Triple waterjets

We chartered an AB when we went to Spain. We loved it in every way. Only criticism we had was that it wasn't as fast as some they offer, only had a max speed of 47 knots and a cruise of 36 knots. We were short of time and the ability to move around the Med quickly for our couple of days there was incredible. As to the boat, it ran and handled like a dream. We're fans of jets but had never experienced them on a boat that size before. You don't have to run it fast, but then you sure can enjoy doing so. It somehow combined the sensation of a smaller sport boat with the luxury of a large yacht.

We will at some point own a fast larger boat and it most likely will be jet propulsion.

AB's nearest model would be the AB 92. The CCN "Freedom" does use a similar propulsion arrangement to that AB uses with MTU and Rolls Royce and with the center a booster type unit. I don't know the HP on the CCN but imagine it's less plus the CCN is aluminum and the AB is glass.

Wish I knew more on the fuel consumption. My first thought is you have to spin up and get on plane before ANY benefits come into play. There must be still a nice fuel bill every night.

These are ideas I have but no experience on. I would think down da ditch in slow speed, just the center engine, but again I'm guessing.
I look forward to more replies here.

AB used 3 x 1825 hp a few years ago in a 92' to achieve the kinds of speeds CCN achieves. The current model with 3 x 2600 hp, running at WOT uses about 5.5 gallons per mile. Running with 7800 hp at 40 knots they use about 4 gallons per mile. Sounds horrible until you consider that we use 5 gpnm running an 85' Pacific Mariner at 25 knots or just under 4 gpnm at 23 knots while only 3.7 gpnm at 20 knots. From what little I've gathered, running at 20 knots you're using so little load that it's not going to be much different from other similar boats running that speed. At 20 knots, the AB 92 would use less fuel than our PM 85, but it also weighs less. Now, might we use more fuel if we had the 92? Yes, because we'd seldom run offshore at slow speeds like 20 knots.

Incidentally, a Pershing 82 will use nearly 5.3 gpnm at 42.8 knots and 5.2 gpnm at 34.5 knots with 4870 hp and surface drives.

What we observed indicated at similar speeds you were talking similar consumption, even less on the triple jets cruising at some lower speeds although more in accelerating to those speeds. Now, AB is likely made lighter and with more hp than the CCN. It's our belief that with an AB we'd use no more fuel per mile than we do now and perhaps less.

There is a perception that jets are less efficient than props. That's based on the smaller jets with large engines often used in smaller recreational boats and even the jets used in small Ribs. It's not true when you reach a certain size and you use jet systems like the MJP system and you couple them with the amount of power these boats have.

Now, no one who has great concern over fuel efficiency buys a 50-55 knot boat. As to the CCN, I don't know their buyer but suspect not fuel conscious. Pershing and Mangusta, even Riva buyers aren't focused on fuel. If we were fuel conscious we'd run the PM 85 at 10 knots and only use 1.4 gpnm, but we don't do that. Of course then we'd probably have a displacement boat of some sort. Although we've been told most Westport 130 owners run at 12 knots, we run more at 20 and average 15-18 knots so we use twice the fuel we could use if we ran slower.

With the advances in Welding equipment, aluminum is a cheaper alternative than high tech composites for weight savings.

Not saying better, just can be done for a cost savings.

Well, normally we do measure in nmpg, but it's always less than 1.

Interestingly, their Fuoriserie Custom line of 4 boats are all aluminum. In their regular models, 2 are composite, 3 are aluminum and 2 are steel hulls with aluminum superstructure. I guess the real outliers are the two Flying Sport models which are composite.

They offer it with twins or with the booster. Also interestingly they offer it with MAN engines. They show 1900 hp or 2300 hp but I didn't know MAN offered more than 1900 hp and apparently MAN doesn't know either as they only show 1900 hp max on their web site. Either way, it seems strange to me that you're building a "fast jet boat" where there's one builder clearly the leader in such boats and you build it to run 10 knots slower than anything AB builds. Perhaps they're building for a superior ride or with something else in mind or it's just what the customer wanted and was happy with.

As a potential buyer of such a boat, the lack of speed would eliminate it from our consideration. I know that seems strange to say on a boat with WOT of 40 knots and cruise of 34 knots but it's all comparative and the type boat. Interestingly, their 86' flying sport achieves 39 knots WOT and 35 knots cruise with twin 1920 hp MTU's and conventional drives and their 102' flying sport achieves 38 knots WOT and 32 knots cruise with twin 2640 hp MTU's and conventional drives. So, it's not appreciably faster than their conventional composite models.

Ask the Navy how they are enjoying their triple jet alloy boats.

https://taskandpurpose.com/navy-littoral-combat-ship-problems/

None of which has anything to do with triple jets. Just typical Navy and contractor screw up.

We found the ride to be great at those speeds and at lower speeds more than acceptable. By that I mean it will handle rough water well at lower speed, but at 12 knots it won't handle rough water as well as a heavier full displacement boat would. It would handle fairly rough conditions (what some would consider very rough but we wouldn't) well still at moderate speeds of 20-30 knots, better than at 12 knots. Only at extreme conditions, which we did not encounter, have we been led to believe it will be better at 12 knots. That's really not all that different than other planning hulls we've been on. Many handle 4-6' at 6 to 7 seconds better at 20 knots or faster than at 10 knots.

You really feel a lot more in control at high speed in a 100'+ AB than in a 39' Center Console running 50 knots. You're still more in contact with the water.

It's a bit like a fine sportscar where if you're not careful you'll find you're going much faster than you thought just in the ride and handling. Still though you get the sport boat feel.

Most videos only show smooth water but this one has a little wake crossing at least.

https://www.bing.com/videos/search?...97F57F282D281E032C5897F57F282D28&&FORM=VRDGAR

I have been commenting of these POSs for a while. Somebody please open up a new thread on these.

On the original Post. I'm learning. Keep bringing the info up.
Thx

Also aluminum makes it easy to make hull or superstructure changes from boat to boat, or just a one off boat without the huge expense of first making a mold.

As for jets, they are efficient in a narrow rpm band of what their design parameters are (cruise or wot usually). The slower and slower you go below that, they become horribly inefficient.

Hi CaptPKilbride, from our past conversations, I’d love to talk with you about Jet Drives and can do so at your convenience. Just finishing a new build currently that will be out on the water in the coming weeks.

My brother (Freddie) has since retired from shipbuilding and left it for me to deal with.
Welded alum is cheaper to build in half the time as carbon fibre/fiberglas/kevlar moulds. I use a lot more of it now that I'm back building sail cats. As to water jets - I've never found them to be that efficient as compared to Arneson drives. Sure wastes a lot of fuel though.