The right stuff?

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Jonathan Theobald
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The right stuff?

Post by Jonathan Theobald » Wed Apr 23, 2003 10:50 am

Over Easter I managed to leave a bit of gel coat on an Anglesey rock, and now I need to patch up my boat.

It's not a job I've done before so I'm after advice on repair basics - right tools, right materials, where to get them, and the right way of putting the stuff on.

The hull is white, and the damaged section is less than six inches by two. The glass matting doesn't seem to have suffered.

Tareverso.





Mike B
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Scratch repair

Post by Mike B » Wed Apr 23, 2003 12:42 pm

Oh dear. Plastic Padding make a "Gelcoat Filler" which is ideal for filling small scratches.

Knoydart do it. Or a chandlers will have it. Its white, but could be colored as necessary.

Mix. Apply with applicator stick as supplied. Leave. Sand if necessary. Job done. Used it with good results on the Quest.

You could also make up some gelcoat obtained from your local fiberglass stockist ("Strandglass", if they still exist)and use it. Cover the freshly applied gel with something like packing tape for a nice smooth finish.

Hih - Mike.


Mike B
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Scratches

Post by Mike B » Wed Apr 23, 2003 12:48 pm

Sorry - its Loctite 3024 Gel Coat Filler you want. Not made by "Plastic Padding".

Jonathan Theobald
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Re: Scratches

Post by Jonathan Theobald » Wed Apr 23, 2003 1:54 pm

Tar for that, Mike.

I'm feeling better already.

Mike B
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Scratches

Post by Mike B » Wed Apr 23, 2003 3:18 pm

Glas to help - but, the stuff IS made by Plastic Padding! Now that I've actually checked the box, it says it s a Plastic Padding product, using Locktite technology. :rolleyes

(Thought I'd better get the details right before the pedants get on the case)

:b

Jonathan Theobald
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Re: Scratches

Post by Jonathan Theobald » Wed Apr 23, 2003 7:13 pm

Very reassuring to know postings to this forum are refereed with the rigour of a scientific journal. Keeps us all on our toes.

I'm hoping to keep on the right side of the pedants, too.


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MatSav
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New Rapid?

Post by MatSav » Thu Apr 24, 2003 10:38 am

"I'm hoping to keep on the right side of the pedants, too."

Shouldn't that be "I'm hoping to keep to starboard of the pedants"? So, where are The Pedants? are they anywhere near The Bitches? ;)

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Jim
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Method

Post by Jim » Sat Apr 26, 2003 3:36 pm

Take some fairly coarse wet and dry, perhaps P400 (i.e. finer than glasspaper) fold it into a small square or rectangle and abrade your damaged area. What you want to acheive, apart from a mechanical bond, is to taper (or feather edge) the existing gel in the immediate vicinity of the rapair slightly. Keep the abraded area small and close in to the repair. Apply the gelcoat filler sparingly - you won't get it flush (if only we could) but you want the asolute minimum amount proud - a recessed repair won't polish up well and will need to be redone.

When set take your P400 on a very small block of wood and abrade the proud part back almost flush keeping the direction of abrasion the same - making short backward and forward strokes. At this stage if the repair is too proud the block will rock and you will sand the edges of the repair away but not the lump in the middle, it takes practice! Next take some finer paper, P800, and do the same thing at 90 degrees to your scratch marks (so up and down in this case). When the 400 scratches have been replaced by 800 scratches change to P1000 and do it in the first direction. Basically move down through as many grades as you can find, each time the scratches become less noticeable - but go lightly or you may find you've taken too much off around the outside and you can see the matting at the edge of your repair. Usually the finest grade of wet and dry available is P1600, sometimes just called "superfine". After this the perfectionist can move on to Farecla polishing pastes or T-cut to get a lovely shiny job, but it's going to stand out against the rest of the boat at this stage!

Of course with my boat making like a sieve last Saturday I was forced into an interesting position, I sanded the areas to be fixed with a rough rock (sandpaper and wet & dry in the car...), applyed some epoxy and glass tape to the split and then dabbed epoxy in all the gel chips that may have been leaking (it's probably my new deck fittings), forget nice neat repairs I had 6 days to go and was sinking fast! My boat seems to need some TLC and dirty great patches!

JIM

Jonathan Theobald
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Leak detecting

Post by Jonathan Theobald » Fri Jun 20, 2003 4:17 pm

As if ripping my Chillcheater pants weren't enough, I've also put a hole in my grp Valley boat. After only an hour of paddling last night, the forward compartment had half a gallon sloshing about. The same thing happened again after I emptied the kayak and checked the hatch was properly on.

