Aerolite Glues
Dave King
sure of the information, but things might have
changed. Originally I had sent this to the chap
that asked the question of the list, but thought
it might be imformative for someone else as well.
I'm currently working on a Corby Starlet (all wood). Our
equivalent of the FAA is the Ministry of Transport MOT,
about 2 years ago they were activly discouraging the use of
Aerolite or Urea Formaldehyde resins. Last I have heard they
have totaly disapproved of its use in anything. And will take
aircraft out of registry if found to be built with it!
When I was looking around for a project all the old timers
of course suggested using Aerolite. Of course I was wondering
why no one up here was stocking it ;-]. I do have several
articles and some Air worthiness Directives from Canada,
Australia, US etc about the disallowment or non-use of this type
of glue.
Evidently the problem usually starts after a year
or two (and sometimes faster) on aircraft assembled with
Aerolite. What happens is that as the glue ages its resistance
to heat decreases to the point where a normal sunny day
can cause the glue to let go.The damage starts to occur within
a few years but may not be noticed for some time after that.
According to the info I have
the surface temps (the temp of the aircraft structure and
glue joints)only have to be 120° or higher for this to start.
Doesn't seem that low but I have an FAA report showing
that on a sunny calm 85° day the temps would range from
180° on the inside of the upper skin to a low of 130° in the
glue line on the lower skin.
Anyway the things you might want to get a copy of is
FAA Advisory Circular No: 43.13-1A
This is a statement against using Aerolite or UF glues
in aircraft as this Type of glue is considered obsolete
and no longer acceptable.
Adhesive Bonding of Wood - Tech Bul 1512
Airworthiness Advisory Circular No 108 -Wooden Aircraft
and wood glues
Wood as an engineering material,Sterling Pubs
Glues and Gluing, by Bruce Hoadley
Anyway after getting the FAA circular, or any of the others
you'll see that you shouldn't use the UF styles of glues.
I wound up using a MOT approved epoxy G2 Structural epoxy
which is close to T-88 epoxy's but is an apporved adhesive
for airframes here.
Hope this gives you some help, feel free to drop a note.
Dave
=================================================================================
David W.S. (Dave) King
d.k...@cyberstore.ca
"My opinion is not necessarly my own"
"My spellchecker's broke and the dictionary doesn't make sense"
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RTaylor12
(Jeffrey M. Matthews) writes:
>Mosquitos were built with Aerolite, the cure being accelerated by
>heating the molds. They allegedly proved troublesome in the China-
>Burma-India theater due to deteriorating wood joints
Thier were actually two separate problems with the Mosquito in the tropics
(I am assuming you are refering to the De Havilland fighter-bomber from
WWII) only one of which was related to glue.
Early Mosquitos used a casein type glue (is Aerolite such a glue?). In
warm, moist environments this type glue is subseptible to attack by
micro-organisms. This was solved by switching to urea-formaldehyde glues
which held up well.
The other problem, BTW, had to do with the fact that plywood webs of the
spars would shrink/swell with water soakage at a different rate than the
spruce spars themeselves. This increased the internal stress. This was
handled through maintenance and inspection.
Rich
Steve Eldredge
using as the primary adhesive on a Pietenpol, we called the FAA for their
stand on this glue.
Short Answer:
Use it. No problems.
The conversation included a search of all AD's which revealed nothing.
They suggested that the best point of information would be the EAA. That
is where I did all my initial research about Aerolite before commiting it
to an airframe.
As for me and my house we will use Aerolite and not worry.
Steve Eldredge
Stafford William
John R. Johnson <jo...@cwis.siu.edu> wrote:
>After 50 years of using Aerolite glue for aircraft construction NOW they
>decide that it is no good because it comes apart in high temperatures!
>I have some stuff that has NOT been protected from heat or humidity and
>was glued with Aerolite glue thirty years ago. The glue joints are still
>sound and have not loosened or come apart. I have always found Aerolite
>comparable to urea formaldehyde resin glues. It was not FAA approved for
>production aircraft in this country, mainly because after Aerolite came
>out, we didn't build any new wooden aircraft in this country. However,
>it was approved for aircraft construction in Britain.
I originally posted the question about Aerolite. I was motivated
to ask about Aerolite because of:
FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
volume II
Airframe: Non-Metalic Structure
Sept 1993
Chapter 3 Section 1 page 3-4
ii. Plastic Resin Adhesive
"Although 'plastic resin glue' (urea-formaldehyde resin glue)
has been used in wood aircraft for many years, caution should be
used due to possible rapid deterioration (more rapidly than wood)
in hot moist environments or under cyclic swell-shrink stress.
This is the reason urea-formaldehyde is not allowed for
structural building applicationsc such as in laminated beams for
housing. Quality of fit and clamping pressure are both critical
to the achievement of full joint strength. Bond lines must be
very thin and uniform in order to acheive full joint strength.
