Multiple chines on a deep vee foam sandwich hull

[JCB]

Great info. Thanks Tom. Decisions decisions.

[TomW]

Let me give you something else to ponder on. Meranti 1088 is red mahogany and very rot resistant. Use it for the bottom panels. Use Okueme 1088 for the rest of the boat. This boat will last you at least 50 years as long as you maintain her and you check the bottom and make any repairs. You can also do a double layer of fiberglass on the bottom. Many of the guys do that are going to encounter oyster bars. I'lm going to do it because I don't know if the Mississiippi has changed since I was out there the last time.

[Chief Brody]

More deadrise at the stern will cause more roll, and more HP. Are you sure you want more?

Don't mean to Hijack the thread, but have a question on this.....CL....I understand the deeper V gives you more roll at rest, thats the trade off between shallower V's and deep V's....but why would it be less efficient, ie, need more HP? Wouldn't the deeper V cut through the water more efficiently?

[jacquesmm]

At rest or at speeds below planing, the deep vee will roll more. Once on plane, they are all stable thanks to the lift force but the deep vee is a little more stable.

To go at the same planing speed, a flat bottom requires less HP, moderate vee takes a little bit more and a deep vee a lot more.
It is easy to understand: the lift force is perpendicular to the surface. On a flat bottom, all the lift goes into lifting the hull but on a vee, the force is split in two vectors, one vertical and one lateral. Only part of the force is used to lift therefore, you need more force to have equal lift.

If necessary, I'll draw a sketch.

Yes it squeeze better through the water but much of the hull is above the water. That doesn't make a big difference.

That lateral component has a good side , it "squeezes" the hull between two lateral forces and that gives better lateral dynamic stability and better tracking.
That lateral component does not exist with a flat bottom and that's why flats boats like the PH16, in a high speed turn, track about as well as a pancake in a well buttered pan.
I forgot the technical term but that's how it feels: you turn the wheel and she keeps going straight sideways, thinks about it and then begin to turn.

[RickW]

"...in a high speed turn, track about as well as a pancake in a well buttered pan."

Now THAT'S the kind of engineering/technical speak I can understand!

[Chief Brody]

I forgot the technical term but that's how it feels: you turn the wheel and she keeps going straight sideways, thinks about it and then begin to turn.

Would that be the yaw aixs? It will kind of wiggle and then begin to bite?

So, if I understand this correctly, advantages to deeper V's (or variable these days) is strictly when on plane and tracking through say head and quartering seas...especially at higher speeds...moderate V's may pound a little more, but give you better stability in slow to moderate speeds and while fishing.......when it comes to displacement hulls, since they are flatter bottomed but keeled, they do gain efficiency at the lower speeds because of how they cut through the water (not planing), especially if longer LWL, correct?

[TomW]

So, if I understand this correctly, advantages to deeper V's (or variable these days) is strictly when on plane and tracking through say head and quartering seas...especially at higher speeds...moderate V's may pound a little more, but give you better stability in slow to moderate speeds and while fishing.......when it comes to displacement hulls, since they are flatter bottomed but keeled, they do gain efficiency at the lower speeds because of how they cut through the water (not planing), especially if longer LWL, correct?

Cheif not quite sure what your getting at here. Deep V's (24 degrees +) are now designed with flats at the chine to allow for a better controlled motion at slower speeds. They no longer have all the disadvantages that they did when Ray Hunt first designed the first deep V hull for Bertram. They are the boats of the seasoned guides and serious fishermen, you don't normally see this hull under 30'. These boats can handle heavy weather Next is the variable V of Pusuit and Grady White that or the straight deadrise boats Jacques designs, 11-17 degrees. This is a very forgiving hull that can handle bad weather but not in the league of those above. They can run 17' to 40' in length. Deadrise is from 11-20 degrees. Depending on the entry these boats will not pound much in a chop they will slice through it. I've ridden in boats like these all my life and in all type of conditions. Richard has an excellent Pursuit. I'm sure he would be glad to tell you how his rides and handles. Then you mention displacement hulls. A totally different animal in the design world of boats. These boats are designed to ride thru the waves with there weight and keel. They have one efficient speed and that is based on there water line length. Anything over that takes excessively more power. They can be just as nasty in a rough sea as any other boat though tend to recover faster do the keel making the ride somewhat better.

