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Forum Category: PT Boats of WWII
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Forum Name: PT Boats - General
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Topic: Speed of PT Boats?
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?cid=101&fid=102&tid=3265



I was under the impression that on a clean boat it was around 40+ knots. In the Elco Rudders post a few days back talked about a 55 Elco and a 78* Higgins in a race on July 4 1945 doing 75 mph. During the Plywood Derby a Huckins was 33.8 knots while a 77 Elco was at 39.7 knots. On top of that I've read where a boat encrusted with sea life couldn't outrun japanese destroyers. I realize other factors involved such as a clean boat , calm sea and weight , but there's a big difference between 30 mph and 75 mph. What do you guys think?



Posted By: Bob Butler | Posted on: Jul 12, 2013 - 1:16pm
Total Posts: 192 | Joined: Mar 23, 2013 - 11:58am



Bob, no PT BOAT during WWII has ever reached a speed of 75 MPH. I have original time trials from Lt. Cmdr. Alan Montgomery, who was in charge of the PT SHAKEDOWN in Miami, Florida. These trails were conducted with the Higgins Hellcat, which was PT-564, another Higgins, PT-295, and PT-552, an Elco eighty-footer. In one test Montgomery has written down for the measured mile, a top speed of 48.25 knots for the Higgins Hellcat, 46.39 knots for PT-295, and 51.30 for the Elco. Now this was just one test, and his book has many different entries, but from what I can see, the top speed for any boat that was entered into his book was 56.30 knots for the Elco with Elco planes installed, and 53.80 knots for the Hellcat. I don't know for sure how fast that is in MPH, but I know it's not 75 MPH, and those were the fastest boats produced. There are many other entries, and I have two of his original pocket notebooks, so it is possible those boats may have gone faster in other tests.



Posted By: Frank Andruss | Posted on: Jul 12, 2013 - 3:01pm
Total Posts: 3964 | Joined: Feb 9, 2007 - 11:41am



56.3 knots is 64.79 mph.



Posted By: Bob Butler | Posted on: Jul 12, 2013 - 3:41pm
Total Posts: 192 | Joined: Mar 23, 2013 - 11:58am



YEAH!!! GO ELCO!!!!!
Take care,
TED



Posted By: TED WALTHER | Posted on: Jul 12, 2013 - 4:20pm
Total Posts: 2932 | Joined: Oct 16, 2006 - 7:42am




I was under the impression that on a clean boat it was around 40+ knots. In the Elco Rudders post a few days back talked about a 55 Elco and a 78* Higgins in a race on July 4 1945 doing 75 mph. During the Plywood Derby a Huckins was 33.8 knots while a 77 Elco was at 39.7 knots. On top of that I've read where a boat encrusted with sea life couldn't outrun japanese destroyers. I realize other factors involved such as a clean boat , calm sea and weight , but there's a big difference between 30 mph and 75 mph. What do you guys think?



Ahoy there.

I wonder if the 75 mph comes from the old PT boaters' song:

"Oh, some PTs do seventy-five
And some do sixty-nine.
When we get ours to run at all
We think we're doing fine."

(From PT-109 by Robert J. Donovan)

Cheers from Peter


"Give me a fast boat for we want to get out of harm's way too."

Posted By: PeterTareBuilder2 | Posted on: Jul 12, 2013 - 6:28pm
Total Posts: 204 | Joined: Dec 8, 2012 - 6:03pm



Peter;

65 Knots = 74.9 MPH
Speaking from my experience in later day fast boats, YES, this can be attained on a world war two PT BOAT, with a totally cleaned hull and religiously tweaked engines.
TED



Posted By: TED WALTHER | Posted on: Jul 12, 2013 - 7:20pm
Total Posts: 2932 | Joined: Oct 16, 2006 - 7:42am



It's all kind of esoteric. What mattered most was operational speed with a war load. . .

Will

Posted By: Will Day | Posted on: Jul 12, 2013 - 9:57pm
Total Posts: 1954 | Joined: Oct 8, 2006 - 4:19pm



From the British

1 Mile = 5,280 Feet (statute mile)

1 Sea Mile = 6,080.20 US Feet or 6,080 feet Great Britain

IE; 10 Knots = 10 Sea Miles

In case anyone's interested.

