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asims View Drop Down
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    Posted: Jan/20/2010 at 8:05pm
I'm looking to see what kind of experience other teams have had doing composite (particularly fiberglass) body panels.  We're in the midst of making ours right now and it is taking forever.  We're using a three-step process of molding a positive plug on the frame, making a negative mold of that, then finally laying up the actual fiberglass for the panels on that.

So far the plugs have been very time consuming.  We're laying a base of fiberglass on the frame, then carving foam to get the contours we want, and then covering all that with bondo and sanding until smooth.  This is taking many hours per panel.  If anyone has any advice on making the process go faster or any general information for that matter, it would be much appreciated.  Also, estimates on how long it takes your team to make molds would be useful to see if we're making similar time.


Edited by asims - Jan/20/2010 at 8:16pm
Andrew Sims
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2010 at 8:44pm
frankly if you want a good looking panel, you are going to have to take your time. last year, we did fiberglass over a mould in maybe less than 24hrs and it came out pretty bad...The guy from the formula team that was making their nose cone too 3 days just to SAND the positive plug..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2010 at 8:48pm
Okay that's reassuring, but not particularly encouraging for our schedule Confused.  The sanding is definitely the vast majority of the time for each panel.  At the rate we're going I can't imagine how rushed we would be if we tried to crank one out with only 24 hours of work.

Edited by asims - Jan/20/2010 at 8:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2010 at 9:45pm
yea well we didnt, it looked terrible...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ehunt Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2010 at 11:23pm
weeks, with lots of people sanding and helping out, taking the time at the beginning definitely pays off in the end
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 1:24am
The fastest way to make sweet panels would be find a sponsor with a CNC router with a big table, and have them run the molds out for you. Then run some vac form plastic over it. 

Short of that, good looking fiberglass panels are tough. I know we never pulled it off well. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SDTech Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 3:26pm
Why fiberglass?  AL sheet is lighter, cheaper, and way faster to make.  If done right it looks as good or better than a fiberglass panel.    
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 5:21pm
Originally posted by SDTech SDTech wrote:

Why fiberglass?  AL sheet is lighter, cheaper, and way faster to make.  If done right it looks as good or better than a fiberglass panel.


Plenty of reasons.  With fiberglass, we have a lot more design flexibility, especially for large, sweeping curves as well as smaller details.  We've already made some really good looking contours that I know would have been a nightmare in aluminum.  Also, we're planning to make these as thin as possible, so the difference in weight will be negligible.  Once we have these molds made, we'll be able to duplicate any damaged panels within just a few hours.  On top of all that, it keeps things challenging, and its nice to learn new techniques.  We also have a very large team, so its a good way to get everyone involved.  We're building a new car as well as re-entering last year's car, and even with that much work going on, there's still people who aren't as involved as they want to be.

Is it hard, expensive, and time consuming?  Absolutely.  But we think its worth it.  Plus, we want a better body than Cornell this year Tongue


Edited by asims - Jan/21/2010 at 5:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blue2kss Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 7:13pm
making the panels how you stated is the only way to do it IMO.  we had carbon panels last year (three layer of 5 oz in some places like the corners and bends, two everywhere else) and we did them that way.  we (i should say Mike) spent months making the molds but they turned out perfect.  we were blown away when we pulled the parts how nice they turned out, but it was all due to the prep of the plugs and molds.  Each body panel was a fraction of a pound when they were laid up with the vacuum bag. 

I wouldn't want to do aluminum panels, but its just personal preference.  I like how the composite panels turn out when you put the right amount of work into them and popping more panels is no problem once the mold is made (try doing that with AL).  We run a new set of panels for every race because they get so banged up.   


Edited by blue2kss - Jan/21/2010 at 7:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 7:19pm
Okay, sounds like we're on the right track then.

does anybody have a preferred method or any special hints for making good negative molds?  Right now we're debating a couple different ways to do that, so I'd be curious to know stuff like how you've prepped the surface of the plugs after sanding, what you've used as release agents, how you laid the molds themselves, etc.

Thanks for all the help guys, I appreciate it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motomike Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 10:35pm
First and for most I would like to tell you that you are definitely on the right track.  That process is the only way to go if you have the time and man power.  The ease of being able to pull panels at will is priceless (although it may not seem that way now).  To answer your first question earlier, yes, it takes a LONG time to produce a quality mold (unless of course you have a CNC cut mold, then its cake).  The plug that we made for our panels took a couple of months, granted there were very few people working on them and im a little anal when it comes to waves and discrepancies.  However, the bright side is that once the plug is done and perfectly sanded, you are over half was complete with the whole process.  I say that because once you pulll the mold off of the plug and do a little fine sanding (if done right there shouldnt be much at all) the parts can be easily mass produced (in figerglass, kevlar, carbon, or a hypbid of all).

Moving on to the next issue... the mold making.  Im sure you realize this but you have only ONE shot at this.  If you do not get the mold to release from the plug you are screwed.  All that work you did you perfect the plug was in vain.  SO... to be extra sure that you are going to be able to have seperation you need to do this: rough sand till the desiered shape is formed, progressivly move up in sand paper grit till...lets say maybe 1500 (all this is a little hard to remember seeing ive been out a while so do your research as well). Then you need to wet sand the plug. after wet sanding the surface should look shinny.  Next step is wax.  Throw a minimal of 5 to 6 coat (more if you got the man power).  This should make the plug very shinny. ( i would use mold release way, you can find it on websites like fiberglasssupply.com)... some would stop here but to make extra sure (and i highly recomend this) spray a couple of coats of PVA on the mold) you will need a spray gun for this.  Remember though, thin coats and let the coats dry before spraying the next on.  if you think that this is taking too long just look back at the time aready spent making the mold and the extra steps may be worth it.  Once the PVA is dry, you can paint (or spray) on the gell coat and start making the mold. and another word of advise, make sure you have all positive slopes on your plug (meaning that when you go to pull the mold, there will be no negative sloped sides resisting it from pulling out, if there is in your design you may need to make a two part mold)

Now these my ideas from research and a lot of mistakes.  Ive made perfect plugs and seen them ruined because i could not seperate them cleanly. NOT FUN!

