Pocket cruisers

Lh ?

How do you come for LH = 7.5 m.

My copy of 8666:2002 exclude from LH detachable items, and lists as examples outboards and outdrives, but specifically includes "detachable parts of the hull wich act as hydrostatic or hydrodynamic support".

The shape of the jetpack do provide significative hydrostatic and hydrodynamic support.

I am asking this, because LH is an important length for ISO, for the scantling. But is also sadly a basis for taxes. (french tax lower limit is 7m, and belgian is 7.50m)

 

Another way to solve the engine space problem is two small engines under settles as devlin czarina 30 :
http://www.devlinboat.com/dccz30.htm

 

Thanks for your interesting comment.
The Jetpac provides hydrostatic and hydrodynamic support, for sure, but in my understanding of ISO 8666:2002 we should not consider it a "detachable part of the hull", but an outboard engine. Anyhow as it is quite important to me to properly check this important matter (precisely because of taxes in Spain where 7,5m is also a limit), I think it's wiser to put the question to a Notified Body. I'll do that.
Cheers.

 

I read this whole thread,i guess it all comes down to money and how biga pain in the butt u want your boat to be,trailering some giant heavy thing around once in a while,still dosent sound good,are u married?and no im not interested.would make a big difference on how and what u do this with.A smaller easier to tow boat would be my answer.mabe the sailboat turned motorboat would b good,sure would use less gas.something like a McGregor 26?with a small outboard it would cruise preety good.from reading all of the posts i almost want to find one and do it myself.could tow it with any normal pickup truck instead of a high dollar diesel.curious what you decided.

 

Happily. Six children

 

Makes a difference in what kind of boat to have,if the wife isnt happy nobodys happy kinda thinking!with six kids u could save fuel with a buncha oars.Then they would be to tired at the end of the day to cause much trouble.

 

Wonderful idea! I have to try that in my present boat, a 12 tonnes motorsailer!

 

Six kids should equal 2 or 3 hp

 

Having put the question in written to the Notified Body I use to work with, they tell me they do not consider the JetPac as part of LH. Excellent.
Cheers.

 

Another funny thing in LH "cheating", is in the beneteau powerboat range.
The Antares 760 is 744cm Lh. The bigger Antares 8.8 is 749 cm Lh.
Commercial length 1.2m bigger, Lh 0.05 m bigger.

Some day, you will have "removeable" stems. Just imagine a vertical watertigth bulkhead at FPP. Bolt on this a stem. This stem is not structural part of the boat, do not have hydrodynamic/static support (just barely touch water at rest), and is removeable. So all the front overhang do not count for Lh.

 

This has been done. I had an 1970's vintage S&S boat that had a removable stem part so it could rate under both IOR and MORC.

It was only a tiny fitting, but I took the idea further on a more recent design to allow a boat to enter short handed races, some of which have a 30ft max and others a 30ft min loa requirement.

 

That's common practice with sterns. Many models around have 7,49 m LH (because of the 7,5 m limit in several countries) and named "Whatever 820" or the like, having huge bathing platforms being some of them real removable sterns. The removable stem you mention, fcfc, is an interesting loophole, indeed. I think it may open very interesting possibilities. Mmmmm....

Have a look at this interesting scandinavian boat: Yamarin 74 Cabin
http://www.yamarin.com/index.cfm?ChangeSetNow=5

LOA 7.40 m (24ft 3 in)
Beam 2.60 m (8 ft 6 in)
Weight 2100 kg (4630 lbs)
Berths 3 + 2
Max power 165 hp (Yamaha ME372)
CE Category C
Price (inc VAT) from 62,295 british pounds (Wow!)
It is said to cruise economically at 25 kn, having a top speed of 31 kn

 

Amalgamation

Amalgamation: a mixture or combination. And so this posting will be. As always, this is just my not so humble opinion.

As I recall the thesis of this thread – a discussion of boats suitable for cruising in protected waters and coastal areas.

First off – let’s toss this one into the ring as an example from years past that was eminently suitable for coastal cruising. I AM NOT suggesting this is the perfect boat for today’s market. But why not something similar?

Let’s chat a bit about fuel. Some threads here and some on the Usenet (rec.boat.cruising) are alternatively suggesting that fuel in the near future (5-10 years) will be plentiful, just more expensive. Then someone comes along with the Peak Oil theory and argues that if you don’t have a blow boat you won’t be able to go anywhere in 5 to 10 years. Hopefully obvious to other folks besides myself is that the truth probably lies somewhere toward the middle of those two extremes.

I’d suggest that we will indeed pay more for gasoline and diesel and natural gas and kerosene etc. In fact, any product that has a petrochemical base – plastics of all sorts, including epoxy. But I do not believe that oil based fuels will dry up completely in (at least) my lifetime – which, God willing will be another 40+ years.

