Boat hull design for rough water gear,used pontoon boats in upstate sc university,pontoon boat for sale lake lanier jobs,design your dream boat meaning - PDF Review

Published 17.02.2014 | Author : admin | Category : Wooden Skiff Plans

Originally Posted by sottorf I agree with the general sentiment that long and narrow is good for seakeeping (not exactly a new concept). Location: NW Washington State USA Here's a boat I designed in the 70s that may be of interest.
Location: The Netherlands why not extend the bottom hull so your stem angle has like an 80 degree angle with the waterline.
The boat was originally designed with a steeper stem but I thought the weak link was the low volume in the bow so in order to find out if that was going to be a problem I extended the bow during construction thinking if I did'nt have a problem w the extended bow I did'nt have a problem. In quartering following seas the forward end of the boat lacked stability but the stability of the stern kept things in control. Location: The Netherlands So, in your opinion fast hull form with an steeper stem will increase the head sea performance, but will mess up the quarter sea performance.
I am designing a planing hul form with a fairy large payload capacity, so going airborne won’t be an issue. When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. If you're in a catamaran with one or the other, is there any difference between them if the hull cuts through a wave?
Are you talking about the difference between transoms on displacement cats and power planing cats?
Location: Here and There It will be a sailing catamaran, sorry for the lack of clarity there. Location: Port Gamble, Washington, USA Theoretically, the minimum wave drag shape has a sharp stern. One good way I've found to design such a stern is to create a generic cross section shape and smoothly vary the beam-depth ratio along the length of the boat. You'll also want to read the articles by John Shuttleworth on multihull seaworhiness and topsides shaping. Speaking of the boundary layer, I have another question that's totally unrelated, but I've been wondering about for quite a while. Originally Posted by Free Pirate It will be a sailing catamaran, sorry for the lack of clarity there.
Perhaps the most important part of a small cat, say the designers I've spoken too, are the bows.
Do a Google for Formula 18s, F18s, and builders and designs like the Hobie Tiger, AHPC Capricorn (very fast) and Nacra F18 and you'll find lots of shots of succesful stern shapes. Location: Here and There Yeah, it's more like an F18 than a Hobie 16, but it will have to displace about 400 kg of crew, and over 200 kg of its own weight. Originally Posted by Skippy Speaking of the boundary layer, I have another question that's totally unrelated, but I've been wondering about for quite a while. If you look at tank test models, you'll see a row of small studs sticking out of the model just behind the bow and the leading edge of the keel. In the bowling ball example (and the infamous dimples on a golf ball), what you're dealing with is laminar separation.
The point is, boundary layer trips are a cure for a very specific disease: premature laminar separation.
So you need to know what the pressure distribution on the hull is doing, and where transition occurs. So you have transition occuring way ahead of midships, in a region with a favorable pressure distribution.
Location: Sydney Australia Hmmm, I may be wrong about that, but I'm still not sure.
The Flyers spend a lot of their time sitting around between races with the bow knuckle out of the water, unlike the drawing above. I think your observations are correct, you are not going to get the trim that you see in the pictures I posted unless the crew is sat on the front beam in the centre of the boat, as the static centre of buoyancy is around 2.5 m in front of the stern. Location: Sydney Australia Ya, I'll have to have a decent look between races this Sunday.
Having taken damage in the vulnerable part of the topsides from a Flyer's ram bow, I wouldn't be altogether happy about sharing a course with the Nils 2001 I must say. Location: Here and There Would adding 'rocker' (I don't know the correct term, is it sheer?) to the freeboard help with forward-back-rocking stability? I think the bow might get totally submerged, therefore displace more and float more, if it gets hit at the right (or wrong ) time by a wave. Shoalwater fishing boats has earned a reputation as the premier fishing boat manufacture through hard work, attention to detail and quality control. We manufacture four models of catamaran style fishing boats, from 16' to 23' Catamaran hulls.


