Jerry Feather

Here is a final set of pictures. I have left the project for the evening with some epoxy curing overnight. I am trying to refine the joint between the form segments with epoxy on each mating surface and then screwing them together tightly with double wax paper in between. I'm hoping that will help keep the surfaces and the edges more resistant to damage in frequent use. I hope I didn't duplicate any of the pictures.

Daniel5691

With amazing results like that, my input is relatively meaningless; but I've shaped some odd designs from wood by using a belt sander. It seemed like to me that having the sanding surface "fixed", and moving the piece over the belt, I had better fine control than when I tried using my smaller handheld sanders.
Jerry do you ever do any of your shaping with a similar belt set-up?
Thanks
Dan

crushingday

The problem with this is that the front end will be heavier after it rains due to water absorption. and the possibility of another Achilles heel beyond green wire, water pumps, and lower ball joints would be the potential for termites! .....oh wait, ...you meant,..never mind

Jerry Feather

Dan, with each one of these weighing about 15 or 20 pounds or maybe a bit more, they are pretty hard to handle on top of the belt sander. With the small disc sander I can manipulate it all kind of directions to sculpt what I want and can even use it for inside radii that would be difficult and limited on the belt sander. I do use my belt sander quite a bit, but only for straight flat surface work.

Later today I'll see how the method of hardening the mating surfaces is going to work on the two corner pieces I have layed up with the double waxed paper in between. If that is going to do what I want then I'll do the other mating surfaces. Then I'll start covering the outside surfaces of both forms with epoxy so I can begin to do the final finishing with files and my sander mouse. The epoxy is really hard so this process takes a lot of time and hand work, and contrary to the original sculpting, I can't do much of it with the disc sander; although, on second thought I wonder how that might work but with a much finer grit disc??? Maybe I'll give that a try, at least for the initial cut down of the epoxy.

While I'm doing this I'll make my final decision about how I am going to do the little bridge over (or under) the rear of the brake air duct. It will have to be formed separately and glued on. There is going to be a lot of other pieces to be glued on, so a lot of that still has to be developed.

Jerry Feather

The picture just two above here that has my fingers in it shows the comparative rear profile of the two versions of this spoiler as it relates to the outer aft corners. The inside line is the profile of the bump on the original spoiler and the upper one around the outer edge of the paper pattern is my later version that is going to put the bump that much farther up the edge of the front wheel opening in the bumper cover.

Jerry Feather

Dan, the second thing about your idea of the belt sander is that you cannot see or feel what the belt is doing as readily as with the much handier disc sander.

On another sub topic----the splitter has come up twice in this thread. I dismissed it lightly once and kind of ignored it the second time, at least so far as posting anything about it. I have however spent some mental time with it. My problem is that I guess I don't really fully understand it. Its not that I don't know much about aerodynamics, because I know more than most about that, and I understand about ground effect and such, but I don't know almost anything about exactly what the air is doing under the car in motion.

From my casual observations of splitters, mostly on various race cars, they seem to be most effective the closer they are to to ground. Since ground effect is most likely providing some lift to the car from underneath, the splitter will be trying to reduce the amount of air going under the car. But, since that air is now caught between the top of the splitter and the bottom of the front of the car, what is it doing? Some of it is going into the engine compartment causing cooling drag, and then going back under the car for more ground effect lift. What about the rest of it?

For me the real problem in trying to do this project and incorporating some kind of splitter is that they are diametrically opposed. I am trying to smooth up the front under side of the car from an appearance and esthetic standpoint, keeping kind of within the style design and lines of the original 928, while a splitter of just about any kind is just the opposite, seems to me.

In fact, one of my somewhat remote thoughts is that if this project amounts to much I may want to do something similar for or to the earlier cars. I have thought about doing a similar kind of spoiler for them with one version blank in respect to brake air vents and another to incorporate the S style brake vents/ducts. In that regard, my thoughts are to in fact eliminate the splitter effect of the S spoiler almost entirely in favor of something much more like the S4 spoiler. Too, it might even be incorporated with some kind of design of a belly pan or pans for those 928s.

Jerry Feather

I thought I would check on these two corner pieces before I go to the office this morning. Here are a couple of pictures of them, one with the waxed paper still in the joint and one where the joint is opened up. now I can screw them together and have them fit snugly with a very fine joint that wont show in the final forming of plastic and I can finish the outside that I have coated with epoxy.

Jerry Feather

I put the larger L shaped pieces of the form onto the basic piece with waxed paper and epoxy in between then screwed them together, then spread the rest of the epoxy over some of the outer surface. That is probably all cured by this morning, so I'll see if they will come apart then start working the outer surfaces smooth and into their final shape.

