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Hot Rods Panel bonding floor pans

Discussion in 'The Hokey Ass Message Board' started by southcross2631, Feb 9, 2020.

  1. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,015


    I am in the process of putting floor pans in my 65 Comet wagon SEGA super stock project and am considering using panel bond instead of welding them in . I know it is not traditional but it sure would be a lot faster. Lighter than welding.
    I have used panel bond to install a new roof skin on a Chevy pickup before with great results.
    Has anyone tried it before or will I be the first ?
  2. I have not ever tried it , but I think it is a cool idea and should work fine.
    seb fontana likes this.
  3. catdad49
    Joined: Sep 25, 2005
    Posts: 4,400


    Will this have frame connectors? If so, I think it would be fine. Are you doing a build thread?
    OLSKOOL57 and Dino 64 like this.
  4. anthony myrick
    Joined: Sep 4, 2009
    Posts: 6,186

    anthony myrick

    After removing glued parts much easier than had they been welded, I’m not a fan.
    Yes the OEs bond parts today but now most are also riveted.
    No OE recommends full glue replacement of a previously welded part.
    But we’re talking about a 64 comet.
    I will add I passed on buying a started on project when the owner bragged about how the new panels were glued on.

  5. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,441

    from Berry, AL

    The floor is part of the unibody frame. I'd think you'd want them welded to make the structure stronger.
    6-bangertim, LWEL9226 and tractorguy like this.
  6. Budget36
    Joined: Nov 29, 2014
    Posts: 4,274


    I'd think he'd have the frame tied together for a race car.
    mad mikey and tractorguy like this.
  7. On a framed car I’d say go for it..that Comets a unibody...I’d weld em in...and I’m a 20 year 3M employee working in the Collison Industry..
    tractorguy likes this.
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 46,881


    Is the car fast enough to need a roll bar or cage?
  9. oldiron 440
    Joined: Dec 12, 2018
    Posts: 1,510

    oldiron 440

    The sheer strength is stronger for panel bonded panels then when welded. About the only thing than concerns me is improper use of the product or aplacation. I've been using the 3M panel bond since the late 90s and I've had vehicles hit in the aira that I've replaced a panel or two with adhesive with no problems with panel separation. Bonded panels are supposedly stronger than welded, the bond effects more surface than a weld plus it seals it at the same time.
    mad mikey and Hnstray like this.
  10. Properly done it will be stronger than welding. That's the key Properly Done. If you call an oem and say hey is it ok to panel bond floor pans in? On a car you sold 55 years ago? They will say no. Ask them if it is ok to put a 500 hp engine in a car that had a 90 hp six in it and go 135 mph in 1/4 mile ...also no. So you are in uncharted waters. The key is good prep.
    All bonding surfaces stripper of paint coarse ground and degreased.
    Use a good bonding adhesive...3m or Lords brand.
    Get the proper panel interfacial distance...3m puts beads in there you need to clamp it or use sheet metal screws.critical to the final strength.
    ...if you want bond a test sample using the same scrap and prep it screw it and send it out for a pull test. To convince yourself if needed.
    Follow the directions from 3M or Lords.

    Do racing sanctioning bodies care if the floor was tacked in or glued? Check the rule book.

    Not accusing anyone, but some welders think they are better than they are, I've seen some "welds" pull right apart. Definitely I'm no fan
    of butt welded floors. Just one guys opinion.
    oldiron 440 and Hnstray like this.
  11. You have heard from a manufacturer of an adhesive who recommends against it. I work for a company that manufacturers adhesives as well and agree on a uni body car it is not a good idea.

    Sent from my SM-G950W using The H.A.M.B. mobile app
  12. Pats55
    Joined: Apr 29, 2013
    Posts: 415

    from NJ

    You could use a combination of both panel adhesive and weld around the body mounts and any other area that would be stressed.

    Have any of you ever welded a paint can together? Like POR- KBS or Mastercoat. The resin used in gorilla glue is the resin use in these paints. So after you're done glueing and welding Apply two coats of the aluminum pigmented formula and that will glue the crap out of everything.
  13. BigChief
    Joined: Jan 14, 2003
    Posts: 2,079


    I've used panel adhesive alot. Door skins, quarter panels, roof and trunk/ hood skins....yes, all day. Floor pans on a full frame car? Go for it. Floors on a unibody car....I'd weld them in correctly.

    Sent from my SM-G950U using The H.A.M.B. mobile app
    tractorguy and Hollywood-East like this.
  14. Mig welding near panel adhesive melts it...a resistance spot welder is fine...chances are the hobbyist doesn’t have a resistance spot welder..
    dan31 likes this.
  15. 1ton
    Joined: Dec 3, 2010
    Posts: 399


    What about heat. On a hot summer day, the underside of cars get pretty warm. Can the adhesive handle it?
    Maybe the flexseal guy could put a screen door on the bottom of his car. After all, it worked on his boat.
  16. Other idea is to do ALL the prep work yourself .....drilling out spot welds grinding surfaces, fitting the new floors in , then have a pro welder come in and do the welds. Ask how he might bench test a spot weld. Lots of welders do side jobs for reasonable $$$. He can stop by in his work truck after work. I will admit I did a partial floor on a full frame car not the same as what you are doing. Chrysler glues the roof on the new minivan no welds at all but that is done under controlled conditions on new metal. Other thing I read was Ford used to pull every 25th Crown Vic body off the assembly line and do destructive strength tests on the welds. That to me speaks volumes about The variability of weld strength even under ideal conditions.
  17. Hackerbilt
    Joined: Aug 13, 2001
    Posts: 6,244


