Fibreglass inner and outer sills and brake disc backing plates

[Elliot]

Okay just trying to gain opinion before i go down this route.

I can get complete strengthened fibreglass inner sills and outer sill replacements manufactured local to me and also brake disc backing plates with fire proofing fibreglass.

What do you guys think?

will they sell?

should i stick to galvanised metal?

these will be exact fit so no messing with dodgy repair panels from ebay so what do you think.

Will post pictures once mould is created and first ones are produced.

Elliot

 

[944Turbo]

If you can convince me they are as strong as the original metal, and will remian securely bonded, if the price was sensible I would seriously consider them
Tony

 

[edh]

ORIGINAL: 944Turbo

If you can convince me they are as strong as the original metal, and will remian securely bonded, if the price was sensible I would seriously consider them
Tony

I don't think you could ever convince me of that
..and would any bodyshop be brave enough to fit them without you signing a disclaimer absolving them of all liability?

I didn't think the Porsche sills were all that expensive? - or is that just the outers?

 

[Elliot]

These would be bonded and flush rivetted. For the same strength the thickness needs to be 0.3 mm thicker than the original steel sills but this should not be visible when fitted.

 

[Alexw]

Double Post, not sure how this ended up here []

 

[Alexw]

IIRC only the inner sills are load bearing (if thats the correct term), the outers are cosmetic?

 

[poprock]

I'd be happy with fibreglass outer sills but I think I would want the inners to be steel, since they're load-bearing.

 

[JM1962]

I would say both the inner and outer sills are load bearing since together they form a triangular section and are part of the torsional rigidity of the shell. In fact I think one of the reasons they are prone to corrosion is due to the stresses created in them from the rear suspension mount and the flexing of the shell, obviously the fact that moisture is also prone to collect in them contributes also.

 

[poprock]

ORIGINAL: Elliot

"¦ also brake disc backing plates with fire proofing fibreglass.

I'd like to know more about these. I need new backing plates anyway and something that couldn't rust in future would be very handy. Porsche are asking around £55 per plate for standard ones, so fibreglass could work out a fair bit cheaper too.

 

[morris944s2john]

Fibreglass sillas are nothing more than a dangerous bodge when fitted on a monocoque car like the Porsche 944.[:-]

The sills were metal for a reason, they are the structure of the car!!!

If the MOT man spots these he will fail the car, possibly condeming it as dangerous to drive with such a weakened structure. Not only does the rear suspensions depend on the sills on a 944, but also the SEATBELT mountings!! think about that.

 

[zcacogp]

ORIGINAL: morris944s2john
Fibreglass sills are nothing more than a dangerous bodge when fitted on a monocoque car like the Porsche 944.[:-]

The sills were metal for a reason, they are the structure of the car!!!

If the MOT man spots these he will fail the car, possibly condeming it as dangerous to drive with such a weakened structure. Not only does the rear suspensions depend on the sills on a 944, but also the SEATBELT mountings!! think about that.

I'm with this fella ^^^^. The reason that rusty sills fail an MOT is because they are structural. And chopping structural metal parts out and replacing them with fibreglass replacements would be a bad idea for a million reasons. Safety, passing an MOT, seatbelt mounts, rigidity of the chassis ... the list goes on. You'd end up with a deeply unsafe car which would handle like an undercooked plum duff.

Brake disk backing plates are items with no clear purpose anyway. I have removed them entirely from my S2 and the only difference is a slight reduction in unsprung weight (good!) and increased brake cooling capacity (also good!)


Oli.

 

[944Turbo]

Well Boats are fairly strong with FG box sections and lotus elise etc. chassis are bonded together, so keeping an open mind on this - have the mot requirements kept up with Elise type bonding?
I think the biggest problem would be getting a sound and clean enough surface to ensure an adequate bond.
Tony

 

[zcacogp]

Yes, there are fibreglass cars which are clearly road-safe, but the design will be material-specific. Just replacing a steel section with a fibreglass one wouldn't be sufficient, I'm sure. Bear in mind that a number of 'fibreglass' cars actually have seperate steel chassies - such as TVR and the like. And then you have the bonding issue ... and bonding fibreglass monocoques together is both an art and a science, and some way beyond the abilities of the average bodyshop.


Oli.

 

[944Turbo]

Was thinking the Aluminium tub that is bonded on an elise rather than the FG body - dont even know how that is attached, however Lotus do have a lot of composite experience and went Aluminium for the chassis.

Oh and backing plates - would have to be cheap as had no issues running without - A design that allows fitment without stripping the hubs might be popular.

Tony

 

[John Sims]

While I appreciate the anti rot advantages of GRP I would be very loath to use them as replacement cills.

944's were designed and tested with steel cill sections not GRP so, in the event of an accident, you have no clue what may or may not happen........and, in the event a significant claim is made it would just be another sneaky option for Mr Insurance Man to avoid paying.

 

[Neil Haughey]

These panels are also HT steel, its one of the strongest areas of the 944 chassis. Sills are not expensive in the great scheme of things and should last for many years once replaced.

 

[Mike_Pollock]

Would not be interested at all.
Think I'd prefer well rusted ones!
Mike

 

[Peter Empson]

Whilst I doff my cap for any cunning weight saving (whether intentional or accidental), I really don't think I'd go that far on a road car (i.e. without a serious cage). To my mind the sills are a major part of the strength and rigidity of these cars, and the genuine panels are not expensive after all.

 

[Hilux]

I can get complete strengthened fibreglass inner sills and outer sill replacements manufactured local to me

Cannot work!

The 944 has a stressed monocoque shell.

Fibreglass has completely different characteristics in shear and tension.

If the originals are being cut out to replace with something new then replace with steel.

Kit cars have a chassis, the rest is non structural in most instances.

 

[pauljmcnulty]

I'm struggling with this one too. I thought, quickly reading the OP, that it was a replacement for the box-style sill covers. I can't see how fibreglass can make any sense as both inner and outer sill panels?

I am happy to accept that they can be made with the same strutural integrity as steel (althoug I'd have thought they would be very bulky), but what bodyshop would have the skills, or want to take on, bonding them to the shell in a guaranteed safe way? The rear of the sill is the most important area of the car from a structural point of view; that joint would be critical to the safety of the car in an accident, affect the rigidity of the shell and scare any MOT inspector.[]