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Article 8298 of alt.surfing:
Path: sol.ccs.deakin.edu.au!munnari.oz.au!news.uwa.edu.au!rhino!rd005.251.54.192.in-addr.arpa!conrad
From: conrad@jtec.com.au (Conrad P. Drake)
Newsgroups: alt.surfing
Subject: FibreGlass FAQ - part 1 of 2
Date: Mon, 17 Oct 1994 05:22:05 GMT
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Someone (well C. Myron Ware cmw@hobbes.larc.nasa.gov, actually) asked for the 
FibreGlass FAQ.  So here is the current revision, in two parts.
Conrad Drake

Changes from 0.1 - clarified the basic steps
===== Fibreglass repair FAQ  0.2 17 Oct 94 ===== Part 1 of 2
This FAQ looks at (Part 1) fixing dings in "conventional" surfboards and 
(Part 2) some other materials and other uses for GRP.

Thanks to (at least) for comments, advice and comments that I've ruthlessly 
plagerised without permission.
        tele1@eternity.corp.sgi.com (Eric N. Valor - Ding Repair Suggestions)
        ttweed@ucsd.edu (Tom Tweed - setting fins)
        flynn@cats.ucsc.edu (Eric Flynn - building a board)  
        dmp@bmesun1.MCG.EDU (David M Parrish - aircraft epoxies)
        Charles.K.Scott@dartmouth.edu (Charles K. Scott - more aircraft stuff)

1. Fibreglass for Surfboards
------------------------------
   Dings
   Ding Repair Suggestions
   Setting Fins
   Building a Board
   GRP - Fibreglass and resin sources
2. Other Stuff
--------------
   Epoxy and Other Materials
   Some Books
   Composite Workshop Review
   Fibreglass Update
        **
1. Fibreglass for Surfboards
------------------------------
Dings
-----
For small holes - pre-mix microballoons with resin (50:50 by volume). Add catalyst 
as normal: ie 7-8 drops MEK per 20ml of resin (more if cold, less if hot weather).

For big holes - clean out the hole, cut a chunk of foam to fit and stick it in 
with resin. Shape (180 grit) and re-glass. 

Reglassing - (torn or missing glass). Remove all torn bits & feather the edges.  
Fill any holes or depression with balloons/resin.  When hard, sand smooth (80 to 180 
grit). Cut glass cloth about 1cm too large (as you need a good join & some will get 
sanded off) and put in place.  Mix a batch of resin.  Use a bit of sponge/squegee 
to apply resin to totally wet the glass. Then use the sponge to remove all excess.  
Do this by dabbing/wiping with the sponge, periodically squeezing out the sponge. 
The finished surface will have the texture of the cloth.

Once this has set, sand (w' #80-180) to remove rough spots and to smooth the join 
between old & new. This also keys the resin for the hot coat.  

Mix another batch of resin, this time 'hot' (extra MEK - 1 extra drop per 20ml). 
This will gell really quickly (5-10 minutes).  Brush on just enough to 
provide a smooth finish.  When set, sand smooth with progressively finer paper 
(180, 240, 400, 600 then cutting compound) until either bored or satisfied. 
If you cut through to the 'glass, you _should_ repeat the process.
[Mals tend allways have this second gell coat, and are highly 
polished - OTOH competition boards are often not even sanded at all.]

Resin, MEK and microballons can be bought from most shapers.  Offcuts of foam 
and cloth can usually be scrounged from the same sources.

The process I've described is time consuming and most shops don't do that when 
they "fix" a ding.  They mix up a hot batch of resin with lots of 
microballons and colour, fill the hole & sand.   It's quick (only one setting 
time vs 3 or 4).   It's also weak.  Some at least mix some chopped mat in to give 
it some structural strengh, but you've still got a future source of leaks.

Oh, Masking tape, Saran/Gladwrap and Aluminum foil can be used to hold resin in place/shape 
while it gells.  Personally I like alfoil.