Our Cat Hull series features include a dual shaped bow for pounding through rough seas while maintaining a nearly flat stern (from the console aft).
For serious fishing, family boating or just playing on the water, we have the boat for you. Location: Australia It was a beutifulday yesterday, and I spent it at work. Chris Ostlind Previous Member   Quote Not to be too obtuse about it all, Ike, but isn't your favorite signature quote really from the lips of one, Robert A. Location: north of pompano I built this Race Proven, goes like stink and doesnt slow down in 6's outside. Originally Posted by kach22i Do the Cat's do better than mono hulls of the same length in rough weather? Location: Michigan Thanks, I just hate getting caught out there in any sized or type of craft in rough water.
Location: London Cats dont seem to do well in the typical English sea conditions. They do seem to have short 'bursts' of speed, and then collapse - the variation is as much as 15 mph. Location: Ohio Best handling small craft in rough water: V hull, Cat, Trimaran, Pantoon, PWC? Since it's light it is on the waves and with a sail it has calmer motion, even though its a bit slow for some ppl. Location: Michigan Several people have told me RIB's (rigid inflatable boats) because of their extra buoyancy.
Location: Cornwall, England RIB's is good, anything with a big controllable engine like an outboard really!
Originally Posted by marshmat To start with: There is no small boat under 16' that will be comfortable in four-footers.
Location: Ohio In the fall at lake erie ,sailboaters go playing in rough weather to get the last hurra in .
Originally Posted by longliner45 In the fall at lake erie ,sailboaters go playing in rough weather to get the last hurra in . Location: Davis, California suggestions for a small narrow hull for rough seas I have been wanting to build a small one or two person boat that can cut rough ocean waters while still maintaining at least 20 to 25 knots.
Location: Japan You have said whether you're looking at a mono or cat hull form? Location: Davis, California open to anything that works Thanks for the reply Ad Hoc. Originally Posted by kurtjfred I have been wanting to build a small one or two person boat that can cut rough ocean waters while still maintaining at least 20 to 25 knots. Location: Davis, California I was researching historical torpedo info and was quite shocked by the speeds and distance they were acomplishing during WWII and awed by what they are doing today. On that note, does anyone know off the top of their head if the drag coefficient is the same in liquid as air?
Location: Sweden A long and narrow boat with low deadrise, very little rocker and a long sharp wavepiercing fore would do the job. I don't have a proper ocean nearby so I don't have an opinion on whether a boat is oceanworthy or not.
Hydrofoils work very well and can maintain a constant high speed, until you reach the point where the wave height is comparable to the flying height. The submerged torpedo hull idea- like a SWATH ship- has its applications, but I don't think this is one of them. I first drew a double ended 34 footer with a small outboard in a well, then I started cutting cost of the build and maximize the use of 4 x 8 sheets of particle board for the mold and 38 inch fiberglass for the construction and ended up with a 28'x4' that weighs about 1400 pounds and was meant to carry a 15 horse outboard on the transom. In order to meet the electrical requirements of a spotlight, windshield wipers, bottom machine, and a couple fans it was necessary to purchase a 25 horse for its 15 amp charge system and I was pleasantly surprised when the boat handled well at speeds up to a speed to length ratio of 4 (21 knots) although the stern was settling. Ballasted with water, rocks, gear, and people to somewhere around 2800 pounds it would still run well over 16 knots but really seemed to like 12 knots and burned about 1.2 gallons per hour ( when lighter around 1900 pounds it burned three quarters of a gallon per hour at 12 knots). Design and construction consumed one month and with power about $10,000 , it was well worth the education. As to rough water handling, this one is handicapped by the CG of the passengers being too high and the engine weight being too far aft and to high, but even so I've seen the spotlight underwater while pushing into them and ridden in the trough of a 35 knot inshore blow. I think you can accomplish your goals in a semi-displacement design but because 4 feet is not wide enough you're going to end up with a larger,higher volume boat than you're talking about in order to satisfy stability requirements. Nice work, what about powering with a inboard, this would provide lots of ballast down low and shift weight forward. Location: Davis, California Thanks commuter, have a couple of sketches from the last few months that look similar.


