chepburn

chepburn

Well Known Member
No...it didnt crack but,
Having persuaded the rear bow into position with the help from all of you with an earlier post, I am now wondering just how close the aft canopy sides are going to come to the rear bow on the sides. The windscreen section is fitting 'pretty well' (needs a bit more trimming/sanding)...there is about 1/4 inch to go to touch the roll bar.
The aft end of the canopy has had its 'first cut'. Now, I have to press in, and down, to get the sides of the plexi to touch the frame..not a lot of pressure, but in my opinion, a little too much. (I have -not- started to notch around the vertical frame members yet..but I expect to)

Should the canopy sides touch the frame almost all the way to the aft end? Or did all of you have to pull in the aft sides with the rivets? What is an acceptable gap that can be pulled by riveting?

I'm hesitant to keep on cutting...I dont think thats the answer....

Any advice?


Thanks,
Chris
 
Should the canopy touch the frame?

Chris, I have just completed the last of the trim work on my canopy. My canopy must be pulled in about a half inch on each side by my clamps. I will be using sikaflex instead of rivets. On my canopy, the sides must be pulled in until I get within about a foot of the aft end from that point aft, it fits well.
 
Pull sides in

I recall having to pull the aft section of the canopy in quite a bit to get it to fit. It seems excessive, just go gently and you should have no problem.
Be careful that you don't trim too much away on the rear of the canopy.
It is easy to get carried away and take off too much. This will make sense as you progress and bring the canopy down to meet the frame.
 
Make the big cut

Be careful not to cut too much off the bottom in an attempt to get the canopy to rest on the roll bar and canopy bow. You can cut it too short from front to rear and not get it to rest on the bows. Go ahead and cut the canopy from the windshield. This will take all the fight out of the canopy and the two parts will immediately lay down on their respective bows. Things get easier after the big cut.

Use a Dremel with a sanding drum to notch the glass to fit around all the vertical frames. That will help the canopy to sit on the frame better.
 
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OK...Off to the big cut then

Thanks all,

Well, I believe I have sufficient fore and aft plastic. I dont think I want to cut any more off the sides. I have been waiting for general opinions here before I did any more...another builder in Ottawa has also recommended going for the big cut before I go any further on the sides.

Well....here goes nuthin...

Chris
 
Well, that want so bad after all...

Thanks all,
I did the big cut, and yes, it looks like its going to be a LOT easier to work the aft section now!

Here's the requsite pic.....
canopy1.JPG


Now onwards and upwards....

Chris
 
I have completed using Sikaflex to glue the canopy and can echo the comments made about having to bend in the sides quite a bit at the front and getting close to the back but the rear portion fit well. I did the windshield with Sikaflex too but after the canopy was glued and adjusted the spacers so that the plexi would line up on each. I suppose it could be done in reverse just as well. Really not a problem as it is very flexible and you want it to bend inwards to fit the skirt better.

After getting everything glued then the question comes up as to how to attach the canopy skirt. I have just about finished getting the shape right using clecos to hold it in place but with no holes through the plexi.

I left an overlap of about an inch and a half to two inches at the back of plexiglass but it is not possible to leave a large overlap on the sides. In the way of the skirt. More on the rear overlap in a minute. My intention is to glue the skirt on with Sikaflex using clecos on the frame everywhere but through the canopy drilled per the plans. At the back where there is no frame the skirt would be glued to the plexiglass. The extra at the back will provide more surface area for the glue. After this is done I will decide whether to drill out the holes with the clecos to #30 and put in the blind rivets or just glass them over. Probably I will put in the rivets. My concern has been what to do in the back because there can be considerable stress placed on the bond between the plexi and the skirt when the canopy falls into place or when it is opened by pulling on the loop I placed at the back to use to yank it open. My solution for this is likely to be removing the canopy after it has been glued to the frame and at the back glassing over the overhang of the canopy to the skirt. This will make it impossible to pull the skirt up and away from the canopy at the back and still avoid any drilling of the canopy. I don't know how others have addressed this but my current plan is as described. Any comments welcome.
 
No, did not remove the powder coating prior to gluing on the canopy and the windshield. As the Sika instructions point out it is not a problem to adhere the powder coating but it should be sanded first with #80 grit to improve adhesion. The bottom line is that adhesive bond strength of components like this is a function of the area bonded and the ability to distribute any stress across the total area. The adhesion of the powder coat to the steel is more than sufficient to provide sufficient bond strength to the underlying metal after the plexi is bonded to it over the whole perimeter. Having said this I don't think you would have a problem if you removed the powder coat if it was bonded immediately. The 4120 steel with corrode very quickly once exposed and this could compromise adhesion. In my opinion the powder coat provides excellent protection against corrosion and prefer not to disturb it.
 
I hear what you are saying about the adhesion of the powder coating but unlike the SIKA I cannot find and data that supports what you are saying. Not saying you are wrong in your assertion I just cant find any research showing that the LONG term (measured in years) adhesion of powder coating is at least as high as the SIKA. If it is not then the question is, is it enough?
 
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