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Thread: Foam Core Bodies

  1. #1
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    Foam Core Bodies

    I come from the Kitplane industry where weight is an issue in everything we build. One thing about kitplanes is a lot of the molded parts are either foam core or honeycomb material core.
    Often they use something like 3 layers of light weight glass a 1/4" core material and then 2 layers of glass on the inside. Of course you could vary the layers or weight of the glass depending on the need for the part. But 1 ply on each side would be minimal. The part is then vacuum bagged to form and keep light and often times oven cured but that isn't necessary if you use a good resin and its easy to post cure parts using black bags and sunlight.
    Anybody ever thought of doing this on a car body? It would make really light stiff and strong parts. You all have seen this in the flat panels on the LP640. But you can make some really crazy compounded shapes using the vacuum form method above. Im confident any car body part could be made this way.
    Just a thought.

  2. #2
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    Re: Foam Core Bodies

    hey byran, that is a good idea. am i been considering on using a meterial like this im my diablo panels. i already am using steel inlays where panels attach by bolt or which ever.

  3. #3
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    Re: Foam Core Bodies

    I think it would be really nice on quarter panels, doors and hoods. Easy too. The foam forms to shapes easily. If you need to you can score it to get it ot really lay into a tight curved area. The honeycomb stuff forms to anything really easily but its more expensive. Both materials are fuel and chemical resistant too. So yes you can even build fuel cells out of them. In fact my fuel tanks in my airplane are all composite.
    You could have some really nice light weight parts that are very strong.
    Another idea for inserts or hardpoints in the parts is a stuff called Phenolic. You can get it in all kinds of shapes and thicknesses. Its hard as a rock but lighter than steel and it bonds to epoxy and fiberglass because its similar material unlike metal. Metal doesn't bond well to epoxy parts. We use Phenolic for hardpoints in kitplanes to mount things like seatbelt bolts etc. Even some of the high load parts in the landing gear are supported by Phenolic blocks. You can get it in the same thickness to match the core material so it is flush once glassed in. We mix some chopped cotton material called Flox fiber into the epoxy when bonding high strenght peices into a part. The flox mixture is about as thick as mayo and when it dries its very very hard and strong. We also use a structual bonding agent called Hysol on parts that you never want to come apart again. Expensive but awesome stuff.


  4. #4

    Re: Foam Core Bodies

    its fine if you have the facilities
    we foam core 60% of the things we make, normally we spray a 2 part mould with a plactic and then inject foam
    on body panels we now use a cannon interwet system to spay a mixed layer of epoxy and glass then we spray on a 2 part epoxy based foam (using just a p100 grp gun) let it expand to around 4mm and then back it with grp mat again in epoxy
    when we tried it with pu foams and normal gelcoat/resin systems we couldnt get it to work
    to do this on a comercial basis we have invested a lot in equipment, we now only do it on our dealer supplied parts and race team items, it would double the cost of our kits for the conversion/builder market
    this takes it out of the abilities of a lot of induviduals and companies, for a personal use you can "homebrew" it and recitfy the problems from a comercial use any rework costs more than the cost of the part

  5. #5
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    Re: Foam Core Bodies

    I have built plenty of parts with foam cores in my garage and hangar. No special tools or facilities. If your molds are good enough to lay gelcoat and glass in them then they are good enough to lay gel coat, glass, 1/4" core material, then glass and vacuum bag. The honeycomb core lays into almost anyshape. Its pretty easy to even make a homebuilt vacuum bagging system. Probably to hard to do for a one piece body but for fenders, hoods and doors...not hard at all. We vacuum bag wings all the time and they fairly large parts. Wings also have curves in them them.
    I bet you could do a nice light carbon part buy using 2 plies carbon on the mold with a quarter inch core and 1 ply carbon on the inside of the part. If I had a mold I'd give it a try.

