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Learning how to build Lotus Seven replicas...together!
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PostPosted: March 12, 2022, 10:14 am 
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That's tough, as is your buck. I'd minimize shear loading from the perfectly vertical surfaces with some taper or minimized depth/area of shear or leave the bowls open to aid the elimination of air pockets. Another would be essentially what "lost foam" is to metal casting, but you dissolve the foam out of the mold with solvent. The ideal buck is just strong/rigid enough to make the mold; traditionally chicken wire, paper, and plaster or clay.

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Frame L x cockpit W x eng bay HT (w/o hood/bonnet/cowl)
Lotus Super Seven: 115 (no spare) x39x7.25
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Champion (Book): 114x42x11
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McSorley “442”122x46x14
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PostPosted: March 12, 2022, 11:20 am 
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I feel your pain. You put in a lot of work to make the buck and now this. I hope you can save the buck.

It sure looks like the torn glass was not saturated. I am not an expert on this. I made my doors using just a few applications of good-old Johnson's paste wax as the release agent and was successful. I did not buff it, just let it sit after application. Not saying that it will work for you. Most everyone here recommended the PVA.

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PostPosted: April 2, 2022, 11:19 am 
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When I did my CF seat, I did use PVA, and I still ended up destroying the mold, the seat was fine. BUT...

I didn't know you were supposed to get water in there to dissolve the PVA. :oops:

But you do have a lot of recesses that even if you use PVA and used water to dissolve it, you have to make sure there is a draft on steep surfaces like those little vent/detail pockets.

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PostPosted: April 9, 2022, 5:37 am 
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Thanks guys, actually damage is fairly minor. Made some good progress on the plug repair today, looking forward to getting some time devoted to second attempt over Easter if the filleting wax arrives from the UK in time (Easy Composites). The clay cooled quickly resulting in an unacceptably short working life, but as it was available locally thought it was worth a try - will use the wax this time. Also making the vent slots shallower, adding some airlines to inject air between the mold and plug to assist lift off.

Took a long time to get around to milling the exhaust manifolds, will be interesting to see how they perform. The J series components are easily interchanged between the variants, so could put J32 heads on the J35 block and have individual exhausts but routing will be challenging.

The engine mount plates have been fitted, next job is to weld the support tubing to them.

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exhaust test fit.jpg


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PostPosted: April 23, 2022, 7:33 pm 
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Whilst waiting for final layers of surface primer to dry on the plug have been measuring the pulse train for the camshaft. The design honda used on the J35Z2 should be able to get synch in 1 revolution. Now can build the logic table so it can be encoded for the ECU....

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cmp ckp pulse train.jpg


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PostPosted: May 14, 2022, 3:53 am 
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The filleting wax is much easier than the clay. Applied PVA release agent a few days ago, however the original advice I received was correct, it left a horrible surface on the plug so removed it and put a few more coats of wax on instead (9 in total - as shown below). Plug now has gel coat applied, was working against the clock tonight so didn't take a photo of result. Gelcoat did not set early this time, as room temperature was 20C and had plenty of time to spread and smooth out - even using 2% catalyst. Added a couple of polypropylene panels for the flat regions of the taillight recesses to reduce the grip during mold release. Have all of tomorrow set aside to get the glassing underway, this time I have cut the templates before hand so that the draping is correct. The chopped strand mat did not conform well to the tight corners last time so this attempt have precut smaller sections to suit the contours.

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PostPosted: May 15, 2022, 3:47 am 
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Gelcoat 1st layer looked a bit thin in a couple of spots (could see the primer underneath) so added second gelcoat in those spots.
Attachment:
gelcoat 1st layer.jpg


First layer is a fine tissue - with no bubbles this time! Previous failure was mostly due to attempting too much at once - laminated the tissue and CSM at the same time. This time I am building up the first layers individually (i.e slowly and carefully untill I get the hang of this caper).
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Tissue layer complete.jpg


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PostPosted: May 22, 2022, 7:52 pm 
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Hi Marcus,
Meticulous good quality work, as usual.....I have no worries that your diligence will continue through the entire build.

FYI: My last shot at sharing: I noted some time back you rented a paint booth. In painting the TVR, our Pro painted it
in an OLD nasty wooden barn on a ranch. After his spraying and my sanding & polishing the paint is fantastic. My point:
as long as large insects are kept out of the paint, a booth isn't necessary since Primer, top coat-clear coat are all Sanded,
4-5 levels, then polished, 4-5 levels to achieve a mirror finish. I painted the restored 914 and Europa panels in my own
garage with great results.
Cheers,
Terry


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PostPosted: May 24, 2022, 4:22 am 
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A lot of these build threads I generally skim over when I'm catching up, but this thread is always gold. I read every word. Keep up the madness.


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PostPosted: May 24, 2022, 5:16 pm 
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Thanks Terry, your support as always is appreciated. Actually I was very lucky that the paint booth was a freebie, but your points about paint are noted.

A bit of background is appropriate here, Terry was kind enough to donate a porsche steering rack back in Aug 2017 when I was very very early on in my design phase. He has passed on lots of sage advice since then, especially given his experience creating his own mid engine monster V8 914.

Thanks kabuku6, the madness is deeply ingrained - no chance of it relenting anytime soon!

:cheers:


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PostPosted: May 29, 2022, 2:05 am 
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After what has literally been a month of Sundays' the rear mold exists. Unfortunately the plug stuck again very badly on the deep tail light recesses, everywhere else broke free nicely. Leaned on it with the biggest stick I could find and the styrofoam blocks making up the plug sheared away first so it is toast, but you can't make an omlette without breaking a few eggs, appears I am the same with plugs. The air injection worked really well for separating the mold away in the places where it hadn't chemically bonded. Internal surface is really nice so I am equally heartbroken and happy. Definitely going to be getting help during mold break in, do not want to go to level zero.

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