Creating Fiberglass Tubing
By Tom Cloud TRA 109
Part 1
Well here we go again. I really need to get
a website going for this info with a
few pics added in for fun.
My name is Tom Cloud and I'll post some info here to show you
how to roll up a
glass airframe tube in what ever material that you choose to use for
the
construction of the tube. I.E., Carbon, Eglass or my favorite,
S2 cloth.
The mandrel is reusable and will last a long time with a bit
of care. This
will spread the cost of the mandrel over many tubes and keep you out
of hot
water with the wife/SO in your life.
The mandrel is covered with a piece of sheet mylar. The
mylar acts as the
carrier for the glass tube and slides off the mandrel leaving the mandrel
intact for reuse.
The mandrels that I use are made from full length phenolic coupler
tubes that
I buy from Red Arrow hobbies.
I make the mandrels 60 inches long so that I can use either 38
or 50 inch
cloth widths and trim to 36 or 48 inch long tubes.
I use sheet mylar in either the .002 or .005 thickness as the
carrier for the
airframe, the mylar thickness is determined by rolling a small test
piece using
glass tape to test fit to a nosecone to see how tight it fits.
Part 2- Mandrel construction
I make my mandrels all 60 inches long to allow the
use of either 38 or 50 inch
wide material.
The full length couplers are usually 36 inches long in the smaller
sizes and
48 inches in the larger sizes (6 inch and up) so this means that you
need to
join 2 lengths of coupler together to use the same process that I use.
I cut a second coupler tube to the correct length to make up
60 inches I.E. a
full 36 inch coupler and the second coupler cut to 24 inches long.
To join the 2
pieces you'll need to make a split tube coupler. I all ways make
the joining
coupler twice as long as the tube OD. I.E. a 4 inch (3.900) tube would
have a joining
coupler 8 inches long.
It is plain to see that you need to keep the 2 pieces as straight
as
possible. I join the 2 pieces together using White glue to allow a
long working
time and the pieces laid in a 3X3 angle iron to keep them straight
while the
glue sets.
This makes the basic mandrel for use. I have found that
to make it easier to
remove the glass tube from the mandrel I developed the next step of
adding a
reinforced center to the mandrel.
I make two end rings from 1\2 plywood scraps (cheap) with a center
hole to
clear a 60 inch length of 1 inch EMT. Epoxy one of the end rings in
an end of
the mandrel. Clean the length of EMT with a solvent like MEK
to remove the oil
from the surface and rough the EMT with course sand paper.
Take the second end ring and place 3 or 4 push pins placed in
the side of the
ring near the top as a way to keep it from falling inside the mandrel
for the
next step.
Set the cleaned EMT in the center hole of the epoxyied in ring
and place the
mandrel in an upright position with the first ring facing down on the
floor
and the EMT in the middle of the mandrel. Mix some 2 part foam
and pour into
the mandrel, quickly place the top ring in the mandrel to keep the
EMT
centered and at the same time hold the EMT with a finger down so that
it will
still be flush with the first ring. The expanding foam WILL try
to push the EMT
up as it cures. Finish filling the mandrel with 2 part foam until
its full. Cut
off the excess expanded foam and enough inside so the second end ring
can be
epoxyied in place.
I draw 2 lines down the length of the mandrel about 180 degrees
apart with a
permanent marker pen. One is for laying out the mylar carrier
sheet and the
other is for lining up the first wrap of cloth to keep it straight
on the
mandrel. I also place lines at 38 and 50 inches (centered of
course) around the
OD of the mandrel to help keep the cloth centered while rolling the
tube.
Part 3- Mandrel construction, 2
I went into great detail for the construction of
the mandrel only to help
avoid any questions. Basically you want to have a length of coupler tube
about a
foot or so longer than the widest material that you want to use,
You need the
extra length on each end to turn the mandrel and not touch the wet
cloth that
you are rolling the tube from. The center piece of EMT gives
you a way to
support the mandrel and a way to remove the rolled airframe after its
cured (more on removal in a moment).
Here's what makes it all so easy, the mylar carrier on the mandrel.
For all
intents and purposes the carrier is just a mylar tube that you make
to fit
over the mandrel to keep any epoxy from getting on it. (the mandrel)
The
carrier will slide off of the mandrel and be stuck to the inside of
the airframe.
The carrier is the same length as the mandrel, and has about
a 1 inch overlap
on the OD.
