Ex 80s body guy back at it on a Kit Car

[rbranst]

Hey guys and gals. I used to do bodywork back in the 80's, have a 2 year vocational cert. My real calling was computers but I have kept cars as a hobby.
I am building a Cobra kit and I have a few questions. I am building up body sills for the doors to accurately replicate an original in way my kit (Hurricane) doesn't.
To do the work I am doing, I need to build a 3/4" by 3/4" sill around the door opening. Here is what I have done:
Formed the basic shapes with corrugated plastic, fastened in place temporarily and lined with aluminum foil.
My question is:
1. What is suitable to use to build up this area? Chopped mat (what oz) or Everglass Tiger Hair or some combo.

Since this will be about 3/4x3/4 I need something fairly durable in case someone steps on it.

What are your thoughts on how to accomplish and what product to use?

[Len]

Hey guys and gals. I used to do bodywork back in the 80's, have a 2 year vocational cert. My real calling was computers but I have kept cars as a hobby.
I am building a Cobra kit and I have a few questions. I am building up body sills for the doors to accurately replicate an original in way my kit (Hurricane) doesn't.
To do the work I am doing, I need to build a 3/4" by 3/4" sill around the door opening. Here is what I have done:
Formed the basic shapes with corrugated plastic, fastened in place temporarily and lined with aluminum foil.
My question is:
1. What is suitable to use to build up this area? Chopped mat (what oz) or Everglass Tiger Hair or some combo.

Since this will be about 3/4x3/4 I need something fairly durable in case someone steps on it.

What are your thoughts on how to accomplish and what product to use?

Welcome Aboard
I would probably do one of two things.

1. You could make the entire repair using short strand filler. You could have a 3/4" barrier on the outer edge then fill the area with the fiberglass filler
2. You could also use metal or wood around the edge then get the correct shape using the fiberglass filler.

Whatever you decide to do be sure to give the existing surface a good sanding with 36 or 40 grit before you apply the filler so that it bonds properly. Press your first coat of glass into the scratches.

[rbranst]

Thanks for the reply Len.
Are you saying you would use Long or Short Strand on the inside and then glass cloth over after forms are removed?
I am confused on where you are suggesting the filler goes, inside or outside. I think it might be pretty strong doing long strand in the form, then laminating with glass cloth, then a light filler for cosmetics

[Len]

Thanks for the reply Len.
Are you saying you would use Long or Short Strand on the inside and then glass cloth over after forms are removed?
I am confused on where you are suggesting the filler goes, inside or outside. I think it might be pretty strong doing long strand in the form, then laminating with glass cloth, then a light filler for cosmetics

OK let me get this clear for me. Are you saying that you're building on the jamb to close the gap between the door and the jamb?

[rbranst]

OK let me get this clear for me. Are you saying that you're building on the jamb to close the gap between the door and the jamb?

Its really more the jambs are fine, there are no gap issues, I am building more of a door sill inside the door.

Example of my car before I started this project and a REAL Cobrasill6.jpg20220607_201935576_iOS.jpg

[Len]

So you want to raise the inside jamb?

Jambs.jpg

[rbranst]

Yea that’s the area. On a real car they are about 3/4” thick and deep. On my car they don’t don’t 90 degree in. I’m trying to replicate that and I only have the outer edge to build off of .

[rbranst]

A608BC73-19D8-412A-9E0D-79463DD4B006.jpg

Here is where I started. Maybe it will make more sense.
Thanks for looking.
Ryan

[Bob K]

It sounds like you have a single straight flange instead of a flange with a 90 degree bend on the top. If it were me I’d get a length of 3/4” sheet metal angle long enough to be fit up as a single piece, then notch the vertical side at the bends with multiple cuts to allow you to fit it into place and keep close to the finished shape. Screw it to the car with self tapping screws through the car’s flange then cover it with the fiberglass filler that Len recommended and sand it to shape. Blend the filler into the fiberglass body. If you wanted to go even further to make it even more substantial you could use a 3/4 x 3/4” chanel shape instead of the 90 degree angle tnen fiberglass all three sides with the wild end going into the carpeting. Be sure to check the fit to be sure there is room for
fiberglass filler before you put the filler on.

