Quote: "...I have seen some photos of PTBs with that odd 'button' on the mast top but haven't yet fathomed what it could be. ...."

Nobody's perfect!
But then - Who want's to be???
😎

I think you will find that I mentioned the small streamlined dish aerial on the last SO-3 set as a possibility earlier - but pointed out that the streamlined shape is nothing like the button that the Aerokits boat has. Since it appeared on the Adamcraft as well, my best guess was either that ELCO did not know the size of the SO set when they drew those plans, or they did, but considered the actual aerial size to be a military secret....

And there you have your odd button on the PTB mast! 😉

I didn't want to make LOTS of work for myself! That's why the rear guns on the EeZeBilt PT boat are just double Oerlikons - they are easy to make with a few bits of tube and some tinsnips.

But all this discussion about accuracy has left me unhappy that I have avoided putting in the classic 40mm Bofors at the stern. You can, of course, buy one at 1:48 scale, but it will set you back £20 or more, which is rather non-EeZeBilt.

So I spent a bit of time this afternoon putting together a design for a cheap 1:48 scale Bofors - not an easy task because the gun looks so complex. This is what I have so far - it's certainly cheap, and the gun unit is about 1" square.... when complete I think it will look ok at distance....

Dodgy - from the difficulty point of view the new one 1945 et al seems to be the hardest to make and most later models seen at shows etc seem to have the original radar (2nd type). Have you attempted the latest one ? Will dig out my old Billings version (P87) to see what it suggests and scan that part of the plan.

: - did that and P87conforms to type 1 (very early kit - obeche not ply panels and printwood only) two little plastic models have type 2 (japanese?) Revell PT117 again type 1.

Just for info, in case anyone wants to make their PT boat a bit more realistic, the mast should look like one of the three illustrated below, depending on year...

Here is a photo of the Adamcraft plan (overview) from his book dated 1950 - so the plans are somewhat earlier. A scan is going to be rather tricky, given the paper size...

You will see marked similarities with the Aerokits ones at many points - the radar, gun mounts, torpedoes, life-raft, etc... Adams extends thanks to ELCO for providing the prototype drawings, so I think these are taken from them, and the Aerokits plan derived from the Adamcraft one.

I can't tell whether the original ELCO drawings contained what I saw as errors, however. If they did it maybe because they were early prototypes where the weapons or electronic fit was not yet agreed, or maybe because the 1950s were quite paranoiac about military issues and they didn't want to release some details....

"...I have seen some photos of PTBs with that odd 'button' on the mast top but haven't yet fathomed what it could be. ...."

I would love to see a reference for such a photo. The non-radar masts had a small masthead light there, and the SO-3 set had a small streamlined dish aerial mounted under the rotating parabola - but not the shape which Aerokits or Adamcraft shows...

"Er... yes. I have also done a bit of research when drawing up the EeZeBilt PT boat."

I thought you mighta dun! 😉👍
Let's hope that the 'Plan Sources' initiative gains momentum.
Just thought I might try and give it a shove.
More soon.
All the best. Doug

Er... yes. I have also done a bit of research when drawing up the EeZeBilt PT boat.

The US came late to the concept of light torpedo boats. The original doctrine, gathered from the old WW1 exploits of the MAS boats, was that these light boats would overcome capital ships by force of numbers and agility - typically in harbour defence scenarios where their lack of blue-water range was not an issue. Similarly, they could defend against prowling submarines. Since the US did not have any close maritime enemies, they did not consider light torpedo boats to be worth investing in.

Strategy had moved on by WW2, and when the US finally considered them, with the 'Plywood Derby', their original raison d'etre had all but vanished. capital ships were surrounded by Torpedo Boat Destroyers, and radar meant that it would be suicide to consider approaching a 'big gun' enemy on the high seas. Nevertheless, the initial US PTB purchase specified armament for just this function - standard US Mk VIII tube-launched torpedos, smoke for concealment and 0.5 calibre machine guns for local/AA defence.

This turned out to be almost completely useless in practice. The tactical doctrine makes engrossing reading:

"...3401. Unsupported attack on enemy task force.-The plans for attacking an enemy convoy apply equally to attacking an enemy task force, the only material difference being that stiffer resistance may be expected and a great number of boats should normally be employed.

3402. Supported attacks in fleet action.-This type of attack has such a wide range of possibilities which depend on so many factors that it is not possible to recommend any general plan. Some of the possibilities, however, are listed below.

(a) Night action with destroyer support where MTB's first attack the enemy screen, permitting destroyers to penetrate the screen and attack the - main body.

(b) Night action with destroyer or light cruiser support where the DD's and CL's engage the screen, permitting MTB's to pierce the screen and attack the main body.

