Building the Cosign Wherry

[finzup]

Has anyone who has built the cosign wherry had any issues with the Stem fitting station one and two of the strongback? My stem seems to be way short and it fits the plans perfectly

[Daddles]

All I know about the boat is on the website and I suspect most of us will be the same. How about you take some photos and post them - there are enough builders here to be able to come up with a solution, even if we have to make one up :D

Richard

[onthebeachalone]

Has anyone who has built the cosign wherry had any issues with the Stem fitting station one and two of the strongback? My stem seems to be way short and it fits the plans perfectly
There was a previous thread on this topic. Might include some helpful clues. http://www.woodworkforums.ubeaut.com.au/showthread.php?t=36316

[Boatmik]

Howdy,

this has come up before
http://www.woodworkforums.ubeaut.com.au/showthread.php?t=36316

There are error/s in the plan.

see
http://www.amazon.ca/gp/product/0917436024

MIK

[Wild Dingo]

There are error/s in the plan.

MIK


Ive not taken much interest in the wherry as its not my sort of boat but I gotta ask... Were they intentional errors Mik? I have experienced quite a few sets of plans that had what the designer said on contact "intentional mistakes or errors" this in their view was to make the builder CHECK their lines and the offsets BEFORE they started cutting... generally Ive found most plan sets hold at least 2 small errors generally in the numbers of the offsets that although small and seemingly insygnificant if not cought and sorted EARLY can end up bein major pains in the ass when you get down the road a tad with building.


Al Mason made some small mistakes on the Sorkust and Minna... Bud MacKintosh dis the same in Meadowlark George Buhler has several on his large schooner and Troller designs as did Mac McCarthy with his two wee lassie canoes if memory serves the set of early plans of Grey Seal by Iain Oughtred also had ONE mistake or error in the drawings and BB Crowninsheild had several wrong numbers in the offsets of Fame and his Dark Harbor plans...easily found and remidied IF ones looking and checking as they go

Just wondered if that was one of those?

In talking with a quite a few blokes who have never built a boat before and have gone into it all gung ho then become bogged when they hit a wrong number in the plans or offsets... simply put one should always check the numbers as you draw out the lines... if one set of numbers in the offsets LOOKS wrong or way off compared to the others check them!! if one can get hold of the designer and ask them what the go is but always check them... when I drew out Valgerda by Atkin I found several errors in the offsets as I laid them down but with trusty length of 1/2in x 1/2in Jarrah I simply laid the turn until the peice of Jarrah laid nice and fair and marked it at that when the laying of the lines was done all was fair... ol Atkin not bein of the breathing genre it was a tad hard to ask him... so checking the numbers laying the lines should show any glaring anomalies

Not sayin this bloke didnt (and theres no pics yet either) but that seems more often than not the problem.

[Boatmik]

Hi Dingo,

Where have you been?????

(no excuses - I've been off to Sydney and returned so have not been posting regularly.

The cosine wherry has full size plans on paper - so I don't think the mistakes are deliberate - but they have been in the plan since it came out - I've known of the book they come in for at least 19 years.

So figure?!?

I consider full size plans an abomination and like many abominations are the sites of frequent miracles. FULL SIZE PAPER PLANS fuelled the home boatbuilding revolution in the 50s and 60s and have resulted in lots of boats being built.

However the problem is that the paper moves quite a bit. Up to half an inch per foot depending on humidity.

So if you have paper plans for a boat part that is 5ft wide ... it might be 5ft 2 1/2 inches wide on a damp winter day.

So you would never use paper plans for something that has to fit a specific measurement - like a class racing boat.

But despite this - plenty of these boats are built and some really good designers use them - eg Iain Oughtred.

I just consider it a miracle.

I think part of it is that most of the parts for a boat get drawn up over a short time frame - which means the paper doesn't move too much during the period of use.

As far as deliberate mistakes. This is something I have never heard about - it might be a tradition that no-one has ever bothered to tell me about!

At any rate it is irrelevant to me - I produce all my drawings on computer and they are accurate (unless I make a big mistake) to much, much less than a millimetre because the boats are modelled full scale.

With a traditional paper drafted drawing it is very unlikely the drawing that is being worked from is much longer than a couple of feet. So everything has to be scaled up. That would give you an idea of how accurate those 8ths of an inch are in the table of offset. For a 8ft boat they were probably a 1/32nd of an inch or for a thirty footer they were 1/240th of an inch.

Another miracle!!!! They still work - but it is very easy to make some mistakes. So lofting is recommended by designers where the boat is drawn up full size on a floor or wall somewhere (or on cheap sheets of chipboard.

With cedar strip boats it is possible for someone who knows about fairing 3D objects to cheat by making the mould directly from the offsets - and correcting any mistakes in the shape of each mould they find there.

Then assembling the moulds onto the strongback and fairing the whole caboodle longitudinally using a long batten and four hands!.

Any bits that are too high can be planed down when carefully located.

Any low bits can by marked prominantly in black permanent marker to remind yourself that when the strip passes over that area that it must not be nailed down flush with the frame but allowed to spring off the surface to retain its fairness - after each cedar (or paulownia or whatever) strip is a nice little fairing batten on its own so it is easy to see whether it is running a fair line.

This can sometimes be done with ply designs if you put up the moulds and then run the chine logs and keel and space the chine logs and keel till they run fair. And then allow the sheeting ply to ignore the moulds completely. You can fillet up any gaps later or shape edge cleats out of the framing stock to fit inside - wouldn't really recommend it though for big or expensive boats!!!

So as you can see there are lots of potential ways things can go wrong but boatbuilding is quite tolerant of them - mostly if you use your most important tools - YOUR EYES - to make sure that everything is running fair at each stage.

Michael Storer