MTB or MAS Carriers

[jcf]

Self-baling, self-righting lifeboats are not new, however they are designed for stability
and surviving rough water rather than speed. Their slow speed would be of doubtful
utility as pickets. However perhaps a hybrid hull design that flattened the bottom out
towards the stern would allow increased speed without completely compromising
seakeeping. Something not unlike the hull design of an S-Boat in fact.

Here is a pdf on the USCG 36' boay which is of the period and could form the
basis of a picket boat concept.
http://www.uscg.mil/history/assets/boats/docs/36FootMLBTypeT.pdf

How quick would they need to be though? Convoy speeds could be as low at 7 knots and even the purpose-built escorts sometimes had top speeds of under 20 knots. Submarine speeds were less than 20 knots on the surface and less than 7 knots submerged. Normal MTBs had speeds in the 40-50 knot range, so their design could be compromised considerably in the name of seakeeping rather than speed if they only needed to do say, 25 knots.

Max speed of the USCG 36' was 9 knots. You'd definitely need more speed than that. 

None of the deep-V MTB designs would be a good starting point, as stated, I'd start with a lifeboat
design and modify it to make around 20 knots at cruise.

[rickshaw]

Thing is, you can design for stability or you can design for speed, rarely can you do both.  20 kts doesn't sound like much today but back then, it was quite fast for most boats and ships which used to cruise at about 8-10 kts.

I wonder how this sort of plan of having numerous piquet boats would work when a North Atlantic gale blows up?

[Weaver]

Thing is, you can design for stability or you can design for speed, rarely can you do both.  20 kts doesn't sound like much today but back then, it was quite fast for most boats and ships which used to cruise at about 8-10 kts.

Everything's a compromise. A 20 kt boat that incorporates lifeboat-like seakeeping features should be well within the technology of the day, and would be useable in a much greater range of sea states than a classic 40 kt MTB hull.

I wonder how this sort of plan of having numerous piquet boats would work when a North Atlantic gale blows up?

When the weather gets really bad, the picket boats would be firmly back on board the "mother ship", but then the u-boats would be having a hard time of it under those conditions too. Surface running is every bit as miserable for subs as it is for small ships in heavy weather, and their ability to find and attack targets severely compromised. If they submerge to escape the weather then their speed and endurance are reduced.

[rickshaw]

Thing is, you can design for stability or you can design for speed, rarely can you do both.  20 kts doesn't sound like much today but back then, it was quite fast for most boats and ships which used to cruise at about 8-10 kts.

Everything's a compromise. A 20 kt boat that incorporates lifeboat-like seakeeping features should be well within the technology of the day, and would be useable in a much greater range of sea states than a classic 40 kt MTB hull.

Perhaps.  I suspect you'd end up with something much larger than you might be thinking about, if nothing else to improve sea keeping.

I wonder how this sort of plan of having numerous piquet boats would work when a North Atlantic gale blows up?

When the weather gets really bad, the picket boats would be firmly back on board the "mother ship", but then the u-boats would be having a hard time of it under those conditions too. Surface running is every bit as miserable for subs as it is for small ships in heavy weather, and their ability to find and attack targets severely compromised. If they submerge to escape the weather then their speed and endurance are reduced.
[/quote]

You're assuming you'd have sufficient warning.  Also, U-Boats used to carry attacks in all weathers, not just (relative) calm periods.   While I agree, their sea keeping tended to be worse than a full size ship of comparable tonnage, they were better than most small boats, with their very low centre of mass, they often went through the waves rather than up and over them.  They also tended to roll less.

[Weaver]

You're assuming you'd have sufficient warning.  Also, U-Boats used to carry attacks in all weathers, not just (relative) calm periods.   While I agree, their sea keeping tended to be worse than a full size ship of comparable tonnage, they were better than most small boats, with their very low centre of mass, they often went through the waves rather than up and over them.  They also tended to roll less.

Fair comment, but you can only do what you can do. No defence was perfect against U-boats: "proper" escorts couldn't be built fast enough until later in the war, and aircraft were also either grounded or had their effectiveness diminished in bad weather too. Given the amount of resources that Britain in particular put into coastal warfare craft with dubiously cost-effective results to show for it, it seems to me that diverting a small amount of that effort into at least experimenting with this technique would have been worthwhile.

[Old Wombat]

Just a though;

I know they're larger than MTB's, MGB's & MAS boats but what about SGB's?

Steam Gun Boats, even after they were up-armoured, were still capable of 30 knots & were heavily armed, eventually carrying 1 x 3" gun, 2 x single 6-pdr's, 2 x twin 20mm Oerlikons & 2 x 21-inch torpedoes. With some modifications for North Atlantic operations they may be quite useful in the perceived role. Possibly having 2 boats per carrier.

Possible modifications:

1) replace steam turbine with marine diesels (although louder than the steam turbines diesels save having to keep steam up in the boilers "just in case");
2) reduce armament by either 1 or both 6-pdr guns;
3) enclose the 21" torpedo tubes within the hull with the option of 1 or 2 reloads per tube;
4) redesign the deck & superstructure to be more "water shedding";
5) place a semi-enclosed turret around the fore-deck mounted 3" gun; &
6) semi-enclose the bridge.



Guy

[jcf]

Thing is, you can design for stability or you can design for speed, rarely can you do both.  20 kts doesn't sound like much today but back then, it was quite fast for most boats and ships which used to cruise at about 8-10 kts.

The classic Maine/Down-East lobster boat challenges that argument, ditto the Columbia Bar/coastal
fishing boats of my home region of the Pacific Northwest. 

The Beals Island type would be a good starting point.
Here is a study plan for the rebuild of a circa 1950 boat to be rebuilt into a picnic boat:
http://www.dhylanboats.com/plans/diana_study_plans.pdf

BTW the boatbuilder I worked for in the late 90s used the classic lobster boat and bar fisheries designs
as the starting point for his 24 to 42 foot cruisers. Some retained round bilges, others combined the
existing topsides design with a new hard chine, deep-v bottom with slight deadrise aft.

[jcf]

The 72' HDML looks to be a good starting point, although you'd want more power as, according
to the designer of the series, with their diesels they never made more than 12 knots. 

http://www.naval-history.net/WW2Ships-HDML1001.htm

Packard was working on marine diesels in the late '20s - early '30s but development was
curtailed due to the world economic situation. The engines built were inline-6, two were
installed Chief Engineer in Col. Vincent's Cox & Stephen's yacht Clarinda , but
consideration had been given to V-12 and I-8 concepts. So, what if Packard had continued
with diesel development? Perhaps by 1939-40 they would have had a series of powerful,
high-speed diesels as stablemates for their 2500 in³ V-12 petrol engines?
Opens up possibilities.

BTW the LSD, wasn't conceived until Sept. 1941.