Ding Repair Suggestions (Eric N. Valor)
---------------------------------------
(horror story deleted)

First off, fill the holes with foam.  Most surf shops that do ding
repair may have some around that they'll flow you.  Either that or
find a shaper in the area.  But do NOT fill in a hole with just resin;
it makes for bad weight and an ugly repair.  Cut out the hole until
it is nice and even, then cut a piece of foam to shape and insert. 
Make sure it matches up evenly or you'll get ugly lines.  

btw:  that powder is most probably microballoons; small glass bubbles
with air.  They space out the resin and make it a bit lighter.  

Ok, next:  Use 10-12 drops of catalyst per ounce of resin.  I don't know
how big your dings are, so I don't know how much resin to use.  Just
eye it.  Stir the catalyst in for about 60 seconds to get a good mix.
Then coat the bottom of the "filler foam" with a bit of resin and insert
into the hole.  Then cover with a sheet of fiberglass (cut to shape of
the hole) and pour a little bit of resin on top and smooth it out
over the hole and the existing glass (you'll sand off the excess later).
Put a piece of Saran Wrap over the top and let set overnight.  

You can use 80 grit sandpaper to start the process, then once you start 
to get down to the existing glassjob, switch to 100 or 120.  To finish
off, use 400 wet/dry (and use a bit of water).  That should do you.

Fins are a bitch to set properly, as placement of the fins absolutely
determines how the board will respond.  Make sure you get right and
left fins for the twins (yes, there are sides) and a normal single
for the rear (this is a tri-fin, right?).  Angle them out a few degrees
from straight up-and-down, and toe the front edges of them in just a
bit.  This is the hardest part, as they have to be braced while the
resin dries.. it's a bitch and I've only done it (badly) once. 

Eric N. Valor

Setting Fins -(Tom Tweed)
-------------------------

A trick that some of my glasser friends use is to set the fins with a bead of 
hot-melt glue right on the bottom- have the front and back toe-in marks 
penciled on the board, and a little cardboard template cut for the camber 
angle (usually about 5 degrees outside of perpendicular to the bottom).  Slam 
the fin down while the glue is hot right on your marks, slap the camber 
template up against the side and hold it steady for 15-30 seconds while the 
hot glue solidifies.  Voila!  You're ready to rope and glass them in without 
the obstruction of tape braces, etc., holding them in place.  Don't bump them 
too hard, though, it's not that strong before glassing....

Tom Tweed- La Jolla, CA         e-mail: ttweed@ucsd.edu 


Building a Board
----------------
From: flynn@cats.ucsc.edu (Eric Flynn)
Subject: Re: Building a board...
Date: 24 Jul 93 05:40:52 GMT

In article  pa_warren@Merrimack.edu (Warren Crossfield) writes:
>
>Anyone here build their own board(s). If so, any tips (materials) for a
>novice builder?

Well it looks like this is a good time to give you all the update on how my
board-building project went.  First, a little review.

I have been surfing an old 60's style Team Becker.  It's 7'4", kind of half-
way between a longboard and a bonzer.  It has a round tail, and a very wide,
round nose, with a large concave.  These characteristics give it nice
watch-catching ability, even in small surf, good handling, and it nose-rides
like a champ.

The board I just got finished building is based on this design, and has almost
all the desirable characteristics of its predecessor.  I chose to copy this
board because I like it a lot, and the guy who owns it wants it back!

I went to Monterey Bay Fiberglass and purchased all the materials necessary
which ended up costing about $150.  I then had a shaper here in town shape
the blank, which cost $70.  I was fortunate enough to run across one of the 
guys who used to glass for the Haut,and he basically taught me how to laminate.
I paid him for his time, bought him lots of beer, and ran him around town for
a couple weeks ( he doesn't have a vehicle ) in retrun for his help.  In the 
meantime, we have become good friends, and this worked out so well we plan
to build another board.

The next board will be a 9'3" shaped by Doug Haut, and glassed by me and Jeff
Thompson.

One other stroke of good fortune:  Jeff happens to be a personal friend of
Jimmy Phillips ( of Pack-Your-Trash fame ), he talked Jimmy into designing
a custom logo to put on my board.  I paid Jimmy for the work, but I can tell you
that I got it at a very handsome discount.

I took some pictures of the new stick before I waxed it, and plan to use the
scanner at work to digitize a few and will post them to the surfing GIF mailing
list.  The board came out really nice, and it surfs like a dream.
:-)))))))  Yaahhooo!!

