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andrsnj

Member
I am finishing up my canopy which has no rivet holes drilled in it. I had a problem with drilling all those holes in the plexiglass and trying to match them up with a round frame tube as well as floppy side skirts. This looked like a disaster waiting to happen and has been confirmed by all the cracked canopy reports I have been reading. As a final incentive to choose this method I went to an airshow where I saw another RV. This plane looked real nice but when I took a closer look at his canopy I saw that some of the rivets did not match up all 3 holes, skirt, canopy and plexiglass. So I made 37 clamps from aluminum hex stock and drilled and tapped holes for screws that acted to clamp onto the plexiglass. The clamps go around the frame tube and are restricted from moving upward by the bottom of the "U" channel machined into the clamp. The top of the clamp is open which allows the canopy to slide down along side the frame tube. My clamps must be installed with a twisting motion so that they cannot move up or down when installed since they have a half round section which mates with the frame tube. After the plexiglass is in place and pretty much held there with no other mechanical means other than the clamps which are machined just wide enough to accept the plexiglass. Screws are used to put a little pressure on the plexiglass. The screws push against a flat piece of aluminum about an inch square and the plexiglass is sandwiched between the outside of the clamp and the inch square aluminum. To make this arrange fail safe I used Sika flex 295 sealant around the entire canopy edge. The sealant fills a small gap of about 1/8 inch which was created by the width of the outer wall of the clamp and the side skirt. It also fills 2 fillets between the plexiglass and the frame tube. I believe this is a better way to make a canopy. My feeling is that either the clamps or the Sikaflex by itself would have been sufficient to hold the canopy in place, especially the Sikaflex. But together I can't see anything that is going to move that canopy. If I get nervous about pressure on the plexiglass then I would feel confident that the Sikaflex would hold the canopy all by itself and I could relieve some pressure off the clamps which isn't much to begin with. Even with no screws in the clamps I built the canopy with just the plexiglass resting in the slots created by the clamps which held it sufficiently. Oh yeah, I forgot to mention that I also riveted "wings" onto the clamps to which I riveted #4 nutplates that the side skirts mount to, it works.
 
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Photos as requested

If everything works out OK you will have some photos of the canopy clamps. I will attempt to upload 4 photos showing an interior shot of an installed clamp, an exterior view showing the #4 screws which go through the skirt and beneath the plexiglass and into the clamp and also some clamps that are partially finished that I didn't use. Here goes. My photos are too big, I will attempt to make them smaller and try again. Since I now need a new battery in my camera this may take a while. For now I will try a little more description. One of the hard parts of this method is to squeeze the #4 screw under the canopy frame and still have it go through the flat part of the skirt. Since the traditional way of doing this is to drill through the skirt, plexiglass and frame tube the attachment points are a little higher because I am securing the skirts below the frame tube. The difference is only about a half inch or less so I don't think this is a big problem given the difficulty of the canopy in general this is a minor obstruction. On my plexiglass I would still have been dealing with very small edge distances on my plexiglass unless I did more trimming on the front and rear to lower the entire canopy. I didn't want to do this which was another reason I went the way I did. As it turns out, a few of the screws are near the crease in the skirt but are in the flat part. There was room to make the crease larger if this was a problem but it worked out OK. Building the canopy is more art work than anything else anyway so this is just more of the same. Building this canopy was probably the most difficult task I have encountered on this airplane so far but I have used all the original parts which is more than some others can say. There must be an easier way to build a canopy. One thing I would have done differently is to make the "wings" on the clamps a little larger to better accomodate the small "mini", as they were called, #4 nutplates. I actually trimmed off one of the rivet tabs on mine so the nutplates are only held on by one rivet each. I don't see this as a problem since they are only holding on the skirts which are also sealed in place with the Sikaflex 295. I did some research on the Sikaflex and I believe this is the best stuff to use. It is specifically made for this type of application and is used primarily in cruise ships. It is UV resistant and paintable. I looked into silicones but didn't find one that I liked. Sikaflex 295 is pretty tough stuff from what I can see.
 
