Progress of the F-39 build is going quite well. Although I’m building in my spare time for quite some years now, the estimated average building hours by Ian Farrier seems to be quite accurate and I’m still on schedule with this.
Last weekend the second main hull half has been foam stripped. The method of vertical foam stripping is one of the great inventions of Ian Farrier and after finishing 6 hulls it is still a pleasant job to do. At first it looks an intimidating job, but after the third strip or so one knows how it works. I’ve added the dry fix method, whereby the joins are being V-shaped with a small router and filled with a bog of microballoons afterwards. My first goal with this technique was the insurance of getting an airtight foam hull that besides of the sandwich core is also the airtight mould for the vacuum infusion. The extra benefit is a clean job during the fitting of the vertical foam strips. However, there is a small weight penalty in comparison with a glue method of epoxy or a PU glue.
I don’t know the thermoforming qualities of other structural foams, but CoreCell is quite easy to bend with a heat gun. Even a very tight radius of say 2” is possible without burning the foam, which in my case has a thickness of 15mm (5/8”) The foam strips are consequently 405mm. (16″) wide, so three strips out of one 4’x8’ foam sheet. I started with using Philips screws but now I’m totally sold to the T20 screws, which are much better to re-use without damage to the screw head. A pity I didn’t discovered this earlier in the build.
In a few weeks I expect to vacuum infuse this hull part and I will report the list about that (for me) exciting event.
Meanwhile have a look at this YouTube video, made by the workshop webcam, to watch vertical foam stripping in practice. Even for such a large part as the F-39 main hull it’s an easy one man job.