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 Author  Topic: PT-3 Information
Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 24, 2014 - 2:12pm
All,

On Monday I took a day off and drove down to NJ to see PT-3 and take photos and measurements. She's in sad shape, but still very original and I was very impressed at this George Crouch designed craft and have tried to capture much of what I found in my drawings. Considering that the US Navy really had no idea what they wanted at the time of her contract, she did directly addressed the severe weight (transportation) requirements and incorporated many advanced features.

Some noteworthy design features.
- oak steam bent framing spaced every 10 and continues through barrel back.
- curved tumble home provides strength and stiffens hull, and eliminates normally weak deck edge to hull transition.
- double longitudinal planking provides lightweight strength and eliminates additional weight requirement of sandwiched cloth/canvas.
- use of carriage bolts to secure planking to lightweight framing, allows crew to tighten hull from inside.
- combination of framing structure with planking provided a very strong and mildly flexible hull.
- hull form is a warped plane design and overall narrow in design, but keeping the stern wide, in comparison to midships, seems to have minimized suction and stern squatting. Photos indicate that boat lifted up on step at a constant angle. As fuel consumed, weight would shift slightly forward.
- used two Packards for power (first PT Boat with these)
- muffler system (although huge)

You can understand why this small boat was considered obsolete once the Navy figured out what they didn't want (stern fired torpedoes), but I believe she was an important design worthy of note in PT Boat development and exceeded the designs of newer boats in frame and hull construction and showed the experience of George Crouch.

I have not seen any actual USN sea trial results, and will add this to my list of items to research when next down at the National Archives, Anybody already have this info?

Merry Christmas and Cheers!
Andy


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 24, 2014 - 2:29pm
Assuming PT-3 finally gets a sponsor for restoration. Are there any folks in the NJ area that would/might be able to assist during the restoration? Guess it comes down to what sort of support she might receive.

While she fired no shots in anger, she was the first, and she did go to war 8 months before the US. I believe she may also be the sole surviving UK/Canada Lend-Lease boat.

Being relatively small with potentially two Packards, it seems she would be a bit easier on the pocket book to operate, but would still have that great sound. Also, her mahogany planking and art deco design would look great in varnish and would show off her unique construction.

Be nice to have a PT on the East Coast again.

Andy


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 26, 2014 - 3:50pm
Here's an update of my PT-3 drawing.

- Andy

 photo pt3_profile_feb15_zpsvg65wosw.jpg

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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 27, 2014 - 4:41am
Here are photos showing PT-3's wood construction:

The fore-aft longitudinal bottom planking that shapes the chine location. Outer and inner
planking seams overlap and planking is screwed together from the outside and inside. It is
probable that glue is also applied between the layers.
photo

Here is the fore-aft side planking that continues up the barrel back. The planking transitions
to plywood at the deck.
photo

Here is a butt joint. You can just make out the four carriage bolts. These are attached to
a butt block on the inside located between the frames which are spaced every 10 inches.
photo

Here is a butt joint revealing the carriage bolts.
photo

Here is a butt block. Carriage bolts may be tightened if required. Photo also shows part of
a forward framing.
photo

Photo shows the forward keel to keelson transition. The inner portion of the frames are bent
laminated oak and an addition piece of oak is applied to the outer portion of the frame.
Carriage bolts and screws hold the frames together. Carriage bolts are also used to hold
the stringers to the outer planking (sheared bolts are visible in line with the stringer).
photo

Here is the framing at the chine. Every third frame is reinforced. Also visible is another butt block.
photo

Here is the forward framing showing the high chine and the most forward portion of the
barrel back. Also shows several gussets and the deck framing and stiffener as well
as the plank to plywood deck transition.
photo

Here is the side framing with gussets and frame reinforcement every third frame. Also
visible is the deck framing/joints and plank to plywood deck transition.
photo


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 27, 2014 - 9:33am
Here are some photos of the engine compartment. For this design, the Navy required the engines to be mounted on a steel frame. In order to accommodate the engines, boat uses some sort of "v" drive. PT-3's engine compartment construction has a forward and aft steel bulkhead with engine hoist. Hull and deck framing is wood. Believe original engine deck access hatch is missing.

Port replacement diesel and what looks to be the original drive - looking aft.
photo

Stern engine room access added by former owner. Center fuel tank removed to allow this access.
photo

Looking down into the bilge area of the aft bulkhead.
photo

Looking forward at the engine room access. Wood door behind is the opened door to the head.
photo

Starboard engine hoist (wood hull framing in background).
photo

Starboard engine hoist looking forward. Engine compartment access hatch to the upper left.
photo

Starboard side of engine room looking aft (aft bulkhead) with cables.
photo



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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 29, 2014 - 8:37am
Here are my estimates and comments (opinion) on PT-3s hull design.

Based on measurements, I came up with an at rest aspect ratio of about .25 and an on-step (plane) aspect ratio of about .34.

