CoolHandMoss
CoolHandMoss New Reader
8/16/21 11:29 a.m.

It sounds like most typically automotive paints will work just fine with the right primer. I am considering awlgrip actually. It is a truly fantastic finish for a boat. Very durable and high quality finish. Easy to spray. But I'm not sure. 

TVR Scott
TVR Scott SuperDork
8/26/21 1:19 p.m.

More progress on the mold and on part-making preparation.

CoolHandMoss said:

Great progress Scott. I hope you are able to pop out an extra for me.

Yes, I can definitely make you a roof panel!  I've got 5-6 others wanting them as well.

I posted this on the TVRCCNA forum, but I'm not sure you're on there:

As far as the actual part goes, there are options.  Simplest / heaviest / cheapest will be solid fiberglass.  Somewhat fancier would be fewer layers of fiberglass with a structural foam core in the middle of the laminate.  High-dollar / lightest / strongest would be carbon fiber layup with structural foam.  I can add in some Kevlar too, which really helps damage tolerance.

I'm going to use epoxy for the resin system, BTW.

No pricing or anything yet, but carbon fiber costs roughly 4X what fiberglass does.

I did a quick 3d model of what I'm looking to make:

And a cross section showing the internal flange on the bottom side:

This can be bonded to the underside for a permanent installation, or could be a temporary panel with gaskets and screws.  Some people are looking to do that too.

Here's what the underside will look like:

As far as the colors go, if someone wanted a cosmetic panel I could use whatever external layers they wanted.  So the carbon/kevlar weave I show on those concepts is totally possible.  A bit of auto clearcoat and it'd be good to go.

TVR Scott
TVR Scott SuperDork
8/29/21 3:10 p.m.

More disassembly and destruction today.  The target: dashboard and wiring.  I finally got the dash pad off th top - it took using the dremel to grind off the old bolt heads.  I'm going to add a lot of nut-plates and captive fasteners to make assembly and removal easier on all these parts.  What a chore.  And what a mess:

I did finally get the dash panel out too.

I didn't really pay much attention to where all the wires were going.  It's a total mess and I will reuse exactly zero of what's there.

I think maybe the car quit running because of electrical troubles.  Just guessing...

So much nasty hackery behind the dash.  Bleech.

On the roof panel front, I got in a box of 0.040" thick tooling wax.  This will let me build up the flange around the roof panel and give that nice flush mounting.

It's got pressure sensitive adhesive on one side so I can layer it up to the 0.160" that I need to match the roof.

That's it for now.

TVR Scott
TVR Scott SuperDork
9/2/21 2:02 p.m.

More roof mold work today.  First I wanted to cover up the sharp edges on the mold so that I won't worry about popping my vacuum bag:

I had this rubber house-wrap stuff sitting around, so I used it.  Worked out pretty well.

My plan is to use an envelope vacuum-bag - basically I'll put the whole tool in the bag and pull vacuum over the whole mess.  This should be reusable and less temperamental with small vacuum leaks.

Next up I built up the "joggle" that will form the inside flange.  This is where the tooling-wax comes in.  Four layers built up to 0.16" thick:

I added some little corner fillets - you can just barely see them in the corners.  Just used a punch and a razor knife to make them:

Time to go change the oil in my vacuum pump - it's been forever since I've done a composites layup like this.

Shavarsh
Shavarsh Reader
9/2/21 2:27 p.m.

The tooling wax is a great idea, I'll have to file that away for future use. Looks great!

 

Are you worried about creasing in the corners?

TVR Scott
TVR Scott SuperDork
9/2/21 2:32 p.m.
Shavarsh said:

The tooling wax is a great idea, I'll have to file that away for future use. Looks great!

 

Are you worried about creasing in the corners?

When I was doing aircraft composites we used tooling wax for exactly this purpose.  Works out really well and it's not very expensive.  Easy to work with.

What do you mean creasing in the corners?  Creasing of the laminate or the vacuum bag?

I added the radii to smooth out that transition onto the joggle and reduce any stresses at the corners.

Shavarsh
Shavarsh Reader
9/2/21 3:04 p.m.

I mean creasing of the laminate as it tries to pull into the corner where you added the radius. My only background is in open layups (no vacuum bag) and have had trouble getting compound curves to conform nicely. I'll be watching and learning.

TVR Scott
TVR Scott SuperDork
9/2/21 4:14 p.m.

In reply to Shavarsh :

That is a concern - more with the laminate bridging the corner.  You'll get a gap there that isn't the right shape.

There are ways around this - I'll post more pics tomorrow.

TVR Scott
TVR Scott SuperDork
9/2/21 6:26 p.m.

Ah screw it - I'm in the mood for more photo-dump.  I got lots done today, so that makes me happy.

Vacuum bag construction.  This bagging-film is of the "stretchy" variety.  It's really nice for getting into tight corners and such, and it's quite tear resistant, but it can be a bit of a pain work with.  This particular stuff is 55" wide V-fold, which means it's really a huge 110" sheet with fold on one side.

