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Old 12-18-2018, 03:00 PM   #21 (permalink)
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Current Detailed Plan:

Step 1: Roof Chop (Maybe)
Add a temporary third brake light to the rear doors. Cut out the Suburban roof from the back just above the doors weatherstripping and then 30” forward, stopping inside the window framing. Fabricate a patch panel using the roof of the parts truck and/or sheet metal tapered on an English wheel. Also fabricate a tapering Z patch for the sides near the windows, probably with a brake and bead roller. Weld all the items together onto the roof. Overhang the roof slightly over the doors to shed most water off past the weather-stripping. Cut off the upper portion of the doors, stopping at the weather-stripping. Put a cap/patch on the top of the doors to keep them sealed as needed.

Step 2: Fixed Tail
Relocate the rear tail lights to the bumper/other location. Beef up the tail light area to accept a heavy duty hinge. Create templates of the shape of the rear taper near the front and back of the tail. Bend aluminum tube (1.5”?) using a tubing roller/bender to match the templated shape. Cut/bend extension pieces to run between the two and weld the assembly together. Hinge the assembly off the tail light area on the passenger side, add a latch on the drivers side, and add areas to mount hinges for step 3. Using 0.040/18ga aluminum, create contoured panels to skin the frame and to transition from the frame to the Suburban body. Some mockup and field fit will be required. Weld the panels to the frame.

Step 3: Hinged Tail
Similar to step 2, create templates and build three frames one for each side and one for the top. (I am not sure about doing one for the bottom, I kind of liked leaving the bumper exposed from a “bumping” standpoint.) Hinge the three frames from the fixed frame, with the hinges for the top rearmost and the hinges for the sides closer to the vehicle. Offsetting the hinge pivots back slightly should allow clearance between the panels so they can shut without binding. Connect the frames to one or more electric linear actuators.

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Old 12-18-2018, 03:41 PM   #22 (permalink)
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If you look at the picture in Permalink #18, the pivot point is inset from the deployed position. You can't avoid a small inset, but more might be better to position the panel. The downside is the stored position isn't as compact.

On the aluminum frame, consider two hinges; one would have to resist torquing. Have you dimensioned the panels? The top panel looks long to store correctly.
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Old 12-19-2018, 08:48 AM   #23 (permalink)
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I couldn’t agree more about avoiding the roof chop. Waaay too much work for too little return.

And (the clincher), what degrades utility means it’s the wrong vehicle in the first place.



A folding boat-tail (big truck Trailer Tail-brand ) has been in a few of my daydreams for my CTD Dodge. Front air dam and side skirts of appropriate conveyor belting. Same to fill wheelwell gaps and cab to bed topper.

But all of it easy enough to remove pending sale (which should always help drive ownership duties).

Beginning, middle & end.

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Old 12-19-2018, 09:08 AM   #24 (permalink)
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I always wondered how Aztek Cd compared to otherwise similar minivans.
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Old 12-19-2018, 09:57 AM   #25 (permalink)
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Freebeard,
I see what you mean on the inset. Because the panels are curved at the mating surfaces, I will have to use inset and/or backset to make them clear without binding, however inset or backset reduce the effective length of the panel when constrained to nesting within the fixed space so I will try to minimize it. I will be sure all hinges are used in pairs. The folding panels are about 3’ for the top and 2’-6” for the sides. Attached are some accurately dimensioned drawings, a top view and side view, each square represents 3”.

Kach22i/Slowmover,
I examined the bodywork much more closely and based on your inputs I am abandoning the roof chop. There is some slight taper built into the top of the roof, but it gets too steep near the back. I will make the fixed tail meet the top right where the slope gets too steep. Thus step 1 is gone, other than the relocating the third brake light and patching that hole in the roof.

Everyone,
The taper shown in the drawings is based loosely on AST-II (side) and AST (top) rates of change, but are predicated on the assumed length that you are picking up from the existing slopes of the rear of the body. I need to more accurately compare the angles to see exactly where I am starting. I am also looking for more aggressive side tapers, I have a big collection of pictures and posts from Aerohead that I will do some overlays on. The feedback has been great!
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Old 12-19-2018, 10:11 AM   #26 (permalink)
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Quote:
Originally Posted by slowmover View Post
I couldn’t agree more about avoiding the roof chop. Waaay too much work for too little return.

And (the clincher), what degrades utility means it’s the wrong vehicle in the first place.
I think the worst thing would be the vortices forming at those wing root stubs left over.

They look like little car fins or vortex generators.
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Old 12-19-2018, 11:16 AM   #27 (permalink)
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side taper

Quote:
Originally Posted by aardvarcus View Post
Freebeard,
I see what you mean on the inset. Because the panels are curved at the mating surfaces, I will have to use inset and/or backset to make them clear without binding, however inset or backset reduce the effective length of the panel when constrained to nesting within the fixed space so I will try to minimize it. I will be sure all hinges are used in pairs. The folding panels are about 3’ for the top and 2’-6” for the sides. Attached are some accurately dimensioned drawings, a top view and side view, each square represents 3”.

Kach22i/Slowmover,
I examined the bodywork much more closely and based on your inputs I am abandoning the roof chop. There is some slight taper built into the top of the roof, but it gets too steep near the back. I will make the fixed tail meet the top right where the slope gets too steep. Thus step 1 is gone, other than the relocating the third brake light and patching that hole in the roof.

Everyone,
The taper shown in the drawings is based loosely on AST-II (side) and AST (top) rates of change, but are predicated on the assumed length that you are picking up from the existing slopes of the rear of the body. I need to more accurately compare the angles to see exactly where I am starting. I am also looking for more aggressive side tapers, I have a big collection of pictures and posts from Aerohead that I will do some overlays on. The feedback has been great!
I'd recommend figuring out where any plan-taper begins on the sides,then respect the taper contour based upon the template,or you're guaranteed separation if you get too radical.
The flow attachment on the aft-body can only tolerate a pressure recovery of that of a 4:1 streamline body of revolution's.
You can be more 'gentle', but you can't be more aggressive.
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Old 12-20-2018, 01:06 PM   #28 (permalink)
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Attached are my AST-II side view and AST top view overlays. I also did a few other top view overlays, but AST was the fastest “proven” design, other than Meir which basically was matching but got more aggressive past 40% (which I am not going that far back). I believe I have these drawings lined up accurately based on the existing taper of the vehicle. I also did a sketch of the bodywork viewed from the back, the boat tail will start at the base of the existing tail lights.
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Old 12-20-2018, 05:33 PM   #29 (permalink)
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That's what it needs.
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Old 12-30-2018, 10:13 AM   #30 (permalink)
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I assisted my step father in restoration of several 67-72 Chevrolet and GMC trucks in the mid 2000s. On one of those, a "Camper Special" we cut the roof off of an old Uhaul Dually which had clearance lights and corresponding raised buckets to replace the rotted roof panels on the 3/4 ton.

Despite measuring 5 times and using oem pieces, this was a painstaking undertaking.

Since you are removing your factory tail lamps, you will have to build filler panels. This makes me wonder if you would be better off pie cutting the length of your chop through this section of the body. This would leave your roof and windows in tact. You would end up with misaligned door hinges and a gasket that would need attention, but that seems to be much less work that what you have been describing.

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