looking for advice on materials and design for car projects; doors, front nose

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#1

i will come back and edit this post; i have little time to do so today.

i will first outline the goals and limitations to give you a better understanding where the compromises will be made.

my concerns are mostly weight with consideration to cost. meaning getting the lightest finished product with what i deem reasonable money. when choosing a core material i am trying to consider its propensity to absorb resin. the parts will likely be fiberglass for cost reasons unless cf has come down in cost in the last year or so, initial check appears it has not. i also accept i lack the skills to utilize the extra potential that cf allows. having said all that if there is some material that you feel is a better for my aforementioned needs than i am all ears.

a little background: i have made a couple panels so far but my method is rather neolithic; overlay type - a couple layers of fg then i separate the piece and add a foam carcass than apply one layer fg over the foam. this has worked so far but the next two projects i want to do are more involved and weight savings take a huge priority. hence the research about core materials outlined shortly.

i will also ask for advice about structural epoxy as my last recommendation i adopted was was to flimsy around 90 degrees and warmer. i would imagine it was more resilient to cracking/chipping but this is not a realistic concern to justify sacrificing such structure a proper resin can add to the system.

here is how i plan to make the doors with functional lexan windows. i will put release agent onto the current outside door surface. wetup the door with epoxy you recommend. than add a layer of fg and add my already cut/trimmed/maybe molded core material and than add another layer of fg over the top. i will place into a vacuum bag and use peel ply with mate to help absorb excess resin. i understand when using an overlay method some dimensions become skewed. after this part is cured i will form the inner structure. same layers unless otherwise advised. i will later reinforce the areas where window lexan window will ride up and down. i plan on only having 2 positions(up or completely down) for the window so i will only have tracks near the top and limiters for window movement; weight being the concern. i am still looking into either using 1/8 polycarbonate with a metal frame to contour to car or using 3/16-1/4 and forming it to contours of normal window. i suspect despite being at least 2x as thick as the 1/8 material the overall weight will be similar. the thicker material creates a cleaner finished product without the metal frame that hides the lightness design some.
edit: i spent sometime reviewing material thickness and believe a formed piece of 3/16" is all i will need for the front windows to prevent any vibration from wind rushing over them at speed.
i also will put a C type aluminum channel where the door frame accommodates the side view mirror. this c channel will help hold the contour of the formed polycarbonate on the most important edge to the wind; leading. i will upload a image later for critique.

the nose clip i will highlight those designs later but to be honest i view that project as easy mode when compared to the doors with functional windows.

back to the core material dilemma; here is the research so far.

the core material i am favoring at this moment is a product called aero-mat. it is a 2mm thick core material with raised hexagonal shapes made out of foam type product to give the thickness. there is a type of fabric like material that connects the hexagonal shaped foam to aid in the bonding of the outer skins and resin. it contours well and is very lightweight. so far i prefer this material to a standard fabric core because its resilience to absorbing extra resin -> thus reducing weight. i however would like something a little thicker 3m =/

links to aero-mat
http://www.acp-composites.com/home.php?cat=256
less expensive source
http://www.cstsales.com/flexible_core.html

similar product called Coremat: Lantor Soric XF (trying to find smaller quantities of it) the manufacturer appears to be located in germany and i have sent an email to them. i will update the thread with their response. seems like the lantor soric name may be same as the 3d product line from the manufacturer’s website? xps-30 looks very appealing; i like that i can get a 3mm thick core vs. the 2mm listed above. waiting on availability of material and price for small qualities.
https://docs.google.com/viewer?url=h...foEn10_web.pdf
http://carbonsales.com/Coremat-Infusion/?page=2 (source for rolls of it =/)

another link (has me thinking the lantor soric and xps-30 are different products)
http://www.amtcomposites.co.za/ac_lantor.html

finally found a link lantor soric xf(3mm ~19$ per yard)
http://www.fibreglast.com/product/Lantor_Soric_XF_1409/
manufacturer’s website? http://www.lantor.nl/index.php/id_st...599/soric.html
soric lrc material properties - http://www.cgcomposites.com.au/produ...rc%2073141.pdf

alternative core materials found here.
http://www.fiberglasssupply.com/Prod...materials.html

