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Learning how to build Lotus Seven replicas...together!
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PostPosted: November 14, 2021, 12:45 am 
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Location: New Zealand
The 200gm plain weave glass cloth conformed to the curvature easily once orientated 45 degrees to the horizontal axis. The plug was quite vulnerable to bumps and knocks with just fairing compound over the polystyrene foam. With the layer of glass and epoxy I can now lean on the plug without denting it with a misplaced elbow. Basically following Mike Arnolds' tutorials - RIP Mike, thanks to his family for sharing these;
https://www.youtube.com/channel/UCVDILm ... nPw/videos

Once the epoxy cures have to remove the amine blush and make the plug dull with sanding;
Attachment:
Amine blush.jpg


One last thin coat of epoxy resin and microballoons to seal all the polystyrene from contact with the polyester body filler and paint;
Attachment:
last coat of epoxy.jpg


Used a super fine finishing filler (Mipa P85), it must be 75% talc because it comes off a little too easily.
Attachment:
final filler layer.jpg


One more big day of work will have it ready for painting, then add flanges for tooling layup. Have bought all new gelcoat and resin, owe thanks to Curtis at NZ Fibreglass for all his advice.


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PostPosted: November 21, 2021, 4:43 am 
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Measured up the vent slots and somehow the accurately cut foam has ended up mispositioned wrt the centerline, will chalk that one up to "learning experiences". To recover the correct dimensions I hacked together a height gauge from threaded rod and a bit of scrap steel. A pair of boxcutter blades held in place with washers and nuts gives an accurate tool for slicing through the glass cloth along the horizontal plane at the correct heights.
Attachment:
slice height.jpg


Easy to slide to block into position and hammer the back of it to make it cut deeply into the plug.
Attachment:
deep cut.jpg


3D Printed some end caps to get the correct slot radius, these corners will be backfilled with epoxy bog to hopefully get an accurate result the second time.
Attachment:
wrong positions.jpg


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PostPosted: November 21, 2021, 10:50 am 
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Location: Oregon City, OR
You're probably already aware some printable plastics distort with the heat generated from epoxies/resins. Being radiused I would expect them to be fairly resistant but the open end might work against you? A cooler bog might help as well.

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Last edited by RTz on November 21, 2021, 11:22 am, edited 1 time in total.

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PostPosted: November 21, 2021, 11:17 am 
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Location: Carlsbad, California, USA
Good, innovative work on that low-cost height gauge. I'll have to steal that one [LOL].

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: November 21, 2021, 1:30 pm 
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Thanks Ron, a good point I will watch out for.

Lonnie, the only issue with it is the time it takes to make large changes in height. I use an air gun on the tangent of the nuts and those little suckers spin up so fast it's entertainment not a chore.


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PostPosted: November 23, 2021, 1:35 am 
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Can recommend using 3D printed PLA forms to mold the epoxy bog against. One coat of Meguiars max mold release wax and they popped right out no issues, and features are within 1 mm of where they should have been - by the time tooling is done no one will ever know I mucked up.....
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position corrected.jpg


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PostPosted: December 2, 2021, 5:53 am 
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The last 20% of progress has taken 80% of the time, so that is a good lesson to take forward. Booked into the spray booth next week for high build primer. Took the plug out into the late evening sunlight, it is a big improvement inspecting under natural light.

Attachment:
almost there.jpg


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PostPosted: December 16, 2021, 3:09 am 
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While we are up will drop the latest progress, lots more sanding to go yet....

Would recommend if you have an alternative site for your build that you post it in your buildlogs so that followers can link to other sites if this one does finally die for good.

My build is mirrored here - https://www.pistonheads.com/gassing/top ... 827105&i=0

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PostPosted: December 16, 2021, 2:52 pm 
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Location: Guadalupe, CA
This is really coming together nicely 8) .. I'm almost due for some fiberglass work.. watching closely :cheers:

--ccrunner

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PostPosted: December 28, 2021, 9:36 pm 
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Hey, Kinetic Research - I've just discovered your thread on here and will be following your project avidly. I am in Auckland too and have been interested in many of the techniques you mention. Are you aware of the Facebook group 3D Print My Ride? They cover DIY scanning and photogrammetry for the purpose of homebuilt car projects. https://www.facebook.com/groups/562692597482059.
cheers
Ross


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PostPosted: December 30, 2021, 5:02 pm 
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Thanks for the heads up Ross, was not aware of them. Cheers.


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PostPosted: January 3, 2022, 6:25 am 
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Happy new year to all reading this build log, expect some major milestones to be knocked over this year but really looking forward to seeing how much actually gets done.

Some carbon fibre cloth appeared under the Christmas tree, going to have to see what that can be used for.

Have finished sanding the high build primer and waxed the plug, last step is shuttering off the vents slots and center gap and tool edge flanges - using corrugated polypropylene sheet and Chavant clay to seal the gaps and easily create draft on the hole sides - leaving the clay block in a closed car during a hot summers day made it very workable material. Plan is to get the tooling underway tomorrow.

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wax and clay.jpg


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PostPosted: March 6, 2022, 3:26 am 
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Finally got my A into G and completed the flanges for the rear mold and applied the tooling gelcoat. Conducted some tests last week on little patches to make sure everything released without damaging the plug and that was fine. 8 coats of release wax and no PVA. Used 1.5% MEKP catalyst for the gel coat as did not want to have any uncured resin, however it went off a little quicker than desired and resulting surface is not as smooth as I had hoped for, but will still get a useable result from it. The flanges are coreflute advertising signage board and the formers will unscrew off the sides after layup. All going well should be done soon...

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Tooling Gelcoat.jpg


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PostPosted: March 6, 2022, 8:43 am 
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Hard to use a mil gauge on curved surfaces. You could use two wires wire one goes through to the buck and the other slides down to just touch then hold them together and check the difference. Not a lot of time to take pics between gel coat and layup with poly. How's the mold look now?

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PostPosted: March 11, 2022, 3:37 pm 
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I was really not happy with the gelcoat application, sanded back all the high points and put the tissue and first layer of chopped stand mat but even with stippling the hell out if I could not eliminate a lot of voids (might not have put enough resin on the mold before applying the CSM), which are critical to avoid in the first few layers for mold longevity, so decided since it was still nice and flexible would be easy to pull off and redo. I was confident given how easy the test patches had popped right off. Wow was I wrong. Not a complete write off but some serious wounds to repair (mentally and physically!). Was advised that the PVA release file was unnecessary if plug was polished well, however next attempt will definitely use it and accept a bit of sanding inside the mold to improve the surface quality.


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