Sunshine Yacht Tender Model #2: Lofting Pt. 1

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Blog entry by kharder posted 03-29-2010 03:08 AM 2908 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 1: Getting Started Part 2 of Sunshine Yacht Tender Model series Part 3: Lofting Pt. 2 »

I started the process of lofting, drawing the 3D shape hull from front top and side views, based on the measurements from the plans using a scale of 2” = 1’. I have followed the same process that is required for a full size hull, but my scale will result in a hull 21” long and 8” wide.

To create the full sized enlargement of the lines of the hull, the plans list points along the various curves which are carefully laid out on a grid and connected with long flexible batons to get nice fair (smooth) curves. The plans list the points to the 1/8 of an inch but at my scale that is almost 1/64th of an inch. I created a spreadsheet that does all the conversions and lists the new points in 1/64ths of an inch to help minimize errors.

I am using a 24”x48”x1/4” sheet of MDF as my drawing board and some left over primer which leaves a dull white surface that is great for drawing small pencil lines.

The first step is to lay out the grid as accurately and squarely as possible. This is the grid for the profile (side view).

Next I added a grid for the plan view (top down cross section parallel to the water line) which is parallel and offset from the profile grid.

A height from the profile and a width from the waterline become a point on the body plans (cross sections when viewed from the front) which is ultimately what you use to build the boat. Typically the body plans are drawn on top of each other. I am drawing each of the stations of the hull separately so that i can then cut them out and use them as molds for building the model around instead of trying to copy the lines from the lofting on to molds as a separate process.

I have only drawin the points and have not yet connected them. The proper workflow is to loft the waterlines first, then the profile, then the body lines.

A fair curve is more important than following the offsets exactly and when I go back to draw in the curves i will go in this order and make any changes to the points I have already drawn on the body line and then connect the dots.

When all three views agree with each other and all the lines are fair curves you’re ready to build!

Build Costs:
  • Plans – $45.00
  • Lofting– $5.00

Total Cost = $50

Build Hours:
  • Lofting – 12 hours

Total Build Hours = 12 hours

Next Steps
  • Complete the lofting

4 comments so far

View kharder's profile


19 posts in 2996 days

#1 posted 03-29-2010 03:54 AM

It is much easier, but maybe not much faster

I’m looking forward to finishing the lofting and seeing how well the offsets line up at such a small scale. I haven’t found a good baton that will take the small curves but keep a fair line.

View Dennisgrosen's profile


10880 posts in 3115 days

#2 posted 03-29-2010 09:49 AM

looks good sofare
can´tyou make a
thin balsa stribe
maybe wet
I have used that
a copple of times
whenI build R/c
aroeplanes with luck


View CaptainSkully's profile


1599 posts in 3558 days

#3 posted 03-29-2010 03:50 PM

That’s very cool. I can see the advantages of building a small version first (mistakes will be less expensive), but wow, that scale must be really tight. When you’re finished, you’ll have a really cool knick-knack. I’m very tempted to do something similar with plans from, but have plenty of other projects already queued.

-- You can't control the wind, but you can trim your sails

View kharder's profile


19 posts in 2996 days

#4 posted 03-29-2010 04:05 PM

At least half of why I want to build the model first is just to end up with something pretty to put on my desk. I wanted to go smaller so that if this does become the tender to a larger boat, I could build a model of that too and have them both in the same scale for display purposes (engineers like to think way ahead). Unfortunately any smaller would have made it much more difficult to build with the sort of accuracy that would bring out the problems seen in a full size build which is after all the other half of why i’m doing this.

At 2”=1’ scale a 33’ main boat would be almost 6 feet long, but maybe i could put it on a large mantel. Something that size I could probably make into a large RC boat or something.

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