not the sides, because it needed to be taken off a male mould, while a blown hood, as it has bulged sides and top can't be made that way.

Am I reading you correctly Edgar?

The word 'standard' in Edgar's quote is what got me confused, he called the one in post #1 a standard 'blown' hood.

So for the Hellcat there were standard Hellcat hoods (the norm), the rarer standard blown (Hellcat) hoods and possibly Malcolm hoods?

Btw as far I recall correctly the Malcolm hoods for the Mustang were blown everywhere, on top AND on the sides.

Probably it is not so important anyways ... sorry for the thread digression

[Graham Boak]

I believe that Edgar is describing the first Malcolm hood as applied to the Spitfire, replacing the initial flat-top standard. Later Spitfire hoods were blown, as were the Malcolm hoods on the P-51, P-47 and F6F.

Edited November 11, 2014 by Graham Boak

[Edgar]

Am I reading you correctly Edgar?

Spot on, thanks.

Btw as far I recall correctly the Malcolm hoods for the Mustang were blown everywhere, on top AND on the sides

As I said, the early Malcolm hoods (produced about 15 miles from here, and used on the Mustang III/B/C) were not blown, but pulled.

Hoods on the D/IV Mustang (which were blown) were not supplied by Malcolm.

.

[occa]

I meant the Malcolm hoods on the Mustang B/C not those on the D model which of course I am aware are fully blown to all sides and were not Malcolm hoods.

I have no idea how they were made (pulled or blown or through a different method) but those on the B and C were lets call it 'bulged' to the sides AND to the top like this photo proves.

http://www.flickr.com/photos/oldbuckshots/8519865195/

That picture shows a so called Malcolm hood, or?

I should have used 'bulged' from the start instead of 'blown', maybe that's where another confusion came from.

I was referring to the appearance not to the making process.

The point I wanted to make is this:

Troy said:

Edgar was pointing out that a Malcolm hood was bulged at the top, but not the sides, because it needed to be taken off a male mould, while a blown hood, as it has bulged sides and top can't be made that way.

Which Edgar confirmed was meant that way ^^ indeed, so I have interpreted that correctly.

That just seems not to be the case with the Malcolm hoods for the B/C/III Mustang like the photo of the P-51 above proves.

[Graham Boak]

A canopy with bulging fore and aft may indeed be difficult to pull from a mould (re Edgar post 3), but there's no problem in principle. To do so when the bulging is in the vertical is quite another matter. (Or, of course, in whatever axis is being used to pull the piece from the mould.) It is my understanding that these canopies were, at their widest, wider than their mountings on the sliding frame. Isn't this also seen on the Spitfire canopies of the same vintage? If this is so, then pulling will not work once the material was rigid, and whilst hot it would not retain the desired shape after being distorted by the release.

However, the flexibility of the material at intermediate temperatures may be relevant. The earlier Hurricane canopy flexed as it was slid, but thicker material was being used by this time. It seems exceedingly unlikely that the cold canopy could be removed without damage, but perhaps there was some warm state at which the canopy could be flexed sufficiently to remove it from the mould and yet revert to the moulded shape whilst cooling further.

Alternatively, it may be possible to arrange some kind of multipart tool, reducing the width of the mould to permit release, but I've not seen this described anywhere and it would introduce its own problems. It wouldn't fit Edgar's description.

[tempestfan]

Alternatively, it may be possible to arrange some kind of multipart tool, reducing the width of the mould to permit release, ..

I always suspected slide moulding was not invented by Dragon...

Another slight digression, but didn't the canopy of the Fw 190 also need to flex due to the converging canopy rails ? And - about which thickness of material (acrylic glass, I assume) are we talking ? I'd imagine an open structure (open at both ends, that is) of, say, 4 to 5mm would allow some flexing to get it off the mould without causing cracks or stress marks.

[Jon Kunac-Tabinor]

well while you all discuss slide moulding.... back to the matter in hand.

Here's where Im at: ( model is Eduard's 1/48th Dash 5N)

Jonners

[occa]

A canopy with bulging fore and aft may indeed be difficult to pull from a mould (re Edgar post 3), but there's no problem in principle. To do so when the bulging is in the vertical is quite another matter. (Or, of course, in whatever axis is being used to pull the piece from the mould.) It is my understanding that these canopies were, at their widest, wider than their mountings on the sliding frame. Isn't this also seen on the Spitfire canopies of the same vintage? If this is so, then pulling will not work once the material was rigid, and whilst hot it would not retain the desired shape after being distorted by the release.

