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Deck repair advice

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Created by Microbe 3 months ago, 25 Sep 2020
Microbe
WA, 91 posts
31 Oct 2020 5:09PM
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First couple of chain plates almost finished. Just a bit more cleaning up and polishing to do.

I went with 30x5 bar. This is what my rigger would have used if I'd got him to make the chain plates. Yield strength of one of these is about 2500 kgs.




Zzzzzz
484 posts
31 Oct 2020 6:22PM
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Select to expand quote
Microbe said..
First couple of chain plates almost finished. Just a bit more cleaning up and polishing to do.

I went with 30x5 bar. This is what my rigger would have used if I'd got him to make the chain plates. Yield strength of one of these is about 2500 kgs.





Looks great how did you work out the bend ?

r13
NSW, 632 posts
31 Oct 2020 9:56PM
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They looks tops.

Microbe
WA, 91 posts
1 Nov 2020 1:01PM
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Old vs new



Harb
WA, 216 posts
1 Nov 2020 8:21PM
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Select to expand quote
Microbe said..
First couple of chain plates almost finished. Just a bit more cleaning up and polishing to do.

I went with 30x5 bar. This is what my rigger would have used if I'd got him to make the chain plates. Yield strength of one of these is about 2500 kgs.





That's what I made mine from as well, reinforced with 4 more layers of glass on the inside and used 30x3mm for inside backing plates. Now they also come in handy when taking the boat off the trailer with the engine cranes.

Microbe
WA, 91 posts
7 Nov 2020 2:00PM
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Started working on the deck (the original topic of this thread!). I wanted to at least tackle the area where the new chain plates are going. I suspected there would some rot in the core so cut a section out of the top of the laminate. I was right - the ply was totally rotten.

The photo shows my initial investigation section, but I'm going to take that right out to the toe rail and about 200mm further fore and aft to take out the entire section of ply.

Once that is removed I can epoxy in a new slab of ply and replace the top layer of laminate.




Ramona
NSW, 5895 posts
7 Nov 2020 6:08PM
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I would suggest when you replace that ply that you have a raised area under the stanchion base. Something like 6 mm or so so that water will not pool at the base.

Microbe
WA, 91 posts
29 Nov 2020 2:00PM
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So, after a bit of a hiatus from boat work because of a sore back I finally managed to epoxy in the bulkheads today. For now its just thickened epoxy between mating surfaces and a bit of a fillet down the edge. Next step will be glass tape layers between bulkhead and hull.

Originally I was planning a bulkhead with timber packing either side to space out the two chainplates by the required 80mm. This would have required me to put the plates on shared 8x100mm bolts. I ended up going with a double bulkhead with a spacer in between, strongly epoxied together. This will allow me to put the plates on their own bolts and spread the load from the bulkheads out on the hull.

Note that the inside surfaces of the bulkheads had to be epoxy coated and painted with two pack paint before being bonded together. The outside will be coated and painted in situ.





r13
NSW, 632 posts
29 Nov 2020 5:55PM
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That looks excellent, it's not going anywhere.

jbarnes85
NSW, 157 posts
29 Nov 2020 6:44PM
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I need to replace a non structural bulkhead in my boat and was thinking of using this thermo-lite stuff. See link below.

if anyone has used this stuff let me know.
I may in the future also replace the main bulkhead but that is well down the road. Maybe some furniture as well.

www.diycaravans.com.au/shop/thermo-lite-tough-composite-boards/

Microbe
WA, 91 posts
30 Nov 2020 7:58PM
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jbarnes - the thermolite looks good, but I don't know much about foam cores. You might want to find another supplier though - the link you sent says a minimum order of four 1.2x2.4 sheets. They would need to be massive bulkheads to require that much material!

But whilst we are on the subject of core material I'm considering using a pvc core material to replace the rotten ply in my deck. Something like this:

compositeswarehouse.com.au/products/composite-cores/

I'm planning to cut off the top glass lamination, dig out the rotten ply and clean up the bottom layer of glass, then bed in the new core with epoxy and put the old top section back on.

What would I use to glue this sandwich together? I'm thinking epoxy thickened with glass powder. Any thoughts?

Achernar
QLD, 165 posts
1 Dec 2020 12:56PM
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jbarnes85 said..
I need to replace a non structural bulkhead in my boat and was thinking of using this thermo-lite stuff. See link below.

if anyone has used this stuff let me know.
I may in the future also replace the main bulkhead but that is well down the road. Maybe some furniture as well.

www.diycaravans.com.au/shop/thermo-lite-tough-composite-boards/


I have no experience with Thermo-Lite, but was watching the latest video from Free Range Sailing last night, and they have been using it for 6mm deck pads and the like. I think they cut theirs out of the back of an old solar panel. Its rigid stuff.

