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 Author  Topic: KEEL FIN?
  Steve Tuhy

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Steve Tuhy   Send Email To Steve Tuhy Posted on: May 2, 2011 - 11:25pm
AFTER VIEWING "PT BOATS- THE GIANT KILLERS" SEVERAL TIMES, I HAVE A QUESTION ABOUT SOMETHING I SAW IN PART THREE OF THE VIDEO. WHEN ELCO FACTORY CREWS WERE TESTING THE NEW 80' BOATS I NOTICED A SMALL FIN LIKE PROTRUSION ON THE KEEL ABOUT TEN FEET BACK FROM THE BOW. CAN ANYONE TELL ME WHAT THIS THING IS? MY GUESS IS THAT IT'S A FACTORY OWNED SPEED SENSOR REMOVED BEFORE DELIVERY, BUT ITS JUST A GUESS.

Steve Tuhy

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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: May 3, 2011 - 12:54am
Thanks for pointing that out Steve, Dick and Al's Elco 80' drawing DVD has a fin drawing for PT's 163-174 and I wondered if they were actually used. The drawing shows it located 7" aft of frame 9 (162" aft of the hull's forward point). The stainless steel triangular fin measured about 13.25" on the forward edge and 22.125" on the aft edge with a 90 degree bottom angle radiused 1".

The drawing does not state its use but I'm guessing it was a turn fin. It doesn't show any kind of mount for other hardware.



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Steve Tuhy

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Steve Tuhy   Send Email To Steve Tuhy Posted on: May 3, 2011 - 1:18am
JEFF, I'M NOT SUPRISED. IT SEEMS THAT THE RON 10 BOATS WERE THE MOST HEAVILY MODIFIED BOATS IN THE FLEET.
YOU CAN ALMOST DATE THE PHOTOS BY THE FIELD ADAPTATIONS THEY USED. STILL, IT'S AN INTERESTING PEICE OF HARDWARE.

Steve Tuhy

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Steve Tuhy

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Steve Tuhy   Send Email To Steve Tuhy Posted on: May 4, 2011 - 2:41am
JEFF;
I JUST REVIEWED PART ONE AND THE FIN IS ON THE 487 BOAT.
LOOKS LIKE ITS CLEAR OF THE WATER AT ABOUT 25-30 KNOTS. DO THE DRAWINGS SHOW WHEITHER ITS A FIXED FIN OR STEERABLE? I'VE NEVER SEEN THIS BEFORE, SO I'M REALLY CURIOUS ABOUT IT.

Steve Tuhy

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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: May 4, 2011 - 5:43am
I'm not sure about PT 487 but the fin is fixed on the 163-174 drawing.

Can you tell if PT 487 had the Elcoplane setup installed at the time the video was shot? I can't tell from the clip I have. Maybe they were trying to get it to turn better. The fin would help the bow grab in a hard fast turn.



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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: May 4, 2011 - 7:01am
I checked Dick's Administrative Guide and didn't see anything on the fin but it has some great information on the Elcoplane staring on page 91. here's a couple of excerpts from it, the book has a lot more info and images: http://www.gdinc.com/Preliminary_Admin_History_PTBoat.html

The fastest run ever made by any PT and the quickest turns ever made at high speed were undoubtedly accomplished by Elcos PT 487, which hit 55.95 knots during trials for the Board of Inspection and Survey, and made a 180 degree turn at top speed in about six seconds - a turn so fast that at its completion the boat had sternway on! The secret of this amazing performance was the addition by Elco of five steps to the bottom of a standard eighty foot boat. 21

The tests on the boat took place on 26 December 1943, and although this was the first time that a PT had ever been equipped with Elcoplanes, as the steps were named, the principle of multiple steps on Elco boats had been conceived more than thirty years before. On 14 January 1913, Irwin Chase, Elcos design genius, was granted a patent for a hydroplane-boat which was a boat comprising a buoyant hull having an unbroken surface skimming hydroplane, secured to said bottom surface . . . The sketches accompanying the patent show a boat with a series of steps similar to those employed on the PT boat thirty years later. 22
22. U. S. Patent 1,050517.


The tests showed the Elcoplane was not ready for prime time:

After considering the results obtained with PTs 560-563 on the Florida trip, as well as the report of the rough water trials of 487, BuShips held up its projected kit-construction program pending a final decision, and on 4 March 1944, the Bureau decided to abandon the project altogether: In view of the experience with motor torpedo boat PT 487 together with that gathered during the shakedown of PT 560-563, the Bureau was of the opinion that multi-steps as installed on these five ships had not been developed to a sufficient degree of effectiveness to warrant further experimentation by the constructor at Government expense. 30 An experimental installation of Elcoplanes on a Higgins PT, PT 485, also proved unsuccessful. 31
30. BuShips C-PT450-545/S1-3(516f); 4 March 1944.
31. Higgins Industries, Inc. ltr. to BuShips with SupShips endorsement; 6 May 1944.


Check out an early Elcoplane design in the .pdf files here:
http://www.boatdesign.net/forums/boat-design/elcoplane-10278.html



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