Am I planing...or semi displacementing?

Semi displacement hulls were built as a compromise between displacement and planning hull. It is said that the S.D. hull is quicker than displacement and slower than planning, but gives a more comfortanle ride than a planning hull particularly in choppy or rough water, when the planning hull might be forced off the plane and slow down anyway
 
Re: Re Planing semi D

building a hull with [ QUOTE ]
semi-displacement characteristics.

[/ QUOTE ] just about sums it up..........ie a semi displacement hull doesn't actually exist any more than a 'slightly wet dry window'
 
Re: Re Planing semi D

Nope it's a planing boat. It either planes a lot or it planes a little but it still planes
 
Re: Re Planing semi D

nope - that's a planing boat with semi displacement charteristics...........

little less flat

finer entry

bit of a keel

etc
etc

once upon a time the only hull design for 'planing' cruisers had concave sections - very efficient for getting the thing up and running so worked well on low ptw engines etc - unfortunately had a few negatives too.............

we now live (generally) in a world of accepted and understood compromises - well we did when there were only shafts, then ODs drove tunnel developement and now Zeus and IPS will drive yet another set of developements (fortunately CAD should enable this phase to be pretty quick!)
 
Re: Re Planing semi D

never mind the semi planing bit. 19 knots down the river. Speed limit I think 6 knots. oh dear!!!!!!!!!!!
 
Looks like the boat planing to me alec. Most boats doing around 20 knots are going to squat a bit, and tend to be flatter at greater speeds, as they are riding 'higher up' in the water. Dont matter whether or not it is planing or semi-diplacement, they still get up and go.

The pattern produced by the wash looks similar to what my boat produces looking at a picture of it going full blast (18-19 knots), obviously in the days when it worked! /forums/images/graemlins/grin.gif

I dont know what shape you hull is underwater, but you've seen mine out at the yard, and i would call it a planing hull, with the dee vee shape, not far distant from a speedboat really.
 
Duncan has forced me to revisit this thread to conceed and agree the Laguna is capable of being on the plane.
It is unfortunate that I am in an argumentertive mood today haydn and must protest most strongly and demand everyone agrees the Lagona is an exceptional sea boat and shouldnt slam (as long as kept at SD speeds ie under 30knts). /forums/images/graemlins/grin.gif /forums/images/graemlins/laugh.gif
 
Re: Re Planing semi D

Definitely not in the speed limit, they are taken between Kingsnorth and Folly point, so there.
Look you can see Folly Point on the right..dear dear me.

planing_or_not.jpg



As regards slamming, its got the deepest vee I've ever seen and doesn't!
Thanks for all the replies, its been interesting!
Right so its a semi planing displacement boat..............
 
Re: Re Planing semi D

Mrs Oldgit is at this very moment composing stiff 500 page letter pointing out serious danger of spilt drinks and various other hazards involved with speeding large semi displacement craft being helmed by Rottweiler owning yobbos hailing from the sink estate marinas on the upper reaches of river. /forums/images/graemlins/grin.gif
 
Re: Re Planing semi D

I used to have a doberman! not quite a rottweiler /forums/images/graemlins/grin.gif

I dont spped though, cause my boat dont ever work, the the little freeman at best does six knots (displacementing /forums/images/graemlins/grin.gif)
 
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