Glue - Crystalisation

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Stephen Hawkins
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Glue - Crystalisation

Post by Stephen Hawkins »

Having announce a desire to own an old Merlin Rocket, I was wondering how the structure of one of these old 'war horses' would be holding up after 40/50/60 years.....

Should I be concerned that I may have to completely disassemble and re-assemble it down the line? An extreme case, I know, but the old phrase '10 thousand rivets flying in close formation' seems to come to mind, an old aerospace saying pertaining to any old, large RAF aeroplane - along with 'if it aint leaking, its empty'....a phrase associated with Lightnings in particular...Anyway, I digress...

It goes without saying that an old boat will need to be treated with some deference, with regard to rig tension and when and where I sail it. But will I be left in the lake floating amongst a sea of wooden parts?

I had an old 1959 wood on frame Heron that was very .....err... flexible athough she sailed nicely and was very usable as a traing boat. I think is was the recent deck that was holding things together, and once I was 'thunked' by a badly driven safety boat that seems to move every panel on the old girl. I could tell as ther were new cracks all over her, especially the transom where the collision occured! Out with the super glue....

I am aware of a recent discussion on this subject that I saw whilst lurking....I was just curious about it in relation to Merlins and thier Clinker construction.

I have a deckless 40+ year old Cadet in my back garden which I am supposed to be re-decking, many of the supports and strengthening pieces were loose and had to be re-glued. The old deck was providing a surprising amount of structural integrity - more that normal anyway.

Balcotan good glue? Its what I am using and seems very strong.

Steve Hawkins
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Ed
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Re: Glue - Crystalisation

Post by Ed »

Gosh, do we have so much traffic at the moment that a great post like this gets lost in the pile!!


There is no doubt that it is likely that the glue used in a classic (pre-65) boat is now giving up the ghost. This does vary. If boat was stored inside, or had an easy life, maybe it will be OK, but on the other hand, this can be very unpredictable. I have had Fairey boats that looked totally sound, but then as soon as I sailed them, they would start to break up.

Some boats seem to go on regardless, with just a loss in rigidity. They don't break up, but just go soft. The problem can be that you don't notice the loss of glue, the broken joint, or the subsequent ingress of water, untill you have got rot set in.

So, sometimes it matters....and sometimes not. Fairey hulls on the whole do not fall apart, but you can hear them start to break between the veneers with little clicking sounds as you walk on them. The cracks (along the veneers) are so small, that you often can not see them until you get the boat wet and as the paint dries, you can see long damp lines along the cracks. To be honest, this does not seem to make much difference except to the loss of stiffness as we said.

Likewise Glued Clinker boats don't seem to break much. The planks are pretty happy where they are and unless put under pressure, seem quite happy to stay in place where they were glued 40 years ago.

The worst (to me, but I may well be biased) are the chined ply boats. The join here can be under more stress and water ingress is more likely and does more damage, as it gets drawn down the inner veneer of the ply to degrade the whole surface. Hence the many Ents, mirrors etc for which the bottom panels go, pretty dramatically when you put your foot straight through them.

I think you were interested in an old Merlin??

If so, here is a tip if you care for old Merlins, or any other 50 year old dinghy. Look for one that has solid mahogany centreboard case. (like Rozzer or my old 14) these are always so very much stronger. It takes away a whole section of the possible problems, is stiffer and looks better to boot. They are always screwed in, so it just keeps them tight and stops those annoying leaks around the case.

But anyway, don't worry about it. When you start re-building give everything a good hard knock, if you feel it move or the sound is any way 'hollow' it most probably needs to come out, but otherwise, just leave it and you an always fix it if you have to later

cheers

eib
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JimC
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Re: Glue - Crystalisation

Post by JimC »

Stephen Hawkins wrote:Balcotan good glue? Its what I am using and seems very strong.
Ask in in 40 years time Steve [grin]
My experience is in general where there is large glue area and moderate load things are OK. Beam joints are the biggest problem. However another twenty years might change that: who knows. I did wonder what the folks who restore DeHavillnd Mosquitos do, because they should be
i) a few years ahead of us and
ii) need to be much more safety critical.
However according to this web page http://www.mosquitorestoration.com/ they solve the problem by throwing away all the wood and the wood glue, which is certainly the right way to get a flying aircraft but isn't quite the sort of activity I usually have in mind when I hear the word restoration.
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Re: Glue - Crystalisation

Post by davidh »

Steve,

Oh dear - I hate to be a harbinger of doom BUT - one of the problems with 3025 (let's face it, a generation younger and more advanced than many of the classic merlins) is that the glue Rowsells used is going crystalline and loosing it's strength. The problems at Whitefriars started when the capping on the rear of the plate case failed, taking with it the mainsheet jammer and leaving me with off the boom skiff style main sheeting!

Close examination of the wood revealed the wood to wood glue joint to have failed completely.

This is something of a worry - if we ever sail in brisk conditions like that again, could there be a sharp 'bang' leaving supercrew et moi sat in the midst of a big pile of planks and bulkheads as the whole lot lets go?

It is a worry - I've tried to check out the areas that I could but the task is just too much - after all, one cannot remake all the clinker plank joints. Jim C has it right in that these in the main are pretty good, however, a sudden impact - as it hitting the jetty coming in - could b enough to start the joints springing and once they go there would be a real issue.



