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914World.com _ 914World Garage _ Lighten trunk lid

Posted by: bpick84 Mar 1 2005, 09:08 PM

I need to lighten the trunk lid on my race car. (I don't want fiberglass and cannot use carbon fiber). Has anyone gutted a lid of the support structure? Is the lid a single sheet of metal or does it have a liner? Does anyone know of someone who makes an aluminum lid skin?

Posted by: xsboost90 Mar 1 2005, 09:13 PM

you should be able to grind around the inside edge of the lid, and w/ some careful prying and scraping get the skit cut off of the frame. Then make some mounts in the trunk like-6- and put some zchus fasteners on it.

Posted by: iamchappy Mar 1 2005, 09:23 PM

The steel ones lose all rigidity without the inner structure and become very flimsy and would bend easily.

Posted by: Travis Neff Mar 1 2005, 09:31 PM

You could cut the steel skin off the hood frames, then wrap it in alumninuminuminnujum , fold over the edges and bond with autobody epoxy.

Posted by: neo914-6 Mar 2 2005, 01:24 AM

Drill LOTS of holes in the structure...
Acid dip it until it's thinner...
Remove the hinges and latch and use rubber latches...
Look elsewhere to reduce weight...

Posted by: Brando Mar 2 2005, 02:32 AM

I like the drilling holes idea.

Just drill lots of holes all over the car. Although it might whistle a bit when you go faster than 40mph...

Posted by: neo914-6 Mar 2 2005, 02:55 AM

QUOTE
Although it might whistle a bit when you go faster

Not if you stretch light weight Saran wrap over it...

Wait, cut out everything except the basic framework and stretch material over it like old planes...

Posted by: Joe Ricard Mar 2 2005, 06:57 AM

I Paul already beat you to that.
Funny you should mention that aluminum thing. I have been meaning to go down to the local sheet metal shop and see what they can do. I think maybe a hybrd lid,
cut the steel skin off use the frame as a mold to make smaller fiberglass frame. then get aluminum sheet hammered into shape and bond it all together.

Posted by: xsboost90 Mar 2 2005, 07:00 AM

just get some buttons and some vinyl and make a tonneau cover.

Posted by: JmuRiz Mar 2 2005, 08:43 AM

QUOTE
Homer: "Hey, what are all these holes?" (points at bullet holes in car hood)
Car salesmen: "These are speed holes. They make the car go faster."
Homer (impressed): "Oh yeah, speed holes."

Posted by: brant Mar 2 2005, 09:41 AM

no pictures with me, but I did it and already have it in fresh paint for my race car.

You can't do the front due to the force of oncoming air that would just fold it in.

But we did the back.

After cutting out the full structure, the single sheet panel of metal is too flimsy to even hold its shape when set back on the car in a horizontal position.

We re- reinforced it
Used Balsa wood strips...(like a GT)

our rules say that we can not use a fiberglass panel and that the panel must remain metal.

So... using panel adhesive, we glued in aluminum stops on rt/left sides. Then cut balsa wood strips that are 1/2 inch long. Place them in between the stops and they bow the panel back up into shape. We glued the strips in with the polyurathane construction adhesive (is it PL-21?) and then smoothed and filled the cracks. Had the underside painted with the top.

Looks good

I saved the full cut out frame, thinking it would be interesting to re-skin it in alloy someday.

Cut the weight by about 11lbs total (If I remember correct) I think its 22lbs now?

Posted by: Travis Neff Mar 2 2005, 10:10 AM

Brant you gotta post a pic from up top and down below!

Posted by: brant Mar 2 2005, 10:17 AM

Ok..

car is 300 miles away at the moment..
I still have to install it onto the chassis, but will try to do so soon and post pics

Posted by: groot Mar 2 2005, 11:48 AM

Brant,

How thick was the aluminum you used?

Posted by: brant Mar 2 2005, 12:37 PM

QUOTE (groot @ Mar 2 2005, 10:48 AM)
Brant,

How thick was the aluminum you used?

Kevin,

I haven't made an aluminum one (yet)
the one I made was from the original sheet metal without the skeleton frame.

techinically an aluminum one might not be legal in my vintage class.

(however, since I have the skeleton I will be making an aluminum one after I get the race car on the track and a motor back in my street car... probably in july-ish)

Posted by: groot Mar 2 2005, 12:48 PM

Being a cheapskate and still wishing to lighten my car, I may use some 0.040" aluminum I have left over from my trailer build. Even though I already make min weight (1870 with driver) pretty easily.

BTW... with 0.040" the skin should be ~9 pounds.

I'm also interested in making my own because the trunk lid may be square, but the opening isn't, so I'll need to tweak anything I put on it. So, it may be easier done with aluminum than a fiberglass mold.....

I'll let you know how it turns out.

Posted by: groot Mar 2 2005, 12:52 PM

Brant,

If your rules say the trunk needs to stay metal.....and doesn't specify steel, you could capitalize on that.

Posted by: bpick84 Mar 2 2005, 01:29 PM

brant..thanks for the input. groot, the trunk lid is not square. I looked at it with a sheet metal man who has rollers, etc. The back is rolled over and radiused from side to side. A roller will not roll the back lip right. It is not as easy of a skin to copy as it looks like.

Posted by: Joe Ricard Mar 2 2005, 01:34 PM

Ah forget about it.

Posted by: groot Mar 2 2005, 01:36 PM

Yep, I noticed that. I'm going to try, but I won't be using a roller to do it. It may not work, but I going to lay the alum over the current lid and gently beat the snot out of it and then use shaped reinforcements to hold the shape. I'm not too worried about the edges looking pretty... race car only.

Posted by: brant Mar 2 2005, 01:50 PM

QUOTE (groot @ Mar 2 2005, 11:52 AM)
Brant,

If your rules say the trunk needs to stay metal.....and doesn't specify steel, you could capitalize on that.

agreed...

I've got to double check though... I think the rule may say: "constructed from the same material as stock"

meaning that technically they may not like aluminum if they ever put a magnet to it...

brant