GW rounded keel

[Ekea]

When comparing the keel of the grady to the keel of other similar CCs, it is very apparent that many other boats have the keel come down to more of a point. the grady is very rounded on the keel. this is noticeable jut about along the full length of the boat. its only at the very front where the keel begins to curve up to the nose that grady drops the rounded profile.

does anyone know why grady did this and what benefit they did it for? conversely, does anyone know why other manufacturers bring the keel down to a point?

 

[Coastboater]

Here’s a good video that explain Grady hull design elements:

 

[everwhom]

Thanks for sharing that excellent video - I've wondered about the rounded keel myself!!

 

[Ekea]

good video. i would like to get a bit more detail about the statement that the rounder keep makes for a softer ride. the part about reducing bow steer makes perfect sense, but not so much about the softer ride

 

[Coastboater]

One thing I’ve noticed on my boat that WOT it feels a bit “squirrelly“ for lack of a better term. I think it’s due to the hull not tracking as straight as hulls that carry the deadrise to the transom when you’re only riding on the last few feet of the hull.
I didn’t experience that on the 228 with a F225 on a bracket, nor on a 225 Tournament with a F300, also on a bracket, although not sure if the bracket makes a big difference, but both brackets had “V” shaped bottoms. I think it has more to do with trimming more of the hull out of contact and higher speed creating more lift.

 

[Ekea]

One thing I’ve noticed on my boat that WOT it feels a bit “squirrelly“ for lack of a better term. I think it’s due to the hull not tracking as straight as hulls that carry the deadrise to the transom when you’re only riding on the last few feet of the hull.
I didn’t experience that on the 228 with a F225 on a bracket, nor on a 225 Tournament with a F300, also on a bracket, although not sure if the bracket makes a big difference, but both brackets had “V” shaped bottoms. I think it has more to do with trimming more of the hull out of contact and higher speed creating more lift.

could be that the outboard on a bracket acted as a rudder farther back, essentially stabilizing some of the speed induced yaw

 

[Summertop511]

Always wondered about the rounded keel

 

[DennisG01]

All good info to think about and ponder. I wonder -- ponder -- there are other boat companies that have excellent R&D and engineering departments... and said companies do NOT use a rounded keel. Coudl the difference, in reality, between a rounded/not rounded keel be so insignificant as to make no difference? I hear what they're saying in the video - but I also tend to take those kinds of things with grain of salt as there's, inherently, going to be some salesmanship in the info. That's not to say it's "bad" salesmanship or misleading - far from it - just that there might be "some" embellishment

Just an outloud thought

 

[DennisG01]

Holy crap I used a lot of smilies in that post!

 

[DennisG01]

Darnit... did it again!

 

[seasick]

A hull with a flat bottom ( really flat) will be the easiest to get on plane. It will however not handle well and will tend to pound in chop. When the hull starts moving over the water,, as the water fights to pass under it, air gets trapped and creates an air cushion. The air cushion reduced the drag, reduces the wetted surface area and 'lifts' the hull up out of the water in a way. If instead you had a sharp V shaped hull, the rushing water will pass more easily around the sloped sides of the hull since there is less resistance (drag) as would be the case of a flat bottom. There is no air cushion or at least a lot less air cushion and that means that the hull will be less prone to get on plane. It's all a compromise.. Of course a rounded hull in the extreme case will tend to roll ( think of a long log with you standing on top Compare that to you standing on a surf board.

 

[Peter A]

Well that video was a GW commercial. I do believe a rounded bottom will give a softer entry, that makes sense. Twice Sorensen mentioned a good ride down sea, yup. Noted that he mentioned hull designed to run 30mph. Yup. Give a dry and stable ride, and predictable handling, yes. Not rock too much at rest, yup. Decent mpg and doesn’t take huge power, yup. A good all around fishing or family boat, for sure.

Every hull design has trade-offs, I am pretty happy with SV2 hull. Grady knows their customer pretty well.

 

[Sardinia306Canyon]

My 98 BW 23 Outrage had a very round hull at the stern and it rode like crap and definitively nothing at all about soft entry.
It is my believe and experience that the softest entry is from deep v hulls what allows them to speed at 30 Knots + on top of the waves as the deep v slices thru the wave tops when a GW would slam and a flat bottom like a old BW Montauk let your teeth fall out.
However, the deep v hull is not the best at all, it's a special purpose hull for special purposes and that is speeding 50 miles+ out to the fishing grounds and in case of adverse weather back quickly. But that comes with a few backdraws,
bad fuel efficiency
rolling at drift
the need to go fast to stabilise the boat
can be complicated to install transducers, particularly transom mounted ones on single outboard hulls
such hulls with the now "needed" steps make it much worse

I am happy with the hull of my 306 Canyon, but have to admit that at least my hull does more plowing thru the waves than running on top of them as my last 30ft RIB did, but only at 35-30 knots.

MY BW 23 Outrage became very squirrelly at 48 knots, my Canyon is much slower @ 5500 rpm but run as on tracks if weight distribution and trim is correct

Chris

 

[Ekea]

I do believe a rounded bottom will give a softer entry, that makes sense.

why? you say that a round keel will cut through a wave better than a sharp keel and give a better ride? can you explain that?

 

[family affair]

My guess is that the round keel is the same premise behind the sv2 hull.

 

[Mustang65fbk]

I think my biggest question about the video would be if Sam left his shirt in the glovebox of his car overnight and then pulled it out right before shooting the video.

 

[DennisG01]

I'm still going with... "it's close enough as makes no difference"

 

[Peter A]

why? you say that a round keel will cut through a wave better than a sharp keel and give a better ride? can you explain that?

Point taken, not precise language.

No I don’t think it will cut through a wave along the entire keel. Not going too fast and especially running in a following sea, rounded bottom helps achieve a soft landing. Head sea and going really fast, not so much. But hey I am not a marine engineer, just a boat driver. I know how my small Grady lives to be driven (bow down to cut the wave, not too fast), and I know how the end-to-end deep V boats I have actually run prefer to be driven. For me it’s all design for purpose and the trade-offs to hit that design goal.

 

[PointedRose]

I am thinking that the rounded part is designed to displace whereas the sharp vee is designed to slice through. GW designed a combination. I am thinking about the large tankers with the rounded nose on the bow underneath the water to displace/push ahead of the hull. When on plane for a GW that rounded section is initially displacing on entry for a brief moment then quickly cutting through to spray outwards. Also maybe helps provides lift when launched deeper in - it’s not going to slice down as much and the displacement design will steady the porpoising with the other hull features. Or maybe I am way off base.

 

[Ekea]

Point taken, not precise language.

No I don’t think it will cut through a wave along the entire keel. Not going too fast and especially running in a following sea, rounded bottom helps achieve a soft landing. Head sea and going really fast, not so much. But hey I am not a marine engineer, just a boat driver. I know how my small Grady lives to be driven (bow down to cut the wave, not too fast), and I know how the end-to-end deep V boats I have actually run prefer to be driven. For me it’s all design for purpose and the trade-offs to hit that design goal.

i can get on board with this. the rounded bottom could prevent slicing too deep which may limit shooting back out of the water because of going too deep in