Propeller – freewheel or not?

Is it best to allow your propeller to freewheel when sailing, or should you lock it? Here are a few considerations:.

The first issue is drag: Under sail with the engine stopped does the propeller create more drag when it’s locked or when it’s allowed to freewheel? You would think the answer would be unequivocal – and it shouldn’t need rocket scientists to work it out. But just to be sure, some rocket scientists, or their marine equivalents, did work it out recently and their answer is unequivocal: There is less drag when the propeller is allowed to rotate. Scientists at MIT and at Strathclyde University agree on this. It is fact.

So, we know we get less drag with the propeller rotating but what are the other arguments for and against allowing the prop to turn?

Noise: The rumble from a rotating propeller can be quite intrusive, particularly if you’re off watch in a stern berth. Some people can’t stand the noise whilst others find it interesting; they like to judge the speed of the boat by the level of noise.

Energy recovery: If you want to run a generator off the shaft it has to turn – simple.

Wear: Where there’s motion there’s wear and tear, if not damage, to drive train bearings and seals.

Gearbox damage: Clearly you shouldn’t be risking damage to your gearbox or losing your warranty protection just to get a half a knot of boat speed under sail or to get a good night’s sleep in the quarter berth.

It seems that Yanmar became so concerned at the number of requests they received for clarification on the best practice for their engine/gearbox combinations that they issued a directive: The gearbox must be in neutral when sailing or your warranty will be invalidated. If you want to stop the shaft use a shaft brake, they say, not our gearbox.

I have to admit that I sailed for many thousands of miles with my Yanmar 3GM30F in reverse gear to stop the shaft rotating and I never had a moment’s trouble. Just lucky?

If you have a Hurth/ZF gearbox you must not select forward gear when sailing forwards. Or reverse when sailing backwards, obviously. Apart from that, use the gearbox in reverse to lock the shaft or let it run free, it’s up to you.

With a Borg Warner Velvet Drive transmission you can do what you like, it will rotate anyway.

On some gearboxes damage can occur because the engine needs to be running to provide lubrication; with splash lubrication there isn’t usually a problem, so check the manual.

It boils down to this: If you are obsessed with squeezing out the last fraction of a knot under sail you need to let the prop freewheel. You’ll be happy to accept any wear and tear on your cutlass bearing and you’ll issue ear plugs to those that find the noise is keeping them awake.

If you’re worried about wear or can’t stand the noise you’ll want the shaft stopped and whether you do that by using the gearbox or a shaft brake will depend on your gearbox manufacturer’s advice, and whether or not you’re going to obey it. Simple, really.

Coaxial cable – what size?

I’m often asked what size and type of coaxial cable is suitable for a marine VHF antenna system. Well, the first thing to say is, it must be 50 ohm cable. Bits left over from your TV installation won’t do, that’s 75 ohm cable. Next, think about the environment in which it must work: Lots of movement – anyone who’s been up the mast in a seaway will know all about that – so a stranded centre core is essential to avoid breaking due to metal fatigue. Then there’s all that salt spray and rain about, so tinned copper is better than plain copper to avoid corrosion. If you use non-tinned cable you must be meticulous about sealing the end fittings.

Then we come to cable size. The smaller the cable, the higher the power loss (attenuation) between radio and antenna. For cruising boats a good guideline is to aim for not much more than a 50% loss in the cable run, this is 3db and limits the popular 5.5mm RG58 to about 10m and RG8X to about 20m. If you race under World Sailing rules the requirement is a little tougher. They want no more than 40% loss, or 2.2db:

World Sailing ( International Sailing federation) regulations.

3.29.1 The following shall be provided:  

       a) A marine radio transceiver (or if stated in the Notice of Race, an installed satcom terminal.

      b) an emergency antenna when the regular antenna depends upon the mast. 

  2)When the marine radio transceiver is VHF

      i) it shall have a rated output power of 25W

      ii) it shall have a masthead antenna, and co-axial feeder cable with not more than 40% power loss.

     iii) the following types and lengths of co-axial feeder cable will meet the requirements of OSR 3.29.1

(a) up to 15m (50ft) – type RG8X;

(b) 15-28m (50-90ft) – type RG8U;

(c) 28-43m (90-140ft) – type 9913F (uses conventional connectors, available from US supplier Belden);

(d) 43-70m) 140-230ft – type LMR600 (uses special connectors)

Coaxial cable is an important component of the VHF antenna system, choose wisely to get the very best out of your VHF radio or AIS transceiver.

