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  #1  
Old 06-14-2020, 12:35 PM
Draker's Avatar
Draker Draker is online now
 
Join Date: Jun 2016
Location: Livermore, CA
Posts: 566
Default Getting a correct Big Cut trim line

Well, the weather in NorCal this weekend isn't going to get very hot, so I'm going to put off the big cut. This gives me another week to agonize over the cut line on my (tipper) canopy. I can't seem to get the top of the canopy less than an inch or so from the roll bar. I've trimmed and trimmed and trimmed (probably trimmed too much) and it still doesn't rest close to the roll bar. Van's says to draw the line "when you have gotten the fit to be somewhat close". Does 1 inch count as somewhat?



I'm worried that after the cut, when the canopy pivots down such that it can touch the roll bar, the cut line will no longer be aligned with the roll bar centerline:

Before cut:


After cut:


Am I overthinking this? I'm not sure I want to trim too much more since the existing trimming I've done has not really helped. I also don't want to put pressure on the top of the canopy to "force" it down onto the roll bar.
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https://stiletto.smugmug.com/RV7
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  #2  
Old 06-14-2020, 02:28 PM
jdiehl jdiehl is offline
 
Join Date: Jan 2011
Location: Williamsport, Pa
Posts: 186
Default Canopy fit

I share your concerns. It?s been 8 years since I dealt with this on my 7A tipper, and yes, it?s a time to slow down. My advice is to eliminate any stress points on the plexiglass around the front and forward sides of the canopy so that it comfortably rests on the tip up frame. Then secure (tape) the plexi to the tip up frame. I believe the slightly elevated plexi over the roll bar will not be a factor in the offset as it drops down a bit after the cut.
Good luck and take your time

Jim Diehl 7A
Based at KLHV
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  #3  
Old 06-14-2020, 02:40 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,577
Default

I would cleco the turtle deck on to insure there is sufficient overlap at the back to insure the plexi can be screwed to the skin all around. Maybe leave the side clecos loose so the plexi can slip under the forward sides.
I would continue trimming the front of the plexi (w/s area) back till the plexi dome lies very close (vertically) to the rear canopy frame/roll when the bubble is draped over the fuselage structure.
Then you can mark the plexi for the big cut.
After the cut, trim the sides of the canopy plexi to their final shape.

Bringing the dome height down dictates your plexi front/back positioning, which locks the big cut location.
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  #4  
Old 06-14-2020, 10:21 PM
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Default

Quote:
Originally Posted by Ralph Inkster View Post
I would cleco the turtle deck on to insure there is sufficient overlap at the back to insure the plexi can be screwed to the skin all around. Maybe leave the side clecos loose so the plexi can slip under the forward sides.
I would continue trimming the front of the plexi (w/s area) back till the plexi dome lies very close (vertically) to the rear canopy frame/roll when the bubble is draped over the fuselage structure.
Thanks, Yea. I still have plenty of overlap in back to attach to the turtle deck skin. After a little more work, I'm about 3/8" to 1/2" from the top of the roll bar. I don't think I'm going to be able to get closer than that. Another builder suggested I make the big cut line a little farther aft on the roll bar and then square it to the roll bar centerline later. That also sounds like a good idea.
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  #5  
Old 06-15-2020, 09:00 AM
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sahrens sahrens is offline
 
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Location: Battle Ground
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Default Mine was was an inch high at first

My canopy also set about an inch too high at the roll bar. I kept trimming the forward edge to improve the fit on the fuselage skin which caused the canopy to get closer to the roll bar. When I made the Big Cut the canopy ended up just a little long at the roll bar, which I eventually trimmed/

http://www.mykitlog.com/users/catego...&category=9962
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  #6  
Old 06-15-2020, 03:19 PM
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robertahegy robertahegy is offline
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Trim it close, make the cut, then finish the trimming. The canopy will rest on the roll bar and then finish trimming the side skirts and the joint between front and aft pieces. Cut the front a bit long and trim it to set nicely on the roll bar. Then trim the aft section to set about 1/8" from the front section aft edge and also set well into the aft upper fuselage sections.

It's best not to get too aggressive before the cut, because you will still have a lot of trimming after the cut. Just get it close and I think you are there. We all anguish during this part of the build. Once it is done, it seems to go a lot easier.

Roberta
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  #7  
Old 06-19-2020, 05:12 PM
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Thanks for everyone's advice -- again! The big cut went smoothly. I decided to mark the trim line 1/8" aft from the center of the roll bar. This resulted in the post-cut sides matching the centerline exactly, and 1/8" too far aft on the top, which can be easily sanded away.



Obligatory "Larry pose" with the Saw Max:

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RV-7A (N12VD): Finishing final tasks for engine-start and airworthiness!

Last edited by Draker : 06-20-2020 at 05:42 PM.
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  #8  
Old 06-19-2020, 07:27 PM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
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Hey Ryan,
Nice job!! I have made cuts on several canopies over the years, and the last one I did was with the tool I see in your hand. To me, that is the best tool ever for the job. Quick, easy, and a smooth cut - which is very important. Congratulations on an important part of your build!! A hangar neighbor borrowed my tool to make his cuts on his RV7A and they all came out beautiful. Good luck going forward.
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RV6/2001 built/sold 2005
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  #9  
Old 06-20-2020, 04:28 PM
rapid_ascent rapid_ascent is offline
 
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What tool is that?
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  #10  
Old 06-20-2020, 04:34 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
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Default Dremel Saw Max

Dremel Saw Max. It comes with a SM500 blade for plastic. Cuts through plexi and fiberglass like a hot knife through butter.
https://www.homedepot.com/p/Dremel-S...0-03/204331723
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Donated 01/01/2021, plus a little extra.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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