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.IE,Carbon,Eglass or my favorite,S2 cloth.
The manderal is reusable and will last a long time with a bit of
care.This
will spread the cost of the manderal over many tubes and keep you out
of hot
water with the wife/SO in your life.
The manderal is covered with a piece of sheet mylar.The mylar
acts as the
carrier for the glass tube and slides off the manderal leaving the
manderal
intact for reuse.
The manderals that I use are made from full length phonelic
coupler tubes that
I buy from RedArrow hobbies.
I make the manderals 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.
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 IE 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.IEa 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
possiable.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 manderal for use.I have found that to make
it easier to
remove the glass tube from the manderal I developed the next step of
adding a
reinforced center to the manderal.
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 manderal.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 manderal
for the
next step.
Set the cleaned EMT in the center hole of the epoxyed in ring and
place the
manderal in an upright position with the first ring facing down on the
floor
and the EMT in the middle of the manderal.mix some 2 part foam and pour
into
the manderal,quickly place the top ring in the manderal 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 manderal with 2 part foam untill its
full.cut
off the excess expanded foam and enough inside so the second end ring
can be
epoxyed in place.
I draw 2 lines down the length of the manderal about 180 degrees
apart with a
permenent marker pen.one is for laying out the mylar carrier sheet and
the
other is for lineing up the first wrap of cloth to keep it straight on
the
manderal.I also place lines at 38 and 50 inches (centered of course)
around the
OD of the manderal to help keep the cloth centered while rolling the
tube.
Tom
I went into great detail for the construction of
the manderal 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 manderal 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 manderal and a way to remove the rolled airframe after its
cured(more on removal in a moment).
Heres what makes it all so easy,the mylar carrier on the
manderal.For all
intents and pourposes the carrier is just a mylar tube that you make to
fit
over the manderal to keep any epoxy from getting on it.(the manderal)The
carrier will slide off of the manderal and be
stuck to the inside of the airframe.
The carrier is the same length as the manderal,and has about a 1
inch overlap
on the OD.
Cut the sheet mylar the same as the length as the manderal,in my
case 60
inches long.The width is determined by the OD of the manderal,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 manderal.
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 pourpose)through the 1 inch EMT in the manderal 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 manderal using one of the lines
as a guide to
keep it straight and paralell.Starting in the center hold the mylar
with one
hand and snug it up to the manderal 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
manderal tape the seam in several places to hold it in place.DO NOT
TAPE THE
MYLAR TO THE MANDERAL!!only tape the mylar to it's self at the overlaped
seam.When you have the carrier so that it's flat and smooth against the
manderal and it slides on the manderal 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
manderal 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
Back from lunch so
lets finish up the manderal.
Mylar comes in many different thicknesses 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 egalss tape and epoxy.Allow to cure
and try
the rings on the nose cone and see how it fitsYou will,for the most
part,be
using the .002 mylar.The phonelic coupler material varies from run to
production run a small amount.some of the manderals 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 manderals here that are from the same vendor but use
different thicknesses of mylar to get a good fit.It happens so be
prepared.
If you went to the extra time and trouble to fill the manderals
as i suggested
they will last for years and are very tough.I stand the manderals 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 manderal is as good as new.Just a piece of coupler thats 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
manderal 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 psi 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 manderal and bunch
up in
different spots.looks really bad.
Next figureing out the amount of cloth and how to determine wall
thickness of
the finished airframe.
Tom
OK you now have a manderal with a carrier in the
size that you want to make the
airframe in.
Saftey 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
mixxing 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 manderal supported in some way so
that you can turn the
manderal 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
manderal 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 manderal 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
manderal 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 manderal so that one of the lines ,the ones
that run
the length of the manderal 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 manderal 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
manderal 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 manderal 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 manderal 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 manderal 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
manderal.
I have a birthday party to go to.I'll post removal and finishing
info when I
return.
Tom
I so sorry to have taken so long to make this last post on the airframe