Mahogany (?) rubbing strake

[Neil]

Mahogany (?) rubbing strake repair

I have a two-year old boat (GRP, sorry!) with a mahogany, I think, rubbing strake which is made up of 3 or 4 bonded strips. Over the winter, these have delaminated somewhat, to my chagrin. Still waiting to hear what the boat builder has to say on the matter, but I'd appreciate the views of the congnoscenti on this forum on possible ways and means to make good.

I was thinking a West System G/Flex 655-K Epoxy Adhesive Repair Kit and a set of deep-throat clamps?

 

[johnlilley]

Hi there
looks like faulty glue or wrong type of glue in the first place really.
Not easy to re-glue successfully as how can you get full face contact let alone a clean face for reliable gluing.

If you have to repair yourself, then you could drill 3mm holes right through the outer sections stopping before you go right through to the hull, Inject catalysed epoxy into the holes under pressure with a hypodermic syringe , this should be able to partly flood the join from the inside & then open the outside drilling to insert a screw to pull the laminates together. When cured, remove screw, counerbore for plug & refit screw & plug, Do this every 7 or 8 inches & it should be OK.
Failing that, then remove the laminates & start again. Both options time consuming but the first option will be less risk of ending up with broken bits of railing where the glue perhaps has taken.

Trying to force glue down the edges is not going to be very successful really & is best avoided.


See what other options appear!

Regrds


John Lilley

 

[Poignard]

If you bought this boat new only two years ago, I would suggest you start with a letter, and photographs, to the boatbuilder asking him to put things right. Words like 'defective materials and workmanship', 'obviously unsuitable for purpose intended' etc.

However, if you end up doing the repairs yourself, I would suggest you take the rubbing strakes completely apart because it looks like they will eventually fail along their whole length. Clean off the old glue and reglue with epoxy.

 

[Neil]

I suppose I was expecting that sort of response, while hoping for a quick and easy fix. Being in Ireland, it'll be a ferry and a long tow to get it back to the builder in Blighty, but it needs a proper job.

 

[Poignard]

Even so, I would still suggest writing to the boatbuilder with your complaint. Any reputable firm would want to get it put right. If it is not practicable to return the boat to the UK it could be repaired in Ireland with the original builder paying the bill.

If you get nowhere with that, then you ought to get a surveyor to report on it and get estimates for a repair locally. Then consider what legal action you could take.

Why should you have to try and repair it? What would you do if you were not competent, pay someone else?

Also, if you attempt a repair, and make a mess of it, you may forfeit any chance of claiming against the boatbuilder.

Sorry if this is not what you want to hear but a boatbuilder is a supplier of 'goods and services' with all the responsibilities that entails.

 

[Neil]

I agree, and so far, the boat builder has been very good at sorting out minor issues - better than one might expect, in fact. I have reconciled myself to taking the boat back.

I think the problem has arose because my tarpaulin is now a bit leaky on one side, but I would expect that glued wood on a boat, even if it got wet, should stay stuck together.....

 

[Poignard]

... but I would expect that glued wood on a boat, even if it got wet, should stay stuck together.....

Absolutely - a boat is going to spend all its life getting wet, and the materials and the workmanship must be up to a standard that allows for that.

 

[srp]

Looks like it was glued with Cascamite (or whatever it's called nowadays). You won't be able to clamp the joins and close them up satisfactorily with an in-situ repair because the old glue will stop it closing up and the new glue won't penetrate into all the crooks and nannies.
The answer is to take the strake off, and with the fixings removed it will probably fall apart with minimal persuasion. Clean up, replace any split or splintered bits, and laminate properly using epoxy. You'll need a million g-cramps and some spreaders to brace the hull widthways (to keep the shape). When the epoxy has cured you can drill the fixing holes and bolt it in position.

 

[northwind]

I think the problem has arose because my tarpaulin is now a bit leaky on one side, but I would expect that glued wood on a boat, even if it got wet, should stay stuck together.....

Really?

I first read this over on the PBO forum.. I was thinking we'd see a huge gap or some other problem..

Wood is a natural material, subject to movement stresses, and will change shape depending on what it is subjected to. (Wood is after all a sponge for mositure).

As you have pointed out, you have had a leaky tarpaulin on the boat over the winter, any wood that is constantly wet will swell, and this can cause glues to fail or the wood to crack. I'd guess that letting air get to this and some warm spring sunshine and it will change shape again. Personally I'd say its better the joint has opened up than the wood has cracked.

