FOAMING the SPIDER
Just came back from my vacation. 10 days ago Reinhard ( MDA GT40) helped me to fill the doublewalled RCR spider with foam to supress eventual resonance sound effects and add even more stability.
THe RCR Spider has a nice finished surface inner skin which together with the outer skin builds a hollow volume of calculated 10 - 11 liters. It is open at the back end. First i closed this opening with a 1,2mm PS Foil ( we use this in our company for forming yoghurt cups).
I thant fixed the spider again to the chassis and made sure that the alignment is still ok. I also checked the windscreen and door fit.
THe whole procedure was done with all the body panels fixed, doors and rear clip latched and closed, to be able to permanently control the alignment during the process.
Next we drilled 3 7mm holes into the inner skin ( 1 each left and right along the top of the windscreen and one in the middle spider section). We used this first to check for any airleaks of the enclosed spider volume. We found some and we sealed all the seams with gaffa tape. THe only opening we wanted were two at the back end of the spider. THis would force the foam to fill every part of the spider any other material would flow out to this 2 overflow holes.
THe main component is the correct foam.
IT IS NOT POSSIBLE TO DO THIS WITH standard PU foam from the home depot. IT would expand to fast and destroy the spider.
We choosed a material from the proffesional boat industry. It is a 2 K epoxy foam. ( this is the adress of the US distributor
Nida-Core Corp.
541 NW Interpark Place
Port St Lucie, Florida 34986
USA
Tel : 1.7723437300
[email protected] )
Here is a description of the system:
Sicomin - Composites, résines epoxy, fibre de verre, carbone, kevlar, peintures, gelcoat
We used the PB 250 epoxy with the DM02 hardener ( 100 : 36 mixing relation). THis means it will give a foam with the density of 250g/l. It expands with a factor 1:4. As the curing curve is much slower as the expansion curve it will flow as long as it expands without building up any big pressure. As long there is one expansion hole, it will fill the whole volume and than expand through the leftover opening.
Me mixing the foam
Reinhard
For application we used 120ml pharmaceutical syringes. We always mixed maximum volumes of 350gr and than filled it into the syringes and than put it into the car. We filled app 0,5 liter mix in each of the front holes and app 1,5 liter in the center one.
Filling the syringes.
Filling the spider
THe result
We are very happy with the result. THe mixed volume fitted very good to the calculated volume, we had very little overflow. The spider is completely filled. No distortions happened. With the DM02 hardener almost no exotermic reaction was tracable. If i close the doors now, the shut sound is more silent with a fat and solid note. The whole spider gained in additional rigidity to the already very good RCR base.
Although the epoxy foam is not drawing water (like PU foam does ) i will close the back end of the spider by laminating it with polyester and glass.
TOM
AWH: 206 h