So, the Marbocoat mould-sealer claims to leave the mould more shiny than if it was just ordinarily treated. Well, if you look at the pictures above, you can see that it actually does. Five coats of sealer and five coats of release agent and you can see the result.
I masked off the mould for about one inch (I know, thinking in old money – don’t care) around the perimeter so there wouldn’t be any issues with the tack-tape struggling for adhesion. As a comparison, masking tape applied to the treated surface just curls off.
The mould is treated, the templates are made. The modifications to an old compressor to make a vacuum chamber are nearly done (subject of another post soon), and the spray-booth is complete. The next post illustrates just how Dexter I’ve gone.
So, I think my tub is going to be an interesting thing to demould – basically more than 4m2 of cloth and it’s nearly all sloped edges. I’ve heard of people using air to demould and I have an air wedge, but that only gets in from the top. I’ve even optimistically bought a couple. The other way to do this is to build a function into the mould or part to inject air.
So, the way is to somehow get a thread into the part for an air-line connector to make a seal good enough to take some pressure. One needs something that gets through to the mould/part interface, without anything so ungainly as drilling and tapping a thread for said airline connector.
Ideally, one builds it in to the part.
The technique is to stick the face of a nut to the mould, and then build the layers of cloth around it. In order to stop the resin infiltrating the nut, one should take a bolt, coat the threads in wax and put that in the nut. If you just put the bolt in, there’s a strong chance infusion resin will get down the threadsl. Then, when you demould, you turn the bolt, crack the thread and you have a way to get the air in.
In order to get the air in, you need to take something that matches the thread, drill it out and then weld it to a air-line fitting. So, you can connect it to your airline and force air in. The other thing you can do, rather than do this, is just turn a bolt in to apply physical force to push the part off the mould.
OR, you can make one feature do two parts.
So, my plan is to weld the nut to a plate, cross drill the plate with a bunch of holes, and embedd the plate in the stack – like a hard-point. I will replace the core with the actual plate, so I am putting in a 5mm thick plate (ouch for weight).
I will then use this as a harness anchor point. So, rather than adding a couple or air-release points that are convenient for the mould, I’ll be adding four either side. Two below for the crotch straps, and one either side of the thighs for the leg straps. needless to say I need to be quite accurate for my positioning, and I’ll probably have to use 7/16 UNF rather than M10 to stay with the standard larger size anchor points (rather than have to do lots of explaining to scrutinisers that may not understand what I’ve done). The other smart bit of advice Vic gave me was to double up the cloth over the anchor point, which makes a lot of sense.
Conclusion: reuse is best. Anchor points can become release points. Viva El Presedente.
Here we have a view of half the tub mould. It’s been flatted, sanded and polished. It’s not a fantastic mirror shine, but it really is quite shiny. in the left hand picture you can see some black gel-coat where I’ve had to make a repair or two. You can also see some white where I’ve flatted back to the undercoat. Not a problem here.
I’ve learned loads from this half, and now when I get time I’ll do the other half. Ideally finished this week. I think there were 5 hours of work in each half to get to this finish. Flatting was done with a P800 paper attached to a dual action orbital sander. Once flatted (and I’ve got other pictures showing how it looks so you can see if you’re finished the flatting process) I then ran over it with a P1200 to start the polishing. Then with a industrial polishing thing, a P1500 cutting polish, P2000 cutting polish, and then high-gloss and swirl removing polish.
Next steps are to apply mould cleaner and mould sealer. Then 5 coats of release compound. Then … I can actually lay up and pull a part.
I love it when you ring someone for a bit of advice and you get an answer you totally didn’t expect.
I’ve finished the engine build, and am about to sort the chassis mould, which means I’m not far from a rolling chassis. I’m gathering together some of the engine components I need and wanted to be sure I had the right advice on intake trumpet lengths I called Damien at Day Tuner – it makes sense to try and get this right before getting to the rollers.
Then Damien came up with the best idea: to quote “with your facilities, don’t try and guess the trumpet lengths, or go from rule-of-thumb. Print out lots of trumpets and we can chop and change over the day”. Bearing in mind pressure waves under the bonnet, you may actually want a selection of different lengths.
To the 3D PRINTER MINES !!!
So, the engine has gone off to Damien at Day tuner to have the cam timing set up. I tried to do it, and I had sane instructions, but I failed more than Trump in Mexico. Every time I tried to get the value just so, the springs would shove and the cam would spang round, taunting me. I followed Homer Simpson’s rule: “If at first you don’t succeed, give up”. I rang Damien to get it done (which is what most Duratec owners do around here) and he laughed … “With your setup, those springs will close a barn door in a force 10 gale – come on over”. This is definitely a job for the expert.
Once done, I can seal up the engine (as in seal down the top, front and sump), and put the injector blanking plugs in, then it’s finished.
In the picture below, you can see some of the blanking plates I printed up – this is exhaust side. Pretty groovy I think. I also got more familiar with Onshape and the more I use it, the more impressed I am. If you’re a hobbyist like me, it’s free as long as you store your parts in their cloud and make them visible to all. For $100 per month, you can keep more than your allocated 10 private parts in the cloud. That sounds draughty to me. Onshape really is VERY GOOD. I use it on my iPad Pro and it’s a perfect fit with the pencil. It’s interesting to watch your drawings on the IPad being updated realtime if you’re also accessing them from a Mac or PC.
The engine spec should get me 230 BHP, 100 up from the stock spec, and it’s strong enough to take a super-charger, which will give me 100BHP more, should I decide that’s the route to go. I’ll done that once I’ve got to know the car all over again.
Right – some tidying up do do.
I now own a dial gauge. I can measure things. I even now have a drawer in my tool cabinet with “measuring things” on the label.