J

JVolkober

Well Known Member
I am looking for advice and comments from experience builders. I?ve got a problem and it is keeping me up at night and taking away from the fun of the build.

I building a -9A.

After six months of bending and twisting, I thought I had the frame in adequate shape. With the canopy drilled and clecoed in place, the lower rear bow cleared the aft skin by less that a sixteenth inch when sliding the canopy back. I now find that I missed something. The lower eight inches of the left rear bow with the canopy taped in place falls one-eight to three-sixteenths inch below the extension of the rear skin. After attempting to fabricate a fiberglass rear skirt, I am realizing that I will be unable to hide this error. The skirt will not be flat but will slope upward from the canopy to the rear skin than then bend flat against the rear skin. Ugly. So, the options I am considering are:

1. Live with it. I suspect I will want to sell the plane a few years down the road. My fear is that this will take away from its appeal and potential sale price. Furthermore, having this flaw is definitely a downer.

2. Attempt to bend this small part of the rear bow into a proper fit. All holes including the side skirts have been drilled to the canopy. Vans advises against this due to future stress on the plexi because the holes in the frame ( I assume in the rear bow I am bending) will not align with the plexi. I figure I could slightly enlarge the plexi holes to compensate. And if all else fails go to option 3.

3. Purchase a new frame and canopy for an estimated $2,000 and start over. What?s another two grand in the context of the total cost of the project and potential resale.

What would you recommend and why?

Oh, and if you live in the San Francisco North Bay and could provide an experienced helping hand, I sure could use it. In fact, if you are interested in flying in to Gnoss field and giving me a hand, I?ll pay for your fuel and lunch. Ah, the pleasure of building.
 
John,

Give me another call tomorrow at Vans and we can further discuss your canopy frame. I have some ideas that may get it to work....
 
Fiberglass

Hi John,

I struggled mightily with the canopy and skirt on my 9A as well. I am not sure I can visualize your problem, but I do know FG can be formed and blended to to hide lots of problems(or so I hear, as I had no need to do it on my plane in any area;) )

I'll bet Joe has a good answer - but if not, make both side symmetrical and just tell people the unique shape houses the flux capacitors for your positronic plasma ignition.....

Post some pics and the suggestions will flow........
 
I made a personal build rule on my RV-6A slider

I made a personal build rule as I built my RV-6A slider to build for perfection but never rebuild anything. Finding a way to salvage every imperfection inspired me to think ahead better and not waste resources. As I understand it you went through a lot of effort to closely fit you canopy frame to the fuselage skin and now you have the frame below the skin when the canopy is closed. First of all I do not know how an RV-9 sliding canopy is configured exactly but I imagine it is similar to mine. The skirt is supposed to provide closure between the sliding canopy and the fuselage skin so the frame fit is not required to be that close.

Perhaps you can change the plastic center slide block and the closure pin blocks to reposition the rear of the sliding portion of the canopy higher relative to the fuselage skin and longerons to the extent that there is a smooth straight (not concave) line following the surface of the canopy to the fuselage skin when the canopy is in the closed position. If so, install the oversize rear skirts and verify that the canopy will not close because of the interference of the skirts with the fuselage skin. If you can achieve this condition with your canopy then you should be able to block the canopy travel so that it cannot close and cleco the skirts in place and mark them with a blue Sharpie pen to show how much you want to cut off for a fit in this blocked open position. Remove, cut, reinstall, remark, remove, cut, reinstall, ... until you are satisfied that the contour of the skirt edge conforms to the fuselage skin contour. Then remove the "hold open" block and replace it with a smaller "hold open" block and repeat the process of clecoing, marking, trimming, ... until you have the canopy completely closed (no "hold open" blocks) and the rear skirts just touch the fuselage skin when closed.

I use a white "P" strip rubber seal attached to the underside of the skirt set back an appropriate distance from the edge to give an air tight seal in this area. The canopy is an area that will develop some craftsmanship if you really focus on it and do what you have to do to get it right no mater how long it takes. I wrote up some of the modifications that are in mine several years ago for this site and they may be helpful.

In 1955 I was stationed at Hamilton Air Force Base and I drove through Novato often but now live in Arkansas so I can't drop by and help.

