Epoxy adhesives

lesweeks

lesweeks

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I'm pretty sure that I'm going to cover the tongue and grooved, softwood, deck of my 1912 yawl with a layer of 6mm marine ply before adding a deck covering of some sort. The thinking is that it'll hold the planking firmly laterally and stop any vertical movement that might lead to a breakdown/split/crack etc. in the covering. I'm led to believe that epoxy adhesives are best for this type of job as there is a greater penetration into the wood thereby forming a stronger bond between the two layers. Am I correct? Does anyone have any experience in this or have a brand/type to recommend?
p.s. I am NOT going to glass over the top afterwards. It'll either be canvas or something like a TBS non-slip covering.
 
This seems like a risky step. Epoxy is quite brittle unless reinforced with (say) glass cloth, and unless heavily loaded with filler would not gap fill enough to prevent water getting into the void, rotting the deck very fast.
The trad method would have been to lute the faying surfaces with a lead paint / putty mix over calico but this is now considered hazardous!
I'd look at some kind of trowel-on soft compound - maybe Sika do something. followed by bronze ring-nails into the old deck every 6" or so
Canvas is the right thing though, bedded in paint.
 
I would agree - epoxy is too hard for a softwood deck. The original deck needs to be able to move, not only with boat working at sea but with varying moisture content, and epoxy will not allow it to do that.

Sikaflex type compound sounds ideal, but just hope you never want to get it off again - it wont let go!
 
Agree, not a good idea. You will end up with a stiff deck with everything else moving around, leading to leaks around the joints with the rest of the structure such as around the cabin and at the gunnels. Fresh water would lead to rot.
 
Sorry guys/girls, have to disagree!
`Yes you have to fit a ply interface between the T&G, and you really really must sheath it with epoxy and 200 to 300 glass cloth. Steer clear of canvas sheathing as you will be re-doing it again in a few years, and that will be after you have repaired your soggy ply.
You will paint your deckhead underneath well, won't you, and the epoxy or polyurethene gluewill seal it well from above, so in reality it won't move a bit. I have done over 25 decks this way, the first being over 20 yrs ago, and all still good as new.Three, in fact, since last Nov.
I am about to sheath a canvas covered deck in epoxy where it has failed after only 7 years. That means all deck fittings, toerails, rubrails etc off to do a proper job. Canvas was a waste of time and effort.

You can use Sika under the ply but it is overkill, expensive, and can stop the ply from pulling down fair. If you get the ply fair, and the sheathing down neatly, no fill/fairing or sanding is required. Squeegy of all excess resin,and just as the epoxy is going of, coat with 2 pack undercoat (SP Hi-build, Perfection 709 U/Coat) and no sanding is required. Not only does \this make for a quick job, but you will be able to see the weave of the cloth for that canvas look.
Just adding the ply will give you a stiffer deck. Whatever glue you use wont make any difference. I usually mechanically fasten the ply with s/s pks or bronze gripfast as well.
Depending on how hard you push your boat, you may notice that the lower seam of your shearstrake may become more active. However, your cabin structure and lodging knees will heave a sigh of relief as the ply will reduce racking of the hull when sailing in a breeze.
For most of you boats life, it is unlikely that she worked or moved at all. New wooden boats are a stiff monocoque structure. Any movement shows in digonal fractures on topside paint seams. If you dont have these, your boats structure is still as good as new!
Must go and play with my 3 day old baby !
Hope this rant helps !!

Oh yes, before you lay the ply refastenthe T&G to the beams/carlins etc as its probably held down by steel/iron pins/nails. Use A2/A4 stainless.
 
Seanick, how come you're allowed to scan the forums when you've got a three day old baby!

Thanks for your comments. It looks like I've started a bit of a debate.
As I understand your recommendation you suggest;
1) level the existing deck as well as possible
2) glue 6mm ply onto this using any suitable glue (cascamite? or is this too hard?)
3) sheath with woven glass fibre cloth
4) use a high build undercoat
5) paint as required.