So I guess I ought to address the questions asked at the beginning of the
article.

First, it helps _worlds_ if you can find someone experienced to help you.  My
board woulda been a giant resin barge if I hadn't had Jeff there to bail me
out of some really sticky ( literally! ) situations.  Failing this, at least
get someone to let you watch them glass a side or two so you can see how
laminating is done.

Second, you will need a place to work.  A spacious garage is what I used.
You will need an enclosure of some sort for the hot coat and gloss coat,
otherwise the resin may do nasty things like split or get bugs in it.

Next, you will need the following equipment and supplies:

Glassing stands
Grinder or Sander/Polisher - I use a Makita 9207SPC
Paint brushes 2,3,4"
Wide wall-papering brush
Rubber Squeegee
Sanding discs
   60 grit, 100 grit Aluminum Oxide
   400 grit, 600 grit Wet or Dry
Jars or #10 cans
Canister-style organic vapor rated respirator - IMPORTANT

X# gallons of resin - I prefer Cargill, its stronger than some others
1 gallon of acetone
masking tape - don't get the cheap kind, get 3M paint masking from a paint store
Single-edged razor blades
X# yards of fiberglass cloth

I'm not going to try to explain the whole process, but here are some helpful
 hints in general:

A plastic trash bag masking taped around your waist make a cheap disposable
apron.  And speaking of disposable, go down to the thrift store when buying
clothes you plan to wear whlie glassing.

Soak your squeegee and paintbrushes in acetone overnight before glassing.
They will be much more pliable and easy to work with.

Tape down a couple layers of tar paper (roofing cloth) on the floor so you 
will not leave any post-Columbian artifacts thereon.

Have two pairs of scissors: one exclusively for cutting fiberglass cloth,
and the other for cutting sandpaper and other such things.

When you cut the cloth around the edge of the blank, leave a 2-3" lap,
begin careful not to leave any dangling strings.  These will be a real
pain later if you don't eliminate them now.

Use the wall-papering brush to smooth out the fiberglass on the blank.
This helps to avoid the cloth "floating" off the blank.

Laminating has three basic steps: 1) saturate the cloth 2) squeegee out the
excess and 3) work out the cloth to a burlap texture.  Start your pour near
the middle and work toward the ends of the board.  This is where it gets hard
to explain without someone holding your hand and showing you what to do.
The basic idea is to keep the squeegee vertical and apply just enough pressure
to spread the resin and saturate the cloth.  Then, using a bucket to catch the
excess, take firm even strokes the entire length of the board, squeezing the
excess resin out of the cloth.  No doubt there will be some dry spots, so use
the resin you catch to thoroughly soak them, and squeegee out the eexcess again.
Once this is done, take medium firm strokes the length of the board, starting at
the middle.  The key here is to leave the squeegee in contact with the surface
as much as possible.  If you pick it up, you will create a puddle.

The hot coat and gloss coat follow in much the same way, only you use a brush to
apply them.

After the hot coat, use the grinder to sand the board smooth.  The fins and 
rails should be done by hand.  Then wash the board with a soft rag soaking
wet with acetone, much as you would wipe down a table, catching the debris
by folding the rag.  Do the same with your bare hand while the acetone is
still evaporating.  You will be able to feel when the surface is clean.

After the gloss coat, you have the option of polishing it.  I personally think
boards surf just fine unpolished, but a mirror finish on a showroom board
will sell faster to be certain.

NOTE: ALL of the organic chemicals used in surf-board building are KNOWN
carcinogens.  Although many people have had long and happy board-building
careers and never gotten cancer, please use all due caution when dealing
with these volatile, corrosive and highly toxic chemicals!
Buy a respirator like the one mentioned above and WEAR it!s

Well, if you all want more gory details, feel free to mail me at
flynn@cats.ucsc.edu, or post a question in reply.  I'm pretty new at this, 
and as I mentioned above this is far from a complete description of the process,
but it should at least give some idea of what you need to know.

Happy board-building!

