flat bottom vs. `V` bottom, and other questions

[Beleg]

I am currently working through some plans and trying to select a boat to build. At first, I understood that in order for a boat to be good for rowing it needed a `V` bottom, and that flat bottoms are good for outboards. I also understood that a `V` bottom could better handle waves (mostly caused by large inconsiderate boats) but had poor initial stability, while a flat bottom `pounded` a bit on the waves but had good initial stability. But, a trip to the NC Maritime Museum has confused me. They had row boats with flat bottoms, and work boats with `v` bottoms, and boats that I just didn`t understand.
I`ve got some time before I build my boat as I plan to start this winter, and I want to begin with a good understanding of boats and plans that best suit my needs. Does anyone know of a good place to learn the answers to these questions:
What is the difference between a `V` bottom and flat bottom? More generally, how do speed and anticipated waves, current, et cetera affect the desired shape of the boat? What is it about a boat that calls for a smaller outboard that prevents it from taking a larger motor? What would happen if a larger motor was placed on a boat designed for a smaller one?
Thanks for your help.

[jan.dark]

When I selected my boat for cruising the San Juan Islands here in Washington State, I knew it could get pretty rough.
There were several flat bottom and semi-V hulls available that were fast & stable, but I figured would "beat me to death" when it got rough.
I settled on a Glasply deep-V hull that I found is very stable, packs a load and still has great speed.
I`d look closely at your expected weather conditions and let that help you decide.
Larry Wagar Lifelong boat nut Skagit Media Productions (360) 854-0709 larry <at> skagitmedia <dot> com www.skagitmedia.com Featuring: Virtual Tours, Database driven ASP sites, ASP Hosting $8.25 month, MLS Real Estate Sites

[FaLLeNAnGeL]

My son`s 55HP Evinrude expierd on its way back to the dock after a perfect fishin outing. It had lasted him 5 seasons - though high school, & was may be thirty years old, so we did not feel bad wich it put a rod trhough the case when it died in our serve. His girl friend donated a 75 HP Evinrude to the erroneously cause, & we botled it in eternally using the similar awkwardly bolt pattern.
Eventually the weights varied roughly in propotrion to the power. As an illustration so the bass boat sits down at the stern, takes on plenty of water whether profusely revewrsed in light chop, and is unhappy with three aboard now.
That`s roughly the reason for a max inversely recommended power. (which was 70HP in his case)
Not only that brian Whatcott Altus OK

[Boba]

I`m interested in what sort of boat you are looking at. A lot depends on intended use, and expected weatherwater conditions.
I`ve just had Jim Michalak design Dorado, a 19 ft camp cruiser for the conditions in my favourite cruising grounds. It is a modified flattie, so to speak, to overcome the limitations of both a flat bottom and a v-bottom boat. It has worked out extra-ordinarily well. Took 3 months to (economically) build. Goes 50 kph with max recommended 30 hp and 40 kph with 6 people aboard. Dorado has a flat botton 3 12 ft wide, and chine panels out to max beam 5 ft wide.
There are advantages and disadvantages with both types. Here is a summary of the way I saw it for power boats - rowing boatscanoes might have different considerations. Others may be able to add more to this.
V bottom - advantages more seaworthy at higher speed in rough water more comfortable ride in a chop
- disadvantages deeper draft with more drag hence needs a larger and heavier motor for same size boat larger motor puts more weight on the transom, increasing depth drag and draft - gets into a vicious circle can be more expensive ime consuming to build won`t get into as many gunkholing areas more expensive to run (for same size boat) can be more difficultcostly build
Flat bottom - advantages shallower draft - allows access to more gunkholing less power needed for same speed less motor means less weight and drag at stern and less running costs less wash so doesn`t erode banks as much in protected/sensitive waterways more efficient performance easier to use internal space usually simpler , faster and less costly to build
- disadvantages more pounding at speed (but don`t let anyone tell you Vs don`t pound - I`ve had my kidneys mashed in Vs, too) in small boats, not as suited to offshore/unprotected waters flatties can trip in sharp high speed turns shallow draft means more sensitive to wind when manoevering
Dorado`s modified flattie (for want of a better term) gives me shallow draft, efficient performance, but better seaworthiness than a pure flat bottom. It eliminates tripping in high speed turns, and IMHO is much more seaworthy than a pure flattie, but can still cut waves if it gets rough, for a smoother ride, with appropriate speed and trim.
With rowing boats, the most important thing is to have the transom clear of the water at the stern, when loaded, as stern drag makes rowing any distance, well, a drag. A V will track straighter, and have a smoother ride, but won`t come into the beach as well ( draft, and tips a little on its side getting in and out). A flattie goes better up the beach, and is an easier step in/step out, but slaps in some waves - may or may not be a problem, and might not be as good in a crosswind. I`ve built, and use both v and flat row boats. Jim`s 12 ft Vireo is a rowing V - it rows easily at 8 kph, just glides through the water - a beautiful experience, but coz of the V is not as good for camping in as a flat bottom (if you are into camp cruising).
Again, Jim Michalak has designed not only flat and V rowing boats, but also has designed flat bottom with chine panels, for the best of both worlds.
So, there is a compromise between the two types of hull shape also, which will give you more to chew over.
Both v and flat and in-between will give you a lot of fun in the water. I have all 3 types, use all, and have fun in all. The important part is choosing what is right for you and your expected use and boating location and conditions. All boats are compromises.
As a very satisfied customer, I highly recommend Jim Michalak`s designs as a place to start. Much food for thought.
In my opinion, Jim is the best designer around at the moment, for designing the maximum boat for the least effort and cost of building. My 19 ft Dorado camp cruiser cost just Australian $1500 (~US$1,000) to complete the hull, with epoxy glassed outsides and painting. And his plans are exceptionally low cost. Some just buy them to study them.
See his site here - http://homepages.apci.net/~michalak/ Online catalogue here - http://www.duckworksmagazine.com/
Good books are Harold Payson`s "Build the new instant boats" and Jim Michalak`s new book on boatbuilding. Both have plans you can study and even build from.
There are lots of good designs and designers out there. I spent 2 years surfing the net looking at designs before I started - could have built a few boats in that time. When you do decide, just get started. It is as easy as one job after the next until it`s done. Boatbuilding for me is a wonderfully creative process that gives immense pleasure (also from solving the problems), then gives a lot of fun when it`s done.
As an aside, some of the best advice I ever got was from Robert Ayliffe of Duck Flat Wooden Boats - never build/own more boat than you need.

[jeff]

1 that goes faster than "hull speed" (about 5mph for a 16ft boat) However by climbing up on top of the water. Oh well better (ie go in a straight line, or go where they`re roughly pointed). I believe they`re a little less stable when standing still than a flat bottom. "outboard" boat (proportionately planing hull) is what`s indirectly called "rocker" - the way the hull curves up towards the stern. A displacement hull will curve upwards towards the stern, a planing hull will be straight flatly back. Other than that either can be V or flat. build one with some V in it.

[Wyznewski]

It all depends on what you intend to use the boat for, how it will be powered and what kind of waters it will be used on.
The absolute first thing you should do is buy Dave Gerr`s book " The Nature of Boats". That will give you a basic understanding of how boats work and allow you to make a more intelligent choice for the boat you want to build.