This is not the builders fault, and it sounds like he has been reasonable in his offer to look at this for you. It is part of the fun of ownership, and just one of those things. After 10 years my hardwood gunwhales have opened up in places more than this, as others have said you can either live with it, or choose to try and fix it.

 

[Ubergeekian]

I have a two-year old boat (GRP, sorry!) with a mahogany, I think, rubbing strake which is made up of 3 or 4 bonded strips. Over the winter, these have delaminated somewhat, to my chagrin. Still waiting to hear what the boat builder has to say on the matter, but I'd appreciate the views of the congnoscenti on this forum on possible ways and means to make good.

I was thinking a West System G/Flex 655-K Epoxy Adhesive Repair Kit and a set of deep-throat clamps?

I would very much doubt that an in-situ repair would work. Far better to split the thing completely apart - which shouldn't take long, as it looks - and then relaminate from scratch.

 

[Tranona]

Really?

I first read this over on the PBO forum.. I was thinking we'd see a huge gap or some other problem..

Wood is a natural material, subject to movement stresses, and will change shape depending on what it is subjected to. (Wood is after all a sponge for mositure).

As you have pointed out, you have had a leaky tarpaulin on the boat over the winter, any wood that is constantly wet will swell, and this can cause glues to fail or the wood to crack. I'd guess that letting air get to this and some warm spring sunshine and it will change shape again. Personally I'd say its better the joint has opened up than the wood has cracked.

This is not the builders fault, and it sounds like he has been reasonable in his offer to look at this for you. It is part of the fun of ownership, and just one of those things. After 10 years my hardwood gunwhales have opened up in places more than this, as others have said you can either live with it, or choose to try and fix it.

Leaky tarpaulin or not, this shoulkd not have happened if the lamination had been done corectly. Outside my study window is an epoxy bonded ply dinghy that has been sitting out in the open for over 20 years. Every lamination is perfectly sound.

It is quite clear that the OPs boat was not built properly.

 

[Neil]

I've been in various correspondence with the technical department of West System, who have been very helpful.

The builder didn't favour epoxy as glue for this application; he says it's too brittle and this application needs some flexibility. The wood was sealed with two-part polyurethane (obviously not well!). He says he now uses Sikaflex to glue the strips together (perhaps I'm not the only one with the problem?), and is suggesting this for the repair.

It may be that it is not practical to remake the laminated rubbing strake - most areas are still glued and may be damaged if the layers were separated. The gaps between the layers are only approx 1-2 mm. The boat builder says that some flexibility is required in glueing the strips of mahogany. He concluded that moisture has resulted in differential expansion of the layers, breaking the glue line. He now favours the use of Sikaflex to glue the laminations of the rubbing strake.

However, the chemist at West takes a different view. He thinks the issue is more a question of technique than adhesive selection. he says that mahogany is not hard to bond to and suspects glue starved sections of the rail caused the problem. Perhaps they were glued with polyester (not a good choice, he says) or more likely they were wet out and clamped in a jig right away – regardless the glue used. The glue then soaks in erratically due to grain variation and you can end up with spot delamination.

I think I have more than spot delamination, but I understand that each layer was glued and screwed in turn.

The man from West says that it looks to him from my picture that the glue line is starved. He also says that Sikaflex is not an adhesive – it’s a sealant. Yes, it sticks tenaciously to the surfaces it contacts and is quite flexible, but it has no cohesive strength to speak of.

The ideal process would be a 2 step technique where the prepped laminations are coated with un-thickened epoxy and allowed to sit until it gels (gets tacky) then a second coat of un-thickened epoxy is applied and the laminations get loaded into the jig. With this method significant clamp pressure can be used to minimize the glue line thickness and still avoid a glue starved joint.

For a limited area repair, he recommends heating the areas that need to be filled so that the area is at least 20 – 30F above the ambient temperature. Heat the G/flex 650 resin and hardener in their bottles, mix it warm and spread or inject (the 807 syringe) the mixed epoxy onto the heated surface. The heat will thin the epoxy and as the air in the wood and the spaces cools it contracts and draws the epoxy in as deep as possible.

Then encapsulate with epoxy to stabilize the wood and keep moisture out or re-do with two-pack polyurethane?