Since I want an envelope bag, I need to seal up the two long ends.  This leaves me with the factory fold on one side, and the open end for access.  Here's the bag with the first long-end sealed:

The tape I'm using is literally called "Tacky tape".  It's sort of a pain and sort of wonderful.

For sealing up corners you can roll the tape into a thick ball.  Reminds me of a fiddle-head plant:

Then you cram that ball into the corner of your vacuum bag fold.  You can make pleats using this method too, but I'm not doing any on this bag.  (Topic for another day).  Here's the corner all sealed up:

I had to work the tape into the bag to get all the wrinkles and little voids out.  Those will leak if I leave them.

All sealed up with clip-and-rod sealing thingy.  I bought that a long time ago - no idea where...

You can see the vacuum port taped onto a tail of breather cloth.  This will transmit the vacuum to the pump while also preventing it from pulling resin.

This thing SUCKS!

My old A/C pump pulled the bag down beautifully.  Decent seal on the bag - wouldn't pass an aerospace vacuum test, but I'm not concerned.

Here's  a quick pic of some pleats that I set up in the bag:

The idea is to form a big wrinkle in the bag over a low spot or a corner.  That added material can then get pulled down into the corner and really press the laminate in tight.  Works great.

Tomorrow I'll cut some plies and prep some of the other materials.  Maybe I'll do a first test part if I have time.

2Girlsracing (Steffi)
2Girlsracing (Steffi) Reader
9/3/21 5:26 a.m.
CoolHandMoss said:

It sounds like most typically automotive paints will work just fine with the right primer. I am considering awlgrip actually. It is a truly fantastic finish for a boat. Very durable and high quality finish. Easy to spray. But I'm not sure. 

There was a show car here some years back called awlgrip, I saw it in person a couple times and it was an awesome finish on it. 

2Girlsracing (Steffi)
2Girlsracing (Steffi) Reader
9/3/21 5:31 a.m.

Does an ac pump work out cheaper than a carbon fibre type pump or is it just a had it lying around thing? Other half is talking about some projects and i may need one.

TVR Scott
TVR Scott SuperDork
9/3/21 6:50 a.m.

The a/c pump works just fine.  This one was actually "broken" and thrown out by my former employer.  They were really good at being wasteful.  I took it apart, cleaned the sludge out of it, and it now works fine.

I've used an eductor-style vac pump and those work too but they're super loud and run the compressor like a rented mule.

The fancy composite-specific vac pumps are overkill for any kind of home use.  I think the main benefits are they're oil-less and quiet.  Great if you're running them 24/7 building aerospace parts, but not really necessary for this kind of stuff.

frenchyd
frenchyd UltimaDork
9/3/21 3:28 p.m.
TVR Scott said:

More progress on the mold and on part-making preparation.

CoolHandMoss said:

Great progress Scott. I hope you are able to pop out an extra for me.

Yes, I can definitely make you a roof panel!  I've got 5-6 others wanting them as well.

I posted this on the TVRCCNA forum, but I'm not sure you're on there:

As far as the actual part goes, there are options.  Simplest / heaviest / cheapest will be solid fiberglass.  Somewhat fancier would be fewer layers of fiberglass with a structural foam core in the middle of the laminate.  High-dollar / lightest / strongest would be carbon fiber layup with structural foam.  I can add in some Kevlar too, which really helps damage tolerance.

I'm going to use epoxy for the resin system, BTW.

No pricing or anything yet, but carbon fiber costs roughly 4X what fiberglass does.

I did a quick 3d model of what I'm looking to make:

And a cross section showing the internal flange on the bottom side:

This can be bonded to the underside for a permanent installation, or could be a temporary panel with gaskets and screws.  Some people are looking to do that too.

Here's what the underside will look like:

As far as the colors go, if someone wanted a cosmetic panel I could use whatever external layers they wanted.  So the carbon/kevlar weave I show on those concepts is totally possible.  A bit of auto clearcoat and it'd be good to go.

I buy prepeg carbon fiber that has expired or about to expire and often get it at fiberglass cloth prices. It's fine if it's body pieces and not structural.  Then use regular resin and a squeegee to remove excess.  That approach weighs a few ounces more than the vacuum bag and autoclave approach  but gives plenty of strength. 
   My XKE I used carbon fiber,  foam core,  and Kevlar and got the front bonnet down to 34 pounds. From the close to 300 pounds stock steel*
    The great thing is I had it laying on the floor, tripped over a Jack handle and landed on the center of the hood.  It flexed and then popped my fat body back up like a trampoline. Some scratches on the bottom edge, but that's it.  
* to be fair this was a race car hood without the bumpers, headlite buckets, or inner panels.  

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) MegaDork
9/3/21 3:32 p.m.

In reply to frenchyd :

where do you buy it?  and do you just ask them if they have any stock that is aging out?

TVR Scott
TVR Scott SuperDork
9/3/21 3:47 p.m.

In reply to frenchyd :

Thanks for weighing in.  Yeah, the strength and lightness of a good composite part is just fantastic.