Trouble is there's no obvious crack or sign of damage. So I'm wondering about the most effective way to leak-detect. I could fill the whole compartment with water, but I suspect the result is simply going to be a wet hull without my being able to tell just where it's coming from.

Is there a better way?

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Douglas Wilcox
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leaks

Post by Douglas Wilcox » Fri Jun 20, 2003 4:39 pm

Old hatch cover,
old bike inner tube OR
Car tyre valve
rubber cement from bike repair kit
bowl
water
Squezy
Can of beer

If you can get hold of or have an old hatch cover, put a hole in it and push an old bike inner tube valve through from the inside, you can glue the remaining bit of innertube to the back of the cover. alternatvely you can get hold of a new car tyre valve and shove it through.

Block off any bulkhead bleed hole.

Pump a bit of air into your compartment,

Go all over the outside of the compartment with a paint brush loaded with dilute detergent solution.

Find string of bubbles.

pour a well deserved beer.

Douglas :)

Jonathan Theobald
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Re: leaks

Post by Jonathan Theobald » Fri Jun 20, 2003 4:54 pm

Beer sounds good.

But not so sure about sacrificing a perfectly good hatch. Is there any other way?

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MikeB
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Onions

Post by MikeB » Fri Jun 20, 2003 5:21 pm

You could try witing till its dark (or doing this in a dark place) and put a torch into the compartment to see if there are any obvious chinks of light shining thro.

Valley boats dont usually leak - is your forward bulkhead letting in water from the cockpit? Seems a lot of water to get in of course.

I'd go for the water test - leave it in the sun and its dry nicely once you've emptied.

Let us know what the problem is.

Best of luck - Mike.

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Douglas Wilcox
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leak

Post by Douglas Wilcox » Fri Jun 20, 2003 5:24 pm

Once you remove the valve, the hole will be very small (assuming its a rubber cover), just stick a bit of old inner tube inside over the hole, good as new!!

Alternatively drive to the factory that made the boat, they will almost certainly use this system for testing new boats. They might even be able to hire/lend/send a hatch cover through the post.
Douglas

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sub5rider
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Re: leak

Post by sub5rider » Fri Jun 20, 2003 7:13 pm

You _may_ be able to pressurise a compartment without damaging a hatch cover. Might be worth a try first....

A bike innertube still needs to be sacrificed.

Cut the tube in half opposite the valve. Roll on end up till it's 3-4" from the valve. Put a couple of zip ties round it to stop it unrolling. Romove hatch cover, dangle open end of innertube in hatch & replace hatch cover (trapping tube twixt hatch & deck) with minimum distance between valve & hatch. Attach compressor & stand back in case it goes BANG!
Nigel, aka Sub5Rider, Onioneer

Jonathan Theobald
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Re: leak

Post by Jonathan Theobald » Mon Jul 07, 2003 10:55 am

Wasn't absolutely sure whether my "leak" was due to incompetence and my failing to get the front hatch on properly. But after the front compartment of my Aquila was shipping water on Sunday morning I finally got round to leak detecting.

I couldn't bring myself to poke holes in the hatch cover so I started by standing the boat on its bow, with the stern in the crook of a branch, and half filling the cockpit. Result - a tiny trickle into the front compartment, but not enough to matter.

Then I laid the boat on the lawn, half-filled the front compartment, and rolled the boat upside. The effect was impressive - not a single drop leaked from the hatch.

Finally, I found the damage. A spot on the keel had its gel coat cracked. After I picked off a loose square inch, water poured through.

That surprised me. I hadn't realised so much waterproofing was done by just two or three mm of gel coat.

Or perhaps I have that wrong? Could fibreglass matting letting water through be a sign the matting is damaged?

What I'm wondering is this - will I be okay just repairing the damaged gel coat? Or do I need to do something more fundamental? And if so, what might it be?

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Jim
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Re: leak

Post by Jim » Mon Jul 07, 2003 12:50 pm

"That surprised me. I hadn't realised so much waterproofing was done by just two or three mm of gel coat."

Waterproofing isn't the job of the gelcoat, it is purely for decoration. It is reasonably waterproof, although water can pass through it by osmosis it doesn't do it in the sort of quantities that would constitute a leak!

"Or perhaps I have that wrong? Could fibreglass matting letting water through be a sign the matting is damaged?"

