S

Steve Sampson

Well Known Member
Today I offered up the canopy frame to the fuselage and I am slightly perturbed by how much bending/hacking it will take to make it fit.

I have a few questions:

1) Much of the bending I need to do will be across a weld. Do I run a significant risk of the welds cracking/breaking? It appears quite a lot of force is needed to change anything much.

2) I have bent the rear bow to make it about .25" wider succesfully. I will need to split the central bulkhead , but the plans allow for that, to gain .25 there also. My concern is have many people had to cut the front bow? (I know Thomas in Germany did.)

3) Is this all normal?

I have put a few pictures here though looking at them I find a lot less daunting than going out in my workshop and looking at the problem for real!

A few words of wisdom and comfort at this stage would be most welcome!

Cheers!
 
Canopy frame

Steve,

With 20/20 hind sight now, I worked too hard on the front canopy bow. It is quite soft and bends pretty easily. Let me back up... Out of the crate the canopy bows matched very closely without any tweaking. The mating radii matched, angle fore and aft good. I decided to get greedy and slighly change the front bow radius and make it perfect. This set off a chain reaction of bending and tweaking that went on for several weeks while I was forming the three skins. I made a simple curved form from a scrap piece of medium density fiberboard. I put the form in a vise and then supported the other end of the canopy frame on some boxes. This allowed me to stand over top and gently put pressure on it. This was helpful to make very slight adjustments in the radius.

I think all the bending I did was overkill. The aluminum tubes used for the securing assembly helps you out on this. The plans call for a slight bevel on the tube ends. When the rods slide into the holes it draws down the canopy just enough to make the forward skins flush. This is the way it was designed. I would not go overboard.

I didn't break any welds. There wasn't a need to bend any of them.

This may sound sick but I sort of enjoyed building the canopy.

Sincerely

Brian Vickers
RV4 ? finishing, sort of? about to start the panel
 
Bend it

Steve,
I read your post again. Yes, I bent the bows to width. The bows are soft and therefore bend easily. The builder's manual says to bend them to fit.

Brian Vickers
 
Steve,

Relax my friend. I just got done with this part (I'm only about a week ahead of you!) and you can make it all work with some tweaking. One thing that helped me was the C-408 and C-409 rods that lock your canopy into position. As the manual says, drill these holes undersize (start with 3/8" inch) then grind them down to the 1/2" size required to get the bushings in. I used the hole shape to help tweak my frame into the proper position.

In other words, I bent my frame to as close as I could get it to the airframe. But after this, I still had about a 1/8 inch gap (as you look from the side) between the front bow and my "overhang" skin that comes off of the top of the instrument panel (the one where your front canopy skin rests on when it is closed. Like yours, mine sat just a tad low. Again, by sizing the 3/8" holes in the "right" direction, it now mates up perfectly. You can also locate the 3/8" hole in the side of your instrument panel (and your bulkhead in the back) to help position your frame when it is closed.

As far as your gap goes in the back of the frame I wouldn't think that would matter. As far as I know, there isn't a problem with having a gap of a quarter of an inch or so (maybe someone else will chime in here). Since your back seat frame will rest on the bulkhead frame I don't see what the problem would be.

Hope this helps - keep it at and one of us will be flying soon.
 
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Rick / Brian - thanks for the inputs. Have had to pull a sheet over it for a few days to take care of a decaying father. Back to it soon. Cheers, Steve.
 
I can't speak to a 4 but it took almost nothing for the weld on my 7A tip up frame to break. I'm headin gup to an aluminum welder today. It's not much of a structural weld on the aft tubes, it appears to be there just to hold it in place until things are fit and skins are riveted on.
 
No. The welds shouldn't break. I TIG weld aluminum all the time and been around machine shops all my life, the only welds that tend to break are the ones where the wrong rod was used or there was inadequate penetration or a bead that's not wide enough. FWIW I made the flop-over canopy frame from scratch on my F1, that's the only way to go if you want a perfect fit. Otherwise, make the square tube bends so that the tubes fit inside the instrument panel flange, and use structural adhesive such as DP190 or epoxy/flox to shim the front canopy skin. In a nutshell you strap the skin down after laying on the epoxy onto the square fwd. tube, and let it cure before drilling the skin on. Use packing tape on the skin so it doesn't stick. Afterwards you can sand the excess glue on the front tube, and rivet the skin on. Hope this helps.

Regards,
Bob Japundza
RV-6 flying 850 hrs. F1 under const.
 
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