Projects Almost Funny - AWB Barracuda Funny Car Build

It takes practice like anything else, and small parts are much more difficult to mold than larger panels. I know friends that have used the Simonize carnuba wax as the release agent, and it worked great.
Another trick I learned from a friend, was to design the small molds so that you can hook a vacuum source to the mould. A very slight vacuum will pull the wetted mat into the mold and significantly reduce the number of air pockets.
My friend also made up a vacuum mold that he used to make a complex shaped canopy out of Lexan. It didn't require a lot of vacuum and made a perfect canopy on the first attempt. He was a sign maker, and was used to working with the materials, which made the job look almost too easy.
Back in the 70s, I made a couple of Lexan windshields for my airplane, and I found that by just bending it cold, 90 degrees, 8 inch radius, there were distracting light patterns in the Lexan, (stress), that distracted from an otherwise perfect job.
Good luck with your experimenting.
Bob

 

That makes me a little itchy just looking at it. Too much trouble to scan and 3-D print, or just too non-period correct?

 

jim, try using fleece, like old sweat shirt material instead on glass mat. you can hot glue it in place and then pour your resin over that, it more strength is needed you can add reg matting over the fleece. the fleece is way easier to mold around bends and such, it will soak up more resin though...be sure to ring me when you r heading through the area on drag week, ive got a room if needed for the night, and you know the shop.

 

Jim, I am working with fiberglass the last few days which I actually enjoy once in a while. As to making small or large parts where removal of the complex shaped part is difficult, what I do is to glass in a small air fitting and cover the end with a small piece of tape. If you brush or spray in two light coats of PVA you should be able to remove the part with a good blast of air on the fitting once it is cured. I have made complicated molds with half a dozen fittings and it works well.

Also most of the mat available in local stores is the 1-1/2oz chopped strand. In applications where it requires the mat to make turns or bends of go over flanges I always use 3/4oz chopped strand mat (available from US Composites). For instance if I make a mold of a panel that goes over a flange the 3/4 oz lays quite well in comparison to the 1-1/2 oz that has a tendency to not want to lay as flat when it goes over the edge. If you use several layers of the 3/4 it will be as strong and IMO stronger than the comparable thickness of 1-1/2 oz. I have made some parts with the 3/4 oz that are super light and pretty strong IMO. I am old school though and tend to use mat 99% of the time with fiberglass resin rather than some of the epoxies (which I am sure are quite good as well-just never used them in making panels). Good luck with your project. It is quite impressive to say the least.

 

Thanks for the tips! I have some 1 oz mat, which I considered using, it probably would have made it easier.

Anyways...as I figured might happen, the release didn't work right in a few places, because I did way too little surface prep on the plug, and also the draft of the part is pretty much non-existent, so I ended up cutting the plug part way across to get the part out of it. I have a few of these to play with, so it's not a big deal. The part I made is useable, with just a little bit of work, but I think I'll try making a two piece mold, with a flange through the middle of it, to see how that works. I plan to do some tricks with the flanges on the fenders I have to make, so this would be good practice.

I only had one area where the mat didn't lay into an inside curve and the gelcoat separated when I pulled it apart.

Fun stuff. The 'glass part weighs half as much as the steel part, but I made it a bit thicker than I thought it should be. I think 20 mils gelcoat, and two layers of 1 oz mat might be what I'm aiming for.

As for the successes....I did a good job of estimating the amount of materials to mix up. I think I got the "wetness" of the layup pretty good, it was fully wetted, but with texture showing, no smooth glossy areas that would indicate too much resin. And now I have a better feel for what it takes to get the mat prepared ahead of time, I was kind of going blind on that.

 

thanks for the offer! we'll probably be taking the southern route, I-10 and 20, but that depends on the weather, etc.

 

Can't wait to see the Hambers in the ATL for drag week.
Just another note the Saturday before drag week Sunday is a Southeast Gassers race at Paradise Drag strip little more than an hour away from ATL dragway. Lots of HAMBERS active at those events and they have show cars or any age appropriate rods featured trackside. I'm sure they'd love to see Jim and Brian and whatever other HAMBERS are in town. Of course I realize drag week is a demanding trip already and another day may not be feasible just thought I'd mention it and be sure everyone is aware.

 

A few ideas for you...

On the Lexan window edges, sand them relatively smooth, then wave a propane torch over the edge. It will melt, slightly, and end up very smooth.

I’ve used Bondo to make mold male parts before. Easy and pretty cheap to work with, molds well to details, and sets up fast. Vaseline can be used as a mold release, or you could get some actual mold release agent.

