When at rest, a surfers weight is borne entirely by the buoyant force (also depending on how much beer you drank the night before). At low speeds every hull acts as a displacement hull, meaning that the buoyant force is mainly responsible for supporting the surfer.
A fluid flowing (water) past the surface of a body (surfer + surfboard) exerts surface force on it. In contrast, the buoyant force decreases as the hull lifts out of the water decreasing the displaced volume.
This is the reason that surfboards with lots of rocker need more speed and their no rocker cousins scream across the water. The major difference between a planing surfboard hull and a displacement hull is the way in which the surfboard travels through the water.
At high speeds a displacement hull’s tail will sink down lower and lower as a result of the “hole” created in the water as the surfboard moves forward. A planing hull, on the other hand, will have a flat or concave bottom contour and plane up on top of the water.
Displacement hulls push through the water as they have no hydrodynamic lift, or the surfboard does not rise out of the water as speed increases. The hull design (shape) does not limit the maximum attainable speed but does affect the power required for it to get on plane (on top of the water). Semi-displacement or semi-planing hulls have features of both planing and displacement hulls. There is not one hull design characteristic that differentiates semi-displacement from semi-planing hull.
The greater the hydrodynamic lift and higher the hull design speed the more likely it will be referred to as a semi-planing hull.
I came across this blog post by Steven Mast of Mast Surfboards and it is an excellent discussion of the topic. Old, soft edged boards are the same, as are any true displacement hulls being produced today.
Now I’m sure I’ll get some flak for this, but displacement hulls, by their very nature, are not as fast as planing hulls (editors note: . Another thing I’ll take flak for, and I’m saying it anyway, Greg Liddle did not invent the displacement hull surfboard. All displacement hulls, although arguably not “modified transitional displacement hulls”, whatever that means. I (even after researching and writing it) have to reread it sometimes to understand it too.
I am totally with you on this, my experience is that a board reacts differently in a turn vs. Putting an edge on a tail does not automatically turn the board into a PH—totally agree. All surfboards (regardless of the intentions, theories, or fantasies of their designers) plane on the wave face. Most simmons hulls I see are single concave, but I spoke to a guy in the water who was riding one with a v hull.
Location: Twisp, WA USA minimalist cruising, sailing, rowing design I'm in process of designing my ideal boat (current vision).
The cabin looks like it will interfere with rowing unless you plan on putting the oarlocks and rowing position very far aft or the companionway is huge enough that you partly enter the cabin at the end of the pull stroke.
I think you're going to find it's quite a challenge to keep water from entering the storage in the cockpit floor. Something you should seriously think about is to not go with that conventional daggerboard. RE dagger board in Cabin: At the very least, raising the dagger board would get water in the cabin - not a great situation.
RE cockpit floor storage leakage: After thinking about your comment, I'm currently thinking to access this space from inside the cabin and from the deck hatch behind the cockpit.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Location: Marshfield massachusetts usa reading I am reading Pete Cullers' book on wooden boats and rowing. Location: petaluma Just the picture for a rainy day Yes I really liked those gigs. Location: Portland, ME Drake in the water Did some rowing the other day after playing with Drake's keel and the results seemed OK. Location: Marshfield massachusetts usa drake Drake looks like you hit the nail on the head. Location: Marshfield massachusetts usa good material Clint, your comment about bedding your keel prompted me to offer a suggestion.
Location: FL, USA I took a break from work today and read the content on this thread that I had missed. Location: Marshfield massachusetts usa panic time Well friends, it's panic time. Location: Marshfield massachusetts usa web sites Clint, I'm aware of two sites where you will find info on open water rowing.


