Ex-Racer Spitfire Mk1 Rebuild

[Escadrille Ecosse]

Got the bag on after tea. Tweek for the sealing tape was to add the loops to take up slack in the bag after the main ring of tape. Much easier.

Then pulled vacuum to get everything properly in to place and check for leaks.

The smiley hose is for listening 

I'll get on with the resin infusion tomorrow. Get the heaters on and that half of the garage warmed up for that job. 

[PeteStupps]

This is so cool, I'm in awe. Hope tomorrow goes to plan

[Hamish]

Waiting with baited breath

exciting waiting for the results. 
good luck. 

[Escadrille Ecosse]

Infusion day today. Seems to have gone OK although I had a minor moment as I had miscalculated the quantity of resin needed - not taken account of the reinforcing and the carbon tape - so I had to make up some more mid job. But all well.

Starting the infusion

And pulling off the air at the end

I took a bit of video which I've edited and put on to YouTube only 40 seconds. The rattly noise part way through is the vac pump running.

It's now courried up under the heated pet mats and blanket - bless

 

[Nick Jones]

Woof......

[John I]

That’s really clever and if I were 30 plus years younger “cool”.

[Escadrille Ecosse]

So a bit of a 'mare last night as the bag developed a microscopic leak somewhere on the suction side of the mould.

I never actually managed to locate it so spent a large part of the evening in the garage sitting in the folding chair reading my book and periodically turning on the vac pump for a few seconds.

So there was much trepidation as I pulled off the bag and various other layers to reveal the carbon which appears to have bonded OK. Back covered up again for another bake overnight before attempting to remove it from the mould.

[PeteStupps]

Yikes! Sounds a bit stressful. Hope it turns out ok 

[steveJM]

On 4/9/2021 at 3:01 AM, John I said:

That’s really clever and if I were 30 plus years younger “cool”.

or additional +10 years younger "Sic"

[Escadrille Ecosse]

Well it came out of the mould in one piece and seems pretty robust. Ridiculously light too.

There was a little it of sinkage of the gelcoat into the carbon weave along the bottom edge of the lid but as it will all get painted that is not a disaster.

[Hamish]

That’s a great finish. Well done. 

[Mark]

Excellent result! Looks great.

[Nick Jones]

Good looking part!  Excellent   But.....does it fit?

Finish looks rather better than Chris's (which was made from pre-preg) but actually I don't think the fact that the weave shows a bit bothers him at all.

[Escadrille Ecosse]

3 hours ago, Nick Jones said:

Good looking part!  Excellent   But.....does it fit?

Good question. I hope so. Need to trim it down before trying but hanging off doing any of that until I've got more bits made. Cutting carbon fibre needs some fairly robust dust management as it's nasty stuff to get inside you. So I'll det the dust extraction set up again and do most of it in one go.

3 hours ago, Nick Jones said:

Finish looks rather better than Chris's (which was made from pre-preg) but actually I don't think the fact that the weave shows a bit bothers him at all.

Others have said similar to make a feature of the fact that it's made of carbon and not steel.

And why not....

[Escadrille Ecosse]

Passenger side door skin de-moulded this morning. Lots of polishing before starting

Learning some tricks here. Putting masking tape on the raw edge of the cloth makes it a lot easier to handle while getting it into the mould. Creates a bit of waste because it is 'impossible' to remove and needs cut off but does the trick

So this is a two part mould as I wanted to try and laminate the return at the window slot as part of the panel rather than gluing it on later. Original plan for this panel was to have a layer of 200 cloth either side of the 2mm thick core and just some extra reinforcement at the door handle (Mk1 twist handle). Plus the tape strips around the core to avoid a large change in section

I the end I decided to beef things up and changed the inner 200 layer to a layer of 600 cloth instead. Adds about 400g to the weight of the panel but aside from the crease line near the bottom there isn't much in the way of shape stiffness in the door panel.

Bagging up and adding the resin

Pleased with the way it came out.

The return on the top of the panel worked well except for a couple of points where I didn't manage to get the gelcoat right into the apex. Bloody difficult to do as you can't actually see what you're doing in there mach in from either end. Fortunately the vac bagging ensured that the resulting holes got filled with epoxy resin. Not perfect but not really critical I guess.

What is interesting though is that my previously mirror smooth mould now has the same surface finish print through as the gelcoat on the door panel itself. I've not seen this with hand layup glassfibre so I'm assuming that it's a combination of the pressure from the vac bag and the heat from the curing mats that's softening the get on the mould and allowing this. I have found stuff called 'tooling gelcoat' which is apparently much harder that standard (and more expensive of course). It doesn't actually mention this phenomenon but presumably this is one of the benefits it gives.

Too late for these panels but when I come to do the bonnet I'll think about using the harder gelcoat for the moulds.

[PeteStupps]

On 4/18/2021 at 12:57 PM, Escadrille Ecosse said:

Pleased with the way it came out.

Cor blimey! As they say down here. That looks very impressive

[Escadrille Ecosse]

RH door skin made and out of the mould today.

I am gradually beginning to get the hang of this. It's lots of details that the videos tend not to cover.  Like how to fit the bag and the sealing strips to get it to hold vacuum first time and pull into the corners effectively.

And exactly how to position the various infusion aid layers to clear out the air from the fabrics as efficiently as possible as the resin goes in so you waste as little resin as possible. There's also tricks to play with how you feed the resin into the mould which helps de-aeration as you go.

It all works but getting the knack as it were just makes the whole process more efficient. Still quite a bit of work though. This was for the doorskin

Polished everything and applied four coats of chemical release followed by two coats of wax on Monday. With 20 minutes between each coat that took all afternoon.

