hull rocker shaping

This is from an old Paul Gross post

From rail to rail there is a flat area about 10” wide that runs from the tail forward through the mid section then feathers out blending into roll. As well, there is a flat section that interrupts the rocker curve starting from the back of the fin box moving forward about 18”. This type of bottom contour combined with the way the board is foiled makes for smooth rail to rail surfing. Hard driving bottom turns and large radius turn backs.

Also LeeV posted rocker for edge board he made a couple years ago

Rocker 4 (to 18) then flat to 24 up from tail to 1 1/2

My Spence has a flat area comparable to PG’s comment but hard to spot as whole board is pretty flat so it goes (on way back from nose) from slight curve to no curve to slight curve.

I drew on paper a rocker template more or less matching LeeV’s and it do look strange. I blended in the breaks but still…broken rocker lines sort of hurt my eye.

Is this in fact the way to run rocker in a Liddle style hull? LeeV’s does run quite a bit longer, in fact almost 3 feet of flat thru center of board.

I’d love any comments/suggestions on rocker distribution in hulls and how this effects the ride vs a more “standard” though flattened 3 stage but blended rocker with no dead flat areas except perhaps the last few inches out the back.

Water does love and cling to curves, until it separates in a turbulent. Flats in hull rocker and overall design seem to me to compensate for the curvier elements. Running the rocker flat out the initial hull curve is one way to neutralize the separation off the initial hull rocker curve.

Don’tcha want cling ? That word could mean drag or it could just mean smooth transit. Turbulance is drag for sure, yes…?

You want cling, and you want as little accompanying separation as you can possibly get. Separation happens off big curves way quicker and more uh, catastrophically than off flats or flattened curves.

Nah… Paul didn’t say that! :wink:

BTW, the flat area that interrupts the rocker curve should have no noticeable transition point… which makes it easy on the eyes. May be why the Spence flat area is hard to spot.


Yes, transition is very smooth also, the curve of the rocker is not great only changing 3.75 inches from nose on a 6’10"

Watch out with my rocker! It’s not really a Liddle-like rocker (if there is such a thing). It was used on my edge board which was more a reflection of Greenough’s kneeboards with some “kick” in the tail rocker to compensate for the lack of flex in a stand-up board. The 1.5 inches of tail rocker was mostly in three stages. Verrrry crude.

The more blending you do the easier it is to ride…kinda spreads the sweet spot out more.

thanks for the heads up Lee. I emailed the man himself…Greg Liddle and he was kind enough to answer that yes, his boards all have a “break” in the rocker. No proprietary details of course.

Been busily drawing curves on paper. Got a nice outline. Funny, can’t draw round noses that look right. Have tried numerous times…so this one will have a point. Has vague similarities in outline to GL’s M3P on his site.

Next up another rocker template after more contemplation of the Spence board and soon as my nichrome wire comes get the hotwire to work…

Don’t be breath holding for visuals but they will come.

would you like the template from my 7’8" v-bottom? it has a pulled, but nicely rounded nose…

Matt, I apprectiate the offer…the board I’m making is considerably smaller…though the curve might be helpful in drawing…

The difference is really only in the very front 6 -8 inches or so. That part is seldom in the water? More an aesthetic difference or performance issue? Hmmmmm…?

Oh, duh! I have a template w/ nice round nose…my Spence 6’10". The brain does work in mysterious ways. Thank you for the offer and Matt and thank you for pointing me in the easy direction! I’ll trace that off and see how the curves work