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ť Forum Category: PT Boats of WWII
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ť Forum Name: PT Boats - General
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ť Topic: 20MM Dual Gun
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I saw a photograph of a nice dual 20MM Cannon set up on one of our WWII Subs. I was wondering if any of the PT Boats carried such a weapon. I do not recall seing this type set up, but that does not mean they did not have them. Maybe it was a weight issue........

Posted By: Frank J Andruss Sr | Posted on: Jan 16, 2009 - 6:25am
Total Posts: 3497 | Joined: Oct 9, 2006 - 6:09am

No Frank,

NOT that I know of ................

BUT knowing me? I'd be wrong.

Posted By: TGConnelly | Posted on: Jan 16, 2009 - 6:50am
Total Posts: | Joined: Unregistered

I wonder why that weapon did not find favor. Seems that with 60 rounds each, it would have put out a ton of lead on enemy planes or surface targets. Like I mentioned in the earlier post, it might have had something to do with extra weight, because it would make since that to support the twin 20MM you would need the heavy Pedestal mount.

Posted By: Frank J Andruss Sr | Posted on: Jan 16, 2009 - 11:19am
Total Posts: 3497 | Joined: Oct 9, 2006 - 6:09am

Frank; I saw lots of PT boats and never saw one with twin 20mm cannons. I recall a study made about the advisabolity of installing twin 40mm's, but weight ruled them out pretty quickly. I suspect that it was more of a "crowd"reason. The foredeck was a beehive of activity during the use of both 20mm and the 37mm. Loaders were constantly rushing about. It would have been chaos with added activity. (one man's opinion)

Posted By: BobPic | Posted on: Jan 17, 2009 - 5:43am
Total Posts: | Joined: Unregistered

Bob

It certainly makes good since. I am sure that if the boats could have handled heavier weapons, they would have used them. The sheer weight of a twin 40MM in the stern might have sunk the darn boat, so I am sure the heavier Pedestal mount for a twin 20MM and the fact of a crowded deck all played a role.

Posted By: Frank J Andruss Sr | Posted on: Jan 17, 2009 - 6:50am
Total Posts: 3497 | Joined: Oct 9, 2006 - 6:09am

I remember the jokes around when they were experimenting with the twin 40's. It was decided they could install twin 40mm's if they removed the engines or fuel tanks. Also I remember that the crew "banned" the skipper from forward of the chart house during general quarters because of the busy conditions. Remember the foredeck of a PT was crowned, sloping toward the edges. No rail of any kind. Deck was painted and slick, especially when wet (all the time). Adding two more loaders would have complicated things.

Posted By: BobPic | Posted on: Jan 17, 2009 - 7:04am
Total Posts: | Joined: Unregistered

"Sloping toward the edges...no rail of any kind..."

Huh?

Are the flat PT boat foredecks I've looked at, in hundreds of photos, for 45 years, optical illusions?

What about the toe rail(s)?

I don't get it. [:-question-:]

Posted By: Drew Cook | Posted on: Jan 17, 2009 - 1:19pm
Total Posts: 1306 | Joined: Oct 19, 2006 - 10:44am

I seem to remember that at least one boat had a twin 20 mm in a turret In place of the usual twin 50. My search for information has been unsuccessful.

I don't remember ever slipping on a wet deck. However, there was a rail about two inches high which was handy for tripping someone and dumping the victim overboard. I do not know if that ever happened.

Posted By: QM | Posted on: Jan 17, 2009 - 2:30pm
Total Posts: | Joined: Unregistered

I didn't mean the deck was rounded but it was sloped toward the edges just to shed the water. I wouldn't have been so conscious of it except we had to repair it and shape the boards. Our deck was slick when wet. The 2" rails were really scuppers and did indeed trip people. We never lost anyone overboard in combat situations but we had a torpedoe man who went overboard several times

Posted By: BobPic | Posted on: Jan 18, 2009 - 8:17am
Total Posts: | Joined: Unregistered

Camber (transverse deck curvature) is a common feature on just about any ship or boat. It is often quite subtle. Here's a section through the forecastle of an 80' ELCO showing the slight curve of the deck.

Al Ross

[IMAGE]http://i73.photobucket.com/albums/i204/alross2/camber.jpg[/IMAGE]

Posted By: alross2 | Posted on: Jan 18, 2009 - 3:51pm
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm

I've never seen any photos or references of the twin 20mm mount being fitted to WWII PTs, although they were fitted to a couple of the four post-war boats (809-812). The standard USN twin mount, the MK24, was actually several hundred pounds lighter than the single pedestal mount MK4 and was mounted on a tripod just a couple inches shorter than the standard MK10 single mount.

The Brits fitted the twin 20mm to a large number of their "short boats". Usually the MKIX pedestal mount, these mounts replaced the .50 Vickers turret on the US built Vospers, were fitted to the 73' Vospers, the 71'9" BPB MTBs (in place of the MKV twin power mount), and amidships on the Higgins PTs transferred to the RN.

Al Ross

Posted By: alross2 | Posted on: Jan 18, 2009 - 4:55pm
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm

Thank You Dr. Ross for your information on the 20MM Mounts.

Posted By: Frank J Andruss Sr | Posted on: Jan 19, 2009 - 6:03am
Total Posts: 3497 | Joined: Oct 9, 2006 - 6:09am

I'm going to have to start acting like Gibbs on NCIS and start whacking you guys on the back of the head... :-) It's Al, just Al.

Al Ross

Posted By: alross2 | Posted on: Jan 19, 2009 - 7:10am
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm