The amount the an unlatched tip-up canopy opens in flight is dependent on a number of different factors.
There is an interaction between engine power and actual airspeed, but another is angle of attack (vs power vs airspeed)
Often times, if the canopy becomes unlatched in flight (if this does happen, the latching system should be carefully inspected by someone than knows how it is supposed to operate because if it is assembled and adjust properly, this should not be possible), it can be re-latched by slowing to a low but safe speed above stall and then deploy the flaps fully. This will make the wing fly at a much lower AOA which will make the fuselage be at a much lower AOA as well. This AOA/speed combination can often be enough to allow closing and latching the canopy.
Do this at your own risk; with appropriate measures taken regarding having a lot of altitude for safety, and another person aboard capable of flying the airplane while the left seater is distracted by and is manipulating the canopy.
I have taken-off, ONCE, with the canopy unlatched on my RV-6A. It was different than every explanation I've seen offered herein. Not to say they are wrong, just wasn't MY experience.
First, I was 100'-150' agl before it was clearly recognized as an unsecured canopy. Second, it was rising and floating a bit, up & down, which was somewhat disorienting because the glareshield was moving in my field of vision and distorted my perception of climb angle. I reached up with right hand and grabbed the handle but realized the futility of pulling it to closure. Was able to reach for the throttle to slow, get the nose down, then realized I was descending and about to pass over a row of off-airport buildings. Just 'flew the plane' to about 1,500-2,000 agl before trying to deal with it. With a steady slower speed, leveled-off, the canopy did not bob up & down, and with a slower speed the plane was very controllable.
Was able to clear the housing area (St John's Az) small town, and was then able to easily pull down the handle and latch it, then closed the canopy locking mechanism. For a few seconds thought of returning to land and make a fresh start, a little shaken, but this was the third day of a long cross-country and home was a little more than 1 hr away. Auto-pilot ON, and got back to concentrating on the last leg to home (KFFZ). Yes, there was a big distraction on the taxi/run-up, and failed to latch canopy. Might be much worse if this happened at cruise speeds.
The bobbing glareshield was the MOST distracting, disorienting. After slowing and knowing it was NOT a crisis, the rest was reasonably do-able. I finally plan to install the canopy switch option and connect it to the HDX for another check, after this year's CI. Oh, the T-handle is NOT for bailing in MY plane, label "GRND USE ONLY" for maintenance, convenient. Yes, you must release the gas struts to eject the canopy in-flight, complex concept.