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» Forum Name: PT Boats - General
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» Topic:
PT-3 Information
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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
Posted By: Andy Small | Posted on: Dec 24, 2014 - 2:12pm
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
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
Posted By: Andy Small | Posted on: Dec 24, 2014 - 2:29pm
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Here's an update of my PT-3 drawing.
- Andy
Posted By: Andy Small | Posted on: Dec 26, 2014 - 3:50pm
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
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.
Here is the fore-aft side planking that continues up the barrel back. The planking transitions
to plywood at the deck.
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.
Here is a butt joint revealing the carriage bolts.
Here is a butt block. Carriage bolts may be tightened if required. Photo also shows part of
a forward framing.
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).
Here is the framing at the chine. Every third frame is reinforced. Also visible is another butt block.
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.
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.
Posted By: Andy Small | Posted on: Dec 27, 2014 - 4:41am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
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.
Stern engine room access added by former owner. Center fuel tank removed to allow this access.
Looking down into the bilge area of the aft bulkhead.
Looking forward at the engine room access. Wood door behind is the opened door to the head.
Starboard engine hoist (wood hull framing in background).
Starboard engine hoist looking forward. Engine compartment access hatch to the upper left.
Starboard side of engine room looking aft (aft bulkhead) with cables.
Posted By: Andy Small | Posted on: Dec 27, 2014 - 9:33am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
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".
Posted By: Andy Small | Posted on: Dec 29, 2014 - 8:37am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Great line:
[green]A little bit of knowledge can be a very entertaining thing.[/green]
Thanks for the information on and images of this little known PT boat Andy.
Posted By: Jeff D | Posted on: Dec 30, 2014 - 3:50am
Total Posts: 2200 | Joined: Dec 21, 2006 - 1:30am
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
Posted By: ROSS FISHER | Posted on: Dec 30, 2014 - 10:43am
Total Posts: 82 | Joined: Jul 23, 2008 - 10:03am
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
Posted By: bubbletop409 | Posted on: Dec 30, 2014 - 9:04pm
Total Posts: 164 | Joined: Apr 22, 2013 - 11:48pm
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
Posted By: Andy Small | Posted on: Dec 31, 2014 - 6:29am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Here is an updated drawing with measurements. I still have to complete the forward bow form at some point.
The real good news is that it looks like the PT-3 restoration is going to happen. We are working on the business plan with the owner, as well as working on the 501c3 application and we even believe we have located original class drawings (PTs 1 thru 4) and am hopeful that we will will soon have them in hand! Please feel free to contact me direct.
Cheers,
Andy
Posted By: Andy Small | Posted on: Jan 7, 2015 - 3:03pm
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Original drawings means there are models in the future!!!
Posted By: nahma | Posted on: Jan 10, 2015 - 3:42pm
Total Posts: | Joined: Unregistered
Another update to the PT-3 drawings.
The design and construction are very interesting from the usual PT Boat construction. Other than the boat designation, I really see nothing in common with the later boats. I also really enjoy seeing how an expert race boat designer tackled this project. I find the aluminum framed engine and fuel tank compartments very intriguing and I believe it prevented the usual engine access hatch weak area since the engine room had aluminum bulkheads with aluminum framing on the other four sides tying the whole compartment together and spreading the loading out. It definitely has helped maintain the boat during its latest neglect.
Andy
Posted By: Andy Small | Posted on: Jan 11, 2015 - 11:44am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Last week I made another visit to PT-3 as well as spending several days at the National Archives. Lots of good info on the boat.
PT 1 thru PT 4 based on the 25ft aluminum test model 9. Model was requested for use during training.
Original 3M2500s were left (port engine) and right (starboard engine). These were upgraded to two right 4M2500s in Jan 41. The engine and fuel tank compartment metal framing is all aluminum.
Construction: Considered superior and boat was 10% lighter than contract (light load 38,000 lbs - trial displacement 56,600 lbs). In comparison, sister boats PT-1 and PT-2 built in Miami were about 4,000-6,000 lbs heavier (not sure if this was due to construction or equipment). Items such as the portholes were light weight aluminum and the boat even used a lightweight Northill Anchor (same typed used by seaplanes).
Performance: Boat handled 8-10 ft waves very well and was compared favorably over PT-9's pounding. Boat turned easily on a very close radius and gave a feeling of complete stability in turn (banked very well into turn). At 2000 rpm, boat turned in 4 1/2 boat lengths. Maintained a pretty constant 4 degree trim angle. Hump speed approximately 12-16 knots.
