Tuesday, July 28, 2009

Stargazing (Equipment Tips)

Though the best instrument for stargazing is your own two eyes, there's nothing like bringing lunar craters, star clusters, or nebulae into focus with a quality pair of binoculars or a small starter telescope.

Around $250 will buy a refractor scope with a 60 to 90 millimeter lense (about two and half to three inches), a tripod mount and a couple of eyepieces. Look for one with a filter , not for solar viewing, which should never be done directly, but for observing the Moon. Seen unfiltered, the glare of the full Moon can be as painful as a car's headlights. Also, steer clear of the generic models sold at discount department store chains.

A pair of 7x50 binoculars offers a comparable field of view and magnification of an entry-level telescope for a bit less money. Planetary conjunctions, lunar occultations, even the next great comet, will look just as sharp through good binoculars. The view suffers only with the lack of a tripod mount. You may want to brace yourself against a tree for steady observing. On the otherhand, binoculars are much more portable than a telescope, a handy feature if you have to drive beyond the glare of city lights to do your stargazing.

Thursday, July 9, 2009

What to Look for when Buying a Inflatable Boat

As you may know, specialization of today's inflatable boats is now in the of the minds of the designers. Each distinct group is specifically designed for a different set of applications and is built and equipped with different components and equipment. Most inflatable boats today fall within one these specific categories.

If all you need is a small boat to get you from ship to shore, then a typical inflatable tender is the best answer. If you're after a medium sized boat for diving or watersports there are many choices. If a large rigid-hulled inflatable (Rigid Inflatable Boat or RIB) for recreation, rescue or work is what you need, there are again many designs available with a wide variety of standard and optional components. The choice is quite wide through the entire spectrum, ranging from very compact models with simple slatted or inflatable floors, to larger tenders with inflatable or wooden keels and solid wooden or aluminum floors, up to the fiberglass or aluminum rigid-hulled inflatables. To avoid confusion, before buying, or even shopping for an inflatable, discuss and decide on exactly what the uses or requirements will be for your new inflatable boat. This will minimize the models to choose from, which in turn will minimize confusion.

Dealer Location and Reputation
The location of the dealer is important because you don't want to have to travel too far for you inflatable boat needs. Whether it's parts, repairs or just technical support and friendly customer service tips, a close dealer can be a close friend. In particular, as a new boat owner and perhaps new to inflatable boats, you may have questions, need to claim warranty, or need regular servicing to maintain a warranty. Any way you look at it, closer is better.

Years ago, inflatable boats where the most expensive boats on the market and only a few people could afford them. This was due to the use of exotic materials and the hours of meticulous hand labor which went into their construction. Now, the boats still use the best materials, but in the late seventies, the companies started investing millions of dollars in computer-driven assembly equipment. This enabled prices to be dramatically reduced as economies of scale rose, enabling more and more consumers to enjoy affordable inflatable boating. Zodiac and its sister company, Sevylor, are now the leading low-cost producer thanks to these technological investments. So be wary of inflatable prices substantially below the Zodiac/Sevylor line. They may be either produced in developing countries by unskilled labor, or marketed by companies who are unaware of the importance of profit margins. They will be glad to see your dollar today but may be unwilling or unable to fix a problem later, or supply that much needed spare part.

You may be enamored with competitor's claims, all of whom will promise they have the best or longest warranty. There was even a lifetime warranty offered some years ago by an inflatable boat company that soon enough disappeared. A lot of manufacturers use attractive warranties as a substitute for quality or proper boat design, or simply to shore up a lack of product features. You should also be sure in your own mind that the company will be around long enough to deliver.

Friday, July 3, 2009

Small Boats and Diesel Engines

The question of whether gas or diesel is a better power choice, some other factors that come into play such as hull efficiency and windage in superstructures.

Diesel becomes the better choice in direct proportion to the amount of weight being propelled. Horse power and torque are two different measures of power. Torque is a measure of the kinetic energy that builds up in a rotating engine. The higher the torque, the more power it takes to slow the engine down and it takes more power to make it work harder or, the engine will carry a heavier load with less strain. Diesel engines develop more torque for several reasons. One is because of their greater mass. But they also have compression ratios three times that of a gas engine, which also develops more torque. Gas engines develop most of their horse power at the top end of their RPM curve, diesels develop more power lower on the speed curve because of their greater torque, which can be thought of as the reserve power behind the rotating shaft.