Some folks posit that sailboats are more suitable as they use less fuel. I’ve read arguments that 1000 miles of coastal cruising only used ~100 gallons of fuel on a sailboat, but used over 800 gallons on a similar sized powerboat. Of course the person posting this tidbit on rec.boat.cruising was the sailboat guy and overlooked replacement costs of sails and rigging as they figured total costs. Then he also overlooked the speed factor. The boat that burned 800+ gallons was a heavy semi-displacement boat (specifically mentioned was one of these) that was pushed into the multiple gallons per hour speed range instead of the sailboat’s displacement speed. Apples and avocado’s both grow on trees, as both types of boats float, but that’s as far as this comparison can logically go.

<snark> Other folks are OK with driving a Hummer, Escalante or a F250 Supercab as their commute vehicle. And don’t forget that it is their “right” to use from the worlds resources at a disproportionate rate – just because they can afford to. These same sorts of folks are less concerned about the amount of fuel that their boat uses, ‘cause it’s just another status symbol of their success and wealth. A boat is something to be used and sold as whims come and go.

As an aside – I was on eBay a couple of nights ago looking at marine diesels. There’s a Yanmar 3gm there from a 2000 model sailboat – a 40’-ish Beneteau IIRC - that had “wind damage” and wasn’t worth repairing and was being parted out – engine, winches, etc. What does trashing a 5 year old boat say about our world-wide throwaway culture? Nothing good I'm afraid. </snark>

But there are some folks – many that inhabit these environs on a regular basis – that see some folly in the idea of $400k boat sitting vacant at a marina most of the year and when it does leave the dock it costs a couple of Boat-Bucks for fuel and other necessities of the weekend.

Some of us here see the need for an affordable boat to buy (or build!) that won’t eat us alive in fuel costs. A boat that perhaps can spend several months in a marina slip or on a mooring and the rest of the year on a trailer in our side yard covered against winter’s ravages, thus saving the costs of winter storage on the hard at a marina. Or if the preparation/launching/retrieving is free of too much hassle, then the boat can live in the side yard year-round, only visiting the water as time permits.

Speaking of marinas – it seems that the value/price of water-side land is rising so fast that marinas are being bought out for condo’s and other assorted high profit developments. So that is even more incentive for a boat that is less dependent on traditional marina services.

There are even a few of us here that have the vision to see that a suitable cruising power boat can be completely trailerable without being a burden to trailer, launch, retrieve and store at home.

Having read this thread since May 2006 I think that the “general consensus” is something between 7.4 and 9 meters in length and a maximum beam of (depending on the country) of about 2.4 to 2.7 meters.

Some folks are less comfortable with boats that are longer and weigh more. Some folks have no problem with the idea of a boat that is longer and heavier. So it all comes around once again to what’s suitable for an individual circumstance.

Recognizing that some folks have tax and regulation issues to deal with for the longer and wider boats, I believe that a distinction that needs to be made is the duration of the cruise and the amenities that one wishes to take along. If we recognize that a three day weekend outing four to six times per cruising season with a single ten day cruise thrown in, involves a different set of requirements than an extended cruise of two or three months duration. Once this distinction is recognized – that the heavier and longer boat will be launched and retrieved once or twice PER YEAR versus six or seven times (or more) for the shorter lighter boat, then we can more easily justify the time and expense of the preparation/launching/retrieving of the larger trailerable boat.

If one has a weekend to cruise and get back to a paying job on Monday, then ease of use – setup, launching, speed and range, retrieval and making road ready are of paramount importance.

Whereas, if one is going to trailer to a distant launch point for cruising grounds such as Puget Sound and Alaska, the coast of Maine, the Trent-Severn Canal and associated Great Lakes, etc. – for a summer long cruise, then the amount of time it takes to tow the boat there, set it up and launch it is of much less importance than to the weekend guy. And to our European, Australian and New Zealand friends, please forgive me as I know not where you would want to trailer a boat for extended cruising opportunities. So I only cite where I would like to go in North America.

I can certainly recognize the G-PITA (Giant Pain In The ***) it would be to try to do the weekend cruise thing with a heavy, large boat. I would theorize that most folks can also easily see those drawbacks and with the rare exception, try to avoid that sort of hassle.

Additionally, I can also see where some folks might not want to hassle with the larger boat at all, regardless of the duration of the cruise and any additional comfort potential it would provide. And that is why ice cream stores offer 31 different flavors.

Back to fuel. One might suppose that the folks that are interested in the “weekend” pocket cruiser would be less concerned about fuel usage than the longer use folks. Perhaps so, but there is nothing to prevent designing and building a boat that sips, instead of gulps, fuel – as long as the end user fully understands that 35 knots ain’t gonna be economically possible – along with the resulting higher horsepower and stronger, heavier boat needed to carry the higher horsepower and tankage, ad infinitum. So the cost of playing around on the water for the weekend is gonna skyrocket to several hundred dollars for the ephemeral joy of going fast for a short time.

