Montage trunk lid redesign ideas

[Rick]

One of the ideas I have been thinking about for my Montage is to figure out how to make the back not a big one piece design and instead split it into fixed fenders and a smaller trunk lid. The reasoning is that there is a lot of wasted space in the trunk lid since the whole area in front and behind the wheels is mostly taken up with the latches and stuff. If the center area opened up like a normal trunk lid somehow, that would give a huge amount of extra working space in the car. It would even let me have a bit of room for a small storage space and maybe even a spare tire in the back. The main reason I am thinking of doing this is part of my eventual plan is to add an electric drive to the car and I need somewhere to fit 108V of batteries. With the large area in front and behind the back tires it would be real easy to find the room to mount them.

One thing that would make it a bit easier on my car at least is that I have the roll bar going right up against the trunk lid in the little back window so I could attach a hinge to that part easily and not have to worry about the trunk getting destroyed from not closing it properly and driving off. Cutting up the trunk lid would be a huge amount of work but in the long run it would probably be worth it. Anyone got any ideas?

[Sulley]

Hey Rick - I have a Manta Mirage so I'm not as familiar with the Montage layout. Also I think some have the VW power-plant and other a V6 or V8. Can you post some photos up of these areas as that would help me.

[Rick]

On the pictures you can see the area in front of and behind the wheels and suspension is more or less useless in the current design. For a race car that might be OK since they don't need the space. But since I am making it a good street capable car I want to find a way to use that extra space. All the area in the back where the body opens up is a nice large area that could be used as trunk space if the body was solid and just the lid opened up forward like a normal trunk lid.

Ideally I would really like to cut the top of the trunk off and make it hinge at the roll bar and have a normal trunk latch to open at the back. I just don't see a good place to make a cut to make that happen. It is pretty old fiberglass so if I cut it apart it would probably warp enough it would never fit together square again. I would also have to figure out how to fiberglass a lip on the fenders and back for the lid to close against and make it all strong enough to survive driving 20k miles a year.

[Blueovalz]

The flange is not a big deal to make. But the hard part you've got to decide on is hatch configuration, hinges, latches, support, etc. These fenders have a lot of area behind each wheel that could be sealed off from the rest of the body. Cutting out two hatches (one on each side of the back rear deck should provide some amount of storage without resorting to cutting the rear window bulge or roofline that extends all the way back. Guessing from the photos that would put you at perhaps 3 or 4 ft^3 per side (good for a helmet, some lunch, and an tech inspection form Anyway, once you decide the exact shape and size of the door (lid, hatch, whatever), then making the sealing flange is easy. You may also want to determine what the thickness of the material is back there before you start. If it's thin (1/8" or so in my humble opinion), then you'll need to build it up a bit so that when you start cutting, or install some boxing panels to beef all of this up so that the body holds its shape after being weakened with the cutting. inserting bulkheads or walls to seal these new storage boxes will provide a lot of new stiffness, but you'll still need to structurally tie the two together (perhaps with a single wall or panel of fiberglass connecting the two boxes.

[Rick]

What is the easiest way to attach things like latches and mounting points to the body? If I do open it up somehow I will need to mount it all together and drilling through the outside of it would look really terrible. So what is the easiest way to fiberglass in a capture nut or something that will hold up for years of use? My best guess would be to weld a nut onto a plate of metal maybe 1-2 inches square and fiberglass over the plate. I am not sure if there is something actually made for that purpose though. I know boats use wood but that would probably not work out that well in a car.

I am really thinking of just cutting the entire top part off at the corner lines like outlined and use a hinge setup similar to the old chevy style hood hinges that let the hood move forward and up to clear the back window and roll bar. That would let me get away with a simple trunk latch without a hood safety catch. But that would probably need a huge amount of reinforcing to make it all stay together and work.

Also there is one other really annoying thing with the way the small spoiler lip is made on the back of the car. When it rains it gets maybe a gallon or two of water built up on either side of the car sitting in that dip(look at that dirty area on the back of the trunk lid to see where it is). So if I drive away without clearing it and hit the brakes before it all runs off it all comes rushing up and probably half of it dumps in the windows. I would really love to figure something out to make that problem go away but I have no idea what to do about it. Other than not hit the brakes after it rains

[Andy Sheldon]

Rick

Could you post some pictures of your door hinges please?

Thanks

Andy

[Blueovalz]

A method I've used successfully without failure is Helicoils. For hinges and latches that must use a blind hole, I fabricate a piece of 1/2" or thicker fiberglass block or small plate just large enough to hold whatever it is I want to attach to it. Then I drill, tap, Helicoil the threads, then bond the piece onto the fiberglass panel, Caution! In doing this, you MUST use fasteners that are short enough not to bottom out. If they do bottom out before being tight against the attachment, they may pry the plate away from the fiberglass panel that the plate is bonded to.

Porsche used the hinge configuration you're interested in. They hinged the back of the 917(I believe?) at the top of the hatch to where it opened from the rear.

There are solutions to everything you're wanting to do, and most all of them will entail some degree of bodywork that will require redressing holes, gaps, etc.

[Rick]

I was thinking of welding a T nut http://www.grainger.com/product/T-Nut-1XGH7?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/1XGH1_AS01?$smthumb$ like this type onto a small 2 inch square of expanded metal for the high strength areas. That way the holes in the expanded metal would let the fiberglass hold it all together pretty solid. I have not really ever done much work with fiberglass other than the few things with this car. And this build of it is the first time I am really changing it from the way it came and redesigning parts of it. I will have to look around and see if I can find some information about the 917 hinge setup. If it would work out without major modifications that would be great.

The bodywork on this car is pretty crooked right now, I think there are maybe 6 bolts still left holding the top body to the side pods and it is sitting on the frame with 4 bolts attaching the side pods to the frame. So I figure there is probably a month worth of work making body bracing and getting the panels aligned and looking good again once I get the frame finished. I will have to remember the helicoil idea. I have tried to screw stuff to the fiberglass before and it never would hold for long. Do you put threadlocker or epoxy or anything on the outside of the helicoil before you thread it into the block of fiberglass?

[Manta22]

Rick

Make sure the expanded metal is clean so the glass will bond properly.

I like to use Riv-Nuts for attaching things. Normally they are used for blind applications where you can't get to the backside of the material but they are also useful for forming threaded inserts in fiberglass, etc. A little JB Weld epoxy helps keep them from turning in the hole.

[Blueovalz]

I've used Riv-nuts in fiberglass for the smaller threads (size 8 and 10), but going up from there caused me concern about the strength of the panel for tear-out. Oh, and no, HeliCoils don't require any threadlock.