Bob Axsom
 
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If the plexi is below the skin in the back, could you put shims between the frame and the plexi to bring the canopy flush to the skin?
 
Can't you adjust the angle of the front nose of the slide track so that the plastic sliding block rests higher up on the slope? I played with this angle for a while trying to get mine to fit.
 
John,

Find a guy with a metal shrinker and let him massage that area a bit. It won't make it perfect but it will be better and certainly good enough to fly.

I've got so much air coming through my airplane due to the canopy, its like driving around in a convertible. I don't worry about CO2 and it facilitates air coming in through the heat system when that valve is opened. The front cabin area is better heated than it was with the hot water Subby heater with a fan. And in the summer, there is always a nice breeze through the fresh air vents.

Beyond that, you're building the airplane to fly and I assume not to walk away with a national award. In flight you won't think about it or notice it and neither will anyone else. None of these machines are perfect, just varying degrees of perfect based on the amount of money and time spent on it. The canopy was the most hateful part of my building experience (I've done 2 of them) and if Van's had offered a preformed frame and glass, structurally sound to open in flight, I would have gone for it. As it is, the slider roll over bar and frame are not bent right for the fuselage and the skins require dark magic to get them right.

It is all part of the 51% rule, keeping costs down on the production end, and we have to deal with it.

Press ON!!
 
Thanks all for the Input - the Fix

Thank you all for you input and particularly thank you Joe for taking the time to discuss further.

Joe suggested using a combination of 1) shimming by placing shims between the bow and the canopy and 2) adjusting the anchor blocs to lift the bow a bit.

Solution: I shimmed the lowest four holes on the problematic left rear bow using -10 washers, starting at the bottom - 2 washers, 3 washers, 3 washers, 2 washers. This brought the canopy into alignment with the rear skin.

The downside is that several holes in the plexi no longer aligned with several holes in the bow and the side skirt. After drilling the rear bow holes to final size, I corrected for this by enlarging the holes in the plexi - the lowest two holes in the rear bow and the rear most three holes used to attach the side skirt. I also decided to use number six screws to attached the plexi to the rear bow, which I think will work better than rivets with the slightly enlarged holes. I came across a couple of other holes that appear to be misaligned, perhaps because I did make a very small adjustment in the left and right rear bows after I had drilled them. I planned to enlarge these as well to reduce or eliminate sideways stress on the plexi.
 
John,
I had a similar problem when I accidentally took out some of the curve in the rear bow as I was working on the side rails. I didn't see it until I had drilled the canopy frame, and I can tell you it will break if you try to bend it:mad: I cut out the bad one and welded in a replacement that I formed by hand. It was actually so easy I cut the other side out so that I could really tweak the frame shape.
 
Same problem on the aft bow of canopy ---

I had the same problem with my 7 canopy. I was drilling the side skirts and noticed that the left aft bow was now lower than the turtledeck skin (even though I had measured it at each step!). I saw this post and went back out to the hangar...

I removed the screws in the anchor block on the left side and raised the anchor block about 1/16 inch. What a difference! Now the left aft bow of the canopy was right back where it needed to be! Apparently when drilling the anchor block down to its holder, it got pushed down ever so slightly. I made a new anchor block and holder and I'm back in business! 'Hope this helps someone else who has this problem.
 
Why not sikaflex it?

You can shim to any desired height, don't have to worry about redrilling holes, etc.

I drilled my first canopy, like you, many many hours of shimming, fitting,cussin' and discussin'.

Sikaflexed the second one. Much, much easier. Fits like a glove, no rattles. Strong and tight.

It's not too late if you have not put in the pop rivets. :)
 
what kind of skirts do you have?

Hi Joe - I'm with you so far on the Sika route. Did you do metal rear skirt or fiberglass? I assume you Sika the side & rear skirts on too?
 
With help and advice from another builder at my airport I went for the complete FG skirt. I couldn't be happier. My canopy is sika'd on. I had problems with the canopy being slightly high (1/8"?) along the rear in a few places. I think most of the problems were caused by the "ski jump" left from the canopy molding process. A belt sander took care of that, and sanding/filling has cured all else that ailed my skirt. I've trimmed it since these pictures and will glue it on soon. I still have to decide what to do with the skirt brace, whether or not to use it, and how to attach it.

