Lighter weight 'convertible' targa top

[Bjorn Nilson]

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....

On photos it looks ok, but in real life it is so, so. I tried to sand it down with 2500 grit to get a hint how it would look with a matte finish, but the color is changing to grey so that didn't work. I will see if a clear coat will remove most of the imperfections.
Stupid question: If I wet sand the matte clear coat with super fine grit, and then polish it, will it become glossy then?

 

[Bobkat]

On photos it looks ok, but in real life it is so, so. I tried to sand it down with 2500 grit to get a hint how it would look with a matte finish, but the color is changing to grey so that didn't work. I will see if a clear coat will remove most of the imperfections.
Stupid question: If I wet sand the matte clear coat with super fine grit, and then polish it, will it become glossy then?

You would have to remove the matte clear. It will always look dull. Good thing most matte clears are very thin. Are the area that are turning grey with the sanding actual CF. Have you sanded it down in to the fabric? Matte will hide some of the flaws but will make uneven surfaces stand out. I think you may be too critical of your work. CF is really hands on and the problem with that is you become intimate with every square inch of it. Most likely you will be the only one that notices.

Have you thought about painting it white or black but leaving one or two stripes of the CF to show?

 

[Bjorn Nilson]

Are the area that are turning grey with the sanding actual CF. Have you sanded it down in to the fabric?

No I just sanded the epoxy. What I meant was that the roof turned to dull grey after drying. When a little bit wet it looks quite ok even at the smoky spots. And I assume that is what it will look like after applying the matte clear. I will buy a 2K rattle can tomorrow and give it a try.
I am thinking of check paint it white/CF if I still find it not good enough. Or stripes.

 

[Dr.Jeff]

The dull appearance after sanding is just from the "rough" surface caused by the sandpaper. It will get back to being brighter if you either polish it or clear coat it. At least that's how it is with epoxy paints, I don't have experience with CF epoxy so just assuming it is the same. Bob can tell us for sure.

Maybe add a little tint to the clear coat; either smoke or any color you want. It will be translucent to see the Cf under it, but less so. That should help hide the imperfections.

 

[Bobkat]

No I just sanded the epoxy. What I meant was that the roof turned to dull grey after drying. When a little bit wet it looks quite ok even at the smoky spots. And I assume that is what it will look like after applying the matte clear. I will buy a 2K rattle can tomorrow and give it a try.
I am thinking of check paint it white/CF if I still find it not good enough. Or stripes.

Are the smokey spots just lower dips in the surface that the wet sanding is not hitting? If you wet sand up to 800 then spray the matte it will have enough tooth to hold but be fine enough to not show the sanding lines through the thin matte paint. I go back and forth with gloss or matte. My personal preference always come back to matte for my own cars.

The dull appearance after sanding is just from the "rough" surface caused by the sandpaper. It will get back to being brighter if you either polish it or clear coat it. At least that's how it is with epoxy paints, I don't have experience with CF epoxy so just assuming it is the same. Bob can tell us for sure.

Maybe add a little tint to the clear coat; either smoke or any color you want. It will be translucent to see the Cf under it, but less so. That should help hide the imperfections.

Epoxy can be treated like sanding out clear coats to polishing. Same process and same results. Depending on the epoxy and method of layup it may need a clear coat for UV protection. The epoxies are getting better and better so some offer good UV protection.

 

[Bjorn Nilson]

Got the top back from the paint shop today. As it didn't turn out very well glossy, I decided to have it clear coated satin matt instead. Some smoky areas are still there in bright sunlight, but not as noticeable as before. The errors in the fabric are still there, but not as visible as when the roof was glossy. After all it is only a rain cap so I consider this is good enough. Maybe I'll add two white stripes to cover my mistakes even more. My main target for this project was weight reduction and at least that has been achieved.

 

[Janis]

Got the top back from the paint shop today. As it didn't turn out very well glossy, I decided to have it clear coated satin matt instead. Some smoky areas are still there in bright sunlight, but not as noticeable as before. The errors in the fabric are still there, but not as visible as when the roof was glossy. After all it is only a rain cap so I consider this is good enough. Maybe I'll add two white stripes to cover my mistakes even more. My main target for this project was weight reduction and at least that has been achieved.
View attachment 48366

Leave as it is without stripes

 

[Dr.Jeff]

Got the top back from the paint shop today. As it didn't turn out very well glossy, I decided to have it clear coated satin matt instead. Some smoky areas are still there in bright sunlight, but not as noticeable as before. The errors in the fabric are still there, but not as visible as when the roof was glossy. After all it is only a rain cap so I consider this is good enough. Maybe I'll add two white stripes to cover my mistakes even more. My main target for this project was weight reduction and at least that has been achieved.
View attachment 48366

Looks excellent to me. And I'm with Janis, no stripes.

