Lighter weight 'convertible' targa top
- Thread starter X1/9Cruiser
- Start date
Henk Martens
True Classic
Ciao amici,
Great to hear about all your creativity.
I did this, cut out a piece of the original targa top and glued in a 4 mm leight weight but very strong tinted Lexan Panel
First we fitted a special laser cut metal frame inside the targa top as a base for the Lexan panel
saluti,
Henk Martens
Great to hear about all your creativity.
I did this, cut out a piece of the original targa top and glued in a 4 mm leight weight but very strong tinted Lexan Panel
First we fitted a special laser cut metal frame inside the targa top as a base for the Lexan panel
saluti,
Henk Martens
puntobarney
Low Mileage
cant find it in your catalogCiao amici,
Great to hear about all your creativity.
I did this, cut out a piece of the original targa top and glued in a 4 mm leight weight but very strong tinted Lexan Panel
First we fitted a special laser cut metal frame inside the targa top as a base for the Lexan panel
saluti,
Henk Martens
Mike Schofield
True Classic
I love that! Available??
Black-Tooth
Tony Natoli
As always, Henk... great work and good to hear from you.
Are you still selling these and if so, what is the price and could you estimate the cost to ship to CA and NY.
Thanks...
Are you still selling these and if so, what is the price and could you estimate the cost to ship to CA and NY.
Thanks...
Mike Schofield
True Classic
Heck ya!
Bjorn Nilson
True Classic
I did av variant of the canvas approach as I expect the canvas will slack over time so I made a carbon fiber skin instead.
I started with shaving off 1-1.5mm from the roof and lost 1.5kg. Then sanded and polished the roof. -Not need to be perfect if you do not bother about finish on inner roof when ready. After polishing I applied several layers of a release agent so the epoxy resin won't bond to the roof later.
Then applied 3 layers of resin and 2K carbon fiber on the roof. Using a putty shovel to spread the resin evenly worked better than using a brush. I was recommended to add a final layer of peel off weave as well. This should help flatting out and spread the epoxy resin. However, I found the peel off weave doing more bad than good. But not very hard to rip off.
The release agent worked very well so the skin was easy to remove from the roof.
Then it was time to remove most of the fiberglass. I just kept the frame and a thin cross for rigidity.
I epoxy glued the skin on to the frame and cut CF endings to fit the frame. Then sanded it and applied two more layers of resin (should not dry completely between layers). Finally wet sanded the roof and polished it.
I'm not 100% satisfied with the result. As you see there are some errors in the CF fabric, and also some smoky areas in the epoxy.
Therefore I didn't clear coat it as I may decide to paint it instead. Or maybe check paint it white/CF (Abarth style) to hide most of the bad areas. What do you think?
I applied three layers of CF but two layers would definitely had worked to obtain even lower weight without losing much rigidity.
The total weight is now just 5.4kg (12lb) so in total 9kg has been removed (incl insulation and inner roof).
Moving the roof in/out from frunk is so much easier now and that was the main reason for doing this. I am driving the car in dry weather only, but an umbrella is sometimes nice to have in our unpredictable climate.
I started with shaving off 1-1.5mm from the roof and lost 1.5kg. Then sanded and polished the roof. -Not need to be perfect if you do not bother about finish on inner roof when ready. After polishing I applied several layers of a release agent so the epoxy resin won't bond to the roof later.
Then applied 3 layers of resin and 2K carbon fiber on the roof. Using a putty shovel to spread the resin evenly worked better than using a brush. I was recommended to add a final layer of peel off weave as well. This should help flatting out and spread the epoxy resin. However, I found the peel off weave doing more bad than good. But not very hard to rip off.
The release agent worked very well so the skin was easy to remove from the roof.
Then it was time to remove most of the fiberglass. I just kept the frame and a thin cross for rigidity.
I epoxy glued the skin on to the frame and cut CF endings to fit the frame. Then sanded it and applied two more layers of resin (should not dry completely between layers). Finally wet sanded the roof and polished it.
I'm not 100% satisfied with the result. As you see there are some errors in the CF fabric, and also some smoky areas in the epoxy.
Therefore I didn't clear coat it as I may decide to paint it instead. Or maybe check paint it white/CF (Abarth style) to hide most of the bad areas. What do you think?
I applied three layers of CF but two layers would definitely had worked to obtain even lower weight without losing much rigidity.
The total weight is now just 5.4kg (12lb) so in total 9kg has been removed (incl insulation and inner roof).
Moving the roof in/out from frunk is so much easier now and that was the main reason for doing this. I am driving the car in dry weather only, but an umbrella is sometimes nice to have in our unpredictable climate.
Dr.Jeff
True Classic
Great job, I love it. 
I've been hoping someone would do a CF version to find out how light it can get. I still want to modify one of my roofs but haven't decided which direction to go...I hate working with fiberglass so I've never tried using CF.
Depending on how bad the imperfections are, it may not show much once the roof is on the car? But one option might be to paint it with a translucent color. It allows the basic CF weave to show but makes it "tinted" so it isn't as obvious. The more layers you add the darker the tint, and the less the CF shows through. That may hide the flaws. And you can choose any color of tint - that makes it look like the CF was colored.