Diesel's great advantage is carrying more load with less strain on the engine due to higher torque generated. Small, lightweight diesels, such as those made for small trucks, have a much lower advantage simply because the torque is lower. When dealing with lighter loads, that advantage disappears. There is also an issue of kinetic energy, which is energy that builds up in rotating parts such as flywheels, which helps sustain the load. Another advantage is that the diesel will develop that power with less fuel. But that advantage is nullified by the much higher initial cost of the machine itself. The only real advantage is in the amount of fuel tank space savings since you can have smaller tanks with a diesel. Otherwise, few boaters run enough fuel through diesel engines for fuel savings to make up for the high cost.

By the time a boat reaches 16, 000 lbs. or around 36 feet, it is approaching the limit where a gas engine can power it efficiently. Not only is there the issue of weight, but the water resistance on a larger hull. Gas engines begin to build up too much internal heat and the strain begins to result in lower service life in larger boats.

Internal displacement is the best measure of an engine's ability to deliver power efficiently. The rule for service life is that the more power is squeezed from an engine block, the shorter it's life span. A ratio of 1:2 is about ideal for a marine engine, but at 80% to 90% at least yield reasonable service life. At 1:1 and above it should be considered a high performance engine with a very short service life indeed.

Speed / Weight: Other factors come into play, engine speed and weight. There is no escape from the fact that fast turning diesels have shorter life spans. Slow speed diesels can be longer lived precisely because they do turn much slower.

A pair of medium weight diesels can easily weigh 2,000 lbs. more than a pair of gas engines. In a 30' boat, an extra ton is going to result in a considerable speed loss because of that extra weight. In terms of speed, this gives a considerable edge to the gas engine. While everyone knows that gas power is faster, few people consider this point. The light weight diesel at least gains the advantage over the heavier counterpart in terms of speed potential, but looses out in the long run on longevity.

Diesel Advantage: If one is willing to travel at slower speeds, the one great advantage that diesel holds over its gas counterpart is lower fuel consumption, lower fuel cost and greater range. If fuel range is a consideration, then diesel wins hands down. Of course this is entirely dependent on how fast you want to travel, if you want to run at the same speeds as gas power is capable of, then even that advantage fades.

Yet many people make the mistake of thinking that because fuel costs are less, the overall operating cost is less. This is simply not true when you figure how much lower cost diesel fuel you have to burn to make up for the added cost of the engines themselves. The average boater running his boat at 150 hrs a year. will never see any advantage from lower fuel costs or consumption.

The argument for gas engines is that they're cheap, efficient, and far less costly to maintain. And they are certainly just as reliable as diesels, all things considered.
If you still want diesels in that 28 or 32 footer, just remember that you're paying a very substantial premium for them without much in the way of benefits.

And since we're talking about small boats, if maintenance costs are a concern to you, think twice about buying a boat with large engines crammed into small spaces. If its going to cause you pain to write a check for $1500 or $2000 for what should seem to be normal maintenance work, you had better consider whether a repairman has to dismantle part of the boat in order to change a water pump.

There's always a trade off for the boat that seemingly has everything, because the extra space was obtained at the expense of engine room or compartment space. When the engines are put in with a shoe horn, rest assured that every aspect of maintenance is going to cost you more, and sometimes a lot more. This is particularly true when considering a used boat. If the front and outboard sides of the engines can't be seen, yet alone reached, problems develop that aren't observed, and therefore not maintained or repaired. There's not much chance of discovering a serious problem and correcting it before serious damage is done. When surveyed, boats with tight engine compartments almost invariably are found to have more engine problems than boats with engines that can be reached on all sides. Its a small thing that usually adds up to big dollars. Small boats with big diesels are usually the worst offenders.

New EPA rules are going to have a major impact on diesel engines. The mandate to make them lighter, more fuel efficient and cleaner is going to translate into engines that are vastly less reliable. Why? Because they're going to start cutting out all that necessary extra cast iron, and in many areas start replacing it with cast aluminum. The marine engine industry tried cast aluminum once before back in the late 60's, it didn't work then and won't work now, never mind all the smoke they'll put out about "technological advances