Definitely!
What has most likely happened is that you haven't been quite as gentle as you thought at some time and have crunched the forward end on a rock. The laminate below the gelcoat must have given a bit and cracked. Now you might not be able to obviously see a crack, the layers may have cracked at different spots and delaminated between thus disguising the 'hole'. You could chip away at the gelcoat some more and try and identify the crack, but you might peel the whole boat and still not be able to see it, so I don't advise this!

"What I'm wondering is this - will I be okay just repairing the damaged gel coat? Or do I need to do something more fundamental? And if so, what might it be?"

Gelcoat is non structural. Just repairing the gelcoat and hoping the leak will go away won't work because the gel will keep cracking off in that location. Clearly you don't want a massive patch on the outside of your hull so I would suggest the following procedure unless anyone has a better idea:

> Locate the area on the inside of the compartment in line with the gelcoat hole. See if there is any internal evidence of a crack or split in the laminate here.

> Dry the compartment - a fan heater will do it, but will keep cutting out because the temperature inside rises quite quickly, maybe combine with a desk fan?

> Abrade the inside quite well. This is doubly important if you have an epoxy boat. I would use P60 or even P40 by hand to key the surface up well. You really want to abrade an area at least an inch bigger all round than the area you have identified (or are guessing) is damaged. If you are going to put on a fe layers make it an inch all round per layer - 3 layers would probably be sensible.

> Get hold of some glassfibre cloth (or tape if you can't get cloth) and cut squares or rectangles to fit your patch. The first layer will be about an inch bigger than the hole, the second and inch bigger than the first, and the third an inch bigger again - this way you 'feather' the repair and don't get such an obvious step in the inside of the boat. Please don't use chopped strand mat, it's awful to work with and will probably leave spiky bits to puncture your dry bags!

> For resin I recommend epoxy, it's more waterproof than polyester and thinner so it will hopefully seep into the invisible cracks and make a thorough repair.

> Coat the outside with a little epoxy, when set abrade and then do the gel repair!

> When the inside is hard you will probably want to flat it back as much as possible and overcoat with epoxy to make the surface smooth and non-dry bag puncturing!

Good luck, it sounds more complicated than it is!

JIM

Jonathan Theobald
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Re: leak

Post by Jonathan Theobald » Mon Jul 07, 2003 2:57 pm

A model of clarity, detail and good sense which I'm about to print out so it's in front of me for when I do the repair.

Tar ever so.


Jonathan Theobald
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Quick question...

Post by Jonathan Theobald » Fri Jul 11, 2003 12:29 am

Where's a good place to buy epoxy resin?

The nearest chandler only sells it by the litre but that is - I hope - far more than I'm going to need.

I tried Halfords, too, but the resin packaging they carry says nothing about its being epoxy. Ditto Knoydart.




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Douglas Wilcox
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The right stuff

Post by Douglas Wilcox » Fri Jul 11, 2003 8:40 am

The kit you want is West systems handy repair kit product number 101. I got mine several years ago for about 7 pounds.

We need to use it for repairing epoxy windsurfers as the polyester resin available in Halfords dissolves the white foam core. I got mine in a windsurfing shop but as epoxy manufacture of windsurfers has improved they need less major repairs and I think most windsurfing retailers now just sell 2 part epoxy putty like Dingstick.

try these places:

Marinac Yacht Fittings, Ltd
24-26 Boswell Square
Hillington Indust'l Estate
Glasgow G52 4BQ
Tel: 01418-838723
Fax: 01418-834638

Marine & Indust'l Sealants
Keepers Cove, Westwick Hill
North Walsham, Norfolk
Tel: 01692-538263
Fax: 01692-538692

Robbins Timber
Units 12-18 Brookgate
Ashton Vale Trading Estate
Bristol BS3 2UN
Tel: 0117 963 3136
Fax: 0117 963 7927

Simpson-Lawrence Ltd
218/228 Edmiston Dr
Glasgow G51 2YT
Tel: 01414-300 9100
Fax: 01414-275419

Simpson-Lawrence Ltd
Unit G, Fort Wallington
Fareham, Hampshire PO15 8TT
Tel: 01329-823300
Fax: 01329-823282

Sowester
Stingsford Rd, Nuffield Industrial Estate
Poole, Dorset BH17 OSW
Tel: 01202 667700
Fax: 01202 668585

Wessex Resins & Adhesives Ltd.
Cupernham House, Cupernham Lane
Romsey, Hampshire SO51 7LF
Tel: +44 (0)1794-521111
Fax: +44 (0)1794-517779
Email: information@wessex-resins.com

If you cant be bothered, polyester resin will work just fine.

