What is considered a deep v hull?

[gordmac]

Have a look at Sonny Levi designs, the Corsair is the business if you have the money!

 

[PowerYachtBlog]

Thinking of cruising speed behaviour
I was speaking with an American bloke the other day about CC, he had a the 390 Z stepped hull version and ended up trading for the V (no stepped version) just because of the superior comfort it gives at speed at the better behaviour at medium speeds. He did this after a month, and now he just says how spectacular the SeaVee V390 is in all respects.

 

[Portofino]

Thinking of cruising speed behaviour
I was speaking with an American bloke the other day about CC, he had a the 390 Z stepped hull version and ended up trading for the V (no stepped version) just because of the superior comfort it gives at speed at the better behaviour at medium speeds. He did this after a month, and now he just says how spectacular the SeaVee V390 is in all respects.

I always have said “ try before you buy “

Reading round the subject it all seems to depend on the details of the design .
If it was a dedicated stepped hull from scratch they seem to be ok no extra down sides .The one down side is in a chop / wave , think beam + waves seas whereby the steps air gets blocked by the waves .The pro step brigade will say alter course away from a big beam sea .Not always possible .

How ever some stepped hills are just done by inserts into a deep V plug is added in later .
This Seavee 39 has a 22.5 dead-rise btw .
With theses counterintuitively they slam more than the standard V .This is because the flat bits of the steps present a slamming surface in waves esp if the thing ( likely if running fast ) gets airborne over a crest .And noisy as the steps slap down , and a wetter ride as more spray flicks up than a std deep V .
Also if the weights far too far back the thing is not balanced then as it gets air or 1/2 out of the water it’s attitude changes , stern dips where the heavy OBs are thus present the exposed flat parts of the steps .The more steps 3 as opposed to 2 the greater the slam .Kinda undoes the deep V soft landing if you like .
Sure in calm conditions with minimal waves you would not notice .
And if the thing was really designed for speed from the drawing board / CAD to begin with , not a sort of retro job on a existing nice deep V plug .

Done right from scratch with a thought to weight distribution- fwd tanks etc they run very flat and will take air flat not change attitude to slap the steps at speed .Low angles of propulsion are paramount so surface drives sticking out give the best chance of keeping flat , the bow low in waves or semi air situations.The mega high speed stepped racing hulls are all surface drives .

You can’ t really do a shaft drive and stepped hull as the shaft angle ( best below 8 degrees anyhow ) means they tend to run bow high , far too bow high .A bug bear of mine watching all theses FB shaft drive boats look like they about to take off like airplanes.
This means the steps will continually keep actually dragging because they are at the wrong attitude under the hull = opposite effect inc drag . Aside the sterns are sinking on a lot of boats I see running .Totally unsuitable for steps that’s why you do not see them , or only in CC fast fishers and of course 100 mph racing boats + surface props as well .

Remember idea is the introduce air and reduce drag = more speed for a given Hp .

Thing about outboard CC s centre consoles , you can very simply up the Hp with a deep V which has more drag compared to its stepped sibling .