One of the most exciting incorporates a 10 hp Sabb with a variable pitch propeller which is presently sitting under a tarp outside.
I've spent a few years lurking around this site without posting much and during that time I've been very intrigued with Fast Fred's pursuit of improving on and modifying for cruise purposes, Atkin's rescue minor. It was while studying the similarities that I was once again struck with how much easier it is to control the relationship between the center of gravity and the center buoyancy as the vessel gets larger. I look forward to continuing this conversation and I'm sure that my prototype would have benefited from the scrutiny of the experts on this site. I'd suggest you be brave and post your preliminary drawings, the most knowledgeable are gentle and you can ignore the rest, your project will benefit. You can still deflect the spray rail in the configuration you made, but the longer hull might make for an even smoother ride. In strong head winds and seas it had a tendency to become airborne and 50 knot head wind was very dangerous.
With much respect to Tom (who seems to be writing about larger cats), I'm sure that F16s and F 18, Tornadoes and IIRC A Class cats DO have their transoms immersed at rest with crew aboard. Obviously crew position has a huge impact, so maybe we are all worrying about a situation that never happens in real life?
Although they are really designed to sail on one hull, in that situation the stern will be in the water.
Unfortunately our cat club's fleet has dwindled this year so we probably won't have any world-class Flyer As there but Nacras, Capricorn, Auscat 5 A, Tornadoes and Taipans should give me an idea.
The height of the waves varies a lot, so that the hull can not travel in a straight horizontal line without hitting some of them really hard!
A catamaran would be preferable, and then you can utilise the longer length to good effect.
I am familiar with aerodynamics but at times you are considering the compressibility of air which I believe is not a consideration in water. I've tried such a boat, and it gave a smooth fast ride with little horsepowers even in a chop because it cut through the waves instead of crushing them from above. The power needed to drive it is approximtely proportional to the weight, so the boat should be as light as possible. Erik and Matt - A couple of friends from UC Davis read your responses and think you two are dead on. The 37' x 6' that I mentioned above would incorporate Atkin's tunnel stern but I must admit that I've gotten cold feet due to the lack of widespread acceptance of that design. The advantage of GRP is that it lends itself better to mass production, but as I understand it that is not a consideration. People like the Cunninghmans had Vee or canoe sterns for years but decided that transoms were better. Sure, they are lounging between races but I regularly see Caps at that attitude and the crew isn't TOO far aft.
The lower the length displacement ratio the lower the vertical accelerations as well as better powering too.
What if you had two small cylinders skegged to a very sharp v hull of about the equivalent size of a kayak and hydrofoiled them to lift the hull clear around 5 knots +- ?
We have several power plants to work with from small 8 horse up to 30 horse diesel and gas from 5 up to 28, that can be modified and used as inboards. The boat is Safehaven marine, the same article say Ray Hunt commercial designs are very good.
Transom width can be a delicate issue on small boats IIRC, wide sterns are good at times but too much lift aft creates nosedives. I dive from a 12 foot inflatable and the ride in windy conditions is brutal trying to maintain any speed. I have been trying to think of ways to accomplish this such as hydrofoils to keep it up and over the waves or some type of very skinny and possibly heavy hull that would penetrate and go thru the waves. I had a very interesting conversation with an old navy guy in Point Arena California one day about adding water ballast to smooth out the ride and than offload it to add bouyancy while stopped or in calm conditions. I wasn't against the idea of making a hatch so to speak over a cockpit and peirce thru the waves. Although if it was a hydrofoil, the speed would diminishing thru a wave might be a problem. I have yet to look at any fluid dynamics of the drag on a cylinder below water but it can't be any worse than some of the large deep V hulls of the mid size boats.



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