Cut the sheet mylar the same as the length as the mandrel, in
my case 60
inches long. The width is determined by the OD of the mandrel,
in this case
3.90. The OD (3.90) X 3.14(12.246) plus about a 1 inch over lap
to seal the
carrier, a 13 inch wide piece of mylar 60 inches long is needed.
The mylar needs
to be cut square, 90 degree angles, the make it easy to wrap the mandrel.
The carrier is held together with plain cello tape.
use a length of 3\4 inch EMT between two supports (I use 2 saw
horses made for
this purpose) through the 1 inch EMT in the mandrel core. Tear
off 5 or 6 small
pieces of tape to hold the mylar in place while you make the carrier.
Place the piece of mylar on the mandrel using one of the lines
as a guide to
keep it straight and parallel. Starting in the center hold the
mylar with one
hand and snug it up to the mandrel with the other hand. Put a
small piece of
tape on the seam to hold it in place. Keeping the mylar flat
and smooth on the
mandrel tape the seam in several places to hold it in place.
DO NOT TAPE THE
MYLAR TO THE MANDREL!! Only tape the mylar to it's self at the
overlapped
seam. When you have the carrier so that it's flat and smooth
against the
mandrel and it slides on the mandrel with out any slop it's time to
tape the
entire seam. Start at one end and pull out a foot or so of tape
from the
roll, use one hand to hold the tape roll and the other to smooth
the tape as you
go down the seam. Seal the entire length of the seam and make
sure the cello
tape is flat and smooth. Leave the small pieces of tape in place
that you used
in the start and just go over the top of them.
You now have a mylar tube that will slide up and down the mandrel
but is not
loose or sloppy. If you have wrinkles in the mylar carrier you
will have ridges
in the completed airframe. It wont hurt anything but it just
looks bad when
cured.
More later when I get home from taking the kids out for lunch.
Tom
Part 4- Mandrel construction
Back from lunch so lets finish up the mandrel.
Mylar comes in many different thickness' and can be found
online at
Tapplastics.com and other online vendors as well. The common
sizes that are
listed online seem to be the .002,.005 and the .014. The latter
is very heavy
and stiff, its also hard to work with on a small tube.
I usually use the .002 or .005 anyway so it all works out in
the end.
To determine what thickness mylar to use its easiest to roll
a test piece with
eglass tape as the material and make a glass ring to test fit
to the nose
cone.
Before making the carrier tube take a piece of .002 and .005
mylar about 6
inches wide and long enough to make a "mini" carrier of each thickness
and roll
up a test ring from 4 or 5 wraps of eglass tape and epoxy. Allow
to cure and try
the rings on the nose cone and see how it fits. You will, for
the most part, be
using the .002 mylar. The phenolic coupler material varies from
run to
production run a small amount. Some of the mandrels will use
the .002 mylar but
a few will be smaller on the OD and require the .005 mylar to roll
a slightly
larger tube. I have mandrels here that are from the same vendor
but use
different thickness' of mylar to get a good fit. It happens so
be prepared.
If you went to the extra time and trouble to fill the mandrels
as i suggested
they will last for years and are very tough. I stand the mandrels
on end in a
corner of the garage and have had a few "accidents" over the years.
Dings and
divots can be filled with a mixture of microspheres and epoxy and sanded
smooth
and the mandrel is as good as new. Just a piece of coupler that's
not filled
with the foam can be ruined beyond use, been there done that.
If you want to use a vacuum bagging setup you need to fill the
mandrel to
keep it from collapsing under the pressure of the vacuum. I know
that 14 pounds
a square inch doesn't sound like much, but look at it this way. If
the material
was laid out flat it would take a steel plate over a foot thick to
exert the
same pressure as a good bagging job at 29 inches of mercury (14 pi
in air
pressure}
I never had much luck with bagging the airframe and always got
wrinkles in the
finished tube. The wraps of cloth move around on the mandrel
and bunch up in
different spots. Looks really bad.
Next figuring out the amount of cloth and how to determine wall
thickness of
the finished airframe.
Tom
Part 5 - Rolling the airframe
OK you now have a mandrel with a carrier in the
size that you want to make the
airframe in.
Safety First!!!! Always wear a pair of latex or nitrile
gloves and a long
sleeve shirt, and have a fan moving the air in the area that you are
working
in. I work in the garage with the door open and a fan behind
me blowing the
epoxy fumes outside. In a matter of a few minutes after putting
the epoxy in a
mixing vessel my nose will start to run from a reaction to the
resin/hardener. It make no difference what brand that I use I
still have some
type of reaction to the material. Don't think that you wont get
to this point
after years of exposure to the resin,you will if you don't work smart
from the
start in using epoxys.Again saftey first and avoid any problems.
