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Struan's Firewall

This from yet another helpful member of the Lotus List, Struan Robertson from Australia.  It began with my post, and goes from there.

--- In lotuseuropa@yahoogroups.com, "Dave" <p914gtca@y...> wrote:

Beaverboard bites the dust.    http://www3.sympatico.ca/dave.syer/new_page_2.htm Below freezing at night, just above during the day - a real PITA  for fiberglass work - using a heater causes a few problems. I think I'll have to finish the body in the spring. As usual I got carried away, but I'm really pleased with the composite firewall. It has a real advantage over some other materials in that it can be laminated in co-planar (is that a word?) mounting surfaces in the Europa. The finished product is incredibly stiff and strong.

>> Dave

Hi Dave

I've just installed a Nidacore bulkhead in my 1969 S2. Don't bother going to all the effort and expense of fire retardant resins, they only extingiush when the flame is removed. With a flame from a burning fuel tank, they burn just as well as any other polyester resin. What I have used is vinyl ester resin which has a much higher heat deflection temperature (ie melting point) than normal polyester or epoxy, and it's totally resistant to fuel like epoxy. That's why they make underground storage tanks for gas stations out of it.I built mine by putting release wax on a large sheet of melamine faced particle board, a layer of surface tissue wet out with resin, a layer of 450gsm (1.5oz) chopped strand mat, followed by the Nidacore (10mm) whilst the resin is still wet and weighted down. It's applied like a transfer by rolling it to push out the air bubbles. The tissue gives a resin rich and totally impervious membrane on the engine side. Remember the Nidacore has been precut to size and is in three pieces. The main bulkhead and two smaller pieces which go down the lower back of the seats. All are joined once installed. to treat the edges of the Nidacore, you can use a normal steam iron to melt the polypropeleyne honeycomb to give a champhered edge. When the sheets of Nidacore are cured, peel them off the mould, trim and tab them into place with chopped strand mat. Just little bits here and there which can be easily ground off if things aren't right. when you are satisfied with the fit, then glass in the bulkhead properly both front and back. Now it's time to glass the interior with one layer of 450gsm (1.5oz) chopped strand mat with peel ply placed over the top whilst the resin is still wet.

Roll in the peel ply with you consolidator and leave to dry. When cured peel the peel ply off and you are left with a really good, but slightly textured finish. Much better than the ordinary chopped strand mat finish whish is pretty rough. If you can't get peel ply, go to a dress material shop and ask for nylon taffetta. It does the same job but is a whole heap cheaper than fiberglass industry peel ply. Good luck


Struan Robertson



Thanks for your reply

First of all, I've attached a couple of photos of my installation. The photo showing the rear of the firewall was taken whilst the body was raised up on top of the chassis.

As to some of your questions raised in your reply.

Yes an angle grinder seems to be the universal answer to a lot of problems. An iron is much neater, but requires a lot more time to get a neat edge.

The Nidacore (being filled with air) is not a bad heat as well as sound insulator. I've seen some flexible adhesive insulation which I'll look into as it will still need lots of insulation, and this stuff is pretty thin. I'll get the name and run it by you.

I didn't use cloth as to me it's flexural stiffness is not as good as CSM. If I really wanted stiffness I'd use stitched fabrics, but the price is over the top for what I was doing. Anyway, Lotus only used CSM exclusively as far as I can see from my car, so it was in keeping with the body. Albeit with a far more advanced firewall which will not rot.

A consolidator is a grooved roller used to eliminate all the air trapped in the glass/resin matrix, as well as keep the resin to glass ratio within reasonable limits. i.e. reduce resin rich areas. A must if you are doing any glassing.

Let me know if I can be of any further help.