What is the basic sequence of slider frame bending???

I've been staring at my slider frame for 3 days now - afraid to start bending it. I thought I might get lucky and it would be OK out of the box, but now it looks like it will need some "tweakage".

The instructions are confusing, and there are so many posts that I am overwhelmed... Here is what I think they want me to do. I'm not sure I have the order correct and could use some advice about that.

1) bend the square tubing at the base of the frame to be parallel to (and 1/16" inside of) the outside of the fuselage skin.

2) Cut the bottom of the front bow to get the correct 3/8" height relative to the roll bar.

3) Adjust the rear slider track so the height of the rear bow is 1/16" below the aft skin.

4) Bend the front bow to follow the shape of the roll bar, maintaining the 3/8" protrusion beyond the roll bar.

5) Bend the rear bow to follow the shape of the aft skin, maintaining the 1/16" height below the aft skin

6) At this point, the 3 rails can be attached to the fuselage (2 holes each) - and the frame will slide nicely.

7) Now squeeze the canopy frame closed about 1/2" (measured front and back) to compensate for the fact that the plexi will pull it back out to the original dimension. As soon as this squeeze happens, there will be no more sliding until the plexi is attached.

Is this pretty much the plan here?

Is there any way I can attach the rails to the fuselage (with only 2 holes each) earlier in the sequence?

As of right now, it looks like I need a small tweak on the aft rear square tube on the right side.

The front bow looks close to dead on, once the height is corrected.

The rear bow is the problem area - it looks like the right side is 1/4" or more lower than the aft skin. Left side looks good.

I'm planning on gluing the canopy if that matters to anyones suggestions.

Thanks so much for any help you can offer me.

Van's FAQ

Scott McDaniels wrote a piece in the RVator that you can find in the FAQ section of Van's site that is really helpful "Sliding Canopy Installation".
I found it useful to just install the slider side rails with a couple of holes and not lock it in until the end.
Bill Brooks
Ottawa, Canada
RV-6A finishing kit

Dave-

I have two comments. Step #1 and #7 are at odds with each other. It is very difficult to bend the frame. I spent a bunch of time getting the 1/16" clearance perfect. However, once I put the canopy on the spread made everything terrible. Seems to me it would be easier to just start with canopy spread value you have in step #7. Then you don't have to bend it twice.

My second comment is, the slider frame is not easy to bend. It takes lots of force. I used a couple of 4x4 blocks and jumped on the rails. Good Luck!

thanks Peter - I guess the conflict between 1 and 7 is my big sticking point now. Maybe I'll get the shape of the slider rails correct in step #1 and then set the width of the slider rails in step #7.

Also the instructions mention keeping the rollers centered in the tracks.. but that seems pretty crazy since the rollers and almost the same width as the tracks. There is maybe 1/16" of excess space and I cannot imagine holding half that tolerance across this big floppy thing.

Same confusion...

I have the same confusion as Dave. I've been stuck for a couple months out of fear of messing things up. I think I've got some of the bends correct but the width of my tracks is 41 3/16" versus Van's plans nominal value of 40 13/16". My fuselage width is 42 3/4" at the roll bar and 41" where the aft top skin meets the longerons. What kinds of measurements do you all have?

Here's how I did it...

I am building an RV-6, but I don't think the frame is any different. I have the square side tubes like in Pete's photo. I wasn't concerned so much with the dimensions as I was to make sure that the frame sat inside the fuselage skin as noted on the plans and in Scott McDaniels' article in the FAQ's on Van's website.

This photo shows my first attempt at bending the bow. It would have worked except that I did not use a long board across the inside of the bow, which would distribute the bending force. Rather, the force was applied to the inside face of the bow and put a small crimp in it.


This shows how I bent the majority of the bows.


Toward the end of the process, we reverted to brute force.


I put together a photo essay at: http://picasaweb.google.com/bakerfamilyenator/SlidingCanopyFrameBending#
Hopefully some of the photos and info will help someone!

Read this a couple of times before bending,.....

This is an article from Vans that you should read a couple of times and then think about a little bit.

http://www.vansaircraft.com/pdf/canopy.pdf

Just from experience, remember that the rear bows can be bent in seveal directions to change the dimensions. It's all trial and error and a lot of error :-( just bend a little at a time and don't bend anything once you start drilling holes.

Good luck, it's a rite of passage Everything looks easier after you've fitted the canopy!

Bill S
7a almost there

The aft bow on my frame was visibly asymmetrical right out of the box. So much so that if I were doing it again I'd consider requesting a replacement. But what did I know?

