Grob,

I was talking about toe-in stiffness as a measure of material stiffness not about "beam landing stiffness" as you call it.

I actually did the number crunching on the beams already.

I can tell you that the vertical stiffness is mainly the result of the beams and beamlanding fixtures both in bending and torsion.

Toe-in stiffness is a different matter here the hulls themselfs are the dominant factor. It may be relative easy to flex the beams in bending and torsion but not the direct axial compression. 600 kg axial compression on both beams (toe-in stiffness measurement) result in about 1 to 2 mm length difference between the beams resulting in less than 5 mm flex at the bows. The toe-in measurements showed 25 mm - 40 mm toe-in flexing at the bow tips in various designs. So it isn't the beams that is the cause of the toe-in flexing.

In vertical flexing like I have expressed earlier that the beams are the dominant factor with some noticeable contribution of the beamlandings themself. This includes the area around the beamlanding that has to transmit the loads. I know very well how a less then tight bolt on my P18 would kill the stiffness. I tightened them once every 2 months. On my P16 I had a small soft spot under a beam bolt ring and that sure didn't help stiffness.

But then again the point of the post was to show that ply (timber) isn't really as old-fashioned as many think. With building care a superior boat can be build using this methode and the Blade F18 numbers show how much superiour you can be. In the Taipan area the bare timber boats (no glassing of hulls) came out equal to the glass boats. I won't say where they ended up in relation to big beamed boats like the big builder F18's.

Also I have already wasted time on the beams, I actually have an excel sheet that runs all the math for me on beamflexing and the resulting bow tip movements.

Wouter