Sunday, 7 June 2015

Daydreaming

I'm vaguely thinking of what to do after I finish Elena. Somewhere in there is building a house for Perry and I to live in, and then once that's done I'd very much like to build a boat to seriously sail in. Elena has me all fired up on wooden boats, so I'm looking around at possible designs for a 26-30 foot cabin cruiser. Not a fast boat, but rather something we could sail around Australia in or even cross the Tasman.

Like I said, daydreaming.

A boat that ticks a whole lot of the boxes is the Herreschoff H28, a design that's stood the test of time and is much beloved by those who build and sail them.

As it's quite an old design, some of the plan details are actually available on the web. Most notably the offsets, which detail the shape of the hull in three dimensions. I've spent some time over the last couple of weeks transcribing the offsets onto the computer, converting them to metric, and then using sketchup to loft a 3D model from them. Here's a few views of my model thus far. As with Elena, I hope to use this model to try things out, like interior accommodations etc.

Edit: Here's a view of the working that I used to loft this design. I started by drawing the cross shaped former, which I put on it's own layer so I could easily turn it on and off. Then I made a moveable "frame former" on which I can draw frames. I have lines at the station points on the initial piece, and move it around to draw the various lines from the offsets. In each case I move the former so that either a horizontal or vertical surface is where I need it, and rule offsets onto that. Then I use the 3 point arc tool to connect offsets and make fair curves, effectively interpolating between the offsets. Some mucking about is needed to ensure everything is fair.

Once the specified lines are drawn, I then slide the frame former to various points and draw smooth frames, by selecting the points where the lines intersect my former, again using the 3 point arc tool to interpolate between lines.

The frame lines now give me more points so that I can interpolate more WL+n lines. I do this every 4", or 101.6mm.

Finally the really tedious bit is drawing a huge pile of triangles to sheet the hull. Once the lines are drawn, they get selected, then the properties changed to smooth the hull over them. You can see I started with a 101.6mm grid at the bow, but got sick of it about 1/3rd of the way along the hull and swapped to a 203.2mm grid.

4 comments:

John Florance said...

Hey Suzy...

I'm constantly blown away by your productivity and workmanship. Seriously envious of your skills. Like you, I'm jazzed about boat building. And tho my skills are nowhere near your caliber, I'm daydreaming about "next boats". Love the Herreshoff...but have you looked into Paul Gartside's designs yet? I bought is "Plans and Dreams" book which has several of his designs in full plan sets as well as various essays on boatbuilding by Paul. I really really love the Gartside 29' cutter. He's done several iterations of this boat in various sizes from 20' to 30'...you could pick the one you like the best...

I haven't been as diligent about updating my blog. but my build is proceeding. I have the first coats of paint on the inside. I'm getting ready to set the seats and inside "decks", and working on my other spars in between coats. I have the main mast (with hinge) completed, my gaff yard done and the bowsprit and boomkin finished. Just need to hammer out the boom and mizzen components.

I'm also contemplating laying my decking in one of the various hardwoods to give it a more "yachty" look. Will probably do that.

I'll update my blog with pix in the next few days as I have time between work, travel, and kids' functions.

Keep up the good work. I'm very inspired by you.

JF

A. Jansen said...

Hi Suzy,

I like your way of using Sketchup for drawing a difficult form like a classic boat hull. It seems that you figured it out yourself how to do it. I’ve done the same when I wanted to draw my International Folkboat (Marieholm IF) in Sketchup. I only had some lines from an old folder and couldn’t find a tutorial about drawing such a hull in Sketchup. Apparently we did it about the same way with a lot of patience and thinking.
I admire your design and wish you luck with realizing your ideas

Ab

Sandro M. Passos said...

Fantastic job. I'm interested in H-28 drawings and construction too. Do you think to share the file on Sketchup 3D Warehouse ?

Suzy said...

Done. Search on "Herreschoff H28".

No guarantees on the accuracy of my model though - From memory I might have scaled it a little...