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Crack in canopy

WingnutWick

WingnutWick

Well Known Member
Hello all,

I have had my 8 for only a few months now and am still new to it all. I took it down to Imperial CA and had it parked there for about a week and a half. When I returned and removed the canopy cover, there was a large crack in the canopy on the left side (see pics) originating from on of the screws. Where do I go from here? How do I repair this? Drill a hole in the end? Is there filler? Or do I need a new canopy, in which case, where does one get this done on the west coast? Finally, I don't have the screws on tight to prevent this, but it obviously didn't work…how does one go about preventing this in the future, rubber washers?

Thank you all!
Charles
photo.jpg
 
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Search the forums

There was a thread about this very thing last week or two.

Try searching the RV 8 forum.

And, Welcome to VAF:D

Sorry I missed your first post:eek:
 
Feel Your Pain

Not a solution - but perhaps a warm fuzzy of shared frustration. My 2 1/2 year old Silaflexed -8A doesn't have a rivet or screw in the canopy - but a few months after first flight I removed the canopy cover to discover a crack - in almost exactly the same location as yours but probably 1/3 the length. If you were listening that day, the roar you heard was me going through my expletive inventory - numerous times.

I stop drilled it and continued flying. Still upset when I see it, but no further problems. However, I have no clue as to what the max length for that "fix" is.
 
Sikaflex Questions

Hello Paul,

I’m sorry to hear that your 8A's Sikaflex’d canopy cracked. I’m trying to decide when and how to Sikaflex my 8A’s canopy. Would you mind answering a few questions for me?

1. Is your canopy the standard Van’s canopy or an aftermarket canopy like Todd’s?

2. Can you remember the approximate ambient temperature when you Sikaflex’d your canopy? (hot, warm, mid-70, cool, or cold?)

3. What is the approximate Sikaflex’d gap between your canopy frame and the canopy? (1/8 inch?, 3/16 inch?, other?, varies?)

4. Did you also Sikaflex your canopy skirt onto the canopy?

5. Did the crack occur when going from warm-to-cool or cool-to-warm ambient temperature? (I’m guessing warm-to-cool, but . . . )

Thank You,
 
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Feel your pain. Left mine in New Mexico on the ramp last winter and got two cracks at once. One coming out of the handle area and one from near where yours is. I stop drilled them and haven't had any issue since, other then the blood pressure rising every time I see it.
 
I'm in Lemoore too!

Charles -

I built a Rocket and a -4, and may be of some help (at least about where to go or what to do).

Give me a call if you like - (559) 816-0433

David Howe
 
My '8 was one of the first flying in the U.S. I built in an un-heated hangar. The canopy build happened to land smack in the middle of winter. I used a space heater inside the fuselage to warm the plexi prior to drilling and cutting. The ambient temps were close to freezing so it was a scary job. I used a figure of 80 degrees plexi temp to shoot the holes all the way around. The plan was to split the diff. (sort of) between the hottest temps 110 F. vs the coldest temps 20 F. anticipated during the life of the plane. Prior to leaving the hangar for the day I would pull all the clecos except for the very front roll over area. In the morning the aft-most holes would be off by 3/8" due to contraction of the plexi! I would then plug in the heater and wait for 10 minutes as the canopy expanded and creaked it's way to the proper length.
Every rivet hole was finished carefully while wearing magnifiers to confirm there were no stress riser chips remaining. I have not had my canopy colder than 15 degrees F since.
My point here is the RV-8 canopy has a total expansion length change of 3/8" just between 20 and 110 degrees F. Over-sized holes won't do it as the holes will need to be slotted as you move aft, increasing to 3/8 inch or more as you reach the very back. Riveted holes are under a great deal of stress unless the canopy is bonded on with a flexible adhesive. I would say the best approach would be to rivet the "roll over" area and bond the horizontal attach area all the way aft to the canopy frame. I've had good luck with my canopy and living here in the northern part of Ca. we rarely see temps in the teens. I did have my canopy cover blow off one summer during 110 degree temps. My interior thermometer showed 170 degrees after the heat blackened LCD screen cleared up! But it's not the heat that cracks these canopies it's the cold contracting the plexi and trying to pull the canopy in half. If we get an Arctic blast and the forecast temps are going to fall below 20 degrees I will put a heater in the cockpit and throw a sleeping bag over the canopy just to be safe.
My 2 cents worth on the topic
 
Slotted holes?

Thanks everyone for the help. Good info there R. Dan. I'm curious, why don't people slot the holes to begin with to allow fir this 3/8th of expansion?

