Is it necessary to use a fibreglass mold?

[arunmenon]

Hi. We are a first year team and we are running a bit short on budget. So we will be using fiberglass to make the bodywork. So, I was thinking why i should make a mold first and then make the part inside it with the releasing being troublesome. Instead, can i use the mold as the part itself after applying a gel coat layer to smoothen the outer surface?

Please post your suggestions...

[,4lex S.]

Using your mould as final bodywork will do one of two things.
1) Give it a really poor surface finish, or
2) Result in a very heavy final structure

Now, it is up to you what is acceptable weight wise, but you can take a quick look at the effect of weight with Optimum G's lap simulator (Optimum Lap). It is probably less significant than getting the car done.

If I was in your situation, I would look at aircraft fabric for the side panels, and focus on building a good male plug, female mould, and final part for the nose cone.

Aircraft fabric is this stuff (http://www.aircraftspruce.ca/catalog/cmpages/peelply3.php) I think. We have a bunch of old stuff laying around, so I am not sure. You basically epoxy it to your frame rails and heat shrink it to a tight fit. It can look good.

[Dunk Mckay]

If you do use fibreglass make sure it's woven, not just matte.

[AxelRipper]

If you want to be even less costly (and simpler) go with aluminum. Its surprisingly light in thin sheet form relative to even carbon, and can be done without molds.

[jlangholzj]

Originally posted by ,4lex S.:
Using your mould as final bodywork will do one of two things.
1) Give it a really poor surface finish, or
2) Result in a very heavy final structure

Now, it is up to you what is acceptable weight wise, but you can take a quick look at the effect of weight with Optimum G's lap simulator (Optimum Lap). It is probably less significant than getting the car done.

If I was in your situation, I would look at aircraft fabric for the side panels, and focus on building a good male plug, female mould, and final part for the nose cone.

Aircraft fabric is this stuff (http://www.aircraftspruce.ca/catalog/cmpages/peelply3.php) I think. We have a bunch of old stuff laying around, so I am not sure. You basically epoxy it to your frame rails and heat shrink it to a tight fit. It can look good.

Go with this stuff instead:

Fabric (http://www.aircraftspruce.ca/menus/cs/polyfiber_fabric.html)

We've put that on a few cubs and a stearman, It doesn't get any better. Also if you look at the poly-fiber page on spruce they've got a practice kit and additional instructions/materials.

this was our '12 car with the fabric on and painted before final assy

http://sphotos-b.xx.fbcdn.net/hphotos-snc6/243353_10151130678309477_1299494674_o.jpg

[Charles Kaneb]

Covering the nose with a nylon or polyester "jacket" with a zipper anchored in a few places to the steel always fails at our design reviews for being "too janky for a team with Texas A&M's resources" - but it's light and easy to do. You'll have to attach some rollcage foam in a couple places to meet minimum-radius requirements.

[arunmenon]

Originally posted by ,4lex S.:
Using your mould as final bodywork will do one of two things.
1) Give it a really poor surface finish, or
2) Result in a very heavy final structure

Now, it is up to you what is acceptable weight wise, but you can take a quick look at the effect of weight with Optimum G's lap simulator (Optimum Lap). It is probably less significant than getting the car done.

If I was in your situation, I would look at aircraft fabric for the side panels, and focus on building a good male plug, female mould, and final part for the nose cone.

Aircraft fabric is this stuff (http://www.aircraftspruce.ca/catalog/cmpages/peelply3.php) I think. We have a bunch of old stuff laying around, so I am not sure. You basically epoxy it to your frame rails and heat shrink it to a tight fit. It can look good.

I was thinking i can make a male mould and use that as the final part. Then the exterior would be smooth right?

And the final structure can be made such that there is enough strength to keep it intact throughout the run and with more support at the points where fasteners will be present. So i hope it wont be too heavy.

What is your opinion?

[arunmenon]

Originally posted by AxelRipper:
If you want to be even less costly (and simpler) go with aluminum. Its surprisingly light in thin sheet form relative to even carbon, and can be done without molds.

The design we came up with after a series of analysis is a fairly complicated one. The curves will be difficult to make with aluminium. And it wont look as good as fibreglass right?

[arunmenon]

Originally posted by jlangholzj:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ,4lex S.:
Using your mould as final bodywork will do one of two things.
1) Give it a really poor surface finish, or
2) Result in a very heavy final structure

Now, it is up to you what is acceptable weight wise, but you can take a quick look at the effect of weight with Optimum G's lap simulator (Optimum Lap). It is probably less significant than getting the car done.

If I was in your situation, I would look at aircraft fabric for the side panels, and focus on building a good male plug, female mould, and final part for the nose cone.

Aircraft fabric is this stuff (http://www.aircraftspruce.ca/catalog/cmpages/peelply3.php) I think. We have a bunch of old stuff laying around, so I am not sure. You basically epoxy it to your frame rails and heat shrink it to a tight fit. It can look good.

Go with this stuff instead:

Fabric (http://www.aircraftspruce.ca/menus/cs/polyfiber_fabric.html)

We've put that on a few cubs and a stearman, It doesn't get any better. Also if you look at the poly-fiber page on spruce they've got a practice kit and additional instructions/materials.

this was our '12 car with the fabric on and painted before final assy

http://sphotos-b.xx.fbcdn.net/hphotos-snc6/243353_10151130678309477_1299494674_o.jpg </div></BLOCKQUOTE>

I dont think i will be able to make our design with aircraft fibre. Its a bit complex

[jlangholzj]

So bodywork as in a nose, sidepod or what? You're going to be able to make just about any shape with aircraft fabric.