However, the flexibility of the material at intermediate temperatures may be relevant. The earlier Hurricane canopy flexed as it was slid, but thicker material was being used by this time. It seems exceedingly unlikely that the cold canopy could be removed without damage, but perhaps there was some warm state at which the canopy could be flexed sufficiently to remove it from the mould and yet revert to the moulded shape whilst cooling further.

Alternatively, it may be possible to arrange some kind of multipart tool, reducing the width of the mould to permit release, but I've not seen this described anywhere and it would introduce its own problems. It wouldn't fit Edgar's description.

I always suspected slide moulding was not invented by Dragon...

Another slight digression, but didn't the canopy of the Fw 190 also need to flex due to the converging canopy rails ? And - about which thickness of material (acrylic glass, I assume) are we talking ? I'd imagine an open structure (open at both ends, that is) of, say, 4 to 5mm would allow some flexing to get it off the mould without causing cracks or stress marks.

I too think it would be possible to straddle it and therefore release it from a 3D mold, even bulged steel sheets are flexible to a degree ...

[Jon Kunac-Tabinor]

OK - the funny thing here chaps is that it was OBVIOUSLY possible - because it was done. Its a bit like discussing whether Stone Henge was possible to be built - and kind of ignoring the bloody big stones standing in a circle behind you.

So perhaps while we all ponder on how it was done, could we get back to the matter hand - ergo - theres photographic evidence it existed, but do we have any more pics?

Jonners - wanting to build a model of the bleedin' thing

[Troy Smith]

HI Jonners

I think the pics have been posted, one still up, the other posted by IanG but now deleted, which did show more.

Here's a photo of a Hellcat II(NF) on Ocean. I agree with Tony that this is likely to be KD110, as according to Sturtivant this aircraft 'went over starboard side onto walkway' on 27.11.45. No other 892 squadron Hellcat accident description fits what can be seen in the photo.

Zero length rocket rails, and 20mm cannon with a blown hood.

You might want to PM him and ask it be put back up, or if he has any more info in his files, than what has already been posted.

Is your blown canopy a scratchbuilt or a modified P-47 hood?

cheers

Troy

[occa]

OK - the funny thing here chaps is that it was OBVIOUSLY possible - because it was done. Its a bit like discussing whether Stone Henge was possible to be built - and kind of ignoring the bloody big stones standing in a circle behind you.

So perhaps while we all ponder on how it was done, could we get back to the matter hand - ergo - theres photographic evidence it existed, but do we have any more pics?

Jonners - wanting to build a model of the bleedin' thing

We are just trying to convince the reality is not always that strict and rigid ...

[John Aero]

Perspex/plexiglas will spring quite a bit if it's not really cold. I would suggest that any of these "bubble" hoods were done by blowing where perspex hot enough to bend is clamped in a moulding frame and then reheated to the right temperature and then pressurized from within. BTW I've just come across a some info that the Spitfire jettisonable hood was developed by Martin Bakers.

John

[Edgar]

According to Vickers, the Martin-Baker hood jettison gear was introduced on the Mk.V with the new hood and windscreen originally developed for the Mk.III. The only photo I have, of the III canopy, shows a double thumb-push style of release.

Edited November 25, 2014 by Edgar

[tempestfan]

OK - the funny thing here chaps is that it was OBVIOUSLY possible - because it was done. Its a bit like discussing whether Stone Henge was possible to be built - and kind of ignoring the bloody big stones standing in a circle behind you.

So perhaps while we all ponder on how it was done, could we get back to the matter hand - ergo - theres photographic evidence it existed, but do we have any more pics?

Jonners - wanting to build a model of the bleedin' thing

I thought it was the way it was moulded that was discussed - "blown" (into a female mould ?) vs. "punch moulded" over a male former.

[tonyot]

Nice job on the canopy Jonners,........I presume that you added the bulge with milliput or something similar to answer an earlier query?

I`ve not been able to find any more info out re individual colours and markings so KD110-S is looking favourite?

Cheers

Tony

[John Aero]

Without wishing to hi-jack. The double thumb catch was the normal way of opening the hood. MB developed the Red rubber ball total hood release which operated a bowden cable which pulled the pins on the hood slides to jettison the lot.

John

[Jon Kunac-Tabinor]

Nice job on the canopy Jonners,........I presume that you added the bulge with milliput or something similar to answer an earlier query?

I`ve not been able to find any more info out re individual colours and markings so KD110-S is looking favourite?

Cheers

Tony

Hi Tony - I used semi circular flanges of plastic card to make the edges, then in-filled with CA & Talc filler and sanded it all out. I'll post a pic of it with the primer sanded out on the upcoming WIP thread.

Yes looks like KD-110 "S" but with that enigmatic man & woman bit of nose art too.

Cheers - excited about this one

Jonners