Escadrille Ecosse Posted February 4, 2023 Author Share Posted February 4, 2023 Managed a wee bit on the Spitfire while I was waiting for bits to arrive for the Scimitar. Got the red bonnet out as it's next up. The bonnet really isn't very well made and it hasn't worn well. The wings curl in on themselves at the back quite alarmingly. However it looks like someone spent a bit of time and effort making the mould. Moulding the raised wing seams integral to the bonnet is awkward but fairly doable in GRP. A different story with carbon fibre for various reasons. I could do it but it would involve multiple vacuum steps and I can't be bothered with that. So I'm planning on keeping the rather nicely executed beaded seam lines on the red bonnet. This means the cut line for replacing the wings needs to be well away from those. The outside edge of the 2" masking tape. The tape at the nose is where Im marking out the fake seam lines to match the original steel part. Then similar job with marking out the cut lines on the wings. Both sides marked up identiacally. Unlike the steel wings where the flanges are completely different. The arrows are to avoid operator confusion and I also covered up the raw edges with tape as they are a bit sharp. Hopefully a dry day sometime next week and I'll get everything outside and trimmed. Then need to look at putting in on the car! 2 Link to comment Share on other sites More sharing options...
Nick Jones Posted February 4, 2023 Share Posted February 4, 2023 Good to see some action on this. Hopefully and indicator that you are on the mend too?  So you are using the red bonnet top as the final part or to take a mould off? Link to comment Share on other sites More sharing options...
BiTurbo228 Posted February 9, 2023 Share Posted February 9, 2023 Again, looking very good! Oh, wonder if I could get some advice. I've got a rather tatty fibreglass GT6 bonnet for my Spitfire that was a bit too curved out at the lower trailing edges. Way back when I thought it was a good idea to cut some slits into the return and reshape them, bonding some more fibreglass on the inside of the return to hold it in the new position. That worked until I fitted the bonnet where it just cracked and sprung back into position (not sure if I did the clasps too tight, or there wasn't enough space for the reinforcing on the back) Knowing you can heat-mould fibreglass a bit I'd probably have tried that now, but I've slit the return so there's no strength left in it. Would you cut the returns off entirely and remake them? Or something else clever? I expect you'd scrap the fibreglass version and make one out of carbon fibre Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted February 9, 2023 Author Share Posted February 9, 2023 2 hours ago, BiTurbo228 said: I expect you'd scrap the fibreglass version and make one out of carbon fibre Well yeah Reshaping doesn't work that well on the whole, especially once the GRP is well cured. To have any chance you need to remove a lot of material from the thickness of the laminate as well as cutting reliefs in any flanges. The thinning also needs to extend fairly extensively. Then the whole thing needs held rigidly while you lay in more layers over the thinned area. The problem is though that polyester resin shrinks a couple of percent as it goes through its final cure so laminating on something that's already thoroughly cured builds in stresses or distortions. It's why you really want to get the laminating done in as short a time as possible. The other thing is that grinding off lots of GRP produces lots and lots and lots of really nasty dust. The best thing to do is cut the distorted areas off and start again. Making sure that the feather into the original material is as large as practical. You're wanting at least 2" to achieve a decent bond. The other way of doing it is to straighten out the distorted part of the bonnet by gluing in bits of wood, etc on the reverse side. Take a mould off the area in question amd make a part repair panel off that mould. Link to comment Share on other sites More sharing options...
