Spa building

[Guest]

Good evening gentlemen.

I am in the process of extending my mast. The previous owner thought it would be a good idea to cut the bottom off and deck step it. This led to its own problems and so I have taken it upon my self to restore back to former glory.

The scarphs are cut and (hail mary) they fit. Ive also sussed out a sound method for glueing up but am undecided on the glue. Thus the point of the story!

Question 1. I have a good quantity of Cascophen resorcinol glue but it is two months out of date (according to the label) Am I taking a risk here?

Question 2. I also have access to an alternative glue: Extraphen resorcinol glue. I am not familiar with this glue. Can anyone tell me what it is designed for?

Question 3. Total glueing area is aproximately 1m square. Any idea what sort of glue quantities we are talking about?

Regards, Dirk (Vincents son)


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[Peterduck]

Resorcinol is a terribly fussy adhesive; you will need more clamps than a hardware store, and the whole thing has to be really tightly clamped. The faying surfaces have to be a perfect fit; nothing less will do. I have found epoxy to be much more tolerant and just as effective. About one litre of glue should be adequate for a square metre.
Peter.

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[Guest]

Perfect fit?! Tighter than a ducks *** ill have you know!

cheers.

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[ccscott49]

i would still go for epoxy, although casco is a superb glue.

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[Gordonmc]

Don't hold me to this... I am quite new to the intricacies of marine wood glue... but both Cascophen and Extraphen are both resorcinol formaldehydes. Extraphen is a Humbrol product and replaced Cascophen.
Shelf-life is critical. If stored below 20C the resin thickens. Other downsides are a long curing period and temperature sensitivity during curing.
When I used it on a spar it left quite a marked red glue line.
On the plus side its, UV resistant, long lasting and very strong.
Epoxies are certainly easier to use.
What wood is the mast made of? I want to replace the mast on my Hillyard 8 tonner this Summer and am thinking of Sitka but am worried about the weight of a solid lump (deck stepped).


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[ccscott49]

I think Sitka spruce is less dense than douglas fir, so would be ideal, it is good for spars anyway.

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[Mirelle]

I would not. Cured epoxy is not UV resistant and softens very quickly with heat - even quite moderate warmth. A mast on a fine summer day could well get warm enough to weaken the bond.

I have an epoxy glued sitka spruce mast (came with the boat) and have had two significant partial failures of the glue line. Repaied with more epoxy, but I wish it had been resorcinol in the first place.

In my experience, handling such a large glued area singlehanded can create, shall we say, "a measure of exitement", the more so as the epoxy must, obviously, be mixed in many small batches to stop spontaneous combustion.

I would go with resorcinol (in date!) + "n" cramps. The recognisable dark glue line is not a bad thing, IMHO, a surveyor will recognise it for what it is if you want to sell the boat, whereas a clear glue line might be urea or might be epoxy.

<hr width=100% size=1>Que scais-je?

 

[ccscott49]

extended my mast with epoxy, wetted the joins first with neat epoxy mix, then thickened with chopped cotton fibres, no sign of anything going wrong yet, after ten years. No sign of spontaneous combustion either and mixed the lot at the same time, for two scarfs. just worked quickly. Resocinol is of course a fabulous glue also and would be good for the job. as long as all the scarf is a tight fit, not just the bits you can see.

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[sailorman]

does this dreadfull news mean that all "mirrordors" are liable to "melt" out of sight
in this summers heat wave?. with flotsum in precut ply shapes littering coastal reagons & rivers

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[Guest]

Thanks for all the help.

The deed is done!

I used the Extraphen and made up a load of my own clamps using angle iron and stud bar. This seems to have done the trick very nicely. I must agree that resorcinol is by far the best glue for this kind of work and its so much more pleasant to use. No mad panic and it also washes off with water if it hasnt already cured.

Not worried about the glue line (looks like its not going to show much) and anyway, shes an other Hillyard. We dont worry about those kind of things.

The mast is Columbian Pine. I think this means its Douglas fir but dont quote me on that. Yes it is quite heavy but again thats classic Hillyard build.

Silver Spruce is suposed to be the muts nuts for spar building. Much lighter and just as strong as sitka spruce. Dont ask me where to get it from.

And for the last time, my joints are perfect! You cynical bastards!

cheers again, im off for a beer!

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[Guest]

In most cases epoxy is painted over or protected in some other way. Therefore there is no UV problem but heat still affects it.

Im not sure of the details but there is a process that 2pac paints, polyester resins and so on, can go through called Post Curing.

I believe this has something to do with cooking the product after it has already set. maybe someone else can explain further.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by vincent on 09/01/2004 19:13 (server time).</FONT></P>

 

[ccscott49]

I fyour joints are that perfect, I may well be extending my mast, again, from the bottom this time, so I will be in touch! /forums/images/icons/laugh.gif

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[Mirelle]

Bravo!

Well done.

I've been considering extending mine, at the top. You have encouraged me to dust the project off again.

<hr width=100% size=1>Que scais-je?

 

[sailorman]

NOT SO MUCH OF THE CYNICAL IF YOU DONT MIND

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[Guest]

Colin,

Unless you already have one, see if you can lay your hands on a number 6 or 8 Try plane. I makes cutting the scarphs a very pleasurable job! Oh and you will probably find you have to sharpen it quite a lot. The resin in the wood blunts it pretty quick.

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[Guest]

Just out of interest, how many of these deck stepped Hillyards have leaky cabin fronts?

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[BrendanS]

as a matter of pure interest, motorboater, so will not need to do it. How the heck do you cut those scarphs accurately? Measure, cut?

<hr width=100% size=1>There is no such thing as "fun for the whole family."

 

[Guest]

Not sure I can do justice to that question with out the aid of pictures but if you were to build a new mast you would sparph the lengths together brfore shaping. I this case making the joints out is a matter of chosing the length (at least 12 times as long as it is wide) and striking a diagonal between them.

In my case, the new portion was as above but in two halves so I finished up with two scarphs facing each other forming a V. The origional section of the mast was to become a point to fit that V. But the origional section is round. This is where things get a little tricky.

Marking the ends of the scarphs was easy enough but I was unable to strike the diagonal. With no line to work to I had to plane these scarphs with a little more care and with copious usage of straight edge and winding sticks.

A little scary at first but quite therapeutic when you get into it.

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[BrendanS]

I've looked on the web and seen examples of the double V shaped cut required.What I don't understand is how you measure, and then cut accurately that shape?

My personal experience with cutting and shaping wood, is such that I'd need several attempts on practice wood before I'd attempt anything like that on a mast, and would probably hand over to a pro rather than do it myself?

<hr width=100% size=1>There is no such thing as "fun for the whole family."

 

[Guest]

Can you keep a secret? I am a pro. Well not really but ive been doing it for 4 years now and ive had some great boss's in that time who have taught me loads. Trouble is im doing it on my own now, hence the questions.

Still, give me another 30 years and ill be able to smoke rollies and drink tea with the best of them!

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