Modified Deep V

[jfblouin]

I'm in design step for building a all FRP 6,7m Zodiac look boat.

You can see one of my study design at
http://boatdesign.net/forums/showthread.php?t=6375 Deep V

For now, I'm looking for V design and I have somes questions at can you see at:
http://boatdesign.net/forums/showthread.php?t=5903 RBB

Yesterday I found this design



Progression boat said:"Hull type is a modified Deep V

Progression’s bottom design, starting at the transom keel, has a seven inch pad running forward. Working from the pad to each side, the design incorporates a 24-degree panel, a three inch lifting strake, a 23-degree panel, a three inch lifting strake, and a 22-degree panel ending with a three inch reverse angle chine. (where the side meets the bottom). This is Progression’s unique Variable-Deadrise Bottom. The benefits of a bottom with this geometric design, as opposed to that of a straight V-bottom, is a stronger and stiffer bottom, creating greater lift in the water. All this adds up to softer entries, a dryer ride, greater stability, and higher speeds in rougher water."

I find this approach interresting for me, but I dont want a high speed boat, only 30-35 knots top speed boat with soft ride and seaworthy.

What do you think about this design.

[intrepid71]

My understanding is that a convex bottom section will produce reduced impact accelerations compared to an equivalent concave section. I would consider the Progression section to be concave, with the higher deadrise inboard and the lower deadrise outboard. I would recommend reversing that if your really want a soft ride.

[jfblouin]

I dont realize that will give a concave section and you have reason. I will calculate a convexe section with the same principle. Thanks a lot. I make a big step forward.

[ClarkT]

Shouldn't the convex hull wetter with much higher drag? There must be some data out there on this, but I have not seen it published. Anyone know where to find it?

This variable deadrise angle is very similar to the old SeaCraft 21 hull geometry, which was quite revolutionary in its day.

[jfblouin]

I try to design this test

22 degres bottom, 26 degres middle, 30 degres top

http://boatdesign.net/forums/attachm...tid=2530&stc=1