Today's Message Index:
----------------------
1. 04:39 AM - Re: Steve from Owings, MD (chase143(at)aol.com)
2. 09:24 AM - Glue and Varnish Test (dgaldrich)
3. 10:26 AM - Re: Glue and Varnish Test (John Francis)
4. 11:51 AM - Re: Glue and Varnish Test (biplan53)
5. 01:09 PM - Re: Glue and Varnish Test (tools)
6. 07:08 PM - Re: Glue and Varnish Test (dgaldrich)
7. 07:34 PM - Re: Glue and Varnish Test (tools)
8. 09:09 PM - Cable Symmetry (John Woods)
9. 09:13 PM - Re: Saturday afternoon patrol (taildrags)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Steve from Owings, MD |
Hello Axel,
Wow, thank for the kind words. We've met you a few times over the years, and I
am very glad you will be there again this year, in one piece (give or take a few
pins) ;-). Hope your new project is coming along!
Regards,
Steve
--------
Steve
www.mypiet.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397073#397073
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Glue and Varnish Test |
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
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Glue and Varnish Test |
I believe it would be a mistake to proceed with your project based on these results.
My understanding is that although a strong bond may appear to have been
made, the epoxy has adhered to the varnish and not the wood. Varnish will eventually
break down as the moisture content of your wood changes seasonally and
the wood expands and contracts because of it. Time will weaken the joint.
Have you checked with the manufacturer about these tests?
John
--------
John Francis
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397110#397110
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Glue and Varnish Test |
I just read in the Bible(Tony's books) not to get ahead of game and varnish anything
to be glued later. I am not trying to be a rain cloud but I trust someone
who has been there and done that.
--------
Building steel fuselage aircamper.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397116#397116
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Glue and Varnish Test |
What needs to be glued to the ribs after you have varnished them? The leading
edge sheeting or the leading edge itself?
I can't see any reason why you would have a problem. I'd sand any portion of the
rib that needs glued for some key, and then wouldn't worry about it.
My dad dipped all his ribs just like you did on his Hatz, no problems. It's a
similar wing.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397128#397128
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Glue and Varnish Test |
I forgot to mention that the varnish on the wood was 12 years old and was taken
from a previously flying airplane. With a great deal of difficulty, I pried
off the pieces that remained on the plywood. None exhibited the failure mode
you're describing. I've redone some 90 year old varnished furniture (I grant
you not SPAR varnish) that was not giving up without a serious fight. The point
is properly applied varnish of most any kind is a b++++ to get off.
I think for use on the leading edge plywood, this is not an unreasonable test.
This ends up being a low stress joint in any event due to: 1) the fact that all
the ribs will be held parallel by a combination of the drag/antidrag wires
and the fabric rib lacing and 2) there is very little, if any, "side load" from
aerodynamic forces.
As a reference to the amount of stress on leading edge fairing, take a look at
Aeronca Chiefs and Champs. Their leading edges are .016 or .020 aluminum held
on by a relatively small number of short wood screws.
Please note that I am NOT recommending using varnish under glue for anything structural.
What I am suggesting is that the dunking technique DOES insure that
the entire rib, even the nooks and crannies behind the gussets, is varnished
and protected from moisture. The "conventional wisdom" that you can't or shouldn't
use glue on varnished surfaces may NOT apply to this specific kind of stress
with these specific epoxies.
That's what experimentation is for and why I offered this data.
Dave
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397149#397149
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Glue and Varnish Test |
I agree with you. Epoxy is recommended to glue all sorts of non porous things
together, don't know why wood with the grain sealed would be any different. Key
is the key, needs to be sanded some is all.
I've never seen varnish release due to seasonal movement. I do believe some very
old varnishes eventually oxidize to the point they flake off, just like the
paint on old machines.
Varnish being spar or not shouldn't have anything to do with it's ability to hold
either, spar varnish means that it's got UV inhibitors is all.
I like the idea of dipping the ribs because of the difficulty of ensuring you've
painted all the surfaces. It's EASY to miss places.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397151#397151
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
Hi Steve from Owings,
I just had a look through your construction web site (www.mypiet.com) and it is full of great detail.
The one which caught my eye was the Cable Configuration Thoughts and in particular
the slides showing the elevator cable configurations.
I must agree with you that Setup B is the one to aim for to avoid those loose cables
we hear about on flying examples.
The key there is ensuring that from the control column all the way to the control
horns, everything is symmetrical.
By symmetrical, I mean in the neutral position, the control column, idler bar and
control horns are vertical or at the same angle from vertical AND the cable
connection points on each of those items are equidistant from the pivot point.
By equidistant I don't mean that all three items have to have the cable attached
at the same measurement, they can be different, but for each item the cable
should be the same measurement from the pivot point. Does that make sense?
This is why setup B works.
The same would apply to all the cable controlled surfaces.
Symmetry is good! When moving things are symmetrical, they move together in harmony
and all is good.
Hope this information is found to be useful.
Best regards,
John Woods
Perth, Western Australia
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Saturday afternoon patrol |
We ARE going to get that airplane onto the cover of a national publication! It's
a beauty.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397155#397155
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|