ERic

GRP - Fibreglass and resin sources
----------------------------------
Fibreglass is more properly known as Glass Reenforced Plastic (GRP). 
   Most surfboards are built using 1950's materials - plain woven glass cloth and polyester 
resin with Methyl Ethyl Ketone peroxide catalyst on a polyurethane foam blank, 
reenforced with a single wooden stringer.

You'll have to pay for your resin, hardener and micro-balloon filler.  If you know a local 
shaper you should be able to scrounge some off-cuts of foam and glass cloth.  Rovings (basically 
fibreglass 'rope') are usually bought, but if you're cheap, pull apart some cloth.

Boat manufacters usually use either chopped strand mat - which is much weaker than cloth or a 
sort of spray gun which pulls in fibreglass rope, chopping it up and sucks up resin, mixes it 
with catalyst and the chopped strands before spraying the lot out.  Usually into a mold.

Speaking of molds, watered down PVA (White wood working) glue apparently works well. YMMV.


===== Fibreglass repair FAQ  0.2 17 Oct 94 ===== Part 2 of 2
2. Other Stuff
--------------
Epoxy and Other Materials
--------------------------
   Not suprisingly, materials have come a long way since 1950. Almost everyone knows 
about Carbon fiber and Kevlar.   Not so well known are the changes in the foam and resin.
Most high-tech fibreglass jobs (ie commercial and homebuilt aircraft, and some sailing boats)
 are constructed using a two-part epoxy, with a stronger glass fibre.  

Some surfboards have been made, using a special closed cell (to stop waterlogging) polystyrene 
or polyvinylxloride (PVC) foam, both in the West Coast of the USoA and on the east coast of Oz. 
The few reviews (Aust.Surfing life had one recently) seem impressed by the weight and strength
of the boards - down to 2.5kg for a 6' board you can jump on.  One other advantage is that they 
can be repaired with 2-part expoy glues (such as Araldyte).
 
There are rumoured to be people making kevlar (reef-proof) boards in South West Oz.

Many of the newer resins come preimpregnated in carbon/glass/kevlar cloth (to order) and require 
autoclaving (cooking) to set.  

I'm not going to go into detail on my own, but rather I'll include a few articles from 
regular rec.aviation.homebuilt contributors.  Tune in there for more info (unfortunatley
they don't seem to have an all singing/all dancing composites FAQ).  Also try rec.autos.racing.* 
rec.boats,.building and rec.models.rc 

Strengths of materials
----------------------
Tm Tensile Modulus (Giga Pascals 1gpa = 10^9 Newtons/m^2 ~= 140,000 psi, i think)
Ts Tensile Strength (Giga Pascals)
D  Density      (grammes per cubic centimeters)
Material        Tm      Ts      D
E-glass         77      2.5     2.54
S-Glass         85      3.5     2.48
Graphite AS4    190     2.8     1.80
Kevlar 49       130     2.8     1.45    - note kevlar is shitty in compression.
Aluminum        70      .14-.6  2.7

Note these are unidirectoinal free fibre, with no expoxy.  Reality is only 1/4 as good.
There are lots of different grades of each material.

Some books - various people
----------
(I haven't been able to find these at my local library - I haven't tried the Uni yet.)

"Graphite Fibers and Filaments" by M. S. Dresselhaus et al, Springer 
Series in Materials Science 5, (Springer-Verlag, Berlin, 1988), chapters 1, 2, 
and 12.

ASM Engineered Materials Handbook
Volume 1: Composites
ISBN 0-87170-279-7 (v. 1)
(c) 1987 ASM International

'Composite Construction for Homebuilt Aircraft' Jack Lambie's 

"Composite Basics". Andrew "Bud" Marshall 

"Composites Design", by Steve Tsai   

"The Behavior of Structures Composed of Composite Materials"
        J.R. Vinson and R.L. Sierakowski        

Composite workshop review (by Daid Parrish)
-------------------------
This weekend, I attended the  composite  basics  workshop  put  on  by 
Alexander  Aeroplane  in Griffin, Georgia and I thought that others on 
the net would like to hear my impressions on the workshop and  what I 
think are some very useful techniques presented.