I'm still intent on an efficient non-slip surface so if I go down the glassed top route I'm inclined to replace the undercoat and paint stages with a non-slip layer such as the TBS covering that I mentioned in my first post.

My query regarding the canvas decking you're about to replace is whether or not it was competently applied in the first place. The traditionalist in me still tugs a bit in that direction.
 
Well Les, he was feeding, and lets just say my boobs are not quite interesting enough!

You could use cascamite, but I would go for the polyurethene for 4 reasons. First, its moisture curing/tolerant.
2nd it will fill any gaps in the t&g with its sort of expanding foam, which will fill them, but also crush if, and its a big if, the t&g swells a little.
3rd, it does not require mixing, so quick to use
4th overflow on the deck edge is easy to clean up when dry.

Once sheathed, you can go 2 routes. I was originally taught to leave the resin to go off, then acetone scrub to remove Amine blush, sand to smooth and key, then fill and fair with epoxy and Microlight or Fairlight.

To miss out the scrub and sanding stage you need to skim up the cloth before it sets. This can make a long day !

For the canvas look no skimming is required, but you must lay the cloth carefully, maybe wit a central fore and aft join.

Finally, after you have 2 pack u/coated, which you need to avoid
sanding and get the next coat to stick to the epoxy, you decide weather to go for the maintenance fee 2 pack top coat, or, normal deck paint.
If you go for two pack, a further refinement is to paint 2 coats round the edges of the deck, then mask up the smooth border berfore painting the center areas and sprinkling them with silver sand, Appling a second coat over the top gives good colour and a seriously non-slip finish! It also lasts for years without repainting (about 15!)


The canvas deck has gone on the inside edges of the toe rail, where a little moisture has sat. Canvas is of course cotton, so will rot quite happily!
I really think to give a wooden boat its best chance at long life you need to give it a plastic lid, but well camoflaged!

Iuse Marine and Industrial Sealants in Norfolk, as they stock everything, except SP Hi-build, which I get from Marineware.

Must go, time to change a nappy before the evening feed!
 
I have to say that Nick is very persuasive with regard to the glassing/sheathing. I didn't really want to go that way as I wanted to retain as much of the character of the old boat as possible. However, various folk have been at her before me and so too much pedantry may be unwise - I'm having to strip off an old Trackmark covering from the deck as it is - I certainly don't want to be doing all again an a very few years time.
Thanks for all the comments.
 
I dunno, if you want to keep the character, maybe you shouldn't use the plywood either.

But if you want a good sound job the plywood with the glass over the top makes a lot of sense - epoxied it will prevent the water getting into the ply and then all the different layers that will now make up the deck.

The glass when painted will just be a painted surface like some of the others on your boat already.

I don't know if I agree with the idea of using a polyurethane glue - as far as I am aware they are not gap filling and require quite high clamping pressures - so even though they might fill the voids between the existing deck and the ply overlay with the foamy stuff it would not be structural.

Also will the foamy bits act as a reservoir for water over the long term?

But that is based on my understanding of the polyurethane glue technology - maybe there are some that are gap filling?

Epoxy with an appropriate high strength powder filler/thickener will be gap filling.

As far as epoxy making the decks "too rigid" in some way - this is exactly what will be achieved by the ply.

As far as epoxy being "brittle" - it is one of the least brittle boatbuilding materials apart from metals. I think what people meant is that a coat of epoxy used without glass cloth will crack up. But that will be because a film of epoxy over the decks will not have enough strength. If an adequate amount of fibreglass is used it would be strong enough (I'm not saying it is a good idea - but I am attempting to compare eggs with eggs).

To make it explicit - if you use enough 'glass to provide the same strength as the 6mm ply both jobs will be equally strong and durable.

However I would choose the ply as the end result will end up much more fair than the glass which would just follow the existing surface.

Best wishes
Michael Storer
 
Thanks Michael,
I appreciate your comments.
Spent the day trying to get the toe rail off. You wouldn't believe the number of different sizes, screw types and metals I've come across. I wanted to salvage the rail to re-use it but it appears that part of restoration is demolition!
New rails with bronze screws to come.
Les
 
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