Slider Blues ? Seeking Opinion on Options

JVolkober · #1 11-24-2009, 09:40 PM

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.

JoeBlank · #2 11-24-2009, 10:11 PM

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....

petehowell · #3 11-24-2009, 10:26 PM

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........

Steve Barnes · #4 11-24-2009, 11:01 PM

Check your PM

Bob Axsom · #5 11-25-2009, 01:14 AM

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

Chappyd · #6 11-25-2009, 03:30 AM

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?

newtech · #7 11-25-2009, 05:59 AM

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.

David-aviator · #8 11-25-2009, 06:58 AM

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!!

JVolkober · #9 12-05-2009, 12:13 PM

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.

Sully · #10 12-06-2009, 09:32 PM

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

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.