First you have to remove the old plexy hopefully without any damage on
the original frame. Than probably fill the surface to provide smooth
contact. Glue the plexy to the frame. Cut it to fit and probably fill
and send before paint. Than you still have to sand and polish the new
surface. You shouldn't damage the new plexy during the whole procedure.
I don't say it's 50 hours, maybe more;)
/Jancsika
"Roger Worden" <rwo...@aol.com> wrote in message
news:KBXlf.28425$7h7....@newssvr21.news.prodigy.com...
--
Hartley Falbaum
"Roger Worden" <rwo...@aol.com> wrote in message
news:KBXlf.28425$7h7....@newssvr21.news.prodigy.com...
* As Tim pointed out, mounting canopies takes time and experience to do
right. As with most things, the best results are had the second or
third time you do it. Your best bet is to find a shop that's done it
before so you don't end up paying for the shop's education.
* Though the work is fussy, takes rather a lot of time to do properly,
and requires a good eye and somewhat delicate touch, it can be done in
the home workshop environment. If you've done good-looking bodywork
with Bondo and paint, you can probably mount a canopy. At very least,
you can probably do some of the prep work. But consult with your A&P
before starting. If you've done owner-assisted annuals (the best kind,
I think) and have a good relationship with the A&P, they might be OK
with it. Or, they might not. Ask first to avoid surprises.
* Usually the preferred bonding techniques and materials are shown in
the maintenance manual. You can also pick up some general hints by
looking at the tech notes for different gliders. The DG tech notes in
particular show a neat trick for using foam tape for controlling
squeeze-out of the bonding resin.
* Bonding the transparency onto the frame without having the frame on
the fuselage is very risky, and I've seen it result in an
embarassing-looking assembly that barely fit onto the glider at all. I
definitely don't recommend it. Canopy frames tend to be fairly
lightweight parts, and a lot of the strength and stiffness of the
canopy assembly comes from the transparency. Also, the frame is often
painted black so it sometimes gets hot and takes on a warp that only
shows up when it is separated from the transparency. All the big
companies have tooling that emulates the cockpit rail that they clamp
the frame to when bonding in the transparency.
* Acrylics are much more crack-prone when they're cold. If you feel
tempted to work acrylics such as Plexiglas, don't do any cutting,
drilling, or filing operations unless the plexi itself (and not just
the room it's in) is warmed up to at least 70 degrees F and preferably
in the 80s F.
* If the preferred bonding resin isn't shown in the tech notes and you
have to choose your own, I suggest _not_ using an epoxy thinned with
butyl glycidal ether (as are most laminating resins) - it crazes the
acrylic. George Applebay has recommended Epon 828 kicked 2:1 with
Versamid 140. I haven't tried it myself, but I will.
* Last time I checked, the manufacturers were paying 500 to 1200 Euro
for transparencies of various sizes in lots of ten or so. Contrary to
popular belief, Mecaplex quite often has the best prices in Europe for
the raw transparencies. The big markups start when it leaves Mecaplex
or wherever, and the glider manufactuer and all the middlemen and the
shippers and insurers get their cut. That's just the way commerce
works.
* Right now acrylics sheet prices are spiking to follow oil prices, so
be prepared for some degree of sticker shock.
* Anybody who wants is welcome to develop their own tooling and place
an order for ten or so and become part of the game themselves. But I
don't think that you can contact Mecaplex directly and order Discus or
ASW-27 canopies. Usually, the glider company develops the canopy
tooling and then hands it off to the transparency company with the
agreement that they will only make transparencies on that tool for that
glider company.
* Anybody who ever thinks of making their own canopy transparencies
should count on not getting usable results until somewhere between the
third and sixth attempt. It's a tricky business, and the major players
guard their trade secrets jealously. Way more often than not, the most
cost-effective way of getting a good transparency is to buy it from a
reputable firm such as the sailplane manufacturer.
Thanks, and best regards to all
I have recently installed a new canopy on my Phoebus C and it took
about 60 hours. Im sure if I did a second it would require less time.
Im aware that 40 hours is about standard for an installation if the old
canopy has been removed.
If you are thinking of a new canopy due to cracks, you may be
interested that there are ways to repair cracks that removes the crack
and the repaired area is much less apparent.
Good luck,
Mike
"Jancsika" <janc...@nowhere.org> wrote in message
news:dn9ij0$cqe$1...@news.al.sw.ericsson.se...
I would not bet on buying a completely new canopy from Grob, because:
1. First of all I do not think that the economy of scale holds for
glider manufacterers since the number of aircraft built is quite low.
Next to that, the canopy-glass is made by Mecaplex another company. The
glass is said to be especially difficult to make and thereofre it is
expensive.
2. Furthermore, Grob will most probably also need your fuselage when
installing a new canopy because of fit and new, or other, hinge
locations
3. Grob is not out of business as an aerospace company, but my guess is
that they haven't built gliders for over 15-20 years now. Spare-parts
come from LTB Lindner now (southern Germany).