IMAG0053.jpg


IMAG0077.jpg
 
Update: Drilled but Not Riveted

I may have mentioned this at the close of the original thread, about eight or nine months ago. My solution was to shim the canopy with washers at the low point, up to three washers at two points on the lower left side. This resulted in having to "oval" a couple of the rear most holes attaching the side skirt. I have since placed the whole shebang in temporary storage in the basement and moved on to engine, baffleing and cowling. It gives me the shivers to have to go back to the canopy, which I will do in the next three months or so before the weather turns cold. (I wonder it it work with an open cockpit?)

Question, it was suggested that if I haven't pop riveted everyting, I could move on to sikaflex. First, this will rase everything front and back about 3/8 inch for the sikaflex moving both the front and back bow out of alignment. The back I can adjust by moving the slider track. The front appears to be a different story. I have drilled the holes for the roller wheels already. Second, what would I do with all the drilled holes, particulary on the front bow?

While I'm at it and since this thread is alive again, I found that when I screwed the side skirts to the plexi, the skirts puckered between the screws. My planned solution for this is to sikaflex the side skirts to the canopy first and then, for cosmetics, attached the screws but not so tight that the skits puckers? What do you all think?

Ah, its nice to share my delemas with others. Thank you for the input.

John
 
Shoot I thought I was the only one who had spent 6 months bending my canopy frame! In my opinion it is all down hill from the canopy:) I like the idea of adjusting the rear canopy blocks a little, and possibly addjusting the angle of the sliding rail.
 
Why 3/8"?

Hi John,

You mentioned this last weekend and I didn't follow why 3/8"? To do the Sikaflex, you need about 1/8" to 3/16" gap between the bow and the plexi. It sounds like in the back, you ended up with about that much in shim washers anyway to get the plexi to fit tangent to the skin. So, if you use Sikaflex, you will just substitute the Sikaflex material for the washers. Anyplace where you don't have spacers now, the extra 1/8" will get blended with your skirt.
On the sides, the 1/8"--3/16" wider surface of the plexi on each side will just be faired with the skirts I think. You may have to make a custom molded-in-place skirt like the one pictured by Lionclaw to get a really nice look, but its not hard to do.
Over the front bow, you will position the windscreen with the same space for Sikaflex as the sliding canopy plexi, so the windscreen and sliding canopy will fair tangent.

The holes you have drilled will come in pretty handy for doing the Sikaflex. Use screws and just tighten enough to pull into position (don't let the plexi scallop or get wavy) until the initial application of Sikaflex cures, then remove them at the same time you remove the rubber hose spacers, then apply the final fillet of Sikaflex. tape the holes in the plexi so you don't get squeeze-out bulging out. Then, these holes will be covered by the skirt. Over the front bow, you may have to do some creative and careful epoxy + microballoons to fill the holes, then when you paint, you can put a stripe over that part of the canopy along the front bow. It will disappear under the fiberglass gap seal when the canopy is closed.

For a good tip for using Sikaflex on the skirt, see my old post using 30# fishing line to force a .030 gap between the skirt and plexi for the Sikaflex.
 
I reused my old side skirts.

IowaRV9Dreamer said:
Hi Joe - I'm with you so far on the Sika route. Did you do metal rear skirt or fiberglass? I assume you Sika the side & rear skirts on too?
Click to expand...

I reused my old side skirts, so they have the screws going into the plexi. :(

I did lay up a beautiful rear skirt, directly onto the fuselage with the canopy in place. It sanded and trimmed very very nicely. A perfect fit when closed. I even molded in the little "dog box" at the top where the slider rail passes through.

I get a lot of compliments on my rear skirt.

The windscreen was all sikaflex, no screws at all. We even removed the aluminum "hold down" clips before fairing in the transition with fiberglass.
We used duct tape to hold the windscreen in position as the sikaflex was setting, along with a couple of ratchet straps around the fuselage to get the flex "just right".

Once that sika has set, it's not going to let go, IMHO. I think the plexi will fail first. One benefit was that my windscreen to canopy transition was PERFECT, no gap or vertical unevenness. When we laid up the strip to cover it, it sealed very nicely.

Finally, I had the painter do the center strip on the canopy to cover the sikaflex and about 1/2 inch on the forward edge to cover the sika there.

Cheers.
 
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