How to build a trunklid for any early coupe

This how to is one that I have used twice, once on a 31 Desoto coupe which I had no trunklid for, and once to create a steel louvered and operational trunklid in a glass 27 T Ford roadster. It is not really difficult, and if you have anything other than a Ford, it may be your only choice if your car came without a trunk lid. It works very well for cars up to and including 1932---once you get beyond 1932 there is too much compound curve in the trunklid to use this method.

 

I have found that all early coupes have a slight compound curve to the trunklid---that is to say, they curve a bit from side to side, as well as the obvious curve from front to rear. I start by using 4 large sheets of cardboard, setting them one at a time into the trunk opening, and tracing the profile of that particular side onto the cardboard. I then take 1" x 1" x 1/8" wall square tubing (mild steel), cut 4 peices about 12" longer than will be needed (this is important) and taking them to a metal fabricating shop that has a large set of plate rollers. I have them roll the individual peices untill they match the 4 profiles drawn onto the cardboard. It is important to have the peices cut about 12" longer than necessary because the first and last 6" on each peice will not get bent, but is used to start feeding into the plate rolling machine.

 

Once I have the 4 peices rolled to match the cardboard profiles, I drill two 3/16" holes thru the side of each peice, and through the side of the opening it is matched with. I install the peices with a 3/16" thick flat washer and a sheet metal screw thru them into the side of the trunk opening. The washer is what is going to ensure a uniform gap all around the trunk edge. I miter cut the ends of each peice at 45 degrees.

 

step 2 in the process---do the two sides first as shown---

 

Third step----add in the member for the top of the opening

 

And finally the peice which goes along the bottom of the trunk opening. Be very particular about the 45 degree miter cuts on the ends, and put a good deep 45 degree chamfer all around the mitered ends to hold the weld bead---

 

Next step---while everything is securely screwed into place, cut 4 peices of the same tubing (straight peices this time, no curve required) about 10" long. Miter cut the ends at 45 degrees and install them as shown. Get out the welder of choice and tack everything that you can---don't get weld on the washers. Put enough tacks on that puppy that when you remove all the screws and take the frame out of the trunk opening that nothing is going to fall apart on you.

 

Undo the screws, remove the frame, and weld everything solid. On the sides which will have sheet metal in contact, grind the welds down flush with the tube surface (thats why I suggested good deep 45 degree chamfers---we still want lots of weld left after the grinding flush process).

 

Cut a sheet of #20 gauge body metal, and leave enough material for a 1" overlap all around the frame. Use all the C-clamps, vise grip style welding clamps, that you have, borrow some from your buddies, and try to put a clamp about every 6" all around the edges---Don't get too crazy here---we want to pull the sheet metal skin in contact with the frame but we don't want to put dents and divots in the exposed surface. Cut a 1" square relief in each corner. Take a flat faced body hammer, and gently "persuade" the sheet metal all the way around the perimeter untill it lays flat against the edges of the frame. Do NOT try to do this all in one "go-round". it ahould be done in about 4 progressive steps, bending the flanges a bit at a time. You may have to take a "pie shaped" cut about 7/8" deep every 2 or 2 1/2" on the sides of the sheet metal in order to get it to follow the frame material without kinking. The top and bottom edges do not have such a pronounced bens, so will not need as many relief cuts (maybe none, depending on the cross-body curvature)

 

Man what timing, a buddy of mine is just starting to build a 32 that doesn't have a trunk lid. Funny how it works out sometimes, you come to the hamb looking for an answer and before you can ask it there it is .Thanks for the help and answer before anybody even got the question.

 

If you are lucky, and have a bit of talent, you will end up with this---weld the flanges to the sides of the frame BEFORE you remove all the clamps. Amazingly enough, even though it is a truly compound curve, there is enough "give" in the sheet metal to conform to most most of the cars from the twenties and early thirties without kinking or oil-canning.

 

In a perfect world, and with patience, it will end up like this. Of course, one point that I skimmed over is the positioning of hinges and a latch mechanism. This can be a varied as you want, but whatever method you choose, it should all be done before the skin is attached, while the bare frame can be put in and out of the opening and everything perfected BEFORE the skin goes on. The first time I did this, I just about fell down dead at how easy it was, and how well it worked. If you are carefull and take your time, there will be absolutely NO BODYWORK required on the exposed trunklid surface.---just a light skim of bondo on the edges (after you have finish ground all the welds).

 

Excellent!! Thanks for taking the time to share that!

 

Great tech, and it comes at a perfect time. funny how i too have to deal with a 31 Desoto and no decklid. thanks, this is going to be very helpful for me.

 

My '33 Chevy 5w and I both want to send our thanks......

 

Ive got time because I just got my 34 chev 5 window but I will save this post for later.

 

Tetanus Shot---Here is a pic of the much modified 31 Desoto that I built---The trunklid in the picture (as well as the tailpan, license plate cove, and tail light buckets) were all built from scratch.

 

great post. Very detailed, and usefull. I dont know where all the model A trunk lids went over the years, and a 500$ brookville lid isnt in the buget. Thanks

 

that is some nice work, mine is not going to be nearly as nice as that.

this is what ive got so far

 

excellent post, thank you!

 

Tetanus---I built mine about 20 years ago. It was the first "total build" that I had ever done. It turned out very nice, but by the time I was done all the mods there was over 100 feet of weld, all done with oxy-acetylene and .030 wire. I ended up using 13 gallons of bondo to get everything as straight as you see in those pictures. I spent 6 months with a board file on that coupe---of course, 11 of those gallons of mud got sanded off and ended up on the shop floor---Oh MY Gawd---I wish I'd had a mig then.

 

...I thank you and my 32 Desoto 3 window thanks you!!!
Great timing indeed.

 

Great tech! Thanks a bunch.

 

Very good- seat of the pants tech ,BrianAngus!

As an added side note,I posted here a few years back about makin a lid from an old roof skin.
A '49 51 Ford and 55 57 chevy have a compound that when used as a deck lid skin is almost perfect....I used the very rear half of the roofs.....Im sure the pics are gone but it is prob still in the archives Im sure....

 

Would 3/4" or even 1/2" square tubing be strong enough to work? I wonder if it would look better, so that the side edge, or 'jamb' of the trunk lid isn't so thick? In a perfect world, the edge of the trunk lid would be constructed so you only see the doubled-over sheet-metal, (like on most factory pieces) but that would be hard to build while supporting the lid.

THanks again, great post!

 

I found that smaller square tube was too flexible and did not hold its shape well.

 

Tonight I dug out an old scrap book (pre digital camera) and found a good pair of pictures for a "before and after" comparison . What you see is my 27 roadster that I built about 10 years ago, with a glass body. In the one picture there is no trunklid at all--just molded in. In the other picture is a trunklid I built using the above "how to" method. I cut out the opening in the fiberglass rear deck, framed in the opening with 1/2" plywood and fiberglass, and effectively created a "trunk". I then built a trunklid exactly as described in the thread and popped about 90 louvers into it. I used a pair of light compression springs as "door poppers" and the solenoid from an old Volkswagen starter for a hidden push button latch. The solenoid was powered by a push-button inside the car that only received power when the ignition key was turned on, so no-one could open the trunk unless I was there with the key.

 

see craiglist.com auto parts portland or. there is a lot of 34 chevy stuff right now!

 

any more info on how to build a hinge set-up from scratch?

 

I think it would be much easier to go find some donor hinges, unless you want them to be 'correct'. It seems like that would be a little tricky to build?