How far do you have to pull the frame together with the glass installed to get it to bend about 1/2”? Can you elaborate on the process you used?
I sort of feel that posting info like this is similar to giving someone written instructions how to play the violin... I don't know how to play the violin, but my daughter does (very well actually) so I know that there are a lot of things to know that just come from experience and practice.
But, I will give it a shot (be sure to read my disclaimer in my signature).
If someone chooses to try this they should carefully weight the risk versus reward.
Also consider the fact that the level of care that was taken drilling and final finishing holes and edges of the canopy while it was being installed can also have an influence on how risky doing this is.
Bottom line - There is a risk of cracking the canopy doing this but I have adjusted 3 different sliding canopies without inducing any cracks.
First figure out how much too wide the canopy frame is by removing one side from the roller bracket and let it spring out to where it wants to be and then measure the displacement from the roller bracket.
Reinstall the frame in the roller bracket and with the canopy fully closed, try and determine if the canopy is lower at the top just fwd of the latch handle than would be ideal (look at how it is fitting relative to the molded fiberglass or formed metal fairing that the canopy slides under). What you are trying to determine here is if the canopy has been pushed down excessively at some point, inducing a bend at the top center. If this has occurred, it will cause the canopy to get wider down below at the roller brackets.
If you are the original builder/owner and you know that the canopy has always been dragging because it is too wide, you can skip this step, but if the top center is too low, this is the area where you will be focusing on first, when adjusting the width.
If the top of the canopy is at the correct height, then the bending adjustment needs to be focused in the area of the tightest bend radius of the front bow (about the 10:30 and 1:30 points on the frame if viewed looking forward from the center of the cockpit. Adding a small amount of additional bend at these two points will cause the bottom ends of the front frame bow to translate inboard on both sides without changing the overall shape an appreciable amount.
The sketches on the second page of
this document might help with understanding the concept. The text may be helpful in developing a strategy for applying the bend force where needed.
Bending-
Only do this when the canopy has been normalized to an ambient environment temp of at least 75 degrees, but the warmer the better (don't try and warm the canopy when conditions are colder)
Start by writing down the measured width of the frame before you start. Subtract the amount you determined it was oversized so that you have a specific dimension to shoot for.
Put some soft blankets / towels on the floor.
If bend is needed in the top center of the frame you need to first remove the latch handle.
Then put the canopy upside down with a padded wood block on the floor under the front bow, about 12" to each side of the canopy center (where the latch handle was). You will need a helper to lift the back of the canopy a bit so that the blocks are laying flush on the face of the canopy at the location of the bow, and not pressing on just the canopy aft of the bow.
Pull inboard on bottom ends of the front frame bow, while applying pressure with your foot (wear a soft soled shoe) downward on the center area of the frame bow. Some short wood dowels or pieces of tubing that fit inside the frame tubes closely, can be inserted to give you a bit more leverage. The force required is pretty high, and there is a lot of spring back, so you need to go beyond where you want it to end up.
It is best to make many tries and measure after each, increasing the force each time until you start to see a dimension change. Then you will have more of an idea of what level of force is required (part of the process of learning the violin
). Move your foot around a bit with each attempt so that you are not always focusing the force on just one spot.
If you have determined that the bend adjustments are needed at the tight radius bends, the basic process is the same (measure, check, etc.) but inducing the bending force is a bit more difficult because of awkwardness and the need to keep the bend focused in a narrow area.
Have your helper position the canopy upside down with the aft end once again lifted and the canopy rolled about 45 degrees to one side so that the mid point of the tight radius bend of the front bow is tangent with the floor. Make sure your helper is holding the canopy up properly in the back so the primary contact point to the floor is right at the edge under the frame bow. Pin that point to the floor with your foot and with both hands pull the end of the bow and the point where the latch handle would be, towards each other.
Once again, it takes a lot of force, but I am not a huge muscle bound guy and I am able to do it. The important thing is to slooowly work your way up to the point that a change starts to occur (keep checking with the tape measure).
You may also have to do adjustment at the top and the side bends depending on your situation (canopy on and off the airplane a few times for fit checks may be a good idea). I.E., if the height of your canopy appears low, don't assume that you can entirely correct the width by only making an adjustment at the top until the width is correct. You may then have a canopy that is too tall in the center.
