Posted by JamesB on Friday, July 17, 2009 @ 02:00 PM:
I am purchasing a set of canopies for my RF5B. Since the canopies are held on with screws, this increases the chance of stress cracks.
Can anyone point me to a source of instructions for mounting canopies like these? Online? A book? etc.
Thanks,
James
Posted by SteveBeaver on Friday, July 17, 2009 @ 02:28 PM:
http://www.seqair.com/skunkworks/Canopy/Notes/Notes.html
and the first two books here:
http://www.homebuilt.org/vendors/info/bookstore/elsewhere/elsewhere.html
Posted by dannparks on Friday, July 17, 2009 @ 08:23 PM:
I recommend using a step drill to make the holes. Regular drills screw themselves into the hole and can bind and crack the plastic. Step drills kind of shave the hole open and don't stress the plastic as much. I used one on my RV and it worked perfectly.
I also made the hole bigger than the screw, countersank the hole more than usual, and used a flathead screw and countersunk washer. This allows the canopy to move under the screw and expand and shrink on the frame.
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Posted by JamesB on Saturday, July 18, 2009 @ 09:47 AM:
| Quote: |  | | Originally posted by dannparks
...I also made the hole bigger than the screw, countersank the hole more than usual, and used a flathead screw and countersunk washer. This allows the canopy to move under the screw and expand and shrink on the frame.
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Did you use Tinnerman washers?
[Edit by JamesB on Saturday, July 18, 2009 @ 10:11 AM]
Posted by JamesB on Saturday, July 18, 2009 @ 10:02 AM:
| Quote: | | |
Steve, thanks for the links.
- Would you go with larger screws than were used originally, then use Tinnerman washers with them? (the nice thing about the Tinnerman washers is that they would let you cut the hole a bit oversized to allow movement)
- With Tinnerman washers, is it important that the slope of the indentation of the washer match a countersink cut? Or do you cut a hole large enough for the indentation to fit into the hole? (sorry -- this must be a novice question)
- Would you use anything for a trim strip along the line where the screws attach to the canopy? (e.g., paint, tape or fabricate metal strips)
James
[Edit by JamesB on Saturday, July 18, 2009 @ 10:17 AM]
Posted by eugenio on Saturday, July 18, 2009 @ 12:46 PM:
If you use the screw system to install the canopy you must follow Dann and Steve suggestions. I suggest to fit a small piece of rubber hose in the plexiglas hole in order to avoid any contact between the screw and the plexiglas.
I personally prefere to glue the plexi to the frame without using screws. You must use polyurethanic sealant (like the one used to glue the windshields in the cars).
This way you have no holes to start cracks. I do that to all my RF's when I have to replace the canopy and I'm really satisfied with the result.
ciao
Eugenio
Posted by dannparks on Saturday, July 18, 2009 @ 05:31 PM:
I used tinnerman washers, and a large countersink on the plastic. Make the countersink large enough on the plastic so the washer and screw can slide around without the indention of the washer or the screw contacting the countersink. Also make sure your countersink angle is the same as the washer. Countersinks for woodworking are not the same. Use an aircraft countersink bit and a microstop countersink bit holder (and aircraft tinnerman washers). All available at aircraft tool supply shops.
The only down side is that the tinnerman washers are a bit big. You might be able to hide them a bit by painting them the color of the frame, or to match the trim color around the canopy if you paint one.
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Posted by JamesB on Sunday, July 19, 2009 @ 11:41 AM:
| Quote: | | | Originally posted by eugenio
...I personally prefere to glue the plexi to the frame without using screws. You must use polyurethanic sealant (like the one used to glue the windshields in the cars).
This way you have no holes to start cracks. I do that to all my RF's when I have to replace the canopy and I'm really satisfied with the result.
ciao
Eugenio
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Thanks Eugenio.
- Do you do any preparation of the plexi or the frames before you use the sealant?
- Is there enough contact surface between the rounded tube frame and the plexi for the sealant?
- What is your general procedure? (e.g., turn the canopy upside down, prefit the frame & mask on either side of the contact area, apply sealant to canopy, set frame)
- What do you do for trim to hide the line of sealant? (tape/paint/etc.?)
James
Posted by SteveBeaver on Monday, July 20, 2009 @ 03:05 PM:
My preference is to drill the holes with a step drill, and to do so on a warm day when the plexiglass is soft(er). Plan to make a liner, or sleeve for the hole with a short length of polyurathane tubing (aquarium tubing). Use tubing with an ID equivalent to the screw used to retain the canopy, and drill a hole of a diameter to suit the OD of that tubing of course.