First  off,  a  little  about  the  workshops  and  in particular, the 
instructor for the composite  workshop,  Stan  Montgomery.  Currently, 
Alexander  is  running  three  -  two day workshops on basic composite 
construction, welding and fabric covering that are  held  in  Griffin, 
Syracuse,  Oshkosh,  Trenton,  Bloomington,  Houston, and Lakeland and 
will  soon  be  adding  workshops  on  other  topics  like  wood   and 
metalworking.  Stan  also  mentioned the possibility of three and five 
day advanced composite workshops and another workshop on finishing.

Stan Montgomery is a very good speaker, has a masters in chemistry, so 
he knows his resins, and was a military pilot and has  built  numerous 
homebuilt  aircraft, so he knows airplanes and composite construction. 
He's also VERY passionate about composites. This has caused some -  er 
-  disagreement  with illuminaries such as Dick Rutan, but anyone that 
can make a spar shear web out of heavy, finely  woven  bid  glass  and 
achieve  40% resin, BY HAND, and still use peel ply should be listened 
to seriously.

For those that don't have the foggiest what I just  said,  some  extra 
information.  The  spar  carries  the  weight of the plane through the 
wings, and the spar web carries the load between the upper  and  lower 
spar  caps, forming a strong and very stiff I-beam inside the wing. In 
fiber/resin composites, the fibers carry  the  load  while  the  resin 
keeps  the  fibers  together. If there is too little resin, the fibers 
don't stick together as well, and the part is weakened.  If  there  is 
too  much  resin, which is much weaker than fiberglass, then the resin 
starts taking some of the load, and produces a weaker product.

The problem is, most homebuilders think that if resin is good, more is 
gooder. But anything above 60% resin, 40% glass,  is  actually  weaker 
than  50-50  or  40-60  and is both heavier than it should be and more 
expensive, since any resin, from $20 a gallon polyester to $100 plus a 
gallon epoxies are expensive to buy.

Bid glass is a fiberglass cloth that has nearly equal number of fibers 
both along and across the bolt of cloth. Peel ply is  a  light  weight 
and  finely  woven  nylon  or polyester cloth that is used as the last 
layer in a layup. When peeled off, it fractures the resin surface  for 
a  stronger bond with subsequent layups without using sandpaper, which 
damages the glass fibers on the surface.

Back to the workshop. 

The syllabus had an ambitious  schedule  that  we  were  unfortunately 
unable  to keep up with because of time constraints. Even saying that, 
the most important points and procedures were hit upon. The first part 
of Saturday was a lecture that covered  what  composites  are,  safety 
with  composite  materials,  and  various techniques used in composite 
construction. Most of the rest of the two days was hands  on  building 
of  a short section of a canard with interspersed discussions on other 
composite techniques, including a hands on vacuum bagging.

The  construction  of  the  canard  started  with  a  block  of   blue 
polystyrene  foam  and  a pair of templates, so we had to hot wire out 
our own canard cores. Hot wire cutting the foam is a very intense  few 
of  minutes  where  you  have to be aware of wire temperature, cutting 
speed, wire drag, tension against the template and exactly where  your 
partner  on  the  other  side  of  the wire cutting frame is at on the 
templates. This is done by numbers around each template that one calls 
off and the other gives faster or slower cues as the pair cuts  around 
the templates. 

Once cut out, the leading edge just in front of the spar cap recess is 
hot  wired  off  and  the  front  edges of the trailing edge part were 
rounded so there are no sharp edges for the spar web to go over.  Once 
rounded,   the  spar  web  area  is  filled  with  epoxy  filled  with 
microscopic glass balloons or Alexander's superlite filler.  Both  are 
very light in weight and prevent raw epoxy from soaking into the foam.

A  quick, unsolicited ad for the superlite epoxy filler. This stuff is 
a very light weight epoxy filler that can be used in place  of  either 
Bondo  or  microballooned  epoxy  and  was developed by Stan. It has a 
density at least half that of Bondo, doesn't shrink, is very sandable, 
and contains a built in chromate conversion for use  on  aluminum.  It 
also  contains  an agent that helps tiny entrapped bubbles rise to the 
surface and burst so pinholes are greatly reduced. The only thing I've 
tried it on so far is to fill an aluminum nose gear fork, and  it  has 
very  nice  working  properties. I'm definitely going to try it when I 
start finishing the wings on my Velocity.

