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Thread: Skid plate kits, a word of caution !

  1. #1
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    Default Skid plate kits, a word of caution !

    For the benefit of those who've never tried it before, I had my first attempt at fitting Nova Craft factory supplied Kevlar skid plates at the weekend.
    I'd watched their most recent YouTube video more than once and thought I had it sorted in my head, but luckily I'd also done the unmanly thing and read the enclosed instructions , which stated that it might be worthwhile for the uninitiated to make up two resin mixes rather than one full one.
    I duly did this and thank God I did, because being a very warm day, each mix turned into a hard, unusable lump in very short order, in fact very much quicker that the 20 mins that the instructions said it should be workable for.
    I got the job done, and for a first attempt I'm pleased with the result, but had I mixed all the resin in one go, it would have gone hard before I'd got anywhere near starting the second plate.

    So be warned, do it on a cooler day and out of direct sunlight.
    Nin Wanakiwidee Tchiman

  2. #2
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    Good advice, thank you.

  3. #3
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    Resins kick off a bit slower if you get them out of a pot and into a shallow container. You can also stick both parts in the fridge for a while before mixing.

  4. #4
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    That's the opposite to what I found. The first mix I did, I transferred half the resin and half the hardener into the much larger pot supplied with the kit and that went off really quickly.
    For the second one, I left the remainder of the resin in the (smaller) pot it came in and just added the hardener to it, and I'd say that it took very slightly longer to go off. Not much in it though. I think the biggest factor was the ambient temperature, I wish I'd known about the fridge trick.
    This was my first ever attempt at working with these types of materials and I don't think I'd want to do it for a living, although I imagine it's very satisfying when you get it right.
    Nin Wanakiwidee Tchiman

  5. #5
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    Quote Originally Posted by OLD MAN View Post
    That's the opposite to what I found. The first mix I did, I transferred half the resin and half the hardener into the much larger pot supplied with the kit and that went off really quickly.
    Oh, that surprises me. I assumed it was an epoxy you were using. When I built my stitch and glue, I found that getting a mix out of the pot made significant differences to the gel time. Maybe you were on a hiding to nothing with the high temperature.

  6. #6
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    Quote Originally Posted by bigyellowtractor View Post
    Oh, that surprises me. I assumed it was an epoxy you were using. When I built my stitch and glue, I found that getting a mix out of the pot made significant differences to the gel time. Maybe you were on a hiding to nothing with the high temperature.
    I think the ambient temp played a major part here.
    As for epoxy, I don't know exactly what it was. NC label it as resin to which a small amount of hardener is added. What they call resin is very runny, a bit like watered down paint and it was a oxblood colour to match the boat.
    Nin Wanakiwidee Tchiman

  7. #7
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    I thought I would slow down setting time for some fibreglass resin by putting it in the fridge part of our fridge freezer. My wife was not pleased. Everything in the fridge was noticeably tainted and inedible. Surprisingly so was much of the food in the freezer, including items factory sealed!

    Sent from my SM-T813 using Tapatalk

  8. #8
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    Quote Originally Posted by Gdd View Post
    I thought I would slow down setting time for some fibreglass resin by putting it in the fridge part of our fridge freezer. My wife was not pleased. Everything in the fridge was noticeably tainted and inedible. Surprisingly so was much of the food in the freezer, including items factory sealed!

    Sent from my SM-T813 using Tapatalk

    Whoops
    Nin Wanakiwidee Tchiman

  9. #9
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    Crikey, not the best way to work with resin at all!

    Did the instructions specify that the 2 parts were supplied in exactly the right ratios or were you meant to measure them out accurately?

    Epoxy resin is quite particular about being mixed in exactly the right ratio, and cure time depends on the ambient temperature, transferring to a pot with a larger surface area will dissipate the heat and prevent the reaction running away up to a point, if you are working at much above 25C the gel time can get surprisingly short. Mix ratio is normally between 3:1 and 5:1 depending on the system, and the resin has only a slight smell, the hardener can have quite a noxious smell but it is usually masked once mixed up.