    Anyone suggesting this is a good idea is forgetting a very important part to the story.
    Any new vehicle that has a bonded panel is using it in an area designed for that application.
    Once you start gluing where welding was originally used, YOU are the one responsible for what you get...good or bad.
    Better be damn sure of what you are doing.
    Don't go inventing ways to use decent products in ways unintended.

    I work in the collision repair industry...and I've seen bonded panels, factory installed panels, delaminate in hits and roll over situations.
    Old cars have half the internal structure of the new cars so outer panels (inc floors) are under constant flex forces as the vehicle is driven. Those glue joints are gonna be working for their living!

    Do yourself a favor and weld those floors in place...
  18. saltflats
    Joined: Aug 14, 2007
    Posts: 10,315

    from Missouri

    If you are building a race car and you only need the pans to keep your feet in the car I would say you will be fine.
    mad mikey likes this.
  19. Read the 3M adhesive instructions.
  20. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,015


    The car will be tied together. it will have sub frame connectors and a roll bar. I was worried about body flex breaking the bond. Like I said I have used panel bond before and know about prep and I figured if I used the panel bond and then self tappers to clamp it in place while the chemicals setup I would be fine.
    I will probably just weld them . Just trying to save time getting ready for the season.
    milwscruffy, catdad49 and mad mikey like this.
  21. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,031


    Unibody body design has come a long way since 65. Back then, the design was a lot less structurally sound then the more modern versions are. I sure wouldn't want to take a chance of reducing the structural integrity of that 65 unibody structure in any way. I'd weld in the floor pans.

    In my past, I've been involved with field testing unibody dirt track race cars with a much better cage then I suspect your drag car will have. I've seen the distortion of unibody floor pans in cars with great roll cages including forward and rearward support bars. that have been stressed in crashes. I wouldn't want to trust all that stress with a glued in pan.
    It makes me feel much better to hear you have decided to weld in your floor pans. Gene
  22. coilover
    Joined: Apr 19, 2007
    Posts: 616

    from Texas

    Airliners and super sonic planes are glued. They go from below zero temp at altitude to 100 plus temp on a runway repeatedly and flex a bunch on a hard landing. I bonded the roof insert on a 30 Model A sedan on a factory A frame six years ago that is driven regularly and has no seam issues. Model A frames flex a bunch. The bonding was done in one day with zero warping and no weld grinding to create even more heat. When it comes to panel replacement my mig or tig are just going to sit in the corner and gather dust. What part of "bonding is stronger than weld" is not understood. Bonds done right have no chance of water or dirt getting into the joint.

    1967 Mustang Convertible, a unibody car, with rusted panels removed
    mustang conv 003.JPG mustang conv 001.JPG

    Finished car with no welds. If it crashes into your welded one it will wipe it out.
    Hnstray likes this.
  23. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,609

    seb fontana
    from ct

    ^^^HOLY CRAP!!^^^ What a start and what a finish..
  24. anthony myrick
    Joined: Sep 4, 2009
    Posts: 6,186

    anthony myrick

    Build one like that and crash test it.
    It won’t outperform a welded car.
    It will at best perform the same.
    I have yet to see a manufacturer recommend a totally glued in structural part, not even the glue manufacturer.
    By definition, every panel welded to a unibody is structural.
    lots of shops totally glue in panels, one lost a multi million dollar lawsuit over gluing in a roof
    I have used adhesives on panel replacement like roofs but not 100% bonded, no OE has recommended a total glue in process that I have seen as of yet. The OE process generally say to weld in the glass pinchweld areas as normal and spot welded over the A post. The adhesive was only used in the area above the doors.
    Plastic and SMC panels are different being that the shear strength of those panels is low and those panels are generally non structural skins. OEs use either a weld bond or rivet bond method with adhesives. BMW has a bond method for rails that uses a special made sleeve to create a laminated bond along with a mechanical fastener. GM has a bond in frame rail repair that utilizes special rivets. OEs are using fewer welds but changed to a mechanical fastener along with adhesives.
    I have had to re-do repairs from other shops that used glues, ripped of quarter panels with a hammer. A poor welder is usually a poor panel bonder
    7AA0CEA8-D719-4D11-BADC-E2111BE90AFC.jpeg C94BEF71-B0CA-49C3-AD16-D20AD703DE18.jpeg
    According to this, 3m doesn’t recommend their product be used for panel replacement
    Last edited: Feb 10, 2020
  25. If that mustang doesn’t have any welding or mechanical fasteners helping the adhesive in the event of a collision it’s going to be a sad day.

    Adhesives have very low shear strength, that’s why the OEMs use rivets or resistance spot welds along side adhesives.

    Sent from my iPhone using H.A.M.B.
    anthony myrick likes this.

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