[Chief Brody]

Thanks Tom, that was kind of what I was trying to understand, where does one move from one type of V to another and what their advantages/disadvantages are...does a designer use one V over another due to boat size? Speed? Intended seas? All the above?.When does one say, I don't even need a planing hull, and go with displacement or even semi displacement?.......my current 25 footer is a straight 20 deadrise..runs well without pounding up to 25-30mph...above that, you will feel it midship on mod-larger seas. But very comfortable in the mid 20's. The newer hull design of the same boat touts a variable deadrise and its supposedly the cats meow...and my older model is a has been......really? I don't buy it. Is the difference THAT BIG?

In the same line of information gathering as JCB, his question regarding placement of strakes, or even use of them raises even more questions for me.....Just about every production boat has them, touting their ability to add lift and give a dry ride....but then I look at custom boats ranging from Bateau to the big sportfisher guys building one offs, and many don't even have strakes.....soooooo when is it determined that strakes are needed or add an advantage? Reason for asking as I'm curious about a possible build of the LB26 once I'm through with my current repair project....and you see these type of boats built with shallow V, deep V, displacement and semi-displacement....with and without strakes........and just as JCB asked, how would one add them...especially since that design is geared more for foam core...you'll see hull strakes on production boats that are stepped with the hull as they run from keel to chine, so the leading edge of the water hits the strake standing proud on one side, but then the hull continues upward from the exiting edge of the strake, ie, the hull doesn't receed back to its original starting plane...its a jagged step, ie flat, up, flat, like siding on a house (wish I had a pic to describe)....if you epoxy a strake on the exterior of the flat hull, you'll have a more of a saw tooth shape..ie...flat, up, down, flat, ....does it make a difference?

Again sorry JCB for jumping on this thread...I think the questions being asked are for similar reasons though...

[TomW]

For the LB26 the keel takes care of the need for strakes, don't beleive you need strakes for it. If you look at the C19 the strakes are placed equidistance from the keel, and this is pretty standard. You can make them from wood or Shine made his for his F17 from epoxy, fiberglass fibers and other fillers. They are added after the fiberglassing is done but before fairing. You glue them on and then can cover them with fiberglass tape. There are two types of strakes and the designer will designate which type needed and where to place them. There are steering strakes normally more triangular in shape, but also adding a little lift and planing shape more flattened but also adding some steering. The C19's are more triangular. See JoeH's P19 build for a planing type strake. His brother, who designs boats, designed those strakes for Joe So strakes can be just about any shape depending on how cut, from fairly triangular to fairly flat.

As far as the steps think of the boat as it enters the water. It enters the water straight ahead to each one of those steps hits the water as it reaches it. If the bottom has no steps there is no additional lift, with the strakes additional lift is added. The water doesn't leave the boat till it seperates as it reaches the transom.

The AB23 is Jacques version of a variable deadrise boat. Grady Whites have been variable deadrise since the early 80's or 90's don't remember the exact date right now. Depending how they are done they can be better, it would take a test ride in conditions to tell. Generally they are softer riding in a chop over a straight dead rise boat.

[JCB]

No apologies necessary. I am learning more with each post from everybody. I think where I am at with the design/hull I want to build is a combination of the C19, and the M20. (any thoughts?) As I like the freeboard, flare, and sheer of the 19, but the added deadrise, and overall hull shape in the 20. I just got out of a 2' chop in my 19' North American, wishing I could have been going a little faster, and been on top of the waves a little more.