Practicing lofting frames - any feedback?

[hamilton]

Hi there:

 

I've been building wooden ship models for about 6 years now, and am starting to think about getting into scratch building (despite having several kits on the shelf!!) I've been looking into tools and looking through some of the scratch logs here and reading as much as I can in my few spare hours. 

 

One of the great mysteries to me has always been translating line drawings into frame templates. I read the articles here, which at first made me feel like I was back in freshman year trying to figure out what people were talking about. But, as in freshman year, after reading the same and similar things some of it began to click, so I decided to start experimenting with lofting frames from my MS Kate Cory plans, which include all the necessary hull line drawings (body plan, sheer, half breadth). These experiments are not really aimed at producing anything, but more just to gain familiarity with the process. The technique I'm using is derived from Gene Bodnar's Bluenose practicum. I'm posting here and showing some of the process and results because I'm hoping that some of you pros out there might be able to direct my efforts or provide some tips for improving in the craft. 

 

Anyway, my first step was to late the frames - this I have to say was largely guesswork - assuming that at 3/16" scale the Kate Cory's frames would be 3/16" wide. Because I'm not interested in actually building the KC as a p.o.f model, I just positioned the frames 3/16" apart. Again, it was more important for my purposes just to locate frames than to achieve accuracy - clearly I would not take this same slap-dash approach on a proper build. Here's the sheer and half breadth with the lines drawn on, followed by a shot of the body plan with the buttock and water lines extended to highlight the grid.

 

 

 

I wanted to test out my proportional dividers, so I decided to scale up the lofted frames to 1/4" scale. I set the dividers to 1.5 and then began to reproduce the grid from the body plan on the sheet of paper, using a steel ruler and a right angle ruler to square it off. Here it is in process.

 

 

Once I had marked the centre line, the base line, the buttock and waterlines and the width and depth of the keel on the grid, I returned to the plans. The stages of lofting the frame were as follows. Frames "J" and "12" were used as samples

 

1. Referencing the half breadth plan, and using the proportional dividers I marked the distance from the centre line to waterline 1 at the aft edge of the frame.

 

2. I then transferred this measurement to my grid by placing one side of the dividers (on the scaled up side) on the centreline of my grid where it intersects WL 1 and placed the other end of the dividers on that waterline out to the starboard side and marked the point on the grid.

 

3. I did this for all the waterlines.

 

4. I then referred to the sheer plan and, placing the dividers on the baseline at the aft edge of the frame I measured up to (first) the deck line and (then) the underside of the cap rail and marked these on my grid at about buttock line 4.

 

5. I then took these same locations from the sheer plan, and marked them using the centre line on my grid as the starting point - this game me the location of the outside edges of the deck and the rail.

 

6. I then connected all these lines into as smooth a line as possible, defining the outside of the frame.

 

7. I then made another assumption, that the moulded dimension of the frame at the rail would be (at scale) about 1/8" and at the keel about 3/16". These, again, were meant just to give me a basis for my practice rather than to achieve any accuracy. I marked a point 3/16 up from the bottom edge and 1/8 in from the outside edge of my drawn frame at the rail and tried to draw a line as parallel with my first one as possible. This gave me an approximation of a frame.

 

Here are the results of the evening's efforts....

 

 

Anyway, I don't know if this gives those of you who really know how to do this stuff enough to go on, but I would love and appreciate any feedback, commentary, suggestions, constructive criticisms or pointers that you may have to offer. Sorry for the lengthy post.

 

Thanks in advance and happy modelling!

hamilton

[Jaager]

Suggestions:

 

Draw your grid on the white side of a piece of thick poster board.

 

Tape a piece of transparent drafting velum or a less expensive substitute:

Bienfang Designer Grid Paper, 50 Sheets, 8-1/2-Inch by 11-Inch Pad, 8 by 8 Cross Section

( $7.00 at Amazon )  The lines are straight and the grid perpendicular, but the grid is not precise.

 

The center line, keel line and base line transferred ,  but you can leave off the waterlines and buttock lines for each frame - just the frame points are needed.

 

Only plot one side of the frame. 

Scan the half frame into your computer.

Have a transparent metric ruler in the scan.

Open the scan in a drawing program - Photo Shop - ( has a rental online deal - if you are quick, you only need a 1 month rental) / Paint Shop Pro / I use Painter 12 - older versions like Painter 8 work just as well - I just needed 12 to get PNG in/out.

The program needs layers. 

Open the half frame as a layer, duplicate it, flip copy horizontally and position the baseline/ centerline and combine the two layers. You now have a precise mirror of the half frame.

 

Kate Cory would probably be framed French/American style -  paired frames with the space between +/- half the thickness of one of the pair.   I round - I am working on USS Vincennes 1825  R/S is 26"  Given the range of sided dimensions of the frames I chose to make each frame 10" and the space 6".

 

The point ?  You can use the middle frame shape layer for both outlines of the pair.

 

The metric ruler part - scan in - print out - can be altered by the computer-  Matching up the print out of the ruler with the ruler- the % change in document size needed to be done in the drawing program  to get identity in size is easier to calculate using metric an English scale.

 

Another advantage - colored lines are easier to follow when cutting out and shaping the frames.  With a paint program, it is easy to magic wand a line and change its color.

I make the dead flat centerline shape = red - next one = green, the next one = blue, the next = red....

The paint program color picker has a slider for each of the three colors, so they are easy to set - 

255/0/0  then 0/255/0 then 0/0/255.

Edited October 12, 2015 by Jaager

[druxey]

Hamilton: I'm sending you some information by PM.