 

[carl]

The person who does the work (you in this case) always knows all the defects on something. Odds are no one else will notice them so leave the stripes off or any other attempt to "hide" the defects that only you are in angst over.

 

[Bobkat]

So finally getting around to getting a roof clean, repaired and smoothed for making a mold for Carbon Fibre skins. I had also planned on making a Stratos style roof scoop but there is not a whole lot of room in the Frunk for additional thickness on top. A NACA duct would serve the same purpose and would fit in the storage without an issue. I really would prefer to do the scoop. Thoughts? Scoop or NACA?

Also for those that have lightened the roof, how much is the maximum people have cut up to the molded edges? I notice a lot have left a rim around the edge. Has anyone gone super aggressive? Even drilling holes in the frame part?

 

[DanielForest]

I will go for the hood scoop. But for a different reason: the opening will be facing the rear and the scoop will be to provide some clearance for my helmet when racing in the rain. But it probably won't fit in the front trunk so the NACA duct look like a logical choice if you intend to use it on a regular basis, of getting a really low profile hood scoop. Maybe also if you fit the scoop offset, i.e over the driver's head.

 

[Mike Petrecca]

I like the looks of a scoop. Any chance you could make it removable for storage purposes?

 

[Bobkat]

I will go for the hood scoop. But for a different reason: the opening will be facing the rear and the scoop will be to provide some clearance for my helmet when racing in the rain. But it probably won't fit in the front trunk so the NACA duct look like a logical choice if you intend to use it on a regular basis, of getting a really low profile hood scoop. Maybe also if you fit the scoop offset, i.e over the driver's head.

from what I can measure with a tin foil ball. There is only 3/4 of an inch of clearance between the roof and one of the support beams on the lid. Not a lot for a scoop

 

[Dr.Jeff]

I'm not sure if having a permanent scoop or duct opening would be extremely practical if I intended to use this roof all the time. And to me that would be the intent of having a light weight roof, so it would be easier to use on a daily basis. Perhaps if it was possible to incorporate a closable duct that was water tight?

Otherwise I guess two light weight roofs would be needed; one with the opening and one without. But that also isn't practical for regular use.

 

[DanielForest]

Making the scoop removeable would be easy. Making it removeable AND waterproof is another thing...

 

[dllubin]

How about putting a scoop on the frunk lid to provide clearance for the roof scoop? If you face it to the rear and exit the radiator cooling air through there it could give you the cooling and aero advantages of the recessed frunk cooling air exits done to some cars. Of course, you would need to make sure it doesn't block your view.

 

[Bobkat]

I'm not sure if having a permanent scoop or duct opening would be extremely practical if I intended to use this roof all the time. And to me that would be the intent of having a light weight roof, so it would be easier to use on a daily basis. Perhaps if it was possible to incorporate a closable duct that was water tight?

Otherwise I guess two light weight roofs would be needed; one with the opening and one without. But that also isn't practical for regular us

Making the scoop removeable would be easy. Making it removeable AND waterproof is another thing...

Hood scoops can be made weather proof with a plug. I imagine NACA ducts could have a plug also. The idea would be to have a light weight roof with more air flow. Funny the side vents on the dash are hardly water proof. I never drive my car in the rain but have been spit at by the vents after a wash.

 

[Dr.Jeff]

One possible option to increase air flow with your custom roof was discussed in a previous thread about making light weight tops. That is to cover it with a mesh material so it can breath through all of the 'cutout' areas. There are fabrics made specifically for this; they allow a little light in but still protect from direct sunlight, and they allow some air flow but still offer wind protection. Obviously it isn't waterproof but neither is a duct or scoop in my opinion.

Lighter weight 'convertible' targa top

My winter project for the X this year was a lot easier and less expensive than some of my other projects from years past. Tired of lugging and stowing my 25 lb. insulated targa top, I bought a spare top on eBay along with some convertible top material and trunk liner material. Tools I used...

xwebforums.com

 

[Bobkat]

One possible option to increase air flow with your custom roof was discussed in a previous thread about making light weight tops. That is to cover it with a mesh material so it can breath through all of the 'cutout' areas. There are fabrics made specifically for this; they allow a little light in but still protect from direct sunlight, and they allow some air flow but still offer wind protection. Obviously it isn't waterproof but neither is a duct or scoop in my opinion.

Lighter weight 'convertible' targa top

My winter project for the X this year was a lot easier and less expensive than some of my other projects from years past. Tired of lugging and stowing my 25 lb. insulated targa top, I bought a spare top on eBay along with some convertible top material and trunk liner material. Tools I used...

xwebforums.com

A roof scoop is water proof if it is combined with a rally style roof vent. Both scoop and naca would have to have some way of controlling air.

 

[Bryce-o-rama]

We have another targa roofed Italian car in our garage:

I got my wife one of these sun shades for it. That material would be ideal for a top that is airy but keeps the sun at bay. It certainly would not be weather tight though.