Re-cabinning our butty.

[Chop!]

The wooden cabin on our butty is as rotten as a pear. I'm in the process of removing the outer skin leaving the inner panels undisturbed.

I'm using best quality 18mm Bruynzeel Hechthout marine ply on the sides, fore and aft with surrounds from green oak.

In order to make curving the roof panels easier I intend to use two layers of 6mm okoume marine ply (with staggered joints) topped off with a final layer of 6mm Bruynzeel Hechthout.

What would be the best adhesive to bond these layers together?

I'm thinking Sikaflex 291i sealant for the joints. Marine stainless screws, it will then be UV resistant stained and then lacquered using Tonkinois Chinese lacquer.

Thanks guys and gals.

[Mike Adams]

I have done a couple of woodentop narrowboats and a cruiser. The only thing that lasts forever is West Epoxy. Bond all the exterior timber with it and then cover with a layer of epoxy, followed by fine weave fibreglass cloth/epoxy then after sanding two pack filler/paint such as Jotun HB with a final coats of two pack Jotun gloss. Mine is as good as new after ten years in the heat of France. You need to keep the water out of the outer layer otherwise it's a waste of time. Bond the cants on afterwards with epoxy. Silaflex at the deck bonds and fittings.

[X Alan W]

Be careful with your chosen fastenings in the oak anything Ferrus will leave black stains  if the wood gets damp/wet

[carlt]

55 minutes ago, X Alan W said:

Be careful with your chosen fastenings in the oak anything Ferrus will leave black stains  if the wood gets damp/wet

+1 here.

 

I would use Silicone Bronze screws rather than steel...even stainless.

[fittie]

Silica bronze screws is the way to go and stronger than SS in my limited experience. All the oak floors in the house are screwed with these and no probs as regards staining.

[Chop!]

My oak cratch boards have been fixed with A4 marine stainless screws for several years now, no staining so far.

But it was what adhesive to use to laminate the three layers of 6mm marine ply together on the roof that I was enquiring about.

[carlt]

13 minutes ago, Chop! said:

My oak cratch boards have been fixed with A4 marine stainless screws for several years now, no staining so far.

But it was what adhesive to use to laminate the three layers of 6mm marine ply together on the roof that I was enquiring about.

 

I may not be the right person to answer this one but I have always used Bituminous repair mastic between the layers.

 

Most would probably disagree however and recommend more modern stuff.

[roland elsdon]

Canvas on top is pretty vital. It also means you can countersink and fill screws through your ply layer rather than relying on bonding. When we did our butty in 1996 we used 8mm ply alone on top of the boarding , on top of roofing tar and mastic.  Not sure why you need 18 mm  on the roof unless you have no boarding. Then canvas then handrails ( well they arnt handrails) as no gunnel. We set the canvas down with fibreglass resin.

its still on there three owners and 22 years later.

old fashioned but practical. Get the end grain well treated too. 

[X Alan W]

40 minutes ago, Chop! said:

My oak cratch boards have been fixed with A4 marine stainless screws for several years now, no staining so far.

But it was what adhesive to use to laminate the three layers of 6mm marine ply together on the roof that I was enquiring about.

West systems adesive (see their web site ) or Aero lite they used this to stick Mosquito aircraft together in WW2 & its still used in wooden aircraft construction/repairs

[koukouvagia]

This looks so familiar.  For twenty five years I've sealed, patched, replaced, mastic-ed, resined, sheathed and painted umpteen times to keep a wooden butty cabin. 

The final step would have been to sheath the cabin in steel, but because the wooden cabin wasn't really the correct shape, I decided to bite the bullet and have a complete rebuild in steel.  I was reluctant to do this, but eventually I decided I was spending more time repairing than I was boating.

Best of luck.

 

Have a look at my website for the full story.

[Chop!]

Our butty did have canvas originally, but it had been damaged and puntured over the years allowing water in, where it sat, merrily rotting the roof boards. It leaked like a sieve, so I removed it and treated the boards with liquid rubber as a temporary fix, it's been dry as a bone since. But the cabin sides started de-laminating and the softwood surrounds became as soft as putty, luckily, the inner joists are fairly sound (as I didn't want to disturb the inner panels).

