mark kibort

I started to dig into my sunroof this weekend and found, by careful observation, that i believe you can get most all of the suroof weight out of the roof by cutting it all out . Not just the metal sheet that looks like the second layer where the actual sunroof slides in and out of, but the structure that attaches to the sides and inside of the roof. (The liner, if you will, around the front of the sunroof opening.)

you can see by my pictures below, that i just followed the "gutter" path with a sawsal. (starting from the inside outward until I hit this path of sheet metal.)
Then, by pulling it down (bending , because Im not finished with the other side yet) you can see the structure. its not really even attached at the rear, just in the middle with those 3 fat welds, but also a vertical piece that you can see.

If you take a sawsall now and hold it horizontal and attak the sunroof structure, you will end up with just a lip, all the way to the rear of the car. the rear can and has been cut out to mirror what the stock non-sunroof roof looks like.

Then, the only thing remains is the front structure. instead of using a sawsal, you will have to use a grinding and cut just the front of the sunroof structure this way. after that, there will be nothing left, but a thin ridge or portion hanging down all the way from the rear, to the front, and back around to the rear again. Nothing else will be left. underneath, the roof looks identical to the non sunroof roof.

after this, a piece of the donor roof or CF, something, can be bolted in place using the what is left of sunroof structure. (Ill probably leave 2 tabs, front and rear for this purpose incase I want to bolt in and make brakets for a sunroof cover. I could make the cover out of the donor non sunroof top and make it a little wider.I could cut the piece out, leaving tabs front and back to bend downward to be used for L bracket tabs.

thoughts?

This certainly will be much easier than removal of the entire roof, windshield for prep and rear hatch. plus, we need to do it twice becasue I have to remove the donor roof from its structure as well.

Mk

mark kibort

I had to finish the gutting of the sunroof. I just couldnt let that thing beat me!
so, after 4 jigsaw blades, and each one broken and reground to be used again , I was able to get the interior roof sunroof panel.

Get this, the panel only weighs exactly 5lbs. then, I noticed that the sunroof box is actually not really attached that securely. so, with some plyers, I was able to break the rear part of the sunroof box and get half of it out. by the way, all the rear section weighs is a little under 1lb. Im sure the front part will be more like 2.

I think now, its find a way to cover the sunroof hole, or replace the entire roof. right now, there is no weight savings either way.

What would you do?

here are some pics of the panel that was removed. its the same size as the sunroof hole and , again, only 5lbs. bet the sunroof is near 13lbs.
Also, a few shots of the sunroof box being pulled apart and what is left is the front area. grinding wheel and sawsal will drop that structure. its glued in, and it wont come out without bending the roof. (tough stuff) . so we will cut it out and leave some tabs to mount a roof panel as a bolt in sunroof cover. any ideas?

jon928se

Fully caged race car - 1.5mm or 2mm aly panel. Joggle the existing edges to get a flush outer surface. JB weld in the new panel. Bondo smooth and repaint.

mark kibort

I just weighed the sunroof itself. (with all the stuff taken off of it) 14lbs so, the entire structure of the sunroof, including the sunroof is worth about 22lbs. (not counting all the motors, brackets, interior panel, etc) Thats the sunroof, the steel that you can see and cut out and all the structure attached to the roof to support it. 22lbs. minus, what ever a panel will cost to add. probably 2-3 lbs I would guess. so net, 20lbs

sunroof itself = 14lbs
interior roof panel holding the sunroof rails =5lbs
side structure = 1 lb
front structure = 3lbs (est).
_________________
24lbs

There is all the stuff you pull out when removing the sunroof. cables, motor, brackets, tracks , and ceiling stuff, that probably weighs 5-10lbs but I didnt weigh it.

James Bailey

Sounds about right 20 lbs off the highest point of the car.....far far better than say 20 lbs for an alloy torque tube Just please be sure to cover the exposed cut edges they are dangerous should your arms be flailing about during an Oh **** moment.

FUSE69

You've done pretty much the same as me.

I made a CF plug to fill the hole and I also welded in a tube to add back some reinforcement to the rear header also to help reinforce the hatch hinge points....