At the moment I've stop drilled the crack and it's held up so far without further propagation, albeit an eye sore. The previous owner actually had this same thing happen and insurance ended up covering it! Seeing as we have the same company I have my fingers crossed. Just from reading what I've seen here, I think when I do get it re-done, SikaFlex seems to be the way to go. Here in the central valley it gets hotter than **** during the summers and pretty cold during the winter so I think flexible adhesive is the best call. I'm curious though, bubble style canopies like the 8's have been on hundreds of aircraft, does everyone have this problem or are other planes using different material?

Finally, how difficult would this be to do myself? I have no building experience but I am pretty savvy and capable with picking up such things.

Thanks again for all the help!
Charles
 
Wingnut, I feel your pain! The RV-8 canopy is a bear to build due to the total length causing such extreme expansion and contraction issues. I've built 5 RV's so far and haven't had any cracks yet (knock on head). I haven't bonded plexi to a frame yet. Here's the issue with the '8. You have a steel frame, plexi canopy glass and fiberglass skirt. The skirt and steel slider frame probably have somewhere close to the same expansion coefficient. The plexi has many times that rate. The problem is the plexi is sandwiched between the other two. If you bond the plexi to the slider frame, then bond the glass skirt over that, then will the flexible bond be able to absorb 3/8" or more movement? Only if it is VERY THICK! Something has to give. Personally, I will continue attaching my plexi canopies and skirts per the plans. I really think the key to preventing cracks is this;

1. Use the proper plexi drill bits
2. Drill and cut the plexi only when the glass is 80 degrees (no warmer as the issue of cold contraction will really come into play)
3. Warm up the plexi to at least 80 degrees before match drilling into the slider frame
4. De-burr the drilled holes using magnifier to verify no chips
5. Edge finish the plexi until SMOOTH
6. Sand the canopy skirt bond area with 100 grit and bond the skirt to the glass with quality epoxy/milled glass mix. This will help to limit the expansion and contraction of the plexi along the rivet line (my theory)

If you didn't build your own plane then you haven't experienced the joy of cutting and drilling plexi. Sort of how a bomb de-fuser feels not knowing which wire to cut. If your insurance company will pay for new glass then seek out a local who has done one or two RV's. Pay for some help. Even if your insurance won't pay for the repairs, find someone and pay for some help. Follow the suggestions 1-6 above.
Good luck to you
 
Sitka

R. Daniels said:
Wingnut, I feel your pain! The RV-8 canopy is a bear to build due to the total length causing such extreme expansion and contraction issues. I've built 5 RV's so far and haven't had any cracks yet (knock on head). I haven't bonded plexi to a frame yet. Here's the issue with the '8. You have a steel frame, plexi canopy glass and fiberglass skirt. The skirt and steel slider frame probably have somewhere close to the same expansion coefficient. The plexi has many times that rate. The problem is the plexi is sandwiched between the other two. If you bond the plexi to the slider frame, then bond the glass skirt over that, then will the flexible bond be able to absorb 3/8" or more movement? Only if it is VERY THICK! Something has to give. Personally, I will continue attaching my plexi canopies and skirts per the plans. I really think the key to preventing cracks is this;

1. Use the proper plexi drill bits
2. Drill and cut the plexi only when the glass is 80 degrees (no warmer as the issue of cold contraction will really come into play)
3. Warm up the plexi to at least 80 degrees before match drilling into the slider frame
4. De-burr the drilled holes using magnifier to verify no chips
5. Edge finish the plexi until SMOOTH
6. Sand the canopy skirt bond area with 100 grit and bond the skirt to the glass with quality epoxy/milled glass mix. This will help to limit the expansion and contraction of the plexi along the rivet line (my theory)

If you didn't build your own plane then you haven't experienced the joy of cutting and drilling plexi. Sort of how a bomb de-fuser feels not knowing which wire to cut. If your insurance company will pay for new glass then seek out a local who has done one or two RV's. Pay for some help. Even if your insurance won't pay for the repairs, find someone and pay for some help. Follow the suggestions 1-6 above.
Good luck to you
Click to expand...

I glued on my canopy with Sika and love it. As far as flex, I made a test piece, to this day I can pull this apart to almost a full inch and it just springs back. Just a data point on glued canopy.

Cheers
 
Cracked canopy

I too developed an almost identical crack in the same position on my 8A due to the cold weather I am assuming? I too just stop drilled the crack and will keep on flying but I may put a piece of clear tape on the inside or I might try to fill the drill hole so water does not come in.
 
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