Anyone know of a cheap source of deep-throat clamps?

 

[Tranona]

I agree entirely with the West man. I have been using epoxies since West first became available here over 30 years ago. I have NEVER had a laminated joint fail like that. Your builder clearly does not understand how to use the product - which is not difficult if you follow the instructions. As I noted elsewhere I have a ply dinghy I built in 1981 that has sat outside untouched for at least 20 years (now a garden ornament!) and every joint is sound. The mahogany rubbing strakes and toe rails on my Eventide were attached with West in 1988 and still perfect.

So, follow the instructions for the repair - try and clean the faces in the splits with a piece of hacksaw blade. Don't over clamp them as the West is structural. You can buy pressed steel clamps with 4 inch throats from sheds like B&Q or Screwfix quite cheaply. Personally I would remove all the 2 pack varnish and re-finish with Sikkens Novatech/Top as this gives better UV protection and is easier to keep looking good for longer. High gloss impervious finishes are fine in a piece of furniture, but not ideal on the rubbing strake of a boat that is used.

 

[Poignard]

Anyone know of a cheap source of deep-throat clamps?

APTC Ltd, but why do you need to know that? You're surely not going to repair it yourself when you would seem to have a cast-iron case against the boat-builder?

He has not done his work properly and should put things right, at his expense.

If you bought a new car and it started to fall apart after two years would you be on a motoring forum asking where to buy a welding set?

 

[srp]

I agree with the man from West as well - I still think that the best repair would be to split the laminates and re-glue, but you may not have the facilities or the inclination to do this. From a practical point of view the simplest solution is to follow the West repair instructions. You may well have a case against the builder but it might cost too much to pursue, and if he did the repair with Sikaflex it would be a bodge anyway.

 

[Neil]

I agree with the man from West as well - I still think that the best repair would be to split the laminates and re-glue, but you may not have the facilities or the inclination to do this. From a practical point of view the simplest solution is to follow the West repair instructions. You may well have a case against the builder but it might cost too much to pursue, and if he did the repair with Sikaflex it would be a bodge anyway.

This is exactly my view; not the best solution, but pragmatic. I might send him the receipts for the G-Flex and clamps......

 

[Roach1948]

An alternative approach?

How big is the boat? If quite small I suspect it might be quicker and less hassle to make new rails in solid iroko - cheap and quick and saves a bomb on West and Labour. Just one tip, think about the way the scarphs will go - they will pop-out if placed the wrong way around. Oh - and with solid rails you will never have this problem again and they will look better.

 

[Delfin]

Hi there
looks like faulty glue or wrong type of glue in the first place really.
Not easy to re-glue successfully as how can you get full face contact let alone a clean face for reliable gluing.

If you have to repair yourself, then you could drill 3mm holes right through the outer sections stopping before you go right through to the hull, Inject catalysed epoxy into the holes under pressure with a hypodermic syringe , this should be able to partly flood the join from the inside & then open the outside drilling to insert a screw to pull the laminates together. When cured, remove screw, counerbore for plug & refit screw & plug, Do this every 7 or 8 inches & it should be OK.
Failing that, then remove the laminates & start again. Both options time consuming but the first option will be less risk of ending up with broken bits of railing where the glue perhaps has taken.

Trying to force glue down the edges is not going to be very successful really & is best avoided.


See what other options appear!

Regrds


John Lilley

The only thing I would add is that what hasn't failed is going to. Test to see if you can effectively clamp and move the pieces where they need to end up. If the gap still exists, it will have to be removed. If you do undertake the repairs, John's advice to screw and plug every few inches will keep what hasn't failed yet in place.

 

[Roach1948]

Anyone know of a cheap source of deep-throat clamps?

Yes, make your own.

Cheap PVC pipe - cross cut into 2" sections - and then long cut open with jigsaw - hundreds of "C" clamps at a few pence each. Of course thickness of strake will determine what pipe daimeter you go for.

 

[Neil]

How big is the boat? If quite small I suspect it might be quicker and less hassle to make new rails in solid iroko - cheap and quick and saves a bomb on West and Labour. Just one tip, think about the way the scarphs will go - they will pop-out if placed the wrong way around. Oh - and with solid rails you will never have this problem again and they will look better.

It doesn't sound quick and cheap; would it have to be steamed and bent? What's a scarph?