| Author |
Topic: PT-3 Information |
|
 |
Andy Small |
MASTER
|
  
Posted on: Jan 7, 2015 - 3:03pm
|
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
 |
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
nahma
New Member
|
Posted on: Jan 10, 2015 - 3:42pm
|
Original drawings means there are models in the future!!!
|
Total Posts: | Joined:
Unregistered | IP
Logged
|
|
Andy Small
MASTER
|
Posted on: Jan 11, 2015 - 11:44am
|
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
|
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
Andy Small
MASTER
|
Posted on: Feb 16, 2015 - 11:55am
|
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
|
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
Will Day
TOP BOSS
|
 Posted on: Feb 16, 2015 - 12:45pm
|
Interesting stuff, Andy. Thanks....
Will |
Total Posts: 1955 | Joined:
Oct 8, 2006 - 4:19pm | IP
Logged
|
|
Andy Small
MASTER
|
Posted on: May 15, 2015 - 9:11am
|
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
|
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
David Buck
TOP BOSS
|
Posted on: May 23, 2015 - 3:50pm
|
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 |
Total Posts: 332 | Joined:
May 4, 2008 - 2:59am | IP
Logged
|
|
Andy Small
MASTER
|
Posted on: May 25, 2015 - 9:16am
|
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.
|
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
David Buck
TOP BOSS
|
Posted on: May 25, 2015 - 11:59pm
|
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 |
Total Posts: 332 | Joined:
May 4, 2008 - 2:59am | IP
Logged
|
|
| |
Andy Small |
MASTER
|
Posted on: Jun 3, 2015 - 6:28am
|
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
|
Total Posts: 261 | Joined:
Nov 20, 2013 - 9:04pm | IP
Logged
|
|
|