BiTurbo228 Posted March 11, 2023 Share Posted March 11, 2023 Bother! Guess I might be getting into mould-making at some point in my future. A partial repair panel certainly sounds like the most viable option... Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 12, 2023 Author Share Posted March 12, 2023 (edited) On 3/11/2023 at 11:06 AM, BiTurbo228 said: Bother! Guess I might be getting into mould-making at some point in my future. A partial repair panel certainly sounds like the most viable option... @BiTurbo228Well, I've a couple of now redundant moulds taken off the steel bonnet you could have. Curve at the top back isn't quite right but good as a base as the rest is good which is what I'm doing with them for my bonnet. They're a bit rough as they were simply transfer moulds rather than the finished article but decent enough. Edited March 12, 2023 by Escadrille Ecosse Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 16, 2023 Author Share Posted March 16, 2023 Back on the chain gang. Covid wearing off so I've taken to the garage to work on the Spitfire again. At last. Last wee job on the steel bonnet before I can get it ou the way and get the car down on the hoist so I can get to making the buck for the main bonnet mould. I have worked out a plan for the bonnet cone mounts the first step of which is to take a basic mould off each side. The brown tape was refusing to stick properly for some reason so had to resort to masking tape. Less than ideal but parts are going to need a good bit of work anyway so meh, gets the job moving. And in anticipation I finally stumped up for a gelcoat spray gun. Specifically for the main bonnet panel but I'll practice with it when I'm making the inner panels for the bonnet. It should give a quicker, smoother and most importantly pinhole free gelcoat for the carbon fibre layup. 1 Link to comment Share on other sites More sharing options...
Nick Jones Posted March 16, 2023 Share Posted March 16, 2023 Good to see you back at work on this, not least because it shows you must be on the mend. Gelcoat gun…. Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 16, 2023 Author Share Posted March 16, 2023 8 minutes ago, Nick Jones said: Good to see you back at work on this, not least because it shows you must be on the mend. Gelcoat gun…. Thank you. Yes. The opportunity for making a humugous mess is considerable Link to comment Share on other sites More sharing options...
Nick Jones Posted March 16, 2023 Share Posted March 16, 2023 27 minutes ago, Escadrille Ecosse said: The opportunity for making a humugous mess is considerable Yes…. Though it looks like it uses some kind of disposable mixing vessel? Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 16, 2023 Author Share Posted March 16, 2023 3 minutes ago, Nick Jones said: Yes…. Though it looks like it uses some kind of disposable mixing vessel? You can use the plastic cup or disposable paper cups which minimises the cleaning to the end cover and nozzle. I got a few spare cups. The gel is obviously quite viscous and heavy which prevents you using a conventional spray gun as the nozzle on this is about 1.5mm diameter. And the feed is direct to the nozzle. On the plus side the high viscosity of the gel should reduce atomisation and overspray. Although the garage will get a bit high on styrene levels I imagine . Link to comment Share on other sites More sharing options...
Nick Jones Posted March 16, 2023 Share Posted March 16, 2023 1 hour ago, Escadrille Ecosse said: the garage will get a bit high on styrene levels  the garage will......? Link to comment Share on other sites More sharing options...
PeteStupps Posted March 17, 2023 Share Posted March 17, 2023 Great to see some more action on this Colin, I have nothing to contribute but love seeing the weird and wonderful processes involved! Link to comment Share on other sites More sharing options...
JohnD Posted March 17, 2023 Share Posted March 17, 2023 Colin, you are a martyr to detail! "It should give a quicker, smoother and most importantly pinhole free gelcoat for the carbon fibre layup."   This, for a part that will be invisible in use! John Link to comment Share on other sites More sharing options...
Hamish Posted March 17, 2023 Share Posted March 17, 2023 But doesn’t the gel coat go in first this is then the outside finish that May or May not be painted. ?!  Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 17, 2023 Author Share Posted March 17, 2023 53 minutes ago, Hamish said: But doesn’t the gel coat go in first this is then the outside finish that May or May not be painted. ?!  It does Hamish but everything will get painted. And John is right, the main panel aside everything else is underneath and hidden from view. But I know it's there Link to comment Share on other sites More sharing options...
JohnD Posted March 17, 2023 Share Posted March 17, 2023 You are like the church stonemasons of old, who would carve the back of the capital of a stone column with the same dedication as one at ground level and visible to every worshipper, because their god could see it! John Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 19, 2023 Author Share Posted March 19, 2023 Got the transfer moulds off the bonnet cone mountings. As expected rather rough but there is a lot of work needed anyway to get these even to the right basic shape the main thing was to get them done so I can get the bonnet out of the way. I also rethought the grille panel and rather than making it with the holes that then need filled I filled the holes in the mould and remade the panel solid. Bit of brain fade with that one! 2 Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 20, 2023 Author Share Posted March 20, 2023 Well here we go... Starting at the back where it meets the scuttle. Might be better than the steel one and superficially OK but in reality all a bit wavy in both planes. Going to take a bit of rectification before we get anywhere near trying to fit the wings. At least it fits left to right 1 Link to comment Share on other sites More sharing options...