Big problem seemed to be the prop slip, which reduced the HP. At a top speed of 34 knots (2400 rpm with 3M2500s), boat was losing an estimated 450 HP. Two different sets of props were tested (first 25 x 23 and then 26 x 27) a third was requested (greater pitch and increased blade area) for model testing with the tests completed 5 months after the transfer of the boat to Lend-Lease. Hull performance graphs indicate the boat hull design would easily allow speeds up through 40 knots, however I could not find any follow on performance tests with the 4M2500s or if a third set of different size props were ever installed. Looking at all the early PT boat BuShips data, props, either having the wrong size (P and D), using race type wheels which wore out quickly, or suffering from excessive cavitation, seem to be a constant theme.
As far as critiques from the various reports, maneuvering and seakeeping were excellent, as were the cockpit layout and internal arrangement, however the boat's small size (59 ft), restricted deck size due to the rolled chine and deck mounted mufflers, and the stern launched torpedoes came up on the negative. In response to the restricted deck, it was stated that the rolled chine gave this light weight boat great strength (it is true she never suffered the hull and deck problems of boats without the rolled chine). Since she planed early, not sure how well her design would have taken to weapons overloading and her small fuel capacity (1665 gal) would have also been a limiting factor. Lastly, having to run on 1 prop required excessive rudder to drive her at what turned out to be an inefficient speed (just below hump speed). Her best operational speed seems to have been about 25-26 knots.
Of note, PT-4 was built with two 3M2500s and was suppose to receive a centerline 700 HP Allison. Found no indication that this Allison engine was ever installed (initial trials done with just the two Packards).
Here is another photo - Cheers, Andy
Aft aluminum steering gear. Cables ran down starboard side
Posted By: Andy Small | Posted on: Feb 16, 2015 - 11:55am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Interesting stuff, Andy. Thanks....
Will
Posted By: Will Day | Posted on: Feb 16, 2015 - 12:45pm
Total Posts: 1955 | Joined: Oct 8, 2006 - 4:19pm
Well, Sometime things aren't at all what you expect. Just received the wood analysis from the Forest Products Laboratory (USDA) from a 7/16 hull planking sample taken from PT-3. The inner (7/16) and outer (5/8) planking are either Sequoia, or Giant Sequoia!
I knew after my last two visits that the wood looked extremely pale, and after I obtained a small sample (extremely light weight) and cut the piece to send off for analysis, I was pretty sure it wasn't mahogany, but def no idea it was Sequoia. Wow, not exactly sure what that's going to mean for restoration.
There's a NAVSHIP 250-336 publication on wood ship/boat building material. Does anyone have access to the volume that would talk about red wood/Sequoia for planking? Really interested in what they had to say.
Internet searches are kind of all over the place on use of this material for planking. Pretty much nothing on big boat construction, just mostly little stuff like canoes. I did find a 1944 article describing redwood for boat planking, and recommending younger heartwood which is tougher and more suitable than the old stuff.
Cheers,
Andy
Posted By: Andy Small | Posted on: May 15, 2015 - 9:11am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Hi Andy,
After doing some digging it would appear that they chose this timber for its high resin content, very resistant to borers and of course its weight, making for a good weight gain over mahogany.
Redwood does seem to be quite available for use in the decking industry but mainly on the west coast of America, of course once you find out which part of the trunk you want you will have to find a supplier who will sort that part and deliver it.
Odd that some sites state the heartwood is the best others say the heartwood is to soft?? so someone who works with redwood may have a better idea which is better!
Interesting restoration project would be nice to see this Boat back to her former glory and back in the water, good luck with her!
Yours
D.buck
Posted By: David Buck | Posted on: May 23, 2015 - 3:50pm
Total Posts: 332 | Joined: May 4, 2008 - 2:59am
It never dawned on me that the hull planking might be made of two different materials, which explains my errors in identifying the wood, but this seems to a standard practice in wooden boat building.
This weekend I finally had a chance to read through PT-4's 1945 survey and buried within the report, it says the hull planking material was made of two materials, mahogany outer and what they called cedar (now I'd in PT-3 as California red wood) interior planking. They reported some cracking of the inner hull planking. The piece of wood I sent off for analysis was from the inner planking. Next time I'm down at the boat I will grab a sample of the outer hull to complete the analysis. I had sanded some of the outer hull back in Dec, and it looked to me to be mahogany.
I should have done a better job in the investigation, since I seem to suffer from a case of seeing what I want/expect to see Guess it would be a we bit more convenient if the boat was closer than a 10 hour round trip.
