EJ posted the message below up on boatertalk and I thought I would post it up here for anyone whom might have missed it on BT. The write up is quite informative:
andquot;It is VERY non-productive to consider all planing hulls and all displacement hulls the same, just FYI. Many boats have andquot;chinesandquot; or lines that are where drop chines would be on a playboat but it doesnand#39;t make it a planing hull (like the old Hero, and many creekers and river runners.
So lets start with that:
1. A planing hull is more flat than round- goes flat to the ends of the boat. David Knight, my design partner added the andquot;Drop Chineandquot; in 1997 to the X boat and that is something youand#39;ll see in many planing hulls now days,as well as many non-planing hulls (they arenand#39;t mostly flat or flat to the ends)
2. A displacement hull is mostly round and if it has a flat area, it isnand#39;t flat to the ends.
Finally, what is flat? Take a straight edge and put it across the hull. If there is more than .75andquot; of distance between the andquot;chineandquot; and the straight edge- it isnand#39;t a planing hull and from a performance standpoint, canand#39;t be considered flat or planing.
So why would we put a displacement hull on a Rocker and a Planing hull on a Hero?
1. Landing flat on big waterfalls- displacement hull, designed properly will land softer, be safer.
2. Displacement hull is easier to maintain the shape and is a stronger shape, good for creeking.
3. Displacement hull takes hits from the side with less chance of tripping than a planing hull- better for when you are going fast and on rocks.
Better for river running, because
1. Better zip across waves for ferries
2. more initial stability- assuming all else is equal
3. better control in holes if you do get stuck
4. better play for surfing, by far.
5. Better transfer from playboats to river runners.
6. Great for most creeking by intermediates or for hard ones by experts that arenand#39;t worried about landing flat on big drops, and the other benefits of a dispacement hull listed above.
Jackson Kayak (David Knight and EJ designed boats)
Hero- planing hull- oh yea- a Fun hull, Sweet!
Punk Rocker, Rocker, Mega-Rocker- Creeking to the 10th degree, sweet!
Continue reading here:
Displacement and Planing Hulls for Creeking