Cost to install a canopy?

[Roger Worden]

Our club is looking into a new canopy for a Grob 103 Twin Astir. We received
an estimate from a well-known repair shop: $2,000 for the canopy and 50
hours of labor to install. I'm new to this field - I fly 'em, I don't fix
'em. But I'm having a hard time imagining what steps must be involved to
consume 50 hours. Hinge, latches... what am I missing?

[jphoenix]

Gluing, sanding, gelcoating.

[Jancsika]

Roger Worden wrote:
> Our club is looking into a new canopy for a Grob 103 Twin Astir. We received
> an estimate from a well-known repair shop: $2,000 for the canopy and 50
> hours of labor to install. I'm new to this field - I fly 'em, I don't fix
> 'em. But I'm having a hard time imagining what steps must be involved to
> consume 50 hours. Hinge, latches... what am I missing?

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

[Tim Mara]

I think your estimate is pretty close to correct and what you may
expect.......labor rates may vary from one repair shop to another but
generally you can expect to pay something near the cost for the canopy equal
in labor costs....or between $2000-$2500 (estimated)
the labor involved is rather extensive if done properly.....removing all of
the old acrylic (Plexiglas) breaking chipping and grinding off where the old
canopy was glued in place, repairing and preparing the canopy frame to
accept the new acrylic, fitting the new canopy (really good canopies like
Mecaplex or similar will be factory trimmed pretty close to fit, others
might require a lot of extra trimming (and time) then re-gluing the new
acrylic to the frame, all quite fragile work as well.......then repainting
(gelcoat) the frame (a portion of the acrylic is also painted where it is in
the frame work) and then re-fitting to the glider.....Most repair shops also
want the glider in their shop to do the work since the frame will take a
different set if not mounted on the glider when the new acrylic is
installed..so you can see that the work is a bit intensive and deserves the
time and effort .........you also want to be certain that the canopy you are
installing is the proper one and of the highest quality, since an inferior
canopy will cost the same labor (or more) to install and since the acrylic
is (should be) protective coated, even the repair shop won't know what the
optics or quality of the canopy is until the job is 99% complete and they
then remove the coating.......I, BTW do not do the repairs.....but do
support many of the better glider repair shops in the USA.....I hope you do
too...we need them!
Best regards
Tim
Wings & Wheels
www.wingsandwheels.com

"Roger Worden" > wrote in message
. com...
> Our club is looking into a new canopy for a Grob 103 Twin Astir. We
> received
> an estimate from a well-known repair shop: $2,000 for the canopy and 50
> hours of labor to install. I'm new to this field - I fly 'em, I don't fix
> 'em. But I'm having a hard time imagining what steps must be involved to
> consume 50 hours. Hinge, latches... what am I missing?
>
>

[HL Falbaum]

Since you state that you are "looking into" a new canopy, can we assume that
the old one is not broken?
If it is not broken, it may be possible to revive the old one with one of
the repair kits like Micro-mesh. Available from aircraft supply place,
possibly Tim Mara.

--
Hartley Falbaum


"Roger Worden" > wrote in message
. com...
> Our club is looking into a new canopy for a Grob 103 Twin Astir. We
> received
> an estimate from a well-known repair shop: $2,000 for the canopy and 50
> hours of labor to install. I'm new to this field - I fly 'em, I don't fix
> 'em. But I'm having a hard time imagining what steps must be involved to
> consume 50 hours. Hinge, latches... what am I missing?
>
>

[Bob Kuykendall]

Tim has provided a pretty good summary of the process. Some notes on
canopy transparencies in no particular order:

* 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

Bob K.
http://www.hpaircraft.com/hp-24

[Mike C 17]

I just finished putting a new canopy on my Phoebus and it took about 60
hours to do. I know it can be done quicker by a more experienced
technician, but it is labor intensive. A lot depends upon how difficult
it is to remove the old canopy and any required prep work to repair the
frame when the old canopy is removed.

