The PT Boat Forum
http://www.ptboatforum.com/cgi-bin/MB2/netboard.cgi

» Forum Category: PT Boats of WWII
http://www.ptboatforum.com/cgi-bin/MB2/netboard.cgi?cid=101&fct=showf

» Forum Name: PT Boats - General
http://www.ptboatforum.com/cgi-bin/MB2/netboard.cgi?fct=gotoforum&cid=101&fid=102

» Topic: Audibility Test Data for Elco and Higgins
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?cid=101&fid=102&tid=3714

---

Hi All,

Does anyone have any info on exhaust noise level charts/info for the Elco and Higgins?

My understanding is that early on (in order to validate noise level requirements), both boats received audibility tests at a speed of 10 knots on one, two and three engines both with and without mufflers. With mufflers, the exhaust noise was required to be inaudible at ranges greater than 800 yards on a still night.

Also that both boats suffered from manifold back pressure above 1200 rpm with the mufflers. So were the boats ever tested at speeds greater than 1200 rpm with mufflers? If so, does anyone have the manifold pressure or back pressure measurements/readings? or info on how long a boat could operate at these higher speeds if required?

Thanks!
Andy



Posted By: Andy Small | Posted on: Nov 4, 2014 - 10:43pm
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm

---

Andy;
I would say these are 1942 tests you are looking for, the RON 3 boats went into combat with no mufflers, I don't know if this was as a direct result of lessons learned by RON 3, or it was in planning already and was solidified after Bulkeley and Kelly returned and gave lessons learned in "post deployment debrief".

while not really answering your questions, here is some added info:
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?fid=102&cid=101&tid=2113&st=0&nd=10&pg=41&sc=20

Take care,
TED



Posted By: TED WALTHER | Posted on: Nov 5, 2014 - 6:24am
Total Posts: 3059 | Joined: Oct 16, 2006 - 7:42am

---

This 10 knot/800 yard spec was from BuShip's Special Specification for Propelling Machinery for US Motor Torpedo Boats PT71-102 of Dec, 10, 1941. So to meet the first new batch of PTs (Oct 41 order) after the Plywood Derby tests and before Elco received their Jan 42 order for the first 80' Elcos. I'm assuming this spec , or the lack of meeting it, lead to the Higgins muffler and eventually the Huckins internal muffler (which worked extremely well but was only installed on PT 257 - interesting story there....). I also assume that feedback from the Fleet (quite a bit of BuShips/ Ron 4 letter activity in the Summer of 42) coupled with pointers to this spec led to the famous Elco muffler system.

I'm trying to establish a rough noise level baseline for the three boats These test would have been far from super accurate. The BuShips test for the Huckins (PT 95) used 2 observers to independently record detection of the boat on a set distance range. In July 42, the unmufflered Huckins recorded an average audibility of 876 yards on all three engines, but was much louder on 1 or 2 engines.

Andy



Posted By: Andy Small | Posted on: Nov 5, 2014 - 9:22am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm

---