Today's Message Index:
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1. 11:10 AM - Re: Glue and Varnish Test (Ben Charvet)
2. 04:19 PM - Re: Glue and Varnish Test (Bill Church)
3. 09:34 PM - slow days on the list (taildrags)
4. 10:09 PM - Re: slow days on the list (Mark Roberts)
Message 1
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Subject: | Re: Glue and Varnish Test |
I don't have my plans in front of me, but I bolted my leading edge to
the ribs,using #8 or #10 stainless screws and I'm sure that wasn't an
original idea. I believe I glued it too. I think your testing proves
you have nothing to worry about.
Ben
NX866BC, flying for 3 years.
On 3/26/2013 12:24 PM, dgaldrich wrote:
>
> Several days ago, I revealed that I had "dunked" my ribs in varnish. Someone
pointed out that the varnish might pose a problem with future glue. In order
to determine whether I'd have to sand all the nose portions of the ribs, I did
an experiment, or rather two.
>
> I had some turtle deck stringers that were varnished and almost 1/4 inch thick
-- .220-.245 inch -- that were laying around so I ripped them into 1/2 inch
pseudo cap strips and glued 6 inches of them to a piece of 1/4 okoume plywood.
That length was chosen to approximate the amount of rib that would be glued
to the plywood leading edge. Since I had some mixed up, I used West System epoxy
as well as T-88. Glued 3 each for a total of 6. Also had some douglas fir
that was approximately .285 thick so I ripped some of that into 1/2 inch strips
and also glued them to the same piece of 1/4. After the glue had cured for
24 hours, I marked the sticks at 6 inches out from the plywood, put the plywood
in a vice and hung a water bucket at the 6 inch mark.
>
> I chose this particular test, rather than a tension or compression arrangement
with the thought that the primary strain on the glue joint would be a side load
on the nose part of the rib where it's nominally glued to the leading edge
plywood.
>
> After hanging the water bucket on the cap strip, I added water to it until the
wood or joint failed and then weighed the bucket on a bathroom scale. Did it
for the twelve samples and the results are pictured below. ALL of the test
pieces failed in the same manner. They all broke at the "hinge" point where the
cap strip met the plywood. NONE of the glue joints failed.
>
> Conclusion: Since this was more of a qualitative experiment than a serious quantitative
one, the primary one that I reached is that a T-88/West System glue
joint with varnished wood is strong enough for the intended purpose and I don't
have to sand off my ribs.
>
> Observations: The Douglas fir pieces were approximately 25 percent thicker than
the Sitka and yet failed at an average of 70 percent higher load. This lends
credence to the AC 43-13 note that Douglas is stronger and those that use
it could probably use slightly thinner longerons and diagonals in the fuselage.
>
> Notes: This test was for ONE failure mode and the data samples were not tightly
grouped so the quantitative reliability is not very accurate and any calculations
should be based on much more rigorous testing. Since the glue joints
did not fail, this is confirmation that West System is suitable for at least this
sort of application.
>
> Pictures: Glue 1 is the board before testing. Glue 2 is the varnished pieces
after failure. Glue 3 is the Douglas fir pieces after failure. The numbers
are the weights at failure.
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=397093#397093
>
>
> Attachments:
>
> http://forums.matronics.com//files/glue_3_734.jpg
> http://forums.matronics.com//files/glue_2_176.jpg
> http://forums.matronics.com//files/glue_1_717.jpg
>
>
--
Ben Charvet, PharmD
Staff Pharmacist
Parrish Medical center
Message 2
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Subject: | Re: Glue and Varnish Test |
Ben,
Maybe this is where you got the idea.
BC
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397238#397238
Attachments:
http://forums.matronics.com//files/le_189.jpg
Message 3
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Subject: | slow days on the list |
There doesn't seem to be much going on, so I'm going to stick my neck out and post
a time-waster. Not just for you... for me, too. It's about what I did at
the hangar last Saturday. It was a beautiful day and I would have gone flying
if Scout had wings (still sitting on tables waiting to be cleaned and re-mounted
on the fuselage). I would have cleaned and re-mounted the wings except that
I need to climb down into the front cockpit and re-make the connections from
my fuel tank and shutoff valve to stop a slight weeping that seems to be producing
a fuel smell in the cockpit. I would have worked on that except that
earlier that day a little back spasm hit me while I was lifting a heavy box off
of an upper shelf and I was worried that I might not be able to get back out
of the front cockpit if I crawled down in there with my tools and my back complained.
I would have worked on something else on the airplane but what I ended up doing
was opening the hangar doors wide (my hangar faces west), rolling a shop stool
out into the sun, and drinking a mocha coffee while I tried to figure out what
to do next.
Since it's annual time, I could have pulled the air filter off the carb, cleaned
and re-oiled it and been done with that. I could have pulled the plugs since
I have the cowlings and cooling eyebrows off the engine, cleaned and gapped
them, and been done with that. I could have cleaned, primed, and painted the
new cooling eyebrows since it was plenty warm enough to paint. I could have...
I could have... but I sat in the sun and drank coffee.
A Baron fired up and taxied out. A Cherokee 180, same. I looked over at my shelves
and saw a pull-down electrical cord reel that I've been meaning to hang
from the overhead structure so I can use tools anywhere in the hangar, but I would
have had to move the ladder over there and I was worried about my back.
I could have filled a bucket with soapy water and washed the bottoms of Scout's
wings, but I figured the water was too cold to do a good job cutting through
the grime. So I sat and sipped coffee and looked around the hangar and thought
about all the things I could be doing.
Before long, I went over and arranged things on my shelves so I could find them
better, and I did a pretty good job of taking more things out of boxes left over
from the move. I found some missing items (like a big box of AN hardware
that I knew I had somewhere). I found the squawk list from the last annual, which
will be useful in starting the list this year. I arranged some loose tools
and moved some things to their proper places from where they had been laying
on workbenches or on shelves, but not much else. Mostly I sat around the hangar,
looked around at things I should do and could do, but didn't do much except
drink coffee and enjoy the sunshine. What a waste of a good Saturday afternoon.
do not archive
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397251#397251
Message 4
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Subject: | Re: slow days on the list |
Actually Oscar, it sounds like a perfect afternoon for a low and slow pilot! Not
too much rushing around, just taking life as it comes to ya, in a hanger, at
an airport, where there are airplanes.
Could it get better than that??
When are you coming to San Luis Obispo? Isn't it this summer for graduation?
Mark
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397252#397252
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