Photos

I uploaded photos to yahoo RV4 group. To see them go to yahoo.com, groups, RV4, photos. I have a total of 5 photos, 2 in "andrsnj1" folder and 3 in "canopy" folder. The 3 in the canopy folder were taken in close up mode so details are clear. Like I said earlier, if I had to do another canopy I would do it the same way. Just trying to help those who follow as others have helped me. The Sikaflex 295 was a little difficult to apply neatly since it is quite sticky right out of the tube. My plan is to apply some more and wait a while for it to set up to a point when I can smooth it out better. This is for asthetics only, the sealer that holds everything together is well extablished in all the nooks and crannies. I actually used some round foam strips that I got at Home Depot to fill in a spot in the front under the aluminum fairing I made that runs around the front of the canopy. From what I've seen most builders use fiberglass here but I made a pattern out of paper and transferred it to aluminum, it works. This would have required a lot of sealant between the fairing and the plexiglass which I didn't think was necessary. By using the foam I used less sealant but still plenty. The aluminum fairing is about 2 or 3 inches wide in front and tapers down to about an inch on the sides.
 
Photos

I am in the same boat as Bob, the previous poster......why not post them within this forum as well?

The concept of no drilling in the plexi is something I know everyone would appreciate!

Take care!
 
not a yahoo member, no problem

It's real easy to join up, doesn't cost anything. Just go there, Yahoo.com, groups, RV4 and sign up. It will take a day or 2 to get approved but that's it. I will still attempt to make these photos smaller but like I said I'm having trouble with my battery in my camera. It's a mystery because it reads plenty of volts, 4.2v for a 3.7v lithion Ion battery and it powers a flashlight bulb with no problems but in the camera it balks. I guess I'll just get a new one, hope that works. My feeling on holes in plexiglass is that they shouldn't be there. I feel much better this way. Yes I know they've been doing it this way for years, but they've been cracking for years too. Also, this is a very small target we're trying to hit. A little 1/4 inch tube, or whatever size it is, and trying to match it up with that flexible side skirt flopping around, that's not for me. A flat surface and drilling through one other piece might work and maybe I would have done it but not like it is. Also, we have newer and better sealants now, why not take advantage of them? In the mean time, go to yahoo, they want members too.
 
photo

I took the liberty of posting one of your photos here. I have to say I can't quite figure how your system works from the photo or the other two. I'm not really too familiar with the RV4 canopy attach system, so that's no surprise. Perhaps I've started my new year's celebration too soon!

img14740bu.jpg
 
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photos of canopy sealant

andrsnj said:
I uploaded photos to yahoo RV4 group. To see them go to yahoo.com, groups, RV4, photos. I have a total of 5 photos, 2 in "andrsnj1" folder and 3 in "canopy" folder. The 3 in the canopy folder were taken in close up mode so details are clear. Like I said earlier, if I had to do another canopy I would do it the same way. Just trying to help those who follow as others have helped me. The Sikaflex 295 was a little difficult to apply neatly since it is quite sticky right out of the tube. My plan is to apply some more and wait a while for it to set up to a point when I can smooth it out better. This is for asthetics only, the sealer that holds everything together is well extablished in all the nooks and crannies. I actually used some round foam strips that I got at Home Depot to fill in a spot in the front under the aluminum fairing I made that runs around the front of the canopy. From what I've seen most builders use fiberglass here but I made a pattern out of paper and transferred it to aluminum, it works. This would have required a lot of sealant between the fairing and the plexiglass which I didn't think was necessary. By using the foam I used less sealant but still plenty. The aluminum fairing is about 2 or 3 inches wide in front and tapers down to about an inch on the sides.
Click to expand...

How can I see photos of your canopy process?
 
Paragraphs please

There is this useful tool in writing called the paragraph...... it makes thing much easier to read.

I find it almost impossible to read things without paragraphs please use them.
 
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