Slider Frame Installation

What a shame such a nice kit has such lousy instructions to install the slider canopy frame.

This is the sequence I propose, please correct me if I am wrong.

1: Cut front bow, where rollers are inserted, to get 3/8" difference in height between top of roll bar and front slider bow. Mine is currently 3/4 " high


2: Move canopy slide rail (C762/763) fore or aft to place rear slider bow, at the top, 1/16" below rear skin.
(This should than make side bow parallel to the aft canopy deck ( F-721B-L), or within the specified 1/8", if not, I cant see anyway to adjust.)


3: Move on to checking side bows, inset 1/16" from fuselage shape.


4: Adjust rear bows to 1/16" below extended rear skin.



If installation of the canopy bubble will expand the frame 1/2" why do we only allow 1/8" as per item 3: above. ( 2x 1/16") ?

MY side bows are 1/8" inset, why adjust if the canopy bubble will pull them out?


Peter

You can try leaving them there, then drilling your canopy and then see how much the canopy pulls the bow out. I think the point you are at is just to make sure everything is even when the bows are at 1/16", cause that's where they will be when you're done. (?) The canopy frame is a pain to be polite. I spent 3 weeks (6 full weekend days plus numerous nights)working on mine to get it to the point where I was ready to move forward with actually attaching the plexi. It's a big learning curve, but you spend enough time and you'll get it.

Thanks for the reply, what about the proposed sequence, is that logical

Peter

Peter,

I'm bending the slider frame for my 9A now. I think your process is theoretically just fine. However, theory and practice are only the same in theory.

I've approached the fit slowly - I'm about 4 days in and I'm close to cutting the canopy. I've ground down the front bows twice to get the 1/4 - 3/8" that the plans talk about AND to get the front bow parallel to the roll bar. They were very close to parallel but 1/2" high, which had me perplexed in terms of finding a solution. Both measurements changed when I mounted the canopy slide rail and adjusted it to get the right height relative to the turtle deck.

I worked on the side bows before mounting the canopy slide rail. So far I've paid attention to the constant 1/8" inset and I'm darn close. I've watched and done little about getting the bows parallel to the longeron. Mine are off about 3/8" now. I'm not going to worry much about this as I think the skirts will cover them - but I may live to regret this decision.

My last move after getting the front and side bows close to correct was to mount the canopy slide rail. When I did this and got the height of the aft bow right, I realized I'd need to take more off the bottom of the front bows. This should get me down to the 1/4-3/8" difference in height and trimming the front bow tubes will also help make the side rails closer to parallel to the longhorns. I think the plans say up to 1/4" off. Mine will be around the max variation.

My suggestion is to go slow with both the bending and the grinding (or cutting). It looks like it would be easy to over do it.

As for why the 1/8" inset when the canopy will pull the frame out 0.5" (or more) - well, keep reading. There comes a point where you have to bend the frame in to accommodate the expansion that the canopy will cause. I've chatted with one builder about this, and frankly, it seems pretty flaky and loosey-goosey in terms of accuracy.

My intention, and oft times my intentions run afoul of reality which prevents them from happening, is to measure the frame before and after attaching the canopy (with clamps not drilling it). If the canopy pulls more or less than what I've anticipated, I plan to remove the canopy, rebend the frame accordingly, reattach the canopy with clamps and measure again. When it appears to be the right size, I'll move forward. I should know in a few days or a week if this is possible.

As for the directions being substandard, I think Van's is trying to convey what the critical measurements are for the frame. Since there are individual variations in the shape of each fuselage, the directions can't say, "do this, then this and finally that". I'm just surprised there isn't simpler way to approach the whole problem.

Van's instructions

Have a look at these instructions on Van's website
http://www.vansaircraft.com/pdf/canopy.pdf
The 1/16 is a measurement that you want to achieve as a consistent inset along the length of the side bows (it allows for the width of the canopy and the side skirts to fit snugly against the fuselage sides).
Get the canopy frame to fit properly on the fuselage before the plexi is fitted.
When you are satisfied with the frame fit, take it off and squeeze the frame at the front bow and a bit at the rear bow so that it is, without the plexi, too narrow by about 1/2 inch at the front, and just a little too narrow at the back - the idea is that when the plexi is fitted to the frame, it will pull the frame wider and if you have made it too narrow by just the right amount, the plexi will pull it bck to exactly the 1/16 inset you are looking for.
Posts on this site will warn against trying to bend the frame once it has been drilled for the plexi - it may crack at the holes. And never try to bend the frame with the plexi drilled to it.
What I did was once I got the frame the right shape, and squeezed the frame to account for the spread, I attached the canopy to the frame with lots of clamps (no holes drilled yet) and then could see how much the frame spread and whether it was right - it was then easy to adjust by further minor squeezing or spreading (having unclamped the plexi).
This way it is also easy to finally locate the roller tracks - the key is that they are parallel and the rollers slide in the middle without being pressed against a side.
I shortened the front bars for the rollers in stages - I left the last and final cut until I was ready to install the rollers.
The hardest part was getting the rear bow to match the rear deck - time mtaken getting this right will be rewarded with a good fitting rear skirt.
Bill Brooks
Ottawa, Canada
RV-6A finishing