What I have found out about using T-88,
1) Its not so much whether one epoxy "sticks"better than the other,
so long as the glue join is stronger than the wood, which means the wood
will fail before the epoxy join.
2) T-88 has been used, so they tell me to build quite sustantial
numbers of aircraft, ( in the thousands ), although people here (
Australia ), seem to use the West epoxy, probably because more of it greater
availability through boat building outlets and slightly lower cost. I don't
think anyone actually sells T-88 here locally anymore. If they do, they want
their fare share of money for it.
3) I mix by pouring into a plastic cup which has a ring marked around
the lower extremities to give EQUAL VOLUME. I then also check by using a
digital scale to weigh for the correct mix ratio by weight and find I am
always within 1 gram. Apparently though, T-88 is fairly indifferent to mis
matched mix ratios.
4) When mixed, pour onto a pallette, as the reaction between resin
and hardner generates heat, don't leave in the plastic cup. Although I find
the ambient temperature has far greater effect on the curing time than
pallettes or cups.
5) Surface preparation, people on the krnet will advise of the correct
type of saw and appropriate number of teeth per inch etc. I was a naughty
boy and used a disc sander, I spoke to quite a few people who built there
aeroplane this way and no one had any problems, but I would listen very
carefully to the advise of the krnet as these people have years of
experience building wood aeroplanes, and many people have built more than
one.To get the appropriate saw blade required 12 weeks from a specialist saw
shop while they boated one over from Germany, at, like everything, greatly
over inflated price. ( its for an aeroplane, why else! )
6) Research procedure, use the krnet archives, there is so much
information here, then search peoples web sites, Mark Langfords, Dave
Mullins for example, then, simply ask.
7) Epoxy glue is like axle grease, you may have a perfect dry fit of
parts, put some glue on and it slips and slides all over the place, some
people use staples, others nails, I found dress making pins, you know, the
ones with the plastic bubble on top, are good to keep things in place.
Clamps are great but here they are $30 each, in the US they are much
cheaper. I made my own from some threaded gal rod and wood for about $2
each, the threaded gal also flexes and bends to allow the wooden clamp to
mate with the sloped sides of the kr boat, so you don't have to use tapered
wooden chocks or blocks.
8) If its a hot day, the stuff is runny, if there is any gap in your
join, it will run in the top and out the bottom.Try to orientate your joint
for gravity to have the least effect, which is nearly impossible to do
sometimes, but, something to think about. You can get a beautiful glue
fillet by running you finger along the squeezed out glue along a glue line
when the glue has started to cure, just after the runny stage and just
before the tacky stage is the best time to do this I find. Strangely enough,
it doesn't seem to want to stick to your finger.
9) I was told to wipe the excess epoxy off the joint but found as the
glue cured, I always ended up with a slight hollow along the glue line, so I
leave the excess and sand it off later, its very easy to sand.
10) I always keep a test sample of the glue, just pour some mixed glue
into a plastic cup and let cure to see how well it sets, and I keep a test
wood/glue sample as well, take three pieces of spruce about 2 inches long,
lay them side by side, orient in a north south direction for example, slide
the middle piece northwards for half its length, glue the remaining
overlapping areas, lightly clamp, and let set for about a week, then place
in a vice, with the north most piece on one vice jaw, and the opposite two
ends on the other vice jaw, and compress in the vice. If you have a good
join, then the wood will fail everytime. A lot of my test pieces suffer a
compressive failure across the grain of the wood while the glue line stays
intack. I have tried test pieces with T-88 where the faces have been disc
sanded, sanded with wet and dry, sandpaper, no preparation at all,
contaminated with sweat, oil, coated each surface with wood dust, even
bruised the mating faces with a ball pane hammer. I have even glued samples
together with the glue so tacky you could hardly spread the glue, and the
wood still fails everytime. This does not mean you dont prepare the surface
properly though.
11) Waxed paper is great for acting as a barrier to glue, I found out
the hard way that one layer of paper is not good enough, at least two are
needed, but that could be due to the poor quality of the local waxed papers.
12) If anything I have said is wrong or disputable, then I am sure
many people will advise of the correct procedure or events. I have done
pretty much all the boat section with T- 88 and it seems to do the job. I
would not say that mixing is any problem
13) If I were building the boat section again, I would make a simple
jig to assemble on to gaurantee accurate alignment of the side frames, while
many people have built hundreds of kr's using nothing other than the plum
bob described in the plans with great results, one thing the plans do not
say is to ensure your workbench over its whole length, is perpendicular to
the plum bob for accuarcy. When it comes to jigs, ensure you use sustantial
pieces of timber or whatever if you are layying up the side frames, which
are firmly fixed to the bench, its surprising how much a fraction of give in
a jig block can cause errors to accumulate. Measure six times, go away and
have a think about it, measure again, and then cut once!
13) This may be a bit long winded but plenty of people have provided
me
with much useful information, so the least I can do is relate my
experiences!
14) And one last thing, if you submit anything to the krnet, ensure
that you use the correct units to differentiate between millimetres and
thousandth's of an inch.
Chris.
----- Original Message -----
From: <bdazzca...@aol.com>
To: <kr...@mylist.net>
Sent: Wednesday, January 25, 2006 6:54 PM
Subject: KR> any better resins to use?
> Hi netters,
>
> I am about to start on my "boat" and ordered everything I think I
> need
> to finish this stage of the project... I bought the T-88 glue and bought
> some
> of the WEST SYSTEM EPOXY... Aircraft Spruce was saying that this is easier
> to
> mix than the AEROPOXY system epoxies.... TRUE OR FALSE? Is there a better
> composite epoxy out there then West? If so, what is it? Who makes/sells
> it? Also
> I was looking through Mark Langfords online manual thing and saw that he
> was
> using mircoflux.... what is it and where do you get it? I couldnt find it
> in
> the Aircraft Spruce catalog. Any advise will help thanks.
>
>
> David Swanson
> bdazzca...@aol.com
> _______________________________________
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>