0.769Kg

svp928

Is that scale in grams? 769gm = 1.6 lb, so a nice light panel. You should sell those!

mark kibort

HOW CAN I GET ONE OF THOSE!!!!!!! That looks great. the only thing that I would do, is finish the cutting up front. there is a couple of lbs there, so that I could equal your weight savings, by using a 3lb sheet of the non-sunroof roof, and bolting it in place. (or close. ) you dont need the structure behind where you bolted the CF roof too,and up front there is a lot of wasted steel remaining from the sunroof structure up front. very clean . can you make one for me??????

I dont know if the bar you put in is nesessary for the hatch hinge. you end up with pretty much what a non sunroof top has back there as far as support. Looks like a clean install though!

mk

FUSE69

Yes, scale is grams. I was pretty happy with the results...
As for selling... there's really not a business case, given the time involved and the cost of raw materials here in Sweden... 'Constantine' made something very similar some years back... I believe he sold those for 100USD??
Raw materials would cost that much here in Sweden.

Perhaps could have gotten away without the tube... but the section size of that rear header is smaller than a non sunroof...



Perhaps not enough smaller to worry about, but at the time I did this I felt it was better to be safe than sorry.
If I had a roll cage I would not have put the tube in, but would probably consider 'gusseting' the rear header to the main hoop... if possible...
I did do a little more trimming after the pics were taken, just never took any new pics.... I fitted a non sunroof headliner and found that there had to be more removed for it to fit. (At the moment this car is predominantly a street car)

As for making more... the mold/plug... whatever you want to call it is at work... I'll have a look at it tomorrow and see if its in good enough condition to produce another... I probably have enough material laying around to make another...
I'll get back to you.

dr bob

Mark, you will almost undoubtedly want a similar rib across the rear of the opening to keep the back half of the roof from flapping.

My thinking was that the spot-welds would get cut and the original adhesive cut to get the roof section off. The donor panel would then get spot- or maybe stitch-welded into place on the race tub.

If you are serious about saving weight up top, think about a CF rear hatch with a lightweight polycarbonate rear window. Put latches on and no hinges, just lift it off to get best access. Bet that rear hatch and glass weigh a LOT more than the roof panel.

mark kibort

back half of the roof from flapping?? how. it is very very sturdy back there and has similar reinforcement to the stock non sunroof top. there are no welds that have been removed. look at the pics again. what is left is very much like stock non sunroof roof

as far as the rear window, heck, that has been lexan for 10 years. . I forgot its weight, but the glass was really heavy. I even cut out some of the sheet metal out at the hinge area. its not as stable, but fine for my use as a street race car.

sure, a race hatch made of CF would be light, but the car is really light enough. the latch works well and I use the rear hatch to hurry up and set up cameras, turn them on before race time (5min drill) and get in the car and get buckled in. the stock stuff back there is working well, but also I havent seen a replacement hatch as of yet.

dr bob

Easter Bunny just hopped by. And I thought there was no such thing. Another myth debunked.

mark kibort

Look, if I wanted the lightest and most powerful race car, (that was also reasonalbly cheap) I would bolt a blower on to a S2000.
You can build your race car anyway you want, but I race a 928 for a few reasons, feel, looks, sound , power and MOST importantly, safety. why in the heck would you want to put a CF roof on a car that has such great roof protection. I dont know about you , but if you rolled on you side and got hit on the roof by a competitor, I want to have most of the roof to be steel, not CF regardless of the 15lbs you might be able to save. oh, and by the way, add back in another roof bar to give you legal protection.... oh, now its a wash or only 7lb savings

The 928 is a 2600 to 2700lb race car no matter how you slice it. Sure, you can shave a few ounces here and there, and I do, but i try not to compromise safety too much. And, i try and do it in a way that gives the best bang for the buck. Again, if you want a really light and race car, grab a 911 and drop the car and $70k off to Jerry Woods. . You might end up with a car that is fast as a gutted 928 and some bolt ons.

Mk

IcemanG17

I would guess the pop riveted panel on the Estate is light...I think Clint said 2 lbs or so....

mark kibort

I bet more like 1lbs. heck the piece on the inside that is the width of the sunroof exactly, is 5lbs, the actual sunroof is 14lbs . the actual roof is only going to be 15lbs or less. (and all that support structure is less than 3lbs).

rivited aluminum is very light, but it looks like rivited aluminum. I want to make this car look kind of nice.

mk