Douglas

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sub5rider
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Re: The right stuff

Post by sub5rider » Fri Jul 11, 2003 11:07 am

Or a decent model shop will sell it small quantities. You dont want a lot, it has a shelf life. I used to use SP113 laminating resin a lot...
Nigel, aka Sub5Rider, Onioneer

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Jim
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Re: The right stuff

Post by Jim » Fri Jul 11, 2003 2:20 pm

I much prefer SP resin over wessex (thinner to start with, you can add stuff to thicked it if you want). Try their website: www.spsystems.com it's a bit commercial though.
Wessex are: www.wessex-resins.com

There seems to be a load of small epoxy suppliers now, just looking through a boatbuilding magazine I have found a few more (no experience of their products):

www.sicomin.co.uk (Sicomin)
www.epoxy-resins.co.uk (UK Epoxy Resins)
www.yachtpaint.com (Epiliux)

These others only have e-mail:
blue.gee@virgin.net (Blue gee)
connexiontechnology@blueyonder.co.uk (Connexion)
peterjchinawind@aol.com (MAS)

The stuff sold for car body repair is polyester resin - it has it's place but epoxy is better for repairs as it's thinner. Make sure you mix epoxy resins fairly accurately to ensure they set, adding more hardener won't speed up the process like it does with polyester, it will leave you with patches that don't go off at all!

JIM

Jonathan Theobald
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Re: The right stuff

Post by Jonathan Theobald » Tue Jul 15, 2003 10:46 am

I've finally managed to track down expoxy resin in a sensible size and should have it this weekend. The chandlers who do Wessex and SP Systems agreed with your preference, Jim, so an SP Systems 375mm handypack is what I've ordered.

One thing I forgot to ask is about fillers. Both manufacturers offer them as options - is that something I actually need for what should be a minor repair?

Thanks for the friendly advice.

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Jim
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Re: The right stuff

Post by Jim » Tue Jul 15, 2003 5:23 pm

The fillers are only really required for more specialised jobs like bonding and filleting, or indeed if you want to fill gaps. This _shouldn't_ be relevant for your repair!

As a general guide:
> Colloidal silica - thickens the epoxy fairly cheaply but is a bit rough and not very strong compared to some of the other options. Clear/milky white.
> Microballoons (AKA Q-cell) - high strength filler, good for filleting along bulkhead joints for example, Quite expensive, very smooth when set. Normally reddish brown in colour for DIY, we used to use white stuff in the boatyard.
> Microfibres - Reasonable strength, very coarse, thickens the paste very quickly and enables you to make a paste that will stand up on it's own (much better than whipped cream).

Now microballoons are quite expensive, so it is common to mix the different fillers together to get more specific fillers. A mix of silica and microballoons will make a great filleting or filling paste that sets nice and smooth without using too much of the expensive microballoons (you can by these ready mixed sometimes). A mix of microballoons and microfibres will give you a very stiff and mechanically strong paste which is ideal for bonding decks to hulls, most importantly it will stay where you put it on vertical faces until you are ready to squeeze the parts together! to mix microballoons to that thickness on their own would be expensive, and the resulting paste would be unstirrable before it actually got to that thickness - it's kind of wierd to describe!
A filler based on microfibres would be good for filling largish gaps.
I use silica on it's own (well with epoxy) for general gluing and filleting where I can get to it to sand easily, but once you get too much silica in it becomes sort of lumpy and awkward to work.

Final tip when using fillers/bonding pastes - wet the areas to be bonded with plain resin first, then the filler sticks to the wet bit quite nicely and won't keep falling off. I generally use the resin I'm about to mix the fillers into...

JIM


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MikeB
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Repairs

Post by MikeB » Tue Jul 15, 2003 10:07 pm

For what its worth in this increasingly technical debate, we did a lot of repair work to our original fleet of Scout boats using glass fibre - we used a powder mixed with resin (and colorant) for thickening side seams.

Repairs were usually resin and glass mat or cloth, depending on "what and where".

Where we were dealing with an actual hole, the technique we used very succesfully was to cut out the damaged area (cracks were cleared with a round file so as to provide a round, stress free "end") and we then used packing tape to cover the hole, applied on the outside.

Then, working from inside, we applied a gel coat (usually colored as appropriate) - once the gel had set we then applied two or three build-up layers of cloth and resin inside.

