Jet boat design build 2015,boat plans metal gear,used wooden boats for sale australia 2014 - Review

Published 25.02.2016 | Author : admin | Category : Diy Sailboat Plans

Location: Southern England Renato Levi Wrote three books on the subject of designing Powerboats.
Best book currently available on powerboat hydrodynamics is Hydrodynamics of High-Speed Marine Vehicles, by Odd M.
If you are working in Aluminum, go to ABS, Lloyd's, or ISO and get rules for construction of high-speed vessels. Jet boats are tricky, most major water-jet manufacturers have lots of data on what works, talk to the supplier. A phenomenon known as porpoising can occur if you are not caqrefull of what you are doing on the bottom, particurly in the 6' infront of the transom. Make the delta pad on the bottom nice and long, no-one says that the boat needs a 'keel', where the bottom sheets meet to form the vee. Look at other jet boat manufacturers and what they do, we spend many hours making sure we get it right so we can sell a safe and well performing product. As has been said the key is power to weight and planing area in both laden and light conditions. When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Originally Posted by speedboats I'm sure if you were requesting knowledge then you'd be pointed in the right direction.
Unfortunately, as on most forums, it is easy to hi-jack someones thread which then changes the focus and is of no help to the original author, some here try to maintain that focus. I don't want to open another thread, this is the one you commented on so this is the one you should be replying to but so far all I've heard is drivel! I say again I'm a novice with jet drives and I do not believe whatever you do with that jets will help.
However, should you by some miracle gets it on the plane, that boat will not be very stable directionally and will slam like no tomorrow - will not want to take her out on the rough though. At least in displacement mode you can then run the engines economically by barely ticking over to get to the calculated hull speed of 7.34 knots for 30ft waterline.
I did weld some on that extended about 14 inches across part of the transom, with allowances for reverse controls.
The anchor can stick out over the bow and mentioned appendages at the stern, but otherwise the boats are limited to 32 feet overall.
There are lots of similar jet boats in the fishery, some as wide as 17 feet, one as heavy as 45,000 pounds. All the Hamilton jet guys use 5 or 6 blade impellers, as opposed to my 4 blade, with a higher KW rating than Hamilton Jet recommend. With three thousand pounds of fish on board all jet boats are 6 to 8 knot boats, but will keep on packing up to 30,000 pounds of salmon.
Props and shafts would probably increase speed, fuel economy, and directional stability, but I need to be able to run over nets and sit on the bottom. Though I don't use all my horsepower for speed since there is very little gain past displacement speed, as Wynand pointed out, it comes in handy when pulling on the net. Actually you are argueing with a professional boatbuilder (in fact two of them), a well proven pro in Hydrodynamics, a boatyardowner, and other quite respected members with hands on experience.
We know each other for long and have proven each other right or wrong so many times, there is no need to doubt our experience. You have shown nothing but opinions and a unpolite behaviour, and YOU are hijacking this thread because you are stubbornly unwilling to accept, that no expert here has the obligation to answer your questions.
Just throwing a (wrong) opinion in and assuming one gives you private lessons to correct them is bold. Feel free to spread your opinions on every thread you like (for that reason we have such platform), but mark them as opinions and tell the auditorium about your level of expertise on that topic, then you act fair and are welcome. Location: Fox Island I submit this as a question not a solution and don't want to dilute the emphasis on getting a Bay dude's problem solved.


