Best glue for wooden spars?

Seagreen

Seagreen

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So whats best? I'm glueing a 12' topsail yard in halves, and as a wooden spar (Douglas fir) it will take a lot of bending stress. I've loads of epoxy to hand but I feel that the epoxy won't be flexible enough so what would the forum experts suggest, please?

And yes, I know this seems better suited to the Classics forum, but it has an uncertain future and more of us are on this forum.

;)
 
I used polyurethane wood glue from screwfix to laminate my bowsprit (Iroko). Hanging together well after a couple of years. It says seawater proof on the bottle.
 
as usual there is no "best" glue. Epoxy will be fine structurally but needs UV protection. Resorcinol is commonly used and polyurethane is OK provided you are not relying on its gap filling as structural - joints should be good fit.
 
As I was building a mast just after those guys did the biggy for Lulworth, I asked them what the melamine stuff was they used. Turns out it was Urea Formaldahyde (AKA Aerolite) but modified with melamine. Accelerated aging tests suggested it was best. At 156ft they needed to get it right. Their source was an industrial supplier (in Germany?)
In the end I used epoxy, as I had it. Fine after 4years for all three spars.
 
Seagreen said:
So whats best? I'm glueing a 12' topsail yard in halves, and as a wooden spar (Douglas fir) it will take a lot of bending stress. I've loads of epoxy to hand but I feel that the epoxy won't be flexible enough so what would the forum experts suggest, please?
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I'm very fond of Cascamite glue for composite structures. I've never made a spar, but if I did, that's what I'd use. It's a urea-formaldehyde resin glue, like aerolite.
 
Ubergeekian said:
I'm very fond of Cascamite glue for composite structures. I've never made a spar, but if I did, that's what I'd use. It's a urea-formaldehyde resin glue, like aerolite.
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really good for stuff like that but not sure its still called cascomite think
Its changed hands a couple of times this past few years
 
As ever, a whole bunch of opinions and all of them different. :D

I've used Aerolite in the past, I think in building a mirror dinghy in my teens. What about Balcotan, or doesn't it have the flexibility of the other glues? I could always default to epoxy, but.. doesn't feel right somehow. Or is that just me?
 
Cascophen would be better than cascamite for outdoor work such as spars. There are newer glues out there I'm sure, but cascophen is a well tried and tested waterproof wood glue. The name may have changed recently although a little detection work would find it on the net. My spelling of cascophen may be slightly adrift,apologies if so.
Good luck.
 
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fergie_mac66 said:
really good for stuff like that but not sure its still called cascomite think
Its changed hands a couple of times this past few years
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But yes, there do seem to be quite a few versions around these days.
 
Cascophen is a resorcinol glue, Cascomite is urea formaldihyde. If the former, fine glue lines and high clamping pressures. Plus better than 10 deg C over the curing time. If the latter, less tight joints and less problems with temp.
Balcotan is a P-U glue. Tight joints and medium clamp pressures. But, I had an unexplained failure,so, not keen. ( it was Bostik, not Balcotan, similar stuff)
 
Always been a bit careful with cascomite wouldnt use for any framing, although its gap filling, its brittle when set, so catch a frame hard on a diagonal and the glue line can fracture
 
Seagreen said:
As ever, a whole bunch of opinions and all of them different. :D

I've used Aerolite in the past, I think in building a mirror dinghy in my teens. What about Balcotan, or doesn't it have the flexibility of the other glues? I could always default to epoxy, but.. doesn't feel right somehow. Or is that just me?
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Balcotan is moisture curing polyurethane glue. Should be fine. Good gap filling properties as it expands when curing, but not structural in the same sense as epoxy. Not sure why you are worrying about flexibility of the glue line. None of these glues are brittle in the sense that they fail if the wood bends.
 
Tranona said:
None of these glues are brittle in the sense that they fail if the wood bends.
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OK so I may as well use epoxy, but I have issues with the exposure to UV, which is causing me some problems in other areas. However, epoxy with wood-sandings as a filler (instead of colloidal spheres) would leave an invisible join, so may look better. The brittleness vs bending was my chief worry.
 
When I had to glue a wooden mast I went to great lengths (pardon the pun) to find the 'right' glue.

I had assumed that I was going to use epoxy, but was heavily recommended not to by several sources (surveyor - boat builder etc)

The glue I ended up with and was recommended the most was Cascophen. It was easy to use and the wooden mast (which was nearly fifty years old when I re-glued it) is still perfect ten years later.

I was told that Cascomite is too brittle, and stand fast the UV problems with Epoxy, it also isn't flexible enough for mast use.
 
Seagreen said:
OK so I may as well use epoxy, but I have issues with the exposure to UV, which is causing me some problems in other areas. However, epoxy with wood-sandings as a filler (instead of colloidal spheres) would leave an invisible join, so may look better. The brittleness vs bending was my chief worry.
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For glueing it's best to use micro fibers rather than colloidal silica with Epoxy. micro fibers increase the strength and flexibility of the glue, colloidal makes it more viscous and ultimately more brittle when it sets.
 
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