A web site that really helpped me out was http://racingcomposites.net/   There is A LOT of good information on there and everyone is relavily sharp. Let me know if you have any more question, Im more that willing to assist in any way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motomike Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 10:43pm
all the process (plug making, mold making, parts..blah blah) are very well explained in the website i gave you.  Word of advice on the mold making... if you are not going to spray the gel coat on (which is unnecessary (in my opinion) and requires a different spray gun) make sure you do two coats of gel coat, one in one direction, let it tack up till you can see a finger print, the the next in the direction perpendicular to the last, let that tack and then start laying your fiberglass.... again, the rest can be researched.  hope this helps, are you going to wet lay up, vacuum bag, or infuse the actual parts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2010 at 11:01pm
The plan is vacuum bagging right now.  Are there any particular advantages to the other processes?

When you talk about preparing the plugs, is it necessary to paint or otherwise seal the bondo before applying wax and release agent, or does it go straight on the bondo?

Thanks for all the help.  We're planning to have a solid 6-10 people working on panels this weekend, so hopefully we can knock out a lot of sanding.


Edited by asims - Jan/21/2010 at 11:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thompm1 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2010 at 4:13pm
Ascetics is one of the largest driving factors in design judging right now and boy do those judges just love composites.  If your going to do it take everybody else's advice so far, take your time.  

Remember tho that you can make AL sheet metal look just as good, but you have to put almost the same amount of time and effort in to doing sheet metal right.

Final word- Judges want a car that looks fit to finish, and they really do like their composites.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asims Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2010 at 10:08pm
Yeah, we want a just-rolled-off-the-showroom-floor look, since that seems to be the deciding factor when all other elements are more or less the same.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motomike Quote  Post ReplyReply Direct Link To This Post Posted: Jan/24/2010 at 5:11pm
That is a good question, In my previous post I did leave that part out.  (keep in mind this is what I have done, some may disagree) When we did our plugs we DID throw a coat of automotive primer on the plug before the wet sanding.  After some research I concluded (because there is different views about this, some ppl say that it isn't necessary and some feel that it is a critical step) we would go ahead and put the primer on so as to "seal" the part before wet sanding.  Another useful item to have is something called pin hole filler.  We picked it up at an actually composites store so other than that im not sure where you can get it.  what this stuff does is (as the name implies) fills in any pin holes. im sure that you have noticed that after sanding and blowing the piece off there a little pin holes throughout the part.  this stuff comes in tube form and there is no hardener that you need to mix it with.  it dries after you put it on the part within say....and hour? im not too sure.  you simply put some on a razor blade and scrape it in. great product.... then after you fill in all the pin holes you can primer the part and wetsand, wax, so on and so on...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motomike Quote  Post ReplyReply Direct Link To This Post Posted: Jan/24/2010 at 5:31pm
As for the different processes. I would stick with vacuum bagging.  The absolute best process if infusion, but for the parts that you are making, infusion would be a bit overkill.  as long as you make sure that all the material is wetted out and your fabrics (fibergalss, peal-o-ply (some call it differently), breather material, and bag) at correctly positioned, you'll be find.

As for the gains, infusion is the best because your part gets fully saturated with resin, there are no air bubble or pockets, and the minimal amount of resin is used to make your part (leading to lightest part).  Vacuum bagging is the second best because you usually get compression and no air bubble, full saturation, but if you wet the part out too much in the first place and then throw it into a bag with the breather material, some of that material will yes soak up the extra resin but it can only soak up so much before it also is fully saturated.  and of course lastly is wet lay-up, which is easiest, but the least effective to make the highest quality part. risks are things like too much resin (heavy part) and  air pockets or seperation between layers.  This is not to say that you can not make a great part by doing wet lay-up, you can, just take practice and skill to use the right amount of resin and lay-up procedures.  Wet lay-up is the easiest though... to say the least. 

One more item, if you have no one with vacuum bagging experience on your team, do you research AND think about doing some test pieces before jumping into the real thing.  try just doing a flat piece on a glass door, this will get you some practice and let you get use to the process... just a thought.  we were luck and had a composites guru help out my first year...learned a lot.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GT Steve Quote  Post ReplyReply Direct Link To This Post Posted: Jan/25/2010 at 1:21pm

Just to reinforce the point from another perspective, you definatly sound to be on the right track Andrew.

I got stuck with the composites at the end of the build year my senior year because we just couldn't get anyone else to spend the hours sanding the plug to prep for the mold.  We would typically "seal" the plug with a sandable primer prior to wax and mold-release, mainly because it appeared to give a smoother finish, which is what you need when you want that "shiny" look for the panels.
 
Good gel-coat application is critical as well, as well as your first coat of 'glass for the mold.  Make sure there are no air pockets between the gel coat and 'glass, or the vacuum bag will find them, and your finished part will look sh*tty (been there, done that), and you get to start over again.  We have also tried to skip the gel coat before (back before we knew better ('03-'04), and that ended with a butt-load of prep on the mold.  No fun.
 
Make sure you use the proper catalyst in your resin for the fiberglass mold that will etch the gel-coat and form a good bond. Very important!
 
 
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