(c) Day action where destroyers, aircraft and MTB's attack enemy main body simultaneously. MTB's launched from a carrier or operating from a fleet base.

3403. Attacks coordinated with aircraft.-Attacks by large numbers of motor torpedo boats and aircraft made simultaneously on enemy forces should be highly successful, as such attacks will present a great multiplicity of targets for enemy anti-aircraft and secondary batteries and will bring heavy striking power to bear on the enemy. The time of the attack will depend upon the motor torpedo boats, as aircraft can control their timing more readily. The aircraft attack may be a dive-bombing, strafing, or torpedo attack or any combination thereof. An aircraft torpedo attack, coordinated, should be made on opposite side from the MTB attack. A high altitude horizontal bombing attack will not divide the enemy's fire to the maximum extent, as he will not divert the use of his machine guns toward the bombers.

In this type of attack all available motor torpedo boats should attack simultaneously...."

!!!

There are a number of propaganda stories during the early part of WW2 suggesting that PT boats were engaging and sinking Japanese cruisers. These all seem to be untrue, and circulated as 'morale boosters'. I can find few examples of a successful attack on a big ship - the strike on the light cruiser Abukuma by PT137 during the Battle of Surigao Strait (which was almost certainly a mistake!) is one notable example.

The PT boats came into their own as shore harassing gunboats and inter-island supply interdiction once the initial Japanese advance halted, and that was when they began needing to add more guns. The Toku Daihatsu barges used for Japanese supply were almost immune to torpedoes, drawing only a foot or so, and were heavily armoured, so the 'Ma Deuces' were of limited use.

Some early PT boats had a 20mm Oerlikon mounted on the stern. I have never seen one with twin Oerlikons mounted this way, though there might have been occasional one-offs. Invariably the armour plate on the gun was discarded for weight reasons.

Single 20mm Oerlikons were also mounted on the front quarters, together with the distinctive 'horse-collar' M4 37mm cannon, initially from u/s Bell P-39 Airacobras, but later as a standard fitting. By 1945 they were adding 5" rockets...

On the stern the boats were rapidly updated to carry a Bofors 40mm, which they could do when the heavy MkVIII torpedo tubes were replaced with light Mk XIII aircraft 'roll-off' torpedoes. A bit of a misnomer, this, as the torpedoes did not actually roll.... But I have never seen a PT Boat with a 35mm cannon on it.

The radar fitting was one of three types:

1 - no radar
2 - SO dome
3 - SO-3 with rotating parabola.

I wish there was a simple, cheap way to get a 1:48 Bofors gun. The EeZeBilt PT boats need a Bofors on the back, but I haven't managed to source one yet. And I suppose I should add torpedo tubes to provide accuracy across the whole PT range...

Below is a picture of two EeZeBilt PT boats. The far one is an 1940 model with no radar mast and a single Oerlikon on the stern. It should really have tubes as well, of course. Note the position of the life-raft on the bow.

The near one is a 1944 fit, with an M4 at the front and SO radar. The life-raft has moved back to the top of the chart cabin. It should really have a Bofors on the stern, and a small boat on the day cabin, but I haven't made these yet.

And, of course, no PT Boat had varnished wooden planking. But I just thought that it looked nice... 🤗

Looks like the Sea Nymph might have been modelled on the 25' version of the Starcraft by Bates. Followed the lead on those from this forum and the 25 seems to fit the bill even to the little stub mast on the windscreen.So that would fit with Les Rowell saying it was modelled after a Broads cruiser. Will have to convert the file before being able to make a proper comparison.

Hi DG,
I'd be MOST interested to see what you consider to be the 'relevant plan'!
So here is your 'Round to It' 😉
I heartily agree with you regarding the portholes / glazed units!
But as far as armament goes - Anything goes, especially for those operated in the Pacific theatre - which was the vast majority. Crews scrounged and used whatever they could get their hands on. The classic example is the 37mm Army Anti Tank gun JFK scrounged and fitted to PT109. To no avail; they were rammed and sunk the day after by the Japanese destroyer IJN Amagiri. If it worked it was introduced in the next production class.

As far as your 'relevant plan' goes; I guess that depends on which boat of which class in which of 30 squadrons (RONS) of 80' ELCOS built at which stage of the war was taken as the basis of the plan.
The early classes, up to about the 103 class (to which JFK's infamous boat belonged) had no radar at all. You are correct that there was a large radar pod on some PTB's. As built probably from the 200 class at the earliest. Earliest pics and references I can find indicate that the radar pods may have been first fitted to the 500 series. Highly likely that such such details were still secret and not available to Les & Co in the late 40s early 50s.
I have seen some photos of PTBs with that odd 'button' on the mast top but haven't yet fathomed what it could be. Don't fit no radar antenna that I know of and it's way too small for the radar of the time anyway.

