Archive for April, 2012

Mostly Canopy Stuff – 4 hrs

April 28, 2012 Leave a comment

Saturday Apr 28, 2012

Today I completed a number of tasks leading up to the final alignment of the aft canopy frame to the roll bar and the forward canopy frame. I marked locations for and drilled holes for the C-613 splice plates that join the side rails to the canopy frame weldment. There is one hole in each plate that would be very close to  existing holes in the F-702 skin so I left out those holes. You can see that in the photo below.

I also made the C-731 lift handle which will mount to the left side of the canopy. I rounded the corners a bit to make it more sleek than the stock design.

Then I located and drilled the pilot holes in the WD-725 side rail weldments for the attachment to the bow frame.

I finally started mocking up the avionics layout on the instrument panel today. I started with the main instruments; a 10-inch Skyview PFD, a 7-inch Skyview backup display, a PS Engineering audio panel, SL-30 radio, and GTN-650 WASS GPS. That really starts to put some context to the cockpit.

Next I made one of the C-723 wedges. These things are a pain in my opinion. I messed up the first one when it go sucked down into disc sander which I was using to trim down the material from a 3/16 inch piece of stock. The piece is small and gets hot really fast so I had to keep dunking it in water to cool it off.

The second try turned out pretty well. You can see the wedge slipped in under the left edge of the splice plate in this view. I still need to finish the second one for the left side.

I also installed the three rivets in the F-712D elevator stop on the aft deck. I had a note to myself to finish that since the day I removed the vertical stabilizer.

So work this weekend was somewhat productive but intentionally a little slow and non-committal on the aft canopy frame alignment. I have been making the parts I will need but not drilling things together. That is because I have been researching the options on mounting the canopy. Basically the decision is to screw or bond the canopy to the frame. Screwing is the Vans standard method but I don’t like the increased risk of cracking the canopy with all those holes and stress points. I also like the clean look of the Sika Flex approach along the bow frame son I am leaning that way but as yet not committed. Each approach has implications on the alignment of the frame components.

My options are:

1) Screw the plexiglass canopy on according to the standard method. This approach requires no modifications for mounting – just follow the plans.

2) Use Sika Flex to bond the canopy to the bow frame and front deck but use screws on the side rails. This will require modifications to the bow frame to allow 1/8 inch minimum bond gap.

3) Use Sika Flex to bond the canopy to the bow frame,  front deck, and side rails. This method requires modifications to the bow frame and the side rails to allow 1/8 inch minimum bond gap.

Some builders ignore the 1/8 inch bond gap recommended by Sika when attaching to the side rails but I am not sure that is a good idea. The joint in question is shown on this view for the standard mounting. The option 3 modification would be to offset the side rails inboard by 1/8 inch to provide space between the rail and the inside surface of the canopy where the Sika bond will go in place of screws.


C-704 Splice Plate – 1.5 hrs

April 24, 2012 Leave a comment

Tuesday Apr 24, 2012

I had a productive time on the project tonight, especially for a work night. I marked out the locations for the holes in the C-704 splice plate and drilled them. Then I aligned the splice plate to one of the F-631A channels and drilled the mating holes to lock in the position. Then I took a scrap of .062 aluminum sheet and made a dummy splice plate (without the flange) and match drilled it to the C-704.

That gave me a matching plate that I could cleco to the front side of the F-631A channel and use it to transfer the hole pattern of the C-704 to the other F-631A while installed on the fuselage. Then I prepared the second F-631A by adjusting the outer flange angle and fluting to straighten. Glad that is done. My hand is sore from fluting that thick material. Then I aligned both F-631A channels on the roll bar and clecoed on the dummy splice plate. That does not sound like much but it is good progress for a Tuesday.

Started Aft Canopy Frame – 5 hrs

April 22, 2012 Leave a comment

Sunday Apr 22, 2012

A constant theme I read in other blogs about the canopy frame is that it moves around and never fits the same way twice. I can corroborate that opinion. Every thing you do to it makes is shift a little and the fit to the fuselage changes – at least at this stage of the build. I spent at least three hours today tweaking the fit by slightly bending the frame; either the aft tube or the front channels. It is surprising but you can bend the front channels even though they are pretty thick. The material is softer than I expected. After a whiel it just became too frustrating so I switched over to working on the aft section of the canopy frame which is the rear arch and the side rails. First step was to make eight spacers, four 1/8 inch aluminum spacers and four 7/8 inch wood spacers. The aluminum spacers are just scraps of 1/8 inch stock. The 7/8 inch spacers are cut from a 2×4 a little thick with my mitre saw and sanded to final thickness. Here are two for example.

I taped the spacers to the inside of the F-631A channels and clamped them to the roll bar. After aligning them I marked the approximate locations for screws so I would know where I could put flutes. That is what you see set up here.

The plans say: “The F-631A ribs must have the flange angles re-adjusted to about 92.5 degrees (as formed they are only about 88 degrees) and then fluted to make them straight.” I looked at what other builders are doing and learned that they are only adjusting the outer flange angle; not the inner flanges. So that is what I did. It is a shame that the channels start out nice and flat then go pretzel on you when you adjust the flanges. Then you have to flute them like crazy to get them back flat again. Well finished one of the F-631A channels tonight.

