Fiberglass door

[Gregory Walter]

I know little or nothing about fiberglass or boat building and could use some assistance. I am building a fiberglass kit car. A replica of a 1954 Mercedes Gullwing. I have been provided with both an outer and an inner door skin made of fiberglass. I would like to make the door as structurally stiff as possible. I had thought of building an aluminum tube skeleton when someone suggested a honeycome composite as used in boat building. Can someone suggest what might be a good material. Also, how would I go about "fiiting" the core. Do I somehow carve it until it fits snug inside both halfs then use a resin to seal it all together. I am sorry if this seems like a stupid question to you guys but I am trying to learn and I want to do the job right the first time.

[marshmat]

Honeycomb and foam cores are usually laminated between the skins as the part is being built. They are only strong if they are in full contact with both skins everywhere. Unfortunately you can't carve one to fit between two rigid panels. You might be able, though, to find a liquid foam that can be molded securely between them... I don't know of one off the top of my head though.

[Ssor]

Perhaps you can align the two skins and fill the space with canned foam. But there you must be very careful because it expands with considerable force. Also you have the consideration of the internal hardware for the window and latch. Have you researched the details from the kits supplier for hints and instructions? Also there must be a forum for kit car builders that will have addressed this very problem.

[nero]

Foam from a can will not work. It needs to have a large free surface area or it will develop large bubles (voids) that take a long time to cure. This comes from direct experience trying to fill pipe and steel profiles with the stuff.

Look at U.S.composites web site. They have several densities of PU A/B foam.

If you use a solid foam then think about fitting and bonding strips. This way you can work the contact points in a controlable fashion. You could even add some fiberglass cloth inbetween some of the strips.

Bond the foam with epoxy and some filler. perhaps silica power. the pros can provide more info on this.

Filling the voids in cars might make them quieter?

cheers

[tja]

I would go with your original idea of putting an aluminum structure simular to what is in most modern cars. M

[tja]

I messed up and not all of my post got on. So here is the rest. Mount the inner skin to the body and install the door latch. Then install an aluminum barrior to the inner skin. With the door still latched dry fit the outer skin to match up with the contours of the door opening. Once you are satisfied with the fit bond the outer skin to the inner with the door latched in place. Hope this helps, good luck.

[rxcomposite]

Stiffness must radiate from the greatest stress which in this case is the hinge location.

First try doubling the area where the hinges will be with aircraft grade plywood.

Thickness adds stifness, so add foam, PVC, Syntactic, or spray, carve to shape or taper, then add a couple of layers of glass, woven roving type variety. in the hinge side, add more layers.

For side inpact protection, aluminum channels of the "top hat" form will be effective. Tack it then glass over with two to three layers of cloth.