Jerry Feather

I bought a new larger, heavier cut wood rasp and find that it makes pretty short work of cutting the epoxy down to smooth finish. At this stage, the finishing process usually finds its way through the epoxy in many places where there are high spots that don't show up until now so that means another coat of epoxy all over to make a final total epoxy finish to form over. It needs to be final finish because they put some release agent on it in the vacu-forming process and that makes it difficult later to make changes, with epoxy, to the outer surface.

Now I am busy trying to get the design of the center section out of my head and into wood. With the angles and curves involved and since I am making a major change here in the spoiler, I am trying to put the design on paper first so I will better figure out how to carve it. Even that I have done three or four times before I now think I have it nearly correct.

As I mentioned before, the center section is going to become more of a finish to the bottom of the grill than it is now. It finishes the bottom of the grill now, but fairly far back under the front so that it does not really look like what it is actually doing. I find that the front bottom of the grill area of the front bumper cover is at about 65 degrees from vertical. I intend to have the front of the spoiler fall in line with that angle. That means that the front edge of the spoiler is going to move forward about an inch and a half, and down about 3/4 inch. Then the outer ends are going to be farther forward also and will in fact have a slight curve up over the bumper cover to fill in the gap.

I have cut a piece of plywood to start the center section with, but which will actually be added after I have laminated some Poplar wood to do the shaping of the front. Then I'll glue that to the plywood and finish the center out. That way, at least up to the sanding and rasping, the section wont be so hard to handle since I think much of it is going to get its basic shape in my mill and band saw. Then I'll fix the two together and do my final finish work.

With the move of the front lower lip of the spoiler down and forward, as described, that puts the air ramp inside of it down and forward that much. I think that means that there will be no need for the GTS holes in the air ramp for the oil cooler. The upper/inner edge of my new air ramp is going to be only less that half way up where the original air ramp was, and probably at a slightly lower angel. Its going to be interesting to see how it looks on the car.

Jerry Feather

I think I find that there is kind of a design flaw in respect to the front grill. The grill is made up of the upper edge and the two side edges. Then it has two grill bars that are mounted permanently within it. The upper grill bar is recessed about half an inch, and you would expect that the lower grill bar would be also. However, the lower grill bar is mounted more forward almost to the front surface of the grill. I think that is or was an effort to make the lower grill bar look more like the bottom edge of the grill rather than the bottom edge being put into the spoiler.

What I think that means is that when I finish my spoiler, with the center making up the bottom edge of the grill more prominently, it is going to look like the grill has two bottom edges with only one grill bar being recessed. I guess we will have to wait and see how it looks.

Jerry Feather

I have three layers of Poplar boards layed up with epoxy curing so I can start the mid section front. I need now to figure out how to make the pattern for the curvature. The grill bottom is 36 inches wide and the center of it is two inches forward of the ends. It is in a continuous curve. Maybe I can figure out some way to make a long compass with a pencil and string in order to strike an accurate arc. I wonder what the radius is?

I also used my left over epoxy to put another layer on the end pieces. I might be able to cut the curvature of front section by this evening, but it will be a couple of days before I can rasp on the end pieces.

I find that the epoxy runs for a while after it is layed up, so I am letting it run one way for about half an hour then I am turning the pieces 90 degrees and letting it run the other. Maybe that will keep it from all, of most of it, running off.

Mark R.

Amazing craftsmanship Jerry (as with all your projects, really).

Those wooden forms are a work of art in and of themselves...

Jerry Feather

Thanks Mark. I have always thought about making one of those merry go round horses with laminated layers of plywood sort of like this, but then I don't know what I would do with it.

I found out the radius. Its 83.5 inches. I used my tape measure and a piece of plywood on a long table out on the deck and layed out the arc with multiple pencil marks. Then I connected the dots and cut it out in the band saw then sanded it smooth with the belt sander. It works great.

I Have the Poplar boards laminated and the glue set enough to work with them so I used the pattern and cut the front arc at a 30 degree angle in my band saw. Then I sanded that smooth and then used my mill with a small fly cutter and cut the two corner radii. Next I'll connect the two rounded corners with an angle cut in the band saw fairly close then finish the air ramp up with the disc sander and rasp. Then some more shaping, but not so much as with the corner pieces.

Here are some pictures of my progress.

Jerry Feather

One last move for today--I went out and cut the segment off in between the two corners. I set the band saw back to zero degrees then simply cut the bevel for the air ramp. Then I ground it out further with the disc sander then the rasp and finally with the sanding mouse. I think it is almost perfect, but I'll coat it with epoxy then true it up with the rasp and sander. It will probably take two coats of epoxy, but I'll wait for the second one until I round out the leading edge.

Next I'll glue this to the body sheet of plywood then do the final shaping. This part of the center section is going pretty well. Next I need to make a form for an inner support structure similar to the original. It will be fairly complex, but, again, I think I have it pretty well worked out in my head.

MjRocket

Jerry, its amazing how fast this is moving along.. I gotta ask, where did learn to work with wood like this?