Re: [ULF-1] Modern Adhesives vs Plan callouts

From: Member 27
Date: 2018-03-26 21:02 UTC
Message: #0541

Up until thirty or so years ago the very best epoxy for Member 60 as tested by the U.S.D.A
was the formaldehyde based aviation epoxy but I cannot recall the technical aviation name
details. For a decade or so this glue was made available only for US military use to fix
some wooden boat mine sweepers still in the Navy. Those are gone now and the
glue is simply not available in the USA. It may be available elsewhere in the world
but I believe the epoxy technology has greatly improved without formaldehyde use.

Today I believe roughly there are three categories of epoxy
1. laminating
2. structural
3. general purpose

Some other companies may market their brand or various types for their prescribed
special purpose use. I am pretty sure the designer of the ULF-1 did not anticipate
these adhesive developments several decades ago so today you have to do the
research and make the best decision after consulting with the suppliers tech departments.

You must judge which glue joints have the potential to kill you if they fail and I would
use the best glue available based on your research. DO NOT look at the advertising.
I dont know how they get away with it but for instance Gorilla glue says strongest glue
in the world but it turns out to be a foam glue with parts held together by a trillion
bubbles.

Some of the glues targeted for boats could be good.... I dont know for sure but
you generally dont die if a Member 60 joint comes apart in a sailboat or canoe etc.

Perhaps an idea would be to find out what Member 60 glues are locally, reasonably, & financially
available and limit your research to only those. Some builders use two glues....
the expensive one for the "critical joints" and the cheaper glue for all else.

While I have found and experienced that there are some other glues ( beside epoxy)
that are nearly or actually as strong as epoxy ( the Member 60 fails instead of the glue joint )
They require much more precision in application such as joints needing to be clamped
while the glue dries with a perfect amount of pressure in the joint... not too much and
not too little. No so with epoxy. The right kind of epoxy is "gap filling"
and a badly fit joint can be as strong as a precision joint. The wet glue joint
assembly is much easier to accomplish with confidence in the joint strength.

Check in with the U.S.D. A. in their Forest Products Laboratory to see if they might
have done any updates in the last fifteen years re Member 60 glues.

Again. Do NOT use moisture cured polyurethane on anything important.

Member 25

--------------------------------------------
On Mon, 3/26/18, Member 111 <[email]> wrote:

Subject: [ULF-1] Modern Adhesives vs Plan callouts
To: [email]
Date: Monday, March 26, 2018, 4:23 PM

Hi again everyone.

I’ve noticed that the plans call for
aerodux resorcinol urea formaldehyde glue in the
construction of ribs and even the spar cap laminations.
I’ve read of some other builders substituting T-88 for all
adhesives in the aircraft, and wanted to get other ULF-1
builders’ take on the question.

Also, several parts of the build manual
call out “thickened” epoxy, but do not state the ratio
of thickener to epoxy. The use of cotton flakes which I take
to mean flox is also mentioned. Does Dieter intend to refer
to what ratio system 3 or West Systems recommend?

Austin
_______________________________________________
ULF-1 discussion list -- [email]

Subscribe, Unsubscribe, Preferences,
List information:
http://lists.ulf-1.com/listinfo.cgi/ulf-1-ulf-1.com