For these reasons urea-formaldehyde [adhesives] should be
considered obsolete for all repairs. Any proposed use of this
type adhesive should be discussed with the appropriate FAA office
prior to using on certificated aircraft."
My orginal question (still unanswered) was: is Aerolite
approved for homebuilt construction/repair? From the various
responses by builders who are using or have used Aerolite I guess
FAA inspectors of homebuilts are not complaining about Aerolite.
But, is it safe?
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John R. Johnson
such at Fairchild 24's, Staggerwing Beechcraft, and Howard DGA's.
Because of the crossgrain structure of plywood, it is relatively stable
with changes in humidity. Wood normally expands and contracts quite a
bit in the crossgrain direction. That is why you have panels in doors.
Otherwise you would never be able to get a door open on a damp day.
Any cabinetmaker knows that crossgrain glue joints fail after a relatively
short ( few years ) time because of this differential expansion and
contraction in the joint.
Casein glues were the first water resistant ( NOT waterproof ) glues and
are made from casein, with is a milk product. They are a natural product
and a ready extrapolation from other protein glues like the "hide" glue
used to assemble antique furniture and modern violins. Being a natural
protein product that are subject to bacterial attact. I have seen many
older aircraft with wooden structure where the glue joints are falling
apart after 40 or 50 years.
The later urea resin glues are much more resistant to biological attact.
The most common glues in this category are also Water Resistant and NOT
waterproof because they will not meet the "boil test" required for a true
"WaterProof" glue. They are FAA approved for aircraft construction.
This is the old Weldwood or Casco glue you buy at the lumberyard. It is
mixed with water to a heavy cream consistency and applied to both surfaces.
Many aircraft have been built or rebuilt with these glues. I have built
several myself.
The only true waterproof glue of this type is Resourcinal Resin which is
available from Weldwood also. This is a two part glue with a dark brown
resin and a powder component. It is an excellent aircraft glue and is
approved by the FAA for aircraft woodwork.
Both of these glue types are NOT "gap filling" glues and require careful
joint fitting and significant pressure during glueup. They have fairly
short open times ( a few minutes ) and they take usually overnight to
cure.
Aerolite is a resin type glue that consists of a powder that you mix with
water to a heavy cream consistency. This is used in conjunction with a
hardener, formic acid, which causes the resin to quickly undergo a change
and set quite rapidly. It will take an initial tack in seconds. It still
requires some time to cure completely. It is NOT a "gap filling" glue and
does require good fit of parts. It does not require the high clamping
pressure of the urea resin glues, but will not set reliably if you forget
to put the hardener on the other side of the joint.
You put the cream consistency resin on one side of the joint and the
formic acid hardener on the other. When you close the joint, it will
hold itself in seconds. Very little if any clamping pressure is needed
once it takes it first set.
After 50 years of using Aerolite glue for aircraft construction NOW they
decide that it is no good because it comes apart in high temperatures!
I have some stuff that has NOT been protected from heat or humidity and
was glued with Aerolite glue thirty years ago. The glue joints are still
sound and have not loosened or come apart. I have always found Aerolite
comparable to urea formaldehyde resin glues. It was not FAA approved for
production aircraft in this country, mainly because after Aerolite came
out, we didn't build any new wooden aircraft in this country. However,
it was approved for aircraft construction in Britain.
The latest thing for wood construction is the T88 family of epoxys. These
require no clamping pressure and are "gap filling" glues. They supposedly
make up for a lot of slop in joint fitting and last forever. However,
there have not been any aircraft built with them until recently so there
is no actual service history. I have personally had very poor success
with epoxy adhesives. I have found then very critical about mix. An
improperly mixed epoxy glue has all the adhesive qualities of used
ketchup. The older glues are very tolerant of mixture variations.
I am still using weldwood for most structure, and Aerolite where I cannot
easily clamp the joint.
John
Charles K. Scott
w...@cartoon.cartoon (Stafford William) writes:
> My orginal question (still unanswered) was: is Aerolite
> approved for homebuilt construction/repair? From the various
> responses by builders who are using or have used Aerolite I guess
> FAA inspectors of homebuilts are not complaining about Aerolite.
> But, is it safe?
Aerolite is the glue recommended by the designer of the Christavia.
The Christavia has wooden spars and ribs. I chose to use T-88 for it's
ease of mixing, ability to cure in temperatures down to 40¡ and
indifference to exact proportion mixing.
Corky Scott
Raul Blacksten
white Willhold glue.
You are only restricted on certificated aircraft, and you can
use aerolite on certificated aircraft.
In short, yes, you can use aerolite on a homebuilt.
Raul Blacksten
ra...@wavenet.com