View Full Version : Torpedo Stern
04-20-2002, 11:35 AM
Anyone have any info on the design reasons for a torpedo stern, as seen on the Jonesporter Launch?
What benefits does the type present? What strength characteristics?
I've searched through as many books and publications as I can find, including WB #136, but I can't find specific design information.
There seems to be at least two different stern config's called "torpedo stern."
This is a 1940's Stancraft with what they called a torpedo stern:
...and this is GUS at Rumery's, also called torpedo stern:
The late 1940's Chris-Craft Custom has what looks like GUS's transom, but they called it "bubble-back"
And here's a "1906 or 1907 Mullins Automobile Torpedo Stern Launch"
And the Mullins Factory:
The torpedo stern seems to have been around since at least the late 1800's, but all the mentions on the web refer to it as a cosmetic feature. One citation called it a "typical negative transom." I couldn't find anything that said why it was designed that way. The style on the Jonesporters and GUS seem to be present on alot of sailboats.
04-20-2002, 01:59 PM
Actually, what I probably mean is what's also called a "drake tail." redface.gif My ignorance is showing again!
04-20-2002, 02:10 PM
Nice pics donwest. I've always thought there was more to it than aesthetics. I'll be interested in the comments. Aerodynamics ? Mechanical stress distribution ? The idea of a transom always seemed like a discontinuity in what what is otherwise a fairly natural shape. Maybe the old timers were just suplying us with debate fodder.
Besides the torpedo stern of the Stancraft shown by donnwest, "GUS" is sporting what I've usually known to be called as a "slipper stern" a moderate one at that. Perhaps it is more of a negative raked horse shoe stern. The Chris is showing a moderate "barrel back" stern. The old launch has a slipper stern with what looks to be the beginnings of what came to be known as a bussel. Some of the advantages may have been to increase the waterline length, position the rudder farther aft thereby increasing space available for passengers, fuel tanks, whatever. With the launch, the broad flat (sometimes referred to as a beaver tail) area helped to contain prop wash and perhaps helped with speed. So, besides aesthetics maybe they did serve some other purposes. Bussel sterns on Ted Geary designed Fantail yachts are great to look at out of the water. Lets see how long it takes donnwest too find a couple pictures of one of those. Here's a clue donnwest, CANIM, BLUE PETER, PRINCIPIA, ELECTRA. The OLYMPUS built by Consolidated in the 30's has a great stern too.
OK "drake tail" gave me more search fodder:
"The "drake tail" design--the lower section of the stern jutting out away from the boat--also allows for swift acceleration."
= = = = =
"These boats had the characteristic Hooper's Island Drake Tail stern configuration, which was originated on Hooper's Island and has been copied elsewhere on the bay. The design is unique in that these work boats are built with what is primarily an aesthetic look rather that a practical one. I'm sure the watermen who use them will justify the beautifully curved and countered transom as a practical solution to providing a long waterline and cockpit buoyancy with minimal weight, but the real answer is that they just like the way they look - so does everyone else."
= = = = =
This snippet is out of a review of a Morgan (plastic) 45 sailboat:
"Its long drake tail and sharp pointed bow produce a extremely fast hull."
That's all I could find...references to cosmetics and references to speed. I suppose there is some small gain in speed to be achieved from lengthening the waterline, without increasing the beam, but I can't believe it would be that much of a gain.
Maybe it is just cosmetic...it certaily looks good.
Motoryacht Thea Foss
THEA FOSS - Originally "INFANTA"
Length Overall . . . . . . . . . . . 120'-0"
Beam . . . . . . . . . . . . . . . . . 21'-6"
Draft . . . . . . . . . . . . . . . . . . 9'-3"
Construction . . . . . . . . Riveted Steel
Engines: Twin Atlas Imperial Diesels
275 hp ea., Cruise 13.5 knots
Designed by L.E. "Ted" Geary
for a commission by John Barrymore
Built by Craig Shipbuilding Co., Long Beach, CA
= = = = =
Mariner III was built in 1926 for Captain James Griffiths of Griffiths Steamship Company. This classic 122' fantail motor yacht, was designed by Ted Geary. Traveling to China to select the lumber for her construction, Captain Griffiths chose 3" teak planking for the hull and very strong wood, called yacal, for framing. Originally named "SueJa III," Captain Griffiths used the yacht to travel up and down the West Coast.
