cutting holes in the radiator shroud

oaktree11 · #1 11th September 2012, 13:19

Hi Guys,

This is probably another naive message from me but you will all be accustomed to them by now!

I am about to cut the slots in the fibreglass radiator shroud. Before I do I thought i would ask some advice.

I have trial fitted it and lo and behold, with a little trimming it fits! The rivnuts even align properly!

I see that there are "dimples" in the gelcoat which I assume are the centres of the radii for the ends of the slots. My immediate thought is to drill through these with a suitable diameter hole saw then cut the straight lines?

IMG_0116 by oldpropuk, on Flickr[/IMG]

What diameter is best, I guess larger is better for airflow but what looks best?

I am not experienced with fibreglass but I have found that my Dremel with a cutting wheel works really well at slicing through it.

Any help welcome! - John

MartinClan · #2 11th September 2012, 15:51

I used a stepped drill to do the hole at each end of the slot and then joined them up using two cuts from a junior hacksaw blade. A hole saw can be a bit vicious in fibreglass. File used to clean up the hacksaw cuts and make them nice n straight. Afterwards the edges all need a good go with wet and dry just to add a bit of radius to them.

As for size - I think that is up to you. As I remember I used 25mm diameter for the holes forming each end of the slot.

Wear gloves if your skin is at all sensitive. Fibreglass dust will make you itch for ages!

Robin

Patrick · #3 11th September 2012, 16:57

I honestly can't remember the method I used, but I seem to remember spending a long time fine tuning with sand paper. I think it mignt have been step drill / saw. I made the holes quite big on mine.

peterux · #4 11th September 2012, 17:00

Yup, the dimples are the centres for the holes.

Nose cone with slots by marlinpeter, on Flickr

According to my Flickr build pictures, I cut the holes and slots with a 26mm hole saw, jigsaw and file. (both hole saw and jigsaw were battery powered tools, so quite gentle)

I think Patrick Short cut his slots bigger so have a look at his pictures and decide which you like. I don't think it makes any difference to the cooling.

A tip I got from Simon, at the Marlin factory, was to use abrasive paper wrapped around a short piece of hose pipe to round off the edges. They need to be rounded to pass the IVA 'sharp edge test'

...peter

Patrick · #5 11th September 2012, 17:37

My oversized holes

With paint:

oaktree11 · #6 11th September 2012, 17:54

Thanks guys, invaluable information as always more stupid questions to come!
John

morris · #7 12th September 2012, 12:00

I'm planning on leaving mine till post IVA as I know it's going to be a fiddly job to get looking nice and straight and will also be one less thing for the radius tester to pick up on. I've never worked with GRP either so not looking forward to this one.

What's the verdict on the Marlin stainless grill to sit behind this. They want £80 + VAT which seems a lot. is it a perfect fit or will I end up making the usual adjustments that I'd have to if I just bought a sheet of mesh elsewhere? I'm also wondering about the fixing method as there are no clips build into the nose cone ready to go.

peterux · #8 12th September 2012, 12:31

Quote:

Originally Posted by morris

I'm planning on leaving mine till post IVA as I know it's going to be a fiddly job to get looking nice and straight and will also be one less thing for the radius tester to pick up on. I've never worked with GRP either so not looking forward to this one.

What's the verdict on the Marlin stainless grill to sit behind this. They want £80 + VAT which seems a lot. is it a perfect fit or will I end up making the usual adjustments that I'd have to if I just bought a sheet of mesh elsewhere? I'm also wondering about the fixing method as there are no clips build into the nose cone ready to go.

Some cars have been finished and painted with no slots at all, so it's not essential. Drilling and cutting the GRP was easier than I imagined before I started. It's a bit like woodworking but with nasty sharp splinters.

The Marlin grill is a nice piece of SS mesh and polishes up nicely but you may be able to get it cheaper somewhere else. (This looks similar but I can't confirm if its the same quality or size....http://www.cbsonline.co.uk/product/W...erture_SSMESH3 )
Mine came with a nice formed fold down the middle which made it easier to fit but of course it needed a little trimming round the edges.

I bonded and glassed some small ali tubes on the back of the nose cone along the edges and then fixed the grill with SS cable ties. The SS cable ties were a PITA to fit and I think I would use ordinary nylon cable ties if I did it again.

...peter

MartinClan · #9 12th September 2012, 12:31

I bought some stainless woven mesh from ebay. It wasn't cheap - but cheaper than Marlin. You do need some good cutters to cut it too shape as being stainless it is tough as old boots.

To fix it I bonded some small ti-wrap bases to the inside of the nose cone and then just simply ti-wraped it in place. To remove it it is just a matter of clipping the ti-wraps and them replacing them to re-fit. Simple and secure.

Cheers, Robin

oaktree11 · #10 12th September 2012, 13:17

I was certainly thinking of buying some SS mesh rather than going to Marlin. My thoughts were to bond some studding in strategic places to be able to secure the mesh with nuts and big washers but I think I like the cable tie idea better.
John

NigelB · #11 12th September 2012, 20:55

Quote:

Originally Posted by morris

is it a perfect fit or will I end up making the usual adjustments that I'd have to if I just bought a sheet of mesh elsewhere? .

I've certainly never seen the words 'perfect fit' and 'Marlin' together in the same sentence....................................!!

I recently had my radiator grill replaced. When I went to fit the original, it was completely the wrong size. It was one made for the Cabrio. (When did Marlin last produce one of those.?? Over to you Mike!!)

The replacement 'grill' arrived and it was simply a sheet of stainless steel mesh, neither cut to size, nor folded down the centre line.

So Ian, I think your usual adjustments would be required!!

denniswpearce · #12 12th September 2012, 21:56

Peter is right about some Marlins not having holes, mine is like that.

Marlin at home 029 by denniswpearce, on Flickr

Mike · #13 12th September 2012, 23:27

Quote:

Originally Posted by MartinClan

I bought some stainless woven mesh......... You do need some good cutters to cut it too shape as being stainless it is tough as old boots.

Cheers, Robin

Its easier to cut with an angle grinder using a slitting disc (approx only 1-2mm thick), but make sure you clamp the mesh securely before starting.
Mike