Tuesday morning was heating up the garage so that I could apply the gelcoat in the afternoon. It's a special epoxy compatible polyester gelcoat so there is that styrene 'glassfibre' smell. So 'garage only' clothes and overalls on. Gloves and mask on. Weigh out the gel, mix in pigment and add the catalyst. You've now got 15 - 20 minutes max to get that onto the mould before it starts to go rubbery in the pot. Then clean up and go for a shower!

Wednesday morning cut out and lay in the carbon cloth and core material to the mould which took until lunchtime. Then after lunch add the peel ply, infusion mesh, infusion tubes, vacuum fittings and then get the bag cut out and tape on putting in the fold pleats round the edge as you go. Positioning of the pleats is important in getting the bag to pull into the mould and another one of the tricks that needs learned. Connect up the vacuum pump and knock-out pot and start pulling air out. Adjust the bag and membranes, pull down. Listen for leaks. Let in a bit of air, adjust the bag and pull down. And repeat until the bag is neat into the mould and it looks like the vacuum will hold.

That took about 3 hours and so a cup of tea while it sits under vacuum test.

All well with the vacuum so mix up the resin and start the infusion. By the time the resin is weighed out, mixed, into the mould and pulling clear of bubbles at the other end that's getting near tea time (what you Southerners call dinner time).

Back out again after tea to check all is well, put the heated blankets on and wrap everything up in old towels to keep it warm to cure which is 24 hours from mixing. Phew!

Next up are the door shells but first I need to modify the moulds I have for those so I can use them for vac infusion. Been thinking about that and I have a plan. Just need to see if that works.

Edited April 29, 2021 by Escadrille Ecosse
spelling

[John I]

25 minutes ago, Escadrille Ecosse said:

RH door skin made and out of the mould today.

 

 

Fascinating account of black magic, results of your hard work and patience very clear to see. Top dollar finish

[Nick Jones]

Some classy work going on here 

[Mark]

Looking great. Lots of work, but the end results are excellent.

[Escadrille Ecosse]

So... door shells.

I said that I thought I had a plan. Well I did but having thought about it more I decided it wasn't a very good plan. Modifying my existing moulds that were intended for the old GRP doorshells will actually be quite a lot of work and even then probably give a fairly awkward moulding job with the carbon fibre and still run the risk of not working that well. Not to big a deal with GRP but a lot of time and expense with carbon fibre.

The other issue is that when I made the GRP doors both the shells and skins were very light and flexy. Getting them to fit the car was a case of bolting in the shells and then building in any twist as they were stuck to the skins. Mostly worked but was very heath robinson and I got away with it largely because they were so flexy.

The carbon fibre skins have a some limited ability to twist shells (but not bend) but the shells will be pretty rigid even without the skins attached so. And having gone to all the effort of making the the moulds for the skins to be a good fit seems daft to start bending stuff rather than just having it right.

So I will make a pair of GRP shells from the existing hand layup moulds and use these as the basis for making new moulds suitable for the carbon fibre infusion.

First question then is how to make sure the shells will fit the skins I've made. Well I have the moulds for them and so all that's needed is to put the skins back into them and make the shells match. Only issue is the moulds for the skins are not rigid enough for that job - they didn't need to be if just making skins from them.

The job over the last couple of days has been to stick the moulds back onto the patterns with moulding PVA (different from woodworking PVA) and add some structural bracing on the back to make them thoroughly rigid.

In the past I've used wood or polyurethane slabs and glassed these to the back of the mould. However browsing You Tube I came upon someone using foam pool noodles and glassing over them. So I wen't down to B&Q and got some preformed pipe insulation, split in half and glued this to the back of the moulds. Hot glue did the job as long as it was sparingly applied to the mould first. Otherwise it would just melt the insulation. The insulation itself provides no structure it's just an easy way to form a mould for the GRP.

While this lot is left for a few days to thoroughly cure the next job is to make a pair of GRP shells.

 

[Nick Jones]

Ingenious! 

[Sprint95m]

Awesome 

[Escadrille Ecosse]

Moved on to the door shells today. When I built the Mk2 back in 1986 I had been for it to be all GRP, my own bodyshell and the bonnet, boot and doors commercial items. However the purchased doors were so dire that I ended up initially using steel doors to get the car on the road with the intention of making my own at some point.

That some point came a little earlier than intended. Herself had parked the car on our (very steep) sloping driveway but hadn't got the handbrake on enough and as sh opened the door to get out it rolled back, rather quickly. Fortunately she was still seated and the car was prevented from flying out into the street when the back edge of the door caught the wall and brought things to a rapid halt.

The door however came off somewhat the worse in the encounter forcing the plan for the GRP doors to be brought forward in a hurry (this was our only car) and as a result I cut many corners in making the moulds, especially for the shells, which were never particularly brilliant to start with. Now definitely the worse for wear having had three sets of doors out of them already. First for the Mk2, another set for a friend's 1500 and the last pair on the race car.

So I'm going to take another set of shells off them and use those to make new moulds for making carbon fibre parts.

Worst of the damage filled with moulding wax and polished up ready for the gelcoat.

[Escadrille Ecosse]

Got the shells out of the moulds today after a bit of a fight. The consequence of the quick and dirty design of the moulds, especially the return flange on the top edge.

Not bad really but I will give them a bit of a tart up to get rid of some of the bumps and lumps and evidence of rust and paint runs from the original steel doors. I'll also tidy up the area where the door latch goes so it's more suitable for the Mk1 latches.

Next job though is to trim and then match them to the door skins.