Why is it so expensive to replace a keel-band?

dancrane said:
Hmm...Rob, try to imagine you're landing your Wayfarer, singlehanded, arriving on a fairly steep concrete slipway where there's a dependable, brisk onshore breeze...

...now, between jumping out, going to find your trolley, returning and wrestling the boat onto its wheels, how often would you reckon to get her up without running her hard ashore?
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Maybe your location is more exposed etc, but certainly when I borrow SWMBO's 50yr old plywood Graduate I am not allowed to bump into anything! Just a case of fending off manually. Swing the boat broadside to the shore so you drift the last wee bit, jump out, get your feet wet but so what. Tie the painter to a big stone or whatever and give the boat a good shove back out while you run for the trolley. Yes, it's much easier in an offshore breeze...
 
Mavanier said:
Tie the painter to a big stone or whatever and give the boat a good shove back out while you run for the trolley. Yes, it's much easier in an offshore breeze...
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That sounds idyllically easy! But if I jump out of my boat even three yards from the water's edge, it's not just my feet getting wet, it'd be up to my shorts...and if I was to leave her sideways-on in the onshore breeze, she'd come crashing in self-destructively, sooner than I could get the wheels.

And honestly, there isn't a big stone, or a ring, or a post or anything to secure the boat to...though that's separate issue. I'm thinking I'll get one of those big inflatable boat-rollers to lift the bow onto, so incoming waves won't shove her hard into concrete, though the steepness of the slipway risks her rolling back...

...so I'd be crazily optimistic to imagine she doesn't need a decent bit of keel-line reinforcement. I suppose the simple fact of manoeuvring a rather big dinghy singlehanded, puts her at greater risk than if another human was always there to fend off.

It needn't be a big deal as long as I can fit a tough-enough replacement for my existing 3/8" band, now falling off in chunks. But I believe I can't afford to make a sloppy job of it.
 
Try a little experiment. Find yourself a bit of sheet aluminium, maybe a strip of the stuff you intend to use. Mix a bit of Araldite on it and let it go hard. Now bend the aluminium a little. I will bet you a virtual pint that the Araldite will not remain stuck to it. If you applied some sort of surface roughening to the aluminium, by mechanical or chemical means, you might find an improvement, but I doubt very much that it would be enough to survive grounding on a concrete slipway.

You might find something more effective here but I imagine it might be a lot more expensive and less effective than half a dozen screws. http://ctaltd.co.uk/aluminium-adhesive/
 
alahol2 said:
Have you got room to fix this stuff on?
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Thanks for that, Alahol - I'm not sure - at 25mm wide, it looks a bit beamy for the narrow join between my bottom sections, although plastic elasticity sounds appealingly durable.

Thanks Vyv, too. I realise that a bit of metal secured (however well or badly) to the keel of a very untidy old boat, is pretty low amongst anyone's priorities or interests.

Thinking about it though, (and looking at the snapped old section) I wonder just what this very rigid metal is meant to do - is it just for preventing abrasion of the keel-line, or should it spread the impact of a sudden knock? Both, perhaps?

I reckon several heavy impacts have deformed mine, then finally snapped it...so I'm keen to replace it with something which will absorb & diminish the effect of (hopefully rare) sharp thuds, instead of simply snapping and dropping away in segments between screw-holes, leaving the GRP wide open to scrapes.

I expect I'll use the Classic Marine 1/2" brass with the two-dozen bronze screws they recommend, and possibly Araladite as well. The trouble with my old keelband seems to have been how very loose whole sections became, once a single screw was snapped or shifted. If it's secured with glue too, it may endure better. Thanks!
 
vyv_cox said:
Try a little experiment. Find yourself a bit of sheet aluminium, maybe a strip of the stuff you intend to use. Mix a bit of Araldite on it and let it go hard. Now bend the aluminium a little. I will bet you a virtual pint that the Araldite will not remain stuck to it. If you applied some sort of surface roughening to the aluminium, by mechanical or chemical means, you might find an improvement, but I doubt very much that it would be enough to survive grounding on a concrete slipway.

You might find something more effective here but I imagine it might be a lot more expensive and less effective than half a dozen screws. http://ctaltd.co.uk/aluminium-adhesive/
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Funny how it's worked fine for me for 10 years on the present tender doing exactly that and years more on previous ones then. :rolleyes:

Preparation is the key.
 
I'm thinking belt & braces. The 1/2" brass D-section from Classic Marine is 1/4 the price of something similar from Pinnell & Bax...but it comes drilled, so I may as well use screws...

...meanwhile, if the band is strongly glued, there'll surely be less tendency for localised impacts to break it, or to loosen a screw (which is why the existing band has collapsed)...

...so, it makes sense to glue it too, as far as I can see.

I don't have a photo to indicate the present problem in close-up, so it's hard to show why I've been hoping for an improvement. The 3/8" keel-band seems to me to need holes that are really too big for the gauge, making numerous inherent weaknesses in the band, which become catastrophic when any screw is broken or wrenched out - a whole section goes floppy. Just accepting this weakness and replacing it with the same again, isn't good enough! I'll hope to be able to show a photo here, of a tougher, more permanent solution.

View attachment 39930

Can't believe how dirty the hull gets...looks like tyre-marks, but my trolley's padded with orange foam. They don't scrub off...so, please...which rubbing-compound is recommended?
 
Well, it's finally arrived, at least. The delay wasn't Classic Marine's fault - they'd tried emailing me, but their messages had gone straight into my junk file. No idea why.

