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57BLITZ
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Joined: June 12, 2012
Posts: 2385
Location: DEEK - U.S.A.
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 Posted: Sun Aug 14, 2016 5:49 pm Post subject: Mixing Steel & Fiberglass |
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Actually, I know steel and fiberglass do not like to play together!
After reading a bunch of info, and discovering that the expansion rates are different between those materials, and that solidly bonding them together will cause problems . . .
I am hoping I have a solution for my project . . . to add a gas-fill door to a fiberglass body . . .
Please give your thoughts/feedback/advice to my plan . . .
1. Remove gas door flap/hinge/latch/substructure from donor '69 VW Bug.
2. Drill out the spot welds in substructure (the inner portion that has the latch and door hinge) to remove it from the outer quarter panel skin.
3. Sand blast and epoxy prime (or powder-coat) the inner substructure to prevent rust formation.
4. Make cutout in the fiberglass body just slightly larger than the size of the gas door flap. Grind the inside of the body several inches around the cut-out to provide a nice, clean surface.
5. Adhere the substructure to the inside of the body with a flexible substance . . . like seam-sealer.
6. Coat the back side of the substructure's perimeter flange with the same seam-sealer, and allow to cure.
7. Add a couple layers of cloth/mat over the steel flange and out several inches onto the inside of the body . . . to "lock" the steel substructure to the body . . .
The perimeter of the steel substructure will be encapulsed in fiberglass inside the body . . . The outside of the body/gelcoat is completly undisturbed.
Since the steel is coated with seam-sealer on all the surfaces in contact with the fiberglass, there is not a solid bond between the two.
The gas door assembly will be firmly attached to the body while still allowing a tiny bit of flex to avoid stress/fractures/cracking in the fiberglass.
Will my plan work?
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didget69
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Joined: July 22, 2004
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Location: Raleigh, North Carolina
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Dale M.
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Joined: April 12, 2006
Posts: 20377
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sun Aug 14, 2016 7:26 pm Post subject: Re: Mixing Steel & Fiberglass |
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Get after market GAS door for PU or some other zippy car...
This door is by AMP Research for "M" class Mercedes but the is probably 2 dozen style doors that will fit your needs...
http://images.lmgtfy.com/?q=fuel+door
Mine is surface mounted, but the have been other who used same door concept and flush mounted them...
Dale
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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57BLITZ
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Joined: June 12, 2012
Posts: 2385
Location: DEEK - U.S.A.
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| Posted: Mon Aug 15, 2016 10:35 am Post subject: Re: Mixing Steel & Fiberglass |
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| didget69 wrote: |
| I've used the 3M & SEM products for bonding steel to fiberglass, but it will eventually show cracks depending on how it's installed. |
Thanks for posting those links . . . I actually read the one on Pro-Touring forum before I started this thread.
Cracking . . . that's what I want to avoid . . . that is why I do NOT want to securely bond the steel to the fiber glass. It will be behind the fiberglass, not exposed, and simply serve the propose of hinge mounting, a latch point, and door-stop.
I DO want there to be some compliance between the 'glass body and the steel to allow for expansion of the dissimilar materials. I do not want the steel frame to cause stress to build around the cut-out in the fiberglass.
The fiberglass that I will lay-up around the perimeter of the steel will encapsulate it . . . like the way a "cage nut" will stay in place, so will the steel frame when surrounded with fiberglass.
The seam-sealer, or rubberized epoxy, or whatever I use will reduce movement while allowing a slight amount of movement . . . the same way your motor mounts allow the engine to move and at the same time, limit the movement.
That's why I to use want something to fill the gap between the fiberglass and the steel that will not necessarily bond them together securely, but will fill the seam between the two surfaces, be slightly flexible, and be paintable.
Make sense or no?
| Dale M. wrote: |
| Mine is surface mounted, but the have been other who used same door concept and flush mounted them... |
Thanks Dale!
I saw a thread here where someone used a Dremel to remove enough gelcoat/fiberglass to set one of those flush . . . I turned out very nice!
ALSO . . . I may not have mentioned to ya before Dale . . . I think your buggy is Super Bitchen!!! I really dig the gold spokes on the Americans!
If I were to copy a buggy, it would be yours!!!
I am going a slightly different route with mine, so I want to incorporate that Bug gas door.