[ 04-20-2002, 03:51 PM: Message edited by: donnwest ]
04-20-2002, 02:56 PM
Hmm. Looks like a terminology quandary in the making.
This is what I've always seen as a "slipper tail:"
The image is from Peter Freebody in the UK.
While searching on Geary, I found this little lovely..and she's for sale!
"The motor yacht DANAE is for sale to a qualified buyer.
Designer: Ted Geary
Builder: Vancouver Shipyards British Columbia, Canada
Length: 40 feet
Beam: 9 feet 2 inches
Depth: 2 feet 8 inches
Power: Ford Lehman 150 hp diesel"
..only 90 large!
Not a fantail, I guess...but a pretty nice old tub.
04-20-2002, 03:28 PM
BTW, thanks donn for the research and the pics. I love pics.
By way of a little more explanation, this question has been in the back of my mind for awhile, and Melissa Guinness's Jonesporter and Alan Hyde's question on powerboats popped it to the surface.
I have long been interested in either a power boat or at least a motor sailer, since SWMBO has no patience for getting where we're going at 65mph, let alone 7 knots!
In looking into designs for any boats that interest me, I have always tried to understand why a boat was designed the way it was, and what the different design features added to or subtracted from the boat's performance for my intended use.
Unless I'm just not looking in the right places, I find very little about the design of powerboat hulls that explains to me why they are designed the way they are. I see many that are relatively shallow draft that go offshore regularly. I see some that are deeper draft that are not recommended for blue water.
I see discussions that compare hard-chine vs. round-bilge designs. Built-down vs a laid-on piece.
But nowhere have I been able to find definitive text that explains things to me in a way where I can look at a powerboat hull and understand why it was designed that way, and what it should be able to do based on its shape.
In the New England fishery much of the work is done over the stern, setting traps and nets. However longliners work over the side almost as much as the trotliners of the Chesapeake. For these operations the wide corners of the transom could hang up the moving line. This explains the drake tail and reverse transom designs in some of these old work boats to me.
Thad...I don't ever remember seeing a drake tail longliner, and I doubt if it would be a very efficient stern for working longlines...especially for hauling them.
I know a longliner who works over the side, and I was thinking of how to explain the Jonesport boat. This is groundfish longlining not swardfish. The drake tails of the Chesapeake I kind of figured as crabbing boats from watching the trot liners.
The torpedo stern came before the regular/straight stern and after the overhung stern. It's my understanding that as lobsterboats were being built to be faster, the torpedo stern could not handle the horsepower. They would lose control and be very squirrely. Of course, once builders like Will Frost began inroducing the straight stern, many people objected. The torpedo stern was more pleasing to the eye -- but the square stern performed better. A good person to consult regarding this issue would be Willis Beal.
You may want to read the the following issues of Maine Boats & Harbors: Autumn, 1987 Vol. 1 #1 "Jonesport Lobsterboats" and Autumn, 1988 Vol. 1 #4 Torpedo Stern Lobsterboats. You can order back issues here: http://www.maineboats.com/
I may have these issues in my collection. I'll check and get back to you. smile.gif
P.S. On lobsterboats, torpedo sterns have also been called "washboiler-sterned"
[ 04-22-2002, 02:26 PM: Message edited by: MG ]
The more I read, the more I find that the greatest benefit of the torpedo stern was that it was easy on the eyes. Apparently, not only did early torpedo sterns handle poorly under ever-increasing horsepower, but the stern's framing was weak where it met the chine. Leaks were a problem and the repair work was time consuming.
Adding to the name game. . .
"Torpedo stern" aka "washboiler stern" aka "Jonesporter slide".
