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gelmagic or 610


JohnT

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Just getting started on a SpinDrift 10n. I have my scarfs complete and for a first time scarfer I think they look good. I am planning on sealing the end grain with some epoxy so I won't get a dry joint. What I am pondering is the actual bonding of the 2 panels, should I use System Three Gelmagic or West Systems 610 ? Pros and cons for each ?

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I am planning on sealing the end grain with some epoxy so I won't get a dry joint.

NO!!

You want the epoxy that bonds the pieces together to absorb into the wood. Sealing it first will prevent that. You prevent dry spots in a joint by wetting out both mating surfaces for gluing, not just one.

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OK. I understand, just how generous should I be on the wetting out ? Should the plywood look porous or glossy ? What I have on my shelf right now is West System 105 epoxy and WS 207 hardener. Will these be OK for the scarf joint ? Also still looking for opinions/experiences with Gelmagic and 610.

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West System is good stuff, though I never hear of 610. No idea what Gelmagic is. Wet out each face rather generously and wait a couple minutes. If it seems to absorb a lot then wet out again. Although for Okoume plywood I found one generous coat on each surface is plenty. You want the epoxy absorbed into the wood and then some still on the surface. When you clamp the pieces together you should get some oozing out. Now you know there are no voids. I use colloidal silica as an additive to epoxy for gluing, the West version of that is 406. Many just use wood flour. The main reason for an additive for gluiing is to create a consistency that will bridge gaps due to imperfection in the joint.

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Thanks for the advice. First boat project and first time working with epoxies. I am usually not so cautious about projects but at $70 a sheet for plywood I don't want to make mistakes. I have one more question. Glue the scarf joint then tape or glue and tape at the same time ? I have heard of taping the scarf joint after lofting and cutting pieces out to save on materials. Any thoughts on this ? Thanks

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If you do a good job on the scarf joint there is no need to tape it at all. It will be as strong as the plywood itself. The reason for scarfing vs. taping a butt joint is to make a very fair hull and/or to finish it bright. I did scarf joints only for my 9N and it has held up for years without the slightest sign of failure.

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Yes, a scarf joint is strong enough without tape. I do carefully run 2" clear packing tape on either side of the scarf joint, both sides of the ply, just to make joint cleanup easier - just peel tape and thin layer of squeeze out right off. And if possible I scarf panels together, loft parts and then cut them out. I think it is easier to scarf full panels together than to attempt to line up narrow parts for a scarf.

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I presume the Gelmagic you are referring to is the system 3 structural adhesive epoxy? I have some and while yes it works, I found it to be so thick that it was difficult to get it out of the container and get it measured accurately. If you do, and get it mixed correctly, it does make a very good epoxy for things like joining wood pieces, stringers to plywood, etc. No additives needed.

Marketing aside, West Systems or most of the other 2:1 epoxies, even the generic System 3 stuff will work just as well, but you will need the basic thickeners, such as silica or wood flour. With some experience, you quickly learn how much of what. In most cases, if you do a good job of mixing and application, the epoxy joints are stronger than the wood, and that is with almost all of the major brands, such as Raka, MAS or the product Graham sells. They are all pretty good.

Put another way, I have the Gelmagic and never use it. If you really want something limilar, try the MAS products. They are a bit expensive, but very good. One is thicker for laminations, fillets and such. The other has a low viscosity for wetting out glass. Both work well. But then so do the others.

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Do yourself a big favor and download the free "user's guides" at westsystem.com and systemthree.com. These will nurse you through the proper procedures and products, which of course are geared at their own stuff.

Avoid the "fancy" formulations, such as Gelmagic, G-10 or other special mixtures. These are special application products and you need to have a much better handle of the the processes and physical attributes you need in your bonds and laminates.

Gelmagic is a pre-thickened SilverTip product (System Three). You pay dearly for this pre-mixed formulation, when all you need to do is add the appropriate types of fillers to a straight laminating epoxy. Admittedly, some find a pre-mixed fairing compounds handy, but again you pay quite a price for these types of mixtures, compared to mixing your own.

To give you an example of how dearly you pay for this pre-mix stuff. 610 is West System's cartridge delivered, thickened epoxy. Each cartridge is 6.42 ounces (190 ml) and retails for about $22. This means you're paying about $440 per gallon for this mixture. Ouch, especially when their straight epoxy retails around $110 a gallon.

Lastly, West System and System Three aren't the end all to epoxy formulators. They're the industry leaders, but also the most costly. Try Bateau.com for their "Marinepoxy" which is about $60 a gallon in small quantities and as low as $45 in larger. For the price of one gallon of West 105/205, you can have a gallon and a half of other brands and the fillers to thickened it too, for the same money, so educate yourself on the materials, processes and techniques.