View attachment 40492

Keen readers of this thread (he joked) will have noticed that I ordered the keel-band undrilled, in order to prevent it weakening at the drill-holes when coiled for postage...

...plus, the 30 minutes of labour (which it was estimated would be required to put 25 countersunk holes in the band) would have added £25 to the £20 cost. So, it'll be a DIY job.

I'm expecting it'll be impossible to line up the yet-to-be-drilled holes on the new band, with the existing screw-holes in the boat's keel line...much easier to fill the old holes on the hull and drill new ones through the gelcoat to match the positions of holes I will have put in the keel-band.

I can see that some roughening of the gelcoat will be needed to help the glue to key, but is the same roughening required on the metal too? It's beautifully smooth at present.
 
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Dan,

yes I'd use something like a wire brush attachment in a drill to rough up the inside surface of the metal to give a key.

It will still be smooth on the outside to aid the pressure wave going past as you go transonic...:)
 
The most useful ( ? ) thing apart from self bailers I ever put on the bottom of racing dinghies - Scorpion and Osprey - was ' DON'T PANIC ' in large friendly letters as in HitchHikers' Guide...

When we did a capsize test a git ran down the slip and took a photo of the boat on her side wording exposed, didn't stop to ask if we were OK, could have been drowning; I might put a naughty instruction as to where to put the lens if I have another capsizeable boat...:rolleyes:
 
Seajet said:
I might put a naughty instruction as to where to put the lens if I have another capsizeable boat...:rolleyes:
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:D That's a nice idea. Although, as we all know, I don't really do capsizing...yet. :o Maybe sometime after sea-temperatures reach double figures... :rolleyes:
 
I think you may have nailed it (f'nah, f'nah...spell?). I've often seen keel bands coming apart and there are several mechanisms at work. Firstly the screws tend to rot faster than the band, so they can lose their heads, leaving the band to float sideways unsupported. As the screw holes in the band weaken the section and it is likely to have embrittled over the years of service, any sideways element in the movement of the boat on the slipway will snap out a section between screw holes.

By screwing and bedding it, it should prevent movement and therefore snapping of the band, just check the condition of the screws from time to time. Incidentally, one of the reasons that a boatbuilder will prefer the band to be delivered undrilled is so that he can position the screws to minimise such problems in the first place. In particular, you don't want screw holes on the tighest curve of the forefoot, but you definitely want them at the very ends of the band. Best to measure up the screw positions and drill them in the shed on a drill press. I just wonder whether one should use epoxy for the bedding or a more flexible glue to absorb shocks. Don't forget to put some of whatever you're using into the screw holes to waterproof the mounting screws... Grandma, eggs?

Rob.
 
All good points, thanks Rob, though I tend to doubt that a really usefully tough adhesive will also offer shock-absorbing flexibility.

Here's a little laugh...my only drill is an old, hand-powered thing. Not as daft as it seems - I worked a 16mm bit through an inch of GRP/hardwood last year, for the rowlock-sockets...

...and it never runs out of power (though eventually my worn fingers ran low on effort). But even though I'll attempt the keel-band job with it, I think it's time to buy a cordless.
 
That strip does seem like good value.

I wish I could find a cheap bench-drill. Entry-level seems to be about £65, for no great quality. Though I've nowhere dry to keep it. And I'm likely to have numerous uses for a cordless as time goes by.

I was thinking of using a very narrow bit to drill initial holes, which needn't be too destructive if their position isn't quite right...then drill the holes out with bigger bits. Good plan?
 
The bigger drill bit will just centre itself on the initial hole. But yes it could minimise the cock-up-edness of a misplaced hole by not weakening the band too much.
 
While looking for this thread using Google, I was sidelined onto another, quite different site, which then referred back here! Should I be flattered? :rolleyes: It's here: http://ow.ly/unXt8

I managed to drill a perfect, beautifully-centred 3mm practice hole through one of the broken bits of 3/8" keel-band, using my antique hand-drill! I was feeling pleased with myself when it occurred to me that if I'd used a narrower, 2.5mm bit, there'd have been more breadth of band remaining either side of the hole, and more strength left in it accordingly...

...so, how narrow a screw is OK, before insufficient screw-strength (or lack of the screw's thread-depth) becomes a compromising issue in the keel-band's attachment to the hull?
 
Finally drilled the holes yesterday, at neat 4-inch intervals as recommended...first I used a 2.5mm bit, then bored the holes out with a 3mm...then countersunk with a bigger bit.

All done with the hand-drill, and in comparison with the old band, I reckon I've done a better-centred job. I made smaller holes too (the old band had been drilled with a 4mm bit, bigger than necessary) hopefully leaving more metal and strength behind.

Many of the screws which came out, aren't in good condition for reuse. Do I need screws in a certain metal to avoid electrolytic corrosion...or is it another job for Duralac?

The GRP of the keel-line is in pretty awful condition - dings & dents, bits of cracked & broken gelcoat, plus lumps of some earlier hard filler or glue preventing the new band lying flat. So, a bit of work before I can photo the new band gleaming in situ.

The surrounding hull is filthy and rougher than can be good for performance...anybody recommend a particular rubbing compound? I took a long look at the Farecla website and couldn't judge how deep a scour I need to remove black tyre marks and the yellowing of age as well as the outline of her old name stickers.

Post Script: I finally found a use for the old broken bits of keel-band...reinforcing the tips of the centreboard and rudder: :)

20140816_185549_zps58d02417.jpg
 
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