Posted by John Nichols on January 30, 2003 at 19:48:58 from 165.91.199.202 user Mcneacail.
In Reply to: Re: Boat Plans posted by Jonathan Labaree on January 30, 2003 at 17:38:18:
More:
Well I spent several hours last night getting a hull design program to work. I finally gave up, and went home. After a few hours this morning, and a lot of measurements of the AR sketches, and then comparison to the pictures on the web, I had the data that allowed me to create a hull design for an AR Boat.
The real problem is that the boats that AR sailed in (IMHO) are not the same as the boats he has drawn in the sketches. Close but not quite. I think the Swallow is closer but ......The interesting thing about the sketches is the reasonable consistency of dimensions or ratios between the sketches. He obviously had something in his mind when he sketched those boats, compare the picture "Do you surrender in SA" with the pictures on Mr Weir's site of the real Amazon to see the differences.
Mr Weir's site was back up again this morning, and so I could cross check the figures I had calculated with his notes. AR also drew several perspectives that give good angles to get lengths etc.... My figures were only a few odd inches off Mr Weir's figures. Once I had the hull made I could compare the waterlines to what AR had drawn and calculate the mass in the boat. I found that I could create a WRL file which allows me to 3D the model from the hull design program. If you download a VRML add in to Internet Explorer you can look at a rendered model of the hull. (http://www.parallelgraphics.com/) has a nice one. I have enclosed the files. QK 20 is the real design.
I also created a JPG file from the AutoCAD drawings.
So I thought I would share them with you. I had fun, although I lost a bit of sleep over getting the hull program to work.
I also played with a narrowed down version to replicate Amazon and see if there was a hull speed differential. There is a difference of about 1 km/hr in the hull speeds by taking about a foot off the total breadth of the boat. The keel in the Swallow would also slow the boat with drag. I seem to remember in one of the books John was moving everyone about trying to get the boat to move faster. He had the disadvantage of 2 extra bodies that would not have helped, especially if it put the transom in the water, which the picture in SA "The start of the voyage" shows.
I played with the capacity stuff and the Swallow could take about 2000 lb or 1000kg before she goes under. So she is a good work boat. The CB stays just aft of the center, which is the right place.
I am going to build one so I can sail with my daughters 12 and 8. But I am thinking about the compromises to modern boating for children and safety.
They are two girls, so I can definitely argue that she should have a centreboard. The ballast is a safety issue, and she will need buoyancy tanks. Eliza would want a speed machine, so no ballast maybe or bottom boards. I need to give her a name so I will call her the "Eliza Charlotte". And as she is neither the real Swallow or the Amazon, but a copy of AR's plans (as close as I could make them anyway) I will call her the Ransome Class. But the foot of the main sail has to be tied to the boom none of this modern stuff.
So there it is. Target launch date : Christmas 2003.
Thanks for listening.
Now to ring Fed Ex to get a price to ship a 250 kg boat to Windermere. I could email them. I wonder if the NAT Trust would stop a man camping on the Island if he came in a real Ransome boat.
I could die happy then.
John Nichols
(If anyone wants the images please send me an email direct.