Divinycell - http://www.fiberglasssupply.com/Prod...materials.html
corecell - http://www.yachtsurvey.com/ATC_Core-Cell.htm - http://www.gurit.com/core-materials-marine.aspx
nida-core - http://nida-core.com/english/fusion.htm - http://nida-core.com/english/

i am only in the research stage and my mind is open to suggestions. what say you?

#2

do you know how much money it takes to properly form polycarbonate without… breaking, crazing, or ruining it???

if you are worried about fiberglass vs carbon fiber prices forming lexan to work like you want it to will be a miracle…

also the lexan window kits you can buy… dont always fit oem…and the contour is sometimes off. and if you plan on trimming it by hand every piece will be a custom job with hours of trim and fit.

this is coming from a guy who made custom aircraft canopy mock ups out of thermoform polycarbonate.

your looking in all the right spots. but unless you have a good amount of money to invest in this project the final product might be less than you expect.

why not duplicate a door completely and use the steel tracks and frames that come in an oem door. many of the parts are easy to get and for times sake you might be able to find a vendor that can produce a oem fit window that might work.

dont re engineer the wheel… roll with it.

my two cents.

#3

thank you for expressing your concerns based on your experience.

yes, i am familiar with the process of forming polycarbonate. i found some literature that goes into details about the temperatures at which the material can be formed as well as suggested protocol to reduce chances of compromised pieces; i.e. bubbles trapped within material.

the windows will be the first piece i make as the doors will be designed around the weight and design of the windows. the cost is ~ 60 dollars per window. depending upon what i learn from my attempts i can justify up to 2 failed attempts before i wave the white flag. if the first attempt proves the task to be to difficult for my skills and resources i will abandon after first attempt.

my contingency plan; is to use thinner polycarbonate material with a metal boarder that will hold the minor contour of the window.

regardless of the outcome i will post back to this thread with an objective assessment how my polycarbonate forming experience went.

anyone have any advice on epoxy and/or the core material?

#4

Have you made a part out of a two part mold before?
I don’t think using the actual door as a male mold like you mention will work at all.

“i will put release agent onto the current outside door surface. wetup the door with epoxy you recommend. than add a layer of fg and add my already cut/trimmed/maybe molded core material and than add another layer of fg over the top. i will place into a vacuum bag and use peel ply with mate to help absorb excess resin”

How do you plan on lining up the inner and out halves of the doors after you make them? You would also end up with a door that is probably too thick/big to fit on the car. Where in CT are you?

From experince, I think you are jumping in over your head. Ive done the same, the first project I tried to tackle was making a bumper. I ended up wasting a whole bunch of materials…

#5

thank you for expressing your concerns. this is why i made the thread. although the issues you have brought out, up to this time, have been accounted for, i will spend additional time thinking it over.

at this time, i have not made a part with a 2 piece mold.

caveat: i am currently away from my car so details will be off but ill recall them as best i can.

there is about 3/4" boarder flange around the inner door frame an outside panel. the inner door frame does not protrude into the cabin space. it rests against a piece of weather stripping; this will likely be removed as well. because i am keeping the door hinges on the car where they have been there whole life i will have to adjust the inner door frame over the thickness i have made it to keep similar gaps as from factory; i figure inner door frame to be about 7/32" thick. what this does to the door latching mechanism on the other side is much easier to account for; remember i have about 3/4" space that can be used.

this is what i have in mind at this time and pending other concerns that are brought up and the actual measurements that will tell me how possible the aforementioned plan is, i may have to consider alternative methods.

when i return home i will likely reside where i grew up, northeastern connecticut; specifically brooklyn and voluntown areas.