Mike

[Mike C 17]

Hi Roger,

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

[Roger Worden]

Shows what I do NOT know! I was assuming a new canopy would include the
frame, hinge, latch etc. so it could be installed as a unit. I haven't been
out to look at the Grob since this issue came up, but I seem to remember it
as a fairly simple structure. I'm wondering whether Grob sells a new
canopy-frame-hinge-latch combo for less. Factory labor to assemble new
things in an repetitive process is usually less expensive than a craftsman
in the field repairing a similar unit... whether it's a television, a car
engine, or whatever, major repair is usually more expensive than replacement
with a factory-assembled unit. But maybe such assemblies are not available
from Grob, or maybe the typical economics don't hold true in this market.


"Jancsika" > wrote in message
...
> Roger Worden wrote:
> > Our club is looking into a new canopy for a Grob 103 Twin Astir. We
received
> > an estimate from a well-known repair shop: $2,000 for the canopy and 50
> > hours of labor to install. I'm new to this field - I fly 'em, I don't
fix
> > 'em. But I'm having a hard time imagining what steps must be involved to
> > consume 50 hours. Hinge, latches... what am I missing?
>
> 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

[Diederick]

Hi Roger,

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

[Bob Kuykendall]

Earlier, Roger Worden wrote:

> 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.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

[Doug Hoffman]

Bob Kuykendall wrote:
> 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

[[email protected]]

Here is an article I found on how to make the canopy blank yourself:

http://www.sportaviation.org/magazine/2004_summer/canopy.pdf

Still, it is a fair amount of effort for one canopy.

Tom

[Papa3]

Roger,

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)

[pbc76049]

I manufacture Transparencies for a living.
Mostly windshields for sports cars. There are so
many places to screw up that it can be a truly
humbling experience. What puzzles me is that
most folks give little atention to the canopy as
it ages. You can double the life of a canopy
by keeping it squeaky clean and polishing the
surfaces at least annually. Proper polishing
doesn't remove material from the plastic, it removes crap
from the plastic. Micromesh is NOT a polishing system
it is much too agressive, it is for repair work. Even
with normal care, the exterior (interior also) will eventually
degrade and start to produce chalk like deposits as the
monomers in the plastic sublimate. Once it gets to this
state, you basically are on life support. If you have
a canopy that is so old it just won't polish well,
Micromesh probably won't help as the sublimation is
in most cases deeper than the max grind depth of the system.
When you get to this place, toss the book aside, and get a bit creative.
The object of the game is now to stop sublimation and seal the canopy
surface with something you can see thru. Believe it or not, the
green can TURTLE WAX will make things a lot better. It
will fill the small scratches and surface pores and get you back
to a usable canopy surface. The downside is that it stops the canopys
ability to breathe and adjust to humidity changes which will cause
a higher internal hoop stress load to exist and make the canopy less
forgiving to bumps and racking. DON'T do this to a canopy with
life left in it, but when the choice is this or a replacement, I like doing
this first.
I've got some vintage race cars going on 5 or 6 years doing this. They
are one step from the grave as far as repairability, but they still work ok
enough to use. As far as day to day maintenance, a couple thoughts.
First, Plexiglass (PMMA) isn't really a solid. It is an incredibly viscous
liquid and is pourous. This means that the stuff it is made of can
"evaporate"
(sublimate) over time. It also means that stuff you put on it can "go into
suspension" inside the plastic. This is why I cringe so bad when I see
Lemon Pledge used on a canopy. Not only is the propellant, usually
isobutane, (a great solvent I might add) trapped inside the canopy by the
wax
so it can disolve the internal structure of the plastic, but the free
breathing of
the plastic and its ability to adjust its relative humidity are compromised.
Dust can do the same thing, it will plug the plastic pores and in most cases
it is acidic and will react adversely to the plastic. So what to do.
Keep a piece of dry flannel on the canopy when you aren't using it. Only
use good quality plastic cleaners designed for the plastic you have. Always
start a canopy cleaning with clear water to get the dust off the canopy
before you start smushing it into the plastic with your cleaning rag.
Only use soft cotton to clean the canopy, old diapers are the gold
standard. I hope this helps, and no, I'm not looking for canopy work....

