R

RV8R999

Well Known Member
Having received my Todd's canopy this week, I've started the fitting process in earnest. Not sure how Todd's compares with the VAN's standard but I will say go very slow in trimming as there is not a lot of excess. In fact from the roll bar to the aft bulkhead of the cockpit I wont need to trim anything. Only an 1" or so roll bar forward and several off the rear.

I'm almost ready for the big cut but am contemplating a different approach based upon what I've read about alignment issues between the windscreen and canopy section after the cut.

I'm going to glue the entire canopy and windscreen in place prior to the "big cut". I can reach in front of the roll bar aiming aft, behind the canopy bow aiming forward and the top and bottom edge of the canopy frame all the way back to the aft cockpit bulkhead. I'd leave the rearmost part unglued until the rest has set and the big cut is made, but will have a couple of clecos holding it in place. At that point I'd remove the canopy and complete the remainder of the gluing process for both the windscreen and canopy.

The work will be to have all the tape laid out and everything prepared. The glue job while it is on the plane only needs to cover enough to hold the assembly rigid while the big cut is made and while completing the job after they are separated. I would SIKA the windscreen to fuselage skin at this time as well to preserve the exact alignment as well as having the skin prepped for paint on the interior cockpit side. I'm going to use my wife's marinade injector (shhhhh :) ) filled with SIKA to get to all the joints through the open skirt area. I did a dry run and can easily reach everything from the outside reaching in.

I understand the SIKA cures pretty quickly. I'd do the windscreen section first. Pull the tape and move onto the canopy bow, pull the tape, then onto the canopy sides. The rear section I'll prime and glue separately after the assembly is carefully removed.

At my current fit I have the canopy resting nicely on the spacers I put on both the rollbar and canopy bow (about 1/8") I can't think of a better way to preserve EXACTLY the natural alignment of the two halves than to ensure they are rigid prior to the cut.

Also, FWIW, I've found using a dremel and cutoff wheel the easiest way to trim the plexi. I've been taking a lot of in process photos and will put together in a PP when I'm all done (if it turns out well enough :) ).

Ok..fire away!!! Chaff and flares, chaff and flares!!!!
 
I tried a rotozip tool, it was hard to control.
I liked the little discs Vans sells, with the chaepo mandrel that fits the dremel or an air die grinder.
 
what type of dremel to cut the canopy

Only a little OT - but related since you mentioned the dremel. This is the 1st time I've seen anyone use a dremel with the Vans disc. What type of dremel did you use? Mine is an old handheld, variable speed model. I've never put a disc that large on it... and I didn't know you could. How fast did you run it?
 
I don't think the average dremel has the stones to run a 3 or 4 inch cutoff wheel like Vans supplies for the canopy. At least not the hobby model I have - it just bogs down. Works great with a 1 or 1.5" wheel though.
 
I burned dremel out just doing regular trimming. Dremel customer support was awesome though. Sent it to them and they sent me a brand new and improved model along with a couple of trinkets.

I cut my canopy with a RotoZip with the 90 degree attachment/speed reducer. That thing is wild. Really awkward to work with but the high speed made cutting the canopy just like butter.
 
Gutsy move

It's not clear to me what advantage you hope to gain by trying to glue the entire canopy prior to making the big cut. Sounds like it would be very challenging to appropriately apply the Sika. I had my hands full applying the Sika to my canopy and I had my canopy on a frame where I could stand up and work on it form both the inside and outside. Maybe it was overkill but I applied the Sika from both sides of the resulting joint (front/back, top/bottom). I also purchased a bunch of extra tips and cut the ends so I could vary the size of the Sika bead. Sometimes you want a small thin bead while other times you need a large thick one.

The big cut was a non event for me. The resulting cut was not as clean/straight as I wanted. A sanding board made quick work of that problem. Once I had a nice clean straight line I glued the windscreen.

I am not sure what you mean about significant alignment problems after the cut. Keep in mind that because your using Sika it is very easy to align the canopy with the windscreen. You can use various thicknesses of shims to get the alignment perfect before you glue the canopy onto the frame.

Sounds like you way will work as long as everything goes along as planned.
 
Hi Ken,

It ha been a number of years since I id my RV-8 canopy, and I did a stock canopy, not one from Todd's - so please take these points as caveats for my thoughts.

What I fond (and read from others before) is that the canopy and windshield take on completely different properties once they are separated, and fit quite a bit differently - better, actually, than when joined. Many folks get very frustrated trying to get the uncut canopy to match both the roll bar and canopy frame at the dame time, lose weeks worrying about it, and then, when they make the "big cut", both of them settle right in to place. Yes, there will be some misalignment as each seeks it's own form on their respective frames, but the fiberglass you'll lay up will make them match, and as mentioned above, using Sika, you'll be bale to control the fit even more.

Now if you are sue that you have a great fit just like you are, then you may be right where you want to be - but you're definitely out on the far end of the bell-shaped curve fastening first, then cutting. There's a risk to that. Lots of folks have fit it, cut it, then did final fitting, and it works. Your way may work better - but you may be a pioneer.

My thoughts only - you're the best judge of the fit you've got. It will be interesting to hear how it turns out.

Paul
 
If you fit the whole canopy and glue it down before you make the big cut, there will be a gap which equals the width of the saw kerf, plus any polishing you do to make the edges fair. That could be 1/4 inch. If you cut first, then fit, then attach, you can get that fit down to '0' if you want.
If you fit the canopy with the frame retracted 1/4", it will be high at the back, and you will have a wedge shaped kerf when you fully close the canopy.
If you follow my link and gop thru my pictures, you can see some of my crude but effective canopy job. You can make a better finish, I found out about edge finish and surface smoothing after I did mine :( But I'm still happy with it, and not embarassed.
 
I agree with SHIPCHIEF...

I SIKA'd the canopy on my RV-7 and in my opinion it was relatively easy making the BIG CUT before gluing the canopy to the frame. I would think it would have been much more difficult had I glued the canopy to the slider frame and roll bar prior to making the cut. By cutting first, and gluing the canopy frame first, you have a lot of control of the fit of the windscreen using spacers to match the slider portion very precisely. YMMV.

The tool I used to make the cut was this:

http://www.cporyobi.com/products/zrag402.html

It cut the canopy like butter, was easy to control precisely, and I had absolutely no problems. I couldn't imagine using anything else. A Dremel tool or Rotozip would be out of the question.
 
ok I chickened out and cut the "big cut" the normal way. By the time I was ready after much trimming, the canopy sat nicely on both the rollbar and canopy bow. I realized not much would be gained by my suggestion as you folks pointed out.



The dremel tool with 1" cutoff wheel worked perfectly and was very, very easy (like butter) and easy to control. Best of all the kerf is only about 1/8" after sanding (not that it really matters).

Thanks for all the feedback!

Ken
 
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