I am very sorry for you, but I have to agree with the posts above.
Replacing your canopy will not be cheap. But if you have just one clean
crack or a piece that has come out then I would suggest to glue it
back, although making that pretty is not at all easy
Kind regards
Diederick Joosten
The Netherlands
> Factory labor to assemble new things in
> an repetitive process is usually less
> expensive than a craftsman in the field
> repairing a similar unit...
>
> ... or maybe the typical economics don't
> hold true in this market.
The latter, quite definitely. Even in the highest-volume glider
"factory," craftsmen doing things onesey-twosey hold the central part
of the process. I think that none of the big players make more than a
few hundred units a year. That may sound like a lot, but it's a far cry
from the tens of thousands or hundreds of thousands of units you'd see
on a car or motorcycle production line.
The bottom line is that even in the factory environment manufacuring
glider parts is an expensive proposition. It may be less expensive than
field repairs and fabrication, but not by much, and business and
transportation expenses more than make up the difference.
Yes, it is definitely faster and more efficient to make a canopy and
frame assembly in the factory. They have the tools and processes and
procedures in place to do it correctly in the fewest possible hours.
However, with production rates so low, and with the installed base so
small, it simply does not make economic sense for them to dedicate part
of their production to spares manufacturing. For a lot of the parts,
they'd end up with a lot of expensive shelf space dedicated to
expensive spare parts for which there is no definite demand. That makes
sense when there are tens of thousands of units with an established
history of spares requirements. But with a few hundred units in the
field there simply is not enough data to build a realistic model of the
spares requirements.
Another problem is that, here in the US at least, the factory is a long
way away. That means expensive transatlantic shipping of a delicate
assembly.
I heard a rumor that some guy is working hard at establishing a
"factory" for a sleek-looking glider right here in the US. ;-)
The facts so far: I have been amazed at how many "original" parts I
have been able to buy for my 30 year old glider (Schreder RS-15) from
this same guy! Keep it up, Bob.
Regards,
-Doug Hoffman
http://www.sportaviation.org/magazine/2004_summer/canopy.pdf
Still, it is a fair amount of effort for one canopy.
Tom
Tons of good posts here. FWIW, I've done a couple of canopy repair jobs
(not complete replacements), and everything mentioned elsewhere holds
true:
- It's doable if you are average to above-average handy with tools and
finishing work.
- Figure out how long you think it will take. Then triple that
estimate.
- It can be very satisfying.
- The downside risk is pretty high.
I'm probably in the "above average" category in terms of experience
working with filler,epoxy, and finish sanding, and I've managed to get
results ranging from decent to spectacularly poor. If the canopy is
already in pretty bad shape, then attempting a home-grown repair or
refurbish may not be such a bad thing. You might learn something, and
the worst that happens is you have to get the new canopy after all.
Erik Mann (P3)
Scott.
Spectr Scott, I been trying to get ahold of you. Drop me an email when
you can.
Thanks, Bob K.
> I heard a rumor that some guy is working hard at establishing a
> "factory" for a sleek-looking glider right here in the US. ;-)
It's been rough going, but we're plugging along!
Thanks again, Bob K.
Tools -
Air powered die grinder with sanding disks and cutoff wheel
Screwdriver
Foil tape
Plastic drill and countersink
Small paint gun
Day one -
With the frame in place on the glider I used the grinder with sanding
disk and removed the gel where it contacts the frame. Cut off the
remaining canopy next to the frame with a cutoff wheel. (I once saw a
Grob mech beat one off with a hammer.) Chiseled and ground off all
plastic and the resin used to bond it to the frame. Grob uses small
screws to hold it place while the resin cures. Ground those off also.
(Approx 4 hours)
Day two-
The canopy comes oversize. Placed it on the still in place frame and
adjusted its position while overlapped and taped in place with clear
tape. Ran the cutoff wheel around and used the frame edge as a guide
removing all excess. Taped again in place. Drilled and countersinked
holes for small brass screws using a drill modified for plastic
(careful here or you'll break it). Removed canopy and put a bead of
resin on the frame. Pealed back the protective plastic around the
edge. Put it back on and lightly (real lightly) screwed it down.
(Approx 4 hours)
Day three-
Masked off at the level of the frame with metal foil tape. Hand
sanded the canopy edge to roughen and remove the resin squeeze-out.
Filled the gaps and screw heads with white Bondo and block sanded
level. Shot on gel coat with a touchup gun. After it cured, sanded
and polished the gel. Removed all the tape and protective plastic.
Cleaned and waxed it. Signed off the work in the log. (Approx 6
hours)
The moral(s) of the story is that it's not a huge task, break it and
you'll buy another, and these are hand built aircraft. The frame from
one probably won't fit another. Leave the frame in place while you
change the glass and it will fit like the original. Most of all, this
is how I did it. What you do is at your own risk. ;-)