FYI: From the Shipwright in Training website I found this definition of a double planked hull which seems to match up with PT-3's:
Double Planked Hull: A hull that is made up of two layers of planking. Usually the inner layer is a softer, lighter wood such as cedar. The outer planking is often mahogany. Builder often put a coat of thickened shellac between the plank layers, which acts as a sealer. The plank seams are staggered so that the inner and outer seams don’t line up. The outer planking is usually not caulked, so the seams must be made very precisely. This type of hull is light and quite strong.
Posted By: Andy Small | Posted on: May 25, 2015 - 9:16am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Cedar is a very soft timber you only have to look at it wrong for it to crack, I have it on our house and recently needed to replace it O FUN, I'm surprised they used it on the boat!
However they were looking for a mix that would work so that would explain it.
10 hours round trip so do you plan to obtain some faster means of travel or are you going to either;
A. move the boat closer to your home?
B. move home closer to the boat?
Just thought I'd ask for the fun of it!
Interesting to note that when they built the PT Boats planking they had to take into account the swelling of the timber when they put the boats into the water, as the planking of the PT3 of both layers is fore and aft what this may mean to this in building terms?
Yours,
D.buck
Posted By: David Buck | Posted on: May 25, 2015 - 11:59pm
Total Posts: 332 | Joined: May 4, 2008 - 2:59am
Fresh from this morning. PT-3 in her new location at Flanigan Brother's Boatyard. Another small step towards restoration, and a wee bit closer to the water
Photo really shows off her lines.
- Andy
And with a bit of creative license
Posted By: Andy Small | Posted on: Jun 3, 2015 - 6:28am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Great photo Andy!
Jerry
Jerry Gilmartin
PT658 Crewman
Portland OR
Posted By: Jerry Gilmartin | Posted on: Jun 3, 2015 - 8:52am
Total Posts: 1472 | Joined: Oct 8, 2006 - 11:16pm
Thanks Jerry,
This spot is temp and next one should be her restoration spot.
I just edited the photo post with a sepia version.
Cheers,
Andy
Posted By: Andy Small | Posted on: Jun 3, 2015 - 9:20am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Great photo, hey any progress is a step forward in the right direction, no matter how small that step is. Historically it is a good thing she is being saved...........
Posted By: Frank Andruss | Posted on: Jun 3, 2015 - 10:14am
Total Posts: 3964 | Joined: Feb 9, 2007 - 11:41am
Any updates on pt-3 so far?
I'm curious to know more!😀
ThePTboater
Posted By: ThePTboater | Posted on: Apr 2, 2016 - 10:49pm
Total Posts: 136 | Joined: Jan 17, 2016 - 1:28pm
Updates: We are still waiting on the non-profit status but I can comment on some items.
1) It seems the USDA wood analysis on the inner planking was incorrect and the wood is actually Port Orford cedar. This corresponds with some recently obtained documentation.
2) Discovered that the actual drawings were done by Sparkman and Stephens and not the Fisher Boat Works (FBW). After contacting S & S, I was able to obtain a full list of the PT-3/4 drawings and the S & S project number of 308. We thought we had a possible lead, but because the drawings were classified, they were all returned to the USN and not retained by S & S or Mystic. Since BuShips in 1945 contacted FBW asking for the drawings, indicating that the USN no longer could find them, I'm thinking that the drawings probably were forwarded to the UK and later RCAF during the April 41 Lend Lease. We will probably end up having to commission someone to do the drawings and at that point, we will then uncover the original drawings
3) I have discovered that the internal transverse framing is steamed oak (doubled) instead of what I originally thought was laminated oak framing. Most probably we will need to use laminate oak framing for the replacement of damaged framing during the restoration since that will be stronger and easier to form in place.
4) During the construction in 1939, both PT-3 and 4 were delayed by four months due to the unavailability of the new 3M2500 Packards. I had previously wondered why it took so long. PT 3 was originally scheduled to have been completed in December 39. I have also NOT been able to located the November-December 39 construction photos at the National Archives. These are not in the photo section nor could I find them in the BuShips PT-3/4 files. These are important since they show the completed interior and the cockpit area.
That's about it for updates.
Posted By: Andy Small | Posted on: Apr 4, 2016 - 11:17am
Total Posts: 262 | Joined: Nov 20, 2013 - 9:04pm
Nice work Andy, I appreciate that this boat is being saved, it's a nice change from all the Higgins boat we already have, not that it's necessarily a bad thing!😀
ThePTboater
Posted By: ThePTboater | Posted on: Apr 11, 2016 - 8:38pm
Total Posts: 136 | Joined: Jan 17, 2016 - 1:28pm