Scott.

[Bob Kuykendall]

pbc76049 (removethis) wrote:
> I manufacture Transparencies for a living...

Spectr Scott, I been trying to get ahold of you. Drop me an email when
you can.

Thanks, Bob K.

[Bob Kuykendall]

Earlier, Doug Hoffman wrote:
> Bob Kuykendall wrote:

> 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.

[Don Hammer]

I've replaced a couple of Grob canopies, but it has been over 10 years
ago. Each went like this -

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. ;-)

[[email protected]]

Hello Roger, i have a gas station where i want to get canopy installed
If u can email me at

[Charlie M. (UH & 002 owner/pilot)]

I believe you want an awning type thing, we are talking about clear/tinted plastic over the cockpit of an aircraft.

Try another Google search.

;-)

[ND]

On Thursday, December 8, 2005 at 9:40:42 AM UTC-5, Roger Worden wrote:
> Our club is looking into a new canopy for a Grob 103 Twin Astir. We received
> an estimate from a well-known repair shop: $2,000 for the canopy and 50
> hours of labor to install. I'm new to this field - I fly 'em, I don't fix
> 'em. But I'm having a hard time imagining what steps must be involved to
> consume 50 hours. Hinge, latches... what am I missing?

after removing the old canopy, which includes lots of chipping t the frame with a chisel, you have to prep the frame with a grinding disc. basically you are making space for new glue. then you have to trim the canopy to size. (a slow, careful process requiring lots of concentration.) there are many test fits you have to do. then once the frame is prepped and the canopy is cut to size, you scuff the inside of the class where it will contact the frame. you have to apply a seal strip to the frame perimeter to keep glue from overflowing into the cockpit side of the canopy frame. after the canopy is glued, you have to sand the perimeter of the frame, if not stripping it completely. sometimes there is some fitting work required with bondo, then there is priming (if done in urethane) you have to sand that primer. and spraying of paint or gelcoat. then you sand that. if you sand through the paint/gelcoat, which often happens on the first attempt, you have to do touch up spraying, then sand that. by the way, sanding in this case involves working through several grits from 320 to 1500. then you can polish it. after that you clean up the edges, and generally the glider it self needs to be cleaned up as well. its definitely 50 hours of work. that's probably even a little generous.

[Wheaton]

$6000. $3000 for canopy and $3000 labor. Three canopies over five years different club and private ships. Fitting is the art. Wheaton

[Giaco]

On Wednesday, November 15, 2017 at 1:46:06 PM UTC-5, Wheaton wrote:
> $6000. $3000 for canopy and $3000 labor. Three canopies over five years different club and private ships. Fitting is the art. Wheaton

The PIK-20 group has just done a group order and they came out to just over $1800 for a tinted canopy, no labor included.

[Bret Hess]

On Wednesday, November 15, 2017 at 11:46:06 AM UTC-7, Wheaton wrote:
> $6000. $3000 for canopy and $3000 labor. Three canopies over five years different club and private ships. Fitting is the art. Wheaton

I'm not sure there is much art to the fitting.

Look at the description of Don Hammer earlier in this post:
"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... Removed canopy and put a bead of
resin on the frame."

There is no fine fitting here. I'm removing my old canopy in prep for a replacement and find that the edge is uneven by millimeters, which fillers compensate for. Good adhesives have several thousand psi strength in tension and shear, so the adhesive takes the canopy load, not canopy to frame-lip contact.

[Bret Hess]

> The PIK-20 group has just done a group order and they came out to just over $1800 for a tinted canopy, no labor included.

We're having them made now in CA. $1510 per canopy tinted with window, plus $150 to $300 shipping.