There have been some pretty impressive NC driven quick turnaround sponson and bulbous bow jobs done on steel trawlers and crabbers.
Could one slice the bottom free at the chines say the last half of the boat, scribe a new line on the transom and weld back together, tying back together with swim steps, net guards, sistered engine rails etc.? The idea being perhaps a little rocker aft might pry the bow up enough to get over the hump and up on step.
The proportions of your boat is very similar to a standard model that has been thoroughly tank tested, the series 62 model 4665. If you take a look at the thrust lines for the jet, you will find that for the J1 case, the line is shown dotted from about 22 knots and downwards.
The lower crossing between the green and red lines at about 8+ knots represents the working point (where available and required thrust balance) that you get with this setup! On the other hand, with a propeller arrangement it would be easy to make use of full power.
One thing that occurs to me as I look at these pictures is that there is a box built into the transom that houses the outboard part of the jets. I would say there is a very strong case for a set of CP propellers here, any suggestions Richard?? And for the hull, we need more experienced input on tricks to reduce hump resistance from those of you working with short, fat beauties!! Location: Seattle You guys got a couple of posts by me while I was looking for pictures.
Though I spend a total of two months on the boat a year, it actually only fishes about a month, though probably an average of 18 hours a day these last few years. In the future I plan on spending more time fishing this boat, and fuel economy will become an even bigger issue. Originally Posted by Truls Would the hull form inhibit performance with props as well, or will the extra efficiency (150 HP) be enough to overcome the blunt bow issue? But if you would be fine with ONE engine and a Controllable Pitch Propeller instead of a gearbox, you might end up with a win win situation. The boat has been an embarrasment for them for a long time around here and I think they were quite relieved when I changed the name and at least made it a successful fishing vessel. Location: south carolina building an aluma jet after 2 years i finally finished my jet boat project.
Well, as far as mine, I started on it in February of 2005, and by July of '05, it was on the water an operational. Unfortunately, this was metal-to-metal wear, and the flats of the shaft would wear out after about 100 hours, on average. The levers themselves were originally made out of aluminum flat bar, with the ends radiused. The way I did my throttle cable was to buy the cable conduit like that used on motorcycle control cables.
I also had to make my own cable brackets, for holding the throttle, steering, and reverse cables securely. The merc sj175 does offer a reasonable amount of thrust, but the downside is that in their infinate wisdom, Mercury put the exhaust from the engine in the cavity between the hull and jet unit.
I tend to think of those that do as 'old school', and perhaps we should scrap the shuttle and fly the appollo missions again. As in aerospace, the trailing edges create a vortex, much like the tips of a wing, only in water that usually means that air is bled off, if that air makes it to the intake the pump will cavitate causing loss of thrust. If I may, I'd suggest opening another thread and colate your questions and thoughts, no doubt you'd be quickly pointed in the correct direction. Surely one of you can give a technical reply, it can't be that difficult with all that knowledge and experience!
If so, will anything bolted to the rear be regarded as "hull length", or is it a non-counting appendix?


Unless the hull get sorted out, make peace with the fact that you have a displacement hull with plenty of power but too little to get over the hump to plane.
You mentioned that at WOT you only get to 8 knots - see my argument that with all that horse power available you only gained just over half a knot in speed with all that extra fuel wasted. Plotting the 4665 resistance with 30.000 lbs displacement (red line) together with the Hamilton predictions show that the computer predicition seriously underpredicts the hump resistance. This marks that full load operation at 2600 rpm is restricted to 22 kn upwards; below that, performance is reduced due to cavitation!
You also find the non-cavitating point where the 2000 rpm thrust line is crossing the resistance curve at ~7 knots. A rough first estimate shows that even with non-optimum props a total thrust of ~9000 lbf would be available 16 knots, and a max speed about 23-24 knot. After having that fail twice, I went with a spartan jaw coupler, the one used on the Kawasaki 750 jet skis.
I used jam nuts and washers to control the amount of friction required to operate the levers. As well as designing a weedless grate system, using some stainless flat bar, and another push-pull teleflex cable, with a specially designed watertight housing where the cable goes into the intake scoop. As I remember, they are nigh impossible to get hold of (you may have to order directly if you can find the website) but they are well worth reading. If you have a 'rocker' the boat will bounce around, or porpoise, if it has a hook it will bow steer badly, possibly causing the boat to spin in a turn.
Look at not only straight line performance, but also where any vorticied will end up in a tight turn (if you terminate your strakes ahead of the intake), if the unit cavitates during a turn and you loose thruse, a real nice jet spin often occurs, sometimes at an inconvient moment!!!
This explains why your engine is making 2800 rpm; the jet is cavitating heavily and the engine is overspeeding with fuel restricted by the centrifugal regulator. From this, the cavitation limit can be calculated for other rpm's and speeds, see the green line.
Then, I took some small brass round rod, drilled and tapped it for setscrews, and then a cross drill for the cable to fit through. By shutting off the engine, then, pushing down on a handle lever, I can drop the intake grate, allowing it to clear off any weeds. Although they are still in the process of editing the footage right now, I'm fairly certain this boat will be seen on TV, as it was hauling members of the camera crew. You have a strange logic and a blind faith in someone else you probably don't even know, so, if I'm not an amateur or I don't think they're experts then I'd be right to question and query them, right?
Even if full load cavitation-free operation could be achieved below 22 knots, the thrust margin would not allow stable operation.
Sand and mud or muck bottoms will destroy all COMMON built jet drives and possibly you if you eject in a turn with a channel marker pole in front of you.
A mini scatter shield is a very good idea for the rare times they let go completly because no one saw the first of the 3 links opening.
I used the existing design of the Sea Doo Jet Boat's weedless system as a model for my design.
Look into their backgrounds, check their experience, listen to their reasoned arguements (both here and around the forum), you will get a feel for who knows what they are talking about and who likes to drivel on.
As shown above, there is a possible saving, due to the higher efficiency, of about 150 hp at this speed.




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Comments to «Jet boat design build 2015»

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