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GT40 Tech - Exterior, Interior, AC, & Trim All that other stuff not in categories above.

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Old 19th July 2007, 10:47 PM   #1 (permalink)
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Interior finish of Gurney bubble

Hi guys. I'm looking for ideas and experiences with finishing the interior half of a Gurney bubble. Since mine is a street car, I can;t really leave it in its current configuration - see pictures.

I opted to fasten it to the roof with (6-32) screws, because I like that look on the original cars and because I didn't want to fiberglass it in. I'm thinking about releiving the inside fiberglass a bit for a little more head room and glassing over the gap between the inside and outside roof panel. Before I can glass that gap in, ouf course, I'll neet to fasten #6 nut - probably epoxy them to the bottom side of the outer roof panel but I'm open to alternative ideas.
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Old 19th July 2007, 11:09 PM   #2 (permalink)
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Re: Interior finish of Gurney bubble

Quote:
Originally Posted by Mark Worthington View Post
I'm thinking about releiving the inside fiberglass a bit for a little more head room and glassing over the gap between the inside and outside roof panel.
The underside of the bubble is flat? What's the point of that?
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Old 19th July 2007, 11:12 PM   #3 (permalink)
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Re: Interior finish of Gurney bubble

Hi Mark,

If you think you will never have to remove the bubble, why not epoxy the bubble on with the screws installed. That way you get the look you want but don't need to glue or rivet any "nutplates" to the roof.

Of course you would have to cut the screws to the correct length so they don't protrude into the cockpit!

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Last edited by Scott Calabro; 19th July 2007 at 11:17 PM. Reason: content
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Old 20th July 2007, 04:26 AM   #4 (permalink)
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Re: Interior finish of Gurney bubble

Mark,
I keep thinking about one of these.
My biggest worry was about that edge and approval by the SVA here in the UK.

Personally I will cut it back a lot more on the inside skin only and blend it with a taper and radius to the inner skin from 4-5 inches out.
People tell me that the top of the door is always weak and aleady flexes so I will also glass in some stiffening in between the skins as the strength will be considerably jeopardised around the fore and aft of the bubble there being pushed against the weather seal. This might also prevent crazing of you paint.
Are you fitting eyebrows also ?

Hopefully somebody will post a pic of the real thing before you start out.

Just my 2p.
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Old 20th July 2007, 06:37 AM   #5 (permalink)
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Re: Interior finish of Gurney bubble

Mark, I intend to stick mine down with 3M 5200, the mother of all bonding agents, and put screws in for decorative purposes. I think my door is hollow and if it is, I will be shooting in some expandble foam to stiffen door and provide a base for tapering the door into the bubble.

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Old 20th July 2007, 07:31 AM   #6 (permalink)
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Re: Interior finish of Gurney bubble

Ben, the underside has a very small taper and isn't flat. I haven't measured but I believe it allows a full 2" of additional headroom, which is more than I needed. I'm only 6' 0" tall, but have the torso of someone who is 6'4". My head barey touches the ceiling when I sit in the car, but without the bubble I would have to slump in the seat if I were wearing a helmet.

Jimmy, I think 4-5" relief of the inside panel might be a bit too much - I'm thinking something like 1.5-2". But it would be nice to see how other folks have done it. Yes, I have eyebrows also and intend to fit them.

Brian, you can see where I injected the expandable foam in the second picture - I drilled a 7/64" hole in the edge of the door and injected a bunch of Dow "Great Stuff" expandable, flexible foam sealant (I used the Door and Window variety). As you can see, the foam didn't fill the entire door cavity, and I need to get another couple cans of that goop. I'm also running it inside the spider cavity.

I guess a permanant seal with 3M 5200 or epoxy would make sense, since I can't think of any reason I'd need to remove the bubble after the car is finished.
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Last edited by Mark Worthington; 20th July 2007 at 07:50 AM.
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Old 20th July 2007, 08:54 AM   #7 (permalink)
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Re: Interior finish of Gurney bubble

Hi Mark

The underside needs to meet the 2.5 radius rule or it will fail SVA, ANDY
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Old 20th July 2007, 09:30 AM   #8 (permalink)
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Re: Interior finish of Gurney bubble

hi Mark, nice to see some shots of your car, not seen many for a time. Are you making yours as shiny as Brians?

