Windsocks and buoys

[Matty F]

I want to make a windsock and a few bouys with flags, for one of my other hobbies, sailing. They should last without corrosion in the sea and be made at almost no cost from whatever is lying around the workshop. I can use the floats and anchors from the existing buoys. The existing buoys have deficiencies so I want to design new ones. The existing buoys twist around and wind the flags up so they don't fly anymore. I was thinking of running a wire through the top of the flags to keep them straight. When the tide is going out the existing buoys lie almost flat because the anchor is attached to the bottom of the pipe that runs through the float. I reckon the anchor should be attached to the float (i.e. halfway up), and I'll have a heavy weight at the bottom of the pipe.

For all of them I was thinking of using high tensile galvanised fence wire sharpened to a point at the bottom which will rest on a flat surface, probably nylon. The flags or windsock will be attached to the wire. The wire will run inside half inch plastic water pipe, with a nylon washer at the top so the wire doesn't come out.

The windsock will need to stand bad weather as it will be permanently mounted on a pole at sea. It doesn't want to look expensive or someone will steal it. I may need to allow for shags allighting on it or attacking it. I'll drill a hole on the top of the pole and hammer in a two foot piece of steel reinforcing rod that's been zinc coated. The plastic water pipe will fit over that.

Have I forgotten anything? I need to make these by next week!

[Nightjar]

I would not trust to galvanised wire, particularly not any that has been sharpened to a point, removing the galvanising locally, to survive long in a marine environment. You really need 316 stainless steel.

Colin Bignell

[Skipweasel]

Rather than wire, I use dressmaker's boning. It's dead cheap, doesn't poke through the fabric like a wire will (provided you turn the ends up) and is more flexible - if you bend it, it'll spring back instead of staying bent.

[Matty F]

Yes that would be ideal. Except that I don't have any stainless wire lying around so I'll have to go somwhere and try to buy some. And they won't have the size I want, or it comes only in rolls of 100 metres. I'll keep an eye out for something that won't rust. The buoys are taken in every night so they won't have such a hard life, and I can easily replace the wire if I have to.

[Matty F]

There's no dressmaking types around here, or I could use old knitting needles instead of the vertical wire. I do have spare high-tensile fencing wire that is almost impossible to bend.

"Polyester Boning - 8mm White x 40 meters - Free Delivery. Price: =A320.50"

[Skipweasel]

Is there a Dunelm Mill or somesuch near you? Or even a little haberdasher's stall in the local market? They always have it.

[Skipweasel]

--=20 Skipweasel - never knowingly understood.

[Ronald Raygun]

I suggest you should use something which *will* rust, thereby making the things unattractive to thieves.

[Matty F]

Yes thats one reason why I am not buying commercially made items. The thieves will have to take a ladder in a boat to reach the top of the 4 metre pole. So will I, but I'll go at high tide, and lash the ladder to the pole, and tie the boat up too.

[robgraham]

Matty - you really do keep this group on their toes with your projects !! It's always worthwhile reading your posts as 'Here goes Matty again with something which is a way off to the left" - and requires us all to think a little (god,...no) 'outside the box'. Rob

[Matty F]

Thanks. Somebody usually comes up with an improvement to my plans for things I've never done before. I'm almost full-time on DIY at the moment. Most jobs would be too trivial to discuss. Today I installed a 10 metre stainless steel handrail along my cliff path, and painted a shed for its first time in

130 years. Yesterday I made and painted a large door to hide my stack of timber and started repainting the house. I've spent three days taking the ignition system of my car apart after a mechanic and auto electrician failed to fix it. It now works fine.

[Skipweasel]

That's always satisfying.

[Tim Lamb]

I've got a dead VW GTi if you fancy a holiday:-)

regards

[Nightjar]

On 03/02/2011 20:17, Matty F wrote: ...

Particularly if you rinse the salt off with fresh water when you take them in. A bit of grease around the point will probably help too.

Colin Bignell

[Dave]

Try silicone grease, It is a devil to get rid of.

Dave

[Matty F]

I was going to buy a sensible VW but I went temporarily mad and bought an XJ8 which has 8 ignition coils. One of the leads was not plugged in properly. Modern cars seem very picky about little things.

