Light Weight Rear Hatch for Drag Racing

[Doug Brown]

Weight reduction continues on RED, my non-street able BP drag racer.

I worked on the rear hatch today. Fiberglass was my first choice, but it was going to be a major pain and expense to make one. A member suggested reducing a door to just a "skin", so why not the rear hatch? So I went with totally gutting a standard steel hatch.

I can't find it in my notes but I believe that the hatch weighed about 45-lbs with glass in as well as everything else (hinges, hatch opening mechanism, brake light, etc).

Cutting just outside the seam area where the panels are joined, but leaving the seam for extra strength and helping to retain the shape, took about 6-hours of cutting with a cut off wheel, mini grinder, sanding disc and unbolting a few things.

The slightly re-enforced, partial "noodle" rear hatch - that does hold it's shape - now weighs 12-lbs without a window or mounting devices (hinges or such).

I plan on using a 3/32" plexiglass rear window glued and fastened in place, which is not only light but should greatly re-enforce the rear hatch from deforming (anti-noodle!)

I'll use a hood pin type mounting system and should be able to keep the total weigh at 14-lbs. This is a 31-lb weight reduction from the rear of the car.

Again, this is a non-street able drag racer - so this rear hatch isn't very appropriate for a street car.

If you are going to do this mod, MAKE SURE you wear full protective clothing - painter's head covering, full face shield, ear muffs, gloves and a long sleeve shirt!!!!

[mikemounlio]

Wow thats great man!

[firebush357]

What is the ETA for the first Track Day?

[Advancedynamix]

Great work Doug! That even looks nice! I plan on doing the same thing, and this is motivation. It's great to see it done first.
I think I've seen aluminum hood pins on eBay. That would be a smidge lighter than steel pins.

[ryanprins13]

I think I've seen aluminum hood pins on eBay. That would be a smidge lighter than steel pins.

Does a couple grams here and there really make that much difference? I see that kind of thing a lot but wouldnt not eating before the race be more beneficial? Or going on a diet? Or 250ml less gas in the tank?

And doug- make sure you dont do the 1/4 with an open window. At 200km/hr that hatch may drastically change shape and rip off [emoji14]
But maybe not, im just imagining it turning into a parachute shape but it could be stronger than it looks



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[william]

Did this to my circle track car hatch and doors.
An air hammer with a cutting bit opens them up like a tuna can.
About 10 mins a door. I ended up just leaving the hatch off after I talked with tec on my first race and they said no hatch was fine.
Also skinned the hood of a 86 toyota tercel (previous racecar)
And put it on with 4 pins.
The width of the tercel hood is perfect ( within a mm or 2)
But us about 4.5 inches longer this covered the cowl and made it easy to attach with the 4 pins.

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[Doug Brown]

Thanks everyone for the feed back. Here's some replies to questions asked:

ETA for first drag race. I'm not to sure....maybe this year, next spring for sure. Depends how the budget holds up!

Hood Pins. I've seen those too. The also make "gun drilled" hood pins - sort of going to the extreme there! I think it came out looking pretty nice too. Looks better today - I spayed it primer gray, tomorrow it gets sprayed Sunrise Red.

A couple of grams.... I plan to loose 35-lbs. Everyone wins by me doing that! While the hatch is somewhat of a "noodle", it is much stronger than it looks. It should stay put once I make up the mounting hard ware.

I had to have a crew member helio-vaced off my ship once and left the door to the bridge open so I could see where everyone was. 250-knots of rotor downwash turned the bridge into a snow storm of papers, charts - whatever wasn't fasten down went airborne. So I know what you mean about open windows!

Air Hammer. I'm really horrible with an air hammer and chisel blade - I put all kinds of holes into things that I didn't want to have holes in! But I do like 10-minutes per door to get it done.....

While the primer has been drying on the rear hatch, I started lightening the passenger door today. It's coming along pretty good and once I get both doors done then I can mount my new frame rails that Rick made.

[lessersivad]

Does a couple grams here and there really make that much difference?

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Seems like I recall many years ago in Hot Rod magazine I think it was. They used the phrase "Concentrate on the ounces and the pounds will take care of themselves".

[Advancedynamix]

Does a couple grams here and there really make that much difference? I see that kind of thing a lot but wouldnt not eating before the race be more beneficial? Or going on a diet?

Every ounce (29 grams) does count. Putting TQ to the ground in any drag car is an art of weight transfer and perfectly matched TQ curve. A FWD car is even more sensitive to weight than a RWD car. Each ounce is multiplied with inertia. Ounces become lbs quickly in a race car.
I'm sure Doug will have the fuel load calculated (he's going to the trouble to mount a fuel cell in the front bumper) and he'll probably try to shed a few lbs as well as shave every ounce off of his car.