"Straight stern" aka "square stern" aka "cut-off stern"
My (utterly unsubstantiated) pet theory on the development of the torpedo stern is as follows: As the nascent inboard gasoline engines grew more powerful, the cruiser-stern (double-ended) small planing & semi-planing boat designs of the day had a tendancy to squat as the boat exceeded the 1.34 (approx) speed-to-length (S/L) ratio threshold. Design theory of the time held (accurately) that S/L ratios higher than 1.34 were achievable with high length-to-beam (L/B) hullforms, and that a flattish bottom with hard bilges and straight buttocks allowed even higher speeds. It would be reasonable to think that a redistribution of weight at the stern would alleviate the squatting, so the cruiser stern was drawn reversed, making a torpedo stern. This has the effect of maintaining a high L/B ratio, provided adequate coaming height to keep water out and people in, and moved the weight of the stern structure forward. Nice plan, too bad it didn't work much over a S/L ratio of about 2.5. Later developments added the "sponsons" at the stern, as shown in the Stancraft boat in Donwest's photo, to provide reserve buoyancy underway. These quickly became incorporated into the hull bottom as an extension of the bottom planking, and we were well on our way to developing the square stern. Developments in MTB's chronicled by Lindsay Lord during WWII and later break-through hullforms by Ray Hunt sealed the fate of torpedo sterns on fast boats. But they live on in some quarters 'cause they're so darned pretty. That's my story and I'm sticking to it (at least until it fails utterly under withering assault)!
04-22-2002, 08:01 PM
Once again, thanks to everyone for the replies...keep 'em coming!
Assuming I can puzzle out joinery to eliminate weaknesses in the structure, I'm wondering if the round stern/drake tail would be less long-term maintenance. I note on virtually every transom-sterned boat I've looked at the hull-to-transom joints are problematic, and need significant rework.
The more I look at it, the more I like it. It's one of those design things that touch some inner sense of rightness in me.
Ken, This is a worthwhile discussion and most of the positives and negatives of the design everyone has mentioned I have also read in one book or another. One story no one's mentioned yet is one of the Beals or Frosts would supposedly row around in a skiff towing a model (on a string) of a hull they were planning to build. The story went that the model had an upswept overhanging type transom and flipped over as it was being towed. It seemed to do better upside down and there was- in Maine at least- the birth of the torpedo stern lobsterboat. I have also read that the planks that were bent around the transom didn't like to stay there and were a maintainence concern. The remedy was to lop off the curved problem and build in a relatively square transom as a fix. Having said all that, I too think they are incredibly striking although frivolous. I noticed giant spray rails on the Rumery incarnation of the design at the Portland show so I guess that one really moves. I dont think Don found the pics from rumery's site but they've taken lines from the one pictured there
04-24-2002, 09:09 AM
What I'm looking at doing, eventually, is adapting John Gardner's hard-chine hull version (from Wooden Boats to Build and Use) to a family cruiser. I was thinking that the torpedo stern could be planked vertically (like a barrel) using tight-seam construction to avoid the bending problems.
Of course cold-molding or strip-planking (or the combination) could work, but I'm trying to come up with a design that would not be a huge puzzle later when repairs become necessary.
This boat would not be heavily powered, since my aims would be comfort and economy, not speed. So I'm not worried much about the stern getting squirrely when the boat gets up on plane.
The upside-down stability is one of my concerns with power boats. And it's not a discussion that I see often. I have several design books that talk about hull shapes, but none of them (in my menory) talk about hull stability and righting characteristics for the power boat hulls.
I see many such texts on sailboat hulls, but not power.
It was Eddie Kelley--a Jonesport Lobsterman at the turn of the century who was towing the overhanging stern model behind his peapod when it overturned. Kelley went to Roque Bluffs & had Morris Dow build the boat for him. Dow charged him $5 a foot for the 21' boat because the stern would be so hard to construct! The boat was named Blackbird.
My thought is: If a new design idea didn't work with the fishing method of the day it would not have happened. Lobstermen today fish multiple trawls as well as having powerful engines so having a broad transom, open or with broad deck, is important to handling the gear.
04-25-2002, 07:11 AM
Actually, the broad cut-off stern is more for stability under speed than anything. When you fish farther offshore and put out more traps, you need to get there faster and get through your line of traps faster. The boats HAD to evolve to the broad flat stern to handle the horsepower that was being installed.
The articles pointed out and sent to me are teaching me a lot! smile.gif
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