    Polyester resin will cure with anywhere between about 2% and 4% of catalyst by weight. The more catalyst the quicker it will cure and the hotter it will get. You can vary the amount of catalyst to adjust cure time to suit the temperature (up to a point - below 2% may not work and above 4% may cause future problems), and again spreading itout will help dissipate the heat, but it does have a reputation for curing extremely fast (even smoking and catching fire) if you overdo it in warm conditions. The resin has a strong styrene smell which will make you feel light headed and possibly nauseus, the catalyst has a milder smell and is a very small quantity compared to the resin. Most polyester resins are pre-acceelrated these days so no need to worry about that complication.

    My gut feeling is that you probably had polyester and didn't measure the half and half very accurately hence the difference in cure rates, also you could probably have got away with using less than all the catalyst. If it was epoxy and you did measure it accurately, it must have been much cooler in your work area when you mixed the second batch, or you maybe mixed it more quickly, or you didn't hold onto the pot at the bottom the whole time (heat from your hand can speed things up). I have to say I would be wary of using any 2-part system that didn't come with pretty detailed instructions / datasheet, but maybe that's because I already know the pitfalls with these things? The hardeners for both systems are irritants and can be quite harmful, I would want to know the name of the resin and hardener just in case I had an accident and needed to tell a doctor (splash MEKP catalyst in your eye and you will want to be able to tell the doc!), not that I ever have. Epoxies also cause sensitisation. Either way I would not expect a major manufacturer to be sending out kits with poorly labelled chemicals!

    Finally of course it is worth mentioning that there are other resin systems, polyester and epoxy are the 2 you are most likely to encounter in the UK although I think vinyester is starting to be used more here, I have never used it and don't know how it behaves.

    How hard can it be?

  10. #10
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    I think vinyester is starting to be used more here, I have never used it and don't know how it behaves
    I've used vinylester for at least 25 years, it was available under the trade name Derekane. Nick Pink / Impulse used it before epoxy was widely used. It behaves like polyester in terms of hardener type and quantity, but has a viscosity more like epoxy. Once cured it's between polyester and epoxy in behaviour.

  11. #11
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    Quote Originally Posted by Chris_B View Post
    I've used vinylester for at least 25 years, it was available under the trade name Derekane. Nick Pink / Impulse used it before epoxy was widely used. It behaves like polyester in terms of hardener type and quantity, but has a viscosity more like epoxy. Once cured it's between polyester and epoxy in behaviour.
    May well be vinylester in the kit then, OLD MAN's description of the viscosity didn't seem quite right for polyester...

    How hard can it be?

  12. #12
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    But ultimately, yes, small batches are the way forwards unless you are doing something like rolling a filler coat onto a boat and will be applying a lot of resin very quickly. The larger the volume you mix at once, the more rapidly it will go off. Once it starts hardening, it give out increasing amounts of heat and the process accelerates into a chain reaction.

    My experience of polyester is it's all fine until you get a slight "gelling" of the material, that's your cue to put the pot down and make sure whatever is on there already is smoothed down and scraped level. Quickly.
    "I'm not getting in a boat which is DESIGNED to go upside down."

  13. #13
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    not sure about the keel kits but NC boats are made with vinylester resin.

  14. #14
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    Skid plates ... why do you want to fit them? I've seen advice for Royalex boats that said let the boat wear and abrade, you are getting the use out of it and then when/if you need to fit skid plates they will key better to an abraded surface.
    Skid plates ... to protect from abrasion in landing on rough surfaces or from impact? ... the former, yes they do. The latter depends ... a hard enough impact to break the skid plate will rip the underlying canoe ... without the skid plate it might just have buckled?
    Skid plates ... material ... keelezey skid plates are said to be easy to fit (and presumably just as easy to remove/replace). Fibreglass tape should be fairly easy to epoxy in place (available from East Coast Fibreglass Supplies and elsewhere) and fibreglass wears smooth. Kevlar is light & strong but wears furry ... I kevlar wrapped one of my wooden paddle shafts (where it had been eaten by gunwale prying) and it was lovely until I'd worn it back to the kevlar and now it's furry shortly I'll strip the kevlar and do a glass wrap instead.
    The club's Rx canoes have kevlar skid plates.
    Mine don't.
    DCUK
    Can't ytpe or roopf read

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