The hull is relatively straight chine aft of midships (widest part and transom only differ by 2 ft) and the back portion of the hull only has a slight change in deadrise. The hull is also not concave in form, so together I would expect suction loads to be on the lesser side and would not expect to see much squatting of the boat on plane. Trim angle on plane (from photographs) estimated at about 2.5-3.

Because of the position of the fuel tanks (aft) and the weight of the engine room steel framing and engines, the center of gravity (CG) for PT-3 is pretty far aft. The center of buoyancy (CB) is guestimated at about 23-21 feet from the transom. As she starts to plane, CB would move aft and probably move very close to the boat's CG which I believe to be about 20-18 feet from the transom.

She probably rides very well on glass calm based on other George Crouch designs. Deadrise is good at entry indicating potential for a smooth ride, however, in rougher sea states, her lack of a deep forefoot would probably result in some pounding forces, although the steep deadrise and slight convex shape of the bow would help. Having such a large hull sail area out of the water forward would probably make PT-3 very susceptible to beam wind forces when on plane. When operating at lower speeds, the CG being aft of the CB would probably make PT-3 susceptible to yawing motions in following seas. As for turning, she was probably good at slower speeds, but would suffer a bit at higher speeds due to not having the forefoot in contact with the water.

I have no idea what PT-3s actual hump speed is. Probably somewhere about 20 kts (WAG). Even with the steel framing in the engine room, weight saving building techniques are obvious, so she was intended to be a planing hull design.

This is a fun project to try and figure out this boat with lots of missing info. Hopefully the national archives will have some great PT-3 test info and not prove that I'm not totally full of crap As my personal email signature states "A little bit of knowledge can be a very entertaining thing".



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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: Dec 30, 2014 - 3:50am
Great line:

A little bit of knowledge can be a very entertaining thing.

Thanks for the information on and images of this little known PT boat Andy.



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ROSS FISHER

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of ROSS FISHER  Posted on: Dec 30, 2014 - 10:43am
Andy,
Though her present condition is pretty sad, what a great opportunity it was for you to view this early transition design to the wartime boats.
In 50,000 words or less, what do you feel were the major advantages and disadvantages of the Huckins boats as opposed to the Higgins and Elco boats. (that led the Navy to concentrate on the other designs).

Ross Fisher

ross@dupagels.lib.il.us

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bubbletop409

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of bubbletop409  Posted on: Dec 30, 2014 - 9:04pm
Ross

I believe PT-3 was built from a George Crouch design but don't think Huckins was involved in any way. The Huckins entries were built on a design of their own after PT-3 was operational.

Larry
62 Bel-Air
260 Eagle EXP
79 Cole TR-2

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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Dec 31, 2014 - 6:29am
I believe Ross was asking if I've done similar comparisons of the Elco, Higgins and Huckins hull forms and construction, which I have. There are many views on this topic, but here are my initial thoughts on US PT Boat hull development:

This time frame from 1937 till 1944 was an exciting time for this new branch of naval architecture. So little was really known and the collective was trying to figure things out and solve urgent problems. As the war wound down, planing hull advancement completely departed the US Navy pattern and shifted back to the civilian pleasure and racing market, which eventually led to planing designs such as the smoother riding, but more fuel consuming deep V designs. The US Navy instead concentrated their experimentation on various new forms of small craft (fully submerged supercavitating hydrofoils, surface effect ships, and multihull designs). Other than the brief PHM deployments, the USN doesn't seem to have much staying power, or interest in deploying small cutting edge vessels (concentrating more on the more important bigger stuff), and has left the actual tactical use/development to other nations.

I will open a new thread on this once I have collected my thoughts, but in the meantime I recommend the book Naval Architecture of Planing Hulls by then LCDR Lindsay Lord, USNR. With a Doctorate in Naval Architecture and professor from MIT (as Scott Adams calls, a deviate smart person), he was the preeminent US SME on planing hull design before the war. The USN was smart enough to quickly commission him an officer and assigned him to the repair facilities at Pearl Harbor specifically to evaluate and conduct experimental planing hull work. While there, he took this unbelievable opportunity to collect first hand data, conduct hull form tests, and recorded his finding and evaluations in a manuscript submitted for publication by early 1944. (You may find portions of the 3rd edition of the book online, but my virus protection did not like the full zipped download I found - I have the 1st edition hardcopy. You can also find a short Lindsay Lord planing hull discussion in the post war series Practical Boat Building Volume 34 by Motor Boating).

Unfortunately, I can find no evidence that BuShips used any of Lord's research and def none was applied to the 4 experimental PTs constructed after the war. Also reference to his work is completely absent from post war lessons identified/learned. In my opinion, the PT Boat unofficially program died at this point. The design process shifted back to the standard US Navy approach of design by committee and opinion. Meanwhile Lord's studies and writings changed surfing history and probably influenced foreign (non-UK) patrol boat design. If I had unlimited funds at my disposal, I would want to test Dr Lord's monohedron design principles by building a full size version of his high speed monohedron torpedo boat design and then go trolling for some Elcos, Higgins, Huckins, and Vospers for lunch

Andy




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