The tubing will make a nice soft, flexible housing for the machine screw. I also use a layer of thin, double sided foam tape between the canopy frame and the plexiglass.
I prefer not to use Tinnerman washers because they require countersinking the plexiglass, which of course makes it thinner and more brittle. I think a washer head or truss head screw with a nylon washer under the head is a better choice.
I would mask off a black paint line around the edge of the canopy to disguise the screws.
Steve
Posted by eugenio on Tuesday, July 21, 2009 @ 03:12 PM:
No I don't do any particular preparation, I just clean the plexy from dust. If you want to prime the plexy and the frame you can use the activator contained in the kit for car windshield installation (much more expensive).
I proceed as follow: with the frame on the aircraft you must trim the plexy in order to fit, take care with all contours so as to have perfect alignment with the fuselage, not to have steps or misalignement. To better explain think of a fiberglass glider canopy, the result should be the same.
When you are ready to glue, first put some nylon or similar film all around the fuselage/canopy mating surface in order not to glue or damage the fuselage, then close the frame, try again the plexy to fit, remove it again, put the sealant all aruond the frame, with the help of someone else put the plexy on, taking care not to dirty the plexy with sealant and seat it down. Now take some masking tape and tape the plexy so as it remains flush with the fuselage shape without steps. Let it settle until the sealant is cured. Once cured remove the masking tape and take the canopy out of the plane. Now you will fill the whole space between the frame and the plexy in the upper part with sealant until it looks like a square tube frame, This will finish the upper part and make you sure the plexy has a sufficent glueing surface.
The lower part can be finished with some glass reinforced putty. If you want to make a seal you must leave a slot on the mating surface in order to put in a seal. All fits must be not too tight in order to let the plexy expand/retire with outside temperatures.
Usually on the inside I do not use masking tape, I stirr the sealant with my finger. When the job is finished I paint the canopy contour in order to mask the frame, inside and out.
Remember some tips:
Windows should be cut after the canopy has been fitted, in this way you can do it in the correct position and parallel to the frame.
When you glue the plexy you must be sure to be able to open the canopy when sealant is cured, this means that in the RF5B you had better to do only one canopy each time, otherwise if it locks you won't be able to open it again.
Fresh plexy is not so fragile as it may seem, it only must be used with warm temperature.
For the window you should do a template and cut it with a high speed hand mill, it is a very easy job to do and without risks.
hope all this will help
ciao
Eugenio
Posted by JamesB on Friday, July 24, 2009 @ 11:53 AM:
Lots of good suggestions. The final choice may tend to reflect a person's personal skills & tastes.
Many people have remarked about masking for paint.
- Is there a particular brand or kind of paint that you'd use to trim the plexi? I assume that after masking, the strip area would need to be sanded.
- Are you using primer?
- I have seen paint in both black and silver. Are there particular advantages to one color over another?
(Sorry--lots of questions. Note that I am reading up on this as well. But it's also important to ask people who have actually done this. Thanks.)
Posted by SteveBeaver on Friday, July 24, 2009 @ 01:31 PM:
Rustoleum make an aerosol paint intended for plastic lawn furniture. It works very well on Plexiglass ans is avilable from Lowes/Home Depot in the USA.
Steve
Posted by eugenio on Friday, July 24, 2009 @ 01:36 PM:
You use the same paint you use on the aircraft. If your fuselage is white you do it white with the same product. No primer is needed (I never used it) Do not diluite too much the paint, thinner badly affects the plexy. Use trimming tape, not masking tape for the contour and leave it imediately after having painted, this will leave a smooth contour (rounded edge of the paint that is still settling). As already stated, do it like it is a fiberglass high performance glider or Ray's GROB 109. Inside you can do it gray or the colour of your's interiors/ulphostery. (trimming tape is a plastic soft tape similar to electrical tape, but does'nt leave off the glue) Remember, when you paint, to mask the whole canopy, outside and inside if you don't want it damaged by the paint. Work the canopy over a soft rag and take care not to trap in it debris or other stuff that can damage the plexy. When you get finished you can remove small scratches with water based polish. When you get some confidence with plexyglas you will see that it's easy to work, not so easy to break and you only need a few precautions: always use a angle grinder with a cutting disk to cut and trim it; do not use standard new drill bits or you will break it, use an old drill bit not sharpened or modify the cutting angle;
For trimming the window use a high speed rotary file or handheld mill with small bits; leave some space around the handles and the hinges because if metal touches the plexi it will break it at the first jump.
Please do a good job, any kind of system you're goig to use.
ciao
Eugenio
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