I've worked with prepreg carbon and glass a lot in the past.  That would require an oven cure at roughly 350 F, and I'm just not set up for that. 

Quick edit for AC - You can get expired prepreg from aircraft companies or similar.  The one I worked for occasionally had a roll or two of expired, and would often give it away to a Formula SAE team.  Since the resin is already infused and is partially cured into a "b-stage" it doesn't last forever.  You even ship it with dry ice and store it in a freezer.  It's got an expiration date for in the freezer, and then a much shorter shelf-life once it's been thawed out.  So a good shop will plan when to pull out the material according to their work flow.

Two-part epoxy and a wet-layup will get the job done on this one.  The vacuum bag will ensure the laminate is nice and compact, and that my resin ratios are close.

I've got several other M owners interested in roof panels too.  Some will probably just be thick solid fiberglass, others might want foam core too.  Mine will be carbon and kevlar with a foam core.  Light weight and damage tolerance are high on my list!

 

TVR Scott
TVR Scott SuperDork
9/5/21 4:20 p.m.

Test panel day!

Again my younger one helped out.  Really nice, since this kind of thing is so much easier with another set of hands.

Not a bunch of pictures here since things tend to happen fast and sticky!

I prepped two plies of fiberglass, cut release-film and breather cloth, and prepped the mold with wax and then PVA spray.

We mixed up 5 "pumps" of epoxy (about 4 oz) and worked in the first ply.  It actually wetted out a little better than I expected, so we only added 4 pumps for the second ply.  Got the second one down and all smoothed out, and then put down the release film:

This is the perforated stuff, so when I pull vacuum the excess resin will get squeezed out the of the part.

Breather cloth added and placed in the envelope bag:

And vacuum pulled!

Yes, I'm using my car as a work bench.  Sue me, it's a small garage.

You can see the excess resin bleeding thru the release film.  You can also sort of see the pleats in the vacuum bag, but they're not very defined here.  I'm going to run the vacuum pump until this evening, and by then the part should be set enough to not need it.

Then we'll pop it out tomorrow.

Gammaboy
Gammaboy New Reader
9/6/21 7:05 a.m.

Quick question, by AC pump do you mean a vac pump for vacuuming down AC systems before filling, or the compressor out of an AC system?

I salvaged the compressor out of an AC system that had a controller failure specifically for future composites work (I also scored a direct drive air compressor that the pressure switch casting was broken on, was going to salvage the pump and replace the air inlet with a hose barb for jobs that needed more capacity than the ac compressor could provide). 

TVR Scott
TVR Scott SuperDork
9/6/21 11:19 a.m.

In reply to Gammaboy :

Yeah, it's a rotary-vane pump used to evacuate an air-conditioning system.  This one is from Grainger, but Harbor Fright has similar for much cheaper.

You could potentially use a vehicle A/C pump.  I've heard of people turning those into compressor, but they might work as vacuum pumps too.  Try it - I expect a full report!

TVR Scott
TVR Scott SuperDork
9/6/21 3:43 p.m.

Just popped out the part.  Released from the tool with zero issues.  The only bummer was that the epoxy stuck to the vacuum bag.  I've never had that happen, and unfortunately we tore holes.  So I'll need to make a new one.  Next time I'll add a layer of polyethylene sheet on top of the breather film.  That should be a fine barrier.

The part:

Two plies of fiberglass is super floppy!

But it fits, and my assistant is happy:

Terrible pics - sorry about that.

I haven't cleaned up the bondo off the underside of the roof yet, but the contour looks good and the spacing on the flange looks good.  Overall it's coming together.

CoolHandMoss
CoolHandMoss New Reader
9/6/21 8:39 p.m.

Looks great! So once it's mounted by the lip around the edge you just fill the gap with Bondo/awlfare or whatever and ready for primer? 

TVR Scott
TVR Scott SuperDork
9/6/21 9:01 p.m.
CoolHandMoss said:

Looks great! So once it's mounted by the lip around the edge you just fill the gap with Bondo/awlfare or whatever and ready for primer? 

Yup that's exactly what I have in mind.  My goal was that it should go in with just a little filler.

Gammaboy
Gammaboy New Reader
9/7/21 2:36 a.m.

In reply to TVR Scott :

Sorry, I meant the AC compressor out of a house split system, not a automotive unit. It's on the list of things to do once I'm back home in Oz...

One of those little rotary vane pumps was the plan C if Plan A (AC comp) and plan B (direct drive compressor conversion) turned out not so great.

TVR Scott
TVR Scott SuperDork
9/7/21 9:40 a.m.

In reply to Gammaboy :

Oh, gotcha.  I actually don't know much about household air conditioners.  You're on your own on that one.

Shavarsh
Shavarsh Reader
9/7/21 10:30 a.m.

The part came out great! thanks for sharing the process

TVR Scott
TVR Scott SuperDork
9/14/21 8:48 a.m.

Boring update:

A stock TVR fabric sunroof assembly weighs:

I also got my structural foam ordered yesterday.

I'm going to measure my carbon fiber stock today and get more fabric on order.

That's it for now.

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