A resparator with HEPA filters is a good investment,the long
sleeve shirt will
keep the epoxy off of your arms if you bump in to the wet cloth.
You already know what you want the airframe rolled from be it
carbon or Eglass
or something inbetweenWe need to determine how much cloth is needed
to do the
layup.
Measure the thickness of the cloth with a cheap dial caliper
or a mic.This
thickness will determine how many wraps are needed to get the wall
thicknees
that you want to end up with.
To figure the length of the piece of cloth thats needed take
the OD of the
manderal(in this post it's 3.90, a common size)and multiply by PI(3.14)
to
arrive at the length needed for ONE wrap(3.90X3.14=12.246 inches).
Lets say that the material is.010 thick and we want to end up
with an .060
wall tube(most nosecones have a sholder for this thickness)so that
would mean
that we need 6 wraps of cloth to make the tube.
12.246 inches per wrapX 6 wraps means that we need a piece of cloth
73.476
inches long.round this off to 73 1\2 inches long and then we add about
2 inches
to this figure to allow for the tube to grow in diameter and provide
an over
lap at the seam when compleated.So a piece of cloth 75 1\2 to 76 inches
long is
needed to roll a 3.90 airframe with an .060 wall.Easy.
You already have your mandrel supported in some way so
that you can turn the
mandrel but it stays in one place.I use a piece of 3\4 inch EMT on
two saw
horses,remember the 1 inch EMT in the manderal,the smaller EMT passes
through
this and gives you the support needed.
Wax the mylar carrier with a paste release wax and buff
off the excess with a
paper towel.
Set up everything that you need to do the layup on a table next
to the
mandrel BEFORE you start the layup.On my rolling table I have 4 or
5 throw
away resin brushes,4 or 5 2 quart mixing tubs,3 or 4 squeegees an Exacto
knife
with a sharp point tip and several dozen paper towels pulled from the
roll.The
cans of resin and hardner are on one corner and have pumps in them.As
a note
punch a small hole in the top of the cans to vent them.It helps keep
the pumps
from "spitting" and also keeps the pumps from dripping material.If
you drop a
brush or squeegee while rolling,leave it on the floor and pick up a
new one and
keep going.
Put the cloth on a cardboard tube or another length of EMT and roll
it up and
place it behind the mandrel away from the floor so that it stays clean.
Put on the safety items and mix some epoxy in a tub.Use the brush
to coat the
mandrel between the end lines all the way around the manderal.You should
have
a heavy coat of epoxy on the carrier the same width as the cloth if
you have
done it correctly.Turn the mandrel so that one of the lines ,the ones
that run
the length of the mandrel of course,is facing up.lay the cloth end
on this
line and between the end lines,use your brush to move the cloth where
you need
to so that the cloth is straight and matches the lines.
Start rolling the cloth on the mandrel by turn it a small amount
at a time
and brushing down the cloth as you go.Only add more epoxy to the spots
that
aren't wetted out with the brush,they will look white or not as wet
as the rest
of the cloth.Don't use your hands to smooth out the cloth,just the
brush at
this point.Your hands will leave ridges in the tube.Only use your hands
to keep
the material running true with the guide lines on the ends of the
manderal.leave no dry areas in the layup,you can't go back later and
touch it
up.
After you get about a wrap and a half of cloth wraped on the
mandrel pick up
a squeegee and smooth out the cloth and tighten it up at the same time.This
will force the excess resin UP through the cloth and remove any small
airvoids.
Turn the mandrel small amounts at a time and use the squeegee
to press the
cloth smooth and flat,use the brush to add more epoxy to any dry spots
as you
go around the manderalOnly handle the cloth at the outer edges with
the gloved
hands to keep it running true on the mandrel by pulling the cloth on
the side
that needs to be trued up.
Keep doing the above steps untill you get almost to the end of
your clothUse
the brush to smooth down the last few inches of cloth
Don't brush across the end of the cloth whenyou get there.This
will pull the
cloth apart and leave threads on the out side of the tube,just use
the brush to
push down the cloth at the seam.
