C-Forum

good points so how much of the crazy hull features on rotomolded boats are really there to provide stiffness

2opnboat1 wrote:Craig I was not bashing ez there but rather amazed that he know the difference between how the words are used in the sport and the real meaning.

I'm just curious who the designers are you were referring to... most the one's I know are ridiculously knowledgeable... and helpful as well.

2opnboat1 wrote:good points so how much of the crazy hull features on rotomolded boats are really there to provide stiffness

some are... and some features are just things that aren't going to work on an ABS or glass boat without too much hassle.

It's worth noting that the charicteristics of the groove and the hull both work together... as for the operating principles of the tri-hull to hold, the water needs to form a laminar flow parallel to the groove.

If the hull shape isn't reasonably smooth then the boundary layer separation effects as the water passes the rocker transitions will create an area of turbulant flow which precludes the required laminar flow continuing along the length of the chine.


It's also about getting the groove where the flow is (or not)...
If any of you have seen a Pyranha 4-20 or Rev and a Liquid Logic Gus, you'll note similar grooves on each; on the 4-20 and Rev it makes the boat very responsive and edgy; on the gus, it (at first paddle) provides relatively little effect.

On the Pyranha's the groove follows the rocker profile along the very edge of the hull, where there will be a strong flow; on the LL the grove is a little above the chines of the boat, and cuts a straight line, meaning that if anything it's breaking up the smooth flow over the curves of the hull...

In practice, that flow separation actually allows the boat to break away from a carve and kick round when the boat is edged strongly, which is a blessing or a curse depending on how aware of it you are and what you're trying to do.

Thanks for the input. Since I'm a carpenter, I was thinking it may be for structural reasons, but it sounds like some performance is accounted for in the design and does have an effect, good or back depending on technique or style of boating your doing.