Tip-up Canopy plexi problem

I've made the 'big cut'. Now I'm doing final trimming and fitting.

The fit in the area around the right 'ear': the plexi doesn't seem to have enough bend in that area so it doesn't want to lay down along the side rail without considerable pressure applied.

Also, when it was made, that side didn't stretch much in the mold so it is just about full thickness of 3/16ths, which adds to the flexibility/fit problem.
The left side fits easier - it is about 1/8th"+ thick.

Can the right side be heated up enough to relax that tension? If so, how?

Gus at 'mothership' said not to apply any heat in that area, but just to make it work. I'm afraid of it cracking in that area at some point in its life.

Cliff
Chase, BC
RV9A, canopy

plexi fun

Cliff, hope you are doing well with your build.
If you haven't already found any help from the RV guys in Kamloops and Vernon,
you could try there. Lots of sliders, but John swallow in Vernon has a tipper -7a, and Rick Thorburn is on his 6th Rv I think, so may have some ideas.

from what I know about plexi, to truly make it 'plastic' and relieve the stress, you'd need to evenly bring the whole thing to the 'correct' temp, apply even pressure, without marring or adding stress, and then cool slowly, or you are likely to add localized stresses that will bite you later, or at the least, distortion....but perhaps not a big deal in that area.

The glass transition temperature (Tg) of atactic PMMA is 105 ?C (221 ?F). The Tg values of commercial grades of PMMA range from 85 to 165 ?C (185 to 329 ?F); the range is so wide because of the vast number of commercial compositions which are copolymers with co-monomers other than methyl methacrylate.

sorry, not much help. If you ever want to kick the tires on a completed -9a for ideas or whatever, give me a call, I'm at YLW. (Kelowna)....but mines a slider.

dr cooper said:

I've made the 'big cut'. Now I'm doing final trimming and fitting.

The fit in the area around the right 'ear': the plexi doesn't seem to have enough bend in that area so it doesn't want to lay down along the side rail without considerable pressure applied.

Also, when it was made, that side didn't stretch much in the mold so it is just about full thickness of 3/16ths, which adds to the flexibility/fit problem.
The left side fits easier - it is about 1/8th"+ thick.

Can the right side be heated up enough to relax that tension? If so, how?

Gus at 'mothership' said not to apply any heat in that area, but just to make it work. I'm afraid of it cracking in that area at some point in its life.

Cliff
Chase, BC
RV9A, canopy

Click to expand...

This is one of the problem areas. This is what I did - I took modeling clay and covered the area, then pulled down the canopy. I had previously worked to ensure the canopy was very close to the drilling step to ensure the fit was not going to change. The clay was compressed and that showed the exact area to be worked - i really mean filed and hammered. Using files, hammers, and double flat rivet squeezers, it was eventually lessened until there was not a point loading. Repeated checking with clay ensured I truly knew what the high spots were. It fit quite nice after that.

Post some pictures of your problem area so we can be sure we are talking about the same thing.

Tip up Canopy

Sorry I can't insert photos - it is too complicated going by the directions on the forum.

Bill, may I just email photos to you?

Cliff's wife,
RV9A
Chase, BC

dr cooper said:

I've made the 'big cut'. Now I'm doing final trimming and fitting.

The fit in the area around the right 'ear': the plexi doesn't seem to have enough bend in that area so it doesn't want to lay down along the side rail without considerable pressure applied.

Also, when it was made, that side didn't stretch much in the mold so it is just about full thickness of 3/16ths, which adds to the flexibility/fit problem.
The left side fits easier - it is about 1/8th"+ thick.

Can the right side be heated up enough to relax that tension? If so, how?

Gus at 'mothership' said not to apply any heat in that area, but just to make it work. I'm afraid of it cracking in that area at some point in its life.

Cliff
Chase, BC
RV9A, canopy

Click to expand...

Cliff -

Definitely no heat.

Here is how I addressed this issue and getting the canopy to fit semi-properly. The goal is to get as the canopy to lay flat all the way around, emphasis on goal. Any pressure left in the canopy may very well cause a crack at a later date.

I trimmed the ears to almost non-existence. If I every do another I will cut the ears off. You will fiberglass over this area anyway. Here are two images taken during my trimming and fitting process.



You can see the area around the ear has been cut back to eliminate the pressure against the plexi. I wanted it to lay flat but not distort the plexi.



Here is a close up. On my canopy much of the outward flex on the sides was due to the fit on the forward compound curve. You can see the marks on the tape where I needed to bevel that edge. I was trying to eliminate the canopy sitting on a corner of plexi as it made that curve. The better I made that edge fit the better the sides fit. It was a slow process of sanding, fitting, sanding, fitting ...... Fortunately my wife helped me every time I needed to take the canopy and put it back on.

I hope this helps. Again this was my process others will probably chime in with their method.