Categories: Canopy Frame

Drilled Canopy Frame Hinge Holes – 6 hrs

April 21, 2012 1 comment

Saturday Apr 21, 2012

Oh canopy release mechanism, you have been more of a pain than I expected. I had to remake the links and now I learned that I should not have riveted the hat section to the subpanel until after installing the mechanism. Mounting it requires cutting a slot in the center rib for the link to pass through. There is not a dimension or note on the drawing telling me where to put said slot or how big to make it so I had to figure it out on the fly. First thing I did was mark the rib approximately where the center of the slot should be and I made a hole there just large enough for the link to pass through. That allowed me to place the bearing block where it needed to be and align it with the hat section with the links in line with the pin holes for the canopy hinges. Then I drilled through the #12 holes that mount the bearing block to the hat section.

The bigger challenge was installing the nut plates on the hat section. My options were to drill out all of the rivets that hold the hat section to the subpanel and install the nut plates conventionally, or use pop rivets to install the nut plates. I chose the pop rivet approach because I did not want to risk having oversize holes because universal head rivets are tough to drill out. But pop rivets are 1/8 inch versus the 3/32 holes in the nut plates so I had to enlarge those holes. I know that drilling out nut plates is difficult because the metal is very hard so I used a diamond bit on my dremel to enlarge the holes almost to 1/8 before final drilling with a #30 bit. That worked pretty well. Then I machine countersank the holes in the hat section and assembled it. Fortunately this assembly is not structurally critical so I am not worried about the pop rivets in the least. In hindsight I went back to my March 3rd post to warn other builders to hold off riveting the hat section.

With that done I was able to gradually begin enlarging the slot through the center rib to allow the mechanism to rotate through the entire range to disengage the canopy hinge pins. It turns out the slot is bigger than I expected. And I had to make a notch in the hat section to permit the clevis pin on the left to rotate by without contacting. You can see the pop rivets in this photo.

Then I put the subpanel back in the fuselage to check that it all works. I don’t have a handle attached yet but it does work if I rotate the bellcrank.

Next I turned my attention back to fitting the canopy frame. I worked for a long time to get the fit of the canopy frame skin to the fuselage as good as I could, then it came down to just drilling the holes for the hinge goosenecks. Other builders have documented the setup very well so I’ll just pick up where I was ready to drill. I used a 12 inch long 1/4 inch drill that I already had from a prior project. I unclecoed the F-771 skin on one side then drilled through the hinge bearing a shallow hole. It’s hard to tell how deep to drill because you can’t see it well. As it turns out I could have drilled a little deeper. When I took the frame off the fuselage I finished drilling the holes to 1/4 using a hardwood block as a drill guide. Here is one side drilled.

Then I enlarged the holes to 3/8 using a new drill bit and pressed the brass bushing in.

Here is a shot with the frame remounted on the fuselage to confirm that it works as a hinge. It does.

Riveted Canopy Frame – 3 hrs

April 18, 2012 Leave a comment

Wednesday Apr 18, 2012

In this episode I spent some more time trying to tweak the fit of the canopy frame on the forward fuselage. I must have put this thing on and taken it off two dozen times by now. Since yesterday I’ve just been playing around within the slop of the clecos and bending the aft tube slightly to try to get the edges parallel and flush to the side skins. Eventually I exhausted everything I could do and I can’t get it any better so I decided it is time to move on. So I started preparing the frame to be riveted together. The splice plate area is accessible so I scrubbed and cleaned the faying surfaces and spot primed them with SEM.

On the forward side of the frame I machine countersank the holes for AN426 flush rivets.

After this dried overnight I riveted the splice plate on.

And I riveted the ribs to the channel, again with flush rivets. This whole frame will get cleaned and primed later.

Remade C-621 and C-622 Links – 2 hrs

April 16, 2012 Leave a comment

Monday Apr 16, 2012

I was reading through another builders log last week and noticed he was remaking his C-621 and C-622 links because they were too short. His comment was he didn’t notice that the length dimension given on the drawing was from pin hole center to center, not the end to end dimension. I thought how glad I was I didn’t make that mistake, until I checked and sure enough I had done the same thing! Ouch. Both links are 1/2 inch too short. So I ordered two more tubes from Vans and tonight I remade the parts. Still a pain working with this 4130 steel. But if it is any consolation to me, the workmanship on the new ones is a little better than the old ones. This picture shows both sets, the old ones are primed, the new ones are bare 4130.

It was warm and dry tonight so I was able to clean an prime these parts with a can of SEM. Here is how they will be assembled.

I also removed the elevators tonight and put them back into storage. In doing so I took a picture of the trim tab clevis so I can reassemble it later with the same thread engagement to maintain the same trim tab alignment. This is so I can count the exposed threads.

I also took a photo of the little bracket that holds the trim cable under the cover. For the record, the nut was engaged 4 full turns. That is for my records also.

Canopy Hinge Pins – 0.5 hrs

April 15, 2012 Leave a comment

Sunday Apr 15, 2012

Today is tax day and I spent most of it work on my taxes, my daughter’s, and my Mom’s. I had only a half hour to cut and round the hinge pins for the canopy frame.