>
> Hi, I've purchased a partially complete Europa a little over
> a year ago and had to put it storage until my garage/workshop
> was re-vamped in order to build the kit. It is now to a point
> to where I can start moving my kit into it and start working on it.
>
> I have question about the different devices used to measure
> the epoxy and wondering what most builders have done in the
> past. The cheapest of course is to make the Europa mechanical
> balance which should be no problem (is it quick and easy to
> use during a layup?) but I'm leaning towards either a Ohaus /
> Sartorius digital scale with a resolution of 0.01gm (do I
> need that much precision or can I get away with a lower cost
> 0.1gm unit?) OR a ratio pump like a Glenmarc Portionator
> MBT-JR from A/S which is the most expensive of the all the
> options (is it worth the cost for ease of use?).
>
> I live in Canada so I will be using Aeropoxy resin (100:27 by
> weight or 3 to 1 by volume).
>
Roger,
You will find people who swear by each of these approaches, so I won't try
to tell you which is best. We used digital scales with 0.1 gram resolution
and found them to be quite satisfactory, though I wouldn't recommend less
resolution. Our original scale (an Ohaus Scout) died after a few years of
excellent service, and we have used a couple of cheaper models since. For a
staggering selection of scales, check out www.americanweigh.com.
Even the cheapest pocket-size scales would probably have good enough
accuracy, but you need a large enough weighing platform to hold your mixing
cups easily. (You will often be in a hurry when weighing epoxy, and spills
are a real pain.) Be sure that the scale stays on for long enough to zero
the cup weight, weigh the resin, and then weigh the hardener (even with some
interruptions) before it turns off to save its battery. Not a problem with
AC power, but some of the small scales with tiny batteries get in a hurry to
shut down.
Keep in mind that absolute accuracy is not needed for mixing applications,
only good linearity. This can be tested precisely even without accurate
calibration weights. Just weigh anything and note the result. Then replace
the first item with something else, and zero out the reading. Adding the
first item to the platform should result in exactly the same reading that
you got when weighing it by itself. The two objects together need only to
remain within the scale's range.
Remember also that you will frequently have to mix Redux/Araldite 420/???
with good precision, and it's ratio will be different from the layup epoxy,
so a mixing pump or fixed 100:27-ratio balance won't do this job. A digital
scale is a bit like the digital level or close-quarters drill that you buy
for one specific job, and then find that you use it for many other things.
Dave DeFord
N135TD
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