As others have pointed out, any area that you bend winds up affecting something else. I spent over 20 hours attempting merely to get the aft bow to follow the curve of the fuselage, indented by the recommended 1/16". Never really did get it right. Then a couple of friends stopped by, both are builders but neither had encountered the canopy frame before. We got the entire thing nearly perfect in 45 minutes. We worked on a building table. I bandsaw-cut some curved sections out of some pieces of 2x4 I had lying around, to serve as bending guides. I drilled through the blocks and the table and used some long bolts to fasten them loosely to the table top. Then using a combination of the blocks, some big clamps, musclepower and choice words, we worked the thing until it fit.

I used Sikaflex to bond my canopy in place, which covers a world of little fitment ills, but the frame was accurate enough when we were finished that it would have worked fine using rivets and screws without resorting to shimming.

Now that I am almost done with my canopy, I sort of know what is supposed to be done. I was fortunate in that the side bows were spot on, but unfortunate in that the left one angled up, so it was high at the aft end. I ended up cutting the aft bows off in order to bend those parts to the right shape, and I had to add a bit more length to force the lower left aft corner down so the guide pins would align properly. Of course, all the cutting and bending ruined the power coating, so when I had the fit correct, I stripped the coating off and spray painted the frame to match the rest of the cockpit interior.

Don't cut the front down to that recommended 3/8" until after you have fit the wind shield and drilled/finished the leading edge of the canopy plexi. Make sure the edges of the two properly butt up together before making the cut.

And don't final drill the slider rails until you absolutly have to. Getting the side skirts to align with the fuse skins is critical, and you can made some minor adjustments of the rails after you have done the final fitting of the skirts. Bending to bows to get the side skirts just perfect is not an easy task.

Once you have done it, you will find it really wasn't all that bad. Well......yeah, it was, or is, as I am not done yet. But, just go on and get started, as putting it off won't make it any easier.

right rear bow is 1/4" low

Thanks to all - this is great advice.

Gary - your photo album is great..... but it ends up with the square tubes of the canopy matching the shape of the fuselage. Well, I'm there now (got there a worse way)... but it looks like I will be having some problems with the round tubes.

As of right now, my canopy square tubes (I'll call them "rails") match the fuselage perfectly. They are about 1/4" too narrow , but of course the plexi will change all that so I guess I'm not going to worry about that now.

The front round tube (I'll call it a "bow") seems to follow the shape of the rollbar. It is much taller, but that is because I haven't cut it yet and won't based on advice in this thread. Here is a pic of the front bow, I'm happy with it:


The problem is the right rear round tube (aka bow). I think it may be the same asymmetrical problem that Lars described. Here is a picture - see how the left side of the picture (right rear bow) is lower than the other side?


Here is a close-up of the left rear bow as it leaves the center tube. See how it is the recommended 1/16" below the skin:


Now here is the right rear bow as it leaves the center tube. It starts out at least 1/8" lower and keeps dropping a bit as it goes. Keep in mind in this picture the ruler is like only 1-2" from the ruler in the previous pic.


I don't have any idea how to bend this without messing something else up. It seems as if the right rear bow is just attached a bit low to the center tube... and no amount of bending will change that. Can I compensate for this in the plexi attach? I'm going to use Sika so I could have a thicker bond on that side?

I think it is actually somewhat worse than is shown in the pics.. maybe up to 1/4" low as it moves away from the center.

Bending the aft bow

Dave, my canopy frame looked a lot like yours.

As I mentioned in my previous post, I spent endless frustrating hours trying to straighten the aft bow. I'd get one side to fit ok, but then the right and left square tubes would go out of parallel, viewed horizontally. Get them right, now the aft bow was messed up again. Eventually I cracked the right side of the aft bow at the junction of the top bow & aft mount. Fortunately I've welded lots of 4130, so repairing it wasn't a big deal, but it shook my confidence about ever getting the thing straight.

Eventually my hangar partner got involved. Helps that he was a professional land surveyor for many years. He helped me make a few measurements. It was obvious even to me that the arc of the left (pilot's) side of the aft bow was a lot flatter than the right. What I didn't notice before was that the center (top) bow was somewhat twisted. Its arc should be in a vertical plane, but it wasn't. Not only that, but the forward bow wasn't quite symmetrical either, though that was less of an issue.

A couple of pix below show the bending setup I referred to previously. I wish I had photos of the 3 man bending party that eventually got it right using that fixturing, but we were on a roll that day. I advise having a stout, heavy table and some big clamps handy, and get help: we managed to clamp and support the frame such that we could bend the top bow into perfect alignment- I'd have never managed that alone.

rear bolt

Oh yeah, one more thing... I r&r'd the frame a bazillion times while fitting it. Eventually I got tired of the tight-fitting bolt that retains the frame to the plastic slider block. I found a spare bolt and ground it down a bit so it slid in easy. A piece of welding rod or any number of other things would've worked as well, but we have piles o' old fasteners. Anyway, it made the process just a little easier.