[[email protected]]

On Tuesday, November 28, 2017 at 5:02:04 PM UTC-5, Bret Hess wrote:
> On Wednesday, November 15, 2017 at 11:46:06 AM UTC-7, Wheaton wrote:
> > $6000. $3000 for canopy and $3000 labor. Three canopies over five years different club and private ships. Fitting is the art. Wheaton
>
> I'm not sure there is much art to the fitting.
>
> Look at the description of Don Hammer earlier in this post:
> "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... Removed canopy and put a bead of
> resin on the frame."
>
> There is no fine fitting here. I'm removing my old canopy in prep for a replacement and find that the edge is uneven by millimeters, which fillers compensate for. Good adhesives have several thousand psi strength in tension and shear, so the adhesive takes the canopy load, not canopy to frame-lip contact.

Do it yourself brain surgery isn't a big deal either. Just get out the drill and go for it.
I've done about 20 canopies and all require some degree of "fine fitting". Some not much. Some as much as 12 hours just fitting. If the canopy is not properly fitted it won't match the contours of the glider and will look like junk.
UH

[Bob Kuykendall]

> There is no fine fitting here...

Yeah, I've seen lots of gliders like that.

I have fitted a couple of canopies, and I can say that the more effort and attention you put into it, the better it turns out. The fit of the canopy transparency to the frame, and the assembly to the fuselage, is the first and last thing you see when you get in and out of a glider, so it's nice when it it all looks good.

Pretty much anyone can learn to do it, but when you learn by doing the lessons are too often too late for the learning.

Some points from our experience:

* If you fit the canopy so that the edge is proud of the contour, you can always add a bit of filler to the fuselage and make it look just fine. But if you fit the canopy so that the edge is below flush of contour, it is much harder to deal with.

* Canopy frames often have built-in stresses and preloads that spring them out of shape when the transparency is removed. So it is usually best to fit the canopy while the frame is mounted to the fuselage and maybe has a few spring clamps to hold it into place on the fuselage.

* Canopy transparencies are often not very consistent in thickness around the perimeter; this is a side effect of the stretch forming operation. So don't expect to create an inset the exact canopy thickness and have it come out perfect. The thickness varies, and you also need room for the bonding paste.

* It might be an old wives tale, but I've been told that the BGE diluents in laminating epoxies can attack and craze acrylics. In my shop we use an undiluted bonding resin for canopy transparencies, just in case.

* Squeezeout happens. Use lots of masking tape, and wax the fuselage and everything else you don't want stuck together. The DG guys actually use a narrow strip of weatherstripping along the upper edge of the canopy frame to keep the squeezeout from coming up and into the cockpit. I've not tried that, but it sounds like a good idea.

* Do not attempt to cut, drill, sand, or file the transparency unless it is above about 70 degrees F. Fresh acrylic plastic is actually quite easy stuff to work with when it's warm. But like glider pilots, the colder and older canopies get, the more disagreeable they become.

--Bob K.

[[email protected]]