Left the lot overnight and then removed the packing tape which left a reasonably nice smooth finish. IIRC gel needs to be kept away from air if its to set properly on what becomes the outside. Appropriate use of suitably fine wet-n-dry then produced a good overall finish.

Some of those repairs are now ten years old and still perfect.

One boat had its entire fore-deck reconstructed using this technique and we produced an excellent result with it.

Mike.

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Jim
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Re: Repairs

Post by Jim » Tue Jul 15, 2003 11:51 pm

Good description of laying a boat up with polyester Mike! Seems a bit OTT for a repair, but the longevity seems to have proved itself :-)

A couple of technical points for anyone still following:

Like Mike said, ordinary polyester gelcoat does need an absence of air to set hard. I have also used the tape method on gel repairs using proper gel coat in the past, however there are a couple of ways around it:

a) Use gel coat filler, which is designed to set.
b) Add a small amout of liquid wax to the gel (was it 2% or less?) - it will float to the surface and form an air excluding coat. In fact, it's probably the secret ingredient in the filler :-)

Another thing to note if mixing a polyester gel and epoxy laminating resin is that the 2 do not combine very well, unless you do a couple of things:

For a gel coat repair over epoxy, abrade the epoxy to key it up - epoxy exudes it's own waxy coating to which nothing sticks (causing many slalom boaters to think their boats were unrepairable for a while...), abrading will remove it and allow for mechanical bonding.

For laminating epoxy over polyester gel we used to use a pre-gel. I think this was more to help prevent the cloth weave causing a print on the gel than for chemical bonding reasons, but it is certainly easier to work over a layer of epoxy thickened a little with silica.

Gel coat is a cheap easy way to a nice finish. If you don't use a gel coat a thickened epoxy layer is useful against the mould (for that cloth weave, and for working on). The major advantage or disadvantage is that you can inspect the finished product for voids, or air bubbles under the laminates because you can see both sides :-) If you don't want an off white or black or black and yellow boat (glass or carbon or carbon and kevlar), you could spray paint it, and still be lighter than an equivalent boat with a gel coat!

I digress considerably now....

JIM

Jonathan Theobald
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Re: Repairs

Post by Jonathan Theobald » Mon Jul 28, 2003 12:40 pm

I used SP Systems epoxy handypack to put three layers of glass matting over the damage as per instructions.

And you were quite right, Jim - the job was straightforward and the results were gratifyingly neat and effective. On Sunday I took the boat out and brought it back with front compartment bone dry.

The one thing that leaves me unimpressed is the Loctite gel coat. When first I tried it a month or so ago, the finish stayed so sticky I thought I must have mixed in the wrong amount of hardener. But a lad in the same club as me who built his own kayak tells me he had the same problem.

My local rowing club has boats that always look shiny and well maintained so perhaps I'll wonder along and see if they have the magic ingredient I can use to pretty up the outside of my hull. It sounds as though I only need a couple of drops of wax additive.

It occurs to me I've been lucky having to repair a hole that's easily accessible through a hatch. Had the spot been at the far end of bow or stern, or under the seat the experience might have been more frustrating.

The damage probably occurred when I dropped the boat while trying to get it off the car on my own. Another lesson.


Jonathan Theobald
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Almost forgot ...

Post by Jonathan Theobald » Mon Jul 28, 2003 2:08 pm

... thanks for all the good and helpful advice, which made for a constructive weekend and was much appreciated.

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Jim
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Re: Almost forgot ...

Post by Jim » Mon Jul 28, 2003 6:35 pm

That's alright!

I like to explain these things to people, if nothing else so they can repair their own boats with confidence (especially useful if you're in mid expedition when you find a hole). There is a danger of some of these skills getting forgotten as the majority have moved right away from fibreglass boats. And then there were the dark ages of fibreglass where all boats were repaired by applying loads of chopped strand mat bought from an autofactors, or I heard of one case where someone patched a mirror dinghy using rockwool as the reinforcement!

My dads scouts had a power boat for a while which needed some work doing on the floor or hull (memory is fading a bit- I think the floor had come away from the hull). They had been puzzling how to repair it without making a mess (my dad had machined new parts for steering linkages and overhauled the outboard, but the structural bit was beyond their experience), I had a look, told dad what to get and then helped him and the scout leader to do the job so they would know what to do another time - turned out to be pretty simple once you know how! We were tearing around Loch Nevis in the boat the following week.

JIM

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