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Author Topic: Advice pls: planked hull with hairline cracks  (Read 511 times)

colh107

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Advice pls: planked hull with hairline cracks
« on: January 30, 2020, 06:21:36 PM »

I have this planked (IOM) hull, which has a few hairline cracks. The pic shows the worst of them. Not sure if, after sanding back, I should fill it in some way or just rely on primer and paint to seal the gap. I haven't sanded back yet, obviously, so I'm not sure at the mo' if crack is only in paint or in the planking too.
If the gap extends down to the planks, what's a good filler for this - just PVA, perhaps with some 'wood dust' for bulk?
Any tips/ideas appreciated. Thanks.

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Mark T

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Re: Advice pls: planked hull with hairline cracks
« Reply #1 on: January 30, 2020, 06:54:59 PM »

Hi  - just my thoughts


It looks like the planks have expanded away from the frames which maybe either a bonding problem or a humidity issue from where its been stored.


Can you see anything inside the hull?  Have the planks moved away from the frames?


If the planks have moved I would stabilise them on the inside with some epoxy resin which should stop any further movement


I would then sand it back on the outside of the hull as the paint has cracked anyway and will need sorting out.  I would use two pack car body filler to sort out any blemishes or dips and then repaint.


I hope this helps - Mark
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colh107

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Re: Advice pls: planked hull with hairline cracks
« Reply #2 on: January 30, 2020, 07:41:26 PM »

Thanks Mark.
Hard to see that one from the inside - deck n keel box in the way. I suspect its definitely a storage/humidity issue.
I'll be getting the paint out anyway, as I need to mod for some new fittings, plus a few chips here and there.
The other cracks are a lot finer, like this.
On the plus side, one of the mods is going to be the fitting of a drain hole!  %)

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coch y bonddu

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Re: Advice pls: planked hull with hairline cracks
« Reply #3 on: January 30, 2020, 08:06:32 PM »

Obviously you can get inside to gain access to the servos ...remove them simply mix a quantity of grp resin up pour it into the hull and slosh it about so to speak,this will get into all the nooks and crannies nad help seal the hull up gaining strength.


Rub down all the paint and simply use some car body filler on the cracks....upol easy light or similar....please do not use Isopon P38 you will rue the day you did...trust mer I use filler daily and all we use are the lightest filler going ....easy to rub down and is a delight to use.




dave




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colh107

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Re: Advice pls: planked hull with hairline cracks
« Reply #4 on: February 01, 2020, 02:31:42 PM »

Looking closer, the keel crack is under the base of the mast well. Seems reasonable I guess - pressure of the mast heel.
Reluctant to put epoxy in there, for fear of ending up with an uneven surface for the heel (possibly causing it to steer/slip it off upright?). My thoughts so far: 1) put epoxy in with the hull (one side a time), canted over so it'll hopefully stay out to the edges; 2) pour epoxy in and cut a 1/32 ply piece to sit on top and retain a flat surface (but could be a good water trap if any gaps....); 3) try to get epoxy around the outside of the keel box, and rely on the added strengthening of the adjacent planks to add support to the keel-line.
I should mention, whilst I'd hope to do a decent job of it, this is a 20yr old yacht which I'm doing up as an intro to the sport. It's never going to be race-winning, but all the same I want do a reasonable job of resto/refit.

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tigertiger

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Re: Advice pls: planked hull with hairline cracks
« Reply #5 on: February 01, 2020, 03:20:01 PM »

I cannot remember where, but somewhere on here a similar topic was discussed, and a product was mentioned that is ideal to use inside a hull. From memory it is thinner, goes everywhere and it leaves a thinner coat (less weight).


I think it was mentioned in a restoration project. Anyone remember where it was?
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colh107

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Re: Advice pls: planked hull with hairline cracks
« Reply #7 on: February 08, 2020, 02:19:45 PM »

Ok, I've cut out the deck hatches (the way the design intended them), which gives me a lot more access.

The interior has already be sealed in some way - hard to tell what with. In fact, I can now see that there is the typical 1" strips of cloth from gunwhale to gunwhale, about 5" apart. Including one across the aft of the keel box, along each side of the keel box, but not across the front of the mast box.


I'm pretty much certain that that crack emanates from mast heel pressure, so I think I'll also drop (not glue) in a plate of ali or something, to spread the load around the bottom of the mast box. Perhaps pour some thinned epoxy in first to strengthen the inner base/corners of it. Seeing as the hull does look reasonably well strengthened inside, perhaps that's all it really needs.
I've got some Z-Poxy laminating resin which, it seems, can be thinned with meths?

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Mark T

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Re: Advice pls: planked hull with hairline cracks
« Reply #8 on: February 09, 2020, 09:25:59 AM »

You can thin Z-poxy I have used isopropyl alcohol to do this but you don't want to add more that about 5%.  However it does turn it cloudy and I found that it takes longer to cure.  Its quite  thin anyway so if you can use it straight I personally would.
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colh107

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Re: Advice pls: planked hull with hairline cracks
« Reply #9 on: February 09, 2020, 08:10:29 PM »

You can thin Z-poxy I have used isopropyl alcohol to do this but you don't want to add more that about 5%.  However it does turn it cloudy and I found that it takes longer to cure.  Its quite  thin anyway so if you can use it straight I personally would.


Ah-ha....  O0 Wasn't sure about that this morning with some other touch-up/try-outs. This evening I warmed the bottles in a jug of warm/hot tap water for 10 mins first though - definitely makes it much more pour-able!
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JimG

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Re: Advice pls: planked hull with hairline cracks
« Reply #10 on: February 09, 2020, 10:02:22 PM »


Ah-ha....  O0 Wasn't sure about that this morning with some other touch-up/try-outs. This evening I warmed the bottles in a jug of warm/hot tap water for 10 mins first though - definitely makes it much more pour-able!
Watch out as warming the epoxy makes it set much faster and as setting produces heat it can get very hot if allowed to form a pool in the bottom of the hull.
Jim
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