Vacuum forming pieces with PETG plastic can be used, too. Make the male, make a vacuum rig with a shop vac, and a frame to hold the PETG. Warm in the oven until it starts to droop, then vac it.




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I use urethane washers at a soft durometer and make the holes in the Lexan 3/32 larger in diameter. than the bolt going through it for expansion.

 

Its my understanding the flame polishing works well on Plexiglass but not on Lexan. The Lexan will burn before it melts. JJ

 

This is my understanding as well. Polycarbonate (Lexan) will char in this situation. It chars on the edge when it is laser cut as well.

You can flame polish the edges of acrylic and plexiglass but it is also brittle and prone to cracking where lexan will not. A guy I work with did a test on some 3/8" thick lexan sheet - from fairly close range he fired a .357 magnum handgun at it and the bullet did not pass through. We were suitably impressed.

 

I got a handheld power plane, it seems to work, leaves a decent finish. I just have to be very careful to cut the right depth.

Just don't get any loctite on your lexan....it's amazing the reaction that happens!

 

Or some brake cleaners.

 

Would expanding spray foam insulation (Great Stuff) work for making a "quick and dirty" short run mold? Or is it too much extra work to seal the surface of the mold to keep the resin from attacking the foam?

 

I don't know. Whatever I do, it's going to be a lot of work.

 

thanks, but I'm curious how the back and front will fit and how well they will attach using the lock strip molding (if that's the route you are going).

 

we'll see, one of these days. The windshield is going to be glass, so it should be fine.

 

There must be a story here, please share it with us.
Bob

 

I did some research on my own, and found this highly useful information. I have successfully bonded plexiglas with Crazy Glue, but have never had the need to bond Lexan.
http://thebestglueforplastic.com/Craftech-Adhesive-Guide.pdf
Bob

 

Ok, now I gotta try this when I get home to see what happens.



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it's not exciting, but it will result in the lexan cracking and falling apart. And of course, the thing you used loctite on is something that you don't want falling apart, that's why you used loctite on it!

 

Squirrel just saved probably 100 of us from testing this....

 

I hope you weren't going to try it!

Anyways...I decided to make the second headlight bucket the same way I made the first, and it worked ok. I made it a bit lighter, not so much 'glass. I guess I need to just go ahead and try to make a fiberglass mold of a fender, and see what happens.

Been working on the doors some more, trying to get them all finished up. I have most of the weatherstrip now, but not all, the roof rails were back ordered, and i goofed on the first pair of quarter divider rubbers I ordered, so I had to order the right (hopefully) ones. I cut the windows for one side, used my old band saw, and a laminate blade in the jig saw for the pieces that wouldn't fit the band saw (mainly, cutting a 20x30 in piece in half). I trimmed the edges with the power plane, then sanded them a little with the DA with 180 grit, they have that frosty finish on the edge, which is fine.

I'll have to do some work to get the door glass to behave, and I can't really finish the quarter window until I get the rest of the weather strip.

 

step by step...thank you for the tutorial.

 

Speaking of lexan, lay a junk piece on the floor and wack it with a BFH. It is remarkable what it will put up with. I had a piece of 1 inch thick left over from a machining job. Laid it in my yard and shot it from about 20 feet with a full metal jacket .45. It did not go through, just a BIG dent.

 

LOL- I can just see you doing that, Doug!

 

anyways...I've been tinkering and getting a few things done. Not much for pictures, sorry. Gas tank and radiator and transmission cooler mounts done, battery box secured, front floor riveted in (except the transmission tunnel). Fit the rear bumper, got the door "glass" sort of fitting and working on one side, door locks in and working. Painted the front of the frame, after welding on a few more brackets, then plumbed the brakes. I also spent some time staring at the shifter, and figuring out how to make it come through the floor gracefully, so I can seal it from weather, sort of. I had to slightly modify the mounting bracket to move it up and over just a skosh. I also made the linkage for the shifter and the throttle valve, using hex bar stock and Heim ends (I bought a couple left hand thread taps just for this).

And tomorrow I plan to haul it up to Tucson and see about getting the cage cert. Wish me luck.

 

Good luck on the inspection Jim. Really interested in how that tank location works out on your great build.

 

This car looks cooler than most even at this stage!
Nice Jim! REALLY looking forward to seeing it finished and racing.
The looks you'll get on the street alone will make all the work worthwhile!
You really are a master!

 

I am impressed by the amount of progress you are making on your project. It is encouraging to me, and gets me out there to get at least one task accomplished every day on my garage or on the truck. I can't wait to see your car run.
Bob