Location: New Zealand That allright Will, we are all here to try an uncover an obvious myth in the planing of concave hulls! As you stated earlier John Haines may have a few things up his sleave that we do not know about - hence the patent on the hull, and my reasonsing for testing the shape without any of his 'special features such as the ski plank or spray rails. But, the results did showearlier planing, yet determing of this planing was not as obvious for the concave as the constant.
Better and larger scaled models would provide with some more substantial results - maybe for another project - but Im glad this topic has taken alot of ineterest.
Guillermo: The draft of both the models was the same which does decrease the volume of the concave, however we ballasted them both out so that they were the same overall weight - but the displaced volume would still be less. Location: Australia James, your observations would tend to back up my theory about the pressure distribution. So if you made the boats weigh the same, then they displaced the same amount of water (at rest: once hydrodynamic forces enter the equation it becomes a whole lot more complicated). Location: Oriental, NC I don't think you can accurately evaluate the trim of models while towing from the stem. Location: Oriental, NC I think I will add a bit of my personal experience with testing and the result in the finished full scale boat. Location: New Zealand Yes Will I think proper tests would prove better results, I havent actually investigated convexed hulls at all. Anyway, of course you are right, a 1000kg boat will displaced 1000kg of water when static, I was trying refer to the changes in displacement during the transition to the dynamic stage for the concave and the constant - if I wrote or implied something i apologise, I think it was late night after a long day! Location: Holland (The Hague) convex versus concave sections I wouldn't go for convex bottom sections in the aft. Interestingly, the flat sections required less power to go at equal speed than the concave sections. And yes I 100% agree with you that particular speed at which planing begins isnt of huge importance but the ability to stay on the plane at lower speeds would be as this is where yoiu do the majority of your travelling, at planing- as this would save you on fuel consumption based on RPM etc. I am having trouble uploading my Excel file so if you would like a copy I can email it to you or anyone else interested. If the water flow were truly longitudinal, I would think the sum of all vertical components of lift would be equal for both models. As for low-budget tanktesting, how about a bicycle with digital speedometer, a long fishing rod and a channel with cycle lane next to it (on a windless day)? You would tow one model at a time from the fishing rod which is attached perpendicular to the bicycle. You could attach the fishing rod to a rigid pole at the bases and from the deflection of the fishing rod, you should be able to deduce the force acting on it. My test rig used a postal scale with a lever pressing against the input arm as the drag measuring element. If the hull is towed fast, the transverse component of flow will not only be proportionately less but should be less in absolute terms since the boat is higher in the water and your round hull will present a proportionately flatter section to the flow. I have since significantly advanced the research into concave planing hulls, with testing conducted at the Australian Maritime College tow tank.
Experimental dynamic force for the concave, from experiment, was greater than a Savitsky modelled and equivalently loaded constant deadrise hull of 32.5deg. Resistance was high, however formulation and conclusions have determined that the logitudinal component to spray or bow wave was significantly larger. Secondly, the example with the spoon actually demonstrates the opposite of what majority is saying. The same happens to the boat except that the force is pushing the boat from both sides and the boat goes up as a result.
The only problem with the concave shape is the resistance resulting from larger wetted area.But, between the two shapes, I'd always go for concave shape for smoother, more comfortable ride and for better steering. The choice really depends on what do you want from the hull.The smooth ride, or to save a few litres of fuel. When the concave shape enteres a wave, it does so smoothly at first but, as the entry progresses, the buoyancy increases nonlinearly and the hull will slam. When a convex transverse section enters a wave, buoyancy also increases but the rate of increase decreases with depth of entry because of the convex shape. What appears to be either convexity or concavity to the eye may not be so, depending on the angle at which the hull is viewed. The problem of a boat moving through or on water is more complex than the conclusion drawn from watching what happens to a spoon under a faucet. When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Originally Posted by rxcomposite I have tried to draw all the all the principles posted on this thread to help me visualize the physics of it all. That is, if we want to keep a definition of planing based on the contribution of hydrodynamic lift to the overall lift acting on wetted area of the hull. Tom's Bluejacket 24 has an LDR of around 6.5, and the Bluejacket 28 is around 7, so you can clearly see why it transitions in such a smooth way from displacement to planing.