Nick Jones Posted March 20, 2023 Share Posted March 20, 2023 Ah man..... hope you have a decent supply of patience pills! May the force be with you! Link to comment Share on other sites More sharing options...
PeteStupps Posted March 20, 2023 Share Posted March 20, 2023 It definitely looks like a daunting prospect. And being a stickler for detail, I can imagine you're going to burn quite a few hours on it! Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 23, 2023 Author Share Posted March 23, 2023 (edited) Fizzin' jings. As they occasionally utter in these parts. Beginning to lose track of this but here we go. The mould for the carbon bonnet.... Plan A. Fix up the original broken 'blue' GRP one to use to make a mould. NOPE. Too broken and areas at the back that are the wrong shape. Plan B. Take a mould off the excellent shaped GRP 'green' bonnet. NOPE. It's GT6 Mk1 and too much work to remove the bulge and sort the sidelights. Plan C. Take a mould off the rebuilt steel bonnet. NOPE. Good basic shape but the top panel needs filling and the wings dont have the right curve at the doors and don't want to spoil this but doing too much work. Plan D. Chop up the cheapo 'red' GRP bonnet to remove the crap bits, wings and grille panel and graft on better bits before lots of filling and sanding. The top panel is generally very good and the seam lines between that and the wings are nicely moulded. Having done a fair bit of work on the the chopping up and reinforcing I now realise that plan is a NOPE too. The issue is the rear edge of the centre panel. It is a bit wavy in the vertical plane. Caused by the back edge curling up when moulded. I could grind this back and fill the hollows, except that it also affects the bit by the recess for the air vent. And fixing that would be a nightmare. So Plan E. Which is a bit like Plan C except that I'm only going to take a copy of the top panel and quarters at the head and sidelights. Also to get a better mould line I'm going to extent this panel over the wings seams with the finishers in place to give a more distinct feature. This will then be used to make a GRP centre panel to which I will attach the wings and grille and fill that to size/shape. So yeah. Bugger. Significantly more GRP work than anticipated. The bloody bonnet is getting dizzy. But at least I'm getting practiced at how to lift the thing on and off the car without assistance and I'll get an early shot to practice with my new gel gun. Edited March 23, 2023 by Escadrille Ecosse Link to comment Share on other sites More sharing options...
Nick Jones Posted March 23, 2023 Share Posted March 23, 2023 2 hours ago, Escadrille Ecosse said: Fizzin' jings New one on me….. but seems like choice expletives are appropriate….. Perfection is difficult. Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted March 26, 2023 Author Share Posted March 26, 2023 (edited) While the Scimitar is sulking and blaming me for its latest woes I have left it to pout while I get on with its garage companion. While it is annoying, taking a mould and buck off the steel bonnet is will probably give me the best result at the end and so I have been prepping it for the glassfibre. I'm going to take the mould off the bonnet while it is on the car to avoid any potential distortion in the rather lager and very flexy panel. So there was quite a bit of masking off to protect against spills. I have ordered some clips to secure the wing finishers so while waiting on those arriving I did a bit of fettling with the hammer and dolly then started covering over the various holes, mainly headlights and air vent. And I also remembered a trick with this that I'd forgotten from many years back which is that masking tape is much easier to use than the brown tape as it is slightly stretchy and has better general 'stickiness'. It is also quite resistant to the glassfibre resin on either side as long as you can seal the edges. And the way to do that is to paint on some cellulose lacquer before applying the release agent and wax. And to avoid tricky returns I'm going to split the mould round the grille aperture so added the flange for that too. I can then add the return flanges with the bonnet off the car and upside down. Edited March 26, 2023 by Escadrille Ecosse 4 Link to comment Share on other sites More sharing options...
Nick Jones Posted March 26, 2023 Share Posted March 26, 2023 Most educational. Thank you. I'm enjoying the process and thoughts behind it Link to comment Share on other sites More sharing options...
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