Displacement or/and Full Displacement

[Nomad Willy]

Many boats on this forum that are called or considered FD don’t measure up to that description by normal methods. The boats that aren’t really FD should IMO be called simply “displacement” boats. Why did the expression “Full Displacement” come to pass? The reason must have been similar to my thinking here. From a classification standpoint what’s the difference between an IG 36 and the big Hatt except size? Little I’m say’in. So this fourth classification may make classification of hulls easier. What are some thoughts?

Planing
Semi-planing
Displacement
Full Displacement

Too many of these on the fence designs exist. Haterass .. the typical big Hatt boats of about 65’ we usta call houseboats. Very hard to classify by most normal methods. From a hull shape standpoint they arn’t FD and the are by hull shape actually much like a planing hull. A SD at least. A lot like the Chris-Craft of the early 50’s. Yet I think they are called FD by most all owners that would be offended if I called them SD. But I could be convinced to call them “Displacement” boats. They are (as designed) and powered, not capable of more than a tad over calculated hull speed. But I really don’t know much about the boat. Aft pics would help.

Only supportable classification would put them in the underpowered SD classification.
But the option of calling them just displacement boats has merrit. It’s not fully supportable from a hull shape based classification standpoint ... as I have always insisted upon ... but it may be better than calling them clearly what they are not.

I only mentioned the big Hatt’s but there are many others. Lots or most of the DeFevers are similar.
If I see another post to this end I’ll start another thread. OK I did anyway.

 

[caltexflanc]

See my last post on the original thread.

 

[Arc]

My understanding of FD is a boat that can only travel through the water while displacing it’s own weight equal to the water it has displaced. Since planing emplies lift I see little difference between semi and full planing. To me you are either displacement of planing. Semi means you are not doing it very well.

 

[gotfw]

I doubt anyone would call a 65 foot Hatteras a houseboat.

 

[Nomad Willy]

Arc,
I view “semi’ as meaning partially.
So a boat partially planing like a GB32 running 11 knots is riding up on it’s bow wave to some degree. Not out on top but partially planing. Semi-planing.

But if I’m not wrong we (on TF) don’t use that expression. But I don’t see every word. The thread is directed at FD and SD or the gap there-in. But of course there is a “no mans land” between semi-displacement and planing too. But there I see the gap much more clear and far less no man’s land.

 

[Nomad Willy]

I doubt anyone would call a 65 foot Hatteras a houseboat.

That type of boat usta be called a houseboat. You’re thinking of travel trailer size houseboats most popular in the 60’s and 70’s.
Look in the back of yachting/boating mags and find 65’ yachts w one constant level main deck from stem to transom w one cabin/house on top of the maindeck. It will be refered to as a houseboat.
I probably shouldn’t have used that word as there are some young people on here that don’t know what a yacht sized houseboat is.
I’ll see if my ed window isstill open.
Thanks

I did and only my last post is still editable.
Sorry

 

[psneeld]

Never called a houseboat in my neck of the woods in 60 years of boating.

 

[FF]

"I doubt anyone would call a 65 foot Hatteras a houseboat."


Its what the proper term was for those Trumphy's that are still fantastic eye candy.

 

[Fish53]

My understanding of FD is a boat that can only travel through the water while displacing it’s own weight equal to the water it has displaced. Since planing emplies lift I see little difference between semi and full planing. To me you are either displacement of planing. Semi means you are not doing it very well.

That about sums it up, but it certainly won't be the last word.