[Charles Kaneb]

Then you need a different design!

If it isn't easy to make it has no place on an FSAE car.

This year, our car HAS to meet the 8/8 rule - every component fabricated and installed by 8 people in 8 weeks. We've had three cars in a row come in late/over budget and it's hurt testing time and forced us to rob Peter to pay Paul, shortchanging our racing and capital improvement budget.

[arunmenon]

I was thinking i can make a male mould and use that as the final part. Then the exterior would be smooth right?

And the final structure can be made such that there is enough strength to keep it intact throughout the run and with more support at the points where fasteners will be present. So i hope it wont be too heavy.

What is your opinion?

[,4lex S.]

It would probably help if you did up a quick sketch. Bodywork should easily support itself under most FSAE conditions, but we don't know what else you have hanging off of it, or what your operating conditions are (if you are doing supra, how fast do you guys manage to get going on the full circuit?).

If you are just going to make a male mould out of thin air, I am not exactly seeing how you would do it. I am guessing you mean you would make a plug (in the desired shape of your nosecone), and layup fibreglass on top of it? In general, to get a good surface finish you need either a female mould, or appropriate use of filler.

Filler is heavy, and female moulds take a long time to make well.

[JWard]

I second the Ali solution. Monash did it for their 11 and 12 cars and I remember a figure of 2kg bouncing around last year. That was their first attempt of using cut sheet ali, so I'm sure they worked out ways of reducing this further.... Worth an email? (Don't hope for a quick and detailed answer - FSAE A is in full swing)

[AxelRipper]

Originally posted by arunmenon:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
If you want to be even less costly (and simpler) go with aluminum. Its surprisingly light in thin sheet form relative to even carbon, and can be done without molds.

The design we came up with after a series of analysis is a fairly complicated one. The curves will be difficult to make with aluminium. And it wont look as good as fibreglass right? </div></BLOCKQUOTE>

Well this all depends on what your skills are and what your definition of "good" is. I've seen some pretty shoddy looking fiberglass bodywork (unsanded chopped strand mat is not very pretty if not done right). One of our sponsors fell through this past year and didn't get our MDF bodywork moulds cut, so we had to make aluminum bodywork. One person in a weekend got them together, slap on a bit of bondo to cover the rivets, scuff the aluminum (a step I sadly screwed up on, so the paint hasn't weathered well), prime and paint.

Does it look as good as our original design was supposed to? Not exactly (but thats just my opinion... I was the one who designed the bodywork in CAD). Was it heavy? Well, the whole package was about 7-10 lbs, compared to 3-4 for the previous year's CF. Did it work? Damn right it did. Most people we talked to didn't believe that it was aluminum until we tapped it once and they heard the distinct *ping* that aluminum has (and FRP doesn't).

Also, the addendum to the cost report saved $500+.

http://sphotos-f.ak.fbcdn.net/hphotos-ak-prn1/51900_481831115181604_926471842_o.jpg

[arunmenon]

Originally posted by ,4lex S.:
It would probably help if you did up a quick sketch. Bodywork should easily support itself under most FSAE conditions, but we don't know what else you have hanging off of it, or what your operating conditions are (if you are doing supra, how fast do you guys manage to get going on the full circuit?).

If you are just going to make a male mould out of thin air, I am not exactly seeing how you would do it. I am guessing you mean you would make a plug (in the desired shape of your nosecone), and layup fibreglass on top of it? In general, to get a good surface finish you need either a female mould, or appropriate use of filler.

Filler is heavy, and female moulds take a long time to make well.

i meant that i will be making a cavity of the required shape in foam and lay fiberglass inside it, after applying proper mold release and gel coat. So i guessed it should provide a fair appearance.

[arunmenon]

Originally posted by AxelRipper:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by arunmenon:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
If you want to be even less costly (and simpler) go with aluminum. Its surprisingly light in thin sheet form relative to even carbon, and can be done without molds.

The design we came up with after a series of analysis is a fairly complicated one. The curves will be difficult to make with aluminium. And it wont look as good as fibreglass right? </div></BLOCKQUOTE>

Well this all depends on what your skills are and what your definition of "good" is. I've seen some pretty shoddy looking fiberglass bodywork (unsanded chopped strand mat is not very pretty if not done right). One of our sponsors fell through this past year and didn't get our MDF bodywork moulds cut, so we had to make aluminum bodywork. One person in a weekend got them together, slap on a bit of bondo to cover the rivets, scuff the aluminum (a step I sadly screwed up on, so the paint hasn't weathered well), prime and paint.

Does it look as good as our original design was supposed to? Not exactly (but thats just my opinion... I was the one who designed the bodywork in CAD). Was it heavy? Well, the whole package was about 7-10 lbs, compared to 3-4 for the previous year's CF. Did it work? Damn right it did. Most people we talked to didn't believe that it was aluminum until we tapped it once and they heard the distinct *ping* that aluminum has (and FRP doesn't).

Also, the addendum to the cost report saved $500+.

http://sphotos-f.ak.fbcdn.net/hphotos-ak-prn1/51900_481831115181604_926471842_o.jpg </div></BLOCKQUOTE>

frankly, i didnt know aluminium could give such a good finish. i can consider it now. thank you :-)

[MCoach]

I can think of a different reason to go with the aluminum that I am hesitant to mention in this thread...

However, the ease of manufacturing and cost compared to composite bodywork is just mind blowing. That I will highly agree with.

Sometimes I wonder if teams use composites just because they've seen everyone else do it.