But as shown in several different threads over the past few months, there are designs that can cruise in the mid-teens and still burn only a few gallons per hour. Y’all know of my positive bias toward Tom Lathrop’s Bluejacket series. Using Tom’s reported fuel usage; it’s possible to do something like 130 miles (209 km) on about 20 gallons of gas. That’s far enough to get from the launch point to a quiet anchorage in two hours on a Friday afternoon. Another 50 miles (80 km) of messing-about on Saturday to a completely different anchorage and ~50 miles (80 km) back to the launch point on Sunday.

Personally, I am still not convinced that a semi-displacement boat can achieve these sorts of mid-teens speeds with the same sort of low fuel consumption rates, irrespective of Whio which Guillermo cited to start this thread. I’d love to be able to completely understand how a hull that is not performing in displacement mode or in full planing mode can NOT use fuel at a prodigious rate. Witness the anecdotal tale above of the sailboat versus the Nordic Tug style boat. Can anyone cogently make the semi-displacement case?

Then we have the gas versus diesel discussion. Inboard marine gas engines are (comparatively) cheap, easily found and installed. There are some drawbacks in that gasoline is more volatile and requires some special precautions to keep the boat from exploding! Inboard diesel engines more efficiently use fuel and don’t require the same precautions to keep the boat from exploding, but initially cost more.

Although not having personally run a spreadsheet on total gas vs. diesel costs, I would suspect that the equation would look somewhat similar to the sail versus power comparison when the costs of sails and rigging maintenance/replacement is factored in. Can anyone comment on the inboard gas/diesel installation and running costs?

Let’s close this treatise out with this thought. A boat similar in looks to the Elco Cruisette I first mentioned with a modern efficient underbody and built with modern methods – lightweight fiberglass foam sandwich construction for commercial production and/or lightweight strip/cold molded with epoxy/glass construction for the home built folks – could very well be a winner. Put some nice wood topside with a bit of varnish and I’d suggest that oohs and aahs would follow wherever the boat was floated.

Best,

Leo

 

A very comprehensive look at Gas vs Diesel is offered ,

http://www.yachtsurvey.com/GasDiesel.htm

For all but the longest range HEAVY vessels , the gas option would seem best.

INCLUDING engine life , and cost of ownership maint!

FAST FRED

 

Nice post, Leo.
There are also some extra considerations to take into account when choosing a boat, either for weekend or long range (or long time) cruising.
One of them is if you have or not little children. One of the problems I had experimented with my beloved Banjer "Marie", being a really heavy weighter (and so slow, what I personally like) is that my children get bored if sailings are longer than, let's say, 1 hour long (You know that kind of questions: when will we arrive? how long it will take, etc?). So I can manage to get them awake and interested (except when we are trawl-fishing, which keeps them well awake) only for something like 7 miles, 10 at its most, when cruising. This keeps us very close to the home port, to my taste, and the one who gets bored, after doing this, weekend after weekend, it's me. And when we go cruising for longer periods, it would be nice to be able do 20-30 miles in a row in 1-1.5 hours time, this allowing switching from Ria to Ria in an easier mood, and reach more distant anchorages and marinas.

The boat I proposed some posts ago to fulfill this kind of demand, the JetJane 25, allows a couple with two children (or even 3) to do this kind of cruising scheme. They will be able to reach a 30 miles far away destination in 1.5 hours, which opens a lot of possibilities for weekends and the typical 10-15 days cruising in summer.
And if sometime they want to go for real long range cruising, they may do more than 700 nautical miles at 6 knots with the 300 lt (80 gall) tank.

About your question on the consume in the semiplanning zone, there is a difficult to predict zone between 1.4 and 1.8 S/L ratio, more or less, but from there up, power needed is quite predictable (always supposing an efficient design, of course). At an S/L ratio around 2.2, JetJane 25 should trot along at 10 knots, using an shp power of around 36 hp and a consume of 1.7 gph. Range would be in excess of 400 miles (All this with a total load of more or less 1000 kg, with full tanks. Of course fuel and water consume will lower this weight and will increase either speed or range)

Cheers.

P.S. Here the specific consumption table for the JetPac D150

150 HP
RPM --- GAL/HR -- LITER/HR
750 ---- 0.27 ---- 1.02
1000 --- 0.30 -----1.14
1500 --- 0.70 ---- 2.65
2000 --- 1.60 ---- 6.06
2500 --- 3.00 --- 11.36
2600 --- 3.30 --- 12.49
2800 --- 3.80 --- 14.38
3000 --- 4.50 --- 17.03
3200 --- 5.30 --- 20.06
3400 --- 6.30 --- 23.85
3500 --- 7.00 --- 26.50
3600 --- 8.30 --- 31.42