Building a Foam Core Powerboat

This site will report on the building of the 'Hawk41', a 41ft sea-going launch. It's specifications are: - Length: 12.50 m - Length waterline: 12.07 m - Beam: 3.27 m - Draft: 0.75 m - Displacement: 4.3 t - Engine Power: 184 kW.
The vessel will be constructed from a foam core sandwich using the 'controlled vacuum infusion' technique.

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Location: Utrecht, Netherlands

Monday, June 16, 2008

Working at the table

After working with Adrie for some time, I learned a lesson: Infusion is not the way to go to make simple small parts. To infuse a panel of, say, 10 square ft, leaves you with a relative big quantity of resin in the overflow bucket. In such cases the method is not only cumbersome, but also expensive.
A better way is to make such panels on a 'vacuumtable', which is in effect little more than a table that has an airtight surface. The panels are made by hand lay-up on the table and immediately covered with a bleeder cloth and vacuumfilm that is glued to the edge of the table with 'tacky-tape' (butyltape). After that vacuum is applied to the whole package and the resin is allowed to cure before the pressure is released. The result is absolutely comparable in quality with that of the infusion method. As I do not have to handle or move the panels during this process, it is clean too. Of course I handle one side of the panels at a time. After curing they are turned over and the process starts again.
I constructed my table with two simple and cheap 'board doors', available at the DIY-shop for about € 24 each. I glued them together obtaining a surface of about 6.5 * 6.9 ft. Big enough to make almost all of my flat panels. I covered the table with one layer of 450 gr biaxial glass and epoxy resin, to make it airtight. I ran a test before actually using it, and it turned out to perfom amazingly well: It took three (3!) days to lose the vacuum after I had switched off the pump.
I expanded the construction by adding a 'rig' for a tent, covering it. As soon as I am ready with the hand-layup and the vacuum is applied, I set up the tent and blow in hot air. In this way the epoxy cures really well and fast.
To connect the vacuumpump to the table I use a suction cup from Festo. As it will not 'suck itself' tightly enough to the covering film alone, I found out that an old CD will do the trick: Punch a hole in the film, stick the disk on it with tacky and the cup will have all the grip it needs.
See you next time!

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