And don't look too closely at those photos- our work area is definitely not OSHA approved!

bend side bows to untwist top bow?

Lars said:

What I didn't notice before was that the center (top) bow was somewhat twisted. Its arc should be in a vertical plane, but it wasn't.

Click to expand...

Lars - I didn't notice this, but I think you are right... It looks like the center (top, thicker round) bow is a bit twisted.. causing the smaller round rear side bows to be asymmetrical.

Lars said:

we managed to clamp and support the frame such that we could bend the top bow into perfect alignment- I'd have never managed that alone.

Click to expand...

In the pictures it looks like you are bending the smaller round rear side bows. Was the idea to bend those bows in an attempt to untwist the bigger round top center bow?

I can probably get some help, but I don't have any idea what to do here. Your pictures help a lot, though.

IowaRV9Dreamer said:

Lars - I didn't notice this, but I think you are right... It looks like the center (top, thicker round) bow is a bit twisted.. causing the smaller round rear side bows to be asymmetrical.

In the pictures it looks like you are bending the smaller round rear side bows. Was the idea to bend those bows in an attempt to untwist the bigger round top center bow?

I can probably get some help, but I don't have any idea what to do here. Your pictures help a lot, though.

Click to expand...

Unfortunately that was a period of builder frustration and so I didn't take many illustrative photos. It was head-scratching of the collective that got the ideas flowing the day we got it done. It's amazing when you have three guys and a bunch of clamps- you see ways to do things that don't occur to you when you are alone, simply because there's no way to do them alone.

In the case of the top bow, my recollection is that we clamped it solidly to the table- in fact I think we straddled it in a couple of places with notched 2x4s and then lag-bolted the 2x4s to the table so it was really solid. Then we torqued on the front and aft bows until they were perpendicular to the top bow. It still wasn't easy. That tubing springs back, a lot, so it takes a few tries. And the aft bow, being smaller tube, wanted to bend rather than twisting the top bow. Back there, we had to live with what we got. It wasn't quite perfect, but a lot better than when we started.

Are the heights of your...

canopy side bows equal, Dave? Looking at your first photo from the nose, it looks like the center bow is offset from your canopy front support. Is it possible that one side is higher than the other?

I did not have any problem with my aft tubes. Any problems that I had were corrected with bending the square tubes. The way I looked at my frame was that most or all of the bending of the frame would be taken care by bending the square tubes. The aft round tubes are much smaller/thinner, so it would be difficult to effect much change by bending these tubes alone.

As my friends and I looked at the problem, and it's been said many times before, every movement will cause some other movement. So we needed to clamp every other area in place, so that there was no movement except where we wanted it.

Let us know how you work thru it. Good Luck!!

Gary Baker said:

canopy side bows equal, Dave? Looking at your first photo from the nose, it looks like the center bow is offset from your canopy front support. Is it possible that one side is higher than the other?

I did not have any problem with my aft tubes. Any problems that I had were corrected with bending the square tubes. The way I looked at my frame was that most or all of the bending of the frame would be taken care by bending the square tubes. The aft round tubes are much smaller/thinner, so it would be difficult to effect much change by bending these tubes alone.

As my friends and I looked at the problem, and it's been said many times before, every movement will cause some other movement. So we needed to clamp every other area in place, so that there was no movement except where we wanted it.

Let us know how you work thru it. Good Luck!!

Click to expand...

And therein lies the problem: these things are inconsistent.

A friend is building a -6 and has one of the old style frames with side bows made from round tubing. It looks beautifully symmetrical, everywhere, and he hasn't touched it.

I got my frame 2 years ago with the finish kit. The side bows were nearly perfect when looking straight down (arcs followed arc of fuselage). The front bow nossamuch, but still not too bad (slight asymmetry, easily corrected by grunting loudly while bending). The top bow was out of plane (twisted). The aft bow looked like someone really wasn't paying attention when the frame was jigged/welded- like someone sat on it and pushed it to one side. The left side was so much different from the right that it was easily visible, and it caused the side bows to be out of parallel when looking across the fuselage. From seeing Dave's photos, it appears that his was similar to mine, possibly worse.

Canopy Bending Link

Here is a link to one site I found a while ago when contemplating how to redo my slider. I bent the first one so many times it finally cracked, etc. The canopy by far for me has been the most frustrating part of the whole build! Anyway, I hope to employ some of these techniques and ideas when I begin to tackle mine again this summer...

http://www.vx-aviation.com/rv-9a/photos/Fuselage/Canopy_photos.html

Doug Lomheim
9A; 90116;
Mazda 13B FWF / electrical

If I had my druthers I'd ask for a raw materials kit and weld the thing up myself. As much time as I spent bending mine, it would've been faster just to start from scratch. Fortunately I have the pink cowling to keep me busy now. After the canopy, it seems easy