-gjjQ

PS If you live anywhere near Springfield in QLD, there will be a massive heap of damaged solar panels somewhere, following the hail storm a few weeks ago.

jbarnes85
NSW, 157 posts
1 Dec 2020 2:14PM
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Select to expand quote
Microbe said..
jbarnes - the thermolite looks good, but I don't know much about foam cores. You might want to find another supplier though - the link you sent says a minimum order of four 1.2x2.4 sheets. They would need to be massive bulkheads to require that much material!

But whilst we are on the subject of core material I'm considering using a pvc core material to replace the rotten ply in my deck. Something like this:

compositeswarehouse.com.au/products/composite-cores/

I'm planning to cut off the top glass lamination, dig out the rotten ply and clean up the bottom layer of glass, then bed in the new core with epoxy and put the old top section back on.

What would I use to glue this sandwich together? I'm thinking epoxy thickened with glass powder. Any thoughts?


You might want to test it first. The PVC might not stick with the glass. Not sure if thats a problem or not but they layers might move as the boat flexes.

you could maybe just do a whole bunch of layers of glass if it's small areas. there might be better people than me to comment

the other thing I thought about was fibreglass panels or carbon panels to use as backing plates. www.ebay.com.au/itm/324313781962

www.ebay.com.au/itm/Green-Glass-Fibre-Sheet-FR4-Epoxy-Fibreglass-Plate-Sheet-3-6mm-Thick-200-200mm-/133384127345?_trksid=p2349624.m46890.l49292



r13
NSW, 632 posts
1 Dec 2020 5:46PM
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Interesting thoughts there. To comment on Microbe's SS22 local to the chain plates deck repair only;

Imho it is far better to stay with the plywood core and glass each side lay-up as per the original. To introduce a foam core sandwich panel into this localised area for a 70s built boat with a glassed ply deck is not wise imho and won't work.

Leaving aside the glass layers each side for the moment, the ply core and foam core materials on their own have vastly different properties in bending, tensile and shear strengths, and stiffness in all these three. So placing foam core into the routed out rotted ply will immediately created strength and stiffness mismatches in all these. Even if the foam is bonded well to the underneath original polyester glass layer left in tact, with epoxy resin maybe fortified to glue strength with filler, the perimeter bond would be subject to question as regards strength of the ply edge to foam edge bond. Then the top grp laminate needs to be added to fill the void - epoxy resin based suggested - and then more laminate to create continuity with the existing polyester laminate - say at least 50mm overlap all round.

So I am not talking about the merits of foam cored deck construction versus ply with each sandwich panel having glass each side - I am only talking about repairing a 70s built ply deck with glass each side, with a foam cored insert. I would never contemplate this.

So imho suggest cut out and chase out all the rotted ply, taper it at least 4:1 from the inner glass layer to the outer upper glass layer, epoxy glue in new marine ply with the at least 4:1 taper, laminate top layer of glass fabric with epoxy resin - firstly to fill the void of the ground out initial area, then add more epoxy laminate so that the added top laminate overlaps the void in at least 2 glass pieces tapering outwards, and leaves the location where the chain plates pierce through higher than the surrounding deck so as to avoid a ponding issue as per Ramona previously. Added overlap laminate at least as thick as initial deck laminate on top of the ply.

I have used the International HT9000 epoxy resin and associated fillers for many similar laminating and gluing projects in the past and can recommend it.

Microbe
WA, 91 posts
1 Dec 2020 9:06PM
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Thanks for the suggestions. I had been thinking about PVC core to remove the chance of rot in the future, but hadn't considered the difference in strength and flexibility. Marine ply will be cheaper and easier to find, so I'm happy to use that.


The deck is only partially cored. The core was added as reinforcement in high load areas. There is a section the full width of the deck around the chainplates and a thinner section running fore and aft from there. I will remove the whole chainplate section core ply (about 300x700) and replace with new ply. I'll feel happier knowing I've definitely got out all the rot and solved delamination issues.

Having done this there will be no need to taper or scarfe the new ply in to the old, so no edge bonding issues.

Thanks for your detailed reply r13, I like the idea of building up a new top laminate rather than reusing the old. More work, but a better repair.

Ramona
NSW, 5895 posts
2 Dec 2020 9:00AM
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Pvc core rots just as much as ply if water gets in. Probably worst as the core takes up water the pvc gets soggy!.

r13
NSW, 632 posts
2 Dec 2020 6:55PM
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Thanks Microbe.

As regards pvc core rotting - there are many types of pvc core materials and just as with end grain balsa cores the lamination of the inner and outer skins to the core is the key........effusive article here spruiking end grain balsa

www.yachtsurvey.com/core_materials.htm

and a forum here

forums.sailinganarchy.com/index.php?/topic/155138-longevity-of-foam-cores/

Divinycell if done well during the initial build, and not tampered with after, is a top shelf core.

blog-fgci.com/tag/divinycell/

Gurit work in all cores;

www.gurit.com/Our-Business/Industries--Markets/Marine/Case-studies






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"Deck repair advice" started by Microbe