Sandblasting the K

[240kconvertible]

Can't stop fantasising about a carbonfibre bonnet as we don't really have enough numbers to warrant building the moulds for the fibreglassing.

I hopefully will be finished the majority of stripping/painting the shell this weekend so you should be able borrow the modified gun next week to get into the cavities Kent.

As it stands i'm going to drop my bonnet, doors and boot lid into Redistrip at blacktown to strip them next week at a cost of $600 gst inc. $2000 to strip a whole car not painted though. I'll then cover them in POR before high build primer. The bonnet will be going to the panel beaters to get welded up the front passenger corner exists no more.

[khughes]

oh man, after spending all saturday stripping the battery tray area of the engine bay, i must say, getting the thing sandblasted sure looks inviting

but better to spend a couple of extra hrs of my time rather than pay somebody else i figure (atleast for what i can do myself)..

I think some of my larger photos are dead (stupid software!), but here are some shots of my hard work (up to the suspension tower, it is a little hard to see grey on grey! )

http://www.project240k.com/images/thumbnails.php?album=30

i don't think there is a way around not removing the brake and clutch booster, the brake booster is too big to strip/spray around.. i hope it isn't too difficult

[khughes]

i would have thought that to CF the bonnet, it would cost exactly the same to make a mould etc...

as good as it would be, i think it would be a little too prickly from an engineering point of view certainly if done to a budget.

let em know how it goes, i will have to get my front chin valance sandblasted, and redistrip are very local!

i may not need to grab the gun off you for a good couple of weeks (until xmas is over atleast, i cringe at the thought of stripping deadener off the bottom of the car!)

[Mr Camouflage]

this one? http://www.classiczcars.com/forums/showthread.php?t=19042&highlight=240k+coupe+blue

Yeah, for some reason I though it had an FG bonnet.

Might ask lurch if he knows.

[aarc240]

as good as it would be, i think it would be a little too prickly from an engineering point of view certainly if done to a budget.

Have a read of the National Code of Practice (NCOP) for modification and construction of light vehicles.

Replacement of removable panels with ones made from GRP is specifically permitted with a minimum thickness of 3mm.

That requirement is there for the sole reason of preventing 'crash through' intrusion and subsequent increased likelihood of injury to a pedestrian.

Note this does NOT include doors or door skins which must remain metal!

So, all that is needed for ECF (epoxy bonded carbon fibre) is for the impact resistance of the panel at the desired thickness to be shown to be at least equivalent to that of 3mm GRP.

The manufacturer of the material can provide the data needed.

The main difference is that a metal panel (even aluminium) will bend and stretch on impact. GRP will bend to a much more limited degree and then fail catastrophically ('punch through'). CF exhibits similar characteristics although the amount of energy absorbed before 'punch through' is much higher for the same thickness.

The downside with CF is that when it does fail it produces some very nasty pieces which still retain that incredible resistance to deformation and have razor sharp edges as well!

I've seen such pieces punch straight through the tread area of interstate truck tires, destroying the case in the process.

[aarc240]

Can't stop fantasising about a carbonfibre bonnet as we don't really have enough numbers to warrant building the moulds for the fibreglassing

A CF bonnet will require a mould every bit as expensive as that for GRP.

For strength, carbon fibre construction is done by laying up the epoxy and CF, bagging the whole thing, pumping out all the air and then baking in a high temperature oven. If high strength is needed then another outer skin, bag or shell is required so that the article being molded can be placed under pressure.

Things like carbon fibre race car tubs, wings etc etc are done in an 'autoclave' with a complete mould set covering every surface and under VERY high pressure as well as high temperature.

Not withstanding all that, I must admit I've been toying with the idea of a ferro-concrete mould of the bonnet and then doing a bagged & baked ECF replica. Bloody expensive and time consuming though!

[khughes]

well, if you ever decide to go ahead with it, i am sure there will be some of us very interested in sharing the costs!

[240kconvertible]

Sorry aarc240 I assumed it would cost more for carbon fibre moulds.

I'd really like one but I can't see it happening it's just too big a cost for such a few bonnets. Epoxy resin is horrible stuff to work with, it and sanding drove me from the family business of boat building to a less dirty life of sales repping.

If someone ever did get it going you'd have to sell them over the net and make about 50 to recoup your costs and time I reckon. First thing we need though is to find the perfect bonnet to start with.

How long has it taken you on the engine bay so far Kent? the pictures look good.

[khughes]

too long no seriously, not much has actually been done, it took a whole day just to do the left side of the front panel and that front side of the bay!

i just have to keep reminding myself that every bit of rust i uncover makes it well worth the effort! i have to say, i can't wait to just pour the stripper on the roof and sides.. smooth surfaces are very nice to strip..

i have spent probably 3 full days on it all so far (with some help from my girlfriend, my chief POR painter)

[Mat Big Hat]

ok, ok, so it's among the heaviest datsun bonnets

remember us yanks didn't get those bomber glorias

howsabout a carbon fibre bonnet ...

[aarc240]

Sorry aarc240 I assumed it would cost more for carbon fibre moulds.

I'd really like one but I can't see it happening it's just too big a cost for such a few bonnets.

You're right about the cost, particularly if done the 'conventional' way.

A ferro-concrete mould is a short life and relatively cheap solution but for a very limited number, who cares?

A bit like Holden with the last Monaro - to make steel dies for those big side panels would have killed the project so they used ceramic dies. Life expectancy was in the order of 250,000 articles maximum but then they sure weren't planning on building millions and probably never anticipated building as many as they did.

Epoxy resin is horrible stuff to work with, it and sanding drove me from the family business of boat building to a less dirty life of sales repping.

Funny about that, I got out of my original trade for the same reason (though not the same trade).

First thing we need though is to find the perfect bonnet to start with.

That's probably the main reason to get me off the backside and do a mould - the bonnet on our car is dead straight (at least it is as yet).

The fault with it is minor rust in the frame, easily covered to make a usable master for the frame mould part of it.

If I can con my ex son-in-law into it there just might be a chance. He loves playing with that sort of stuff.

[khughes]

If I can con my ex son-in-law into it there just might be a chance. He loves playing with that sort of stuff.

can we convince him with cases of beer?