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flipper 15th November 2007 03:59 AM

?'s re installing inserts in 12-6 SUP ....
I need to have a shoulder strap on my 12-6 *board sup and my plan is to install a few inserts to attach the strap to. a friend with lots of old windsurf stuff gave me a few of the inserts you see in the pix below.
my plan is to drill a hole, fill it 1/2 up with hardware-store-type 2 part 20-minute epoxy mixed with bits of fiberglass, and shove the insert in. oops-- the first thing i hope i do is tape off the hole so when the epoxy oozes out, it oozes onto the tape and not the board.
anyone see any flaws in my plan? hardware-store epoxy good enuf, do you think? and, what about the inserts themselves, think they'll stay stuck in the board okay? anything else i need to know?

Phill104 15th November 2007 01:51 PM

What is wrong with just looping some straps round the board and fixing your shoulder strap to that?

flipper 15th November 2007 06:20 PM

it's a good idea but in my situation it doesn't work that well. to get to the water i am going down a very tricky, steep, rock-and-boulder strewn hill. more like a cliff. so i need to get the board as high on my shoulder as i can, to work my way around the rocks. with a sling it'd hang too low. and under my arm is too low too.

steveC 16th November 2007 12:54 AM

Hi flipper,

Any time you cut in a board, it's prudent to laminate over affected area with fiberglass or carbon cloth. Epoxy, even when it includes some chopped up fiberglass cloth, just doesn't offer sufficient strength. The lamination step integrates everything into the structure of the board, and it serves to provide the necessary reinforcement outside the boundary of the inserts, especially if the area will see stress of any kind. Given the fact that the weight of the board will balance and leverage off any inserts you install, quite a bit of concentrated stress will be present.

Also, if I were you, I would go for larger, more robust inserts. I would recommend checking out the molded inserts that Chinook makes for footstraps (view at Fiberglass Supply's website). It's important to establish a larger bearing surface that will better integrate with the surface structure of the board (through the use of the fiberglass/carbon cloth), as the internal foam core doesn't offer much support to speak of.

flipper 16th November 2007 08:36 AM

thanks, steve. guess i'll have to use a standard inserts, though the ones in the pix would have been easier ...

PG 16th November 2007 12:15 PM

... And you have to use a slower epoxy to prevent the core from melting...

flipper 16th November 2007 06:04 PM

thanks, guys. and, pg, how slow is slow?

steveC 17th November 2007 12:10 AM

In answer to your question about cure rates, check out the data shown for West Systems epoxy at the following location. You have quite a few options.

Another thing worthy of mention working with catalytic materials is the temperature you will be working at. It's super important to accurately measure portions of resin and hardener within the working temperature constraints.

flipper 17th November 2007 06:21 PM

thanks again. i don't own a router so i'm not going to go with the rectangular chinook insert but with the 1" round one instead and drill 2 holes in it. and put 2 maybe 3 layers of glass over it. that ought to do the trick, right?
as far as cure rates go, given all the options, could you suggest an optimum rate in order to avoid melting the foam?
i'd read elsewhere that one way to go about it is to use a 20 minute epoxy but let it go off for a while before drooling it into the hole, thereby reducing some of the heat. i also read that it's extremely important to keep the hole as snug as possible so that the resin doesn't pool and overheat anywhere.

steveC 18th November 2007 08:40 AM

One of the most important things to understand working with epoxy is that it really doesn't have very much structural strength in itself, unless it's combined with a good design and materials that introduce the needed structural properties (like fiberglass, carbon or kevlar).

Based on my experience, I would recommend trying to keep the tolerances between the cavity and the insert component relatively tight. However, to ensure a super robustness, I would recommend an assembly of hard foam and the insert, and than installing the completed assembly into the board. Also, in going this way, you increase the size of the integrated bearing surface, both internally in the foam and across the area of the lamination. If you have a Dremel tool, you can easily custom a cavity to suit. A router is truly unnecessary, as the cavity area will be filled and buried under the lamination structure, so any minor tolerance variations become a moot point visually.

As far as cure rates, the best choice lies in the way that you go. If a larger volume of epoxy is used, particularly if casting a larger area with just epoxy, go with the slowest cure. If things are done within specification (the mixture and temperature), you will achieve the desired result over time. Catalytic materials are very predictable, keeping in mind the contraints in the use process.

I didn't mention it earlier, but it important not to work the material beyond the recommended working time. This is quite important, as things can quickly go off the map on your project if you exceed the viable timeframe recommended. Only do as much work as reasonable in a single session. A cavalier approach on things can be a bummer, so using the 20 minute stuff and trying to proper time things can be quite risky.

However, based on my recommendations above (going with tight interference tolerances) you can use a quicker, or more regular, hardener that might also be used for laminations too. Really, if things are reasonably tight, you can lose the chopped up fiberglass and easily use microballons instead, or even use only epoxy if your fit is reasonable good. A significant volume of material creates heat, so plan accordingly.

Again, if you find quicker/hotter cure rates a problem, just go with the slower cure rate. Why have to rush things? Time can be on your side.

Two to three layers of fiberglass is sufficient. To gain a bit more dimension of the overall process, I would recommend checking out the Board Lady's website. Eva is a consummate expert, and fortunately, she has offered an incredible amount of sound information on her website. Really, a "must" review for the correct map to the job.

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