Hatseflats Design
A 15ft Pram for Dinghy Cruising
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Hatseflats Hull Build

Fitting Out Hatseflats

Sailing Hatseflats

Building TooPhat

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20170427

In January I decided to have removable seats and floorboards on Hatseflats. My initial plan was to have slatted seats made of oregon pine or fir, similar to the Phoenix III design. However, the seats on Phoenix III only need to span 105cm. I am looking at a load of 100kg and a span of 160cm (which is twice the length of a bookshelf). I used the online 'Sagulator' calculation tool to calculate the deflection. You can find it at http://www.woodbin.com/calcs/sagulator/
When using okoume (MOE=7.9GPa), you need at least 35x4cm to span 160cm to keep sag below 0.25cm per meter.

Since solid planks tend to warp and slatted seats may not be stiff enough, I thought up a hollow 35cm wide sandwich of 8mm ply with 3 planks of 50x30mm acting as a core. This is much stiffer than the solid okoume plank. I may reduce the core to three planks of 50x25mm and stil have a margin over the solid okoume plank.

The floorboard sandwich of 56cm width is similar, with a core of 4 planks. The drawings show how the sandwich boards can be used as seats and as a sleeping platform. Alternatively, the seats can be taken out or put against the sides.



20170427_h4a_seats4sailing.jpg Seats and floorboard set up for sailing.
20170427_h4a_seats4sailing2.jpg Seat removed
20170427_h4a_seats4sleeping.jpg Sleeping platform using seats and floorboard