Edition
Boats for sale
| Laser 28 - Excellent example of this great design Hamble le rice |
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| Rossiter Pintail Mortagne sur Gironde, near Bordeaux |
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List classes of boat for sale |
My winter Project |
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kfz 
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Joined: 02 Nov 10 Location: UK Online Status: Offline Posts: 96 |
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 Topic: My winter ProjectPosted: 21 Nov 10 at 1:15pm |
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Glad you guys are enjoying....
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kfz
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Joined: 02 Nov 10 Location: UK Online Status: Offline Posts: 96 |
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Posted: 21 Nov 10 at 7:20pm |
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Mostly worked on the centreboard case today, but not a great deal to show for it, slow going. I did prep the hole in the port quarter to take a patch, should be a neat job. Note how Ive cut away to leave a lip and give the patch support. Ive got some oak (try and save my mahogany) to make some support shoulders out will either Screw and gorilla glue them in or just epoxy. Kev   |
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kfz
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Joined: 02 Nov 10 Location: UK Online Status: Offline Posts: 96 |
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Posted: 22 Nov 10 at 10:11pm |
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20.11.2010 Centreboard crack now filled with epoxy. Using room temperature slightly thinned with the hot air gun and easy on the hardener to give a long cure time Very happy with this repair its a bit of a bodge but not sure what else could have been done without major woodworking surgery. I guess the proper chippy solution would be to mill out a complete section and replace with fresh wood. The very slow process of wood fillets, not only are they slow to make having to be fitted by hand then have to wait 24 hours without disturbing the case while the glue cures. Again I used Gorilla glue to wetted surfaces. Though I think epoxy may arguably be better, if even slower. Also very lucky to have a good wood match with the unobtainable mahogany, a salvage kindly donated.
The cutout in the front section of the case also needs to be filled with a fillet, going to take some careful fitting. |
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JimC
Really should get out more 
Joined: 17 May 04 Location: United Kingdom Online Status: Online Posts: 6661 |
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Posted: 22 Nov 10 at 11:21pm |
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Ah. Not a good idea. Epoxy works quite differently to things like Aerolite or Polyester. With polyester or aerolite glues the hardener is a catalyst that takes no part in the chemical reaction, it just kicks it off. So less or more hardener, which is in small quanties, just affects cure time. With epoxy resin the two components combine, so if you mess with the proportions then you end up with unreacted resin (or hardener) so you are compromising the strength and wasting money. That's why you get different speed hardeners with epoxy so that you can control the reaction speed without changing the mix ratio. |
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alstorer
Really should get out more
Joined: 02 Aug 07 Location: Cambridge Online Status: Offline Posts: 2899 |
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Posted: 23 Nov 10 at 6:58am |
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True- though if well formulated they'll go about 10% of the hardener either way without huge issues- more than that and you'll risk (especially with too little hardener) a sticky mess
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-_
Al |
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kfz
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Joined: 02 Nov 10 Location: UK Online Status: Offline Posts: 96 |
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Posted: 23 Nov 10 at 7:57am |
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Woa Jim calm down. Its was roughly 5 to 1 (as per the blurb), didnt measure it his time as my measuing cylinder has expired. I normally mix it a bit more hardener as Im working outside but didnt this time I was inside and the mix was warm to start with. Kev
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JimC
Really should get out more
Joined: 17 May 04 Location: United Kingdom Online Status: Online Posts: 6661 |
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Posted: 23 Nov 10 at 8:45am |
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I think you're still partially missing the point. Because its a reaction of two components, not a catalysed reaction of the monomer, changing the proportions will not usefully change the cure speed, only waste material, reduce strength and risk it not curing properly at all.
The little plastic measuring cups that come with some cough medicines and the like are handy for measuring epoxy. For even smaller quantities try measuring spoons! Edited by JimC - 23 Nov 10 at 8:52am |
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I luv Wight
Really should get out more
Joined: 28 Jan 05 Location: United Kingdom Online Status: Offline Posts: 628 |
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Posted: 23 Nov 10 at 8:55am |
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It will change the cure speed if you don't get close to the required ratio... to very very very long = never !
I always use digital kitchen scales and never* get it rubbery, - doing it by volume results in duff mixes  * well almost never, it does happen very occasionally, but maybe one mix in a thousand when I get my numbers wrong  |
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kfz
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Joined: 02 Nov 10 Location: UK Online Status: Offline Posts: 96 |
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Posted: 23 Nov 10 at 9:10am |
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Jim,
No you are, its mixed in the correct proportion. I will change the blog, its not clear. I will leave the post above otherwise the thread doesnt make sense if I amend it. sorry, I understand not to change the proportions. Kev
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alstorer
Really should get out more
Joined: 02 Aug 07 Location: Cambridge Online Status: Offline Posts: 2899 |
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Posted: 23 Nov 10 at 10:14am |
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Jim's point rather stands though- not great practice to add more "to make it go quicker outside" as you'll make the final resin worse.
As for voume verus weight? Remember the proportions are different. They'll hopefully be close, but will vary due to density differences. We've got a product designed for 2:1 by volume cartridges that is 100:45 by weight. (though formulated with a much smaller tollerance than your marine stuff)
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Al |
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