There is a further complication with the buoys - I wanted to attach the mooring rope to the float at the surface rather than the bottom of the pole under the water but then sailors are more likely to catch their centre boards on the rope. And power boats are more likely to catch the rope around their propellors. Slight change of plan.

[Ronald Raygun]

Did this insight result from a thought exercise or from an actual experiment? I ask because I think your conclusion is incorrect.

By that I mean that the rope will not lie significantly closer to the surface when it's attached further up the pole (such as where the pole meets the bottom of the float) than it (or the pole itself) would be when attached to the bottom.

Remember that in the original design (rope attached to bottom of pole) the rope will be colinear with the pole, so if the buoys "lie almost flat" and if this means at an angle of 20 degrees to the horizontal, then the rope will also be descending at an angle of 20 degrees.

In similar conditions, the rope will still lie at 20 degrees even when it's attached further up.

All I'm saying is that if you've identified a design deficiency, it's not a new one introduced by your redesign [*], but is one which is already present in the existing design. That doesn't mean it is not in need of being addressed by, for example, adding a weight to the rope instead of or as well as to the pole.

[*] Actually I can see a new problem after all. In the old design, the angle at which the pole is lying warns sailors where and at what angle the rope is, so they will know to give it a wide berth. In the new design the pole is more upright than the rope, and sailors can get caught out by the rope lying at a shallower angle than they think.

[Andy Champ]

We have a bit of chain slung under our buoys to keep them upright. Then a rope, then some sort of mudweight. One of the temporary marks uses an old welly full of concrete.

Andy

[Matty F]

If the rope is attached to the bottom of the pole, it will start at a depth of about 2 feet below the suface and slope down from there. If the rope is attached to the middle of the float where it ought to be in order to not pull the buoy over when the tide is running, the rope will start at the surface, where it can be fouled by the boats. My theory is that I should put a weight on the end of the pole, attach the rope there and have another weight at the bottom end of the rope.

The novice sailors will have no idea where the rope might be, or even that there is a rope or a chain.

[Ronald Raygun]

No, this analysis is incorrect, or at least it is when the tide is running strongly enough to cause the buoys to lie "almost flat".

In that situation, if the pole is 2ft long (measured from a point inside the float which is coplanar with the surface), and the pole is lying as "flat" as 20 degrees, then the bottom of the pole will be only 8 inches below the surface (at a horizontal distance of just under 2 ft from the float).

Or it may be that you've already allowed for the sine of 20 degrees and the pole bottom really is 2ft down, in which case there would be be 6ft of pole between rope and float.

Be that as it may, it doesn't actually matter how long the pole is and thus where the rope starts, because any nearer to the buoy than where this is, there is pole instead, which is just as bad as rope for fouling boats.

Yes, but as I've tried to explain, this is no worse than before, when the boats would just hit the nearly horizontal pole instead of the nearly hortizontal rope.

Yes, I'd cgo along with that, but it depends on how strong a tidal flow this is meant to work in, strength in this case being measured in terms of the drag force which the stream exerts on the buoy [*].

In order for the weights to have a significant kinking effect at the points where they are attached, their weight must be of the same order of magnitude as the horizontal component of the tension (which is constant all along the rope). At each kink point the gradient will increase by the ratio of the attached weight to the horizontal tension.

So if the tension is 15 lbs, and the rope comes up at 20 degrees, i.e. the incoming gradient is 0.364, and you attach a 5 lb weight to the rope, then the gradient will increase by 0.333 to 0.697, so the rope will continue upwards at 35 degrees. Another 5lb weight further up will increase the gradient to 1.03 and the angle to 46 degrees. But there is nothing to be gained by splitting the weight. Had you instead put one 10lb weight in, you would have increased the incoming gradient from 0.364 to 1.03 in one go. The optimal place to attach this weight for your purposes is at a distance from the buoy which is just less than the lowest depth of water you will have (I guess this is what you meant by "at the bottom end of the rope").

[*] It may well be that the drag is minimal and the flow is fairly slow. Your boats have, after all, to be able to navigate in it without being helplessly swept along. You're not talking 5 knots of tide, I hope. In this case, the angle at which the pole was lying was determined by the ratio of depth of water to rope length, assuming the rope itself is as good as weightless in water and is effectively stretched in a straight line from buoy to anchor even by a very gentle flow. In this situation attaching even modest weights should be quite effective.