I've wondered how a "brushed metal" finish might look on these tops. Could be stainless steel, aluminum, or any metal look done with "wrap" material.
I've been hoping someone would do a CF version to find out how light it can get. I still want to modify one of my roofs but haven't decided which direction to go...I hate working with fiberglass so I've never tried using CF.
Depending on how bad the imperfections are, it may not show much once the roof is on the car? But one option might be to paint it with a translucent color. It allows the basic CF weave to show but makes it "tinted" so it isn't as obvious. The more layers you add the darker the tint, and the less the CF shows through. That may hide the flaws. And you can choose any color of tint - that makes it look like the CF was colored.
I've wondered how a "brushed metal" finish might look on these tops. Could be stainless steel, aluminum, or any metal look done with "wrap" material.
Dr.Jeff
True Classic
Also with that fixed roof you can subtract all of the hardware that mounts the removable roof, for even more weight savings.
Bjorn Nilson
True Classic
Just like you say apples and oranges. 10,5 lb but that is only the skin? You still need a frame to mount it on to the body? The CF skin is much lighter, the most weight is in frame and fasteners etc. The whole idea is about having a targa roof, not a fixed roof.
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Dr.Jeff
True Classic
The fiberglass one is intended for a race car, so it is to be "fixed" or "hard-mounted" (not removable). That's why I said the weight of all the mounting hardware for a removable top is also lost with that one.
I'm guessing the box shape support in the middle might be for a air duct to cool the driver/passenger (rally car)?
Janis
True Classic
I think excellent.
I would keep as it is and do nothing more.
Bjorn Nilson
True Classic
Sorry that I didn't weight the skin exclusively without the frame, but it was crazy light. As I said, even two layers of CF would work on a roof, and it would be even lighter but still rigid.
- CF is very delicate and not a very forgiving material to work with. I did the targa top before fabricating my wing stands because I thought the top would be the easiest thing to fabricate and to learn from. -Big mistake
- What I've learnt is that big CF parts are more complex to make than smaller things.
- Vacuum is a good help (which I didn't have).
- Epoxy resin does not smell much and CF does not differ much from working with glass fiber
- CF fabric quality is important. Always buy CF on a roll as it gets distorted when folded (if you care about looks)
- Making strong structures is easy, but making them look good is tricky and time consuming (unless painting them).
Now I realize this is an easier thing to do than fabricating a roof skin, just because the parts are smaller.
Bjorn Nilson
True Classic
Yes that might be a good idea. I will wet sand it with 3000 grit to see how it looks.
Not a big deal. It is a rain cap, and forecast says sunshine for next week
.
Black-Tooth
Tony Natoli
Great work Bjorn! Looks great as well.
My primary goal was to get the top out of the "frunk" so shopping/storing could be done easier. Fortunately I rarely even carry the top these days.
I just had to compliment you on your work!
My primary goal was to get the top out of the "frunk" so shopping/storing could be done easier. Fortunately I rarely even carry the top these days.
I just had to compliment you on your work!
lookforjoe
True Classic
Nice work! Especially considering all the hardware, seals, etc., add up to over 5lbs!
Any detail pics in natural light that show the patches of cloudy/smoky effect ? I can understand not wanting to live with that....
Bobkat
1979 x1/9
Great Job! I was really wondering how much weight savings a skinned roof would have in CF. You took the hardest route to making a part with a reverse wet layup and the weight savings are substantial. I can only imagine a vacuum infused or prepreg would cut the CF skin weight in half. Great Job!! Now I am motivated to scan and make a mold of the spare roof CnC79X19 kindly donated to the cause. You took the most difficult method of doing it and the results are fantastic!
The issues with the weave is almost impossible on large panels with out using stabilized fabric. Most suppliers will have it and almost all will apply it to any fabric for you. On product is Web-lok. It is a very fine CF mesh that is applied to the back of the fabric to keep the weave aligned. It also make cutting the fabric a dream as the edges stay together. The Ghosting of the resin is most likely from the sanding process. It sometimes happens when that spot had a bit of a bad mix in the resin or was not quite cured enough and the sanding heats it up and hazes it. Not sure if it is the heat that changes the resing or the fines get push back in. If you use the roof for a few months then go back to sand it out you may be able to get rid of it.
I always am very picky about my carbon fiber work and nit pick the details about flaws and weave issues. But it is eye opening when you take a look at high end cars. At one coffee meet I as usual was taking pictures of carbon fiber details and was going over a McLAREN Senna and the flaws and gaps and holes filled with black epoxy were everywhere. They don't seemed bothered and no one drooling over the car cared.
I have a few questions about the FG frame. Are you happy with the amount you cut out? could you have been more aggressive? Do you think the ribs you left in the center really kept any stiffness?
Bjorn Nilson
True Classic
I cut out as much as possible from the FG frame. The remaining part is just as big to fit window sealings, snap ons and rear "fingers". I think it was a good idea to leave a cross. It helps keeping the shape and that would be even more important if going for two layers of CF. The weight of the cross is probably less than 10 grams so no big saving there. The roof is flexing a little bit when pushing on it, but it is very rigid at the cross areas so the cross is good to have.