VHF antenna systems

Just a reminder, there is a technical information section at saltyjohn.com where you will find articles on selecting, installing and troubleshooting VHF antenna systems.

Have a look, the link is over there on the right.

(To avoid confusion, I should point out there are references in the articles to the Alpha One antenna which is no longer available.)

Super-duper scooper

Here are the complete manufacturing instructions for a very useful item on any boat – dinghy, rowing, yacht, motorboat, narrowboat, barge. It’s a baler. Its soft sides conform to the shape of the bilge and make it more effective than a hard plastic baler. And, it’s cheap as chips.

You’re welcome!

Dipping the eye

There’s etiquette involved in mooring-up to a post or cleat that’s already occupied. It’s called “dipping the eye” and if you don’t think it important let me tell you it was the subject of a thirty-page discussion on a boating forum just recently. I use the term “discussion” somewhat loosely.

Anyway, the procedure is shown in my sketch. The most recent arrival passes his line through the loop of the incumbent’s line, then over the post. Thus, when the incumbent wants to depart, his line isn’t trapped by the new arrivals line. Simple, really.

Naked sailing: The bare facts

Cruising small boats in sunny climes involves a great deal of nudity. It sometimes seems like the sailing kit of choice is SPF40 sun tan lotion and a hat. If it rains you take off the hat and reach for the shampoo.

It’s amazing how quickly inhibitions disappear under the spell of sunny skies, gin-clear water, sandy beaches and exotic rum drinks. Freedom in all its manifestations is why we’re here and we aren’t going to miss a bit of it, we’re getting our kit off.

In any remote anchorage in the Bahamas or the Caribbean the hour or so before sunset is an extravaganza of naked sailors. On deck, on the boarding platform, even in the dinghy, there are glistening bodies going through the afternoon shower ritual. Some perform under a sun-warmed shower bag hanging from a halyard, others have luxurious plumbed-in deck showers and others do it all with salt water and a final rinse of fresh water from a spray bottle. It’s all good.

Any time of the day you’ll find naked people walking the beaches or pottering around on deck doing the daily chores. Even at beach parties it isn’t long before the more laid back revellers discard their fancy-dress costumes – after all, just how comfortable can coconut-shell bras and grass skirts be? And if you haven’t seen a naked limbo competition you haven’t lived.

Public nudity in the Bahamas and the Virgin Islands is illegal, of course, so you won’t be walking around Nassau in a thong, but in the more remote places no-one seems to care. An all-over tan is the badge of a long-term cruiser – been there, done that, lost the tee shirt. (Got the malignant melanoma, too, so make sure you take all the appropriate precautions).

Chesapeake morning

Autumn was in the air, a magical time on Chesapeake Bay. The breezes were back after the stultifying heat and calms of summer, the trees were starting to acquire what would become a mantel of gold, red and brown, and delta-flights of honking Canada geese were arriving for the winter. Early that morning I stepped onto a dew-covered deck and watched the mist rising like steam; all was quiet except for the occasional slap and roil of a fish taking its prey. The first hint of the sun showed itself through the trees on the eastern shore, a promise of another fine day for sailing. But sailing would come later, when the wind arrived. For now, I finished my coffee and slipped below for another hour in the snugness of a still-warm sleeping bag.

Easy-fit cable kits

Some people just don’t do soldering. If you’ve never soldered, don’t own a soldering iron and don’t want to learn a skill you might use twice in your life then soldering PL259 connectors is not for you.

When Salty John supplies an RG58 coaxial cable kit, it comes with a PL259 fitted at one end and another supplied loose for fitting by the boat owner once the cable has been run to its destination. This is the standard screw-in earth, solder, PL259.

But now, to make things much simpler for the non-soldering sailor, they’ve introduced the Easy-fit PL259. Just screw it onto the end fitting once you’ve run the cable. The Easy-fit cable kit has one fitted and soldered PL259, but the other end terminates in a small-diameter threaded connector onto which you screw the supplied threaded PL259. Couldn’t be simpler.

The main drawback is that you can’t shorten the cable without losing the threaded end, obviously, so you’ll need to coil any excess cable and secure it out of the way. Another slight disadvantage is that the tip of the cable is slightly wider (8mm) than the bare cable and is rigid for the end couple of centimetres – really tight radius corners are out. But for ease of installation you can’t beat the Easy-fit cable kits from: saltyjohn.com

Easy-fit cable kit RG58 10m