The intention is to stain and lacquer the whole of the cabin.

I am also modifying the bottom of the new panels to allow Glenda to walk along the gunwhales should she need to.

They aren't really original working boats, although I think the butty was possibly based on an old dumb barge perhaps. As such, I have no need to keep things 'original', when finished our pair will have their own unique style!  A bit like me!

[ditchcrawler]

2 hours ago, X Alan W said:

West systems adesive (see their web site ) or Aero lite they used this to stick Mosquito aircraft together in WW2 & its still used in wooden aircraft construction/repairs

I build a canoe using Aero Lite when I was a kid, glue one bit and hardner on the other bit if I remember right and if you get it on a cut on your hand you know about it.

[BWM]

Not sure on what to bond them with, but the west system mentioned above sounds like a good suggestion. When I re skinned my back cabin I used an epoxy product called timberseal ps, but I have heard that the supplier has gone out of business, I'm sure that west system do a comparable product. Used on both sides and edges of the plywood it will greatly extend the life of it. I am not a fan of glass fibre or similar, as when damaged it sucks water in and hides the damage until it's too late. Don't rely on untreated marine plywood to be any more resilient than decent wbp, you need to treat the inside or decay and early faliure is almost guaranteed. 

[X Alan W]

50 minutes ago, ditchcrawler said:

I build a canoe using Aero Lite when I was a kid, glue one bit and hardner on the other bit if I remember right and if you get it on a cut on your hand you know about it.

Yep the clear liquid was some kind of acid as yo say get it a cut & a war/rain dance shortly followed

[David Mack]

The problem with external sheathing of a wooden cabin, whether with fibreglass/epoxy, canvas or steel is that the timber is permeable to water vapour. So you will end up with moisture from inside the boat getting to the inside face of the sheathing, where it can go no further. As the sheathing is at outside temperature you will get condensation, which over time will rot the wood, and rust any steel sheathing.  I guess this is what happened to KK's butty cabin.

[frangar]

Another vote for West System. They have good tech advice on the website and even run courses on how you use it. 

 

Ive done all the wooden exterior bits such as hatch covers & handrails on my boat with it then cleaned the blush off with the special cleaner, keyed the surface then painted...note..don’t use a wood primer...it won’t harden. 

[koukouvagia]

1 hour ago, frangar said:

Another vote for West System. They have good tech advice on the website and even run courses on how you use it. 

 

Ive done all the wooden exterior bits such as hatch covers & handrails on my boat with it then cleaned the blush off with the special cleaner, keyed the surface then painted...note..don’t use a wood primer...it won’t harden. 

The West system is good up to a point.  Yes, it's fine for slides and handrails, but there are problems when you have a fundamentally rotten cabin to begin with.  As David points out in #15, the damp will eventually permeate to the steel.

Another problem arises when the sheathed cabin dries out.  As you can see from this picture, the dried out wood shrinks and, in my case, began to crumble.

(By the way, I've never had any problem using wood primer over resin.  You do have to make sure the resin is mixed properly and has time to harden).

 

[Bee]

That's not rot - it's heritage!

[frangar]

1 hour ago, koukouvagia said:

The West system is good up to a point.  Yes, it's fine for slides and handrails, but there are problems when you have a fundamentally rotten cabin to begin with.  As David points out in #15, the damp will eventually permeate to the steel.

Another problem arises when the sheathed cabin dries out.  As you can see from this picture, the dried out wood shrinks and, in my case, began to crumble.

(By the way, I've never had any problem using wood primer over resin.  You do have to make sure the resin is mixed properly and has time to harden).

 

Where possible I’ve always applied the resin to all the surfaces to seal the wood totally as you would in say a wooden dinghy. 

 

Interesting about the primer. I’ve always mixed properly & allowed drying time. I had it happen using the craftmaster pink primer and when I coated some hatch covers for a boatbuilder friend of mine he had it with epifaines wood primer....mind you I had told him that it might happen. If you use a universal or metal primer it seems to be fine. Half the trick with painting is to fully remove the blush. Any household cleaner with ammonia in it is suitable according to the West team when I asked them.