How light is too light??

[Escadrille Ecosse]

So we have been discussing experiences in making lightweight composite panels for our cars.

Perusing the internet looking for inspiration of the best way of dividing up the multi-part mould I'm going to need for the Spitfire bonnet I cam upon this rather interesting bunch of people

Some ridiculously light panels for the current Lotus. Interesting they have gone for an unpigmented glassfibre layup which is what I did when making the original super-lightweight glassfibre panels for the Spitfire. Makes it a lot easier to see the glass is properly wetted out when going for the minimum resin content.

However this is perhaps the piece de resistance - an R26 replica shell. However I hope it is going to be fitted with a very good cage as a 40kg bodyshell will provide about as much protection as a paper bag

 

[Nick Jones]

Hmmmm, for a road car you really need something that won't turn to dust if you hit a badger / pheasant / woodpigeon / large bee

[JohnD]

When I was making the roof for Silverback, I made the mould in several pieces, so that I could get the finished part out, as you may wish to do for the bonnet.    I found that following the various pressings that had been welded together to make the original was a good way to decide where to position the 'fences' that seperate the mould parts when taking them from the original.     The logic behind this is that each panel had to come off the press, so would have no recurves in its outline.   Seemed to work!

 

[andymcp]

I remember seeing photos of the bikes on the Sulby Straight (at the TT) with the fairings deformed by the air pressure at +185mph.  Can't be good for aerodynamics...

[Escadrille Ecosse]

30 minutes ago, andymcp said:

I remember seeing photos of the bikes on the Sulby Straight (at the TT) with the fairings deformed by the air pressure at +185mph.  Can't be good for aerodynamics...

Air can get remarkably 'solid' at speed.

38 minutes ago, JohnD said:

When I was making the roof for Silverback, I made the mould in several pieces, so that I could get the finished part out, as you may wish to do for the bonnet.    I found that following the various pressings that had been welded together to make the original was a good way to decide where to position the 'fences' that seperate the mould parts when taking them from the original.     The logic behind this is that each panel had to come off the press, so would have no recurves in its outline.   Seemed to work!

Absolutely John. This is the mould set for the Spitfire tub I made back in the early 80s. All the split lines are along the body seams.

On my hardtop mould I did much the same as you making a bolt on flange for the returns around the door openings and across the header rail at the front.

The trick with the bonnet though is that the recurvature on the nose and around the headlights means that the split lines there are not in an obvious place along a seam which would help hide things. I think I am going to have to put a split in the mould across the bonnet top. Like they have done here..

Back to the Lotus Factory boys though. A repair section for the corner of the Elise front clamshell. You can see from the flash lines how complicated their mould is around the headlights. Hopefully I won't have to go this far....

[Escadrille Ecosse]

@JohnD with all those moulds you had for Silverback did you not ever think of building another estate? Understand there's a lot of work involved but the estate was a bit different.

Back to the subject of moulds after the chat above I was out in the garage today having another look at the bonnet and the way the draw angles might work. The other thing I want to do with this is make sure I get the panel lines around the quarter panels under the headlights.  This is my current thought (from a random bonnet pic off the internet)

A top section split across the headlight ring, two wing sections that wrap round the front, a grille section and a bottom flange to form the returns on the wheelarches, bottom of the wings and grille panel. This would make the outer bonnet shell all in one piece.

The inner arches, D sections under the sidelights and the two reinforcing panels either side of them would be separate pieces glued in. As would the bonnet locating cone brackets.

[JohnD]

After the 'Ring, I wasn't about the make anything else, but then what became SofS appeared on the Bay.  It seemed fated that I should buy it!     

On your new sketch, you aren't folloring the panel seams at all there, are you?  

John

 

[Escadrille Ecosse]

2 hours ago, JohnD said:

After the 'Ring, I wasn't about the make anything else, but then what became SofS appeared on the Bay.  It seemed fated that I should buy it!    

Fate intervened there mate

2 hours ago, JohnD said:

On your new sketch, you aren't folloring the panel seams at all there, are you?  

Not really, no

We'll see when I get the doors finished and do some trial fits