Interesting that he starts up using Froude number and referencing Savitsky, then says that Froude number isn't sufficient, and winds up the a general statement about hydrodynamic pressures compared to buoyancy. It is probably true that LDR is not a universally applicable tool, and you have given us a good example of it's limits.
For the rest, the fact that the term planing is not clearly defined in the ITTC dictionary either, as you have noted, is probably yet another proof of how problematic it's formal definition actually is. There are, of course, many degrees of planing, ranging from the stage where the water ceases to close in behind the stern until some feet astern to the stage where almost nothing of the boat is in the water as it streaks over the surface. Planing can perhaps be defined as that stage at which dynamic forces do the motion of the hull though the water begin to make their influence felt. Originally Posted by daiquiri seems that you have kept the wetted surface length constant, which is not really the case.
Cheers For the prismatic hull, I did not include the root spray line and used only the intersection of the waterline to keep the presentation simple. What is easily noticeable here is that the hull with deadrise angle narrows down during lift resulting in a high length to beam ratio leading to a great reduction of Clo due to loss of stagnation pressure in the leading edge. LR has a definition of planing, which to me is inadequate, hence, I am following this thread. Location: Cocoa Beach, Florida Sail Rocket Interesting point, Gonzo, well proven by the fastest sailboat on the planet. Location: auckland nz Gonzo and Doug, your interjection of reality (re VSR) may NOT be want the punters are wanting to pontificate upon here.
Location: Italy (Garda Lake) and Croatia (Istria) What answers do you guys expect?
As for Doug's pic, I did not follow the SR discussion, so don't know all the stuff involved, but the pic looks like it was taken when the forward planing surface was momentarily out of water between two wave crests.
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The FR-32J specifications were developed by the Bowers (DE) Fire Company to improve firefighting and rescue capability on the Delaware River in the area of Bowers Beach and surrounding waters. 2015 Skeeter SX 240 bay boat for sale located in Merritt Island, Florida powered by a Yamaha 300 Four Stroke outboard with 370 low hours and stainless steel prop.
Skeeter fiberglass boats have been around since the late 1940s making them one of the oldest boat builders to date. When you buy a Skeeter boat you can rest assured you are getting one of the best-engineered boats on the water. Also bear in mind that we that the planing for each hull was determined visually and there was absolutely no more than a second in it - given the size of the models as well as the accuracy of the models, they were built pretty quickly and the concave did not have a 100% accurate shape along the longitudinal buttock lines. The concave planed within 0.5-1second of the constant 9 of the times out 12, the other 3 about the same time.
The constant tended to trim alot more to get over the 'hump' and then settle down and move with what appeared greater force aft.
A tank test with underhull shots may be the only way to find out, however our budget of very little didnt allow us to fly to Tasmania and use their tank in Launceston. Im not sure of the volumetric differences in the Signatures models compared to regular vees though. A vessel will ALWAYS immerse to the point where it displaces a volume of water equal to its own weight.
Or put it another way, if the volume of the bottom of your concave boat was less than the straight one, then it would sink further. I did notice the strings on the chines as well, I might incorporate that into my next tests whenever those will be.
Would your basis on the sucking down be due to the increased transom area exposed compoared to the concaved area at all or along the section of the hull in contact with the water?
If you let the round part of the spoon touch the flow, it will immediately get sucked-in entirely.
We just did a CFD for a fast round bilge hull and the streamlines were almost perfectly aligned with the buttocks.
I would like to comment from my experience with ships, which should be applicable to smaller boats too.
The water is travelling in the same direction, passing the hull horizontaly, just as the water from the tape is passing the spoon. A high LDR hull may be narrow and deep and not have much bottom area, or it may be wide and shallow and have considerable bottom area, or it may be in between.