On Tuesday, November 28, 2017 at 6:09:15 PM UTC-6, Bob Kuykendall wrote:
> > There is no fine fitting here...
>
> Yeah, I've seen lots of gliders like that.
>
> I have fitted a couple of canopies, and I can say that the more effort and attention you put into it, the better it turns out. The fit of the canopy transparency to the frame, and the assembly to the fuselage, is the first and last thing you see when you get in and out of a glider, so it's nice when it it all looks good.
>
> Pretty much anyone can learn to do it, but when you learn by doing the lessons are too often too late for the learning.
>
> Some points from our experience:
>
> * If you fit the canopy so that the edge is proud of the contour, you can always add a bit of filler to the fuselage and make it look just fine. But if you fit the canopy so that the edge is below flush of contour, it is much harder to deal with.
>
> * Canopy frames often have built-in stresses and preloads that spring them out of shape when the transparency is removed. So it is usually best to fit the canopy while the frame is mounted to the fuselage and maybe has a few spring clamps to hold it into place on the fuselage.
>
> * Canopy transparencies are often not very consistent in thickness around the perimeter; this is a side effect of the stretch forming operation. So don't expect to create an inset the exact canopy thickness and have it come out perfect. The thickness varies, and you also need room for the bonding paste.
>
> * It might be an old wives tale, but I've been told that the BGE diluents in laminating epoxies can attack and craze acrylics. In my shop we use an undiluted bonding resin for canopy transparencies, just in case.
>
> * Squeezeout happens. Use lots of masking tape, and wax the fuselage and everything else you don't want stuck together. The DG guys actually use a narrow strip of weatherstripping along the upper edge of the canopy frame to keep the squeezeout from coming up and into the cockpit. I've not tried that, but it sounds like a good idea.
>
> * Do not attempt to cut, drill, sand, or file the transparency unless it is above about 70 degrees F. Fresh acrylic plastic is actually quite easy stuff to work with when it's warm. But like glider pilots, the colder and older canopies get, the more disagreeable they become.
>
> --Bob K.

[JS[_5_]]

On Tuesday, November 28, 2017 at 2:02:04 PM UTC-8, Bret Hess wrote:
>
> I'm not sure there is much art to the fitting.
>

That opinion may change after the canopy cracks due to stress in extreme temperatures.
Jim

[Darryl Ramm]

On Tuesday, November 28, 2017 at 2:02:04 PM UTC-8, Bret Hess wrote:

> I'm not sure there is much art to the fitting.

That is one of the more assuming thing I've read on r.a.s. Please post photos of your transparency installation progress.

[Scott Williams]

On Tuesday, November 28, 2017 at 10:27:57 PM UTC-6, Darryl Ramm wrote:
> On Tuesday, November 28, 2017 at 2:02:04 PM UTC-8, Bret Hess wrote:
>
> > I'm not sure there is much art to the fitting.
>
> That is one of the more assuming thing I've read on r.a.s. Please post photos of your transparency installation progress.

Too Funny,

How about;
how to refinish a glider in three easy steps;
1, remove old finish
2, spray on new finish
3, polish and go fly!!

[Charlie M. (UH & 002 owner/pilot)]

Looks like here is a "DIY" gone wrong......https://groups.google.com/forum/m/#!topic/rec.aviation.soaring/JpJN10ItxEs

Not having done it myself, but having to do a refinish, good buffing, sure, go for it..

You want a 20' job, or an "aerodynamic" job?

Sure, a so-so job on a 1-26 may be decent, pushing up into the 40's L/D is different.
You want looks or performance?

[Bob Kuykendall]

On Wednesday, November 29, 2017 at 10:35:10 AM UTC-8, Charlie M. (UH & 002 owner/pilot) wrote:

> You want a 20' job, or an "aerodynamic" job?

Well now, there's a topic that can go on and on. In my direct experience, stuff that looks gawdawful at the 20-foot or even 10-foot level can perform great at the 0.004" level where it really counts for laminar flow. I've seen gliders where the reflection off the wing looked like some crazy funhouse mirror, where the leading edge waved fore and aft. But down in the boundary layer it is smooth and wave-free in the streamwise direction, and plenty close enough to the desired profile and camber line, and it works just fine..

And a lot of stuff that looks fantastic at the 10- and 20-foot level is actually disruptive at the .004" level. A good example of this is the crisp planform breaks on the latest generation of polyhedral gliders. They do look sharp and precise, but they can't be good for spanwise flow (air trying to sneak out and get all 420 with the tip vortex).

In order of importance, for most gliders I'd rank:

* Control surface seals (mylar, curtain, or combo)

* Wing waviness below 0.004" on top back to 60% chord, on bottom back to hinge line

* Cockpit exhaust provisions (keep cockpit below ambient so canopy leaks come inside, not outside)

* Leading edge contour for the forward 10% of chord

* Canopy fit on forward 1/3 of length

* Wing profile aft of 10% chord