Nick Davison
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| posted on 18/6/04 at 09:18 AM |
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Any Ideas
I now need to make a bonnet which I would orefer to make out of GRP so I can paint it without it cracking. The dimensions and position of the
nosecone have been modified so I am starting from scratch. The engine is in and all pipes etc are in place and I now know where the clearance
problems will occur (see avatar).
The question is what material can I use to get the plug formed, I was intending making the plug and taking the molding directly off it while it is on
the car. The materials I have thought of are Ally, hardboard scored on the underside to let it bend and then painted, flexable perspex.
Any thoughts.
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Jeffers_S13
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| posted on 18/6/04 at 09:50 AM |
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I would build it off the car with ply formers and foam, see S Graber or Alan B websites for all the info and pics you could ever need.
James
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Nick Davison
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| posted on 18/6/04 at 10:32 AM |
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James
I can understand that that is a good method and a good idea also probably the correct way of going about things but this is only a one off and I am
looking for a quick and easy alternative.
Nick
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timf
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| posted on 18/6/04 at 10:34 AM |
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former cut to shape of either end of bonnet spaced apart then flexi ply applied for the buck
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Nick Davison
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| posted on 18/6/04 at 10:46 AM |
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Flexi ply sounds like a good idea, is this easy to form into the required shape or will it take some force to get round the curves? Also is it
readilly available?
Nick
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timf
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| posted on 18/6/04 at 11:43 AM |
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flexi ply is available from all decient timber merchants if not flexi mdf is available from b&q
the flexi ply doesnt need much force to bend it to shape
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Jeffers_S13
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| posted on 18/6/04 at 11:53 AM |
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I was gonna suggest flexi MDF, but Im not sure how it would cope with the taper, as it only has slots cut along one axis. I think flexi ply would
stand a better chance as I dont think its slotted, its just quite thin, with it being thin though you may end up with very slight dips where its
unsupported underneath. Maybe you be better off with lots of formers and stringers that are quite thick similar to how an old plane fuselage is
built. Then much use of electric plane and sander to create the cured shape needed.
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Nick Davison
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| posted on 18/6/04 at 01:01 PM |
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I will have a look at the flexi ply aspect.
Nick
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JoelP
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| posted on 18/6/04 at 01:21 PM |
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FWIW, i started with a normal bonnet and chopped it in two, cut the holes for the exhaust, sat each half at the sides of the car, all i need to do now
is clamp or bolt the two bits together and fibreglass the middle up. Then smooth fill and paint...
sounds so easy like that.
Steve Gusterson's website also has lots of info on fibreglassing, its a good read. (cheers steve BTW...)
Beware! Bourettes is binfectious.
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AvonBelgium
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| posted on 18/6/04 at 01:26 PM |
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Nick,
Working on my grp bonnet too at the moment.
What I dit:
make a flat grp ( 100 x 130) piece, when it is set for 30 min , take it of the mould ( glass, alu flat and glossy surface !!).
Then bendt it on the car, let it set for 24 u.
( fixed it with tape)
Now i have a nice shaped grp base for the bonnet.
You can use this to make a plug, or use this as a base to make the bonnet itself.
I try to make some pictures
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Nick Davison
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| posted on 18/6/04 at 01:51 PM |
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That's clever, how did you prevent it from sagging in the middle when you put it onto the car to set? Or did you have a former to lay it
over?
Nick
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AvonBelgium
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| posted on 18/6/04 at 02:16 PM |
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Made the grp plate with 2 layers of 200 gr, let it set till the grp becomes already hard ( but it is only fully set after 24 u )
That way the grp plate was already sufficient set to handle and not to be extra supported.
I was able to bendt it very nicely on the car and fixed it ( tape ....)
I did use only two tubes to support the sites.
This weekend I'm going to make several extra support inside the bonnet, therefore I bought some strip that i can glue inside the bonnet and
cover them with polyester, when this is set completly i have to start on the louvres, then sand it, fill it .........
And hope it is ready for painting in 2 weeks
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Nick Davison
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| posted on 18/6/04 at 02:29 PM |
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Did you gel coat the outside and if so did bending it have any effect on the gel coat finish. I still intend to paint after but whant a gel coat as a
good start.
Nick
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AvonBelgium
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| posted on 18/6/04 at 02:39 PM |
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No did not use gell coat, because i need to make the louvres in it. will use some spray filler to make the finisch.
Don't have expierence with gell coat
I used some spray for protecting schoes for water ( silicone ) or you can use moulding wax.
Make sure that the glass, plexi,alu that u use to make to grp plate is smooth.
Make sure that the resine is fully impregnated in the glass, then you have a nice finisch already on the grp plate.
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Nick Davison
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| posted on 18/6/04 at 02:52 PM |
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I will give it a try this week end. Fingers crossed.
Did you trim it as you put it onto the car?
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AvonBelgium
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| posted on 18/6/04 at 03:48 PM |
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yes and no, I trimmed it with 2 a 3 cm overlap all around.
Now I trim it correctly before putting in the reinforments.
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pbura
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| posted on 18/6/04 at 04:07 PM |
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I corresponded once with Phil Rowe of Oz about how he made a scuttle this way. A couple of additional flourishes based on that:
-- Another good material for laying up the sheet is that white laminated stuff you can buy at a Home Depot-type store.
-- You can trim the lay-up to the shape of a cardboard template made beforehand, while it is going off.
-- Flanges along the side edges can be formed by standing the work-in progress up on whatever you use for molding the flat sheet. This will give a
nice perpendicular surface.
In his case, he worked with the "bad" side up and finished off with body filler before painting.
Good to hear that moldless construction can be done with something so big as a bonnet, AvonB.  I'd really be interested to see pictures,
and to learn about how to make louvers.
Pete
Pete
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marc n
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| posted on 19/6/04 at 12:44 AM |
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for our new bonnet we made a flat sheet of fibreglass on a sheet of glass, gelcoat then one layer 100g and one layer 200g, then made a ply template of
the scuttle height and one of the nosecone, joined the two together with a spine through the centre of the bonnet line with a spine at both bottom
edges, then clamped the bottom edge on one side rolled the sheet over to the other side and clamped. then turned over and put 5 layers of 200g mat to
hold the shape, let it fully cure then remove. by only having three spines it gives the bonnet a natural shape.
hope this helps
regards
marc
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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AvonBelgium
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| posted on 19/6/04 at 11:48 PM |
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I have taken some pictures with my mobile phone, so not that good , Sorry
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Nick Davison
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| posted on 20/6/04 at 08:45 PM |
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Because of the complications I have with the sides of the car, they are not straight down but are steped out for air vents/cooling (see photos) and
the lack of clearance under the bonnet I elected to go for the traditional method and make a mold. I used thin ally to make the shape and included
returns on the bottom edges so I can then return the edges of the finished item. Photos in the archive.
Interesting discussion never the less and I have learned some more.
Also I like your carbon components AvonB is that your work?
Many thanks
Nick
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