Friday, 3 February 2017

Into February - progress with the projects

Lowen Plans

"In response to a request for a set of plans I am currently learning how to use Turbo Cad in order to do this and am also planning to build an epoxy ply version. I have drafted the plans for this in Freeship and it is simply a matter of finding the time to put it together."

This is what I posted on the previous blog, however it has been more than: "simply a matter of finding the time to put it together".
"Freeship" is a lovely little boat design programme, however it takes a bit of an effort to produce really accurate work with it, for example:
The Lowen is built from the gunwales in that all of the frames are fitted to them - like a traditional kayak. Thus it is important to ensure that the line of the gunwale is plotted as accurately as possible. This line is produced when the two gunwale pieces are bent at 12 degrees off of vertical around the edges of the frames, the shape of which is a function of the outline plan of the kayak. It can be worked out quite simply using tangents and the half widths at each station, but then adjustments have to be made for the stern rake of the boat - this is what helps it remain directionally neutral in wind. I did measure this curve as I was building the boat and fed any variations back into the design, but it was difficult to be really accurate.
When I started to draw the frames accurately in Turbocad I realized that the gunwale was not always at 12 deg to the vertical at each frame, thus distorting the line (it is not possible to measure this angle in Freeship). Thus I had to correct the design accordingly. I was able to check this using the "develop plates" function, in which the programme calculates the shape of flat plates used to construct the boat (used to cut the panels in stitch and glue construction). When they came out horizontal I knew they were plotted right. Although a few millimetres out here and there was as good as I could get.
In order to draw up proper plans from the offsets etc from Freeship I use TurboCad Deluxe 2D/3D, currently on version 20. It has very limited 3D capabilities - for that you need to pay over £1000, but for 2D work, which is what I want it is perfectly adequate. However the training material provided with this really good programme was disappointing and I struggled until I came across a superb manual by Jeffery N Harrod
Although health problems have delayed publication of the manual for the TurboCad v 20 (to be sent free of charge when completed) I am doing well enough on the v 19 manual.
I emailed a trial batch of the corrected Lowen linesplan to my local printer today; this is the result, a start:

The Slalom Project
I purchased a mould a couple of weeks ago:

I am going to let sit there until the weather warms up, partly to let the hull settle down. It was quite lightly built in order for the slightly convex section "pop out". Unfortunately it was stored on the a flat surface so that it has a few "wobbles" in the bottom. I want to enable the shape to organically restore, perhaps with the assistance of some weight in the central area where it is a problem. Otherwise I will need to do some fairing. Pleased with the shape though, although I would have liked more volume. I do like the sheer.
I won't be doing anything until the buyer collects the outrigger to the right of the picture.