Anyway, next Stan showed us how to a layup with 40% resin,  yet  still 
be  fully  wetted  out.  First  he  cut  out two ply of glass cloth to 
approximately the right size, weighed them, and then placed them on  a 
piece  of  plastic and poured on a weighed amount of epoxy to an exact 
40% resin, 60% glass by weight ratio. He then  put  another  piece  of 
plastic over the layups and worked the epoxy into the glass. To evenly 
distribute the epoxy, he would occasionally fold the glass and work it 
some  more,  making  sure  not to crimp any folded glass and carefully 
applied heat from a hair drier to thin the  epoxy  out.  When  he  was 
done, the layup was totally saturated with no white streaks indicating 
dry spots. Once this was done, it was applied to the canard core and a 
sheet of peel ply was squeegeed onto the surface, further reducing the 
epoxy content of the layup.

According  to  Boeing,  this  is  impossible. They can achieve a 37-63 
ratio, but only by using  multi-million  dollar  autoclaves.  While  a 
40-60  ratio takes quite a bit of experience, I was able to do a 50-50 
layup with no problems on my first try. Wake up guys. Homebuilders are 
at least ten years ahead of anything that comes out of  the  big  iron 
plants. The only thing that may come close would be the formerly Beech 
Starship,  and  it was designed by the homebuilder's homebuilder: Burt 
Rutan.

I do have one nit to pick with Stan on epoxy though. Being a  chemist, 
he  wants  exact  molecular ratios of resin to hardener, therefore the 
only way to do this is by weighing both the resin and hardener  before 
mixing instead of using an epoxy pump, which does do ratios by volume. 
For  me,  working alone, all that extra weighing of resin and hardener 
just takes to much effort and  time.  Assuming  the  pump  is  working 
correctly,  the  volume  ratio is based on the weight ratio of the two 
components and  the  only  weight  ratio  change  would  be  from  the 
DIFFERENCE  in the expansion rates of the components with temperature. 
Since most epoxy systems has a 5% margin  of  error,  I'm  not  overly 
concerned about this difference, but I am going to retest my pumper at 
various  stroke  lengths.  Also,  if  you  have  a scale that can only 
register to 2 grams and you're doing a batch of ten  or  twenty  grams 
for  a  small  layup,  you  may  end  up with an error greater than 5% 
anyway. Knowing the weight of the glass and the  epoxy  used  in  most 
layups I totally agree with.

Another  neat  technique he showed us was with unidirectional spar cap 
tapes. The tapes are only a few inches in width and  produce  a  thick 
layup.  The  rovings are held together with a sparse cross thread, but 
any weaving in a glass cloth reduces the strength.  What  he  did  was 
find  the single fine thread on the edge that held the cross thread in 
place and removed it after the tape was placed on the canard. Once  it 
was removed, the cross thread was carefully removed, leaving straight, 
flat  fibers  in  the  spar  cap.  That  one  even surprised the epoxy 
manufacturer that sat in on our workshop on Sunday.

Recommended tools were scales, layup rollers and  a  hair  dryer.  The 
scales  are  used  for weighing the glass and epoxy to calculate their 
weight ratios. The rollers are for working  out  air  bubbles  and  to 
distribute the epoxy. He was against using a paint brush to remove air 
(a  process  known  stippling)  because  it tended to break up bubbles 
instead of removing them. Layup rollers are shaped  something  like  a 
small paint roller, except the roller is plastic or aluminum and has a 
grooved surface that allows entrapped air to escape. The hair dryer is 
probably  his favorite tool. With it he can drastically thin the epoxy 
to improve wetting of the glass and speed up the setting time.

Another  point  he made was that all epoxy layups should be post cured 
at an elevated temperature. All epoxies have what's called  the  glass 
transition temperature, where it looses it's strength. They all have a 
maximum  transition  temperature,  such as 190 degrees Fahrenheit, but 
the actual temperature that it weakens is only thirty or forty degrees 
above the temperature the resin was cured at. If it's 60 degrees  when 
you  make  a  wing, the wing will sag when the skin reaches only 90 or 
100 degrees. Not good if you fly down to Sun 'N Fun!

