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canopy attachment in aft frame area

Kato's 8

Well Known Member
Hello all!
I hate to bring up another canopy question and certainly dont want to start another rivit/screw,glue debate but.....
I had called Vans and asked about the aft end of the canopy just past the "no rivit" area and how I'm unsure of the fit there. It seems to require significant pressure both in and downward to get it against the steel in that region. It does clamp down though. Is that normal? The tech guy said he didnt even rivit the last 6-7 inches on his -4. Im qite nervous about drilling that area and then riviting or screwing it down only to release the clamps and watching it expolde!
Can anyone comment on this some?
2nd question is: Should I use riv-nuts or just tap and screw in (assuming I go the screw it down method? Ive read some posts where those who have used them would not use them again.
Thanks a bunch!
Bill
 
Aft Canopy Fit

Bill,
I'm not sure from your post whether you've made "the big cut" to separate the windscreen from the slider.

Once this is done the slider portion is much easier to work with and in my case, the aft fit was good without a lot of clamping pressure needed once the cut was made.

Obviously, the aft portion of the frame must sit properly on the fuselage in relation to the slider track for the best fit. A small change in the aft "hoop" position vertically will change the canopy-to-frame fit quite a bit. The plans give the dimension and I made a small block/spacer to fit between the track and the frame to keep the frame from drooping while working on the canopy.

Hope this helps,
Mike
 
Bill,
I've done a bunch of RV8 canopy's now. I've found, that after you have the canopy front windscreen portion trimmed, and the whole canopy sitting down on the windscreen bow, I make the "Big Cut".
Then I remove the canopy frame and set it on a bench. Then I begin clamping the canopy from the AFT end and work,my way fwd. This way puts way less stress on the canopy as you clamp it. The lower front edge of the canopy also "grows" fwd as you clamp. I just re-trim the "Big Cut" here. I used to do it the opposite way (clamping at the fwd side and moving aft), and found the situation you describe. Trust me on this one. The aft skins also seem to fit a lot better with the "new" way.
Just an additional tip on getting a good "aft skin" fit, The skins will nest/fit pretty well in the cockpit area. Drill and clecoe them there, then get a helper to pull the aft part around the aft canopy, and also exert some forward pressure on the skirt. You will see the gaps with the turtle deck disappear. You drill while your helper maintains pressure on the skirt.
Good luck!
 
Thanks for the kind responses. I failed to mention that I did have the windscreen separated from the slider and am now fitting the bubble to the frame. I was trying different ways to clamp this down and found just as Jon said that it goes easier starting aft and working forward. I too seem to have more of a front lip than original but it can be final sanded. I also need to get up to chapter 91 to see if I can visit with those folks. Thanks Mike!
Im thinking Ill try drilling this and riviting as per plans. Ive seen where Dan kings new bubble is being done with holes drilled open to 1/4 inch and then 1/4" od tube installed to protect and help center the screw or rivit. Any additional thought on this or tips would be appreciated.
Does anyone know if the "todds" canopy fits better on theaft area sides? Mine has probably 3/4 inch on each side in that no rivit zone. Seems like alot to me.
Bill
 
Todd's Fit

I started with Van's and switched to Todd's. Both fit about the same in the front part of the slider, but the Todd's fit better in the aft portion.

I had about 1/8" to 1/4" gap with the Todd's. Perfect gap for Sikaflex in most places and minimal clamping pressure required against my spacers.

Having said that, the Todd's is thicker...so if I'd been using screws it would have taken a lot of pressure to squeeze it inboard in the aft end.

Best,
Mike
 
It's always frustrating to take the time to give a very qualified response to a post that asks for some help, and then have it second guessed by someone working on their first project. The standard Van's canopy and frame fit Freaking perfectly!!!!!!!! Not only have I done 4 of my own, I've assisted on 4 others locally. There is NO misfit of a standard Van's canopy and frame!!
The Todd's canopy may fit as well but it doesn't fit Better!
Excuse me for sounding harsh, but I've been at a baseball game today and I've been drinking!
 
On Second Guessing

Jon,
I switched to Todd's because of a crack in my Van's...long story, but I've fitted both brands and my experience is as stated above.

No one was "second guessing" your response; just tried to answer the question about relative fit.

Best,
Mike
 
Sorry Mike!
A lot like "drunk" dialing, maybe someone should take away my iPad when I've had a few!:D
 
Moderator Plug

Jon,
No worries-and I'll throw in a plug for you and the other moderators on VAF:

You guys do a great job-please keep up the good work.

Thanks,
Mike
 
mine too, Bill

Bill,
I am experiencing a similar problem to your description. Wish I had heard of Mutha's aft end first technique before I went the plans route. Anyway, my canopy appears that it would have fit very well had I not adjusted the aft end of the frame for the slider clearance. As mentioned in an earlier post, the little bit of adjustment in the frame now leaves a 1/8" to almost a 1/4" gap between the canopy and frame when solidly clamped all the way around. I plan to throw some Sika adhesive around that rear portion to seal it up and press on. Maybe my next RV-8 will be perfect.
 
I have been trimming the forward edge of a Todd's canopy for 5 days and it seems to have found its "sweet" spot, as defined by Mr. Todd himself. It's final resting spot is about an inch aft of the Vans 3.25" mark aft of the bulkhead line but I agree with the boss, than is not important. What's important is that "sweet", which in the beginning sounded like voodoo to me, but now I know what he was talking about. The canopy is resting on much of the roll bar and the cut along the forward fuselage is nicely snuggled in.

I will remove the canopy and do at least one more small cut today to get the side in a little closer at the canopy latch hole and adjust the cut out grooves at the vertical bars a bit. Also the card board "big cut" guide needs to be traced and cut.

The aft end has been trimmed twice and now ends about an inch forward of the curve of the frame. Mr. Todd says this is ok, he has done 2 RV-8 canopy's and says the more you can trim here the better as long as the skirt will cover it. The canopy sides will bend into the side rails easier.

My question at this point, have your guys been trimming the bottom sides before or after the big cut? Seems like that trimming would be easier to manage after the canopy is in 2 pieces.

With regard to the wind screen, are you-all gluing it to the roll bar or using screws? Seems like the wind screen could be glued to the roll bar without issue. With all the fiber glass work forward and across the top, it won't be leaving the airplane easily.

Thanks.
 
I had the same problem and was pretty worried about it. What I found ON MY PROJECT was that I was putting to much faith in that dimension at the front (front of canopy to rivet line). In other words I would like the canopy up on that dimension and trim to fit. In reality, the canopy gets shorter with every trim so that line means nothing until the end. I was standing there staring at it, wondering why the aft end needed so much pressure to contact the frame when I had a revelation. The canopy gets skinnier the further aft it goes. I undid all the clamps, shoved the canopy two inches forward until the aft end fit perfectly and then trimmed the front to fit. Voila, Perfecto!

Your mileage may vary. I'm a first time builder and my knowledge is appropriately limited, but that's what worked for me. Luckily, I have a guru named Jim Gray here in town who had told me several times that when he fit his canopy he had very nearly cut too much off the aft end by accident. So, even when I believed it ok to do so, I refused to cut the aft end to fit and only cut it enough to clear the fuselage....had I not done so, I wouldnt have had that two inches to spare. Yet another reason why my project would be much more difficult without Jim around. Thanks Gringo!
 
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If I remember right, I think I trimmed some off the sides all the way around while still in one piece. I had a center line mark on canopy and the roll bar too so that when the big cut was made I could line up the canopy again and clamp. At that pint I simply marked the final trim line around the sides and cut.
 
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