Continuing from the thread on swing rigs, we started a discussion on epoxy:
Marc,
the insulin syringes are the one type that will not work. the needle is too small to allow the viscous solution to flow. That is why I mentioned syringes without needles in the original post. Standard syringes with what are called luer tips are the best, luer locks second best since they are harder to clean out between uses. properly cared for, they last a good while.
re shelf life; I bot involved with model ship buiding 9 years ago and have built about a dozen 3-6 foot warships for combat - lots of epoxy in building and repair - I buy West by the Gallon and it usually lasts 3 years. The hardener does oxidize and change color after a while but this does not affect its strength - per tests by the manufacturer and my experience. It costs about US$90 for a gallon of resin and a quart of hardener or about twice the price of polyester resin. It is used on full size race boats at 90 miles per hour so it is quite strong. I feel you get what you pay for.
I’ve been very happy with west, and yes its expensive, hence the reason for wanting to figure out the best way to make small consistent batches.
I have used the insulin syringes for getting CA into some exacting locations… but the CA is plenty thin
I “vaccum bagged” my mast using one of the clothes storage system bags for suits. I used wax paper and paper towels around the mast to help “release” from the bag.
worked pretty good. I was able to get most of the wax paper and paper towels off with out much sanding…I was going to have to sand for shape anyhow so it was not a huge deal.
I had the soling out some high (15-20) winds and it performed great. It would have been really easy to squeeze some carbon or glass between the halves, to help strengthen the mast, if the rules permitted…
I don’t even buy the the 5 minute stuff from the hobby store any more…
If you check on-line (I get tons of catalogs in my job that have these) you can purchase syringes with flexible small tube tips. The entire thing is polypropylene and the tips are flxible allowing you to bend then to get into tight spots. Because they are plastic, epoxy will not stick to them and if placed in acetone or laquer thinner immediately when done, the epoxy will wash out and the syringe can be used indefinitely.
They look something like this… can’t find a catalog when you want one around here !
You can also purchase a West System ‘tm’ small batch epoxy scale sold with assorted mixing cups, should alleviate any worried about exact proportions. It costs around $40.00 so not cheap, but if you use a lot of epoxy it might save you money over a year or two. (two year warranty) Supposedly it will measure down to .15 gm, which is just a few drops. They should be available at most marine stores, if you can’t find one send me an e-mail I’ll give you some sources. I work in that industry, and I’m not going to advertise here. Paul
I found an Adam Equipment AQT600 digital scale on craigslist.
Max capacity is 600 g (~1.3 #'s) and measures to 0.1 g. I mainly purchased it for managing the weight budget for Footy building. They have other capacity scales.
I am planning to add a section on our www.tanglewoodmyc.com website to show unit weights of various items used in Footy construction (batteries, balsa, ply, etc…) If you have any special requests for items post them here or start a weight budget thread…
The scale works great with hobby shop epoxy squeeze bottles to get correct porportions. Also works for mixing paints for special repeatable custom colors.
Dental whitener also comes in neat sringes. I wonder if they would work as capacity is small. So brighten up your smile for the NCR and get them free, another reason to smile
it is tedious but for really small batches is still probably the best answer. for 1-3 cc batches it is less fuss than measuring in my experience ( I have a good scale).
Someone brought up the std hobby epoxies that are a 1:1 mix on the predecessor thread. They are certainly easier to mix and use, so why not use them or, better, when to use them? The chemistry of most epoxy resins is such that the true ratio of resin to hardener IS 5:1 some are 3:1. none are truly 1:1. They are also of a fairly low viscosity. This makes them ideal for laminating layers of material. So, how do you make a 1:1 product? You add “stuff” to it to bulk up the hardener quantity. This changes the property of the properties of the base liquid and the end product. The 2 parts of the base material are more viscous and easy to squirt out onto a piece of plastic eyeballing a “that looks good enough” 1:1 ratio. The catalyzed mix stays on the substance to be glued well without running. The product is usually softer, a little rubbery and weaker but good enough. It also does not penetrate wood or cloths as well. None of these changes are necessarily bad, just different. the trade-offs made in polymer chemistry. As one of our Northern British members keeps harping: we don’t need colossal strength in Footy’s so this is fine for many applications. Still, if you want max strength with less weight, a laminating epoxy is better. It can be modified with a myriad of fillers and additives to change such properties as strength, volume, density, viscosity, rapidity of polymerization, color, etc. There is a very good monograph on this on the main West System website -
For those interested in taking the plunge, most of the epoxy manufacturers sell there products in quarts - for resin- and pints - for hardener - that go for around $30 or 3 batches of the usual 5 minute epoxy so not that big an expenditure.
One other thought, I have found that for small batches, less than 200cc’s, that the fast 205 hardener is fine. it has a pot life of 10 minutes and once spread out doesn’t start to gel for an hour - plenty of time for small boat work. And yes, for general Footy assembly work, 5 min hobby stuff is fine.
your basic 5 minute 2 part 1:1 epoxy is about $1 per mixed ounce. you end up spending about the same amount “per ounce” when you buy a quality epoxy, like west or some other system.
kinda like buying a steak…if you can get a filet at the same price as a chuck, why not buy the good stuff…
so if you are spending the same amount anyhow, why not buy the best…
That said. given a bias toward West products - and after using 3 gallons of the stuff on large and small projects over almoat 10 years I think it is great - the next question is: are there equal quality products at lower prices with good accessibility?
I still use the 5 min stuff for assemble esp w Footys.
I too have been known to use 5 minute epoxy when assembling footy parts… Early on I had problems with the 5-min epoxy breaking under stress. Now I mix in West System structural micro-balloons… I’ve not had a part break at the joint since.
I use West for wood, but for everything else I’m very partial to Aerospace Composite Products resin. Excellent wetting and flow properties, albeit at a cost.
Bill,
the stuff from SIG is the standard hobbypoxy that has the aforementioned additives taking the base 5:1 ratio chemicals and bulking them up to make them easier to mix but making it less desirable when you need max penetration, strength, or wet out. What they catalog is fine in the many applications. even their 30 minute stuff is not as strong as a true laminating product.
and get them free, another reason to smile