Friday, January 20, 2017

Header Photo: William F. Crosby "Pup" Dinghy

The previous header photo was the side view of Crosby's Pup dinghy, a V-chine design published in the August 1938 issue of Rudder magazine. What is interesting about this design is Pup is one of the first dinghies designed to be built in plywood. Even more surprising is Crosby specified 1/8 inch (3 mm.) plywood for the hull and decks. Crosby seemed to have no fear, this early on, in pushing the structural limits by using very thin plywood. (Designers post WWII such as Phil Rhodes with his Penguin dinghy would revert back to the sturdier 1/4 inch (6 mm.) plywood for the hull.)  To account for the flexibility of the plywood, Crosby added one fore and aft stringer and two smaller, intermediate frames between the major plywood frames.

The Pup dinghy may be one of those "missing links" I am so fond of speculating about in sailing history. I have always wondered what spurred the Australians into wholesale acceptance of thin, lightweight plywood for their dinghies designed after WWII. (The Aussies would even convert their pre-WWII plank on frame designs before WWII over to light ply, their existing VJ class and 12 meter Olympic Sharpie.) I received an email from a South Australian dinghy sailor two years ago and he mentioned that he owned an Aussie Pup built by a local builder in the early 2000's. He also mentioned there was a sizable fleet of Pups in the Melbourne area in the 1940's but they had died out.

Could it be that some Melbourne sailors, in building the 1/8 inch ply Pup before World War II, would become the impetus of the Australian revolution in lightweight dinghies? Certainly South Australian Len Morris with his scow Moth would have taken notice as he would produce his superbly engineered, light plywood Mk II in the late 1940's. It would be an interesting slice of dinghy memorabilia if someone could dig up some photos of the Melbourne Pup fleet in the 1940's.

For those that want more information, Steve Clark pointed out, in the comments section, the current builder of the Australian Pup has a Facebook page.

A JPEG file of the Pup plans as they appeared in Rudder magazine, 1938.


Alden Smith said...

Really nice little sailboat - as good looking as the Crosby catboats!

Alden Smith said...

..... I had another read of this post - It is amazing that 1/8th inch plywood was specified, this is not much stronger (certainly not more puncture proof) than a hull covered in painted canvas.

I love the old sailing magazines - they often used to publish plans like this complete with the table of offsets for any enterprising sailor to have a go at building..... and again, those Crosbys, they certainly knew how to design a pretty boat.

Unknown said...
Group in Geelong Victoria Australia has been developing a modern derivative.
Noty sure I agree with all changes, but someone is doiung something with this pretty nice little design.

Tweezerman said...

Thanks Steve! I pulled the link over to the main post.

Roger said...

Hi I am the person behind the fleet of pups that came back from the dead in 2000 . The pup class in Queenscilff Victoria au has never been built to original plans . The outside hull has been but internal has had many variations. Not long after William Crosby published the plans the local boat club at the time wanted a training boat .( queenscliff boat club now queenscliff Lonsdale yacht club ) But if the pup was built to plan a capsize in local waters would mean loosing the boat and possibly never getting ashore again so the hull was decked over with a small cockpit added for feet similar to a laser class dingy. This is not modifying the design as a bad thing as safety is important and in 1935 these things were not thought about. This means that the pup class then got a following and grew . Without this it would not have gone any further than a drawing of a vessel . Fast forward to 2000 I was a member of the club they again wanted a training boat to restart the dinghy section . I got a set of plans and built a hull then looked at how to make it practical , light and safe . Some would disagree that it is not per plan but many dinghy classes had to evolved to be useable . So that is what I came up with . Anyone that builds a vessel to 1935 design and is a purist does not consider all the facts also risks when sailing . Even the jack holt heron has gone through modifications to make safer . These early designers came up with fantastic designs but the down side was that the LWL was not correct due to construction methods. The total weight of the hull set it lower in water let alone with equipment and persons Also the safety of the occupants was not considered . In 1960s laws were introduced around the world that all small vessels must have enough buoyancy to float hull and crew to be able to bail or sail home .

Tweezerman said...


You are absolutely correct that Classic designs can be improved upon and the Pup, as originally designed as an open dinghy, was definitely made safer with a cockpit. I always welcome more photos of the Australian version. You can find my email address in the Profile section. Rod

Anonymous said...

For those that are interested I have photos of the construction process of the modernised pup class dinghy . On the pup fb page also some older photos . One photo in particular was sent to me from USA which shows a pup built to original plans as plans stated . I was planning to make it a kit / flat pack originally. But no one wanted to build them only sail . The patterns were made by building a half boat with the frames as per the original plans . This gave me the shapes of the panels . Like every ply dinghy since the mirror dinghy stitched and glue construction saves not only time , money or weight but material. The fleet of pups in Queenscliff Victoria au have now been sold off and gone . Pup 2 was given to me as a gift as I did not keep any I built . So occasionally I will post photos on the pup dinghy fb site of it . I can be contacted through the fb page if you want more info .