I have just put a gurney into my car. I attach some pictures but I suspect they won't be as helpful as you would like because I glassed mine in. Well I didn't, Lee Dawson did. He did a great job and I highly recommend him.

A couple of comments, I think you might to look at the strength of the door top as you seem to have chopped out part of the inner moulding that I would expect to have given strength to prevent flexing. If you are to glass in that bit, can you glass in some ali or stainless reinformcment to replace the lost bracing? Your bubble seems quite far back on the door top.

The bubbles are tear shaped so is there a "right" way and a "wrong" way to fit them? I don't know, I left that to Lee to do as he saw fit. He had the original GTD template to help though.

I have used mine both with and without helmet. It made a big difference in head room and I no longer have to scrunch down with a helmet on. Huge improvement. I am only 6ft.

I would have put in eyebrows but no one seems to have metal eyebrows on the shelf. Plastic ones yes, metal no. There is a market there for someone....

I think Ron's idea of screw heads on top but glassed in in reality is the best solution. How often do you expect to remove this bubble? Maybe on a sunny day? My concern is having exposed metal projections into the cabin. Generally sitting in the car you may miss them but if you have a "moment" or worse, you could do yourself some serious damage!
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Old 20th July 2007, 10:50 AM   #9 (permalink)
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Re: Interior finish of Gurney bubble

Thanks for those pics, Malc. Nice job on your install. No, my GT isn't as shiny as Brian's, I've been kicking up some dust in the garage lately, which is a good thing.

I'm not too worried about door strength because the top of the door appears to be non-structural with its only function to keep the elements sealed out of the cockpit. With regard to location on the door, I sat in the car in the seat with my arms on the steering wheel and had my brother stand outside and position the bubble for maximum headroom. I guess I can call mine a Worthington bubble, because mine is customized for me!

Hmmm, I guess it would be fairly easy at this stage to glass in this bubble from the bottom and then just fill in the gaps with some body filler.
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Old 20th July 2007, 11:18 AM   #10 (permalink)
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Re: Interior finish of Gurney bubble

Mark, beware of lift at moderate speeds. I use a tongue to hold my door top down. You can see it in the pictures. If I removed it and ran say at 70 down the road, I would expect the door top to try and lift up. If you put eyebrows in as I think you are then that should reduce this concern.

An equivalent problem for some was the double vent nostril panels. You need to have a tongue on those at the windscreen edge to prevent lift due to higher pressures under the front clip. When you are lapping a circuit at a decent speed you could see 1 inch of air where the panel had lifted up! Big single vent nostrils (deep throats) don't suffer this build up of pressure in quite the same way. However cabin air pressure can build up if you have a double nostril panel. I used to get it and when I opened the little window, I could feel the release of pressure in my ears and sometimes even hear it! This pressure would push up on the door top.
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Old 20th July 2007, 11:22 AM   #11 (permalink)
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Re: Interior finish of Gurney bubble

One other thing if it is of interest to you, the painted finish on the inside of my car is a hand painted egg shell paint in the same colour as the external blue. With a textured glass finish and a bit of care, there are no brush strokes and it is real easy to apply. I have a painted balck (spray painted) dash so I hand painted up the windscreen pillars in black to the mould line just below the roof. When the bubble was put in I dug out my 15 year old paint tin, treated myself to a new brush and away I went!
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Old 20th July 2007, 05:10 PM   #12 (permalink)
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Re: Interior finish of Gurney bubble

We make the eyebroys in Aluminium !
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Old 21st July 2007, 07:04 AM   #13 (permalink)
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Re: Interior finish of Gurney bubble

Mark,

Be sure to dip the tips of your screws in the 5200 as you install each one, for a completely waterproof seal and to (semi) permanently lock them in place. FYI, 5200 cleans up quite easily with WD40. You WILL get it in/on places you don't want to, so be sure to have WD40 and some paper towels standing by.




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Old 21st July 2007, 12:52 PM   #14 (permalink)
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Re: Interior finish of Gurney bubble

Quote:
Originally Posted by wealdenengineer View Post
We make the eyebroys in Aluminium !
I wondered when you would post that! :-)
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