Some earlier boats may have been retrofitted but not many.
Most squadrons only had one or two boats fitted with radar at all (destroyers and upwards took precedence in the early days of radar, until centimetric and corresponding smaller antennas were introduced and could be mass produced) and most PTB skippers switched them off at night and lowered the mast anyway to reduce the risk of detection.
The early classes also had no armament on the foredeck. As the official model of PT109 shows. Only the Carley Floats or some other form of liferaft. I also attach drawings from the USN Bureau Of Ships deck plan and profile drawings as designed and originally built. (Thanks for the pointer Maurice👍).
They and all subsequent classes were, consequent to operational experience esp. in the Pacific, rapidly fitted with a colourful assortment of single and twin barrel cannons fore and aft as well as single and /or twin 20mm Oerlikons midships and/or on the torpedo mounts - similar to British MTBs, e.g. Vosper.
Later versions had all sorts of guns on the foredeck and a single 0.5" machine to port just forward of the cabin. so as far as a PTB model goes; Yer pays yer money and yer takes yer choice. You can fit a model with virtually anything less than a 3" QF/HA and probably be right for at least one boat somewhere at some time!
In my archive I have dozens of photos of PTBs of various types and classes; as built, in operation, and as restored, if anyone needs 'em.😉

Wrt the straight or front cabin; difficult to see what was intended in the Aerokits plan😮
I agree with you that the ELCOs had a cabin front slanted backward. The Huckins PTBs did have a straight cabin front. Not many were built and never saw war service being stationed mostly in Florida, Pearl Harbour and Midway and used for training. Maybe someone got their plans mixed up.
Cheers and G'night, Doug 😎
PS Have a look at Battleship Cove for lots of photos of the restored PT617. There you can see the later radar pod.😉

"Armament
The primary anti-ship armament was two to four Mark 8 torpedoes, which weighed 2,600 pounds (1,179 kg) and contained a 466-pound (211 kg) TNT warhead. These torpedoes were launched by Mark 18 21-inch (530 mm) steel torpedo tubes. Mark 8 torpedoes had a range of 16,000 yards (14,630 m) at 36 knots (67 km/h; 41 mph). These torpedoes and tubes were replaced in mid-1943 by four lightweight 22.5-inch-diameter (570 mm) Mark 13 torpedoes, which weighed 2,216 pounds (1,005 kg) and contained a 600-pound (270 kg) Torpex-filled warhead. These torpedoes were carried on lightweight Mark 1 roll-off style torpedo launching racks. The Mk13 torpedo had a range of 6,300 yards (5,800 m) and a speed of 33.5 knots (62.0 km/h; 38.6 mph).

PT boats were also well armed with numerous automatic weapons. Common to all US PT boats were the two twin M2 .50 cal (12.7 mm) machine guns. Early PT boats (Elco PT20 through PT44) mounted Dewandre plexiglas-enclosed hydraulically operated rotating turrets.[12] Almost immediately after the attack on Pearl Harbor, the Dewandre turrets were replaced on the entire PT boat fleet with open ring twin mounts. The ring mount was designed by both Elco and Bell, and designated Mark 17 Twin 50 caliber aircraft mount.[13] Part of the Mark 17 Mod 1 and Mod 2 ring mount consisted of the Bell Mark 9 twin cradle.[14][15] Another automatic weapon commonly mounted on PT boats was the 20 mm Oerlikon cannon. On early series of boats, this cannon was mounted on the stern. Later in the war, several more of these 20 mm cannons were added amidships and on the forward deck.

Forward of the chart house of some early Elco 77-foot (23 m) boats (PT20 through PT44) were twin .30 cal (7.62 mm) Lewis machine guns on pedestal mounts. Beginning in mid-1943, some boats were fitted with one or two .30 cal Browning machine guns on the forward torpedo racks on pedestal mounts.

Occasionally, some front line PT boats received ad hoc up-fits at forward bases, where they mounted such weapons as 37mm aircraft cannons, rocket launchers, or mortars. When these weapons were found to be successful, they were incorporated onto the PT boats as original armament. One such field modification was made to Kennedy's PT-109, which was equipped with a single-shot Army M3 37mm anti-tank gun that her crew had commandeered; they removed the wheels and lashed it to 2x8 timbers placed on the bow only one night before she was lost. The larger punch of the 37mm round was desirable, but the crews looked for something that could fire faster than the single-shot army anti-tank weapon. Their answer was found in the 37mm Oldsmobile M4 aircraft automatic cannon cannibalized from crashed P-39 Airacobra fighter planes on Henderson Field, Guadalcanal. After having demonstrated its value on board PT boats, the M4 (and later M9) cannon was installed at the factory. The M4/M9 37mm auto cannon had a relatively high rate of fire (125 rounds per minute) and large magazine (30 rounds). These features made it highly desirable due to the PT boat's ever-increasing requirement for increased firepower to deal effectively with the Japanese Daihatsu-class barges, which were largely immune to torpedoes due to their shallow draft. By the war's end, most PTs had these weapons.

