>>>I don't know if a stiffer boat is faster - but that's not what we're trying to figure out here. I do know that I prefer the feel of a stiffer boat and it feels faster to me - but who am I? I'm really intersted just to know what makes a boat more solid with a twist thrown in for hull construction for the sake of conversation.


Good point !

Right now all I have to go on personally is what I know from my old P16 and P18's. Both of them were getting old at the end. P16 was from 1975 and the P18 was from 1986. Both of them had tendency to slack on the rearbeam and every now and then I tightened the bolts. The P18 at one time had a soft spot under a rearbeam bolt and one time I places thick and much larger washers under all bolts.

Just like Jake I can testify that the stiffened boats sailed alot more enjoyable. It felt faster. I have no data however that it is faster EXCEPT when sailing in considerable chop. The difference was so noticeable in chop that I know for sure that a tight and stiff platform is faster there.

The stiffened platform would punch through the chop and keep speed up. When they were more flexible they tended to hit the chop, shake considerably, halt and then accellerate again. We can get some serious chop overhere where I sail. Well it is more like short stubby waves with a wavelength of about 10 to 15 meters.

Eventually I would tighten the bolts when I saw that the chop was present on the race course.

I need to say however that the the holes in the beam were worn out a little, so that a only slightly looser bolt quickly allowed the beam to move over the hulls. So the magnitude of gain due to tight bolts may have been greater on my boats than on newer ones.

There is another thing I believe in (and I say believe intentionally) and that is that a stiffer platform has better dive recovery. I noticed from stiffening up my old P16 and P18. But it also makes sense. When the leward hull bites so to say a stiffer platform drags the luff hull in quicker as well. Often this results in a more direct application of reserve bouyancy. The speed of the biting is important here. A more flexible platform take longer to bring the other hull in and the deflection between the two hulls can be quite large at such shock loads. Again it is a believe, I have no scientific data. However I was far more comfortable pushing the boat and I certainly pitchpoled less.

Maybe it is like flexibility in your steering colom of your auto. A good driver can still go fast with it by learning additional mental skills (I know control computers can) but a sharp and crisp steering colom allows less skilled drivers to go just as fast. Pretty much people don't like controlling systems with delays and overshoots. The human mind is best adapted to systems that approximate pure integrating system. (can you tell this part of my field of study)
Systems that are "less stiff" have noticeable higher order components that appear to the human mind as unpredictable or to complex to control easily. The result is sloppy control where a human being feels insecure and uncomfortable.

It all is an interesting topic though.

Wouter