Incidentally, when I was doing my research for last years talk at the Firefly Nationals, I came across a lovely snippet - the mosquito work was one of the first practical applications of microwave technology. They were worried that the glue was not curing on the inner laminates and wanted to get heat into the joint, so tried a huge microwave. In the end, the solution was much simple, a steam oven - the famous Fairey autoclave - where by heat and pressure could be applied to cook the joint!

D
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Re: Glue - Crystalisation

Post by JimC »

davidh wrote:after all, one cannot remake all the clinker plank joints.
I was mulling over that: I don't see why one shouldn't given a sufficiently "valuable" boat that really justified the work... Goodness knows there have been enough full skin replacements on big boat restorations. I guess what you would do is to make a custom "rebuilding" jig that positively located every frame in three dimensions. I don't see why the planks couldn't come off, all traces of glue be carefully removed from all the surfaces and replaced. It ought to be relatively easy in a fairly open boat like a merlin: at least if you accept replacing the decks... Maybe when it comes to the last Proctor mk9 in sailing order in twenty years time someone will feel sufficiently inspired to put that much work in?
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Re: Glue - Crystalisation

Post by Ancient Geek »

Would an epoxy fillet on the inside of the hull in the lands, indeed on the outside too beef the whole thing up, I am sure it would.
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Re: Glue - Crystalisation

Post by JimC »

Ancient Geek wrote:Would an epoxy fillet on the inside of the hull in the lands, indeed on the outside too beef the whole thing up
Well it would, but would it beef it up enough? To get a decent glue area you are probably talking about a fillet on each side that is the thickness of the plank, at which point I should have thought that much of the character of the boat has gone, especially if painted. Those pesky class rules might have something to say too...
There's also the issue of repairs of different ages... If all your original glue has gone crystalline then with luck major components can be separated without too much damage, but if there's any amount of nice fresh solid epoxy in there...
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Re: Glue - Crystalisation

Post by jon711 »

I think your right Jim, can't find a copy of the class rules at present, but feel fairly sure there is something about radii in there, otherwise you could have a clinker built boat, with all the clinkers faired out (with Epoxy) - that would be a smooth skin Merlin, which is being discussed on the MR website now.... But on a Classic, Vintage or old Merlin, would anyone be so anal to protest them?? The main thing is that the boat is being used.... (I don't think I could protest, unless they beat me :lol: )

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Re: Glue - Crystalisation

Post by Ancient Geek »

A quick look at the rules confirms what I thought that on the inside nothing againsy outside as long as the land is radiused no more tham 6mm as it always was and the "corner" of the land no more than 3mm which allows a fair bit of filler.
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Re: Glue - Crystalisation

Post by davidh »

Okay,

with my 'plans to write Vol II of the merlin history' hat firmly on, I have to tell you that it has all been done before!

Years past, a certain sailor had approached David Thomas (yes, he of 'Unit 7' fame) with a commission for a new boat. David, being one of our best and canniest designers, found a wonderful loophole in the rules. They used to say that although the boat should be of clinker construction, that it was allowed to fair the planks in at the point that they merged onto the bow post.

What the rules didn't say (then) was how far back this fairing was legal. So, the new boat was faired almost right back to the transom, creating essentially a smooth skinned merlin (albeit a well faired clinker one).

It was impossible to keep anything that went on in Graham Edwards shed a secret - it was just about the best meeting point east of the Hamble river! So, the word was soon out and equally soon a directive was issued that saw the fairing removed. This was swiftly followed by a rule change that limited the distance from the bow that the hull can be faired - and the loophole was closed.

Should 4 plank or smooth skinned Merlins be allowed? A good question but not, luckily, a topic that will worry us here!!!!

D
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Re: Glue - Crystalisation

Post by Ancient Geek »

David may remember at least four merlins that had planks radiused at 1/4" in old money 6mm in new and the lands were filled to an equal amount all were sailed by David's! Some time after I left the class in 1970 probably when the rules were amened to permit moulded contruction the in fill was restricted. It was also good that the David Thomas was S L O W otherwise even though the stable door had been bolted........
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Re: Glue - Crystalisation

Post by jon711 »

And was this boat Nitro, currently at Oulton??

And sailing in the classic Merlin circuit??

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Re: Glue - Crystalisation

Post by Ancient Geek »

With his historians hat on David may or may not know that the rules did not prohibit smooth skin construction untill about 1949/50. G O'brien Kennedy design and built 2 smooth skin boats one no 75 was 2nd in a championship the other (with a double bottom even.) broke up leading a race another championship! O'brien Kennedy also designed a built a number of boats - Merlin Rockets in traditional clinker construction, in India, which are still in the rafters of The Royal Bombay Yacht Club boat sheds, though about all that is keeping them together is the termites holding hands! Not surprisingly the basic hull looks like a racy lighter Yachting World Dayboat.
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Re: Glue - Crystalisation

Post by Ancient Geek »

YES IT WAS.
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Re: Glue - Crystalisation

Post by chris »

On the original question about glue and strength. I would certainly check places where tension/force is focussed. eg forestay, shroud anchor points, rudder fittings on the transom etc. On 507 I did put new frames in before I redecked (one or two are original but refitted. The transom was renewed but most of the planking has not been touched. But being the first hull that Holt built with glued ply he screwed each plank together evry 4 or 5" (where the ribs would have been) and I suspect this is what has kept her together.
If there are problems it's not too difficult to open a joint, clean the old muck out and epoxy. One plank at a time I suggest. and perhaps Holts screws could be used to clamp together and left there for added strength.
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