The installation of larger-bore cannons culminated in the fitting of the 40mm Bofors gun[16] on the aft deck. Starting in mid-1943, the installation of this gun had an immediate positive effect on the firepower available from a PT boat. The Bofors cannon had a firing rate of 120 rounds/min (using 4-round clips) and had a range of 5,420 yards (4,960 m). This gun was served by a crew of 4 men, and was used against aircraft targets, as well as shore bombardment or enemy surface craft.
Gunboats

In the Solomon Islands in 1943, three 77-foot (23 m) PT boats, PT-59, PT-60, and PT-61, were converted into "PT gunboats" by stripping them of all original armament except the two twin .50 cal (12.7 mm) gun mounts, then adding two 40mm and four twin .50 cal (12.7 mm) mounts. Lieutenant Kennedy was the first commanding officer of PT-59 after its conversion. On 2 November 1943, PT-59 participated in the rescue of 40 to 50 Marines from Choiseul Island and a foundering landing craft (LCP(R)) which was under fire from Japanese soldiers on the beach.[17]

Towards the end of the war, beginning in 1945, PTs received two eight-cell Mark 50 rocket launchers,[18] launching 5 in (130 mm) spin-stabilized flat trajectory Mark 7 and/or Mark 10 rockets[19] with a range of 11,000 yards (10,000 m). These 16 rockets plus 16 reloads gave them as much firepower as a destroyer's 5-inch (127 mm) guns. By war's end, the PT boat had more "firepower-per-ton" than any other vessel in the U.S. Navy.

PT boats also commonly carried between two and eight U.S. Navy Mark 6 depth charges in roll-off racks. Sometimes they were used as a last-ditch weapon to deter pursuing destroyers. The depth charge could be set to go off at 100 feet (30 m), and by the time it exploded, the pursuing destroyer might be above it.

Additionally, a few PT boats were equipped to carry naval mines launched from mine racks, but these were not commonly used. "

This might become an 'occasional item' on the inspiration for Les Rowell's boats!

The recent discussion on the PT Boat plans reminded me that I was always intrigued at the inaccuracies on the Aerokits PT Boat plan. The model is of the ELCO 80-footer and there are several departures from accuracy which I cannot understand.

For a start. the model has round portholes, while all the glazed units on the original were rectangular. And the front of the forward chart-room cabin is straight across, while the original had an arrow planform. The radar dome was much bigger than the odd little button perched on the mast, and the armament is a strange mix which almost certainly never existed.

I glanced at the Adamcraft model, which probably just predates the Aerokits one, and what did I see? The same odd armament, and the same tiny radar dome. The Adamcraft has a proper cabin shape and windows, but it looks to me as if Mr Rowell drew some of his inspiration from the Adamcraft kit.

When I can get round to it I will scan the relevant plan...

There are few of us prepared to put that amount of work in. Well done!

Dodgy - thanks for that - spent a lot of time searching.

You must have done a lot of research to find that matching boat? Dedication!!

Thanks for the info about svensons, I have now downloaded the plans for myself.
Cheers Colin.

Happy you found it brought back memories😀. It is indeed a 16ft fishing boat .The full size plan is available on the web at Svenson's Free Plans if you wanted a copy. I have both now in digital format. Interestingly a "missing" Rhodesian "Model Products" plan was based on the Sea Urchin, with the Cabin being removable and the deck straightened which makes it resemble a small Sea Scout. The other Model Products kits are largely based on Les Rowell's designs, and the plans for them are on both the Old Boats and RC Groups ,(Vintage Boats) websites.

Hi, I presume that the Dolphin 16 is the same boat that my dad built in the late 50's as a 16ft family fishing boat, he also built the trailer to carry it on. He fitted an Austin 7 engine and gearbox. We used to go to Cleethorpes most weekends in the summer with it. Traded in for a 20foot launch in 1962 to give our growing family room. I think it deserves to be modelled, so I might have a go in a large scale say 1/6th.
Thanks for the memories, Colin.

Looks like you have found the source of Mr Rowell's inspiration..!!!

They really are very similar, aren't they?