Yo guys

Oh boy, my expedition single is going to have a long drawn out gestation, but it doesn't matter, because I will get there .... e v e n t u a l l y.

I decided a regular 2 x 4 strong back was never going to be good enough. Mostly because I expect my build is going to be a long one and I would't want my strong back made out of our course grain NZ pine 4 x 2 warping at some stage - which it would almost certainty do. Also the strong back for an expedition single is literally a long one - being close to a 17 foot span - any sort of strongback is likely to sag a bit if not supported strategically.

So my answer was to make a box frame strong back out the 3/4 " chip board table that I used to sit my Guillemot s&gs on when I wired them up and handled the panels. It seemed like a good idea to whittle the old table up into an artificial 4 x 2 and it would be putting it into continued good service on the expedition single project.

I launched forward on my mission and soon ended up knee deep in saw dust. The beam came together very well and was very straight. But it sagged under its own weight (about as much as a similar length of 2 x 4 or maybe less) which wasn't bad, but also not good enough.

So I attached 2 lengths of steel angle bracing (1cm x 1 cm x 3.6 m) to either side of the bottom of the beam. This reduced the sag to next to zero, but gave my strong back a memory. Lifting it up side ways would give it a slight bend which would be held in shape by the steel reinforcing. This could be adjusted to straight and true with a little tweak, but didn't bode well for the expected frequent shifts during my build.

At the end of the day, I think my composite behemoth (did I mention it weighs about a tonne) would have worked, especially if I was working in a big space and didn't have to move it about. I am guessing that after putting down a few strips, everything ewould have tied together nicely. And my chipboard strongback (had the potential to be) laser straight and was never going to warp.

However, that wasn't going to be good enough for me as I am cramped for space and will have to routinely sling my forms up into the rafters. Besides I want my strongback/forms to be the ultimate rock steady reference for my expedition single during building and for the fibreglassing.

So I went out and bought some 1/2" ply and have almost made a 'proper' box form strongback just like in Nicks Book.

Moral of story

1. Nicks book is probably more valuable than people realise as an honest and accurate outline of how to actually construct a stripper for a first timer. I think I made a mistake thinking that a chipboard strong back would be easier/cheaper/better. Especially since the box form that I have (almost) ultimately built has all the instructions clearly written in black and white on page 70 - which I chose to ignore (dah!).
2. I think having my old chipboard building table around, complete, might just have been usefull for when I scarf up the sheer strips. I may yet have to go out and buy a replacement piece of chipboard (dah!).
3. Building box frame strong backs are nowhere near as difficult as I had thought. Having built two now, I am starting to think it is a doddle. Maybe if I make the ends pointy and make them a bit wider in the middle - I can sell them off as s&g kayaks when I am finished.
4. Box frame strong backs don't use up all of a sheet of ply, so you can use the left overs for gluing your forms to like the book says.

Cheers Pete