A leak through the log impellor hole . . .

[Nick]

.
Campbeltown lifeboat launches to leaking yacht

Keep a wooden bung or two handy . . . . I wonder what happened, if it came right out or what? (Or perhaps the skipper was trying to clear it?)

[Rowana]

I had a similar problem with Rowana when I was bringing her back from the Clyde. The original hole in the hull was 2 inches, but the log that was fitted was 42 milliwhatsits (I think). Anyway, there was a space round the log tube which had been badly filled with sealant. The fact that a bit was missing from the outer flange didn't help. Had to dry out alongside the wall in Burghead to make a temporary repair. When I eventually hauled out in Peterhead, I glassed in a bung, then cut the correct size of hole through it.

Wish I hadn't bothered re-fitting the log, as it usually stops working a few weeks after launch. I'm extermely nervous about pulling it out to clean while afloat, so I just don't bother with a log. The GPS tells me where I am anyway, and I'm never more than a few miles from the coast.

[ubergeekian]

Wish I hadn't bothered re-fitting the log, as it usually stops working a few weeks after launch. I'm extermely nervous about pulling it out to clean while afloat, so I just don't bother with a log. The GPS tells me where I am anyway, and I'm never more than a few miles from the coast.

I'm with you on that. Jumblie's impellor invariably fouls with wee mussel-y things within a few weeks of launching, and I am far too scared to pull it out. I looked at replacing it with a no-moving-parts one, but the airmar transducer would have been several hundred and the adaptor box from Tinley a couple of hundred more. Or so I think - Tinley are one of the marine industry companies which see no need to respond to customer enquiries.

Instead I use a trusty Walker Knotmaster. There's something about that whirling string I find very soothing.

[cpedw]

I have a solution to the flood when cleaning the log impeller. It's described in TOP. It's still quite a faff to fit it up but (nearly always) prevents the deluge. There must be a better way but I'm not too keen on a trailing log.

Derek

[Rowana]

When I was in the Merchant Navy many, many moons ago, there were 3 types of log that I remember. One was the trailing log that we all know, another was a mini-propeller that was pushed out through the bottom of the boat, and the flow drove the propeller - Looked a wee bit like a mini sail drive in reverse. The third type was a tube with slots in the front edge that was also pushed out through the bottom. The slots acted like a scoop, and as the speed increased, so did the pressure in the tube, which was converted to speed on the readout.

I've often wondered if I could make a "Whirlie" thing to tow behind, with a magnet/coil on the inboard end and use the same NASA readout. Save having a hole in the hull as well.

[mm5aho]

I heard a long saga on VHF last weekend, involving Campbeltown lifeboat, Belfast Coastguard and a yacht, whose name seemed familiar, and the drama involved "taking on water".
From position recorded by my radio (DSC) it sounded as if they were mid North Channel?

For us it was a bit of mystery. Hit a log? what causes a leak mid voyage?
So it was a log of a different sort!

On Logs:
We have a through hull type, and it needs cleaning about every month or so in summer, dependent on where we are. Clyde it fouls much quicker than west coast.
I pull it out, quickly replace with the bung made for the hole, and clean with a toothbrush. Reverse procedure to re-fit it. Worst I've suffered is maybe 2 buckets full of water, which reports to bilge and gets pumped out.

We have on board a range of about 6 various sized wooden tapered dowels for such emergency use as a hole. One of these would easily fot the log oriface if required.

ps, also have a trailing log and am often amused at the variance between GPS, hull log and trailing log. Its not a consistent difference, but seems to vary with wind direction. Any ideas?
In heading into the wind the trailing log reads higher than hull. In down wind situation ther opposite - trailing log reads lower and hull higher. Of course GPS is over ground, so current will always have some effect, so that difference is explicable.

[Nick]

I heard a long saga on VHF last weekend, involving Campbeltown lifeboat, Belfast Coastguard and a yacht, whose name seemed familiar, and the drama involved "taking on water".
From position recorded by my radio (DSC) it sounded as if they were mid North Channel?

For us it was a bit of mystery. Hit a log? what causes a leak mid voyage?
So it was a log of a different sort!

Sounds like the same incident.

[ubergeekian]

The third type was a tube with slots in the front edge that was also pushed out through the bottom. The slots acted like a scoop, and as the speed increased, so did the pressure in the tube, which was converted to speed on the readout.

That's a pitot tube, or variant thereof. They are very good at higher speeds, but need to be very well aligned with the flow, so I suspect the relatively large leeway angles rule them out for sailing yachts.

I've often wondered if I could make a "Whirlie" thing to tow behind, with a magnet/coil on the inboard end and use the same NASA readout. Save having a hole in the hull as well.

Is that how Stowe logs worked? There were quite a few electronic tow-behind ones at one time.

[aquaplane]

My Dad fitted a dopler log to the Westerly Windrush. The transducer was stuck on the inside of the hull and there was no hole or moving bits to worry about. I can't find a leisure one these days but I can't see my Dad forking out for an expensive industrial job. It just seemed like a good idea given that the main problems I hear about wouldn't happen.

[Rowana]

My Dad fitted a dopler log to the Westerly Windrush. The transducer was stuck on the inside of the hull and there was no hole or moving bits to worry about. I can't find a leisure one these days but I can't see my Dad forking out for an expensive industrial job. It just seemed like a good idea given that the main problems I hear about wouldn't happen.

A dopler log seems a good idea, but I wonder how accurate they would be at the relative low speeds we achieve. The NASA log works well enough when it does work, but as you say, the problem is fouling, and there is no way I'm going to put a hole in the botton of a perfictly good yacht just to clear it!

If someone came up with a safe way of withdrawing the impeller without letting water into the boat, I would definately be interested. Since this is most unlikely, it led me on to consider a "whirlie" on a string towed astern. I also considered some sort of "Propeller" thing shoved down over the side somewhere, but I think there would be problems with too much drag with this arrangement.

Sounds all too difficult, so I think I'll just ignore it as I do at present. Haven't got lost yet!

[ubergeekian]

A dopler log seems a good idea, but I wonder how accurate they would be at the relative low speeds we achieve.

I presume that's how the Airmar transducers work, but at roughly a grand to upgrade my old B&G Hornet 4 system I think I can live without it.

If someone came up with a safe way of withdrawing the impeller without letting water into the boat, I would definately be interested. Since this is most unlikely, it led me on to consider a "whirlie" on a string towed astern. I also considered some sort of "Propeller" thing shoved down over the side somewhere, but I think there would be problems with too much drag with this arrangement.

I think modern B&G systems have a flap arrangement in the tube which is supposed to reduced water ingress toa cupful or so. Hmm. Would you trust that to work?

Lucas used to make propellor-over-the-side speedometers for boats. I know, 'cos I sold one I acquired from my father on eBay last year. It looked like a very weedy outboard motor and was held to the transom by a couple of C-shaped pipe clips, the top one of which had electrical connections. I suspect that the transom is rather a bad place for that sort of thing, with the water flow too turbulent and too affected by heel.

I'll stick to my whirling string for now!

[sahona]

We've never had a problem drawing the log impellor and quickly plugging the blank filler, suitably greased. A couple of mugs-full of water and, as previously mentioned, a glimpse of the sunlit water - Isle of Capri effect.
If the ingress of a little water is a problem, and space is available, give the transducer it's own self-contained bilge by drilling a hole in a (say) plastic washbasin and fit that with an extra retaining nut over the through-hull fitting, or glass in some "walls".
I don't have any qualms about servicing the log, blakes seacocks and the shaft log packing while in the water - just be prepared for what you know is going to happen and have the remedy (greasy rags) handy.