I'm trying to design an easy to build rowing boat for open water , and would like comments for the design to date. Location: AUSTRALIA It looks a pretty reasonable drawing for one rower, but explain why it is finer in the stern sections than the bow? Location: Cape Town Hi Jelfisher, thanks I know of free ship , but I'm not an engineer or Boat designer, I'm just drawing a shape that looks kinda pleasing to me. Frosh, This is not going to be a formula 1 version , but is essentialy a pleasure and exercise row boat. Regarding the runoff ,all the rowing boat books suggest that the entry should be fine and the run off even finer, The st Lawrenec river Skif is a good example of this ,, as are most of the surf skis in my town.Remeber that most of the double enders of old were working boats , and often were used in either direction. As I've mentioned I'm not an expert , but am just copying what I've read , Kinda Monkey see Monkey do approach. Yeah I guess the sliding seat will cost and arm and a leg , but maybe I can get away with something made locally in Cape Town South africa. Location: Southern England The idea of the fine bow being to reduce wave drag, and the fine run-out to reduce friction drag. You should take into account, of course, that the big problem in an open rowing boat is waves breaking over the bow or stern. I guess that I shoul flair the topside near the bow and stern to give a nice shoae to deflect the odd wave ( not white water though).
Location: Marshfield massachusetts usa go with a stretched Gloucester Gull dory from Phil Bolger, they row well,are fast and can be rowed single or double. Location: Marshfield massachusetts usa hull form A practical reason to have bouyancy forward is to properly support the weight of the oarsman. This design does not ride high on the water like a planing hull, instead plowing through and parting the water. There are displacement hulls, planing hulls and as usually is the case, some variant of the two. The very nature of the release provided by that edge, by definition puts that board into planing mode.
As soon as they get going, the tail end of the board starts submarining and they can literally walk to the nose and go.
As soon as you put an edge at the tail, you release the water and the board begins to plane. They may “feel” faster in a section, but without the release, they are constantly dragging more than a sharp edged board would.
He refined it to an amazing degree, made it work in a short package, championing it when it was completely against the trends of the time, but have you ever seen a Weber Foil?
But i still don’t understand the general accepted theory that as soon as you put an edge on the tail it turns into a planing hull. It is certain to leak and you can't get at it so easily and the case is right in the middle of the only internal living space .
The case goes right through the boat-no leaks, out of the way, efficient, but larger turning radius and rudder must be larger and well balanced. It is sort of a dissapointment to me because I was looking for more concrete information than is in the book.
As you can see in the pictures I am at the W.L without any other weight, especially a person. Those few cold weather rows will give great thoughts for the winter and while I try to get in shape on the erg. He must have had an indominable spirit to survived and then live to the fullest extent possible.
Race conditions were: temp about 44 degrees, partly sunny and a strong breeze of about 15 mph out of the North ( I think ). However ,I take your point about size , I guess I made the mistake of trying a one size fits all approach , thanks for bringing me back to earth, I guess that there should be two boats one for single and double fixed seat as well as single sliding , and one for doble fixed and double sliding. Last time I wanted to import some oars the deleivery cost from england to CT was like buying a couple pf outbards. I'd incorporate some sort of foredeck with a coaming to deflect water sideways at the aft edge of the fore-deck. Oar placement that is too far aft creates a boat that makes it hard to keep her head into the wind. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction.
Think of an ocean liner moving through the deep ocean versus a speed boat racing around a lake.
The modern surfboard, most “hulls” included, balance these principles to achieve the desired effect or feel.
On the contrary, I think his boards are brilliant and have been a huge design influence for me. A displacement hull works more by pushing the water around it’s hull and through the rails and tail, where as a planing hull works more by channeling the water directly through the hull. Put the spoon face up (like a v-hull), and the curvature of the spoon allows it to wobble effortlessly. With spring tides giving us 12' high tides and always 15 kts of wind gusting to 20 it is sure hard to really feel the boat.


After bedding the keel strip, I'll be putting Drake in storage after all these storms pass and getting onto the next project, finally! First leg of the race, the waves were on our starboard stern quarter, second leg right into the wind and third leg was just about broadside to port. If you are thinking two rowers I believe that it will need lengthening to around 6.5 to 7 metres for a really efficient easily driven hull for the greater all up weight. A displacement hull has a theoretical hull speed, above which the water actually sucks the hull deeper into the water (I’m simplifying here). The feeling of a well balance hull is one of the great pleasures of surfing that most people fail to credit. A small amount of edge in the tail of a displacement hull will not convert the entire board, it will still act as a DH.
The picture shows straight seat top sides but we usually build extended curved sides much longer like the ones on the 10' V-bottom dinghy.
I was feeling that I had thrown my money away until I got to the part about making your own oars. Those folks need a dory, I don't think they realize how difficult it't be to load a two-man rowboat into the roof top, but definitely doable. Those long races are where great speed is not as necessary as the ability to keep up the good average speed that Drake should be capable of.
It is moderatly adhesive and retains enough flexability to work well as a bedding compound. The real bad news is that my brother is having some heart problems and may not be able to row.
I haven't done the Essex race, and that is one reason for building Nordlys: When brother Dave isn't able to row, I want to do some different races and meet some new rowers. If it is going to be one or two, then I would think it will be very difficult to incorporate sliding seat(s). Surfing one well takes a different approach, especially if you are stepping off a thruster.
If you were going for a hard back foot turn with little else board in the water than the tail only then you could call that planing, otherwise it would still feel and act like a DH majority of the time.
The cost of commercially made oars is prohibitive to me, so do it yourself is what is in order. At anything above the theoretical hull speed, the boat begins to submarine, actually being pulled deeper into the water.
The cabin occurred when he lowered the sail, tilted the mast aft in its step, and draped the sail over it, yard on one side, boom on the other. I realized last night taking her off the trailer to put in my shop for final adjustments that she is a tad heavy, but I'll need to get a scale and see how heavy. It's sunny but cold here ( 34 ) so I guess that I'll bundle up and see if I can get the oarlocks on and a thwart in place. The second thing that made the book worthwhile to me ( so far, only a quick scan through it ) are the pictures of three rowing boats he designed.
We were elated, but it all pales compared to what Joseph Blackburn did on his row for life. Modifying the skeg allowed me to take the anchor out of the stern and this made me go faster!
Culler would not favor my choice of construction which will be strip built with fiberglass or dynel set in epoxy inside and out.
Let's all hope that none of us ever gets in such a situation for, I fear, we wouldn't have the grit to do what he did. Foot stretchers are a puzzle to be worked out how ever possible to get anything at all to brace on.
One of the DuPonts stopped at our yard coming and going to the Bahamas every year, and every year we would have to fix the bottom of his Boston Whaler and drain several quarts of water out of the core. Incidentally, I found the skeg grabbed a bit too much, so I will shave off a bit and call that good.
Much as I would like to try to do a traditional construction build, it looks like more than I am capable of for a first attempt. Fore cast for Saturday is for a decent day with temps in the low 50's and gentle winds with mostly sunny conditions. Weather here has been miserable with temps in the teens AM and 20's PM continuous light snow with about 10" on the ground. There are several lakes and reservoirs close by where they live in North Carolina, and they would enjoy having the opportunity to get out on the water with their dad. No rowing there right now, but maybe a chance to go dig some steamer clams if things are right some Sunday.
Miserable weather here today, gale warnings and torrential rain with freezing rain to the North And West.




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