SKIRT Material

[SPARKY]

The bottom of Ratical is flat;  after tuffing it at speed week---I need to put some skirts like Ron Main has on Speed Demon.  Does any one have any recomendations on material and attacment techniques---Thanks in advance wmts

[Ratliff]

ABS plastic (ABS is a specific plastic alloy) or polycarbonate sheet.

[jl222]

The bottom of Ratical is flat;  after tuffing it at speed week---I need to put some skirts like Ron Main has on Speed Demon.  Does any one have any recomendations on material and attacment techniques---Thanks in advance wmts

    What is tuffing it? If your talking about sealing the sides of the body the old Chaparral road racer with the sucktion fans
used Lexan polycarbonate plastic .o90in thick and a means to raise and lower them with the suspension.
  CHAPARRAL [ Motorbooks international]
     
                          JL222

[Blue]

ABS plastic (ABS is a specific plastic alloy) or polycarbonate sheet.

I think we are looking for information from QUALIFIED people who actually build RUNNING cars.

Some people have used rubber strip, acrylic, polycarbonate, ABS, thin fiberglass, etc.  Sparky was asking about who had real experience at high speed with what material.

BTW, Rat:  weren't you banned from here in addition to 4 or 5 other sites?

[Ratliff]

ABS plastic (ABS is a specific plastic alloy) or polycarbonate sheet.

I think we are looking for information from QUALIFIED people who actually build RUNNING cars.

Some people have used rubber strip, acrylic, polycarbonate, ABS, thin fiberglass, etc.  Sparky was asking about who had real experience at high speed with what material.

BTW, Rat:  weren't you banned from here in addition to 4 or 5 other sites?

Nobody else was stepping up to offer any advice.

And since the bans instituted in Indy Car, Formula One, Le Mans, etc, nobody in oval track or road racing has any current experience with skirts.

Jim Hall used polycarbonate for the skirts on the Chaparral 2J "sucker" car.

Attached are photos showing how the skirt installation was done on the Bruce Crower car.

[manta22]

Sparky;

You might try attaching strips of UHMD (ultra- high molecular density) polyethelene. This stuff wears extremely well; it's used as a liner for industrial conveyors, etc.

Regards, Neil  Tucson, AZ

[Ratliff]

Sparky;

You might try attaching strips of UHMD (ultra- high molecular density) polyethelene. This stuff wears extremely well; it's used as a liner for industrial conveyors, etc.

Regards, Neil  Tucson, AZ

That's another great material, and maybe the best choice. Along with its other qualities, it has excellent resistance to abrasion.

[Carl Johansson]

we use this stuff to build airdams and skits in oval track racers as well as open road racers -  easy to work with -  riveted, screwed or other ways to mount it.  cheap easy tough stuff.  it grinds itself down to the proper height as we get pushed lower by air pressure!

http://www.speedwaymotors.com/p/1557,229_Colored-Plastic.html

Carl Johansson

[SPARKY]

Should have known Speedy Bill would have something!!!!!!

[JimL]

I put black ABS skirts on the Wagner Roadster and we found that the stuff grew in the sun/heat.  It buckles and gets wavy, and does NOT shrink back to original size.  It worked well, and bolts on nicely....just gets wavy.  I had to add aluminum angle behind the longer runs to keep it from opening gaps at the bottom edge of the body.  I used the thick stuff (I think it was 3/16 or 1/4).

One thing that did happen, was that I set it up as a tunnel under the car (closed at front, open at rear of the 27T body).  That gave us problems with the car sucking the belly pan downward, under the engine (that area was a separate pan, closer to the salt because of pan and bellhousing sizes).  In 2000 it sucked the belly pan down far enough to buckle and crack it.  We were open on top of the engine, so I guess the pressure differential was enough to cause a problem.

food for thought,
regards, JimL

[manta22]

Jiml;

If the belly pan was getting sucked down that far you were generating some serious downforce.

Yes, ABS expands quite a bit when it's heated; to minimize the "waviness", use short strips instead of long ones and mount the ABS with screws in oversized holes to allow a bit of expansion.

Regards, Neil  Tucson, AZ

[SPARKY]

Jim, Thanks for you posting your experience. Did you just attach it to the sides of the body---I have lower body U sections that are around 40" long-- so I could easily have  "expansion joints".  I was thinking of sandwiching it between the body panels and a thin flat strap. your coments please

[Loose Goose-Terry#1]

  You might also think of using the "plastic" baseboard molding that you can get at any Home Depot or Lowes...worked very well for us  and it is cheep.
Terry

[Glen]

Just be sure it will do the job, we pick up a lot of stuff off the courses each year. The one big item this speed week was a full (4Ft X 8 Ft) fiber glass belly pan. Is was a stock panel from a hard ware store and was held on with a bunch of # 8 self drilling sheet metal screws about 1/2 inch long. There were 4 alum cross retention straps as well and all of if came off the car about the 1 mile. It took awhile to find most of the screws.

The plastic molding can be brittle and shatter. Choose wisely on what you use. What works at slower speeds may fail at higher speeds. In many cases we never hear that parts were lost until the crew gets back to the pits. It's important to look over any vehicle at the end of the run and to notify the timing trailer so we can look for it. That's why we insist on a good working CB radio.

[JimL]

I had metal tabs, about 2" long, welded to the bottom of the frame (hanging vertical).  We bolted the ABS using button head screws and nylock nuts.  Regarding the downforce situation...I think it may have been pressure inside the car.  The engine was not fully enclosed, and the front edge of the intercooler was square/flat.  We did have some downforce issues, because in the years the car had front suspension it was pushing the skirts into the ground.  Here's a pic of ground clearance at rest.  It rubbed away about 1/8" of material during the record runs.  Also a pic of my poorly streamlined engine hood (you can see the ABS skirts).  I like the idea of shorter strips of ABS...the two long ones, each side, were a pain to deal with.

Regards, JimL