To  fix that, after the initial cure is done, Stan post cures the part 
by heating it to 130-150  degrees  for  a  few  hours  with  the  part 
supported  so it doesn't bear any weight. This can be done by painting 
the part with black tempera and leaving  it  out  in  the  sun  or  by 
putting  it  in  an  'oven'  made  out  of cardboard boxes and a small 
forced air heater.

All in all, I really enjoyed the workshop. There  were  some  problems 
that I think were due to the newness of the workshop and limited time, 
but over all, it was well worth the $150.

I finally got to try the techniques from the workshop, and  the  short 
answer is: It's harder than it looks.

That's  not  really a fair statement, as I didn't really allow for the 
differences in my application. My first trial was the installation  of 
my  canard  bulkhead  into  the  fuselage. To do that, the bulkhead is 
aligned plumb and square with the proper station in the  fuselage  and 
then  taped in place with 2 ply of bid cloth cut at a 45 degree angle. 
The tape goes about an inch and a half up on the bulkhead and down  on 
the fuselage, both fore and aft, along the full joining line.

  So  I used a string to find approximately what length of bid tape to 
use for the four sections. (Fore and aft and left  and  right  of  the 
nose  gear  door cutout.) I cut the tapes to length, weighed them, and 
poured an equal weight of epoxy over them on plastic  film.  With  the 
layup  roller, I spread the epoxy out. With narrow bid tapes, this can 
be a bit difficult without the tapes distorting, but the roller did  a 
good  job  as  long as I didn't move the epoxy ahead of the roller too 
quickly. They're rather expensive, but I think they do  a  better  job 
than stippling with a paint brush.

  Once  wetted out, I cut the film to rough size and carried the whole 
thing over to the plane and put it in place. One thing though. The bid 
tape conforms to the surface much better than the  plastic  film  that 
keeps it from stretching, so you have to carefully peel the cloth from 
the  film  as you put it in place. Once in position, I used the corner 
and layup rollers to press the cloth in place and  covered  that  with 
peel ply squeegeed in place.

  When I peeled the peel ply off the next day, there were streaks were 
there  was  no  epoxy between the bulkhead and the bid tape, mostly on 
the vertical surfaces of the bulkhead. The problem has to do with  the 
surface  of  cured triax cloth that was used on the bulkhead. In triax 
cloth, there are three layers of fiber bundles, stitched together like 
a quilt instead of woven, giving it  greater  strength.  But  it  also 
makes  the  surface  more  uneven, with valleys between the bundles of 
glass fibers. The streaks I saw were the valleys that had  not  filled 
with resin.

  My  mistake  was not heating the layup with a hair dryer to thin the 
resin out. I had even prewetted the triax with resin on one side as  a 
test  before  taping  and it didn't seem to make much difference. As a 
second test, I cut out a 3 by 3 inch piece of bid and laid it over the 
original streaked tape and out onto  the  bulkhead,  this  time  using 
heat.  When  I  peel  the peel ply off this time, the dry streaks were 
OVER the bundles of glass, indicating  I'd  used  too  much  heat  and 
pressure  and  had worked too much resin out of the cloth. The valleys 
were filled nicely though. Ah well. Live and learn.

One thing I feel fairly certain about is  the  actual  best  resin  to 
glass  ratio  will depend heavily on the weight and weave of the cloth 
and how much work you want to put into thoroughly wetting it out.

The next time I try layups like this, I'll try the other technique  he 
showed us. In it, he marked off the size and shape of the layup on the 
plastic film with a Sharpie pen and cut the cloth to approximately the 
correct  size  and shape. After weighing the cloth, he poured an equal 
weight of epoxy directly on the film  and  spread  it  evenly  with  a 
plastic bondo squeegee. He then laid the cloth on the spread epoxy and 
worked  the epoxy into the cloth. When the glass was completely wetted 
out, he used a razor blade to cut both the cloth and plastic  film  to 
the marked line, leaving a layup ready to be used.

Within  the  next couple of weeks, I'll be ready to skin my left wing, 
so I'll be reporting again on how  well  the  layup  rollers  do  when 
working on (very!) large areas of glass.

David Parrish 

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