  6. #6
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    Re: Foam Core Bodies

    Quote Originally Posted by vonjet
    I have built plenty of parts with foam cores in my garage and hangar. No special tools or facilities. If your molds are good enough to lay gelcoat and glass in them then they are good enough to lay gel coat, glass, 1/4" core material, then glass and vacuum bag. The honeycomb core lays into almost anyshape. Its pretty easy to even make a homebuilt vacuum bagging system. Probably to hard to do for a one piece body but for fenders, hoods and doors...not hard at all. We vacuum bag wings all the time and they fairly large parts. Wings also have curves in them them.
    I bet you could do a nice light carbon part buy using 2 plies carbon on the mold with a quarter inch core and 1 ply carbon on the inside of the part. If I had a mold I'd give it a try.
    vonjet this is exactly the formula that was given me by a guy that used to make Indy car parts. Is coremat what you are talking about using or the material that is filled with air bubbles?

    Mike

  7. #7
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    Re: Foam Core Bodies

    the stuff Im talking using in car bodies is this:
    AHN 7800 is an Commercial Grade Nomex honeycomb particularly suited for use where resistance to corrosive attack and moisture are important. This material exhibits good strength characteristics and is fire resistant. It is available in a variety of cell sizes and densities to suit most purposes. Typical applications include lightweight non-structural bulkheads for ships, joiner panels, shelters, antennas, and auto body panels. This material also exhibits good thermal insulation properties and also has good dielectric properties. This honeycomb is easily machined, formed, and shaped and well suited to adhesive bonding.

    A 4x8 sheet of the 1/4" stuff is about $280 bucks. Its expensive but I think you would use a lot less glass and resin so you would probably break even using this as a core than trying to build up your parts. I dont think it would take more than 3 sheets to complete a LP640 body.
    I would love to make a carbon front fender of an LP640 with this stuff. I bet it would be light as heck, strong too. My problem is I dont know how to make molds. I can make a part but I've never made a mold.

  8. #8
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    Re: Foam Core Bodies

    Quote Originally Posted by turmite
    Quote Originally Posted by vonjet
    I have built plenty of parts with foam cores in my garage and hangar. No special tools or facilities. If your molds are good enough to lay gelcoat and glass in them then they are good enough to lay gel coat, glass, 1/4" core material, then glass and vacuum bag. The honeycomb core lays into almost anyshape. Its pretty easy to even make a homebuilt vacuum bagging system. Probably to hard to do for a one piece body but for fenders, hoods and doors...not hard at all. We vacuum bag wings all the time and they fairly large parts. Wings also have curves in them them.
    I bet you could do a nice light carbon part buy using 2 plies carbon on the mold with a quarter inch core and 1 ply carbon on the inside of the part. If I had a mold I'd give it a try.
    vonjet this is exactly the formula that was given me by a guy that used to make Indy car parts. Is coremat what you are talking about using or the material that is filled with air bubbles?

    Mike
    can you post some pics of the process its really interesting to learn or atleast to watch others do it, thanks

  9. #9
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    Re: Foam Core Bodies

    Actually you can by pass all that mess, bother and equipment if you use the RTM Lite system. You need to build the proper flange around your molds (Fairly easy process) and lay up a cover or lid. If you are making new molds you design them to use RTM Lite process right from the beginning. You can take old molds and adapt them over but it takes a little more skill and planning. However once you have the molds setup properly you can pop out perfect light weight finished panels as fast as you can re-fill the molds. We built our own vacumn pump and made our own mixer gun to inject with but this link has info on the process and equipment ... http://www.rtmcomposites.com/lrtm.html
    This is really the future for small production fiberglass and do it yourself-ers ( no mess, no odor ).


  10. #10
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    Re: Foam Core Bodies

    Just curious, how is that process any simpler or easier than vacuum bagging? It appears to very similar but you have to have proper molds to use it and large enclosures to cover your parts whereas vacuum bagging doesn't really require any special changes to your mold all your do is bag it and seal it. There is a lot of material that gets wasted in vacuum bagging but its inexpensive and for parts like ours that only need 1 finished side seems the easiest to me.

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