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Well I have successfully epoxied two practice pieces together with great success. Then I tried to break the joint with no success. So this morning I epoxied my project pieces together using the packing tape and a little collodial 405.

PAR - thank you for putting the cost in perspective. I guess mixing a small quantity by hand is worth a couple minutes of stir time compared to paying 4 times the amount for the epoxy.

I guess i will need to find a good source for small graduated cups

Thanks for all the input I'm sure I will be back with more questions before long

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Make your own graduated cups from inexpensive clear plastic drink cups. The shallow 8 oz version works well for smaller batches. The 12oz size for the larger ones.

Start with two cups, one inside the other. Use a calibrated cup and being as precise as possible, measure out an exact quantity......say 20 ml of water. Pour that into the inside cup. Then, with a permanent marker like a fine tip Sharpie, mark and label the level on the outside cup. If using a 2:1 epoxy, then measure out half the first amount (say 10 ml) and pour that in. Mark and label that level on the outside cup.

You now have a graduated measure cup to mix 30 ml of epoxy. The graduated outside cup is saved (never used), the inside cup is used and tossed each time. I have these for 30, 45, 60, 90, and 120 ml. For smaller amounts, you can go to a drug store and get graduated plastic medicine cups. Those are good for batches in the 7.5 to 30 ml range. Those are used each time and simply tossed.

A lot of people also use calibrated pumps, and if careful and nothing goes wrong, they will work too. I've had a few malfunctions using those and always found it simpler and easier to use my graduated cups.......even if I'm pumping into them.

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I have found West System pumps work very well for years. If you are using a 2:1 epoxy you can use the same pump for each component and just use a 2:1 ratio of pumps instead of the intended same number of pumps with a 2;1 ratio of liquid pumped. The only time these gave me any trouble is when they were left out in the cold. But then warming them and the epoxy back up solved the problem. To each his own, but I like pumps.

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I too like the pumps- I've used them for years with no problems at all. Since about 1976 in fact. The only real problem I've ever heard about is people mis-using by pumping twice with resin and once with hardener (on 2-1 mixes) instead of once with each, on calibrated pumps. Most are and the pumps you get from B and B for 2-1 most definitely are calibrated.

The marked plastic cups are also a very good way to measure, but I find that the pumps are better for small amounts.

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Where I had trouble with the West System pumps........nothing wrong with the pumps......it was my technique and product of using their small cans of hardener. Five pumps of resin........five pumps of hardener......except on the 3rd or 4th stroke, the can ran out.......and I got a misfire. Once that happened, you were left guessing how much you put in and how much more you needed. Best solution to that is to alternate strokes......one pump resin, one pump hardener and alternate your way to however much you want to mix. If making up a pint or more of mix for a larger wet out, that can make for some pretty good aerobic exercise. Pouring that amount from the jugs is faster.

And unless you are constantly into the goop, if you let the pumps sit around for a while, they can clog. My last set of pumps did just that, sitting in a gallon of resin and half gallon of hardener. The resin and hardener are still good, but the pumps are hopelessly clogged. I'm still using the goop, but I'm having to pour it out of the jugs. Again, no fault with the pumps.......more with my technique and situation. But graduated cups is what saved the day and is allowing me to keep using from those jugs.

When the pumps were working, I'd use them for small amounts, but still used some type of graduated cup to measure with. About the only way to mess up the cup in a cup system is to forget to put in the liner cup.

For small jobs, I would not hesitate to suggest using the WEST System resins and hardeners and using their pumps. West Marine stores carry those in stock and if I wanted an epoxy TODAY, I'm just over an hour from a West Marine source. But I'd also pay a price for that. For a big job, I'd rather use Graham's stuff, or RAKA or many of the other 2:1 mixes purchased economically by the gallon. I have to get those mail order.

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One thing I've done for layups where I need a quantity of epoxy (mixed over the space of an hour, for example) is to pre-dispense 2 floz of epoxy resin into a number of cups. The resin is what takes effort, and time, to pump. If needed, I'll write the volume on the cup with a Sharpie marker.

Then, all i have to do is add the correct number of pumps of hardener (which pumps really easily by comparison), mix, and apply. The rest of the cups of resin-only are just sitting there waiting for me, and I'm not wasting their working time.

I also always keep a logbook of what I mixed, and when I mixed it. In the middle of a layup, I can't possibly remember how many minutes of working time I have left on this particular batch. Looking at the log, I can see it was mixed at 9:42pm, the manufacturer says I have X minutes of working time, so I know whether to relax or hustle. This also helps me keep track of the thickeners I've used, and what ratios / quantities worked on the last batch.

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