D.buck

Posted By: David Buck | Posted on: Jul 13, 2013 - 1:04am
Total Posts: 332 | Joined: May 4, 2008 - 2:59am



You forgot the most important one David

10 NM = 2 Cups of Tea ( North Atlantic in February substitute Kye for Tea)



Posted By: Iowabrit | Posted on: Jul 13, 2013 - 6:52am
Total Posts: | Joined: Unregistered



We used to have races when we would sight land at the base coming in off patrol. That was a good time to race because of less fuel weight. We did not have M.P.H. gauges so don't know how fast we were going. I'd guess 35 - 40 knots at the most. Elco's were usually faster especially the 77 footers. In races our engineers would remove the air mesh covers to the super chargers. The additional air to the carburetors would give 1 to 2 inches more manifold pressure. With that secret we could outrun most Higgins. Also the crew would all get on the bow to make the boat plane out better.

C. J. Willis

Posted By: CJ Willis | Posted on: Jul 13, 2013 - 3:20pm
Total Posts: 464 | Joined: Nov 5, 2006 - 5:02pm



Bob,
It was Maury Hoopers story. PT238. They intentionally disabled the overspeed cutout on the engines and the engines were turning 3300 rpm. The Packard engines were so overbuilt they could easily handle that much rpm over their limit. I have also heard that some boat motor macks would spray a water mist into the carbs to mimic "war emergency" power like on an aircraft engine. (Overspeed trip setpoint is 2950) Frank, your speed test data on the Higgins Hellcat was limited to a top engine rpm of what? 1850 rpm? I know on the boat acceptance INSURV trials that is the maximum rpm they would test the engines to. There is your improper assumption. These guys racing the boats were in it for some serious bragging rights, plus a little cash I would imagine, So you figure it out, 3300 rpm using 26x26 inch props. All Maury knows is that the 10 mile course was completed in 8 minutes. OK all you doubting thomases, do the math! Higgins rule the seas! Way faster than those slow barely turnable Elco boats! Jerry

Jerry Gilmartin

Posted By: Jerry Gilmartin | Posted on: Jul 15, 2013 - 12:33am
Total Posts: 1294 | Joined: Oct 8, 2006 - 11:16pm



I really didn't mean to open a bag of worms, well maybe just a little...



Posted By: Bob Butler | Posted on: Jul 15, 2013 - 9:16am
Total Posts: 192 | Joined: Mar 23, 2013 - 11:58am







Posted By: Bob Butler | Posted on: Jul 15, 2013 - 9:16am
Total Posts: 192 | Joined: Mar 23, 2013 - 11:58am



Jerry, I really have to dig out Montgomery's other notebook from when he was conducting speed trials in Miami. Let's see here, in one entry in the book, he used PT-295 and PT-552, both using W-14 Packards. PT-295 is using 29/26 Props, while PT-552 is using 28/29. Three runs are made with a full war load and 2,000 gallons of fuel.

Run 1 PT-295 44.010 Knots PT-552 45.113
Run 2 PT-295 43.690 Knots PT-552 45.000
Run 3 PT-295 44.227 Knots PT-552 45.456
------------------------------------------------------------------------------------------------------
There was no RPM's given for this one test. In anther entry Montgomery writes down he also conducts a test with PT-487 using three runs with different RPM'S. For instance at 2,786 rpm, the boat produced a speed of 52.13 knots for the first run, the second run at 2,832 rpm. produced a top speed of 54.17 knots, and the third run at 2,695 rpm's produced a top speed of 51.30. I will not argue the point that in the war zone the motor macs were always trying to gain more speed, but I still never heard of any of the boats doing 75mph. Test's do not say altogether if they were carrying a full war load or how much fuel. Montgomery writes down in yet another entry in his book PT-487 doing 52.98 knots at 2, 670 rpm's. The boats never gave you the same speed in each run.



Posted By: Frank Andruss | Posted on: Jul 15, 2013 - 12:14pm
Total Posts: 3964 | Joined: Feb 9, 2007 - 11:41am