Roll the mandrel on the support and look for any dry spots and
small
airvoids,you shouldn't have any,BUT,if you have a dry spot use the
brush to
stipple more epoxy into the cloth(use the brush corner and work the
epoxy into
the cloth)becarefull not to move the cloth and cause an airvoid(bubble
in the
wetted out layup).Small airvoids can be opened by using the exacto
knife point
and poke the void.Use the brush end to push the cloth down again.
The tube when rolled around will look an even green color with
a few shiny
spots.The shiny spots are excess resin and need to be removed.Take
a paper
towel thats been folded several times and touch it to the shiny
spots to blot
up the excess resin.Go around the tube several times while the excess
epoxy is
bleeding itself through the cloth and remove it.
After you are happy with the layup.Leave it alone!!let it cure
on the
mandrel.
I have a birthday party to go to.I'll post removal and finishing
info when I
return.
Tom
Part 6- Removal from the mandrel and a few tips
I so sorry to have taken so long to make this last post on the airframe
construction thread.I have been very busy and also the WTC has been
in my mind
instead of this,again sorry.
The mylar carrier/fiberglass airframe will slide off of the mandrel
in most
cases without too much effort if you made the carrier correctly to
begin with.A
lot of times you can hold the manderal/airframe in your hands and give
it a
sharp jerk and it will start to slide apart,then you just hold the
airframe
with one hand and pull the mandrel out the rest of the way.
If you rolled the tube a bit too snug you might need some one
to help pull the
tube off the manderal.After many tubes I made a simple removal system
that
works every time.This is just another length of 1 inch EMT the same
length as
the mandrel and a length of 3\4 inch EMT 2 feet longer than the manderal.The
3\4 inch EMT acts as a guide to keep the mandrel and the second length
of 1
inch EMT alined.
To use the removal setup just slide the 3\4 inch EMT into the
mandrel and
then slide on the second length of 1 inch EMT.Set the end of the second
length
on the garage floor and pull down on the airframe,things should slide
apart
without to much effort.If you got super carried away with the squeegee
when
rolling your airframe and its stuck on the manderal,just raise the
mandrel up
a foot or so and hold the airframe and slam it down on the second length
of 1
inch EMT like a slide hammer.A few sharp raps like this will remove
the
airframe from the mandrel.
When the airframe\mylar carrier is free from the mandrel
you can remove the
mylar tube by starting at one end and peel the carrier away from the
airframe
with your fingers.Once you have an area free on the end,slide a long
wooden
dowel down the inside of the airframe between the carrier and the airframe
untill the dowel is exposed on both ends of the airframe.Push down
on both ends
of the dowel at the same time and the mylar carrier will pull away
from the
glass tube.Turn the airframe a bit and repeat untill the mylar if free
all the
way around the inside of the airframe.Keep the mylar depressed and
pull it
out.The carrier will slide out with no effort,even a small area that
has not be
peeled away from the carrier will hold it in the airframe,just keep
working
untill the carrier is free of the airframe.
You now have the airframe(YEA!!) the mylar tube and the manderal.Carefully
slide the carrier back on the mandrel and rewax and roll more airframe.
I always remove 1 inch of the airframe from each end to play
it safe.
I have made at least a hundred lengths of airframe in sizes from
54mm to 11.41
inches in diameter using the method that I have described here in this
thread.It works and you no longer need to buy phonelic tube,just roll
it in
glass and enjoy.
A quick tip is to square up the cloth on both ends before you
start rolling
the tube.You can do this by pulling the loose threads of fiberglass
on the end
untill a thread pulls clean all the way across the material.take your
sissors
and trim the end fuzz untill you have about an 1\8 of an inch exposed.
Also remember to work the epoxy UP through the cloth,this will
help control
the amount of epoxy that you use and will keep airvoids out of the
finished
airframe.You want to use about 50% by weight epoxy.IE your cloth for
the tube
weighs 12 ounces total,you want to use about 6 to 7 ounces of epoxy
to roll the
layup.Remember that a squeegee is your best friend in rolling.
Plain weave cloths are the most stable and make good tubes.Start
simple with
open style cloths called boat fabric to learn with.Once you have the
hang of
the rolling,buy some tight weave,plain.The tubes will be lighter and
stronger.Also roll the tube from a single length of cloth,it makes
a stronger
airframe.
Carbon is super strong and you can roll a straight carbon tube
easy
enough.Remember that it lacks the mass for a good altitude.Save the
carbon for
the high velocity birds.
Enjoy!!!!
Tom Cloud
TRA 00109
NAR 34140
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