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Carbon and epoxy, UV resistance?

J

JKA

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Joined
Jul 25, 2016
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229
Location
Banks Peninsula, New Zealand
Hello The Brains Trust, I have a question.

How resistant to ultra violet light, ie sunlight, is carbon and epoxy? The interweb seems divided on the subject (and there's a thing huh!)

The deck-line fittings on my Romany have taken a hiding over the years and some are starting to crack. A friend has helped me make a mould from which I'm planning to construct more solid fittings, with more material in the area that has force applied when pulling up on the lines, similar to the current iteration from SKUK:

shop.seakayakinguk.co.uk

T Deck Fitting - each

One size fits All - This includes the screw
shop.seakayakinguk.co.uk shop.seakayakinguk.co.uk

Mine will also be twice as 'long' as the commercial ones, again to add strength.

I was going to use a slurry of epoxy and chopped carbon and compress it using the mould. The result would then be machined and drilled on his mill, with appropriate PPE!

However, he has also questioned how UV, which we have in abundance down here, would treat the result. Given that the originals are made from some form of plastic, I suspect my new ones will out last the rest of the boat, and probably me.

However, am I actually on a hiding to nothing and they'll fail at the first sunny day? Enquiring minds want to know.

Cheers

John
 
IMO nothing is holding up to UV indefinitely.... Some chemical structures resist UV damage better than others, but eventually all take a hit (gelcoat chalking, anyone?)

I believe that the commercial deck fittings are made from Delrin, an acetal with some degree of UV stabilizer in it. As you have experienced, it will eventually crack as well.

As a general rule, epoxies are not (long term) UV stable and need some kind of protection (hence the need for varnish of a wooden boat).
Some manufacturers have a product in the line up that they add UV stabilizers to, but unless it says so in the TDS etc I'd assume that it hasn't. You could look at a system that is marketed towards surfboard building?

I'm sure that your improved fittings would hold up for several seasons, but it's hard to tell at which point you need to replace them due to integrity concerns. If you are waxing your boat once a season, paying extra attention to the fittings will definitely help.

I don't know how old your Romany is / how long the original ones lasted, but, in your shoes, I'd probably just treat the fittings as consumables and replace them with commercial ones. Just my two cents, of course.
 
Thanks red kite, great points.

The commercial ones would be the easiest option, but the exchange rate and shipping costs make them prohibitive for me.

Considering them as consumables is sound: my Romany is of unknown vintage but it's had a really hard life before it got to me so they've held up well.

Cheers

John
 
I have a bit of experience with UV and carbon/epoxy laminates...but we don't get very intense UV in BC.
About 10 years ago I installed on a friend's boat a set of foredeck paddleholders made by David Thompson on Orcas Is. (His company was called Alta Kayak, as I recall.) They're made with carbon cloth/epoxy, with a clearcoat of some type over that. They're still intact but the surface layer is disintegrating with a lot of dull areas and some loose carbon fibers. (Nagging about giving them a coat of clear from an aeosol can hasn't worked... :) )
So that would be a good reference for your carbon fittings. BTW, unless you have a cheap source of milled carbon fibers, you'd probably get enough strength with milled glass and black pigment along with the usual thickener for epoxy. They would disintegrate with UV, too, I expect. :)

I have carbon laminate seats in several of my boats, but they don't get muchUV exposure, so not relevant.
 
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If they were mine, I would treat them with several coats of varnish or paint for UV protection. That is what is done with the wood kayaks and canoes that some of us build.

John V B
 
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JohnAbercrombie said:
Expedition Kayaks in Australia use that style of fittings in their Audax kayaks, so contacting them might be worthwhile.
Click to expand...

Thanks John. It looks like they use the KajakSport fittings, not the NDK/SKUK version. They may still fit, but I'll continue on my building mission. I may have to put a sign on the Romany, drawing attention to the custom carbon fittings! ;)
 
JKA said:
Thanks John. It looks like they use the KajakSport fittings, not the NDK/SKUK version. ! ;)
Click to expand...
I don't have a Romany here any more, so I didn't realize they were different. Making molds and casting replicas seems like a lot of work (and expense) to me, but if the SeaLect or Kajak Sport (??) ones ( <$1 each) won't work, and Valley/SKUK won't sell you replacements at reasonable cost, there aren't a lot of options, I guess.

Unless you are using vacuum to lay up the fittings - with cloth - you may find that the result is brittle. I find it tough to avoid resin-rich part layups. I was also surprised the first time I molded a carbon/glass/epoxy coaming - it took more layers (thickness) than I expected to get something stiff enough to do the job.

Also, carbon/glass will chafe the lines a lot more than the plastic did.

If the deck recesses were just a bit deeper you could put a stainless bar across and get a lot stronger attachment point.
 
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