However, in the case of the previously mentioned graphs, we also have a family of hull forms (series 62, if I recall correctly) which those graphs are related to.
With regard to planing he explains: It is when the speed becomes sufficient to drive the boat towards the surface that the borrom form of the hull acts as aplane in some measure. The hull in tunnels' pic appears to be sustained by the aerodynamic lift and by the prop forces and moments only. We can talk about planing if the hull is in water, otherwise it is either flying or is being sustained by other external forces and moments.

The 32- x 10-boat boat provides more 3,000 gallons per minute (gpm) through a combination of the 2,000-gpm roof monitor, 1,500-gpm foredeck monitor, and two aft four-inch outlets. In addition to the oversized sliding door aft, the house features two side sliding doors for quick access to the forward deck areas. Paul (MN) Fire Department to suit the departmenta€™s protection mission on the Mississippi River. With this boat being the larger style bay boat but lighter than a larger center console of its size you’ll find she is easy to trailer to wherever you’re next fishing adventure awaits you. Our marine experts will help ensure your next purchase or sale is a trouble free and great experience. 2002 Correct Craft Super Air Nautique 210, a perfect entry level wakeboard boat for any family! I wouldn't care too much if a boat is planing or not at x knots, what I would care about is how much throttle (fuel, emissions, noise etc.) you have to give it to go at a certain speed. The concave hull would provide some extra lift in the aftship from the transverse flow component much in the same way as a flat section + reversed chine does. By conducting a full power and resistance analysis, I will be able to find out any advantages. They slam and rock a lot moe than concave shapes, skim the surface with the full area of the hull and tend to fly out of the water at higher speeds, slamming even harder when landing back on surface. If anything, as Guillermo had said, the water will create upwards (vertical) force and that is why the boat goes up into planing earlier. The shape of the parent hull form, together with the relative resistance data given by the said graphs, gives us the information we need to start making some conclusions.
That means that the only parts in the water were the hydrofoil(holding the thing down) and the forward rudder!
No planing there because it is not touching the water, so in the moment the pic was taken it is out of the scope of this discussion. Monitors and valves are electrically controlled from the safety of the interior fire control station. For the FR-32J hull the fire department requested a 19-degree aft bottom deadrise and shifted the pilothouse aft to counter the famous choppy waters of Delaware Bay. Machinery outfitting is nearly identical to the FR-32J though there are differences in the electronics and firefighting equipment. We pay upfront for a report on every vessel possible, and we provide this peace of mind to our buyers at no charge and with no commitment. If there is low pressure point inside the cavity, producing a suction force, as Will eluded to earlier in the thread, then this may in turn allow water to enter underneath the hull from the sides and around the stagnation line that was not previously there. There is no way that they'll re-entry isoftly nto the water due to their fairly flat and exposed underwater shape.
Namely, seems that you have kept the wetted surface length constant, which is not really the case. During planing, the weight of the vessel is mainly supported by hydrodynamic pressure loads, with buoyancy having less importance.
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Let us not forget that a small boat is built exclusively for transport of people and that the comfort is one of primary concerns fro that purpose. As the speed goes up, the wetted area will also vary because the mean wetted length (Lambda, the mid-value between the chine and keel wetted lengths)) will get smaller, unless the hull is shaped in some specific way to prevent is.
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Navigation, rescue, and recovery include thermal imaging, AIS, digital high-definition color radar, and man overboard monitoringa€”all of which are Raymarine components. Boat comes with a South Florida Dual axle trailer, take your boating to any water you like, do not be trap in one location. We already know that the resistance increase due to the wetted area - and assuming the results I got are correct, then the only way to counter or overcome this extra resistance would have to be have more water underneath the hull. On the protected waters of the upper Mississippi this forward work area will be a valuable attribute for facilitating rescue and firefighting operations from the forward section of the boat.
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