I have finished painting all the interior surfaces of my bonnet. And all the exterior surfaces are shaped and, with a little final cleanup, are ready for basecoat/clear. So this is the point in the project where I assemble the bonnet in preparation for mounting it on the car. This post will be photo intensive and is meant to serve as a tutorial for others.
I previously had the fully assembled bonnet mounted on the car. I temporarily installed an engine and tranny so as to flex the car. Then I made a final cut on the back edge of the center panel section. Next, I made a simple wood frame onto which I tipped the bonnet onto. This allowed transport to my paint booth. I laid the bonnet upside down on my body cart and fully disassembled it, leaving only the center section, upside down on the cart. Then every piece got painted with final basecoat/clearcoat. Which brings us up to date and leads to the current topic, reassembly.
There are many ways to go about assembly of the bonnet. Having it upside down on a cart is one of several approaches. It will be fully assembled with all fasteners left loose. Then it will be mounted back on the car and I will proceed with hopefully the final fitment, at which point all the fasteners will be fully tightened. I will then remove it one more time and apply paint to the various fasteners. As has been discussed here before, at the factory the bonnets were fully assembled and then painted in one go, which means all the fasteners would be body color. I am breaking this down into several steps. Paint the inside pieces, touchup paint the fasteners, and paint the exterior (along with the rest of the body).
I have access to an original bonnet assembly drawing. I will be inserting some details from this drawing which illustrate the factory intent regarding fasteners. I will also be inserting some details regarding the few parts the factory did not want to paint. Time for pictures!
First I mounted the wings.
The joint between the wings is pretty typical, in that it uses a 1/4″-UNC x 5/8″ bolt, two oval washers, a lockwasher, and a nut. One key difference is the special “distance washer” between the flange halves. I bought mine from SNG, they are cheap. They provide about a 1/16″ gap to allow later insertion of the clips to hold on the chrome bonnet bead. Here is a shot of a connectioon detail on the design drawing.
Refer to Section B-B. Some comments. BD542/3 Special Washer is the oval washer. In this case, they are on both sides of the joint. C10193 Distance Washer is the aforementioned spacer that holds the flanges apart. For the spring washer and nut, I used new items obtained from McMaster.com, as there is nothing special about them and they do not have any period specific markings. Here is a shot of assembled connection and also the various pieces lined up ready for assmbly. Not shown but the bolt does have period specific markings, in this case Rubery Owen. A modern bolt would suffice if you are not going for full authenticity. Also, in Jaguar parlance, a setscrew is a bolt that is fully threaded.
This combination of hardware is used a lot on the bonnet, with the exception that the distance washer is only used at the joints where the chrome trim will be added later. See Section J-J above, which is the same connection without the distance washer. In some areas, to be discussed later, the Special Washer is only used on one side of the joint.
Another connection that is common is the one that uses a large #14 (1/4″) sheet metal screw, which Jaguar called a Speed Screw. As you assemble your bonnet, you will immediately know where these go, since in all cases that I can think of, there is a factory spot welded “nut plate” provided on the back side of each relevant joint. Here is a photo of the box of these that I purchased from McMaster.com.
Here is the relevant detail from the factory drawing. See Section D-D. In most cases, it will use an oval washer. That said, you will find locations where an oval washer does not fit well. It will be obvious. In those cases, I used a standard washer. By the way, the oval washers serve to hide “ugliness” that will result from having to enlarge or relocate holes in the sheet metal. I guess what happens under an oval washer stays under an oval washer! Section C-C is an example of a joint with just one oval washer.
Next, I installed the lower nose section. With the exception of the short section under the headlight opening, it mainly uses 1/4″ bolts. Few of these joints are visible after the headlights are installed. Most locations just used regular flat washers on both sides of the joint.
Next I installed the short air duct, which feeds air to the carbs. It uses a combination of Section C-C and Section D-D connections.
Next, I installed the forward diaphragm, which is the one that holds the headlight buckets. These use a combination of Section C-C and Section D-D connections.
Here is a case where the oval washers just don’t fit very well, due to the close edge distance of the boundary of the diaphragm. Also, there is one vacant hole and one hole with a hex head bolt on the “upper shelf”. These will eventually hold P clips for the wiring inside the headlight area. You can see examples of the tack welded nut plates for the sheet metal screws on the right hand side of this photo. Also shown are the nut plates for the bonnet “balance links”. Now is a good time to clean the paint out of those threads.
Next I installed the rearward diaphragm. It used a combination of Section C-C and Section D-D connections.
A slightly odd thing I will note. On this diaphragm, it fits to the rear of the bonnet flange. On the other side, it fits forward of the flange. Also, the upper right hand bolt in this photo will come very close to the sill extension when you get the bonnet mounted on the car. Monitor this situation closely during your fitment of the bonnet on the car. This is true on both sides.
Next I turned to the other side. Assembly was very similar, until we get to the area where the air duct attaches to the “Extension Assembly” P/N BD 19730.
Air duct installed.
Forward diaphragm installed. This one has the largish hole that will ultimately accept the multipin bonnet wiring plug.
The rearward diaphragm. The holes marked with blue tape will be used to mount the air duct Extension Assembly. A slightly odd thing I will note. On this diaphragm, it fits forward of the bonnet flange. On the other side, it fits to the rear of the flange.
So that’s about it as far as the major pieces go. But I do have some details to discuss, if you are interested.
Where do these things go? (See the unpainted item in the photo below) I don’t even know what they are called but Chuck at Monocouque Metalworks supplies them in his bonnet flange kit. Here is a shot of one before everything is installed. And a few of post installation shots. They are hard to see. I gather they were added to maybe improve air flow through the radiator slightly? Before final installation, they get a strip of felt added to seal them against the underside of the bonnet.
There is another obscure L shaped piece supplied in Chuck’s kit. It goes at this joint associated with the rear diaphragms. It is fairly easy to see on the passenger side. On the drivers side, it actually extends through the diaphragm.
What doesn’t get painted? Well, at least what didn’t get painted at the factory during the initial paint effort? There are some notes in that regard on the bonnet drawing. It’s pretty obvious stuff like the headlight parts, the extension air duct, and the chrome bead and it’s clips on the bonnet flange joint.
Something I discovered just yesterday is that my air duct Extension does not fit. That will have to be another article. But it is something to check during the dry fit process.
Whew, that was a long article. Hopefully it will help.
PS I’ve posted this picture before but I find it rather striking. I think Abby Panels charged Jaguar something like 20 GBP for a completed bonnet. Hard to believe.