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AMAC1680
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Joined: April 09, 2015
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Location: Jacksonville Fl/Mantoloking NJ
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| Posted: Mon Aug 15, 2016 11:25 am Post subject: Re: Mixing Steel & Fiberglass |
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In the marine world we have been attaching metal to glass for years and there are simple ways to avoid the stress cracks.
If it were me I'd use 3m 4200 to attach the cover to the hood then just use small screws for aesthetic value and be done with it. The 4200 will flex just enough to keep the stress cracks away. same way I'd do a metal hatch to glass on a boat.
Again just how I'd do it.
AMAC
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57BLITZ
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| Posted: Mon Aug 15, 2016 1:00 pm Post subject: Re: Mixing Steel & Fiberglass |
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| AMAC1680 wrote: |
| . . . If it were me I'd use 3m 4200 to attach the cover to the hood then just use small screws for aesthetic value . . . |
Thanks AMAC!
That might be just the ticket . . . 3M 4200!
From the 3M website http://multimedia.3m.com/mws/media/891179O/3m-mari...4200fc.pdf . . .
Features/Advantages
• Fast cure formula
• One component, moisture curing
• Allows for disassembly
• Bonds dissimilar materials
• Extended shelf life
• Adheres to a wide variety of substrates
• Non-sagging
• Permanently elastic
That sounds good to me!
From the same product info . . . a possible hick-up . . . "Extended exposure to chemicals ( . . . gasoline . . . ) may cause permanent softening of the sealant."
That's why I think I will lay-up some 'glass around the perimeter of the metal frame after it is "glued" in place.
Again, it will fit to the inside of the body . . . nothing will show on the outside . . . only the flap door!
BTW . . . No screws . . . that is one of the reasons I am going to use the '69 Beetle gas flap!
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hillmotorsports
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Joined: December 27, 2014
Posts: 432
Location: Morrisburg, Ontario, Canada
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| Posted: Mon Aug 15, 2016 2:07 pm Post subject: Re: Mixing Steel & Fiberglass |
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57Blitz:
Not sure why you insist on reinventing the wheel here.......
You asked for advice yet want to ignore what you got for nothing from experts and continue down your own unproven road.
Good luck.
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57BLITZ
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Location: DEEK - U.S.A.
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| Posted: Mon Aug 15, 2016 2:30 pm Post subject: Re: Mixing Steel & Fiberglass |
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| hillmotorsports wrote: |
57Blitz:
Good luck. |
Thank you!
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fabricator john
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Joined: October 09, 2009
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Location: manassas va. now Venice Fl.
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| Posted: Mon Aug 15, 2016 4:10 pm Post subject: Re: Mixing Steel & Fiberglass |
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all that work and money for somthing engineered to fail. the boat stuff is the same ( basically but not actually) as siliconing it in , no way to finish paint cant stick to the "glue" line, make a mold from the vw lid you have and make one from fiberglass,,,,, you got a buggy you will be learning glass work before your done anyways.... my 2c
fabricator john |
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AMAC1680
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Location: Jacksonville Fl/Mantoloking NJ
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| Posted: Mon Aug 15, 2016 4:54 pm Post subject: Re: Mixing Steel & Fiberglass |
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No need to paint the 4200 as it all will be out of site, no glue line if applied correctly. Engineered to fail is an interesting term. Engineered with a life span is more like it. Most fiberglass repairs, spray patches etc also have a life span.
Making a plug to create a one off glass piece seems like the long way around. IMO.
AMAC
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57BLITZ
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Location: DEEK - U.S.A.
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| Posted: Mon Aug 15, 2016 5:29 pm Post subject: Re: Mixing Steel & Fiberglass |
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| AMAC1680 wrote: |
| Making a plug to create a one off glass piece seems like the long way around. |
I did actually consider doing that, but . . . that would preclude me from using the VW cable release . . . it passes through the sheet metal . . . the fiberglass would need to be less than .045" thick for the latch to catch the door . . . NOT quite the recipe for longevity!
I have been reading reviews on the 3M 4200 . . . EVERYTHING has been positive with the exception of a few complaints that once the original seal of the tube is broken, the shelf-life of the remaining 4200 is reduced to a couple of days . . . Not a problem for me!
As you mention, the seam will be behind the gas door . . . NONE of the adhesive will be on the outside of the body!
Thanks for the help AMAC!
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