Rocker and Hook

[Desert68]

I just read a thread about a boat that had/has a porpoise/bucking issue. I have an idea of what hook is, but I don't believe I really understand it. I have no idea what rocker means. Could some pleae briefly explain the two regarding a hull? Do they apply to all typical hull designs? TIA
Desert68

[DeltaSigBoater]

HOOK
One of two conditions in the bottom of a planing boat that can lead to performance problems. When the boat is rightside-up, the bottom curves up from the transom; is "dished" forward of the transom. This "hook" will drive the bow down, reducing performance. Can also lead to the bow "bobbing" up and down. The aft section of the hull, seen in profile, should be straight.
ROCKER
One of two conditions in the bottom of a planing boat that can lead to performance problems. When the boat is rightside-up, the bottom curves up toward the transom. This will lead to "porpoising". A similar effect will result from "rounding" the trailing bottom edge at the transom. In the extreme and/or at high speed, this can be dangerous. The cause is usually caused by allowing the transom to drop during construction. The aft section of the hull, seen in profile, should be straight.

[Xlration Marine]

Hook is built into the bottom of the boat about mid ship. This will help it plan and some other some what secret things, depends on how much and actual placement of the hook. Rocker is just what it says, like a rocking chair. This is built into the bottom of the hull and on the back end. The actual start of the rocker depends the size of the boat and just how the builder wants the boat to run. Not all boats have these in them. The rocker will help give the bow lift and get more of the nose out of the water, faster boat. You will find it more in a Custom Boat, Speed boat application. Hope this helps. I would be more in depth but I would have to shoot you.Secrets ya know. But you need both one alone isn't much good. And then there is the angle of attack. Can't tell ya.

[ol guy]

Okay I give. A rocker is on the keel of a boat to load the pump, after the hook is set right to make the boat set right at speed, a hook is at the last 6 to 12 inches of the boat to push the boat down in the bow for better ride and faster plaining. If I'm wrong i would like an explanation.

[holorinhal]

Okay I give. A rocker is on the keel of a boat to load the pump, after the hook is set right to make the boat set right at speed, a hook is at the last 6 to 12 inches of the boat to push the boat down in the bow for better ride and faster plaining. If I'm wrong i would like an explanation.
:confused: ??????????????
Delta sigs explanation is pretty much right on.
Hook,where performance is concerned, is a concave shape (dip)in the area from the transom to 5'-6' foreward.Imagine if You have a set of trim tabs set in the down position. It would push the bow(nose)down making the hull rul with a more wetted surface,hence slowing the boat down.
Hook is hard to see unless it is extreem.But if You put a 5'-6' staight edge across the bottom of Your hull starting at the transom.If Your hull has a hook in it it will show up as a low spot ,somewhere along the length of the straight edge and possibly in more than one location.When checking for hook You should check many points within the 5'-6' area from the keel outward at all strakes and mid points inbetween each strake.
Rocker is the same as in Delta sigs explanation. A convex(dome shape)area from the transom foreward.
Some,but not all hulls,from what I understand, are puposely built with some degree of Rocker,for what I am uncertain.
Where speed and performance are concerned,Hook is a killer.
In order to get the most speed from a hull it requires that the hull runs more aired out,or with less wetted surface(less boat in the water) which usually means a bow up attitude.
Correcting the hook(Blueprinting the hull)removes the dip in the area 5'-6' foreward of the transom,making it flat so that the water along the running srface travels with less friction or interuption.
I am by no means an authority on bottoms,at least where boats are concerned.This at the very least My understanding of hook,from all the research that I have done before blueprinting My hull bottom.....Hal

[ol guy]

Okay that tells me what I thought and have done for over 30 years is right and I'll stick to it. Thanks for the insight. Mark

[Desert68]

Thank you for all the information!