Blanik L13 Windscreen Replacement

Our club (USA) is looking to replace the broken foremost windscreen on
our L13 and is seeking alternative sources. A search of RAS turned up
very limited info. Aircraft Windscreens Inc in CA was mentioned but I
couldn't find them on the web. The part from LET is $500+. Also, does
anyone with experience with this particular job have tips or tricks?
There are about 80 srews around the frame. That's alot of drilling. I
know we need special bits.

Mike

Have a look on : Wings & wheels site.
I think you could what you are looking for.
Regards,
Bruno

On Feb 24, 12:18*pm, Mike125 wrote:
...Aircraft Windscreens Inc in CA was mentioned but I
couldn't find them on the web...

Aircraft Windshields Co. is in Los Alamitos, CA, their phone number is
562-430-8108. I don't know if they have L-13 sections, but it's
certainly worth ringing Judy up and asking her to check their catalog.
Like many old-school specialty houses, ACW hasn't shown any particular
need of a Web presence yet.

There are about 80 srews around the frame. That's alot of drilling. I
know we need special bits.

In my rather meager experience (Where practical, I would rather use
Liquid Nails to secure acrylic than fasteners in drilled holes), the
most important factor in drilling acrylic is temperature. My advice is
to not attempt to drill plexi unless your the entire part and also
your workarea are at or above a temperature of 70 degrees F. Other
than that, practice your technique using the special drills and scrap
acrylic, and see what works before you dig into your actual canopy
transparency.

One other thing to realize is that a lot of people only have
experience with old, weathered, and sun-beaten acrylic such as you'd
find in aged gliders. So they naturally assume that all plexiglass is
hard, brittle, and extremely crack-prone. In actuality, new acrylic
(or even old acrylic that has been kept in protective sheeting and out
of the elements) is noticably more flexible and forgiving. That's
certainly not to say that new acrylic is crack-proof, just that it
does give you a bit more margin than you might expect based on
experience with 35-year-old plexi.

Thanks, and best regards to all
Bob K.
www.hpaircraft.com/hp-24 - Now with all-carbon spars!

Also, does
anyone with experience with this particular job have tips or tricks?
There are about 80 srews around the frame. That's alot of drilling. I
know we need special bits.

Mike

Be vary careful transferring your holes (sucks to do something
perfectly wrong...)

Buy the special acrylic bits. They have a special point that doesn't
allow itself to screw into the plastic faster than the tip is shaving
away the base of the hole, keeping it from punching through before the
hole is there (important, otherwise it WILL crack)

Drill at a lower speed and let the bit do the work.

Let the bit do the work. (seriously, don't push it along)

Take your time.

Good Luck! (it gets more tense with each hole...)

-Paul

On Feb 24, 12:18*pm, Mike125 wrote:
Our club (USA) is looking to replace the broken foremost windscreen on
our L13 and is seeking alternative sources...

Mike, if you're a bit tolerant of profile, I might have a chunk of
curved acrylic that gets close to what you need. If you send me a
kraft paper or duct tape template of the transparency, I'll trundle my
canopy scraps pile for something about right.

Here's what it looked like the last time this happened:

http://www.hpaircraft.com/hp-24/update_29_may_08.htm

Thanks, Bob K.

My experience with getting parts from Blanik is they are close
approximations, but they are never exact fits. They will take a fair
amount of tweeking to get to fit after you get them.

I once got a L-23 canopy replacement. It was not formed correctly, it
was not trimmed, and none of the holes were drilled. It cost me a lot
for my A&P to install.

The same was true for a L-23 wing section and an L-13 landing gear
trunion. It took significant work after receiving to get each one of
them to fit.

On Tue, 24 Feb 2009 12:18:31 -0800 (PST), Mike125
wrote:

Our club (USA) is looking to replace the broken foremost windscreen on
our L13 and is seeking alternative sources. A search of RAS turned up
very limited info. Aircraft Windscreens Inc in CA was mentioned but I
couldn't find them on the web. The part from LET is $500+. Also, does
anyone with experience with this particular job have tips or tricks?
There are about 80 srews around the frame. That's alot of drilling. I
know we need special bits.

Mike

I don't know why I didn't ckeck W&W first. Duh. Do you think it is
better to drill smaller holes and increase the size or just go for it
on the first try? Thanks for the input. BTW, this ship is on the
market (but not yet advertised on W&W). Painted w/Imron 5 years ago,
with trailer located in NJ - asking $20K.

Mike

On Feb 25, 6:47*am, Mike125 wrote:
I don't know why I didn't ckeck W&W first. Duh. Do you think it is
better to drill smaller holes and increase the size or just go for it
on the first try? *Thanks for the input. BTW, this ship is on the
market (but not yet advertised on W&W). Painted w/Imron 5 years ago,
with trailer located in NJ - asking $20K.

Mike

I have a set of Plexiglas drill bits I use frequently - they do a
great job on almost any plastic. I'd go for the final hole size -
just be sure it's in the right spot.

Canopy makers have figured out that that selling untrimmed, undrilled
plastic puts the cracking problem in the hands of the customer who
will be back for yet another part if they crack it.

That said, Bob K was right in that new Plexiglas is far more forgiving
than old brittle stuff. Just work carefully and avoid problems.

The L-13 canopy isn't complicated so it should be possible for a
vendor to "free blow" a replacement which should result in far better
optics than the original.

On Feb 25, 6:54*am, bildan wrote:
On Feb 25, 6:47*am, Mike125 wrote:

I don't know why I didn't ckeck W&W first. Duh. Do you think it is
better to drill smaller holes and increase the size or just go for it
on the first try? *Thanks for the input. BTW, this ship is on the
market (but not yet advertised on W&W). Painted w/Imron 5 years ago,
with trailer located in NJ - asking $20K.

Mike


I just finished drilling and countersinking 60+ holes for my Open
Cirrus last week. I would pick up the old hole locations from the
frame by just drilling enough to make a slight mark, then dismount the
canopy and drill full size. the 60 deg angle of the plexiglas drill
bit seems to preclude drill wander.

In addition to all that was said so far, you should back up the holes
with a piece of wood or equal and carefully control the speed and feed
at the point the drill bit breaks through. Touch c'sink both sides of
hole. I used the bits sold at A/C spruce. If you can produce perfect
holes and countersinks on the old plexi, should have no problem with
the new stuff. Biggest problem is getting tired and not paying
attention after the first couple dozen holes. A typical flaw is a
small radial crack or chip at the back side of the hole, this can be
removed by countersink, and I would omit the screw in that location.

Lastly, the CFR title 14 part 21 has requirements for parts on type
certificated aircraft. Might want to research this before going
aftermarket.

aerodyne

better to drill smaller holes and increase the size or just go for it
on the first try? *

I like to use exact size holes I want the first time. I thought it was
safer (reduced exposure...), as well as faster, but, Tim has a great
do's and don'ts for this very thing (again, on W&W, Thanks Tim!...)
http://www.wingsandwheels.com/Installation.htm and he recommends step
drilling... Lots of really good tips there (including carefully and
lightly chamfering the edges of the holes w/a countersink bit)

-Paul