Bob K

[Ronf]

If this were mine I would use a piece of 3/4 x 3/4 extrusion and weld or braze it to the 90 degree turn up on the existing bend if your substrate is either aluminum or steel. As the original Cobras were aluminum and if your is the same you will need to use aluminum extrusion and braze this on the bend. On these extrusions you will need to cut reliefs every few inches (or less) to allow for contours unless you have extensive sheet metal working tools such as a bead maker, planisher, etc.. Afterwards you will need to glue in a plywood backer for strength. If your kit is fiberglass, I would cut a piece of 5/8" plywood to match your opening and use fiberglass resin and cloth to complete the door gap. Make sure you have a way to anchor your plywood backing well so it does not separate from the existing bend. Start with a large piece of construction paper to outline your entire door opening and build off from there. Believe it or not this is not hard to accomplish. Just make sure you get a very accurate pattern with your construction paper so you have a good tight fit. What you do not show is how your door flange fits into this opening, so you need to provide pics for us to understand how inside door to sill gaps work. After you finish with fiberglass resin and weave/wove cloth, come back over that with either long or short strand fiber body filler to give it more strength. Follow this with a standard body filler, HB primer and finish with sealer, bc and clear.

[Len]

It sounds like you have a single straight flange instead of a flange with a 90 degree bend on the top. If it were me I’d get a length of 3/4” sheet metal angle long enough to be fit up as a single piece, then notch the vertical side at the bends with multiple cuts to allow you to fit it into place and keep close to the finished shape. Screw it to the car with self tapping screws through the car’s flange then cover it with the fiberglass filler that Len recommended and sand it to shape. Blend the filler into the fiberglass body. If you wanted to go even further to make it even more substantial you could use a 3/4 x 3/4” chanel shape instead of the 90 degree angle tnen fiberglass all three sides with the wild end going into the carpeting. Be sure to check the fit to be sure there is room for
fiberglass filler before you put the filler on.

Bob K

Exactly what I would do and I'd use The smallest EZ EDGE (C) to help make edge.

LINK

[Ronf]

Exactly what I would do and I'd use The smallest EZ EDGE (C) to help make edge.

LINK

Yes, this is the way to go.

[bmarler]

the only thing i'd like to contribute to the conversation is that if you're going to glass it, use epoxy for laminating and glass cloth for strength. be careful choosing the epoxy so you don't have to worry about the amine blush that needs to be washed off so the next layer adheres properly. i used to always use west system epoxy as it's very high quality, but the hassle of washing the amine blush made me look for alternatives. i've since switched to system three silvertip epoxy so i can build it up without worry.
pay attention to all the edges and corners to be sure there's a rounded edge, fiberglass doesn't like hard edges. and also extend the ends into the existing structure so there's no "hard" end or you'll get stress cracks.
i'm not clear about whether or not you are hoping to leave the "form" in place or remove it after the glass structure is laid up? but if it's going to stay, i might look at using a closed cell foam as it's lightweight and easy to shape.
this is assuming the shell you're working with is a fiberglass one...

https://www.systemthree.com/products...ng-epoxy-resin

[bmarler]

look here for help deciding what cloth will work best.
https://fiberglasswarehouse.com/blog...fiberglass-mat

also here, i buy from these guys a lot: https://www.fibreglast.com/product/t...earning_Center

[Ronf]

the only thing i'd like to contribute to the conversation is that if you're going to glass it, use epoxy for laminating and glass cloth for strength. be careful choosing the epoxy so you don't have to worry about the amine blush that needs to be washed off so the next layer adheres properly. i used to always use west system epoxy as it's very high quality, but the hassle of washing the amine blush made me look for alternatives. i've since switched to system three silvertip epoxy so i can build it up without worry.
pay attention to all the edges and corners to be sure there's a rounded edge, fiberglass doesn't like hard edges. and also extend the ends into the existing structure so there's no "hard" end or you'll get stress cracks.
i'm not clear about whether or not you are hoping to leave the "form" in place or remove it after the glass structure is laid up? but if it's going to stay, i might look at using a closed cell foam as it's lightweight and easy to shape.
this is assuming the shell you're working with is a fiberglass one...

https://www.systemthree.com/products...ng-epoxy-resin

Brian,

You bring up some great points. For instance, I advised using a plywood backer for both strength, as he is worried about people entering the car and putting excess weight in that area, and to give the upholster a surface for finish out. Also, I love the closed cell foam for contouring custom surfaces when laying up fiberglass over it. I've used this method countless times on custom dashes, door and kick panels as it makes for easy sanding, shaping and finish out.

I'm very curious about the Silvertip system. I have been using the West 105 system for about 30 years and you are absolutely dead on when speaking of the amine float needing to be cleaned and abraded prior to continuing with either more glass work or filler for finish out. On the Silvertip product, if further glassing is required for build up do you still have to clean the surface or just abrade and keep going. This sounds like an outstanding product, maybe it is time for a switch.